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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]

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: 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]

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]

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]

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]

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]

This paper proposes a new method for improving an existing abnormality detection system for a person who soaks in a bathtub. As the number of aged people increases year by year in Japan, bathing accidents among the aged are growing at a rapid rate, especially in-bathtub drowning accidents. Therefore, prompt detection of a bather's abnormality, such as dizziness and fainting, is important to prevent in-bathtub drowning. In order to detect a bather's abnormality promptly, an abnormality detection system using seven ultrasonic sensors has been proposed. The system uses two methods-posture detection and motion detection-to detect a difference in a bather's state compared to normal before an accident occurs, and improves the delay in detection considered heretofore to be a serious problem. There was, however, plenty of room for improvement. In order to improve the detection rate of the system, we propose a new detection method in this paper. The method uses two ultrasonic sensors to scan a bather's head and neck, and detects the head height and swing speed of the head. Experimental results are superior to the accuracy of the existing system, which enables us to detect an abnormality in a bather more precisely. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 57-67, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21133 [ABSTRACT FROM AUTHOR]

The National Metrology Institute of Japan (AIST, NMIJ) launched a project for the development of AC shunt standards. AC shunts allow the most precise measurement of current. A high-precision AC shunt is an important component of nonsinusoidal power standards. The AC shunt calibration system helps improve the uncertainty assessments of the national primary power standards. The calibration system design with uncertainties of up to 10 ppm requires a precise buffer amplifier which has uncertainties of up to 1 ppm in the frequency range from 10 Hz to 10 kHz, with other uncertainty components taken care of. The two buffer amplifiers dealt with in this paper were verified to have errors within 2 ppm and uncertainties within 1 ppm in in-phase and quadrature error in the frequency range from 10 Hz to 10 kHz. This also implies a possibility of reducing both in-phase and quadrature error at 10 kHz within 1 ppm, by taking advantage of both features. This paper describes the circuit design and evaluation results of two different buffer amplifiers. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 24-31, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21218 [ABSTRACT FROM AUTHOR]

For distribution lines in Japan, protection measures against lightning-induced overvoltages have been taken and can be considered almost complete. The focus of lightning protection measures has moved to overvoltages due to direct lightning strokes. Studies of such overvoltages require simulations using the EMTP (Electro-Magnetic Transients Program), and components of a distribution line must be modeled appropriately in the EMTP simulation environment. The authors have proposed an EMTP model of a distribution line in a separate paper. This paper consists of two parts. The first part presents surge characteristics of a distribution line obtained by measurement using an actual-scale test distribution line. In particular, the result reveals noteworthy characteristics of the surge impedance of a reinforced concrete pole and the wavefront-time dependence of insulator voltages. The second part presents a validation of the distribution line model previously proposed by the authors. The validation shows that the distribution line model accurately reproduces the measured voltage and current waveforms for various wavefront times of the injected currents. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 1–10, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.21002 [ABSTRACT FROM AUTHOR]

With the wholesale electric power market opened in April 2005, deregulation of the electric power industry in Japan has faced a new competitive environment. In the new environment, Independent Power Producer (IPP), Power Producer and Supplier (PPS), Load Service Entity (LSE), and electric utility can trade electric energy through both bilateral contracts and single-price auction at the electricity market. In general, the market clearing price (MCP) is largely changed by the amount of total load demand in the market. The influence may cause a price spike, and consequently the volatility of MCP will make LSEs and their customers face a risk of higher revenue and cost. DSM is attractive as a means of load leveling, and has an effect on decreasing MCP at peak load period. Introducing Energy Storage systems (ES) is one DSM in order to change demand profile at the customer side. In the case that customers decrease their own demand due to increased MCP, a bidding strategy of generating companies may be changed. As a result, MCP is changed through such complex mechanism. In this paper the authors evaluate MCP by multi-agent. It is considered that customer-side ES has an effect on MCP fluctuation. Through numerical examples, this paper evaluates the influence on MCP by controlling customer-side ES corresponding to variation of MCP. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 36–45, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20658 [ABSTRACT FROM AUTHOR]

