Analysis and design of an energy regenerative snubber for magnetically coupled impedance source converters

Abstract

Magnetically coupled impedance source (MCIS) converters are prone to high voltage spikes across the inverter bridge (or dc-link) due to the presence of leakage and stray inductances in the high frequency loop. The problem manifolds because of a shoot-through state in impedance source converters, which avoids application of a decoupling dc-link capacitor. This makes the impedance source converter less attractive for industry applications despite of its merits over the conventional voltage-fed and current-fed inverters. Only few attempts have been made in the literature to solve this problem, but the solutions are not generic (i.e. structure-oriented) and they are quite lossy with intuitive modification in the circuit itself, resulting in significant changes in the performance of the power converter (e.g. increase in components stresses). To address this concern, a general passive regenerative inductor-capacitor-diode (L-C-D) snubber is presented in this paper for all MCIS converters without any modification in the original circuit. The proposed circuit rechannel the leakage energy of the coupled magnetics and feedback it to input or network itself, which does not only avoid extreme voltage spikes across the inverter bridge but also improves the efficiency of the system. In this paper, the analysis of the proposed snubber is introduced with simulation results and experimental implementation of the proposed snubber in a 500 W three-phase quasi-Y-source inverter (qYSI) to verify the efficacy of the proposed solution.