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Wireless power transfer (WPT) technology can completely isolate the equipment from the power supply, and has been widely used. However, the transmission efficiency of WPT system is optimal only as the transmitting coil was completely aligned with the receiving coil. But in practical applications, the mobile devices are all dynamic system, and perfectly alignment of the coils is a very demanding condition. In order to solve this problem, the paper proposed a coil position adaptive adjustment control scheme of WPT system with lateral misalignment or angular misalignment. Firstly, the relationship between transmission efficiency and lateral misalignment and angular misalignment was analyzed. And the research results show that if there is a lateral misalignment between the coils, the transmission efficiency can be optimized by adjusting the angular misalignment. Secondly, based on the hill climbing algorithm, a coil position adaptive adjustment control method was proposed. Finally, a coil position adaptive adjustment WPT system experimental platform was built, and the experimental researches are carried on. The results of the experiment show that as the transfer distance is 0.10 m and the lateral misalignment is 0.12 m, the transfer efficiency can be increased from 38.38% to 55.61% through the proposed control scheme. And the results verify the feasibility and effectiveness of control scheme proposed in the paper. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

One of the impacts of the Fukushima disaster was the shutdown of all nuclear power plants in Japan, reaching zero production in 2015. In response, the country started importing more fossil energy including coal, oil, and natural gas to fill the energy gap. However, this led to a significant increase in carbon emissions, hindering the efforts to reduce its carbon footprint. In the current situation, Japan is actively working to balance its energy requirements with environmental considerations, including the utilization of hydrogen fuel. Therefore, this paper aims to explore the feasibility and implications of using hydrogen power plants as a means to reduce emissions, and this analysis will be conducted using the energy modeling of the MARKAL-TIMES Japan framework. The hydrogen scenario (HS) is assumed with the extensive integration of hydrogen into the power generation sector, supported by a hydrogen import scheme. Additionally, this scenario will be compared with the Business as Usual (BAU) scenario. The results showed that the generation capacities of the BAU and HS scenarios have significantly different primary energy supplies. The BAU scenario is highly dependent on fossil fuels, while the HS scenario integrates hydrogen contribution along with an increase in renewable energy, reaching a peak contribution of 2,160 PJ in 2050. In the HS scenario, the target of reducing CO2 emissions by 80% is achieved through significant hydrogen penetration. By 2050, the total CO2 emissions are estimated to be 939 million tons for the BAU scenario and 261 million tons for the Hydrogen scenario. In addition, the contribution of hydrogen to electricity generation is expected to be 153 TWh, smaller than PV and wind power. [ABSTRACT FROM AUTHOR]

