Feasibility of increase in smoothing-capacitor of battery system for dumping power oscillation in transition to isolated operation of distributed generator

Abstract

This study examines the feasibility of increasing a smoothing capacitor of battery system regarding a high power supply in a short period during the transition to isolated operation of distributed generation (DG). By forming a small-scale facility micro-grid (FMG), DG and battery system can be utilized to protect a part of load against a disturbance of utility grid. For damping the power oscillation in FMG, a battery system would be required to supply a high power in a short period. For this purpose, this study simply focuses on the enlargement of capacity of smoothing capacitor, which is necessary for the voltage-type inverter, instead of increasing the DC power output limit of battery itself including DC-DC converter. This study demonstrates the effect of enlarged smoothing capacitor of battery system on suppressing the oscillation of rotational speed of DG when a 100 kW class FMG is disconnected from the utility grid by using a high-speed circuit breaker. The results show that the battery system with the feasibly enlarged capacity of smoothing capacitor can be useful for a high power supply during the transition to isolated operation of FMG.