This study proposes single-phase improved coupled-inductor (CL) Z-source (ZS) ac–ac converters with integrated high-frequency transformer (HFT) isolation. They can provide wide range of buck–boost voltage with same/reversed phase angle, similar to the existing ZS ac–ac converters. Meanwhile, integrating a HFT with CL in proposed converters benefit in two-fold: (i) the CL enhances the voltage gain, which in turn reduces the voltage stresses/ratings of active switches. Moreover, the turns ratio of CL add another degree of freedom to gain adjustment beside the duty ratio; (ii) the HFT (20 kHz) is integrated with CL by adding only one winding to the same magnetic core, which provides electrical isolation for applications such as dynamic voltage restore, saving extra bulky line frequency (60 Hz) transformer. In addition, the proposed converters provide both continuous input/output currents. The commutation strategy is also implemented to eliminate the switch voltage spikes. A proposed HFT isolated improved three-winding Δ-CL ZS (Δ-ZS) ac–ac converter is introduced at first, and its operation, circuit analysis and component design/selection are discussed in detail along with comparisons with counterpart converters. Various different CL structures based proposed HFT isolated ZS ac–ac converters are presented afterwards. Experimental results on 200 W prototype converter are provided finally to verify their merits.

中文翻译：

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单相隔离高频变压器系列，集成了改进的磁耦合Z源ac-ac转换器

这项研究提出了具有集成高频变压器（HFT）隔离的单相改进型耦合电感（CL）Z源（ZS）ac-ac转换器。与现有的ZS ac-ac转换器类似，它们可以提供相同或相反相位角的宽范围的降压-升压电压。同时，在建议的转换器中将HFT与CL集成在一起有两个好处：（i）CL增强了电压增益，从而降低了有源开关的电压应力/额定值。而且，CL的匝数比除了占空比之外还增加了另一种自由度来进行增益调整；（ii）HFT（20 kHz）通过仅在同一个磁芯上增加一个绕组而与CL集成在一起，从而为诸如动态电压恢复之类的应用提供电隔离，从而节省了额外庞大的线路频率（60 Hz）变压器。此外，建议的转换器提供连续的输入/输出电流。还实施了换向策略以消除开关电压尖峰。首先介绍了一种建议的HFT隔离式改进型三绕组Δ-CLZS（Δ-ZS）ac-ac转换器，并详细讨论了其工作，电路分析和元件设计/选择以及与同类转换器的比较。随后介绍了基于不同的CL结构的HFT隔离ZS ac-ac转换器。最后提供了200 W原型转换器的实验结果，以验证其优点。详细讨论了电路分析和元件设计/选择，并与相应的转换器进行了比较。随后介绍了基于不同的CL结构的HFT隔离ZS ac-ac转换器。最后提供了200 W原型转换器的实验结果，以验证其优点。详细讨论了电路分析和元件设计/选择，并与相应的转换器进行了比较。随后介绍了基于不同的CL结构的HFT隔离ZS ac-ac转换器。最后提供了200 W原型转换器的实验结果，以验证其优点。