District Heating and Cooling (DHC) combined with a Cogeneration System (CGS) is one of the most efficient ways to supply energy to the commercial and residential sectors. This paper discusses the feasibility of introducting DHC from the viewpoint of the overall energy saving effect in Japan's energy system as a whole. Although DHC is efficient for congested areas such as urban business centers, these areas are limited in capacity and number. In our evaluation of the feasibility of introducing DHC, we consider the energy demand density profiles of Japan's commercial and residential sectors in order to determine the installed DHC capacity that is optimal for meeting the growth of energy demand. This paper also discusses operating patterns of CGS and of boilers in DHC. In order to improve the efficiency of individual DHC facilities, CGS should be operated so as to satisfy heating demand, resulting in a low annual load factor. On the other hand, the overall efficiency of the energy system requires an improvement of the overall load factor of CGS, which is achievable by combined use of CGS and boilers. Operation of CGS in this manner improves the feasibility of the introduction of DHC. © 2000 Scripta Technica, Electr Eng Jpn, 133(2): 31–42, 2000 [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 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]

This paper deals with an advanced static Var compensator (ASVC) using quad-series voltage-source PAM inverters. The ASVC consists of four three-phase voltage-source inverters with a common dc capacitor and four three-phase transformers, each primary winding of which is connected in series with each other. Each inverter outputs a square-wave voltage, while the synthesized output voltage of the ASCVC has 24-step wave shape. This results not only in a great reduction of harmonic currents and dc voltage ripples but also in fewer switching and snubbing losses. In this paper, transient analysis is performed with the focus on the response pf reactive power and the resonance between the dc capacitor and ac reactors. Experimental results obtained from a small-rated laboratory model of 10 kVA are also shown to verify analytical results help in the design of system parameters such as the capacity of the dc capacitor and feedback gains. [ABSTRACT FROM AUTHOR]

The recent drastic increase in the number of air conditioners has caused sharp and narrow peaks in summer seasons due to the inherent temperature-sensitive characteristics. The authors proposed a method to reduce the peak power demand by controlling air conditioner operations, and verify its effectiveness on clipping peak demand. However, former study has shortcomings in that no qualitative treatment of room temperature or comfort was attempted, and it did not provide a way of assessing peak demand clipping in a power system as a whole. In this paper, the authors propose a new control method that can be deal with the maintaining of comfort and the reduction in power demand. Although air conditioners are used for ‘comfort’, this contradicts the reduction of power consumption and furthermore the concept of ‘comfort’ is very vague. Hence, Weber-Fechner's law is utilized to quantify the pleasant feeling which is treated as a fuzzy quantity. A fuzzy coordination method is used to resolve this difference between power demand curtailment and comfort. The second part of this paper prepares an approach for assessing the amount of peak load clipping when the newly proposed control strategy is adopted in a real-size power system. A decrease in the required generation capacity is estimated provided that the loss of load probability (LOLP) is maintained at the same level before and after the application of the new control strategy. The reduction can be regarded as a dividend of load management. [ABSTRACT FROM AUTHOR]

For lightweight and compact implementation of a generation set, many attempts have been made by some researchers to develop a brushless self-excited synchronous generator without an ac exciter. A previous paper proposed a novel self-excitation scheme by which the second-space harmonic component of armature mmf is used for exciting the rotor field system. In this excitation scheme the effect of the series excitation characteristics, as well as a self-excited and brushless implementation without an ac exciter is automatically obtained. However, in the case of system configuration of the generator already reported, voltage regulation in the inductive load condition was very large. To remove this problem, this paper presents a new system configuration of the generator with a self-regulating feature that can compensate voltage regulation automatically. The new generator consists of a stator installing two three-phase windings, externally connected to a load and a capacitor bank, respectively, and a rotor with field and harmonic windings. In this paper the system configuration and theoretical concepts of the presented generator are described and detailed experimental investigations with a laboratory machine are also shown. [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]

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 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]

