Novel hybrid fault current limiter with hybrid resonant breaker in multi-terminal HVDC transmission system

In practical high voltage direct current (HVDC) transmission systems, the current is considerably high when a fault occurs in the dc line. This current must be limited to make its blocking techno-economically feasible by dc circuit breakers. This paper proposes a new hybrid fault current limiter (HFCL) that is placed and examined together with a hybrid resonance type dc circuit breaker in a four-terminal modular multi-level converter (MMC)-based HVDC transmission system. HFCL consists of an inline fast mechanical switch and parallel fault current limiting inductor (FCLI) with a series thyristor-controlled resistor. Since the FCLI is placed offline and on the other hand, in regular operation, the thyristors are in the off mode which prohibits the losses of conventional inline FCLI in the literature. The operation principle and design theory are presented. In order to clarify the effectiveness of the proposed HFCL, a simulation is carried out in MATLAB Simulink software, and the results are provided and discussed. It is verified that by applying the proposed fault current limiter, the peak of fault current is extremely limited, and the dc breaker obtains the efficient current blocking.