A single-phase symmetric-bipolar-type high-frequency isolated buck-boost ac–ac (SBT-HFI-BBAC) converter is proposed. The converter is composed of two full-bridge inverter modules, input/output LC filters, and a high-frequency transformer (HFT) with series capacitors. It can provide identical noninverting and inverting buck-boost output voltages with symmetric-bipolar voltage gains of ±D/(1−D) \pm D/({1 - D}). The frequency of the output voltage can also be adjusted in discrete steps, similar to single-phase matrix converters (MCs). It supplies continuous input and output currents and works well with nonunity power factor loads. The magnetizing current of the HFT has no line frequency component due to the presence of the series blocking capacitors. Moreover, due to the absence of ac switches, the converter has a simple commutation process, unlike conventional ac-ac/MCs. Two switching strategies are proposed; Strategy-I with fewer high-frequency switches and Strategy-II with reduced switch currents, providing more flexibility in switch power loss optimization. The proposed SBT-HFI-BBAC converter is well suited for application as a dynamic voltage restorer, compensating a wide range of grid voltage sags and swells, without the need for a low-frequency voltage injection transformer. Its step-changed frequency operation can also find use in various applications, such as high-gain ac–dc converters, traction systems, etc. A comprehensive description of circuit operation is presented along with component design guidelines and appropriate comparisons. Experimental verification results are provided using a 400-W laboratory test circuit.

中文翻译：

---

具有连续输入和输出电流的单相对称双极型高频隔离降压-升压 AC-C 转换器


提出了一种单相对称双极型高频隔离降压-升压交流-交流（SBT-HFI-BBAC）转换器。该转换器由两个全桥逆变器模块、输入/输出LC滤波器和一个带有串联电容器的高频变压器（HFT）组成。它可以提供相同的同相和反相降压-升压输出电压，对称双极电压增益为 ±D/(1−D) \pm D/({1 - D})。输出电压的频率也可以分步调整，类似于单相矩阵转换器 (MC)。它提供连续的输入和输出电流，并且适用于非单位功率因数负载。由于串联隔直电容器的存在，HFT 的磁化电流没有线路频率分量。此外，由于没有交流开关，该转换器的换向过程简单，与传统的交流-交流/MC 不同。提出了两种切换策略；策略 I 具有更少的高频开关，策略 II 具有更少的开关电流，为开关功率损耗优化提供了更大的灵活性。所提出的 SBT-HFI-BBAC 转换器非常适合用作动态电压恢复器，可补偿大范围的电网电压骤降和骤升，而无需低频电压注入变压器。其阶跃频率操作还可用于各种应用，例如高增益交流-直流转换器、牵引系统等。本文提供了电路操作的全面描述以及组件设计指南和适当的比较。使用 400W 实验室测试电路提供实验验证结果。