Design of Three-phase Four-leg Inverter Based on Modified Repetitive Controller

A design method based on modified repetitive control (MRC) for three-phase four-leg inverter was proposed,which can effectively suppress the output voltage disturbances caused by non-linear loads.To make better tradeoff between the performance and robustness of repetitive control,a low-pass filter with zero-phase-shift is added in the compensation unit to increase the freedom of repetitive control.The zero-phase-shift filter is optimized with the target of higher error attenuation rate and less complexity for the filter design.Robust stability for the system is taken into account as the restriction,and particle swarm optimization (PSO) is employed to optimize the filter.At last,MRC based on optimal and robust filter with zero-phase-shift was designed.In the proposed controller,error from system modeling is taken into account,so the controller is of great robustness,and it is convenient to be applied in industry.Carrier modulation strategy is used in the modulation layer for three-phase four-leg inverter,which maximizes the utilization of the DC voltage,and no more complicated data process is necessary.The theoretical analysis and experimental results on a prototype verify the correctness and feasibility of the proposed design method.