HAYASHI, Yasuhiro

ISSN：03854213

Outline：© 2016 The Institute of Electrical Engineers of Japan. Recently home energy management system (HEMS) has been spread due to increase in awareness of save energy after Great East Japan Earthquake. HEMS consists of photovoltaic power system (PV), battery energy storage system (BESS) and heat pump water heater (HPWH), etc. Residential PV implementation rate has been increasing due to feed in tariff from 2009. So there is a danger of output suppression loss due to voltage increase on a distribution line due to reverse power flow from each residential PV. So we try to study how to reduce output suppression loss using BESS and HPWH optimally. One of the main purpose to implement BESS and HPWH is for economy using the difference in electricity charges between during nighttime and daytime. So in this research, we optimize how to operate BESS and HPWH to improve the benefit of the electric power selling charges and electricity charges considering reduction of output suppression loss and the difference in electricity charges between during nighttime and daytime.

Outline：The subject of this study is to propose a power interchange system in a collective housing with residential solid oxide fuel cells (SOFCs) and a robust operation planning method for integrated SOFCs against uncertain energy demand forecast. In this method, the future operation plan for multiple SOFCs is optimized and determined to minimize the expected total primary energy consumption in the collective housing considering uncertainty in demand forecast. If the forecast energy demand includes forecast errors, the result of SOFCs operation will corrupt from the viewpoint of the primary energy consumption. Thus, the output decision problem for SOFCs is formulated by considering the corruption caused by forecast errors, so that the decided SOFC outputs have the robustness against uncertainty in demand forecast. The validity of the proposed method is examined based on numerical simulations from the perspective of the robustness.

ISSN：04247760

Outline：© 2016 Wiley Periodicals, Inc. Photovoltaic (PV) systems have recently attracted considerable attention in the context of environmental problems, antinuclear power movements, and energy problems. Therefore, the large-scale introduction of PV systems is expected in the near future. But the connection of many PV systems to the power system leads to problems. For example, the system voltage often drifts from the norm when reverse power flows increase. Accordingly, optimal system operation is required in order to make maximum use of solar energy to the maximum by installing energy buffers such as storage batteries. In particular, in forecast information, knowledge of the reliability as well as the predicted solar irradiance is essential for effective operation. In this paper, we propose a way of estimating the prediction interval of solar irradiance as an index of reliability by using just-in-time modeling. We consider the accuracy of the prediction interval under many conditions and derive a high-precision estimation method. In addition, we also discuss about the future subjects of study.

Outline：Voltage deviation in distribution networks and photovoltaic (PV) output restriction, caused by a large amount of PV systems installation, have been issued recently. BESS (Battery Energy Storage System) is one of the solutions. However, the detailed evaluation of the voltage control effect of BESS has not been carried out, because its effect varies according to BESS placement, its output and configuration of distribution, etc. Therefore, the amount of PV introduction limits in several distribution networks were evaluated and effective BESS arrangement and output control were examined in this paper. The effectiveness of the proposed BESS cooperating voltage control method with LRT, SVR was verified using numerical simulation and experiment of distribution system simulator.

Publish Classification：Research paper (scientific journal) ISSN：1348-8147

Outline：Recently home energy management system (HEMS) has been spread due to increase in awareness of save energy after Great East Japan Earthquake. HEMS consists of photovoltaic power system (PV), battery energy storage system (BESS) and heat pump water heater (HPWH), etc. Residential PV implementation rate has been increasing due to feed in tariff from 2009. So there is a danger of output suppression loss due to voltage increase on a distribution line due to reverse power flow from each residential PV. So we try to study how to reduce output suppression loss using BESS and HPWH optimally. One of the main purpose to implement BESS and HPWH is for economy using the difference in electricity charges between during nighttime and daytime. So in this research, we optimize how to operate BESS and HPWH to improve the benefit of the electric power selling charges and electricity charges considering reduction of output suppression loss and the difference in electricity charges between during nighttime and daytime.

ISSN：21574839

Outline：© 2015 IEEE. This paper studied power and hour capacity requirement for energy storage by two approaches. First one is evaluations without constrained condition of power and hour capacity with 80 sets of maximum ramp rates and time windows. And second one is evaluations with constrained condition of power and hour capacity for 2 grid codes (less than 0.1pu change of wind farm (WF) capacity in 20min time window, showing 0.1pu/20min in this paper, and 0.3pu/360min) to see details. The first evaluation in case of 3a resulted 1.0 pu power capacity (charge plus discharge capacity for all result) and 1.3 to 2.2 pu-h hour capacity are required to satisfy maximum ramp rate in time window of 0.1pu/20min. And 1.2 to 1.3 pu and 13 to 18 pu-h are required for 0.3pu/360min. And from the second evaluation in case of 3a, 0.7 to 0.8 pu power capacity and 1 to 2 pu-h for 0.1pu/20min and 1.0 pu and 10 to 15 pu-h are required for 0.3pu/360min. This paper provides relationship between maximum ramp rate in time windows and power and hour capacity requirement. The results help to answer questions whether power and hour capacity requirement satisfy grid codes with simple operating method of an energy storage system.

ISSN：21574839

Outline：© 2015 IEEE. In this study, as a new index of facilities, business continuity capability on occasion of an energetically isolated operation, was defined and evaluated for the facility with a rich amount of resources such as private generators, a battery energy storage system and a PV generation system. A methodology was proposed to evaluate a duration during which the facility is self- sustaining regarding energy use. An effect of reducing the capacity of PV or battery was also examined.

ISSN：03854213

Outline：© 2016 The Institute of Electrical Engineers of Japan. Demand response can achieve peak-cut and peak-shift of the electric demand by delivering the load restraint of customers, based on Demand Response (DR) signal sent by an electric power company. However, the demand response restrains the load amount of many consumers simultaneously, so the voltage of the whole distribution system is greatly fluctuated depending on the distribution form such as line length, amount of load restraint, etc. Therefore, we propose the voltage control methods which can avoid voltage deviation in consideration of a time constant of demand response. Furthermore, we propose the BESS cooperating voltage control methods with LRT, SVR and verify the effectiveness using experiment of distribution system simulator.

ISSN：0385-4213

Outline：Voltage deviation in distribution networks and photovoltaic (PV) output restriction, caused by a large amount of PV systems installation, have been issued recently. BESS (Battery Energy Storage System) is one of the solutions. However, the detailed evaluation of the voltage control effect of BESS has not been carried out, because its effect varies according to BESS placement, its output and configuration of distribution, etc. Therefore, the amount of PV introduction limits in several distribution networks were evaluated and effective BESS arrangement and output control were examined in this paper. The effectiveness of the proposed BESS cooperating voltage control method with LRT, SVR was verified using numerical simulation and experiment of distribution system simulator.

ISSN：0385-4213

Outline：Recently home energy management system (HEMS) has been spread due to increase in awareness of save energy after Great East Japan Earthquake. HEMS consists of photovoltaic power system (PV), battery energy storage system (BESS) and heat pump water heater (HPWH), etc. Residential PV implementation rate has been increasing due to feed in tariff from 2009. So there is a danger of output suppression loss due to voltage increase on a distribution line due to reverse power flow from each residential PV. So we try to study how to reduce output suppression loss using BESS and HPWH optimally. One of the main purpose to implement BESS and HPWH is for economy using the difference in electricity charges between during nighttime and daytime. So in this research, we optimize how to operate BESS and HPWH to improve the benefit of the electric power selling charges and electricity charges considering reduction of output suppression loss and the difference in electricity charges between during nighttime and daytime.

ISSN：0385-4213

Outline：Demand response can achieve peak-cut and peak-shift of the electric demand by delivering the load restraint of customers, based on Demand Response (DR) signal sent by an electric power company. However, the demand response restrains the load amount of many consumers simultaneously, so the voltage of the whole distribution system is greatly fluctuated depending on the distribution form such as line length, amount of load restraint, etc. Therefore, we propose the voltage control methods which can avoid voltage deviation in consideration of a time constant of demand response. Furthermore, we propose the BESS cooperating voltage control methods with LRT, SVR and verify the effectiveness using experiment of distribution system simulator.

Outline：© 2015 IEEE. Output of the photovoltaic (PV) system drastically fluctuates depending on weather conditions. Therefore users of PV systems should manage their energy usage with forecast information of the PV output. Due to the reasons above, we have developed an estimation method of X% prediction interval of solar irradiance. We have achieved a high-accuracy prediction interval for any prediction coefficient X%. However, we found that there are some errors in a case where the prediction coefficient is high. In this paper, we improve the estimation algorithm of the prediction interval.