Wind turbines on the coast of the Sea of Japan have been damaged by lightning in winter. This is due to the frequent occurrence of upward lightning from wind turbines in winter. Occurrence of upward lightning proves to be closely related to the temperature distribution at high altitudes. In this paper, the correlation between lightning hits of wind turbines and the height of the-10 °C layer is analyzed. When an upward lightning hits a wind turbine in winter, the height of the-10 °C layer is lower than 2000 m in most cases. Moreover, winter lightning is classified into two types, namely, the storm type and the inactive type, and it is found that the parameters of lightning currents observed by LLS differ depending on the type of lightning storm. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(2): 44-50, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22357 [ABSTRACT FROM AUTHOR]

In this paper, the optimal allocation of mega-solar is examined using data envelopment analysis (DEA). A great deal of attention is paid to photovoltaic power generation in Japan. Because such power generation can be freely used, it is attractive in Japan, which has few natural resources. The allocation of mega-solar, a large-scale photovoltaic power generation method, is an important problem for meeting the hope of efficient operation. We tried to apply DEA in Shizuoka Prefecture and to solve this issue. In this type of DEA application, some analyses often result in zero weighting factors in the parameters of some items to be studied, which implies that the corresponding items are not appropriately evaluated. The existing studies do not give special consideration to this situation. In this study, a new calculation scheme is proposed, the above-stated problems are successfully resolved, and the optimal candidate sites have been selected for the mega-solar allocation. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 24-32, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22322 [ABSTRACT FROM AUTHOR]

A linear induction motor (LIM) is suitable for use in trains. The motor can be used in both wheel-suspended and contact-less types such as the Linear Metro and HSST trains in Japan. The LIM has end winding as well as asymmetrical winding. The end effect is a major problem in the LIM, and it makes the analysis, design, and control of motors difficult. This paper describes a method that combines numerical analysis and the equivalent circuit for the LIM in order to design a high-performance controller for the LIM that includes the end effect. A sample basic field-oriented control scheme that is based on the plant model is applied to the LIM in order to check the control performance. The theory of rotary induction motors is used for verification. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(2): 44-54, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21171 [ABSTRACT FROM AUTHOR]

This paper presents a new control circuit to create a high-performance noninverted buck-boost converter with dual ΔΣ modulations. Experimental load regulation, corresponding to load current steps of ±0.5 A, is within 45 mVpp, and the efficiency without a synchronized rectifier is 83% at an input voltage of 2.5 V and a load current of 0.8 A. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(2): 21-28, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21115 [ABSTRACT FROM AUTHOR]

In order to reduce CO2 emission from residential sectors in Japan, PEFC with high efficiency and low environmental impact is expected as one of the promising micro-cogeneration (µCGS) systems. However, the energy demands in houses largely differ from each other and the profiles are also changed every day. Thus, when µCGS is actually introduced, it is necessary to examine the equipment capacity and operation of µCGS in each house. In this paper, the optimization model is developed in order to evaluate the µCGS based on daily-basis demand data. Using actually monitored energy demand data in four households, the differences between using daily-basis data and using the monthly-average data are evaluated from viewpoints of economic and environmental performance of µCGS systems. Moreover, by adding the penalty factor to disposal heat of µCGS, it is seen that system configuration and system operation of µCGS can attain CO2 reduction and energy conservation as well as cost reduction. ©2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 20–30, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20653 [ABSTRACT FROM AUTHOR]

For signal analysis, the Fourier transform and the linear prediction methods are the main approaches. In recent years, the wavelet transform, which gives an expression in the time–frequency domain, has been attracting attention. In the wavelet transform, scale and shift operations are used to analyze regional waves in the signal. In this paper, we propose a new method for signal analysis. Instead of the wavelet, short sine waves and cosine waves which have slightly different frequencies and phases established beforehand are used. These frequencies and phases play the same role as wavelets in analyzing regional waves in the signal. However, our proposed method is different from the wavelet transform because it does not use multiresolution analysis. In conventional spectral analysis methods, all data are prepared beforehand and calculations are performed by using these data. In the proposed method, the spectrum is updated whenever new signal data come in. We show that the amount of calculation is markedly reduced and that real-time spectral analysis can be achieved. Finally, we present an analysis of Japanese vocal sounds using the proposed method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 43–50, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20504 [ABSTRACT FROM AUTHOR]

