LQR-based Optimal Current Control of Grid-Forming Inverter under Load Fluctuation

Abstract

This paper proposes a linear quadratic regulator (LQR)-based optimal current control to enhance the response speed and robustness of the inner current control loop of grid-forming inverters (GFMI). The GFMI enables grid frequency support through rapid active power delivery, which is directly related to the response speed of the inner current control loop. Simulation results show that the proposed method achieves an inner current control loop response with a settling time 0.82 seconds faster and an overshoot reduced by 6% compared to the conventional PI-based current control. Consequently, the frequency nadir increased by up to 0.003 Hz, and the rate of change of frequency (RoCoF) decreased by up to 0.035 Hz / s, demonstrating enhanced frequency response characteristics.