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In recent years, the aggregation business has gained a lot of attention in Japan. Aggregators will make contracts with customers with photovoltaic (PV) power systems and battery energy storage systems (BESSs) including electric vehicles (EVs) to participate in electricity markets. Aggregators might have to pay electricity supply‐demand imbalance charges when generated and consumed energies contracted at the day‐ahead supply‐demand market are different from those at the current day operation due to distribution network constraints such as voltage and power flow limitations. Therefore, the information on network constraints is very important for aggregators to determine their day‐ahead schedules. In this paper, we evaluated the relationship between aggregator supply‐demand schedules and the distribution system operation. It was assumed that the reverse power flow limitations due to network constraints are notified to the aggregators by distribution system operator (DSO). Two cases of the aggregators' schedules of PV systems and stationary BESSs were compared in the simulations. In addition, aggregator strategies for making adequate schedules were evaluated. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient method for photovoltaic (PV) system output forecasting by deep Boltzmann machines (DBM) with scatter search‐predator‐prey brain storm optimization (SS‐PPBSO). DBM plays a key role to extract features of input variables while SS‐PPBSO is a new evolutionary computation that combines PPBSO with scatter search. In recent years, as renewable energy, PV systems are positively introduced into power network in Japan so that power system operation becomes complicated due to the uncertainty. To overcome this challenge, it is required to forecast PV outputs that are influenced by weather conditions significantly. This paper proposes a new efficient PV output forecasting method with DBM that makes use of SS‐PPBSO in learning. The effectiveness of the proposed method is demonstrated for real data of a PV system. [ABSTRACT FROM AUTHOR]

Electric vehicle (EV) will prevail in the near future and many EVs are expected to be parked all day or almost all day according to a survey in Japan. They can contribute as vehicle‐to‐grid (V2G) to primary frequency regulation in power systems. However, as lithium‐ion battery or EV battery is still expensive, it is economically important to evaluate V2G frequency regulation cost. This paper proposes the evaluation method of the frequency regulation cost. The proposed method is based on the EV battery cost and longevity, which is shortened by performing the frequency regulation. The battery degradation consists of calendar aging and cycle aging, and an empirical model is used in this paper. Simulation results are shown using the proposed method under the various conditions such as state of charge (SoC) of the EV battery. Those results indicate a V2G control strategy to increase the cost–benefit of primary frequency regulation. [ABSTRACT FROM AUTHOR]

Abstract: Recently, wind power generation are installed as a countermeasure for the environmental issue in Japan. However, wind power generation output is fluctuated due to wind condition. Moreover, it is some negative impact for system operation such as the economic load dispatching control and the load frequency control. In Japan, NEDO has started the project as a countermeasure for massive penetration of wind power generation in 2014, called “R&D Project on Grid Integration of Variable Renewable Energy.” In this paper, we proposed the output fluctuation suppression control method of wind power generation using the battery and forecast data of wind generation output. Specifically, the target value of wind power generation output is calculated to decrease the deviation output from fluctuation suppression code for ramp event using deterministic optimization method. The effectiveness of proposed method is evaluated through the computational simulation using forecast data and actual wind power generation output in Tohoku area. [ABSTRACT FROM AUTHOR]

Because of the significant changes in environmental policies and electric power deregulation in the last decade, a lot of photovoltaic generations (PV) have been and will be installed into the power system in Japan and the ratio of PVs to other synchronous generators will be increased. As a countermeasure against the decrease in the rotational inertia in the whole power system, a virtual synchronous generator (VSG) model control of the PV has so far been proposed. However, the system stabilization effect of the VSG in large‐scale power systems has been unclear. In this paper, a virtual step‐out blocking method of VSG for improving the transient stability is proposed. In addition, the necessity of governor control of VSG in a large‐scale power system is discussed. Finally, the rated kw and kwh capacities of the battery required for realizing the VSG‐model control are evaluated. [ABSTRACT FROM AUTHOR]