Outline：© 2015 IEEE. This paper investigates the operation of various possible standalone power supply configurations for smart houses with a view to preventing inconvenience to residents when blackouts occur. In smart houses, various types of power-generation equipment (such as photovoltaic (PV), battery energy storage system (BESS), electric vehicle (EV), and fuel cell (FC) systems) with different output power, capacity, and response time characteristics are used. Our results indicate that combined use of these equipment and home energy management system (HEMS) control provide the best means of enabling residents to effectively use household appliances even in limited power supply situations.

ISSN：0385-4213

Outline：This paper proposes a dynamic updating method of the optimal control parameters of multiple advanced step voltage regulators (SVRs) in a single feeder considering a massive introduction of photovoltaic (PV) systems. Each advanced SVR can adjust their tap position according to the updated control parameters in a certain period. The main feature of the proposed method is that the optimal parameters which minimize the voltage violation amount from the proper range and the tap operation count of SVR are determined quickly based on greedy algorithm. A numerical simulation is carried out on an actual distribution system model with the measured PV and load data so that the effectiveness of the proposed method can be evaluated.

ISSN：18839363

Outline：© 2015 IEEE. This paper presents a new method for determining the load drop compensator (LDC) parameters of On-load tap changer (OLTC) and step voltage regulators (SVRs) in the distribution system. Introduction of photovoltaic generation systems (PVs) into a distribution system makes determining the appropriate LDC parameters difficult, which may cause voltage deviation because reverse power flow from PVs affects voltage. Especially in the distribution system in which multiple SVRs are installed, determining the appropriate combination of LDC parameters becomes difficult. In the proposed method, the parameters are reset every hour by choosing one LDC parameter from a database including feasible parameters in the past. To create the database, the proposed method hourly enumerates the feasible parameters utilizing data acquired by SCADA. To evaluate the performance of the proposed method, the amount of voltage deviation of the proposed method will be compared with that of a centralized control method.

Outline：© 2015 IEEE. This paper presents a distribution automation system (DAS) for service restoration in the distribution network with photovoltaic (PV) generator systems, which are disconnected simultaneously after a fault and subsequently reconnected after service restoration. Because the reverse power flow of PVs affects voltage in the distribution system, voltage dips and surges occur during the service restoration. However, current DAS do not control voltage regulators such as an on-load tap changer (OLTC) and step voltage regulators (SVRs) during the service restoration. The proposed DAS estimates the voltage in a distribution network considering the simultaneous disconnection of PVs by performing power flow calculations, and it controls the tap position of OLTC and/or SVRs according to the predicted voltage deviation. The voltage after the disconnection of PVs is calculated by estimating the PV output utilizing square kilometer solar radiation data calculated using satellite image data in real time.

Outline：© 2015 IEEE. Widespread interconnection of Photovoltaic (PV) systems in the distribution system may create voltage rise problem. In this paper, a decentralized voltage control method by use of voltage regulators (VRs) and demand side management using consumer controllable load has been proposed for voltage rise compensation. The proposed method includes a novel determination method to find dynamic line drop compensation (LDC) parameters for a VR that has reverse power flow using the measured line current through VR and an optimal method that determines a dead band for a VR in order to lessens the number of tap operations while minimizing voltage deviation and violation. The obtained results show that voltage violation is extensively mitigated by the proposed method and no significant increment in tap operations of VR is encountered.

ISSN：0385-4213

Outline：Compensating the voltage within the appropriate range becomes difficult when a large number of photovoltaic (PV) systems are installed. As a solution to this problem, the installation of a low-voltage regulator (LVR) has been studied. In this paper, we propose a method for rapidly and accurately determining the line drop compensator method (LDC) parameters as a part of a voltage management scheme, which consists of prediction, operation, and control. In the proposed method, candidates of the appropriate LDC parameters are selected with low computational cost by using classifiers that learns the relation between power series data and the properness of LDC parameters. We performed numerical simulations to evaluate the validity from the viewpoints of computational time and classification accuracy for determination of the LDC parameters, and verified the voltage control performance of the proposed method.

ISSN：0385-4213

Outline：There is a danger of output suppression of high-penetration residential PV systems due to voltage increase. It is necessary to install new technology to prevent the occurrence of such phenomenon. Therefore, we focused our attention on heat pump water heaters (HPWHs). HPWHs are usually used to heat water during night time because electricity prices are cheaper than during the daytime for the load leveling in Japan. So they can be used as a countermeasure without additional cost if they are operated during the daytime. However, HPWHs do not have sufficient capacity to absorb inverse energy at each residence. Thus HPWH operation must be optimized to minimize output suppression loss. In this research, we selected four typical sunny days in spring, summer, autumn and winter. The optimal HPWH operation was calculated by numerical simulation. The optimal monthly HPWH operation was investigated using the weather forecast assuming actual operation in each season.

ISSN：0385-4213

Outline：PV system recently attracts much attention on the back of environmental problems, antinuclear power movements and energy problems. Therefore, a large scale introduction of PV system is expected in the near future. On the other hand, a lot of PV systems connected to the power system bring on some problems. For example, a system voltage often drifts from the norm when the reverse power flow increase. Accordingly, it is necessary to perform an optimal system operation in order to utilize a solar energy to the maximum by installing energy buffers, e. g. storage batteries. Especially, the forecast information i.e., the reliability as well as predicted solar irradiance is essential for the effective operation. In this paper, we propose a way to estimate the prediction interval of the solar irradiance as an index of reliability by using Just-In-Time Modeling (JIT Modeling). We consider the accuracy of the prediction interval under many conditions and derive the high-precision estimation method. In addition, we also talk about the future outlook of this study.

ISSN：0385-4213

Outline：In this paper, the authors propose an electric power interchange system in collective housing with fuel cells (FCs) and a determination method of operation plan for FCs in the collective housing. In the method, the operation plan for FCs is determined from an evaluation point, primary energy consumption of all houses in the collective housing, based on an enumeration method and particle swarm optimization (PSO) which is one of non-liner optimization methods. In order to examine the validity of the determination method, numerical simulations are carried out for the collective housing model, primary energy consumptions of the model are compared to those of a standard system (without FCs), and the reduction effects are evaluated taking uncertainty into consideration by using 10,000 demand patterns which are represented by 40 observational demand data based on the bootstrap method. In addition, the reduction effects by reducing introduced FCs by half are also evaluated from the point of primary energy consumptions, operating efficiency and running efficiency.

ISSN：03854213

Outline：A fault locator system in a loop-shaped distribution system with inverter based distributed generations is proposed. An algorithm of proposed fault locator system is based on the impedance obtained by the phase-voltage and line-current at the transformer feeder in the power distribution substation. We have proposed the quadratic equation expressed in terms of fault location. The quadratic equation represents the impedance from the substation to the fault location. Inserting the impedance obtained by the voltage and current at the transformer feeder into the quadratic equation, two candidates of the fault location are obtained. We can select the true fault location from the two candidates by using the characteristics of impedance calculated by the voltage and current at the incoming feeder of distributed generation. The validity of the fault locator system was investigated by PSCAD/EMTDC simulations. As a result, it was found that impedance obtained by the information of the substation and distributed generations are useful for searching the fault location in the loop-shaped distribution system.

ISSN：03854213

Outline：Measured data from IT switches are utilized in order to control voltage in distribution systems with photovoltaic generation systems. However, length of period from the data measurement to the data acquisition from IT switches affects voltage control ability in the distribution automation system. In this paper, a voltage control method by LRT and SVR with the periodic data from IT switches is proposed, and using the method, the effect of the length of the data acquisition period for voltage control is evaluated through numerical simulations in a distribution system model. Furthermore, the optimal length of the data acquisition period is determined according to PV penetration rate.

ISSN：03854213

Outline：Voltages in distribution system are maintained within a proper voltage range by adjusting a tap position of Load Ratio control Transformer (LRT) and Step Voltage Regulator (SVR). In Japan, many voltage control methods have been researched. However, these conventional methods do not presuppose the bank fault restoration. Since the main purpose of voltage control of the conventional restoration approach is to reduce the amount of voltage violation in distribution system, the number of customers with voltage violation cannot be reduced to zero during a bank fault restoration. In this paper, the authors propose a cooperation voltage control method of LRT and SVR to minimize the number of customers with voltage violation corresponding to the bank fault restoration in distribution systems with PV systems. In the proposed method, the tap position of SVR is controlled after the control of LRT to avoid frequent tap changes and each tap position of voltage control devices is controlled to minimize the number of customers with voltage violation. In order to check the effectiveness of the proposed method, the simulation using distribution system model with PV systems is performed under various conditions.

ISSN：03854213

Outline：Since residential photovoltaic systems trend to increase in low-voltage distribution feeders, it is becoming more important to estimate voltage profile including not only high and middle but low-voltage distribution network to operate distribution systems. In case of using the conventional power flow calculation method based on iterative calculation, it will be taken much time to get voltage values all over low-voltage distribution feeders. This paper presents a new method to calculate voltage quickly keeping the accuracy sufficient for practical operation. In order to check the validity of the proposed method, numerical results are shown by comparing its computation accuracy and time with those of the conventional one.