The development of a wind turbine generator system in Japan is regarded as a promising source of clean energy, and its popularization is rapidly increasing. In Japan, there are many wind turbine generator systems installed on the Sea of Japan coast, with large wind capacity. However, since the Sea of Japan coast is a region with abundant winter lightning, a phenomenon peculiar to Japan, the wind turbine generator systems are subject to damage from winter lightning. Thus, it is important to observe the lightning currents striking wind turbine generator systems in order to provide lightning protection. The authors therefore installed currents sensors (Rogowski coils) on wind turbine generators installed in Hokkaido and Kagoshima Prefectures, and performed waveform observation of lightning stroke current in the winter of 2002 and the summer of 2003. These observations yielded a few current waveforms for lightning striking wind turbine generators. This paper describes the investigation and presents the observation results. [ABSTRACT FROM AUTHOR]

We have recently proposed a new controller based on equilibrium point analysis for power system models. In this paper, first the Japanese standard one-machine infinite-bus system model is formulated, and the equilibrium points are analyzed. Next, complementary control inputs for AVR and GOV with limiters of the system model are determined on the basis of the analysis. Finally, it is shown that the unstable equilibrium point is eliminated by adding the proposed inputs, and then the critical clearing time can be improved in comparison with PSS of the standard model. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(3): 16–23, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20359 [ABSTRACT FROM AUTHOR]

Seismic electromagnetic (EM) phenomena have been observed at many laboratories with specially designed systems. Recently we can utilize radio receivers, personal computers, and communication systems with higher performances and reasonable cost. It is possible to observe seismic EM phenomena not only by specially designed systems but also by a simple observation system integrated by these devices and systems. We have created an observation system for seismic EM phenomena with them in the very high frequency (VHF) band, from 76 MHz to 90 MHz, assigned for FM broadcasting exclusive use in Japan. We are surrounded by many EM waves, such as broadcasting, communication usage, and man-made noises. Thus, we have newly developed the dual frequency observation method. In this paper, we describe an observation method that can identify whether a received signal is a broadband EM wave or an artificial FM radio wave. Next, the observation results for broadband EM waves from galactic noise and solar flares are presented. Then, the observation results for FM radio waves reflected from sporadic E layer and the Leonid meteors are shown. Finally, the observation results for the detected broadband EM waves associated with the Geiyo earthquake are described. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 36–44, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20350 [ABSTRACT FROM AUTHOR]

The national target for PV capacity in Japan is 4.82 GW in 2010, and several PV Roadmaps for up to 2030 are also described. To achieve the target, several support programs, such as subsidization for capital costs, Green Credit by the Green Power Certification System, and buy-back under the Renewable Portfolio Standard law, have been already introduced. A carbon tax is still under consideration, but there are several analyses about the possibility of a carbon tax. The purpose of this paper is to analyze the PV system sales price and subsidies through buy-back which make photovoltaics cost-competitive with other energy technologies and make the target for PV capacity achievable by 2030 in Japan under an expected carbon tax. For the analysis, the energy system of Japan is modeled using MARKAL. Based on the results of the analysis, under a 6000 JPY/t-C carbon tax, photovoltaics need a subsidy for a while even if we take both fuel savings and Green Credit into account. In order to attain the national target for PV capacity in 2010, photovoltaics need more expensive buy-back than in the present, but after 2010 the necessary buy-back decreases gradually. If 120 JPY/W PV system sales price is attained by 2030, photovoltaics become cost-competitive without any supports. Subsidy through buy-back becomes almost unnecessary in 2030, if we can reduce it to less than 170 JPY/W. The total necessary buy-back reaches a peak in 2025. It is much more than ongoing subsidy to capital cost of PV systems, but annual revenue from the assumed carbon tax can finance the annual total necessary buy-back. This means that if photovoltaics can attain the targeted PV systems sales price, we should support it for a while by spending carbon tax revenue effectively and efficiently. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(3): 27–37, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20248 [ABSTRACT FROM AUTHOR]