Aiming at the problem of unnecessary waste of power resources in the power system caused by the uncertainty of wind farm output, and then affecting the economics of the system. This paper proposes a power system scheduling model based on wind power output forecasting errors. In the forecasting stage, in view of the defect that the Fruit Fly Optimization Algorithm (FOA) is easy to fall into the local optimal value, an Adaptive Mutation Fruit Fly Optimization Algorithm (AMFOA) based on the flavor concentration variance is proposed. And then, the parameters of Extreme Learning Machine (ELM) are optimized by AMFOA to predict the wind power output. In the scheduling phase, a limit scenario is established based on the obtained prediction error to reduce the fluctuation of the wind farm output. When modeling, the influence of the prediction error is considered in the power balance equation, and it is constructed to maximize the probability of its establishment. And then, incorporate it into the objective function. Based on this, a scheduling model is established and solved by AMFOA. Finally, an example is used to verify the accuracy of the proposed forecasting model and the economics of the scheduling model. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Off‐line partial discharge (PD) diagnosis, which requires an additional power supply has been accepted as an essential step in ensuring the integrity of power cable systems during commissioning testing. Many types of energizing voltage sources (e.g., alternating current resonance, damped alternating current, very low frequency [VLF] sine, and VLF‐cosine rectangular) have been developed, which are used in practice. However, choosing the optimal energizing voltage waveforms for PD testing is still controversial because their capability to motivate PD activities is still unclear. Accordingly, this paper compares the PD ignition capacity of the aforementioned power sources on six well‐designed PD defects in real cable joints. The influence of test voltage frequencies and waveforms are verified. The results show that the PD inception voltage and PD magnitudes in the cable joint defects do not change significantly as a function of the sinusoidal voltage frequency and the VLF‐cosine rectangular voltage exhibits excellent PD ignition capability with a low PD inception voltage and large PD magnitude. Moreover, the dynamic behavior of space charge in a PD defect caused by a gap is analyzed in order to explain the obtained results. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The traditional 25KV electric railways have various problems such as power quality issues, passing neutral sections, complex storage, and utilization of regenerative braking energy, the medium‐voltage direct current (MVDC) traction power supply system (TPSS) may be a potential alternative electric railway mode and can be freely accessed to the renewable energy and energy storage systems, which is an important development direction of the future low‐carbon RES. This paper first describes the structure and characteristics of the current Railway Electrification System (RES), and then analyzes and summarizes the current research status of the MVDC TPSS topology structure, modeling method, stability criterion, and analysis method and coordination control strategy. Finally, combined with the research status, the development direction of the MVDC TPSS has prospected. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Brushless doubly‐fed air‐core pulse alternator (BDAPA) is a new type of pulse alternator. It does not need a brush and slip ring, improving the reliability of the system. Moreover, the field winding and rotor winding have good compensation effect, which can significantly improve the discharge performance of the pulse alternator. As a high‐power pulse power supply, BDAPA must have a set of corresponding excitation power supplies to control its excitation. Pulse alternator and excitation power supply constitute the pulse alternator power supply system. The excitation power supply of pulse alternator usually adopts a pulse capacitor, the field winding of pulse alternator is excited by the pre‐charged capacitor before the pulse alternator discharges the load. After discharging, the excitation capacitor must be charged again before the next work of pulse alternator. This requires an additional set of DC power supply to charge the excitation capacitor. It not only increases the volume of the whole system and reduces the energy storage density of the system, but also makes the control of the system more complex. Taking the BDAPA as the research object, this paper proposes a control method with energy feedback, which is combining self‐excitation and separate excitation. Using the inertial energy storage of the pulse alternator and the inductive energy storage of the field winding and rotor winding, the excitation capacitor can be recharged through proper control methods, which can save the DC excitation power supply and improve the energy storage density of the system. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The rapid growth of distributed energy resources integrated in distribution systems leads to an increasing need of continuously and automatically changing the system topology to realize the economic operation of distribution networks. This paper proposes an optimization model of dynamic reconfiguration for distribution networks based on a new method of time series analysis. Equivalent daily curve considering time‐varying nature of distributed generator and load demands is divided by an improved fuzzy C‐means clustering algorithm, where the indicator of section function is set to find the optimal reconfiguration time intervals. The uncertainty of distributed generator outputs and load demands is described by the interval algorithm. Then the affine Taylor expansion is adopted to solve the interval power flow equations. The reconfiguration optimization model is solved with decimal particle swarm optimization algorithm based on loop search. The optimal dynamic reconfiguration of a modified 70‐bus test system with distributed generators is carried out and the simulation results demonstrate the effectiveness and superiority of the proposed method. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Switching power supply is widely used in industrial equipment, household appliances, and other fields due to the advantages of high integration and lightweight. Voltage sags can seriously affect the output voltage of switching power supply and the working condition of its power supply equipment; at the same time, the working scenarios of power equipment using switching power supply often have different level of harmonic problems. Considering the continuous innovation of switching power supply technology, the previous analysis and test results on the effect of voltage sags and harmonics on switching power supplies may no longer be applicable. The paper reveals the mechanism of the effect of harmonic alone as well as voltage sag superimposed harmonics on the output voltage of the switching power supply. Then the test research program was developed, and four different brands switching power supplies were selected for the test research, with which the effects of different amplitude voltage sags, harmonics with different frequencies and distortion, as well as voltage sag superimposed harmonics on the output voltage of switching power supplies were investigated. The results show that the tolerance ability of switching power supplies to voltage sags has been improved compared with previous switching power supplies, and the harmonic itself has less effect on the output voltage of switching power supply, but the joint action of harmonics and voltage sags will have a greater effect on the output voltage of switching power supply. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Electricity, as a sustainable energy carrier, plays a central role in the transition scenarios for carbon neutralization of energy systems. Expanding the potential of electricity requires intelligent integration of electricity infrastructures and electricity markets with distributed energy resources (DERs) including roof‐top solar photovoltaics (PVs), controllable loads, and storage batteries. This integration will advance the management of power distribution grids, resulting in harmonization of the distribution grids and variable renewable generation. In the foreseeable future, the DERs will be actively used to perform advanced management of power distribution grids and compensate fluctuation in variable renewable power generation such as PVs and wind power. Market‐based coordination mechanisms are already practiced in large‐scale electricity production, electricity trading and transmission around the world. Using these mechanisms at the distribution grid level to integrate numerous flexible devices into the grids remains an important research topic. This paper reviews the role of DER integration toward carbon‐neutral power systems, the state‐of‐art and challenges associated with market‐based approaches for integrating flexible demand, distributed generation, and storage. Methods for assessing the value of DER aggregation such as virtual power plants and microgrids are also explored. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Solar PV enables the conversion of solar energy into electricity and has become a clean energy technology for economic development. The advantages and disadvantages of solar photovoltaic vary among CPTPP member nations; nevertheless, since the CPTPP's implementation, fewer researchers have evaluated the member countries' solar photovoltaic goods' level of international competitiveness. In order to correct the flaw that the RCA index can only be studied from trade volume, this study adopts the IRCA index method and the revised CMS model, which integrates a number of variables to analyze the competitiveness of solar photovoltaic in each country. The study's findings indicate that: (1) the structural effect has a significant impact on export growth, particularly during the epidemic period, when Australia's contribution rate reached 106.58%; (2) the competitiveness effect has a lesser impact on export growth, and the epidemic led to a decline in competitiveness, with Japan's contribution rate reaching -262.85%; (3) the second-order effect has a declining trend in its contribution rate of export growth; (4) the export competitiveness of solar PV products differs between CPTPP countries, with power supply products having the most export competitiveness and solar cells having a steady comparative advantage in a weaker state. Apart than Japan, the remaining nations' comparative advantages for PV products are less than 1. Based on the above research findings, this paper puts forward the corresponding policy recommendations. [ABSTRACT FROM AUTHOR]

