Hybrid-Modulation Hysteresis Scheme Based Decoupled Power Control of Grid-Connected Inverter

Abstract

Most existing power control methods for grid-connected inverter are implemented in synchronous reference frame. In order to achieve soft-switching operation, those methods usually need additional design considerations, which could introduce complex computation. This article presents a control strategy for single-phase grid-connected inverter system with LCL filter that can be used for grid-connected battery/photovoltaic (PV) system, with the target to implement decoupled active and reactive power control capability in stationary frame and achieve soft-switching behavior for higher efficiency. In order to improve system efficiency, a new hybrid-modulation-based hysteresis current scheme is used to achieve soft-switching while improving the inherent zero-crossing distortion issue existing in traditional unipolar hysteresis current control. Multiproportional and resonant compensators are utilized to mitigate output low-frequency distortions further, together with a capacitor current feedback-based active damping design embedded in an inner loop. The proposed controller also demonstrates good robustness and immunity to distorted grid conditions. Simulation and experimental results are presented in this article with essential theoretical analysis to verify the validity of the proposed control strategy.