Mesospheric optical phenomena (including sprites) are becoming an interesting subject from the standpoint of atmosphere–ionosphere coupling. This paper deals with our observation of sprites associated with winter thunderstorms in the Hokuriku area and we show the characteristics of those sprites and their parent lightning discharges. Although the scale of Japanese lightning in winter is very small compared with the MCS (Mesoscale Convective System) for the summer continental lightning, the essential quantities (polarity, charge transfer, and so on) are found to be nearly the same as those for the MCS. However, an additional factor might be required, such as the self-organization of the lightning. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 9–17, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20178 [ABSTRACT FROM AUTHOR]

The rapid spread of CHP systems will put pressure on the regional power system to require an examination of the power and heat output of CHP systems. When considering the countrywide potential of the CHP system, one should examine such a system in coordination with the grid power system. It is essential to calculate the heat and power demand at end-use level. In this paper, annual heat and power demands of end-use sectors are forecast to the year 2025 based on 20-year data. Regression analysis is used. Estimated annual demands are divided into the seasonal hourly demands considering demand characteristics. Daily load curves of heat and power demands are determined for the Japanese end-use sectors, and the annual changes of such demands are shown by duration curves of heat-to-power ratios. Moreover, the grid power daily load curves are computed numerically from the estimated heat and power demands for the manufacturing, residential, and commercial sectors. Such load curves also consider self-generated power for the manufacturing industry and self-consumption of the grid power. Estimating heat and power demands allows for a joint analysis between the power system and the future phasing in of CHP systems. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 18–30, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20162 [ABSTRACT FROM AUTHOR]

This paper proposes a high-speed reclosing operating method to improve the stability in a power system. The proposed method calculates the reclosing time, taking a standard case in which the reclosing is not done using the generator phase angle δ, and the angular velocity ω, and the field system voltage ed'. Also, the execution of reclosing time is calculated, while taking into consideration the acceleration/deceleration energy of the generator during a fault. It can be expected that δ is suppressed by this optimum reclosing operation. Therefore, the system stability can be expected to improve by carrying out high-speed reclosing when a fault occurs. At present, it has been set at a value which seems to be optimal considering various problems in the reclosing time. However, in those methods, the system stability improvement effect cannot be expected. It was demonstrated that the high-speed reclosing method serves to depress δ in the computer simulation. [ABSTRACT FROM AUTHOR]

Retail competition in the electric power market was introduced in Japan in March 2000. Although the liberalization is limited to a part of the retail power market having about 30% of the total electricity demand, the liberalized customer segment is now subject to competition among the utilities and new entrants. This paper examines the profitability of competitive pricing for eligible segmented customers through a scenario-based model analysis focusing on the demand characteristics of segmented customers. The model includes the utility's investment in power generation for segmented customers, considering long-term rather than short-term profitability. Load leveling is not always achieved under profit-maximizing behavior of the utility because the profitability of competitive pricing depends on load patterns of bypassed customers and price differentials among power suppliers. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(4): 43–52, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10111 [ABSTRACT FROM AUTHOR]

This paper proposes a new method of evaluating the kW-value of photovoltaic power generation systems (PV systems). This evaluation is based on actual insolation data, collected by the Japan Meteorological Agency at four locations in the Chubu area in Japan, and the actual electrical load data of the Chubu area in the 1990s. We selected specific days on which the daily peak load was relatively high. For the selected days, we estimated the average output of PV systems using the IEA's method for considering the temperature dependency of cell efficiency. Then, we calculated the reduction of the peak load ΔLp(d). The resultant ΔLp(d) was distributed in the range from 0.4 to 0.5 kW/kWp. We evaluated the average value of the smallest ΔLp(d) as the kW-value of PV systems. When the kW-value was evaluated for the two or three days with the smallest ΔLp(d) among the selected 10 days for 1 year, the kW-value of the PV systems was calculated to be about 30%. This was close to the value obtained by the conventional loss of load probability (LOLP) method. Our study evaluates the relationship between the kW-value of PV systems and the number of days on which the insolation was low but the daily peak demand was relatively high. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 42–49, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10089 [ABSTRACT FROM AUTHOR]

