适用于双极性低压直流微电网的自平衡隔离型DC-DC变换器

Self-balancing isolated DC-DC converter for bipolar low voltage DC microgrid

双极性结构低压直流配电系统具有负荷灵活接入、运行可靠性高等优势。为了最大限度地减少功率变换级数并提升双极母线电压平衡能力,提出了一种适用于双极性低压直流微电网的自平衡隔离型DC-DC变换器。首先,介绍了自平衡隔离型DC-DC变换器的拓扑结构与调制策略,并分析了不平衡负载情况下正负极性直流电压自平衡机理及其换流过程;然后,结合零电压开关工作原理与输出电流纹波要求,对平衡电感参数进行优化设计,并推导了不平衡负载直流偏置引起的中性点电位偏移量;最后,搭建了一套实验样机验证了所提变换器在两直流极不平衡负载下甚至其中一直流极空载下可平衡双极母线电压。

The bipolar low voltage DC distribution system has the advantages of flexible load access and high operation reliability. In order to minimize the number of power conversion stages and improve the voltage balance ability of bipolar buses,a self-balancing isolated DC-DC converter suitable for bipolar low voltage DC microgrid is proposed. Firstly,the topology and modulation strategy of self-balancing isolated DCDC converter are introduced,and the self-balancing mechanism and commutation process of positive and negative pole DC voltages under unbalanced load conditions are analyzed. Then,based on the working principle of zero voltage switching and the requirement of output current ripple,the design of balance inductance parameters are optimized,and the neutral point potential offset caused by unbalanced load DC bias is derived. Finally,an experimental prototype is built to verify that the proposed converter can balance the voltages of the bipolar buses under the conditions of the unbalanced load of two DC poles or even the noload of one DC pole.