Calculation and Spectral Analysis of DC-Link Current for three phase PWM inverter

Due to the effect of high-frequency switches, the dc-link current of the PWM inverter contains a large number of harmonic components, which results in ripple fluctuations of dc bus voltage and directly affects the quality and reliability of the power supply system. According to the Double Fourier Series method, we deduce the expressions of the dc-link current, which include the low frequency and high frequency parts. Besides, the effect of the output current harmonics on the dc-link current is considered, which improves the accuracy of the expression. Based on the derived expressions, we quantize the spectrum of the dc-link current. From the view of magnitude, we deduce the specific harmonic distribution in the frequency domain. The quantized spectrum of dc-link current provides the guideline for the dc filter design, which can reduce the system volume and cost. Finally, the theoretical analysis of dc-link current is verified by the Fast Fourier Transform analysis results obtained by the simulation model platform.