Studies on superconducting generators have been carried out worldwide. Especially in Japan, it is worthy of attention that Super-GM led the national project concerning the successful development of the 70 MW-class superconducting generators. Low-temperature superconducting wires have been applied to field windings of generators. In Japan, the next-generation coated conductors, namely, high-temperature superconducting wires, have proceeded under the national project supported by NEDO. Provided that the next-generation coated conductors are applied to field windings, the weight and volume of superconducting generators will be reduced. Furthermore, using liquid nitrogen as a coolant instead of liquid helium, the reliability of high-temperature superconducting generators is expected to improve. This paper provides tentative designs of a high-temperature superconducting generator whose field windings are composed of YBa2Cu3O7-x wires. By comparison with the low-temperature superconducting generator developed by Super-GM, the usefulness of the high-temperature superconducting generator is discussed. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 1–7, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10052 [ABSTRACT FROM AUTHOR]

Biomagnetic signals are very weak compared with those of the environmental magnetic field due to trains and motorcars. Trains, especially direct-current electric railcars, seem to be one of the main urban magnetic noise sources of low frequency in Japan, as indicated by comparing the fluctuation of the magnetic field during the day when there are many trains with that at night when there are no trains. In this paper, the relationship between the environmental magnetic field and the electric current of the direct-current electric railcar of the personal track is discussed. Next, the fluctuation of the magnetic field is calculated from that of the unbalanced electric current between feeder line and railroad, which could be obtained as the leakage electric current to the ground. The validity of the calculation is verified by comparison with measurements. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 10–21, 2001 [ABSTRACT FROM AUTHOR]

In Japan, electric power utilities purchase electricity from independent power producers (IPPs) through competitive bidding; the IPP evaluation is based on the avoided costs of corresponding generators of utilities. In this evaluation, however, nonpricing factors such as power flow constraints in the electric power system cannot be considered. In this paper, we propose a new approach to evaluate economic impacts of IPPs, the IPP electricity being priced on the basis of total generating costs of the electric power utilities. Such a price to purchase the electricity of IPPs is referred to as the “break-even cost.” The main results are summarized as follows: 1) Break-even cost depends on not only the power flow constraints in the system, but also various IPP factors such as generating pattern, location, and capacity, 2) Break-even cost for the base-type IPP is higher than the avoided cost of corresponding utility generators, because IPPs located on demand sides can reduce the transmission power loss in the electric power system, 3) Break-even cost is affected by available capacity of utility generators, especially for the peak-type IPP generating only during peak demand periods. © 2000 Scripta Technica, Electr Eng Jpn, 133(2): 20–30, 2000 [ABSTRACT FROM AUTHOR]

This paper investigates a low-velocity-layer (LVL) model for an artificial subsurface fracture examining dispersions of crack waves. Subsurface fractures are important in extracting geothermal energy. The crack waves are seismic modes propagating along the fracture. The LVL represents a zone in which many small fractures are distributed around a main single fracture. The crack waves were measured at an artificial subsurface fracture at a depth of about 370 m in the Tohoku University Higashi-Hachimantai Hot Dry Rock model field, Japan. The wavelet transform is applied to describe the dispersion of the crack waves. Crack-wave dispersions affected by the pressurization of the subsurface fracture are obtained. The numerical dispersion curves are also calculated in the LVL model using a matrix method. When the aperture of the subsurface fracture increases by the pressurization, the LVL model shows good agreement with the crack-wave dispersion. The LVL model is, however, insufficient for the crack-wave dispersion detected at the beginning of pressurization. © 2000 Scripta Technica, Electr Eng Jpn, 131(4): 58–69, 2000 [ABSTRACT FROM AUTHOR]

