Chengjia Zhang, Xiaodong Yang, Lijian Ding, Yue Yang, Helong Li, Zhiqing Yang, Qiuwei Wu, Jinyu Wen
This letter introduces the direct current soft open point (DC-SOP), which is a bipolar DC-DC converter designed to achieve independent four-quadrant power flow control in bipolar DC distribution networks (BDDNs). For the first time, asymmetric dual active bridges are employed to connect the four-quadrant ports, ensuring a flexible power channel to realize flexible power transfer between branches and poles. Bidirectional shift modulation strategy and four-quadrant decoupling facilitate independent power control, effectively mitigating branch overload and inter-pole power unbalance. To improve model linearization accuracy, a refined relaxation method is proposed, providing theoretical guidance for DC-SOP applications in BDDNs. The effectiveness of the proposed method is validated in ±10kV BDDNs with 33 nodes and 123 nodes.