Interline DC Power Flow Controller with Fault Current Limiting Function

When a fault occurs in the DC power grid, the current increases rapidly, which endangers the safe operation of the entire system. The DC breaker used to cut off the fault current has a limited breaking capacity, which needs to work with the fault current limiter. With the increasing complexity of the DC power grid structure, the problem of power flow control is increasingly prominent. Based on the original power flow control capability of the DC power flow controller, this paper explores its fault current limiting capability and proposes a novel topology of the interline DC power flow controller with fault current limiting capability. The power flow control part adopts the interline DC power flow controller, and the fault current limiting part adopts thyristors to control the inductor into service, which realizes the current limiting. The working principle, operation process and theoretical analysis of the proposed controller are investigated, and simulation verification is performed in the single-terminal equivalent system and the four-terminal flexible DC power grid. The simulation results show that the controller can control the power flow of two lines during the normal operation, limit the fault current when a pole-to-ground fault occurs on the line, and complete the clearance of the fault current by cooperating with DC circuit breaker. The feasibility and effectiveness of the device and the control strategy are verified. © 2020 Automation of Electric Power Systems Press.