Islanding Operation Control Method of Micro-grid Including Seamless Transition from Grid-connecting Operation

The micro-grid has been operating at institute of technology of Shimizu Corporation since July, 2006. Main generators are two gas engine CHP (Combined Heat and Power) systems which rated output are 350kW and 90kW. Two power storage devices, a secondary battery and an electric double layer capacitor, are also installed to compensate rapid load fluctuation. This paper proposes an islanding operation control technique for these equipments using an integrated central control by central control server and an autonomous control of electric double layer capacitor. It is possible seamless operation transition between grid-connecting operation and islanding operation because condition signal of circuit breaker has transmitted to each generator at 30 milliseconds. We have verified validity of the developed control method by using the micro-grid. As the results of 50 times transition experiments, frequency fluctuation target (within 0.2 Hz) has been satisfied with probability 99.9% and voltage fluctuation target (within 10%) has been satisfied with probability 100.0%.