If both EVs (Electric Vehicles, includes plug-in hybrid electric vehicles) and renewable energies spread in large quantities, it is possible to control the supply fluctuation of renewable energies using the storage battery of EVs. This research tried to show the charge load potential of EVs based on the state of the Japanese passenger car using traffic census results etc. Furthermore, it tried to show trend of the storage battery capacity according to time. From the estimated result; (1) the charge electricity of low and middle distance gets a majority of the total charge demand, (2) charge load changes according to time several times, and the minimum load is the number of GWh at early morning, (3) if night charge is assumed, the standby charge demand of noon will reach tens GWh, it may have sufficient scale for supply fluctuation control of PVs. Although the present EV is not suitable for long-distance running, these are expected to be 30 or less percent of the total charge demand. The estimated storage capacity potential in this research will not change numbers of times.
This paper describes the electrical response in load change concerning a fuel cell system fueled by high-purity hydrogen. The purpose of this study is that the fuel cell system is applied to make up for unstable electrical output of a photovoltaic system as a renewable energy. As an alternative method of secondary battery, the fuel cell system, which is able to continuously generate power as long as fuel is supplied, is expected to provide power with high reliability and stability. To evaluate the load-following capability of a polymer electrolyte fuel cell (PEFC) system, an experimental equipment was constructed with a 200W PEFC stack (number of cells: 20, cell area: 200cm2) which was supplied with hydrogen from a compressed hydrogen cylinder and a metal hydride canister. We measured the transient phenomenon of current and cell voltage when the PEFC stack was inputted step-up current loads that changed in the range of 0∼300mA/cm2. As a result, we have found that the PEFC system with both hydrogen supply sources is able to response at a time constant of 6.6∼11.6μsec under enough oxygen supply and a load below the PEFC rated power.
Recently, the amount of distributed generation (DG) such as photovoltaic system and wind power generator system installed in a distribution system has been increasing because of reduction of the effects on the environment. However, the harmonic troubles in the distribution system are apprehended in the background of the increase of connection of DGs through the inverters and the spread of power electronics equipment. In this paper, the authors propose a restraint method of voltage total harmonic distortion (THD) in a whole distribution network by active filter (AF) operation of plural power conditioner systems (PCS). Moreover, the authors propose a determination method of the optimal gain of AF operation so as to minimize the maximum value of voltage THD in the distribution network by the real-time feedback control with measured data from the information technology (IT) switches. In order to verify the validity of the proposed method, the numerical calculations are carried out by using an analytical model of distribution network interconnected DGs with PCS.
Load frequency control (LFC) in future power systems, in which a large amount of solar photovoltaic generation is introduced, is studied. The constraints in LFC resources are classified as rate, simple, and energy limits. First the nonlinear transfer functions of the limiters are modeled using random noise input. Second the transfer functions of limiters are characterized by coefficients of necessary facilities (CoNF). Third the appropriateness of concept and identified value of CoNF is demonstrated through numerical simulations using a simple power system model. Also a way to control the contribution of existing and introducing resources to regulation of frequency fluctuation is proposed and demonstrated.
The purpose of this paper is to grasp the partial discharge property of closed voids under the low vacuum involved in an epoxy resin. When an epoxy resin insulator is manufactured in a factory, some voids may be involved in it. To prevent the invasion, partial discharge is measured for insulators. However, partial discharge may not be detected due to the low vacuum in voids right after the manufactory. Well-known Paschen curve testifies this phenomenon, which describes the partial discharge property ranging from a high vacuum to the atmospheric pressure. However this Paschen curve is acquired several gases between parallel-plane metallic electrode gaps. There is little clear statement of Paschen carve on the void. Therefore authors of this paper studied the partial discharge characteristics of the void within the epoxy resin under the variable vacuum level.
When we examine the lightning frequency and the lightning shielding effect by EGM (electro-geometric model), we need the current distribution of all lightning to the ground. The lightning current distribution to structures is different from this distribution, but it has been used in EGM conventionally. We assumed the lightning striking distance coefficient related to height of structures for getting the result which corresponds to observed lightning frequency to structures, and estimated the current distribution of all lightning to the ground from data listed in IEC 62305 series by EGM. The estimated distribution adjusted by detection efficiency of LLS almost corresponded to observed distribution by LLS.
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 turned out to be closely related to temperature distribution in high altitude. In this paper, correlation between lightning hits of wind turbines and the height of -10°C layer is analyzed. When an upward lightning hits a wind turbine in winter, the height of -10°C layer was lower than 2000m in most of the cases. Moreover, winter lightning is classified into two types, namely storm type and inactive type, and it is found that parameters of lightning current observed by LLS differ depending on the type of lightning storms.
In recent years, frequent damages of wind turbines by winter lightning have been reported in the region along the Sea of Japan. It is a serious finding that lightning hits concentrate on wind turbines in this region. The authors investigated the rate of increased frequency of lightning hits on wind turbines due to its construction by using LLS (Lightning Location System) data. As a result, an experimental formula to estimate the increase rate of the frequency of lightning hits on wind turbines as a function of parameters related to the construction condition, namely the height of wind turbines, the height above the sea level and the latitude, is proposed.
The Editorial Committee is working in planning and editing of the publication of Power and Energy Society. In this article, activities of the committee of the last term are reported, and recent trend and future problems are also discussed. The process of planning and editing of the publication, and the challenges to reduce the necessary months for reviewing papers and to increase the number of submitted papers are shown.