ISSN：03854213

Outline：Distribution system has huge number of configuration candidates because the network configuration is determined by state of many sectionalizing switches (SW: opened or closed) installed in terms of keeping power quality, reliability and so on. Transmission system also has huge number of configuration candidates and circuit breakers (CB: opened or closed) as same objective as distribution system. Since feeder current and voltage depend on the network configuration, losses of transmission and distribution systems can be reduced by controlling states of CB and SW. So far, various methods to determine the loss minimum configuration of transmission and distribution systems have been researched. However, a method that hierarchically determines the loss minimum configuration of transmission and distribution system with PV has not been proposed. In addition, power flow of whole system is changed by various PV penetration distribution patterns. Therefore, transmission and distribution losses must be evaluated in various PV penetration cases.In this paper, a hierarchy control method to determine a transmission and distribution loss minimum network configuration by controlling on-off states of CB and SW is proposed. The validity of the proposed method is evaluated to calculate the reduction of whole network loss in a transmission and distribution model with 48 CB and 1404 SW in two kinds of PV penetration cases.

ISSN：03854213

Outline：This paper describes dynamic voltage control method using SVC with controllable dead band that changes dynamically to a node voltage in a distribution system installed SVC. Proposed method consists of three systems. First system detects probability of voltage deviation from proper range of node voltage. Second system is used to stabilize output of SVC based on changing dead band. Third system expect voltage trend. In order to verify the validity of the proposed method in comparison with conventional methods, numerical simulation and experiment were carried out using a distribution system model with RES.

ISSN：03854213

Outline：Recently, the number of system interconnection of the renewable energy sources (RES) such as the photovoltaic generation (PV) and wind power generation is increasing drastically, and there is in danger of changing the voltages in a distribution system by the precipitous output variation of RESs. In this study, the authors propose one voltage control method of the distribution system by the power factor control of plural PV systems in consideration of cooperation with the load ratio control transformer (LRT) of laggard control response installed beforehand in the distribution system. In the proposed method, the slow voltage variation is controlled by LRT, and the steep voltage variation uncontrollable by LRT is controlled by plural PV systems, as a result, all the node voltages are controllable within the proper limits. In order to verify the validity of the proposed method, the numerical calculations are carried out by using an analytical model of distribution system which interconnected PV systems.

Outline：Recently, the amount of distributed generation (DG) such as photovoltaic system and wind power generator system installed in a distribution system has been increasing because of reduction of the effects on the environment. However, the harmonic troubles in the distribution system are apprehended in the background of the increase of connection of DGs through the inverters and the spread of power electronics equipment. In this paper, the authors propose a restraint method of voltage total harmonic distortion (THD) in a whole distribution network by active filter (AF) operation of plural power conditioner systems (PCS). Moreover, the authors propose a determination method of the optimal gain of AF operation so as to minimize the maximum value of voltage THD in the distribution network by the real-time feedback control with measured data from the information technology (IT) switches. In order to verify the validity of the proposed method, the numerical calculations are carried out by using an analytical model of distribution network interconnected DGs with PCS.

ISSN：03854213

Outline：It is well known in the numerical simulation of synchronous generator that the damper winding contributes to suppress the three-phase circuit unbalance in power systems. However, experimental study has not been performed yet. In this paper, authors verify experimentally the suppression of the three-phase unbalance by the damper windings. In order to simulate the three-phase unbalance, a 470W dispersed generator of single-phase-two-line type is connected to a three-phase laboratory-scale power system that includes a 6kVA synchronous generator. Authors measured and analyzed line voltages and currents as well as damper bar currents both with and without dispersed generator. The influence of damper windings to the unbalance of three-phase circuit is also investigated. The results show that the damper winding contributes to improve the three-phase unbalance.

ISSN：03854213

ISSN：03854213

Outline：This paper describes the results of experimental investigation on the effects of damper winding of a 4-pole synchronous generator at the synchronous generator transient. It is known in the simulation that the damper winding acts effectively at the synchronous generator transient condition. However, experimental proof has not been performed yet. Then, experiments on damper effects were conducted in this paper using a laboratory-scale power system. The damper winding of tested generator consists of 5 damper bars each pole and the number of working damper bars can be changed manually. Damper currents at each bar were measured by a Rogowski coil. FFT analysis was applied to both damper currents and armature currents under different operating conditions. Relationships between damper currents in the rotor and armature currents in the stator were made clearer than before.

ISSN：03854213

Outline：In the field of electrical power system, various approaches, such as utilization of renewable energy, loss reduction, and so on, have been taken to reduce CO2 emission. So as to work toward this goal, the total number of distributed generators (DGs) using renewable energy connected into 6.6kV distribution system has been increasing rapidly. However, when a fault occurs such as distribution line faults and bank faults, DGs connecting outage sections are disconnected simultaneously. Since the output of DGs influences feeder current and node voltage of distribution system, it is necessary to determine the optimal system configuration considering simultaneous disconnection and reconnection of DGs.In this paper, the authors propose a computation method to determine the optimal restoration configuration considering many connections of DGs. The feature of determined restoration configurations is prevention of the violation of operational constraints by disconnection and reconnection of DGs. Numerical simulations are carried out for a real scale distribution system model with 4 distribution substations, 72 distribution feeders, 252 sectionalizing switches (configuration candidates are 2252) and 23.2MW DGs (which is 14% of total load) in order to examine the validity of the proposed algorithm.

ISSN：02850494

ISSN：03854213

Outline：In tandem with the penetration of Renewable Energy Sources (RES) such as photovoltaic and wind power generation to reduce CO2 emissions and conserve energy, development of advanced smart grid technologies is needed to secure a stable power supply of grid with RES by controlling power quality (voltage and frequency) within each secure range. This paper describes Japanese trend of the advanced smart grid technologies to harmonize RES and conventional bulk power system. Furthermore, several ongoing field tests to try to realize Japanese version of smart grid are briefly introduced.

ISSN：03854213

Outline：The line voltage control in a distribution network is one of the most important issues for a penetration of Renewable Energy Sources (RES). A loop distribution network configuration is an effective solution to resolve voltage and distribution loss issues concerned about a penetration of RES. In this paper, for a loop distribution network, the authors propose a voltage control method based on tap change control of LRT and active/reactive power control of RES. The tap change control of LRT takes a major role of the proposed voltage control. Additionally the active/reactive power control of RES supports the voltage control when voltage deviation from the upper or lower voltage limit is unavoidable. The proposed method adopts SCADA system based on measured data from IT switches, which are sectionalizing switch with sensor installed in distribution feeder. In order to check the validity of the proposed voltage control method, experimental simulations using a distribution system analog simulator "ANSWER" are carried out. In the simulations, the voltage maintenance capability in the normal and the emergency is evaluated.

ISSN：03854213

Outline：In recent years, the number of connection of distributed generators (DGs) such as the photovoltaic generation (PV) and wind power generation is increasing, and there is in danger of changing the voltages in a distribution system by the precipitous output variation of DGs. In this study, the authors propose one voltage control method of a distribution system by the static var compensator (SVC) in consideration of cooperation with the load ratio control transformer (LRT) of laggard control response installed beforehand in the distribution system. The proposed method may be able to make the rated capacity of SVC small and may be able to reduce the aggravation of power factor of the distribution system, by setting up the dead band of voltage control appropriately. And the authors propose one determination method of the necessary minimum rated capacity and optimum control parameters of SVC in view of the cost of equipment and high-speed controllability. In order to verify the validity of the proposed method, the numerical calculations are carried out by using a distribution system model.

ISSN：03854213

Outline：This paper describes distribution voltage estimation and a control method using measured data from sectionalizing switches with sensors which are called IT switch. The voltage estimation is based on Particle Swarm Optimization (PSO) and all distribution line voltages are estimated by minimizing the weighted sum of voltage and current error at IT switch. The voltage control maintains all the estimated node voltages within the proper range by changing tap of a LRT in a distribution substation. In order to check the validity of the proposed method, numerical and experimental simulations are carried out on a distribution system model.

ISSN：03892441

ISSN：03854213

Outline：Recently, total number of distributed generators (DGs) such as photovoltaic generation system and wind power generation system connected to an actual distribution network increases drastically. The distribution network connected with many distributed generators must be operated keeping reliability of power supply, and power quality. In order to accomplish active distribution network operation to take advantage of many connections of DGs, a new coordinated operation of distribution system with many connections of DGs is necessary. So far, the authors have proposed a coordinated operation of distribution network system connected with many DGs by using sectionalizing switches control method, sending voltage control method, computation method of acceptable maximum output of DG and determination method of optimal smoothing time constant of wind power generation system with storage battery. In this paper, the authors develop an experiment of scaled-down three-phase distribution system with distributed generators in order to check the validity of the proposed approach.

