Satoshi Uemura

Cooperative control of distribution system with customer equipments to reduce reverse power flow from distributed generation

It is expected that large capacity distributed generation (DG) systems including photovoltaic (PV) power systems will be installed in future power systems. When the capacity of PV power systems installed in the distribution system increases, reverse power flow may cause problems. To deal with these problems, control equipment such as static var compensators and storage batteries can be used. However the cost of such control equipment is relatively high. Therefore, it is necessary to minimize the capacity of them. In this study, cooperative methods of controlling customer equipment to reduce the capacity of control equipment are proposed, and the effectiveness of the methods is evaluated by simulation analyses. The simulation results show that the amount of reverse power flow from PV power systems and the required capacity of the control equipment are reduced by the proposed cooperative control methods using the heat pump water heaters (HPWHs).

Demonstrative study of control system for distribution system with distributed generation

When the volume of the distributed generation (DG) is increased, the voltage variation may occur in the distribution line. To keep the distribution line voltage for smooth power supply, a research project “Demonstrative Project on Power Network Technology” was carried out from 2004 to 2008 under the research contract with the New Energy and Industrial Technology Development Organization (NEDO). In the project, control devices and a centralized control system to keep the distribution line voltage properly were developed and demonstrated. In this paper, demonstration tests to keep the voltage of the distribution line were carried out by use of static var compensator (SVC) and loop balance controller (LBC). Then, the required capacity of the control devices were estimated analytically. As a result, an optimal selection of the control device and the control method is considered according to the penetration ratio of the DG.

Development of Autonomous Demand Area Power System in Criepi

Abstract A large introduction of distributed power generation is expected. Under such circumstance, power flow congestion, voltage fluctuation and degradation of safety on distribution systems will occur by the operation of the distributed power generations. As a strong measure of the issues, we have proposed a unique, new power supply system called “Autonomous Demand Area Power System”. The system leads free access of the distributed power generation to the grid and makes effective use of the generations using power electronics devices and communication network. The paper described concept, composition and operation measures of the Autonomous Demand Area Power System.

Experimental study on short circuit phenomena in air switch of distribution line due to lightning overvoltage on which one surge arrester of the three ones is omitted

We experimentally examined the possibility of the internal short circuit of an air switch due to the sparkover between different poles under the condition that no surge arrester exists in neighboring poles and one of three surge arresters is omitted at the pole with an air switch. Experiments at Shiobara Testing Yard and Akagi Testing Center of CRIEPI clarified the following. Fault current may flow via the grounding point of a pole with an air switch and that of the next pole on a different phase from grounded phase of the pole with an air switch. If the low-voltage wire, overhead ground wire or communication wire forms a short circuit between them, ultimately the air switch may burn out. Moreover Fault current continues even if the length of the short circuit between different poles is increased. Although the increase of the short-circuit length results in the increase of wire impedance, the amount of increase is still small compared with source impedance.