HR Control Strategy Based on Phase Compensation for LCL Grid-Connected Inverters in Weak Grid

Abstract

With the large-scale development of renewable energy, distributed power generation represented by voltage source type grid-connected converters with inductor-capacitor-inductor (LCL) filter is increasingly used in power systems. Aiming at the problem that the increase of grid impedance in the weak grid reduces the system bandwidth, which leads to the instability of multiple harmonic resonant (HR) control, this paper proposes an improved HR current control strategy for LCL grid-connected inverters. The traditional HR control is improved by phase compensation to avoid the $\boldsymbol{-\pi}$ line crossing caused by the sudden phase change. The weak grid adaptability of traditional and phase-compensated HR control is analyzed and simulated respectively. And the results shows that the current THD is only 1.57% with improved HR control when the weak grid inductance is 3mH, which can effectively improve the system stability and robust performance under weak grid conditions.