The track circuit uses the rail as part of the circuit. The purposes of the track circuit are (1) to detect the train, (2) to transmit signals to the train, and (3) to detect rail breaks. There are two types of track circuit. One uses insulation joints at the end of the circuit, and the other is jointless. The insulation joint requires much effort to maintain and control. Furthermore, it is extremely expensive, and uses an insulation material, which is one of the weak points of the rail track. There are some methods for constructing a jointless track circuit, but they have several problems. The biggest one is that the border of the track circuits becomes fuzzy. Another is the interference of multiple track circuit signals. Nevertheless, jointless track circuits have high priority. First, they do not demand an insulation joint and impedance bonds. Second, they are very easy to divide. Jointless track circuits are used for sharp curves where it is impossible to install insulation joints on the Shinkansen line. Also, several conventional lines and private railways use this system. Furthermore, several European high-speed train systems also use jointless track circuits. Regarding Japan Railway, short-distance track circuits for level crossing control are jointless, but normal track circuits have insulation joints, because there is a legal restriction on track circuit border ambiguity. To solve this problem, the author worked out a simple jointless track circuit only with induction coils, whose border characteristics are excellent. Furthermore, it does not have a strong frequency characteristic and it can be applied to any frequency. In this paper, a new type of jointless track circuit is proposed and theoretically analyzed, and basic experiments are reported. © 1999 Scripta Technica, Electr Eng Jpn, 127(4): 64–76, 1999 [ABSTRACT FROM AUTHOR]

In Japan speed tests in the region of 300 km/h have been carried out since the Oyama test line recorded a 319 km/h run in 1979. TGV recorded a 515.3 km/h run by an electric locomotive installed with a pantograph in 1990 and ICE achieved 406.9 km/h using a similar train in 1988. High-speed current collection tests over 400 km/h using electric railcars have been desired in Japan. Problems of high-speed tests are: train speed approaching wave propagation velocity, multipantograph resonance, and too large uplift of contact wires caused by lift. It is necessary to keep wave propagation velocity of contact wire higher than train speed. CS contact wire and TA contact wire were compared in high-speed tests because it was impossible to get a good current-collecting performance by using hard-drawn copper contact wires. In December 1993 using these contact wires we carried out high-speed tests in the region of 400 km/h on Jyoetsu Shinkansen with the test train STAR 21 which JR-EAST built for high-speed tests. This paper reports the current collecting performance of these contact wires predicted by simulation and running tests at 425 km/h. © 1998 Scripta Technica, Electr Eng Jpn, 124(3): 73–81, 1998 [ABSTRACT FROM AUTHOR]

We wish to derive an improved analytic method and performance equations for estimation of the characteristics and the design of a reasonable LIM. An approximation that simplifies the estimation of the performance of the single-sided linear induction motor is presented. The original equations were derived from the two-dimensional electromagnetic analysis and the equivalent circuit quantities, such as the magnetizing reactance, resistance, the secondary resistance and reactance, and are given in combination with hyperbolic and trigonometric functions of complex number. In this paper, these functions are approximated by the McLaurin's expansion, and the equivalent circuit quantities are expressed by polynomial approximations. The computed thrust, primary current, power factor and efficiency-slip curves for the test of urban-transit SLIM at Kyushu University, calculated from the original equation and the new approximation, show a close agreement. The magnetizing reactance plays an important role in the LIM performance and the larger it is, the better. The ratio of air gap length to pole pitch is the key to the performance of the LIM. [ABSTRACT FROM AUTHOR]

This paper presents a new discrimination procedure of signal waveforms based on wavelet theory for the inspection of rotating machinery. The wavelet transform decomposes signals into time-frequency space, rather than mere frequency space, limited by the uncertainty principle. This decomposition permits time-frequency analyses and provides a more flexible means of signal processing than before. To examine a rotary compressor pump, particular waves in the rotational load torque signals that correlate with failure modes are discriminated from one another and evaluated. To extract the focal waves, the signal is decomposed with wavelets and then only particular waves, such as impulses, are reconstructed from a selected set of wavelet coefficients. This is called time-frequency space filtering. The wavelet local modulus maxima are used to open a time-frequency window through which only the focal waves can pass with high fidelity. The maxima have information of the inflection points of the wave at each resolution that represent its waveform. The experimental results show the effectiveness of the procedure. [ABSTRACT FROM AUTHOR]

