A voltage-clamped bidirectional fault current limiter based on a three-winding coupled inductor for DC power grids

The DC fault is a serious challenge to voltage-source-converter-based HVDC (VSC-HVDC) systems, and the fault current limiter (FCL) is one of the key measures to solve the DC fault and reduce the capacity of the DC circuit breaker. This paper proposes a voltage-clamped bidirectional fault current limiter (VCB-FCL) based on a three-winding coupled inductor. During normal operation, the reverse magnetic coupling of the windings gives the VCB-FCL a low inductance, resulting in minimal impact on system dynamic performance. After the fault occurs, the IGBTs control the windings with the same magnetic flux direction to conduct the fault current, rapidly increasing the equivalent inductance, and the metal oxide varistor (MOV) in VCB-FCL is conducted. It can effectively limit the current through the voltage clamping effect of the MOV. Based on the analysis of the working principle and parameter design of VCB-FCL, simulation and experiment are carried out, and its good performance is verified. Compared with DC reactors, the amplitude of fault current decreases by 54.8 %, the interruption time is reduced by 1.2 ms, and the energy dissipation of the MOV is reduced by 57.0 %. Compared with other FCLs, the proposed VCB-FCL exhibits better performance in bidirectional current limiting, system dynamic response, interruption time, MOV energy dissipation, and cost. The simulation and experimental results show that VCB-FCL is not only feasible in principle but also has outstanding advantages in performance compared to other current limiting methods.