SUMMARY This paper analyzes influence of resource allocation in R&D of solar cells in Japan. First, it estimates solar cell price in Japan in the case resource allocation for R&D of crystalline silicon solar cells was not significantly reduced, but maintained almost constant level. For the projection, it does not use experience curve, but models technological progress, price reduction, of solar cell in Japan with a variable technology knowledge stock by excluding mass production effects. Second, solar cell prices in other countries are estimated based on their market share in the global solar cell production. The estimated solar cell price in Japan under the assumed resource allocation decreases by about 30% compared to the actual one and it, therefore, could be competitive to the estimated solar cell prices in China and Taiwan. In this case, Japan could maintain its top market share in the global solar cell production several years longer. Instead of the Japan's Feed-in Tariff with subsidy, net-metering without subsidy is enough for keeping almost the same internal rate of return of residential PV systems for new and existing houses. This paper will be helpful to cost-effective R&D planning by a modeling and simulation approach. [ABSTRACT FROM AUTHOR]

This paper reviews on the trends in extremeweather events induced by global climate change. The number of tropical cyclones (TCs) making landfall on Japan and their intensity show no discernible long-term trend in the past observation record, while the translation speed of TCs shows significant decline. The intensification of heavy rainfalls and extratropical cyclones are also confirmed. Recent simulation studies indicate that the global warming would increase the maximum wind speed and rainfall associated with the TCs. The intensification of extratropical cyclones, heavy rainfalls/snowfalls, tornados, and lightning strikes are also predicted. [ABSTRACT FROM AUTHOR]

SUMMARY This paper evaluates the impact of an extensive introduction of electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs) on the energy supply mix in Japan. Energy consumption in Japan's transport sector has been dominated by petroleum, and CO2 emissions in this sector account for 20% of Japan's CO2 emissions. Therefore, the deployment of clean energy vehicles, such as EV and PHEV, is expected to play a significant role in tackling energy security and environmental concerns. In order to assess the energy and environmental benefits of EV and PHEV, we develop an energy system model integrating an optimal power generation mix model and a vehicle penetration model, with consideration of the optimal electricity charging profile of those advanced vehicles. The calculated results suggest that massive EV penetration serves as an energy saving measure in Japan's whole energy system due to significant petroleum reductions exceeding the growth of fuel input into the power generation sector derived from significant EV and PHEV penetration. Massive EV deployment is estimated to contribute to CO2 mitigation in the energy system as well. Evaluating CO2 emissions by mileage by automobile, however, carbon emissions by mileage for EVs is almost equivalent to that of gasoline hybrid vehicles (HEVs) in the case of decommissioning of nuclear power plants, which eventually causes a higher carbon intensity of the electricity supply. [ABSTRACT FROM AUTHOR]

SUMMARY: In almost all Japanese railway companies, rolling stock management still relies on manual procedure. As density of trains and interconnectivity between lines are increased, a support system for the management gets to be important. This paper focuses on a scheduling task for vehicle units’ operation and a support system for rescheduling vehicle units’ operation in train service disruption. A schedule of vehicle units’ operation is modified by a dispatcher to keep consistency between train timetable and vehicle unit assignment. When there is no solution, the dispatcher has to ask a train service manager to change train timetable. To support this task, we developed an algorithm of rescheduling vehicle unit operation, which included relaxation of constraints. Our algorithm represents constraints as a network model, and, if necessary, relaxes constraints by modifying the network model during search of a solution. This paper indicates the network model, the algorithm of searching for a solution as relaxing constraints, and numerical experiments using a real middle‐size data. The results of the experiments showed that our algorithm could calculate various solutions with relaxed constraints. Analyzing the solutions at the viewpoints of train service and rolling stock operation, we showed the effectiveness of a system that proposes various solutions using our algorithm. [ABSTRACT FROM AUTHOR]

SUMMARY Because of significant change in environmental policies and electric power deregulation in the last decades, a lot of photovoltaic (PV) generations have so far been installed to the power system in Japan. When a huge amount of PVs generation is installed into the power system, we are very much concerned that the disconnection of the PVs due to a system fault has a big impact on the power system stability and transient voltage stability. So it is important to equip the PV with Fault Ride Through (FRT) function in order to maintain power supply-demand balance. In addition, Dynamic Voltage Support (DVS) function of the PV is effective to recover the voltage after the system fault. However, it is unclear how the PVs which are equipped with the FRT and DVS functions affect transient stability and voltage stability. In this paper, how the power factor of the PV power output affects the power system after a system fault is analyzed using P- δ curve. Then, a new PV power factor control method for improving the transient stability is proposed and its effectiveness is shown by digital simulations on a simple power system model. [ABSTRACT FROM AUTHOR]

