Overvoltage Suppression in Initial Charge Control for DC Capacitor Using Multiple Leg Short-Circuits With SiC-MOSFETs in Power Converters

Abstract

This article proposes an improved overvoltage suppression method for the initial charge of the dc capacitor in voltage source power converters. The proposed method makes multiple short-circuits in each leg, utilizing power devices in the converter. These short-circuits discharge the dc capacitor and suppress overvoltage caused by resonant effects during the initial charge. The utilization of short durations of short-circuits multiple times in each leg reduces the power consumption in the power devices and results in a decrease in the peak junction temperature. Experimental verification using a 200-V, 5-kVA three-phase converter demonstrates that the proposed multiple short-circuit method reduces power consumption by 6% and suppresses device degradation by more than 40 times compared to the previously proposed single short-circuit method. The experimental results exhibit the effective overvoltage suppression capability of the proposed method with modest device degradation. As a result, the proposed method allows for the elimination of the initial charge circuit, leading to reductions in the size and cost of power converters, particularly in PWM rectifiers.

Keywords

• Electrolytic capacitorless power converter
• initial charge
• short circuit
• SiC-MOSFET