Solid-State Circuit Breaker Snubber Design for Transient Overvoltage Suppression at Bus Fault Interruption in Low-Voltage DC Microgrid

摘要

Under a short-circuit fault in low-voltage dc microgrid, solid-state circuit breaker (SSCB) assumes the responsibility of the quick and effective isolation of the faulted area, while its own safety and reliability depends on the overvoltage suppression ability of its snubber. For SSCB snubber design, however, traditional method suited for converter switch snubber cannot be directly applied, because SSCB snubber stresses more on its overvoltage suppression and fault current withstanding instead of snubber loss reduction. Therefore, this paper strives to build a snubber design method specialized for SSCB overvoltage suppression at bus fault interruption. A comprehensive and target-focused set of measurements is proposed and applied to the comparison of three RCD snubber candidates: charge-discharge type, discharge-suppressing type I, and discharge-suppressing type II. The set of measurements includes six indicators with peak SSCB voltage and peak bus current as the main indexes. After parameters are determined, the indicators of the three snubbers are compared, through which discharge-suppressing type I is selected as the most appropriate SSCB snubber. Experiments of the three snubbers have also been conducted in a ±200-V/dc system to verify the correctness of comparison results and the validity of discharge-suppressing type I for SSCB overvoltage suppression at dc-bus fault.