This paper intends to derive a detailed representation and attain a suitable computation method for the traction network. The transient analysis of the lossy multiconductor transmission lines (MTLs) is performed considering the electromagnetic characteristics of the rail track, which accounts for the frequency‐dependent and distributed nature of the line parameters over the entire frequency range for the traction network. Due to the practical difficulty in wideband parameter determination and the complex layout for the traction power supply system, the model implemented has been validated by comparison to several field tests that are carried out on a real high speed railway line for the purpose of identifying possible power quality problem. The good high representation of the frequency‐dependent parameter and the numerical solution will provide a reliable method for the transient analysis of the electrified railway. Afterwards, the transient calculation using vector fitting and modal decomposition is presented to evaluate how the emission is propagating along the MTLs of the electrified railways. Performing detailed and suitable analysis is necessary to determine the overvoltage conditions during the transients. The outcome of the analysis could be beneficial for the transient protection study in the electrified railway system. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper deals with load extrapolation methods and algorithms for the estimation of the energy efficiency of induction motors, starting from the electrical data generally available after parameter identification. The main aim of this paper is to help the readers move from the theoretical analysis to the experimental verification, which is suitable to be included in its own testing. For this reason, step‐by‐step algorithms are included in this paper. The first part deals with the determination of energy efficiency based on an original load extrapolation. Finally, experimental verification of the high‐power and high‐voltage induction motors is provided. Comparison between the values of the in–out method and load extrapolation method confirms the validity of the proposed algorithms. Compared to the direct in–out method, the error of the load extrapolation proposed in this paper is less than 1%.The load extrapolation method is mainly used for the high‐voltage and high‐power asynchronous motor. The high‐voltage and high‐power motor can be used to drive a low‐power motor to achieve coaxial twin trawling in the absence of a suitable power supply and matched load. The energy efficiency of a high‐power motor under different loads are measured and estimated using a mathematical fitting method. The estimated energy efficiency curves in the whole load range can be used to evaluate the high‐power and high‐voltage induction motor. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper proposes a control method for step voltage regulators (SVRs) to avoid voltage violations in distribution systems with unbalanced voltages due to photovoltaic (PV) generation and electric vehicle (EV) charging. Distribution system operators must effectively address voltage problems resulting from the widespread installation of distributed energy resources under the optimizing the utilization of existing voltage regulators to establish an efficient and rational infrastructure. Therefore, this study focused on advancements in voltage control using SVR based on line‐drop compensator (LDC) control, which is widely used in actual operations. We propose a method that utilizes voltage data from information technology switches to detect and address voltage unbalances in the control section, allowing for the sequential adjustment of the monitoring target in LDC control to maintain appropriate voltage limits under unbalanced conditions. We conducted power flow calculations using a distribution system model that represents an actual distribution system in the Hokuriku area. The effectiveness of the proposed method was evaluated in terms of its impact on PV and EV hosting capacity, as well as the frequency of tap operations. © 2023 The Authors. IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The rapid growth of electricity demands for recent years leads to many global concerns, including greenhouse, energy risk, and large size brownouts, which require modern energy management system to provide environmental‐friendly power supply service with less cost and higher reliability. However, most of previous studies separately focus on improving prediction accuracy or reducing cost and emission of power supply solution by dispatch optimization. To exploit the benefits of microgrid system furthermore, this paper firstly proposes a comprehensive day‐ahead multi‐objective microgrid optimization framework that combines forecasting technology, demand side management (DSM) with economic and environmental dispatch (EED) together. Then, two versions of particle swarm optimization are implemented for obtaining load control plan from DSM model and power supply plan from EED model, respectively. Moreover, two different microgrids' applied scenarios are simulated with detailed sensitivities analysis on key parameters. Experiment results demonstrate effectiveness of the proposed framework, which can obtain load demands profile with better reliability, as well as power supply solution with less cost and lower emission. Meanwhile, beneficial decision supports are provided to manager for their references. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In order to fill the blank of practical engineering application of inductive control in ozonizer power supply, this paper probes into a scheme of high frequency and high voltage inverter for the control, and analyses operation modes to form a reasonable theoretical result, and introduces a new current zero crossing and phase locking method to adjust the address deviation and ensure that the address pointer directs to the last value of inverter current by changing the sampling period and adjusting the error of practical reference address pointer at each zero crossing point. The results from theoretical derivation, numerical simulation, and power experiment prove that the scheme can suppress the current spike caused by diode reverse recovery and reduce the power loss of switch devices, which is conducive to cost reduction. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The problem of shafting torsional vibrations has been increasingly emerging due to the increasing capacity of turbo‐generator and the complexity of power grid. Therefore, how to reduce the torsional vibration of the turbo‐generator shaft and improve the stability of the power system has become the focus of our research. First, in order to solve the problem and alleviate the torsional vibrations of turbo‐generator shafts, this paper proposed a new shafting structure model of Double‐ended Driving and Dual‐Excited Turbo‐Generator set (DDDETG). A static excitation mode is used for the excitation of the DDDETG and the mechanical power is supplied symmetrically and synchronously from both ends of the generator rotor. Then, in order to improve the output characteristic of the generator and further suppress the torsional vibrations of the turbo‐generator shafts, combined with the nonlinear control design method of partial feedback linearization, a Multi‐Index Nonlinear Coordinated Control (MINCC) strategy for the double‐ended driving and dual‐excited turbo‐generator is proposed to ensure good dynamic and static state performances of each state in the system. Finally, the simulation results on a single‐machine infinite bus system demonstrate the effectiveness of the proposed control strategy. In addition, this paper compares the performance of DDDETG and the traditional Single‐ended Drive and Single‐Excited Turbo Generator (SDSETG), the simulation results show that the restraint effect of the DDDETG structure on shafting torsional vibrations is more obvious under the proposed control strategy. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Offshore wind power attracts intensive attention for decarbonizing power supply in Japan, because Japan has 1600 GW of offshore wind potential in contrast with 300 GW of onshore wind. Offshore wind availability in Japan, however, is significantly constrained by seacoast geography where very deep ocean is close to its coastal line, and eventually, nearly 80% of offshore wind resource is found in an ocean depth deeper than 50 m. Therefore, power system planning should consider both the location of available offshore wind resource and the constraint of power grid integration. This paper analyzes the impact of power grid integration of renewable resources including offshore wind power by considering the detailed location of offshore wind resource and the detailed topology of power grid. The study is performed by an optimal power generation mix model, highlighted by detailed spatial resolution derived from 383 nodes and 472 bulk power transmission lines with hourly temporal resolution through a year. The model identifies the optimal integration of power generation from variable renewables, including offshore wind, given those predetermined capacities. The results imply that, together with extensive solar PV integration, total 33 GW of offshore wind, composed of 20 GW of fixed foundation offshore wind and 13 GW of floating offshore wind could contribute to achieve 50% of renewable penetration in the power supply of Japan, and that scale of offshore wind integration provides a technically feasible picture of large-scale renewable integration in the Japanese power sector. [ABSTRACT FROM AUTHOR]