ISSN：0389-2441

Outline：Through use of smart grids, countries around the world are aiming to realize construction of 21st-century electric systems that provide people with abundant, affordable, clean, efficient and reliable electric power regardless of time or location. In addition to adding advanced functions to the nation's electricity grid and thus enhancing reliability, efficiency and security, a smart grid also contributes to the strategic climate-change goal of reducing carbon emissions. This paper describes the trend toward smart grids in Japan for smooth integration of increased use of renewable energy sources and conventional bulk power systems. Several ongoing Japanese field tests relating to smart grids are also briefly introduced.

Outline：In this paper, the authors propose a power and heat interchange system using fuel cells (FCs) in a collective housing and develop a determination method of optimal operation schedule for FCs in this system. The developed method is based on tabu search which is one of non-linear optimization methods. In the developed method, the optimal operation schedule is determined by using Pareto optimal solutions from two evaluation viewpoints ((1) running cost, (2) CO2 emission). In order to examine the validity of the developed method, numerical simulations are carried out for the collective housing model with 12 houses in winter, summer and middle season, and the optimal operation schedules are determined.

Outline：Recently, total number of distributed generators (DGS) such as photovoltaic generation system and wind turbine generation system connected to an actual distribution network increases drastically. The distribution network connected with many distributed generators must be operated keeping reliability of power supply, power quality and loss minimization. In order to accomplish active distribution network operation to take advantage of many connections of DGS, a new coordinated operation of distribution system with many connections of DGS is necessary. In this paper, the authors propose a coordinated operation of distribution network system connected with many DGS by using newly proposed sectionalizing switches control, sending voltage control and computation of available DG connection capability. In order to check validity of the proposed coordinated operation of distribution system, numerical simulations using the proposed coordinated distribution system operation are carried out in a practical distribution network model.

Outline：This paper deals with experimental investigation on a novel fault location method using air-gap flux distributions of a synchronous generator connected to a power system. Air-gap fluxes are the sum of field fluxes and armature reaction fluxes. Changes in armature current and field current at fault contribute directly to the armature reaction fluxes and field fluxes, then resultant air-gap fluxes. Therefore, air-gap fluxes can be utilized to locate fault. Wavelet analysis is applied to induced voltages of search coils which are wound around a stator tooth top for measurement of air-gap flux. It is shown that fault type and location are estimated from the change of search coil voltages measured during fault.

Outline：Recently, the total number of distributed generation such as photovoltaic generation system and wind turbine generation system connected to distribution network is drastically increased. Distributed generation utilizing renewable energy can reduce the distribution loss and emission of CO2. However the distribution network with the distributed generators must be operated keeping reliability of power supply and power quality. In this paper, the authors propose a computation method to determine the maximum output of a distributed generator under the operational constrains ((1) voltage limit, (2) line current capacity, and (3) no reverse flow to bank) at arbitrary connection point and hourly period. In the proposed method, three-phase iterative load flow calculation is applied to evaluate the above operational constraints. Three-phase iterative load flow calculation has two simple procedures: (Procedure1) addition of load currents from terminal node of feeder to root one, and (Procedure2) subtraction of voltage drop from root node of feeder to terminal one. In order to check the validity of the proposed method, numerical simulations are accomplished for a distribution system model. Furthermore, characteristics of locational and hourly maximum output of distributed generator connected to distribution feeder are analyzed by several numerical examples.

Outline：Since a distribution network has many sectionalizing switches, there are huge radial network configuration candidates by states (opened or closed) of sectionalizing switches. Recently, the total number of distributed generation such as photovoltaic generation system and wind turbine generation system connected to the distribution network is drastically increased. The distribution network with the distributed generators must be operated keeping reliability of power supply and power quality. Therefore, the many configurations of the distribution network with the distributed generators must be evaluated multiply from various viewpoints such as distribution loss, total harmonic distortion, voltage imbalance and so on. In this paper, the authors propose a multi evaluation method to evaluate the distribution network configuration candidates satisfied with constraints of voltage and line current limit from three viewpoints ((1) distribution loss, (2) total harmonic distortion and (3) voltage imbalance). After establishing a standard analytical model of three sectionalized and three connected distribution network configuration with distributed generators based on the practical data, the multi evaluation for the established model is carried out by using the proposed method based on EMTP (Electro-Magnetic Transients Programs).

Outline：This paper presents the results of experimental study on the performance of a Unified Power Flow Controller (UPFC), one of the FACTS (Flexible AC Transmission Systems) controllers. A laboratory-scale UPFC was manufactured and installed on a laboratory electric power system to investigate its multifunctional capabilities as a power flow controller. The UPFC consists of two 4.5kVA, 200V back-to-back voltage-sourced converters, labeled “Converter 1" and “Converter 2", operated from a common DC link provided by a DC storage capacitor of 380V. It can provide independent control of both the real and reactive power flow in the line. Tests were performed to examine the capabilities of UPFC, under one-machine connected to an infinite-bus system. Steady-state responses under various kinds of operating conditions were measured and analyzed.

Outline：In a distribution system, in order to enhance the reliability of power supply, the distribution feeder is divided into several sections by installing sectionalizing switches, and then each of sectionalized sections is connected to different feeder. For example, one feeder is divided into three sections by two sectionalizing switches, and then each of divided sections is connected to other feeder through sectionalizing switch. Since a distribution system with many feeders has many sectionalizing switches, the system configuration is determined by states (opened or closed) of sectionalizing switches. Usually, power utility tries to obtain distribution loss-minimum configuration among large numbers of configuration candidates. However, it is very difficult to determine the loss-minimum configuration that the mathematical optimality is guaranteed, because it is well known that determination of distribution system's configuration is to decide whether each sectionalizing switch is opened or closed by solving a combinatorial optimization problem. In this paper, the authors propose a determination method of loss minimum configuration which the mathematical optimality is guaranteed for a three sectionalized and three connected distribution feeder network. A problem to determine the loss minimum configuration is formulated as a combinatorial optimization problems with four operational constraints ((1) feeder capacity, (2) voltage limit, (3) radial structure and (4) three sectionalization). In the proposed method, after picking up all partial configurations satisfied with radial structure constraint by using enumeration method, optimal combination of partial configurations is determined under the other operational constraints by using conventional optimization method. Numerical simulations are carried out for a distribution network model with 140 sectionalizing switches in order to examine the validity of the proposed algorithm in comparison with one of conventional meta-heuristics (Tabu search).

Outline：Distributed generators (DGs) such as fuel cells and solar cells etc. are going to be installed in demand side of distribution systems. The distributed generators can reduce distribution loss by appropriate allocation. However, there are several problems to install DGs such as service restoration of distribution system with DGs and so on. When one bank fault of distribution substation occurs in distribution system, since DGs are simultaneously disconnected from the system, it is not easy to restore isolated load by one bank switching in distribution substation. Therefore, a service restoration method to determine restoration configuration and restoration procedures (switching procedure from normal configuration to restoration configuration) taking into account simultaneous disconnection of DGs is needed. In this paper, the authors propose a computation method to determine the optimal restoration configuration and the restoration procedure considering simultaneous disconnection of DGs by one bank fault of distribution system. In the proposed algorithm, after all of restoration configuration candidates are effectively enumerated under the operational constraints, the optimal configuration to restore the isolated load is selected among enumerated configuration candidates. After determining the optimal restoration configuration, the optimal restoration procedures are obtained by greedy algorithm. Numerical simulations are carried out for a real scale system model with 237 sectionalizing switches (configuration candidates are 2237) and 21DGs (total output is 5250kW which is 3% of total load) in order to examine the validity of the proposed algorithm.

Outline：In order to devise countermeasures for harmonic disturbances and harmonic suppression in power systems effectively, it is necessary to develop a harmonic analysis approach with high accuracy. The major harmonic analysis approach is to recreate harmonic distribution in a power system model by using a simulation method. However, in order to carry out high accuracy estimation of the harmonic distribution using the simulation method, after creating a load model which consists of several parameters associated with the measured harmonic impedance, the optimal load model parameters must be determined. So far, appropriate load model parameters have been determined by trial and error. Therefore, a systematic approach to determine the optimal load model parameters is needed to estimate the measured harmonic impedance with high accuracy. In this paper, a determination method for the optimal load model parameters to estimate the measured harmonic impedance is proposed. The proposed method is based on Particle Swarm Optimization (PSO), which is one of optimization methods by using concept of swarm intelligence. In order to check the validity of the proposed method, the load model parameters estimated by the proposed method are evaluated using test data and filed data of Hokuriku electric power company.

