Theoretical Analysis of Harmonics in PWM Output Waveform of Multi-Level Inverters

Abstract

Multi-level inverters have very attractive features such as lower harmonics in the output, lower EMI, and reduction of the required voltage rating of power semiconductor devices. Among them, lower harmonics in the output can reduce the volume of the output harmonic filter and additional losses caused by the harmonics. Therefore, multi-level inverters are expected to realize higher power density and higher efficiency. In this paper, as a basis of the quantitative investigation of these features, the harmonics in the PWM output voltage of multi-level inverters are analyzed theoretically. As an application of the theoretical results, the usefulness of the theoretical results is verified by the prediction of the harmonic contents of the load current.