This paper presents a low‐power self‐contained overvoltage detector. Compared with conventional detectors that consist of stacked Zener diodes, the proposed structure can trim the threshold with binary codes to accommodate system‐level changes. The proposed structure enables trimming by adding a decoder, a biasing circuit, and switches in parallel with Zener diodes. The newly configured structure forms a standalone detector that can operate independently and be powered from the supply under detection with negligible current addition. The proposed structure is applicable to any high‐voltage process that contains N‐type isolation layer and needs no high‐voltage device. The proposed circuit with three bits adjustment circuit was fabricated in a 0.18 μm Bipolar‐CMOS‐DMOS (BCD) process, the overvoltage threshold can be adjusted from 8 to 38 V with post trim variation of ±2.5 V. The measured quiescent current was around 0 μA at 10 V and 28 μA at 38 V, which was comparable to the current consumption in a conventional structure with 38 V overvoltage threshold. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In Japan, the Goal of Carbon Neutral in 2050 was declared by Prime Minister in October, 2020. In order to achieve the goal, the Japanese government positioned Renewable Energy Source (RES) such as PV and wind power as 'main power supply resource' and is expanding its introduction by taking various types of countermeasures to solve the problems induced by massive integration of the RES into the grid. In recent years, the power system was damaged many times by a lot of natural disaster such as strong earthquakes, typhoons and heavy rains. The situation of the Japanese power system is drastically changing due to low demand growth, massive introduction of the RES as well as evolution of the power system reform that is introduction of power markets such as energy spot market, capacity market and balancing market. In this paper, our activities toward deregulated, smart and resilient power systems are presented. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

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In order to reduce the torsional vibration of the turbo‐generator shaft and improve the stability of the power system, this paper proposed a more stable shafting structure model of Double ended Driving Turbo‐Generator (DDTG) by improving the shafting structure of conventional turbo‐generator set. For DDTG, the mechanical power is supplied symmetrically and synchronously from both ends of the generator. Compared with the conventional Single ended Driving Turbo‐Generator (SDTG), simulation results verify the effectiveness of the proposed shafting structure model, and indicate that DDTG can effectively reduce the torsional vibration of turbo‐generator shafts under the same electrical disturbance. Besides, in order to further suppress the torsional vibration of turbo‐generator shafts and improve the system performance, based on the nonlinear control method with objective holographic feedback, a Coordinated Control law of Excitation and Steam‐Valve (CCESV) is proposed. Under the action of CCESV, the simulation results show that the restraint effect of the DDTG on shafting torsional vibration is more obvious, and the dynamic and static performance of the system can be effectively improved. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Power transformer rooms have been gradually installed in residential buildings due to an increasing demand for power supply and space requirement. However, the noise generated by transformers during operation has become a hot topic of complaints. In order to solve the problem of transformer noise pollution and explore the rules of noise for power transformer rooms, a portable noise monitoring system consisting sensor array and a vibration and noise tester is developed in this paper. The noise characteristics of a power transformer room in Guangzhou city are obtained through field tests, which include the time‐domain characteristics, spectrum characteristics, and A‐weighted sound level characteristics. Results show that the frequency component of noises is stable, but the amplitude varies. The sound pressure of the power transformer room has obvious periodicity and the amplitude is 0.1–0.2 Pa. The dominant noise frequency is fixed at 300 Hz. According to different positions, the A‐weighted sound level is distributed between 55 and 65 dB. The research is not only of great help to formulate transformer noise assessment methods, but also of great significance to improve people's living environment and ensure power system's reliable operation. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

At reconnaissance to feasibility study stages of wave energy development, guidelines and standards recommend wave power assessments to be conducted for long periods of time, albeit at relatively coarse spatial resolutions. However, quite often developers need to make a preliminary site selection based on high-resolution information. Unfortunately, even with abundant computational resources nowadays, running a high-resolution coastal model for more than a decade is still not practical. In this paper, we propose to combine uncertainty estimates from a 21-year-long 1-km-resolution model and a high-resolution (10 m nearshore) coastal model to assess wave energy. Two sites in Japan facing the Pacific Ocean were selected for this study. One site located on the southern coast (site-S) is affected more by the passage of typhoons than another site located on the eastern coast (site-E). The estimated wave power climatology at site-S ranges between 3 and 7 kW m - 1 with an uncertainty of ± 0.27 to ± 0.51 kW m - 1 ; whereas for site-E, the climatology varies between 3 and 9 kW m - 1 with uncertainties of ± 0.12 to ± 0.34 kW m - 1 . In general, the eastern coastal area of Japan is found to offer higher wave power and lower margins of uncertainty than compared with the southern coastal area. [ABSTRACT FROM AUTHOR]

