IGBT Based and Parallel RL Fault Current Limiters for HB-MMC

Half Bridge Modular Multilevel Converter (HB-MMC), a sub-module of modular multilevel converter (MMC), is widely accepted voltage source converter (VSC) topology for high voltage DC (HVDC) systems. HB-MMC has a disadvantage that it did not limit, clear DC fault current and protect IGBT converter from damage. For confining DC fault current, it is necessary to place fault current limiter (FCL) in series with HB-MMC. In this paper, Author presents two novel fault current limiter i.e. IGBT based fault current limiter (IGBT-FCL) and Parallel RL fault current limiter. IGBT based FCL consists of IGBTs and diode which are connected in parallel to each other. IGBT based FCL perform two functions i.e. it circumscribe large DC fault current and also clear DC fault current. The RL circuit has connected in series with HB-MMC. Due to no zero crossing point in DC systems, Hybrid DC circuit breaker (HDCCB) has been connected in series with Parallel RL and HB-MMC to clear the fault instantly. IGBT based FCL confine the fault current to 4 kA from 14 kA which is 72% reduction in fault current and clear fault current within 14 ms. The parallel RL circuit confines the fault current to 3.6 kA from 14 kA which shows 75% suppression of maximum DC fault current. With the help of HDCCB, the fault is cleared within 18 ms. The PSCAD/EMTDC has been used for designing of HB-MMC, IGBT-FCL, Parallel RL circuit and HDCCB.