Circulating Resonant Current Between Phase-leg DC-link Capacitors for Single-phase Full-Bridge Inverter

Abstract

A design for an inverter circuit configuration of integrated half-bridge modules with focus on the circulating resonant current is clarified in this paper. Although this configuration has the advantages of a small DC-side stray inductance, an analysis of the equivalent circuit suggests that the DC-link capacitor current increases depending on the relationship between the resonant and switching frequencies. This leads to an increase in the capacitor volume. The capacitor current was experimentally investigated under PWM operation at switching frequencies up to 100kHz using SiC-MOSFETs. The experimental results demonstrate that the resonant current is remarkable when the resonant frequency was close to either the fundamental or the third harmonics of the switching frequency. Using the proposed design considering the quality factor and the resonant frequency, the increase in the capacitor current based on the resonant phenomenon can be avoided.