A novel low‐power, tuneable resolution and low‐current sensing analog‐to‐digital converter is proposed in this paper. The proposed architecture consists of silicon neurons along with digital circuits. The architecture is tuned for input signal ranging from 100 nA to 3.3 μA with power supply of 1 V/3.3 V for digital blocks and silicon neurons respectively. The design is simulated using 0.18 μm CMOS 1P4M triple well process of Tower Jazz Semiconductor's technology. Total power consumption of the circuit is 98.8 μW and achieves FoM of 14.74 pJ/Conv for 8‐bits of operation. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this paper, the authors present a two-step model to obtain quasi-optimal solutions for the storage and transportation of renewable energy as its installation becomes more widespread in remote areas. The model is formulated as a total cost minimization linear programming problem and considers both renewable energy facilities and the energy supply and demand of the entire country. The first step of the model optimizes the entire country, while the second step determines the marginal capacity of energy storage and transportation facilities when the excess production capacity of remote renewable energy is added. This approximation for reducing computational complexity is shown to be sufficiently accurate under realistic conditions. The authors apply the model to analyze energy storage and hydrogen production at renewable energy power plants in Japan in 2050. The study shows that photovoltaic power generation uses storage batteries attached to the power plant for electricity transmission. In contrast, wind power generation transmits most electricity directly without storage batteries and converts some into hydrogen for consumers. The proposed lightweight model allows for numeral sensitivity analyses, which provide valuable insight into optimizing energy storage and transport of renewable energy. • We developed a 2-step model for quasi-optimization of equipment at VRE site. • This model optimizes energy storage and transport with VRE deployment. • If additional VRE is sufficiently small, the model division retains sufficient accuracy. • Energy supply costs minimized by combining power transmission and H 2 transportation. • PV has large LIB, while WT has direct transmission and H 2 production. [ABSTRACT FROM AUTHOR]

In recent years, the design of new electronic equipment requires the development of new topologies for power supplies. The above is clear for portable equipment, which many times is classified as light loads. These new applications require power supplies with wide conversion ratios and better efficiencies. A solution to this problem is the use of two or more conventional converters connected in cascade, which have been proposed to operate in continuous conduction mode; however, if these converters operate in discontinuous conduction mode (DCM) a better efficiency is achieved. In this paper, a cascade connection based on two boost converters operating in DCM is proposed. A step‐by‐step procedure for the proper design of the cascade connection is given. Simulation and experimental results for a low power converter validate the proposed methodology. Thus, the design procedure will help in designing converters for light power applications. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

After the Great East Japan Earthquake, energy security and vulnerability have become critical issues facing the Japanese energy system. The integration of renewable energy sources to meet specific regional energy demand is a promising scenario to overcome these challenges. To this aim, this paper proposes a novel hydrogen-based hybrid renewable energy system (HRES), in which hydrogen fuel can be produced using both the methods of solar electrolysis and supercritical water gasification (SCWG) of biomass feedstock. The produced hydrogen is considered to function as an energy storage medium by storing renewable energy until the fuel cell converts it to electricity. The proposed HRES is used to meet the electricity demand load requirements for a typical household in a selected residential area located in Shinchi-machi in Fukuoka prefecture, Japan. The techno-economic assessment of deploying the proposed systems was conducted, using an integrated simulation-optimization modeling framework, considering two scenarios: (1) minimization of the total cost of the system in an off-grid mode and (2) maximization of the total profit obtained from using renewable electricity and selling surplus solar electricity to the grid, considering the feed-in-tariff (FiT) scheme in a grid-tied mode. As indicated by the model results, the proposed HRES can generate about 47.3 MWh of electricity in all scenarios, which is needed to meet the external load requirement in the selected study area. The levelized cost of energy (LCOE) of the system in scenarios 1 and 2 was estimated at 55.92 JPY/kWh and 56.47 JPY/kWh, respectively. [ABSTRACT FROM AUTHOR]

Certain applications of power electronics for railway vehicle traction systems and fixed installations are reviewed and future possibilities considering technical and social trends around railway industry are mentioned in this paper. First of all, some particularities of railway load and traction power supply system are summarized as problems to be solved by power electronics technologies. Such technologies for fixed installations and vehicle traction systems are presented and future possibilities for higher performance, minimization, and improved resilience of railway system are pointed out. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to provide empirical estimates of total factor productivity (TFP) growth rates in the electric power industry for the United States, Japan, and Korea. In this paper, the conventional Divisia index number approach and two cost function approaches are used to assess TFP growth rates during the 1972-1996 period. The TFP growth rates in the United States, where regulatory reform has been progressing gradually since 1978, did not show much difference from those in Japan, and were considerably lower than those achieved by Korea, where little reform has taken place. Decomposition analysis based on the total cost function shows that the major sources of TFP growth were the scale effect in Japan, the capacity utilization effect and the scale effect in Korea, and technical change in the United States. Since the mid-80s, the increases in TFP growth were due to improvements in the capacity utilization effect in all three countries. [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]