The photovoltaic (PV) power output might be frequently curtailed to maintain electricity supply‐demand balance in future power systems. In our previous study, we proposed a new method for updating the battery energy storage system (BESS) charge/discharge and the generator unit commitment (UC) schedules based on the forecasted and actual PV power outputs. The forecast dataset was updated every 3 h (eight times a day). Although the simulation results showed that the proposed method could reduce the supply‐demand imbalances, it was not clear whether the forecasted or actual values made contributions. Therefore, in this study, we propose and evaluate a real‐time scheduling and operation method using the forecasted and actual PV power outputs assuming that the forecasted dataset is updated only once a day. Numerical simulations of supply‐demand operations are conducted on the power system model of the Kanto area of Japan for one year. The results show that the previous study method has a slight advantage over proposed method in terms of curtailed PV energy and operational cost of thermal generators reduction, but the difference is very small, indicating that the contribution of the actual PV power outputs is greater than that of the forecasted PV power outputs. [ABSTRACT FROM AUTHOR]

Recently, dynamic wireless power transfer (DWPT) for battery electric vehicles has been actively studied because it can enhance their cruising range and reduce their charging time. An SS type WPT circuit is simpler and more efficient than a WPT circuit with a filter, such as an LCC type WPT circuit. By contrast, the leakage magnetic field generated by the harmonic current is a problem that needs to be addressed. The leakage magnetic field is limited by the Radio Act and the Ordinance for Regulating Radio Equipment in Japan. This study aims to reduce the leakage magnetic field generated by the harmonic current using a high‐frequency switching technology. The inverter and rectifier are operated using pulse width modulation (PWM) with a high carrier frequency. The effectiveness of the proposed method was experimentally verified using a GaN inverter and rectifier. As a result, the proposed method can drastically reduce the leakage magnetic field, especially, the magnetic field generated by the current harmonics of order greater than five. [ABSTRACT FROM AUTHOR]

SUMMARY To assure power system stability when variable photovoltaic (PV) power generation is deployed on a large scale, accurate irradiance forecasting will be important in the near future. A substantial amount of PVs will be generating power at numerous locations in the power service area, and it will be necessary to predict the total PV output for supply/demand balancing control. Therefore, irradiance forecasting accuracy should be verified using the total irradiance at numbers of sites equivalent to areas with large-scale PV deployment. This paper reports an investigation of the accuracy of an approach to area total irradiance prediction based on regional numerical weather prediction data from the Japan Meteorological Agency. The forecast area total irradiance is compared to the assumed total area irradiance for numbers of sites equivalent to large-scale PV deployment. [ABSTRACT FROM AUTHOR]

SUMMARY This paper investigates Japan's long-term energy outlook to 2050 taking into consideration the massive deployment of solar photovoltaic (PV) systems and wind power generation under a nuclear energy scenario. The extensive introduction of PV systems and wind power systems is expected to play an important role in enhancing electricity supply security after the Fukushima nuclear power accident, which has increased the uncertainty of the future additional construction of nuclear power plants in Japan. Against this background, we develop an integrated energy assessment model composed of both an econometric energy demand and supply model and an optimal power generation mix model. The latter model is able to explicitly analyze the impact of output fluctuations for various renewable energy sources at a detailed time resolution of 10 min on 365 consecutive days, incorporating the role of stationary battery technology. The simulation results reveal that intermittent fluctuations derived from a high penetration level of those renewables are controlled by quick load following operation by natural gas combined cycle power plants, pumped-storage hydro power, stationary battery technology, and output suppression of PV and wind power generation. The results show as well that massive penetration of renewables does not necessarily require a comparable scale of stationary battery capacity. Additionally, in the scenario, which assumes the decommissioning of nuclear power plants with a lifetime of over 40 years, the required PV capacity in 2050 amounts to more than double the PV installation potential in both buildings and abandoned farmland areas. [ABSTRACT FROM AUTHOR]