Outline：Sending voltage profile of distribution feeder is controlled by changing a tap of distribution transformer. In a distribution network with distributed generators, for reasons of effect of reversed flows from them and existence of a great number of sending voltage profile candidates, it is not easy to control sending voltage profile within the acceptable voltage limit. In this paper, in order to determine the optimal sending voltage profile of distribution transformer in a distribution network with distributed generators, the authors propose a new method to determine the optimal sending voltage profile so as to minimize total number of tap position's change per day under constraints of acceptable voltage limit. In the proposed method, after calculating acceptable range of three phase voltage of distribution feeder, the optimal profile of tap position within the calculated acceptable voltage range is determined among these candidates by using reduced ordered binary decision diagram (ROBDD) which is an efficient enumeration algorithm. In order to check the validity of the proposed method, numerical simulations are carried out for a distribution network model with a distributed generator.

Outline：Three-phase voltage imbalance occurs by variety of connecting points of single-phase loads. In order to improve three-phase voltage imbalance, connecting points of single-phases loads are exchanged. System planner has to decide how to exchange connection of single-phase loads with the minimum planning cost in order to improve three-phase voltage imbalance. However, since there are many patterns of connection for single-phase loads, it is not easy to determine the optimal connection pattern for single-phase loads with the minimum planning cost under the constraint for improving voltage imbalance. In this paper, authors propose a computational method to support the planner's decision of single-phase loads connection systematically. The proposed method, which is based on effective enumeration algorithm, can obtain the optimal single-phase loads connection pattern, which satisfies with constraint of voltage balance and has the minimum total number of single-phase loads exchanged from previous single-phase loads connection. In the proposed method, three-phase iterative load flow calculation is applied to calculate rate of three-phase voltage imbalance. Three-phase iterative load flow calculation has two simple procedures: (Procedure1) addition of load currents from terminal node of feeder to root one, and (Procedure2) subtraction of voltage drop from root node of feeder to terminal one. In order to check the validity of the proposed method, numerical results are shown for a distribution system model with DG.

Outline：Distribution planning must be carried out by considering (1) geographic information such as allocation of loads and feeders, (2) operational conditions such as line current capacity, voltage drop limit and distribution loss, and (3) facility cost and so on. In order to systematically support the above work by computational approach, optimization techniques are available. In this paper, a computational method to support distributional planning systematically is proposed by introducing (1) geographical optimization technique and (2) configuration optimization technique. The geographical optimization is to determine which of sectionalized lines should supply power to future appeared loads so as to maximize availability ratio of feeders. The configuration optimization is to determine states of sectionalizing switches (opened or closed) so as to minimize distribution loss under the constraints such as the line current capacity, voltage drop limit and radial structure. In the proposed method, after the geographical optimization is carried out to determine future section loads, operational conditions are evaluated by the configuration optimization. If the operational constraints are not satisfied, previously prepared expansion plan candidates are evaluated quantitatively, and then the best candidate is decided. Voronoi diagram is applied to realize the geographical optimization, and tabu search is used to accomplish the configuration optimization. In order to check the validity of the proposed method, numerical results are shown for a distribution system model.

Outline：Local power systems (66kV) are served from the 275kV or 154kV substations. In order to maintain power supply reliability, the transmission lines are connected to several substations, and the operational configuration is radial. Since practical local power system has a number of transmission lines, many configuration candidates occur. It is expected to effectively evaluate these configuration candidates from various viewpoints such as reliability of power supply, transmission loss and so on. In this paper, the authors propose a multi objective evaluation method by using deterministic and probabilistic approaches for local power system configuration. In the proposed multi objective evaluation method, after selecting system configuration candidates which satisfy N-1 security by using an optimization method based on Boolean function, these candidates are evaluated from viewpoints of expected outage time, transmission loss and facility operation rate. In order to check the validity of the proposed method, numerical results are shown for a practical local system model with about 39 × 1027 configuration.

Outline：Open access to electric power transmission networks has been carried out in order to foster generation competition and customer choice in the worldwide. When several PPSs request to simultaneously supply power to customers based on bilateral contracts, it is expected that transmission network accepts amounts of wheeled power requested by the PPSs as much as possible. It is possible to maximize total requested wheeled power by controlling power flow through transmission lines. It is well known that FACTS device is available to control line flow flexibly. In this paper, in order to maximize total wheeled power simultaneously requested by several PPSs, the authors propose an algorithm to determine the optimal reactance of TCSC (one of FACTS devices). The proposed algorithm is based on Particle Swarm Optimization (PSO), which is one of optimization methods based on swarm intelligence. In the proposed algorithm, PSO is improved to enhance ability of searching global minimum by giving different characteristic to behavior of each agent. In order to check the validity of the proposed method, numerical results are shown for 6 and IEEE 30 bus system models.

Outline：Open access to electric power transmission networks has been carried out in order to foster generation competition and customer choice in the worldwide. Available transfer capability(ATC) is the largest additional amount of power above some base flow which can be transferred between two sets of buses under constraints such as voltage limit, overloads, stability and n-1 contingencies. Calculation of ATC is important to promote open access to electric power transmission networks. If there are several ATC between two sets of buses, simultaneous transfer capability(STC) of power transmission networks must be calculated. STC is defined as the ability of a transmission network to allow for the reliable movement of electric power from areas of supply to areas of demand. In this paper, a new algorithm to precisely calculate STC is proposed. The proposed method is based on linear programming(LP) based DC power flow and optimal power flow (OPF). Namely, LP base DC power flow is used to obtain the initial solution of STC, and then OPF using successive quadratic programming (SQP) is applied to obtain feasible solution of STC under the operational constraints such as balance of power supply and demand, voltage limit, overloads, generation limit, steady state stability and n-1 contingencies. Furthermore, if power wheeling transactions by several PPSs are simultaneously requested for the transmission network, it seems that the acceptable quantity for the requested wheeling power must be indicated to PPSs from a view point of the transmission network reliability. An algorithm to calculate the acceptable quantity for the requested wheeling power is also proposed by using STC computation. In order to check the validity of the proposed methods, numerical results are shown for 6 and IEEE 30 buses system models.

Outline：Dispersed generators (DGs) such as fuel cells and solar cells etc. are going to be installed in demand side of power systems. The dispersed facilities can reduce distribution system loss by the appropriate allocation. However, when a DG which has large capacity is disconnected from the distribution network by a fault, violation of the operational constraints such as the line capacity and voltage drop may occur. From a view point of system reliability, robust system configuration for suddenly disconnecting DG from the distribution network must be determined, since system operators can not control DG connection to the network in the on-line. In this paper, the authors propose an algorithm to determine the loss-minimum configuration for a distribution system with DGs maintaining system reliability. Namely, in the proposed algorithm, when the loss-minimum configuration is determined under the line current capacity and voltage drop constraints, n-1 contingencies for DGs are also considered. In order to determine the loss-minimum configuration, tabu search added strategic oscillation is employed. Numerical simulations are carried out for a real scale system model with 118 sectionalizing switches (configuration candidates is 2118) in order to examine the validity of the proposed algorithm. Furthermore, performance of the proposed method is compared with a conventional metaheuristic method, which is Simulated Annealing (SA), through numerical simulations for the system model.

Outline：In Japan, local power systems (77kV) are served from the 275kV or 154kV substations. For enhancement of power supply reliability, the transmission lines are connected to several substations, and the operational configuration is radial. The local power system's configuration is determined by connecting and disconnecting transmission lines so as to keep the radial structure and satisfy the operational constraints. When a local power system has a number of transmission lines, many configuration candidates occurs. Recently, an IEEJ committee made a practical scale local system model (IEEJ Local System Model). Since IEEJ Local System Model has 76 transmission lines, the total number of configuration candidates is 276(=7.5×1022 approximately). In this paper, the authors try to strictly obtain the loss-minimum configuration under constraints such as substation capacity, line capacity and radial structure in IEEJ Local System Model. In order to obtain the optimal configuration, a new computation algorithm is proposed. In the proposed algorithm, the configuration determination problem is replaced as two combinatorial optimization problems based on the operational constraints (1)substation capacity, (2)line capacity and (3)radial structure). One combinatorial optimization problem (subprobleml) is to pick up all partial configurations satisfied with line capacity and radial structure constraints. The, other one (subproblem2) is to select the partial configurations so as to minimize total line loss under the substation capacity constraint. By using the enumeration method, subprobleml is solved. Subproblem2 is solved by using the reduced ordered binary decision diagram (ROBDD). Since the proposed method is based on enumeration and Boolean function, the optimality of obtained solution is guaranteed.

Outline：Secondary power systems (66kV) with radial system structures are served from the 275kV or 154kV substations. For enhancement of power supply reliability, the transmission line is connected to another substation. However, when the radial power system has a number of connected feeders, the combinatorial number of possible system structures by switching CBs becomes very large. In this paper, a new solution method to determine the optimal secondary power system configuration is proposed. In the proposed method, the determination problem of the optimal system structure is treated as a minimum spanning tree problem with constraints, and then it is solved by using reduced ordered binary decision diagram (ROBDD). Since the proposed method is based on Boolean function, the optimality of obtained solution is guaranteed. In order to check the validity of the proposed method, numerical simulations are carried out for system models, and the results obtained by branch and bound method are compared with these of proposed method.