Methane hydrate is expected as domestic energy resources in near future in Japan. Especially the shallow-type methane hydrate and the associated methane plume are regarded as sustainable energy resources. In this paper, the investigation of the methane hydrate particle motion in the methane is presented. A quantitative analysis of the motions of the ascending methane hydrate particles seeping from the seafloor and reproduced by the numerical simulation is performed by the two-dimensional motion analysis technique and the behavior is discussed in detail. [ABSTRACT FROM AUTHOR]

Following the theory and method of the 'same‐phase power supply scheme', as declared in United States and Taiwan patents, a novel power supply method is proposed to reduce damage to users when the supply power is in shortage. This paper proposes using the equivalent model function blocks, as built by MATLAB/Simulink, for simulations of the probable line‐to‐line and single line‐to‐ground faults in a distribution system when the power supply mode is switched from 'normal' to 'same‐phase'. The simulation results prove that, when the power supply is switched to the 'same‐phase' power supply mode, all the short‐circuit fault currents are a little lower than that in the 'normal' power supply mode, and the maximum difference is less than 3%. Therefore, when the supplying power of the system is in shortage or the power distribution system has a short‐circuit fault between phase lines, the system can be directly switched to the 'same‐phase' power supply mode and can continue supplying power to the essential and basic loads for life‐support and people's livelihoods. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper details the efforts made by Institute for Global Environmental Strategies (IGES) and The Energy and Resources Institute (TERI), under their Japan-India collaborative projects, to promote low carbon technologies (LCT) among small and medium enterprises (SMEs) in India. The empirical evidence gathered during the projects show that three key barriers hinder faster adoption of Japanese LCT among the Indian SMEs: (i) information and knowledge gaps; (ii) networking and communication challenges; (iii) higher cost of the LCT. To bring stakeholders from the two countries together, a multi-stakeholder platform called Japan-India Technology Matchmaking Platform (JITMAP) was developed. The paper outlines how JITMAP, through its online information sharing and on the ground activities, is addressing some of the barriers by promoting awareness enhancement, arrangement of business meetings, study on LCT application (feasibility studies), access to financial schemes, and arrangement of policy and regulatory discussions. There is ample scope to scale-up the JITMAP activities and replicate it as a model for LCT cooperation between other developed and developing countries. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive life-cycle analysis of CO2 (LCCO2) emissions from automobiles using a hybrid life-cycle inventory approach to predict the growth of electrified vehicles in Japan. Herein, the hybrid electric vehicle (HEV), plug-in HEV (PHEV), and battery electric vehicle (BEV) versions of the massproduced Toyota Prius hatchback are analyzed, considering the automobile-usage environment in Japan. In particular, a breakeven analysis of HEV vs. PHEV vs. BEV is conducted in terms of LCCO2 emissions that are affected by (i) outside air temperature and (ii) CO2 emissions during power generation from the present day up to 2030. Our results show that HEV has the lowest LCCO2 emissions when the current thermal-power-dependent electricity generation mix (average for 2012-2014) is considered, followed in order by PHEV and BEV. However, it is predicted that in 2030, PHEV will have the lowest LCCO2 emissions, followed in order by HEV and BEV, as it is anticipated that nuclear and renewable energy sources will be widely available by 2030. PHEV is expected to gain popularity by 2030. Regarding BEV, large quantities of CO2 emissions are emitted during battery production. Furthermore, due to the domestic electricity generation mix from the present day up to 2030, the LCCO2 emissions of BEV will exceed those of HEV and PHEV. [ABSTRACT FROM AUTHOR]

In 2006, the first Lithium-ion battery in Japan was installed in traction power supply system by the West Japan Railway Company and now more than 20 energy storage systems have already been installed in traction power supply system in Japan. In this article, the recent Japanese trends of regenerative energy utilization are summarized not only in DC railway but also in AC railway. We, East Japan Railway Company, have installed three energy storage systems for DC railway and one railway static power conditioner (RPC), not energy storage system, for AC railway for regenerative energy utilization. The effects of these systems are also shown quantitatively in this paper. [ABSTRACT FROM AUTHOR]

In this article, we measure the energy efficiency of 17 sectors in the Japanese economy during 1998–2005 using data envelopment analysis (DEA), in which a total-factor framework is applied. We compute the total-factor energy efficiency, which is defined as the ratio of the target energy input suggested by the DEA to the actual energy inputs in a sector. Energy, labor, and capital are the three inputs, while the value added in each sector is the single output. Our major finding is that remarkably energy-inefficient sectors in the Japanese economy include energy-intensive industries (i.e., pulp and paper, chemical, cement and ceramics, and primary metal sectors) as well as agriculture, forestry and fishery, transportation and communication, and miscellaneous manufacturing. There is much room to improve energy efficiency in Japanese industrial sectors. Moreover, for 8 sectors, including energy-intensive industries, the inefficiency of energy use is much worse than that of other resource usage. [ABSTRACT FROM AUTHOR]

