A Control Method for Inverter Used for Distributed Power Supply under Voltage Sag Condition

Inverters which are used for distributed power supply, such as solar cell or fuel cell system, tend to stop easily as a result of voltage sag. In the present electric power system, there is little problem due to this characteristic of inverter. But if the number of those inverters connected to the power system increases, the quality of system voltage and frequency may deteriorate by stop of the inverters. In addition, regarding the fuel cell system, its output power cannot be controlled quickly, and the whole system may stop by a rise of inside temperature. For these problems, we tried to realize high continuous operation ability of inverters used for distributed power supply under voltage sag condition. This paper shows a control method of inverter for the over-current caused by sudden change or unbalance of the system voltage and examination results with three-phase 200 V-4 kW class inverter system. (C) 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(1): 28-40, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20888