SUMMARY Solar power business has been expanding rapidly in Japan since the new feed-in tariff began in July 2012. Generally, monitoring for failure detection and total electric generating capacity is performed by the power conditioning system (PCS) in a large-scale photovoltaic (PV) power plant. Although PCS monitoring can detect its own failure or a reduction in power generation amount, it is difficult to monitor in a PV string/panel. In this paper, a new failure detection method effective for detection in PV strings, by collecting the current value of each string measured at each terminal and analyzing these data, is proposed. The data collection is performed utilizing the Digital Enhanced Cordless Telecommunications wireless communication method, realizing easy installation in both existing and new PV power plants. Finally, the effectiveness of this proposed method is shown in real-facility demonstration experiments using the F Onomichi PV power plant. [ABSTRACT FROM AUTHOR]

SUMMARY This paper focuses on residential photovoltaic systems in Japan. It projects the installation and installed capacity of residential photovoltaic systems by analyzing the correlation between their payback period and annual installation in new and existing homes. Exponential and hyperbolic curves are used for correlation analysis. However, the exponential curve gives a better fit than the hyperbolic one. PV installation in new houses shows a stronger correlation with the payback period than with existing houses. For the installation projections, target and delayed scenarios are assumed. In the target scenario, the target price is achieved as planned. However, it is achieved later in the delayed scenario. Ongoing subsidies and feed-in tariffs are also assumed. Based on the results of the analysis, the target cumulative installation and installed capacity are achieved in the target scenario. They are not significantly affected even without subsidies and feed-in tariffs. But they are reduced by almost half in the delayed scenario compared with the target scenario. This means that systemic price reductions resulting from research and development as well as mass production are more effective than ongoing dissemination promotion programs. To achieve the target capacity, not only cost reductions but also conversion efficiency improvements through research and development are indispensable. [ABSTRACT FROM AUTHOR]

This study investigated cost‐effective energy strategies for realizing net zero CO2 emissions in Japan by 2050, employing an energy system optimization model with hourly electricity balances. The detailed temporal resolution enables the model to capture the intermittency of variable renewable energy (VRE) and the costs of system integration measures. Siting constraints on VRE, such as prohibiting solar PV and onshore wind developments in forests and offshore wind developments inside fishery rights areas, are incorporated in the model to reflect the environmental protection and social acceptance perspectives. Simulation results imply that a well‐balanced power generation mix, combining renewables, nuclear, gas‐fired with carbon capture and storage, as well as ammonia‐fired, would contribute to curbing mitigation costs. In contrast, a simulation case with very high VRE penetration poses economic challenges. The average shadow price of electricity in 2050 in a 100% renewables case (RE100) is projected to be more than doubled from a reference case which is based on middle‐of‐the‐road assumptions. Marginal CO2 abatement cost in 2050 increases from 49,200 JPY/tCO2 in the reference case to 75,300 JPY/tCO2 in the RE100 case. The economic viability of high VRE penetration is improved by relaxing the siting constraints, although it may raise environmental and social concerns. [ABSTRACT FROM AUTHOR]

SUMMARY In recent years, frequent damage to wind turbines by winter lightning has been reported in the region along the Sea of Japan. It is a serious finding that lightning hits concentrate on wind turbines in this region. The authors investigated the increase rate of the frequency of lightning hits on wind turbines due to wind turbine construction by using LLS (lightning location system) data. As a result, an experimental formula to estimate the increase rate of the frequency of lightning hits on wind turbines as a function of parameters related to the construction conditions, namely the height of wind turbines, the height above sea level, and the latitude, is proposed. [ABSTRACT FROM AUTHOR]

In Japan, installed capacity of variable renewable generation (VRG) is rapidly increasing. Through the efforts to make VRG into one of main power resource, vehicle‐to‐grid (V2G) is considered as an effective source of flexibility, which is concerned to lack under large amount of VRG. In this study, we analyze the cost reduction effect of using V2G as system flexibility through calculation of day‐ahead unit commitment (UC) in Kyushu area. To consider uncertainty of day‐ahead UC, we calculate UC simulation with operation reserve requirement considering day‐ahead forecast error of photovoltaic generation, followed by economic dispatch simulation using actual photovoltaic generation. V2G as LFC reduces operation cost especially when demand is low, even with 180 000 electric vehicles (EVs). Cost reduction per EV is about 20‐80 JPY/day with 180 000 EVs, which saturates if more EV participates in the control. V2G as operation reserve reduces discharge from EV for about 0.5‐1.5 kWh/day/EV, which results in reducing degradation of EV battery. [ABSTRACT FROM AUTHOR]