In commercializing the superconducting Maglev system it is important to reduce the cost, especially that of ground coils constructed along the whole length of the guideway. For this purpose we have examined the combined propulsion, levitation and guidance system (PLG system) which can generate levitation, guidance and propulsion, forces by the same coil. This paper describes the test run of the PLG system, whose ground coils (PLG coil) are constructed in one part of the Miyazaki test track. In designing the PLG coil, we make clear the magnitudes of the force acting both under normal and unusual conditions because the electromagnetic force, which levitates, guides, and propels the vehicle, directly acts on the magnet winding of the PLG coil. In the experiment, we examine both the performance of the vehicle and the force of a PLG coil. The measurement of the force at the PLG coil gives not only propulsion force and levitation force directly, but also guidance stiffness by sifting the measured coil. Good correlation recognized between the calculation and the experiment in the propulsion force, levitation force, and guidance stiffness proves that the required characteristics can be expected from the PLG system even under combination of propulsion, levitation and guidance. [ABSTRACT FROM AUTHOR]

When electric power supply interruption is caused by a fault, it is imperative to restore the power system promptly to an optimal target configuration after the fault. The problem of obtaining a target system is referred to as power system restoration. Both mathematical programming (MP) and expert system (ES) have been used to solve restoration problems. However, existing approaches based on their MP and ES are effective in that they can utilize expert knowledge, maintenance of large-scale ES requires inordinate effort. This paper proposes a new approach to power system restoration that utilizes both methodologies so as to exploit both system' advantages. That is, a system under study is decomposed into a set of subsystems based on the knowledge of restoration experts, which is realized as an expert system. Then, MP is applied to each decomposed subsystem to obtain an optimal target configuration. A feasible operation sequence leading to the target configuration is generated by ES. This approach reduces significantly the computation time required to obtain target systems and is far less than would be the case if the total system is solved (as a unity). Moreover, the number of rules in the knowledge-base are greatly decreased. [ABSTRACT FROM AUTHOR]

This paper proposes a transmission line tower model in frequency domain for back-flashover analysis, which has a uniform characteristics impedance and a uniform propagation constant. Most conventional tower models are constructed as a constant and uniform parameter transmission line that is independent of frequency. However, the author's models have the frequency dependency of the characteristics impedance and the propagation constant to express the frequency characteristics of the transmission line tower. Two models, a cylinder model and a four-frames model, were investigated to stimulate the tower. Their surge response were computed by numerical electromagnetic field analysis based on the moment method. From the results, the two-port circuit constants were calculated in the frequency domain, and the characteristics impedance and the propagation constant are derived from them. The complex artificial oscillations appeared in frequency dependency of the parameters because the parameters were calculated numerically. The equations with analytical form were obtained by approximating with a smooth curve to the oscillations. It is possible for the equations to represent the transmission line constants as a function of geometrical parameters such as the towers height and the radius. Close agreement was found between the surge response computed by the numerical electromagnetic field analysis and the result calculated by inverse Laplace transformation of the analytical equations. To prove the model, the experimental results were compared with the computed ones of the cylinder model that has arms, and it was shown that the new model agrees closer with the experiment than conventional transmission line models. [ABSTRACT FROM AUTHOR]

Research on decentralized control of an electric power system is important for stabilizing control problems. In particular, since an electric power system is a large-scale nonlinear control system, decentralized (not divided) systems with cooperation should be constructed. This paper presents ways to construct decentralized systems for an electric power system. In section 2, swing data of a three-machine model infinite-bus system with AVR and GOV are estimated by the least square method. In section 4, the equivalence calculated using estimated values is discussed, and the effect of conditions on the fault is considered. Finally, section 5 is devoted to summarizing results of decentralized system identification. [ABSTRACT FROM AUTHOR]