This paper is based on a localized case study of teaching Sino-Japanese energy issues in the area studies setting of Japanese studies through a historical perspective. It is based on the author's four semesters of teaching at Chinese University of Hong Kong, the complexities of which are increased by the 11 March 2011 Great East Japan Earthquake and the resulting discussions of energy issues in Northeast Asia. Five sub-topics related to energy are discussed here: energy transitions; history of energy fuel use in Northeast Asia; the scarcity of fossil fuels in the region; competition and cooperation for energy resources; and the potential and possibility of non-fossil fuel replacement resources. These five sub-topics are collectively discussed and contextualized in the post-311 or post-Great East Japan Earthquake scenario. The methodology used in analyzing the content approach to covering these topics and making them accessible to students fall into three main areas: the use of historiography to cover the major arguments, concepts and scholarly arguments/schools of thought in teaching these sub-topics; techniques in constructing historical overviews to make these topics accessible to area studies students and constructing literature reviews to stimulate student discussions on post-311 energy scenarios in Northeast Asia within the contextualized of the globalized energy industry and relations. Limitations of these approaches will be discussed through observation techniques. Textual analysis of textbooks covering these topics will also be analyzed based on the author's bibliographic use in constructing the course materials for the above subject areas. Finally, some concluding trends, remarks and observations as well as implications of the above teaching experience are covered in the concluding section. [ABSTRACT FROM AUTHOR]

In array antennas, sometimes the desired radiation pattern cannot be obtained due to coupling between element antennas, reflections from the surroundings, or amplitude and phase error of the power supply circuits or failures. In these cases, it is necessary to regenerate the desired radiation pattern by estimating the excitation amplitude and phase of the array antennas. Among methods of estimation of the excitation amplitude and phase, the rotation element field vector method of element antennas is used for the phased array antenna with variable phase shifters, and the planar near-field measurement method is used for the array antennas with no variable phase shifters. The former is limited to phased array antennas, and the latter requires a large-scale scanner for the measurement and results in increased measurement time with larger-scale array antennas. In this paper, we propose a method of estimation of excitation amplitude and phase using the radiation pattern of array element antennas and the measured radiation pattern of the array antennas. Two methods are proposed here; the first method of estimation is the least-squares method using the electrical field as the measured radiation pattern, and the second is the repeating calculation method using the electrical power as the measured radiation pattern. We describe here the principle and experimental results when the first method is used, and the principle and the effectiveness of selection of the initial value for the second method is confirmed by numerical results. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(9): 102–110, 2000 [ABSTRACT FROM AUTHOR]

In this paper, the significance of CO 2 -free hydrogen is discussed using a long-term global energy system. The energy demand–supply system including CO 2 -free hydrogen was assumed, though there are still large uncertainties as to whether a global CO 2 -free hydrogen energy system will be deployed. System analysis was conducted using the global and long-term intertemporal optimization energy model GRAPE under severe CO 2 emission constraints. Applied global CO 2 constraints for 2050 were a 50% reduction from 1990 levels. CO 2 constraints accounting for Intended Nationally Determined Contributions (INDCs) in each region were also considered. A variety of energy resources and technologies were considered in this model. Hydrogen can be produced from low-grade coal or natural gas with CO 2 capture and electricity from renewable energy. The hydrogen CIF (cost, insurance, and freight) price for Japan was about 3.2 cents/MJ in 2030. Hydrogen demand technologies considered in this paper are hydrogen-fired power plants, direct combustion, combined heat and power (fuel cells, gas engines, and gas turbines), fuel cell vehicles, and hydrogen internal combustion engine vehicles. The majority of CO 2 -free hydrogen was deployed in the transportation sector. CO 2 -free hydrogen was utilized in the power sector, where deployment of other zero emission technology has some constraints. From an economic viewpoint, CO 2 -free hydrogen can reduce the global energy system cost. From the viewpoint of a localized region, such as Japan, deployment of CO 2 -free hydrogen can improve energy security and environmental indicators. [ABSTRACT FROM AUTHOR]

To cope with the high rate of increase of power demand in the main industrialized districts in Japan, 550-Kv transmission systems covering the distrits have been reinforced, with most of the main power plants connected directy tro these systems.Throught 550-/300-kV substations, the majority of power to the districts is supplied by 300-+kV systems. To limit the excess short-circuit capacity in the 300-*kV systems, they tend to be reconstructed as so-called radia; networks. in radial networks with high short-circuit capacity and relatively small number of transmission lines connected to the substation busbars, the rate of rise of TRV can be far higher than standard value. This paper analyzes the transient recovery. this paper analyzes the transient recovery voltages (TRV) in such extra-high-voltage radial networks in Japan, together with the relevant stress to circuit-breakers during clearing. future system conditions have also beeen introduced. As the typical rate of rise of the TRV values, more than twice that of today's standard ones are probable. [ABSTRACT FROM AUTHOR]

To reduce CO2 emissions in the residential and transportation sectors, distributed energy technologies, such as photovoltaic power generation (PV), stationary storage batteries (SBs), battery electric vehicles (BEVs), and vehicle-to-home (V2H) systems, are expected to be introduced. The objective of this study was to analyze the impact of the installed capacity of PV and SB, the type of vehicle, and their combination on the economic and environmental performance of the total energy consumption of residences and vehicles. Thus, this study developed a model to optimize the technological configuration of residential energy systems, including various vehicle types and driving patterns. The simulation results showed that it is more economically and environmentally efficient to install a BEV and a V2H system in households with longer parking times at the residence and to install an SB in addition to these technologies in households with shorter parking times at the residence. Furthermore, comparing a gasoline vehicle and an SB, the most economical combination, with a BEV and a V2H system and with a BEV, a V2H system, and an SB, estimated the carbon tax rate necessary for cost equivalence. The result indicated that the carbon tax rate needs to be increased from its current level. [ABSTRACT FROM AUTHOR]