Outline：Dispersed generators (DG) such as fuel cells and solar cells etc. are going to be installed in demand side of power systems. The dispersed facilities can reduce distribution system loss by the appropriate allocation. So far, planning and operation of distribution system with the dispersed facilities have been discussed. In this paper, the authors discuss about how much the distribution system loss minimization can be reduced if DGs are optimally allocated at the demand side of the distribution system. In order to determine the optimal allocation and size of DG for minimizing the distribution system loss, an algorithm based on tabu search is employed. The proposed algorithm consists of the repetition of nested use of the tabu search algorithm. Namely, in the proposed algorithm, in one computational iteration, after the location of DG is temporarily determined by tabu search, the size of DG is also determined by tabu search so as to minimize the distribution system loss for the temporarily determined allocation. Numerical simulations are carried out for two system models in order to examine the validity of the algorithm.

Outline：This paper proposes a new algorithm to obtain an approximate optimal solution for the load balancing of large-scale radial distribution system. Since the problem is formulated as a combinatorial optimization problem because of the discreteness of load section connection, it is difficult to solve a large-scale combinatorial optimization problem accurately within the reasonable computational time. So for, in order to find an approximate optimal solution quickly, the authors have published a solution method based on the network flow incremental algorithm. Although the incremental algorithm can find the optimal solution to the problem, the result is not always radial (feasible). So as to overcome this deficiency, in this paper, the authors propose a new algorithm that can find the load balanced radial distribution feeder configuration. The proposed algorithm picks up load by a unit of a section load. Therefore, the problem is elementarily a combinatorial optimization problem. However, to avoid the permutation, the algorithm employs a heuristic algorithm based on the mathematical concept of the optimality of the incremental algorithm. In picking up section load, the algorithm can take into account not only the current load balance but also the expected load which feeders should pick up afterward. To realize this algorithm, a combination of labels is introduced to each node. Through numerical examples, the validity of the proposed method is examined.

Outline：In planning a distribution system for urban area, when a feeder is newly installed, the route of the feeder must be determined among many candidates, considering investment cost and constraints. However, it is difficult for planners to find the optimal route of the newly installed feeder. Because too many candidates of route exist which can be constructed along the road on service area of the power company. It must be considered whether the end part of an existing feeder can be used as apart of newly installed feeder within specified loaded value. In this paper, in order to support planners' decision for selecting optimal route of newly installed feeders, the authors have formulated the problem mathematically, and propose a new solution algorithm to find the optimal route by referring Dijkstra Method. Through numerical examples, authors demonstrate the validity of the proposed method.

Outline：Recently the task of planning in power systems is becoming a very complicated process for utility planners. This kind of planning has a lot of objectives to accomplish. In this paper we employ Negotiation Algorithm, which was proposed by the group of Chen-Ching Liu, for subtransmission power system planning to create a plan having many objectives. First, the Goal-Decision-Network(GDN) is constructed to model this planning problem, and Negotiation Algorithm is applied to utilize both subtrasmission system planning GDN, which attempts to capture its knowledge, and negotiation operators, which search for the most feasible and promising decisions in this planning GDN. Finally the negotiation expert system is demonstrated for the subtransmission system planning using a real system.

Outline：The voltage control calculation is the combinatorial optimization problem, and it has been difficult to solve this type of problem quickly with the conventional digital computer. However according to the modelling of excellent parallel processing ability of neurons, it has become possible to carry out the optimization with the Hopfield neural network model. In this paper, in order to solve the voltage control problem we propose an improved Hopfield model which has an individual input-output function for an individual neuron to achieve a drastic improvement in the calculation time.

Outline：In recent years, according to the modelling of excellent information processing ability of neurons, it has become possible to carry out pattern recognitions or optimizations with the neural network theory. In this paper, we show how to introduce the neural network theory to the load-flow calculation of rectangular coordinate. A problem which input-output functions have for neural network applications is pointed out, and effects of changes in load patterns and system size are discussed in terms of the optimal multiplier. Results of simulations are shown with the convergence characteristics.

Outline：If several feeders are interrupted in a severe accident, distribution networks should be restored by reconfiguring switches automatically with smart grid technologies. Although there have been several restoration algorithms developed to find the new network configuration, they might fail to restore the whole network if the network were critically damaged. The network's design has to guarantee that it is restorable under any possible failure for secure power delivery, but it is a computationally hard task to examine all possible failures in a large-scale network with complex electrical constraints. This paper proposes a novel method to find all the critical (unrestorable) line cuts with great efficiency to verify the network design. The proposed method first runs a fast screening algorithm based on hitting set enumeration; the algorithm selects suspicious cuts without naively examining all possible cuts. Next, unrestorable cuts are identified from the suspicious ones with another algorithm, which strictly tests the restorability of the network under each suspicious cut without redundantly repeating heavy power flow calculations. Thorough experiments on two distribution networks reveal that the proposed method can find thousands of unrestorable cuts from the trillions of possible cuts in a large 432-Bus network with no significant false negatives.

Outline：Recently a lot of studies and developments about distributed generator such as photovoltaic generation system, wind turbine generation system and fuel cell have been performed under the background of the global environment issues and deregulation of the electricity market, and the technique of these distributed generators have progressed. Especially, micro grid which consists of several distributed generators, loads and storage battery is expected as one of the new operation system of distributed generator. However, since precipitous load fluctuation occurs in micro grid for the reason of its smaller capacity compared with conventional power system, high-accuracy load forecasting and control scheme to balance of supply and demand are needed. Namely, it is necessary to improve the precision of operation in micro grid by observing load fluctuation and correcting start-stop schedule and output of generators online. But it is not easy to determine the operation schedule of each generator in short time, because the problem to determine start-up, shut-down and output of each generator in micro grid is a mixed integer programming problem. In this paper, the authors propose an online optimization method for the optimal operation schedule of generators in micro grid. The proposed method is based on enumeration method and particle swarm optimization (PSO). In the proposed method, after picking up all unit commitment patterns of each generators satisfied with minimum up time and minimum down time constraint by using enumeration method, optimal schedule and output of generators are determined under the other operational constraints by using PSO. Numerical simulation is carried out for a micro grid model with five generators and photovoltaic generation system in order to examine the validity of the proposed method.

Outline：The introduction of photovoltaic power systems is being significantly promoted. This paper proposes the implementation of a distributed energy management framework linking demand-side management systems and supply-side management system under the given time-of-use pricing program for efficient utilization of photovoltaic power outputs; each system implements a consistent management flow composed of forecasting, operation planning, and control steps. In our framework, demandside systems distributed in the electric distribution network manage individual energy consumption to reduce the residential operating cost by utilizing the residential photovoltaic power system and controllable energy appliances so as not to inconvenience residents. On the other hand, the supply-side system utilizes photovoltaic power maximally while maintaining the quality of electric power. The effectiveness of the proposed framework is evaluated on the basis of an actual Japanese distribution network simulation model from both the supply-side and demand-side viewpoints

Publish Classification：Research paper (international conference proceedings)

Outline：Maintaining voltage levels in distribution networks (DNs) with photovoltaic systems (PVs) is a complicated task for conventional voltage control schemes that only use a load ratio control transformer (LRT) and step voltage regulators (SVRs), because of local voltage fluctuation caused by the introduction of PVs. This paper proposes a coordinated voltage control scheme consisting of multiple kinds of load tap changers (LTCs). The proposed scheme determines the location at which to introduce low-voltage regulators (LVRs) and provides control parameters for the LTCs by considering the behavior of the other LTCs. We carried out numerical simulations using a DN model including PVs to verify the validity of the proposed scheme. The results specify the characteristics of the voltage deviation that cannot be prevented by a conventional voltage control scheme, and the proposed scheme significantly reduces such local voltage deviation.

