Fumiko Koyanagi

A strategy of load leveling by charging and discharging time control of electric vehicles

By ZEV regulation of the California government in 1992, not only The United States but also many developing countries are interested in replacing gasoline cars by electric vehicles (EV). The electric utility expects that the electric vehicle improves the difference between the daytime and nighttime of recent demand as a new market of electric power demand. There are some reports that indicate on the danger which generates the new peaks as the electric vehicles spread through the market in charging start hour. As a countermeasure for avoiding this problem, the authors propose that (1) the regional charging time shift method is introduced in the midnight charging time zone, and (2) inverse load flow by the discharge of the contract private use EV is carried out as an energy shift in daytime, in this paper. Therefore, the actual energy consumption of the automobile was investigated, and future demand is predicted by the mathematical consumption modeling. Especially, it shows a strategy of optimum introduction on scheme and rate of electric vehicle for effective energy shift. The authors point out the necessity of market regulation for an electric vehicle.

Modeling power consumption by electric vehicles and its impact on power demand

Electric vehicles are expected to be one of the means to level the difference between the peak time and off-peak time electric loads. From a global point of view, increasing environmental concerns make us recognize the necessity of replacing conventional gasoline cars by electric vehicles. Due to problems with the efficiency and life time of a battery, it will take time before electric vehicles are in general use. Electric vehicles are used only in specialized small fields. Automobile makers are cooperating to invent advanced batteries for use in electric vehicle. Thus, it is timely to develop appropriate infrastructure standards and technologies to make electric vehicles attractive to consumers. In this paper, we investigate the impact of electric vehicle on electricity demands by assuming analytical models of EV consumption. The charging characteristics of a battery, the running performance, and the practical driving distance of each type of car are used in this analysis. According to the scenario analysis, the simulations clearly presented the impact of EV introduction using the practical day load duration curve for the Tokyo cosmopolitan area. The authors conclude that electric vehicles are effective for load leveling under some sort of market regulations. If there is no regulation in the EV market, power shortage will occur on both nighttime and daytime because of the concentration of the nighttime charge and the quick charge.

Monte Carlo simulation on the demand impact by quick chargers for electric vehicles

This paper presents a scheme of predicting the impact on the electric demand which may appear as random harmonics with respect to quick charging for widespread electric vehicles (EV). It is known that the battery charging for EV provides a potential problem to power distribution systems. The aims of this work are: (1) to make clear the influence of quick charging on power distribution system, and (2) to assess the optimal penetration level for load leveling to avoid a serious impact of harmonics. Ordinary quick charging will take place at lunch time according to the drivers psychology. This profile can be expressed by the normal probabilistic distribution function. If the penetration level of EV is accelerated, the profiles will appear randomly on the electric demand. Hence we can derive these impacts on power demand by the well-known Monte Carlo simulation. The proposed approach has been verified on a practical ten-machines and 47-buses test system.

Possibility of fuel cell fast charger and its arrangement problem for the infrastructure of electric vehicles

The fuel cell is a very promising energy production system to supply electricity and heat with high efficiency and low impact to the environment. Presently, the effort is paid both to applications for dispersed generator and automobile energy source. However, the infrastructure for fueling of pure hydrogen has been still discussing and investigating. In this paper, the authors propose a new concept for constructing the infrastructure of EV by fuel cell chargers. This unique application is simulated by the scenario analysis as an arrangement problem. The approach uses the modified weighted Voronoi Diagram providing a proper allocation of the chargers for electric vehicle (EV). The simulation presents a suitable distribution and the possible implementation number of EVs when 100 chargers, including the fast charger and the parking charger, are introduced in Tokyo metropolitan area.