Accurate Harmonic Calculation for Digital SPWM of VSI With Dead-Time Effect

Abstract

This article presents an accurate model of a digitally controlled voltage-source inverter with the dead-time effect. The impact of two nonlinear behaviors of digital sinusoidal pulsewidth modulation and dead time on the output waveform is analyzed in the time domain. The problematic waveform with sinusoidal pulsewidth modulation is displayed, which highlights the necessity of establishing a new model. In the frequency domain, considering the dead-time effect on the current double Fourier transform is used to give a harmonic expression without a current sign function. Furthermore, this avoids the error caused by the measurement of the current polarity, so the exact amplitude of each harmonic of the output voltage can be accurately calculated, which is important for eliminating specific harmonics and improving power quality. Moreover, the problem caused by the current zero crossing is solved. The result of the analysis is verified by simulation and experiment on DSP and SIC platform. And the result shows that the harmonics and their amplitudes are in good agreement with our formula.