ISSN：19314973

Outline：The incorporation of photovoltaic (PV) inverters makes the management of voltage difficult for power system operators. One solution is to consider these inverter-based devices as controllable reactive power (VAr) sources and to coordinate them with other voltage regulating devices in the distribution system. This paper proposes some acceptable approximations to quickly formulate and solve a mixed-integer quadratic programming problem to periodically determine the optimal voltage coordination of a load tap changer, voltage regulators, capacitor banks, and PVs on a smart grid platform. The solution to the optimization problem is aided by an iteration-based algorithm. By using the MATLAB software to carry out the simulation and computation, the method is well verified by comparing its generated result with a trustworthy solution obtained from examining all possible coordinating combinations of voltage regulating devices and PVs in a modified IEEE 34-bus system. The effectiveness and features of the method are clearly illustrated on that test system by considering a time-varying load and PV generation. The obtained results demonstrate the practical application of this work to medium-voltage systems. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Outline：Because of the rapid growth of wind power, an electric grid company set the maximum change rate in a time window to share its fluctuation; this set maximum change rate in a time window is called the grid code. Large fluctuations of wind power may cause deviation from the grid code, but no studies discuss how to control an energy storage system (ESS) so that it quickly goes back to satisfying the grid code. The authors proposed three control methods for an ESS when the wind power output deviates; they are (1) ‘restart’, (2) ‘continuance without operation’, and (3) ‘continuance with operation’. One year numerical simulations with two types of grid codes and two wind power output data have been performed to evaluate the methods. From the studies, control method (3) is found to be the best control method for an ESS to minimize capacity when the wind power output deviates from the grid code, and is verified by the numerical simulations. These results help to answer questions on how to reduce deviation time and ESS capacity using the control method when the wind power output deviates from the grid code.

ISSN：0385-4213

Outline：The subject of this study is to propose a power interchange system in a collective housing with residential solid oxide fuel cells (SOFCs) and a robust operation planning method for integrated SOFCs against uncertain energy demand forecast. In this method, the future operation plan for multiple SOFCs is optimized and determined to minimize the expected total primary energy consumption in the collective housing considering uncertainty in demand forecast. If the forecast energy demand includes forecast errors, the result of SOFCs operation will corrupt from the viewpoint of the primary energy consumption. Thus, the output decision problem for SOFCs is formulated by considering the corruption caused by forecast errors, so that the decided SOFC outputs have the robustness against uncertainty in demand forecast. The validity of the proposed method is examined based on numerical simulations from the perspective of the robustness.

ISSN：0453-4662

ISSN：1341-9463

Outline：Waseda University and various enterprises proposed a Zero-Energy-House(ZEH) called “Nobi-Nobi HOUSE” in ENEMANEHOUSE2014. In this ZEH, we carried out a design for the ZEH technology, and was build in Tokyo at January 2014. After the relocated in Shizuoka, it was measured every four seasons in energy consumption, electric-generating capacity and indoor environment. This report shows design of “Nobi-Nobi HOUSE” for ZEH and result of measurement.

ISSN：19493053

Outline：© 2010-2012 IEEE.In this paper, we consider the impact of cyber attacks on voltage regulation in distribution systems when a number of photovoltaic (PV) systems are connected. We employ a centralized control scheme that utilizes voltage measurements from sectionizing switches equipped with sensors. It is demonstrated that if measurements are falsified by an attacker, voltage violation can occur in the system. However, by equipping the control with a detection algorithm, we verify that the damage can be limited especially when the number of attacked sensors is small through theoretical analysis and simulation case studies. In addition, studies are made on attacks which attempt to reduce the output power at PV systems equipped with overvoltage protection functions. Further discussion is provided on how to enhance the security level of the proposed algorithm.

ISSN：21574839

Outline：© 2015 IEEE.In this study, we determine the suitable method and timing for the renewal of the voltage control method using voltage control performance evaluated by the maximum photovoltaic (PV) installation rate possible without voltage deviation. The voltage control method is renewed when the voltage of a distribution system deviates with an existing voltage control method. We determine the most suitable voltage control method, which extends the most PV systems, and define its renewal timing as the moment when the PV installation causes voltage deviation. For the renewal of the voltage control method, changing the control operation of a load ratio control transformer (LRT) and the additional installation of a static VAR compensator (SVC) are considered. A numerical simulation is performed to calculate the limit of PV installation rate of each voltage control method to determine the suitable one and its renewal timing.

ISSN：03854213

Outline：© 2016 The Institute of Electrical Engineers of Japan.The subject of this study is to propose a power interchange system in a collective housing with residential solid oxide fuel cells (SOFCs) and a robust operation planning method for integrated SOFCs against uncertain energy demand forecast. In this method, the future operation plan for multiple SOFCs is optimized and determined to minimize the expected total primary energy consumption in the collective housing considering uncertainty in demand forecast. If the forecast energy demand includes forecast errors, the result of SOFCs operation will corrupt from the viewpoint of the primary energy consumption. Thus, the output decision problem for SOFCs is formulated by considering the corruption caused by forecast errors, so that the decided SOFC outputs have the robustness against uncertainty in demand forecast. The validity of the proposed method is examined based on numerical simulations from the perspective of the robustness.

ISSN：03029743

Outline：© Springer International Publishing Switzerland 2016.The large-scale introduction of renewable energy resources will cause instability in the power supply. Residential energy management systems will be even more important in the near future. An important function of such systems is visualization of appliance-wise energy consumption; residents will be able to consciously avoid unnecessary consumption behavior. However, visualization requires sensors to measure appliance-wise energy consumption and is generally a costly task. In this paper, an unsupervised method for nonintrusive appliance load monitoring based on a semi-binary non-negative matrix factorization model is proposed. This framework utilizes the total power consumption patterns measured at the circuit breaker panel in a house, and derives disaggregated appliance-wise energy consumption. In the proposed approach, the energy consumption of individual appliances is estimated by considering the appliance-specific variances based on an aggregated energy consumption data set. The authors implement the proposed method and evaluate disaggregation accuracy using real world data sets.

Outline：© 2016 IEEE.This paper presents a method for enumerating the feasible load drop compensator (LDC) parameters of on-load tap changer (OLTC) and step voltage regulators (SVRs) in distribution networks utilizing data acquired by SCADA. Deriving the feasible combinations of LDC parameters is becoming important because voltage control is becoming difficult due to the introduction of photovoltaic generation systems, and the voltage control effectiveness of OLTC and SVRs depends on their three LDC parameters: the target voltage, the dead-band, and the impedance. However, an exhaustive search takes a lot of time and heuristics or metaheuristics provide no guarantee on the quality of the solution. The proposed method derives all the feasible LDC parameters, with which tap operation keeping voltage within the proper range is performed, within practical time. To evaluate the performance of the proposed method, the numerical simulation results of the proposed method will be compared with those of the metaheuristics.

Outline：© 2016 Power Systems Computation Conference.The maximization of distributed generation (DG) hosting capacity that takes into account network configuration is a complex, non-linear combinatorial optimization problem. The search space of the configurations becomes massively large in practical-size networks with several hundreds of switches. For this reason, no existing method can handle such large-scale networks. In this paper, we propose a novel exact solution method. Our method consists of two stages. In the first stage, the method divides the entire problem into a set of small subproblems. In the second stage, it converts all subproblems into a compressed data structure called a zero-suppressed binary decision diagram (ZDD), which expresses the combinatorial sets compactly. The proposed method avoids any combinatorial explosion by using the ZDD to enable operations of the weighted combinatorial item sets. We conducted experiments on a large-scale network with 235 switches. As a result, our method obtained the global optimal solution in 49 hours.

ISSN：19493053

Outline：© 2010-2012 IEEE.In distribution network management, switch reconfiguration is an important tool for reducing energy loss. Recently, a variety of annual reconfiguration planning methods considering energy loss have been studied. However, no conventional methods address the reconfiguration periods in fine granularity. Practically, switch durability does not support high-frequency switching. Therefore, this paper proposes a new optimization method for annual reconfiguration scheduling. This method determines switch configurations and their reconfiguration periods with a constraint on the permissible reconfiguration times. In addition, this paper reveals the annual energy loss reduction effect of this optimization. Our method is based on partial network optimization with exhaustive enumeration of all feasible configurations. Experiments were conducted using a standard Japanese distribution network model with 468 switches. The results show that optimizing the reconfiguration periods reduces energy loss by up to 2.1 times, relative to that in a simulated conventional operation, which considers reconfiguration at equal intervals. We believe that this is the first quantitative report to address the difference between optimal reconfiguration scheduling and conventional reconfiguration.

ISSN：21608555

Outline：© 2016 IEEE.This paper presents an enhanced centralized voltage control method of on-load tap changer (OLTC) and step voltage regulators (SVRs) in distribution systems with photovoltaic (PV) and evaluates its effectiveness. A conventional centralized voltage control is effective when its data acquisition period is short because tap operations of OLTC and SVRs are performed after the voltage values in the distribution lines are acquired. However, in distribution systems with high penetration rate of PVs, voltage deviation occurs between the data acquisition intervals because the tap positions can be changed only at the timing when the data are acquired. The proposed centralized voltage control method forecasts voltage fluctuation between the data acquisition intervals and changes to the tap position which maximizes the minimum voltage margin from the voltage limits. The numerical simulation results will be shown to compare the voltage control effectiveness of the proposed method with that of the conventional method.

