In this paper, a T-type common ground transformer-less single phase inverter with dynamic swing of the dc-link voltage is presented for photovoltaic (PV) application. The topology is a combination of a bi-directional, partial-power-processing boost stage and an asymmetric half-bridge inverter stage along with a T-branch. It takes advantage of the three-level switching states with reduced voltage stress on the main switches to achieve lower switching loss and almost one-half the inductor current ripple w.r.t. two level implementation. The double line frequency power decoupling is addressed by a dynamic dc-link approach, which allows a large swing of the dc-link to reduce the decoupling capacitor requirement, enabling an all-film capacitor implementation. This topology also significantly reduces the high-frequency capacitive coupled ground current by directly connecting the PV negative terminal to the grid neutral. Moreover, an adaptive dc-link voltage control scheme that optimally changes the average value of the dc-link voltage as the operating conditions (load and power factor) vary, has been proposed and thoroughly investigated from the perspective of better utilization of passive components and further reduction of switching losses. A SiC MOSFETs-based 1 kVA laboratory prototype has been built to validate the converter's operation at 200 V dc nominal input and 120 V/60 Hz ac nominal output with a wide range of power factor and load operations. Extensive experimental results validate the superior performance of the topology with the adaptive dc-link voltage control implementation showing a peak efficiency of 98.22% and a CEC efficiency of 98.03% at 50 kHz switching frequency.

中文翻译：

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具有集成功率去耦功能的单级共地三电平光伏逆变器

本文提出了一种具有直流链路电压动态摆幅的T型公共接地无变压器单相逆变器，用于光伏（PV）应用。该拓扑结构是双向的，部分功率处理的升压级和不对称的半桥逆变器级以及T分支的组合。它利用三级开关状态降低了主开关上的电压应力，从而实现了更低的开关损耗，并且实现了两级实施，电感电流纹波几乎减少了一半。双线频率功率去耦通过动态dc链路方法解决，该方法允许dc链路大幅度摆幅以减少去耦电容器的要求，从而实现全膜电容器的实现。通过直接将PV负极端子连接到电网中性点，该拓扑还显着降低了高频电容耦合接地电流。此外，已经提出了一种自适应直流链路电压控制方案，该方案可随着工作条件（负载和功率因数）的变化而最佳地改变直流链路电压的平均值，并从更好地利用无源组件和改进角度进行了深入研究。进一步降低开关损耗。已经建立了一个基于SiC MOSFET的1 kVA实验室原型，以验证转换器在200 V dc标称输入和120 V / 60 Hz ac标称输出下的运行，并具有多种功率因数和负载运行。