LCpL Filter Design and Control for Stability Improvement in a Stand-Alone Microgrid with Sub Inverter Structure

Abstract

The inverter of an energy storage system, which plays an important role in maintaining the voltage of a stand-alone microgrid, can shut down in response to external or internal abnormal conditions. Such a protective measure can cause the microgrid to blackout. A redundant inverter can be configured to respond upon failure of the main inverter to ensure higher stability of the stand-alone microgrid. However, the microgrid may experience several to tens of blackout cycles when the main inverter fails owing to a time delay in the operation of the sub inverter. To overcome this limitation, we propose an LCpL filter for suppressing any sudden changes in the microgrid during the transition period between the main and sub inverters. In addition, this study also describes a control method for the sub inverter to prevent system blackouts. A 100 kW microgrid system consisting of two 100 kW inverters with LCpL filters and loads was used to demonstrate the efficacy/utility of the proposed method.