Virtual synchronous generator based frequency control in interconnected microgrids

To achieve a sustainable energy supply, the expectations are increasing for autonomous decentralized microgrids (MGs) that effectively combine renewable and fossil-fuel-based energies. When a power imbalance occurs in an MG, based on the governor free control (GFC), the output sharing and frequency of the MG are first determined by the inertial force and synchronization between distributed generators (DGs). Next, desired power-sharing and frequency recovery are performed by secondary frequency control (LFC) in the control mechanism of the MG. However, in interconnected microgrids (IMGs), not only loads (LDs) but also DGs are connected/disconnected arbitrarily, and it is difficult to analyze the synchronization forces and tie-line power accurately. Therefore, in this research, we constructed a frequency response model (FRM) of MG composed of various DGs with different inertias and time constants and applied the extended virtual synchronous generator (E-VSG) model to it. It was confirmed by the simulation that frequency nadir and recovery time could be significantly shortened by properly setting the parameters of E-VSG without interfering with those of the existing DGs. Furthermore, in a system in which three MGs are interconnected, even if there is no E-VSG in the MG where the power disturbance occurs, the similar effects by the EVSG in other MGs were confirmed due to the tie-line powers. (C) 2020 The Authors. Published by Elsevier Ltd.