Single-Stage Symmetrical Bipolar Multi-Port Converter Based on Cuk Voltage Balancer with Output Current Ripple Suppression for Bipolar DC Microgrid Applications

Bipolar DC microgrids have gained significant attention as a promising solution for their unparalleled efficiency and reliability. However, the asymmetric bus voltage caused by the uneven distribution of loads and generators between the two poles often restricts the stable operation of the bipolar DC microgrids. This paper presents a multiport converter with strictly symmetrical bipolar output voltages to interface various sources to bipolar buses. By combining the half-bridge rectifier and the Cuk voltage balancer, single-stage power conversion is achieved, and the cost and efficiency are greatly improved. To further suppress the output current ripple, the positive and negative polarity ports are integrated through coupled inductors, which greatly reduces the size of the magnetic components and filter capacitors, thereby increasing the power density. Furthermore, the wide-range soft-switching operation, bidirectional power flow capability, and simple control all make the proposed converter an excellent candidate for bipolar dc microgrid system applications. The topology derivation process, operation principle, steady-state characteristics, bipolar port current ripple, soft-switching conditions, design consideration, loss distribution, control method, and performance comparison are deeply analyzed in this paper. A 2-kW rated laboratory prototype is designed to convert 160 V input to ±200 V output. The experimental results agree well with the theoretical analysis.