Analysis of the DC-Link Voltage Ripple for the Three Phase Voltage Ripple Under Low Order Harmonic Output Current

Abstract

This paper presents a general analytical method of the dc-link voltage ripple to facilitate the dc-link capacitor design for the three phase voltage source converters (VSCs) under harmonic ac currents. The expressions of the dc-link low order harmonic (LOH) voltages and switching harmonic voltages (SRVs) are derived, respectively. Moreover, a simple and practical equation for designing the dc-link capacitor, based on the maximum value of the dc-link voltage ripple, has been proposed. A flexible grid-tied inverter lab prototype is developed to inject arbitrary combinations of LOH currents of different orders, sequences, amplitudes and angles into the grid. Good match between the computational and experimental results validates the proposed methods.