ISSN：13419463

Outline：Waseda University and various enterprises proposed a Zero-Energy-House(ZEH) called "Nobi-Nobi HOUSE" in ENEMANEHOUSE2014. In this ZEH, we carried out a design for the ZEH technology, and was build in Tokyo at January 2014. After the relocated in Shizuoka, it was measured every four seasons in energy consumption, electric-generating capacity and indoor environment. This report shows design of "Nobi-Nobi HOUSE" for ZEH and result of measurement.

ISSN：07339402

Outline：© 2016 American Society of Civil Engineers. An increased penetration of wind energy into the power system will lead to instability of local voltage and global frequency in Japan. Power flow simulation is a powerful tool for understanding the electrical behavior in the power system caused by wind energy; however, plausible and various wind power profiles are required to perform a meaningful simulation to evaluate the effect of wind generators. This paper proposes a procedure of generating synthetic wind power profiles that involve the plausible short-term fluctuation for a power flow simulation based on the spatial kriging method and the bootstrap method.

ISSN：07339402

Outline：© 2016 American Society of Civil Engineers. This paper proposes a voltage control method during service restoration in the distribution networks with photovoltaic (PV) generator systems. In the current distribution automation system (DAS) process in Japan, voltage dips and surges occur during service restoration because PVs are disconnected simultaneously after a fault and subsequently reconnected after service restoration. However, in the current DAS, voltage regulators such as an on-load tap changer (OLTC) and step voltage regulators (SVRs) are not controlled during service restoration. The proposed DAS estimates the voltage in a distribution network during service restoration, and it controls the tap position of OLTC and/or SVRs according to the predicted voltage. The numerical simulation results using a real-world distribution system model on a real map and PV output profiles derived by actual square kilometer solar radiation data will be shown. Those results indicate that the proposed DAS prevents voltage deviation that occurs as long as the current DAS is used. The results also show high spatial resolution PV output data are needed to prevent voltage deviation absolutely.

Outline：© 2016 IEEE. Maintaining voltage levels in distribution networks (DNs) with photovoltaic systems (PVs) is a complicated task for conventional voltage control schemes that only use a load ratio control transformer (LRT) and step voltage regulators (SVRs), because of local voltage fluctuation caused by the introduction of PVs. This paper proposes a coordinated voltage control scheme consisting of multiple kinds of load tap changers (LTCs). The proposed scheme determines the location at which to introduce low-voltage regulators (LVRs) and provides control parameters for the LTCs by considering the behavior of the other LTCs. We carried out numerical simulations using a DN model including PVs to verify the validity of the proposed scheme. The results specify the characteristics of the voltage deviation that cannot be prevented by a conventional voltage control scheme, and the proposed scheme significantly reduces such local voltage deviation.

ISSN：19314973

Outline：© 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. The incorporation of photovoltaic (PV) inverters makes the management of voltage difficult for power system operators. One solution is to consider these inverter-based devices as controllable reactive power (VAr) sources and to coordinate them with other voltage regulating devices in the distribution system. This paper proposes some acceptable approximations to quickly formulate and solve a mixed-integer quadratic programming problem to periodically determine the optimal voltage coordination of a load tap changer, voltage regulators, capacitor banks, and PVs on a smart grid platform. The solution to the optimization problem is aided by an iteration-based algorithm. By using the MATLAB software to carry out the simulation and computation, the method is well verified by comparing its generated result with a trustworthy solution obtained from examining all possible coordinating combinations of voltage regulating devices and PVs in a modified IEEE 34-bus system. The effectiveness and features of the method are clearly illustrated on that test system by considering a time-varying load and PV generation. The obtained results demonstrate the practical application of this work to medium-voltage systems. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

ISSN：04247760

Outline：© 2017 Wiley Periodicals, Inc. There is a danger of output suppression of high-penetration residential photovoltaic systems due to voltage increase. It is necessa1ry to install new technology to prevent the occurrence of such phenomenon. Therefore, we focused our attention on heat-pump water heaters (HPWHs). HPWHs are usually used to heat water during nighttime because electricity prices are cheaper than during the daytime for the load leveling in Japan. So they can be used as a countermeasure without additional cost if they are operated during the daytime. However, HPWHs do not have sufficient capacity to absorb inverse energy at each residence. Thus, HPWH operation must be optimized to minimize output suppression loss. In this research, we selected four typical sunny days in spring, summer, autumn, and winter. The optimal HPWH operation was calculated by numerical simulation. The optimal monthly HPWH operation was investigated using the weather forecast assuming actual operation in each season.

ISSN：03062619

Outline：© 2017 The Authors Power grids connected to renewable energy sources must cope with fluctuating output by those sources. One method to do so is for the power grid company to accept bids to increase grid stability. These bids are accepted via capacity market auction of increasing grid stability. These offers are to increase the maximum power capacity by using power stations (both utility and non-utility stations) and by reducing electricity consumption via demand response. One candidate for achieving this is a district heating and cooling (DHC) system installed with combined heat and power. However, the electricity adjustment (EA) operation needed by the DHC for the auction is complicated because the system consists of boilers, water heaters, chillers, generators, and other items. To investigate the possibility of using DHC systems for capacity market auctions, this paper proposes two models for operating a DHC system: electricity-adjustment capacity (EAC) provision and EA operation. In addition, to develop methods for evaluating the cost of the proposed operational methods, a model DHC system is formulated with an actual DHC system as a basis. Using the models, numerical simulations are conducted by particle swarm optimization. Then, the running costs of EAC, EA, and normal operation are calculated. The results show that the running costs of the proposed operations are relatively stable by day and season, not varying beyond the range of ±10%. Nevertheless, the running costs in spring and fall are be lower than those in summer and winter. The cost of providing EAC is no more than 1% the cost of normal operation, and the cost of EA itself is no more than 2% that of normal operation.

ISSN：19493053

Outline：© 2016 IEEE. The introduction of photovoltaic power systems is being significantly promoted. This paper proposes the implementation of a distributed energy management framework linking demand-side management systems and supply-side management system under the given time-of-use pricing program for efficient utilization of photovoltaic power outputs; each system implements a consistent management flow composed of forecasting, operation planning, and control steps. In our framework, demand-side systems distributed in the electric distribution network manage individual energy consumption to reduce the residential operating cost by utilizing the residential photovoltaic power system and controllable energy appliances so as not to inconvenience residents. On the other hand, the supply-side system utilizes photovoltaic power maximally while maintaining the quality of electric power. The effectiveness of the proposed framework is evaluated on the basis of an actual Japanese distribution network simulation model from both the supply-side and demand-side viewpoints.

Outline：© 2017 IEEE. As more photovoltaic systems (PVs) are allocated to both transmission and distribution systems, it has been required to consider constraints of both transmission and distribution systems, such as power shortages and surpluses in transmission systems and voltages and current in distribution systems. This research proposes the framework to consider these constraints, and formulates the optimal allocation of PVs and energy storage systems (ESSs) to prevent the violation of the above constraints.

ISSN：03854213

Outline：© 2018 The Institute of Electrical Engineers of Japan. This paper presents an evaluation of economical capacity of storage batteries equipped with residential PV systems. In around 2019, many of power companies' ten-year contracts with PV system owners will come to expire, pushing down the selling price of PV generated energy. This, if combined with a declining battery price, would make it more economical to self-consume PV generated energy than selling the electricity to the utilities. The authors explore the optimized storage battery capacity and charge-discharge pattern by using load and PV output data of 200 houses, and by linear programming. Results show 5.8 kWh battery is suitable for an average house with 4.5 kW PV system when the battery system price is about Y60,000/kWh. The authors analyze the daily storage start timing's impact on reverse power which affects power system operation, the optimum combination of PV and battery capacity, and each house's deciding factors for optimum storage capacity and so on.

Outline：© 2017 IEEE. In order to coordinate controlling devices of utilities in medium-voltage networks with large-scale photovoltaic (PV) inverters, a revelation of clustered impacts of rooftop solar panels in PV dominated low-voltage networks is necessary. This paper first investigates impacts of smart functions on system performance if they are installed in rooftop solar inverters. An optimization is then formulated based on conflicts that have been revealed. Through simulations in a typical Japan low-voltage system with real data, investigation and optimization results show that optimal inverter settings for rooftop solar are feasible and they could help improve system performance.

ISBN：978-4-902553-99-4

ISBN：978-4-542-30183-2

Dictionary/EncyclopediaTotal Number of Pages：1900Responsible Number of Pages：1235-1252ISBN：9781118755488

Venue：New Orleans, USA

Venue：Eindhoven, Netherland

Venue：Vienna

Venue：Arlington, VA, USA

Venue：Lyon, France

Venue：Italy

Venue：Eindhoven, Netherland

Venue：Arlington, VA, USA

Venue：Hong Kong

Venue：Hong Kong

Venue：Hong Kong

Venue：Hong Kong

Venue：Hong Kong

Venue：Hong Kong

Outline：Spring conference of the KIEE power engineering section