As a core piece of equipment in DC distribution networks, DC solid-state transformers (DCSSTs) are attracting more and more attention in academia and industry. Due to the limitations in terms of the electrical stress of the switches, the input series output parallel (ISOP) structure is adopted in DCSSTs. This paper proposed an improved DCSST topology based on a voltage balancing unit (VBU). This topology has the advantages of higher power density, reduced weight, and cascaded number without compromising efficiency, cost, or reliability. The working modes, mathematical models, and control strategy are analyzed. In addition, a start-up strategy and a parameter design method are proposed in this paper. Simulation and experimental results verify the correctness and effectiveness of the proposed solution. The proposed DCSST is a practical scheme for the application of DC distribution networks.

作为直流配电网络中的核心设备，直流固态变压器（DCSST）在学术界和工业界正受到越来越多的关注。由于开关的电应力方面的限制，DCSST中采用了输入串联输出并联（ISOP）结构。本文提出了一种基于电压平衡单元（VBU）的改进的DCSST拓扑。这种拓扑结构的优点是功率密度更高，重量更轻，级联数量不降低效率，成本或可靠性。分析了工作模式，数学模型和控制策略。此外，本文提出了一种启动策略和参数设计方法。仿真和实验结果验证了所提方案的正确性和有效性。