Distributed generation systems integrated into the modern electrical grid demand novel circuit architectures that can combine high efficiency and high power density together. The transformerless highly efficient and reliable inverter concept (HERIC) topologies are notable due to their mitigated leakage current concerns, constant common-mode voltage, and high efficiency. Nonetheless, the HERIC-based structures feature a maximum of three-level ac output voltage, forcing the conversion system to integrate large output filters to meet the grid codes. This article introduces a novel HERIC active-clamped converter with bidirectional power flow and full reactive power capabilities that can achieve five-level output voltage. This is accomplished by means of a phase-shifted pulsewidth modulation technique that effectively doubles the apparent switching frequency of the inverter and improves the quality of the injected ac power. Consequently, the topology can achieve higher power conversion efficiency, while using the same or a smaller output filter. To verify the feasibility of the proposed converter, a 2.5-kW SiC-based prototype was built and tested in the laboratory under different operation conditions.

中文翻译：

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具有全无功功率能力的 5 级 HERIC 有源钳位逆变器，适用于并网应用

集成到现代电网中的分布式发电系统需要能够将高效率和高功率密度结合在一起的新型电路架构。无变压器的高效可靠逆变器概念 (HERIC) 拓扑因其减少的漏电流问题、恒定的共模电压和高效率而引人注目。尽管如此，基于 HERIC 的结构具有最大三电平交流输出电压，迫使转换系统集成大型输出滤波器以满足电网规范。本文介绍了一种新型 HERIC 有源钳位转换器，具有双向功率流和全无功功率能力，可实现五级输出电压。这是通过相移脉宽调制技术实现的，该技术有效地将逆变器的表观开关频率加倍，并提高了注入交流电源的质量。因此，该拓扑可以实现更高的功率转换效率，同时使用相同或更小的输出滤波器。为了验证所提出转换器的可行性，构建了一个 2.5 kW 碳化硅基原型，并在实验室中进行了不同运行条件下的测试。