In large-scale deployment of electric vehicles, their charging demands are concerned to cause load flow congestions of the power system, especially in the distribution feeder around residential area. There are many studies on charging demand analysis considering the power system bottlenecks and the smart charging schemes mitigating the impact on the power system. Flexible demand dispatch by the electric vehicle charging would be expected as candidate of fast demand response resources. The electric vehicles are also expected to be an aggregated mobile energy storage for integrating large-scale renewable energy sources into the power system. V2G control schemes, which are focusing on the ancillary services for the power system, are being implemented to the electric vehicle and charging infrastructure system targeting the smart grid strategy. This paper summarizes the technical subjects and perspectives on cooperation of the electric vehicles and the power system through the fundamental research achievements and the reviews of smart charging and V2G applications.
In future, plug-in hybrid automobile (PHV)/electric vehicle (EV) will come into use with the arrival of Low-carbon society in the next twenty years. On the other hand, the power generation system using renewable energy installed in power system as one of the countermeasure for problems of the global warming. Then, the new problems in EV and energy will occur. This paper describes the examination is carried out on the charge control method of PHV/EV in the micro-grid for efficient use of the battery.
In the future, renewable energy (RE) generation systems will be constructed and interconnected to the power system by the non-utility entities such as generation companies and residential customers. Therefore, the generation expansion planning (GEP) should consider the effects of RE generations. The purpose of this paper is to discuss the best GEP from economic, supply reliability and environmental aspects considering penetration of RE generations. For this purpose, this paper proposes a model of utility's GEP process considering the RE generations. The proposed method is based on the stochastic dynamic programming (SDP) in which the long-term uncertainties are modeled by the geometric Brownian motion (GBM) and the binomial lattice process. Furthermore, the variation of RE generation output due to the weather condition (short-term uncertainty) is also considered in the proposed method by means of the net load curve.
A fault locator system in a loop-shaped distribution system with inverter based distributed generations is proposed. An algorithm of proposed fault locator system is based on the impedance obtained by the phase-voltage and line-current at the transformer feeder in the power distribution substation. We have proposed the quadratic equation expressed in terms of fault location. The quadratic equation represents the impedance from the substation to the fault location. Inserting the impedance obtained by the voltage and current at the transformer feeder into the quadratic equation, two candidates of the fault location are obtained. We can select the true fault location from the two candidates by using the characteristics of impedance calculated by the voltage and current at the incoming feeder of distributed generation. The validity of the fault locator system was investigated by PSCAD/EMTDC simulations. As a result, it was found that impedance obtained by the information of the substation and distributed generations are useful for searching the fault location in the loop-shaped distribution system.
The authors are planning a shared energy center for ensuring a cheap and reliable power supply to the Japanese Industrial Park in India. The shared energy center interlinks together diesel engine generators (DEGs) from different companies by applying the concepts of smart grid technology. The algorithm of economic load dispatch (ELD) coordinating self healing dispersed power supply is investigated. The case study is carried out according to the proposed algorithm. The generators are operated at optimal point in this algorithm considering fuel cost, spinning reserve capacity, interchange electric power, and the system stability. In this paper, the details of algorithm are explained and the improvement of the control performance is shown.
In order to maintain a soundness of power system with fluctuating highly penetrated photovoltaic generation (PV), accurate irradiance forecast will be important in the near future. A substantial amount of PVs will be penetrated on numerous points in power service area, and it is necessary to predict total PVs output for supply/demand balancing control. Therefore irradiance forecast accuracy should be verified by total irradiance on numerous points correspond to highly penetrated PVs in the area. This paper shows an accuracy study on an approach to predict area total irradiance using regional numerical weather prediction data by the Japan Meteorological Agency. Forecasted area total irradiance is compared to the presumed total area irradiance of numerous points which corresponds to highly penetrated PVs distribution.
In this paper, based on the data of field exposure test, which was initiated by Japan Electrical Safety & Environment Technology Laboratories (JET), we investigate the degradation characteristics of crystalline silicon PV modules by using its equivalent circuit model for the purpose of the lifetime extension in the development of PV modules. Specifically, we observe the degradation of bus bar electrode and solar cell by capturing electro luminescence images and infrared images of the surface of PV modules when forward voltage is applied. Although this observation enables us to determine which part of the PV module deteriorates, it is impossible to quantitatively evaluate how much each deteriorated component has an influence on power degradation. Accordingly, using the equivalent circuit model of the PV module, we calculate the equivalent circuit parameters from the measured I-V characteristics of the PV modules in the field exposure test by the least squares method. We adopt the photocurrent, series resistance, shunt resistance and diode factor as unknown parameters in the equivalent circuit model. Based on the change of the circuit parameters, we evaluate the influence of the deterioration of each component on decline of output power quantitatively.
A photovoltaic power generation system (PVS) is one of the promising measures to develop a low carbon society. Because of the uncertain power output characteristics, a robust power output forecast method must be employed for realizing the high penetration of PVS into an electric power system. Although there are several researches focusing on the forecast of single point insolation, the research focusing on the forecast of spatial average insolation in electric utility service area is not enough. In this study, we developed method to forecast spatial average insolation using a meso-scale model grid point value (MSM-GPV) data computed by the meteorological simulation. The main results are as follows. In spite of very simple method using a linear function of relative humidity, low/medium/high cloud cover, and extraterrestrial insolation, %MAE of the proposed method using MSM-GPV delivered at 18: 00 is 15.7%, which is smaller by about 10% than that of single point forecast due to the so-called smoothing effect. However, there are still a few days with larger forecast error than 0.3kWh/m2. Such the large error is hardly reduced even with the later delivered MSM-GPV, because of the essential inaccuracy of MSM-GPV.
This paper investigates transient measurements in a scale-down vertical conductor above a conductor plate. A number of experimental studies of a lightning surge in transmission towers have been carried out. However, the influence of measuring wires layout on the measured result has not been well investigated. This paper discusses the effect of a current lead wire and the layout. When a coaxial cable being used as the current lead wire, the measured voltage becomes lower than that for a covered (or bare) conductor being used. For example, the tower top voltage is reduced by 20% in the coaxial cable case. The induced current from the conductor plate representing the earth to the current lead wire also affects the measured result. The sheath current in the coaxial cable case also influences measured results significantly. Thus, it is recommended to use a covered conductor as current lead wire in a scale model experiment above a conductor plate.
High penetration of variable sources of renewable power generation will lead to operational difficulties of supply-demand balancing of an entire power system. The mass deployment of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) will also cause significant changes in electricity demand. Therefore, controlling and managing the charging time of EVs/PHEVs are effective and imperative for improvement of the balancing in the power system operation. We assumed trip patterns of EVs in a model of the future Tokyo power system and analyzed the power system loads, including the charging load of EVs, assuming several charging control scenarios. It was verified that charging-time controls are substantially effective to reduce the fuel costs of the power system. Further, we found that load leveling by multi-car charging management scenario indicated the best results in terms of the fuel cost in all cases.