Constant Frequency Control Strategy of Microgrids by Coordinating Energy Router and Energy Storage System

Abstract

In this paper, a constant frequency control strategy of a microgrid by coordinating energy router (ER) and energy storage system is proposed to solve the frequency fluctuation problem of microgrid, in which ER is the core of the energy management system. The interface converter of ER connected to the microgrid adopts the virtual synchronous generator (VSG) control, which adjusts the mechanical reference power in real time according to the state of charge (SOC) of the energy storage. The energy storage system adopts constant voltage and constant frequency (V/F) control to maintain the frequency and voltage stability of microgrid. The energy storage system with fast charge and discharge responds to the power fluctuation of the microgrid. ER maintains the stability of the energy storage capacity through bidirectional power regulation. When the energy storage system fails, the frequency and voltage droop characteristics of ER controlled by VSG will play a role in maintaining the stable operation of the microgrid. By the coordinating control strategy, the maximum efficiency of intermittent distributed energy can be guaranteed, and the stability, reliability, and grid-connection friendliness of the microgrid operation can be improved. Simulation results prove the effectiveness of the proposed control strategy.