A simple 60-pulse voltage source inverter using voltage reinjection strategy to improve voltage harmonics for high-power local loads

Abstract

The voltage reinjection strategy is an effective solution to improve the voltage quality of the voltage source inverters for high-power applications. In this article, the fundamentals of voltage reinjection strategy are analyzed to reduce voltage harmonics of the output voltage. Then, a novel voltage reinjection circuit is proposed which can generate a 5-level voltage to be injected on the voltages of the DC sources. The reinjected voltage can create a 60-pulse voltage waveform for a three-phase load. Turn ratio optimization of the reinjection transformer has a significant effect on the improvement of the harmonic situation of the output voltage. Furthermore, the proposed reinjection circuit provides ZVS conditions for the main switches to reduce switching losses considerably. The simulation results indicate that the proposed reinjection circuit can reduce the output voltage THD to 3.16% without any type of filter or modulation, and the load variation does not have a considerable effect on the voltage quality. The experimental results approve the analytical trend and simulation process and also confirm the reinjection circuit performance. According to the results, the proposed method has generated a semi-sinusoidal voltage waveform with $TH{D}_V=3.78\%$ in the laboratory.