Solid State Bridge Type FCL and Novel DC Circuit Breaker for HB-MMC

Abstract

Voltage Source Converter (VSC) in comparison with conventional High Voltage DC system based on line commutated converter (LCC) has several advantages i.e. low power losses, high reliability and lower cost. In Voltage Source Converter topologies, Half Bridge Modular Multilevel Converter (HB-MMC) has been widely used but HB-MMC is vulnerable to large DC fault current due to their free-wheeling diodes. In this paper, Author proposes a bridge type solid state fault current limiter (BFCL) for DC fault current suppression and a novel DC circuit breaker for clearing fault instantly. The Solid State bridge type FCL confine fault current to 2 kA from its peak 14 kA value which shows 86% suppression in fault current. The Novel circuit breaker has been design to interrupt 10 kA and below 10 kA DC fault current with in 1.9 ms and when connect in series with Solid State Bridge type FCL, where fault current is above 10 kA, the interruption time is 7.1 ms. PSCAD/EMTDC simulation software is used to design HB-MMC, Solid State Bridge type FCL and Novel DC circuit breaker.