An Energy Absorbing Method for Hybrid MMCs to Avoid Full-Bridge Submodule Overvoltage During DC Fault Blocking

The full-bridge submodules (FB-SMs) in hybrid modular multilevel converters need to absorb the enormous energy stored dc side and arm inductors during fault blocking, which may lead severe overvoltage. An energy-absorbing branch (EAB) composed of metal oxide varistor (MOV) thyristors is proposed this letter. No extra power loss produced by EAB normal operation. can a part reduce absorbed FB-SMs suffering from overvoltage clamping voltage. Thus, maximum FB-SM reduced. Turning off several milliseconds after blocking converter accelerate decaying transmission line required volume MOV with minimal effect on shows better technical economic performance than existing methods. validated simulations experiments.