SUMMARY Feed-in tariff (FIT) has been enforced in order to promote the utilization of renewable energy since 2012 in Japan. In consideration of FIT, we propose an integration plan for incinerator plants (IPs) with highly efficient power generation for the whole area of a prefecture. The plan includes disposal of forest biomass using the reserve capacity of IPs. The model prefecture's population is set to 1,200,000 and the proportion of the forested area is set to 70% of the model area based on data for northeastern Japan. The present 16 IPs are integrated into three new IPs. A relay transportation (RT) facility for waste is located at a decommissioned IP, and the waste from the area is transported to the new IP. In order to calculate the RT costs, an approximation formula for the RT distance is estimated via the IPs integration study. The plan will realize about 37% cost reduction and 1.8-fold CO2 reduction including RT as compared to the plan to update the current IP situation. Forest biomass of 56,500 tons per year, which is about 43% of available forest biomass volume in the model prefecture, can be disposed of at new IPs. On the other hand, enough profit is not expected from the dedicated biomass power generation plant as a result of wood chip processing fees. The plan will help to develop local forestry. [ABSTRACT FROM AUTHOR]

SUMMARY We developed the 550-kV disconnectors that strengthened earthquake proofing by the addition of the damper unit and weight reduction of conductive part based on the damage of the 550-kV disconnectors by the Great East Japan earthquake (March 11, 2011) and inspected the earthquake proofing performance by shake table test. In shake table test, we performed the test by the artificial seismic wave that varied in phase characteristic in addition to the test by resonance method. And, in a high-level earthquake area, we analyzed it about the influence that a phase characteristic of the artificial seismic wave gave to stress to occur in disconnectors. As a result, it is thought that the stress to occur in disconnectors is decided by a primary natural frequency basically because a bending strain to occur to the disconnectors in the time when the resonance frequency ingredient becomes the big acceleration response value grows big. But, on a particular phase condition, it was confirmed that the bending strain to occur in disconnectors might grow big conspicuously. As for this, the possibility is thought about by influence of higher natural frequency doing superposition. [ABSTRACT FROM AUTHOR]

SUMMARY In the disconnecting switch of 300 kV or less single pole structure, the Great East Japan Earthquake received much damage at the former by the rotation insulator base metal which damage experience had. Conventionally, we carried out a simple desk evaluation about earthquake-proof evaluation of insulator base metal. However, there is deviation with the damage actual condition and it became clear that it was an apparatus weak point part. Then, we worked on the analysis accuracy improvement of insulator base metal, and we built the analysis technology of the single pole structured disconnecting switch. [ABSTRACT FROM AUTHOR]

SUMMARY It is desirable that the number of forward contracts traded on the Japan Electric Power Exchange increase. However, few studies have clarified what factors have contributed to impacting the number of forward contracts traded. In this study, the authors analyzed the number of forward contracts using four count regression models. The negative binomial regression model and the zero-inflated models were better able to express the expected counts, by incorporating the overdispersion and excess zeros present in the observed data. Among others, the spot market can carry positive influences on the expected counts, by about 12% for a 1 yen/kWh increase in price, and by about 27% for a 0.1%-point increase in volumes. The zero-inflated models revealed that as many as three-fourth of the entire forward products have a high probability of zero counts, while the remaining one-fourth may see an increased number of counts as the spot market price and/or the spot volume becomes higher. [ABSTRACT FROM AUTHOR]

SUMMARY The 2011 Tohoku earthquake had a great impact on Japanese energy policy. It is expected that nuclear power plants will be phased out and a large amount of generation from renewable energy sources will be installed. Attention is particularly focused on photovoltaic (PV) generation, technology in which Japan is superior, and a high price is set in the feed-in tariff policy, which started in 2012. However, large integration of PV into power grids may cause imbalances between power supply and demand. It will be indispensable to use PV power generation forecasts in economic-load dispatching control (EDC), so that the economics and reliability of power systems networks can be maintained. Thus, in the previous study, we proposed an EDC method with unit commitment (UC) based on the results provided by a day-ahead PV forecast. In this study, we evaluate the frequency and trend of shortfalls and surpluses of power due to error in forecasting PV power generation by numerical simulations using the power system model of the Kanto area in Japan. The results showed that shortfalls or surplus power occur not only due to overestimations or underestimations of PV power, but also due to the operating conditions of the power systems. [ABSTRACT FROM AUTHOR]