Research on Control Strategy of Four-Leg Inverter Under Unbalanced and Nonlinear Load

Abstract

The three-phase four-leg inverter can effectively solve the problem of asymmetric output waveform when the system is equipped with unbalanced and nonlinear loads. A mathematical model of the inverter can be established in a rotating coordinate system, and proposing a control strategy based on improved repetitive control. By decoupling the four-leg inverter into three single-phase inverters, closed-loop control of positive and negative zero-sequence components is achieved, ensuring the accuracy and dynamic stability of the system. A simulation using Simulink is designed on this technology and presented to verify the correctness and feasibility of the method. System using the method proposed in this paper has high output waveform quality under unbalanced, nonlinear, and sudden load changes. At the same time, it has strong unbalanced load capacity, good dynamic and static performance, and meets the requirements of industrial design.