Low Voltage Fault Traversal Control Strategy for DC Transformer Based on Voltage Balancing Circuit

Low voltage DC bipolar short circuit fault, as one of the most severe faults in DC transformer, may cause low-voltage overcurrent blocking of the converter in the DC transformer, and even damage power electronic power devices. This article studies a DC transformer topology based on voltage sharing circuit and analyzes the working mechanism of the new topology. Using this as a prototype, the discharge circuit of low-voltage short circuit faults is discussed and divided into two fault stages. A low-voltage fault traversal control strategy is proposed for the stage two discharge mechanism, which switches the control quantity from DC voltage to DC current. Combined with phase shift control modulation, the fault current can be limited within the threshold range. After fault recovery, the delay switches the control quantity from DC current to DC voltage, and the fault traversal control logic switches smoothly, making it easy for engineering applications. The simulation results verify the effectiveness and correctness of the low-voltage fault traversal control strategy proposed in this paper.