The growing demand for electricity, driven by factors such as the shift to carbon neutrality and economic growth, is a challenge shared by South Korea and Japan. South Korea, a peninsula nation, and Japan, an island country, which are both heavily dependent on foreign energy sources and have manufacturing-based industrial structures, are actively working to secure stable power supplies for their economic development. This article carries out a quantitative analysis of the roles of the South Korean and Japanese electric power sectors (EPSs) in their respective economies, seeking to identify differences and generate actionable insights for decision making and policy formulation. Utilizing the input–output (IO) technique with the latest available data, the analysis includes a demand-side model, a supply-side model, and a price-side model to examine various effects of the EPSs. The key findings reveal differences in the production-inducing, value-added creation, and job-creation effects between the two countries, highlighting operational disparities in their electricity sectors. Additionally, South Korea exhibits higher wage-inducing, supply shortage, and price-side effects than Japan, because of its public enterprise-oriented high-wage structure and a substantial manufacturing sector. These quantitative results provide valuable reference material for future government decisions and policy development in the EPS and emphasize the significant role and impact of the power sector in both countries. [ABSTRACT FROM AUTHOR]

The metro stray current leaked during the subway operation causes the nearby earth surface potential to change, so that the various neutral‐grounded transformers to be at different earth surface potentials, resulting transformer DC bias. In order to analyze the influence of metro stray current on transformer DC bias, the polarization potential monitoring data in metro traction power supply system and neutral point current of nearby transformer were compared, and the positive correlation characteristics between the two were pointed out. By studying the stray current leakage reason in the metro traction power supply system and the circulation path causing transformer DC bias, the mechanism of the transformer DC bias under the subway operating environment was revealed. Based on the discrete model of the stray current distribution, considering the mechanism of stray current on DC bias, the equivalent resistance model of the transformer DC bias caused by metro stray current was built with double‐end power supply environment. Then the calculation formula of transformer neutral point current changing with subway operating conditions was derived, the numerical calculation of DC bias current of transformer caused by metro stray current was realized. The validity of the proposed model was verified by current distribution, electromagnetic field, grounding and soil structure analysis, the simulation results showed that the proposed model can calculate the stray current distribution and the nearby transformer DC bias current with high accuracy, which provided a quantitative analysis method for studying the correlation between metro stray current and transformer DC bias phenomenon. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

SUMMARY Reducing the rates of nuclear power generation for all electric power sources has been seriously discussed in Japan since the accident at the Fukushima No. 1 nuclear power plant in March 2011. Thus, the distributed power supply is expected to expand. The local production of safe and clean energy for local consumption is greatly needed in Japan. In this paper, the Saroma Lake green microgrid (SLMG), a fuel cell microgrid using tidal power generation and photovoltaics, has been planned. Energy balance equations were used to investigate this system's method of operation. Further simulated analysis of the facility, its operation cost, and the electric power quality of the network were conducted using MATLAB/Simulink, and the relationships among the capacity of a facility, the cost, and supply rate of green energy and the electric power quality (interphase voltage, frequency, and higher harmonic wave) of the power network were clarified. The total projected cost of the equipment and operation for introducing the proposed SLMG is ¥1,500,000,000/10 years. Increasing the supply rate of green energy and reducing the facility cost will require the introduction of biofuels and the reduction of the facility costs of solid oxide fuel cells in the SLMG. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ground-based high voltage electrical line inspection is one of the difficult and highly dangerous job as far as a manual worker is concerned. The transmission line inspection by robots avoids temporary interruption of power supply that affects the end user and transmission grid. Also, robot-based inspection reduces maintenance cost and hazards. The electrical line inspection is normally carried out using binoculars and rarely by helicopters in most of the countries because of the low cost. Wire traversing or aerial robots are being used in Japan, Canada, USA and Russia for inspecting and monitoring faults in transmission lines and towers. However, most of these robots require a lot of human effort for installation due to its weight and complex design. Cost of these robots is also very high. This paper presents the mechanical design, fabrication and testing of a novel, low cost, light weight and compact power transmission line inspection robot. This work also includes kinematic, static and dynamic analysis of various subsystems of robot. Proposed robot is capable of traversing on straight transmission line and jumper cables present in tension towers. The robot has 10 DoF dual arm for crossing operation and a base system to achieve the locomotion. [ABSTRACT FROM AUTHOR]

Peer-to-peer (P2P) energy trading is gaining attention as a technology to effectively handle already existing distributed energy resources (DER). In order to manage a large number of DER, it is necessary to increase the number of P2P energy trading participants. For that, designing incentives for participants to engage in P2P energy trading is important. This paper describes a user-centric cooperative mechanism that enhances user participation in P2P energy trading. The key components of this incentive for participants to engage in P2P energy trading are described and evaluated in this study. The goal of the proposal is to make it possible to conduct economic transactions while reflecting the preferences of the traders in the ordering process, making it possible to conduct transactions with minimal effort. As a case study, the Higashi-Fuji demonstration experiment conducted in Japan verified the proposed mechanism. In this experiment, 19 households and 9 plugin hybrid vehicles (PHV) were evaluated. As a result, the study confirmed that prosumers were able to sell their surplus electricity, and consumers were able to preferentially purchase renewable energy when it was available. In addition, those trades were made economically. All trades were made automatically, and this efficiency allowed the users to continue using the P2P energy trading. [ABSTRACT FROM AUTHOR]