Feasibility study of DC circuit breaker-less MTDC systems

This paper discusses the feasibility of clamp double submodule (CDSM) type modular multilevel converter-based multiterminal high-voltage direct current (MTDC) systems. Firstly, the MTDC system structures, the topology of CDSM, the DC fault current blocking capability of CDSM, and the possible control scheme for clearing DC fault with CDSM-type modular multilevel converters are introduced. Based on the DC fault clearing control scheme, the DC fault impact on the connected AC system with the proposed method is analyzed in detail. Two types of test systems are built for this study, including the MTDC systems with 1 DC backbone and 2 DC backbones suitable for different occasions. The simulation waveforms are compared with those containing high-voltage direct current circuit breakers. The results show that the connected AC system postfault responses do not diverse too much with the 2 configurations, which proves the feasibility of the DC circuit breaker-less MTDC system.