High-frequency dc solid-state transformer (DCSST) plays an important role in DC bus connection, voltage conversion, electrical isolation, and bidirectional power transmission in dc distribution networks. In various DSSCT topologies, the dual-active-bridge (DAB) scheme becomes a typical solution for DCSST due to its various advantages. However, the DAB scheme still has drawbacks during practical applications. In this article, a DAB with half-bridge submodules (HSDAB) is proposed. By replacing the switches in front bridge arm with half-bridge submodules (SMs), the proposed HSDAB scheme maintains the advantages of conventional DAB and obtains bidirectional dc fault-handling capability, reducing the application of large dc capacitors and dc circuit breaker; therefore, the volume and construction cost of DCSST can be effectively reduced. Besides, a high-frequency-link (HFL) voltage regulation strategy for HSDAB is also proposed in this article. The HFL voltages can be adjusted to match the HFL transformer voltage ratio during the whole operating range, reducing the current stress, HFL reactive power, and power loss of DCSST. Moreover, the proposed HSDAB scheme can also be applied as a basic circuit to establish multiple modular architecture DCSST, flexibly connecting low-voltage dc, medium-voltage dc, and high-voltage dc buses in the dc distribution network. The topology, operation principle, control structure, corresponding bidirectional dc fault handling, and HFL voltage regulation strategy of the proposed HSDAB scheme are investigated. The experimental results verify the correctness and effectiveness of the analysis and proposed scheme.

中文翻译：

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用于直流配电网的带有半桥子模块的双有源桥直流固态变压器

高频直流固态变压器（DCSST）在直流配电网络中的直流母线连接，电压转换，电气隔离和双向功率传输中起着重要作用。在各种DSSCT拓扑中，双有源桥（DAB）方案由于其各种优点而成为DCSST的典型解决方案。但是，DAB方案在实际应用中仍然存在缺陷。在本文中，提出了具有半桥子模块（HSDAB）的DAB。通过用半桥子模块（SM）替换前桥臂中的开关，提出的HSDAB方案保留了传统DAB的优点，并获得了双向dc故障处理能力，从而减少了大型dc电容器和dc断路器的使用；因此，可以有效地减少DCSST的体积和建造成本。除了，本文还提出了一种用于HSDAB的高频链路（HFL）电压调节策略。可以在整个工作范围内调节HFL电压以匹配HFL变压器的电压比，从而降低电流应力，HFL无功功率和DCSST的功率损耗。此外，所提出的HSDAB方案还可以用作建立多个模块化体系结构DCSST的基本电路，在直流配电网络中灵活地连接低压dc，中压dc和高压dc总线。研究了所提出的HSDAB方案的拓扑结构，工作原理，控制结构，相应的双向直流故障处理以及HFL调压策略。实验结果验证了所提方案的正确性和有效性。