Analysis and Solution of Current Zero-Crossing Distortion With Unipolar Hysteresis Current Control in Grid-Connected Inverter

In this paper, a kind of zero-crossing distortion (ZCD) generated in the grid-connected current of a single-phase grid-connected inverter with unipolar hysteresis current control is investigated. By establishing the mathematical model of the grid-connected inverter around the zero-crossing points (ZCPs), the reason for causing the current ZCD is presented. It is ascribed to the slope of the actual current less than that of the reference one around the ZCPs. The expressions of the critical phase angle (the starting point of the current ZCD) and the amplitude of the current distortion corresponding to the parameters of the inverter and connected utility grid are obtained, and the solution for the ZCD based on on-line leading phase angle compensation is proposed. Simulation and experimental results verify the accuracy and feasibility of the theoretical analysis and the proposed solution.