Imbalance Compensation for SVPWM-Controlled Four-switch Three-phase Inverters

Four-switch three-phase (FSTP) inverters have been investigated as low-cost alternatives to traditional six-switch three-phase (SSTP) inverters for a variety of applications. However, voltage fluctuations at the DC link center tap can significantly degrade the performance of FSTP inverters, which leads to an imbalance in the inverter output. By analyzing the vector trajectory of the output voltage in FSTP inverters, this paper characterizes the imbalance and proposes an adaptive SVPWM algorithm to correct it. The method uses correction factors to adjust control parameters according to the real-time voltage at the DC link center tap. The proposed method is thoroughly discussed, both in terms of theoretical analysis and simulation verification. Experiment results are also presented to further validate the proposed method. As demonstrated by the results, the compensation method is effective even in the presence of substantial voltage ripples at the center tap.