光伏系统中无变压器级联H桥逆变器的漏电流抑制方法

This article presents a leakage current mitigation method for a single-phase transformerless grid-connected cascaded full bridges’ (CFBs) inverter for photovoltaic (PV) systems. Cascade multilevel inverter (CMI) allows for feeding loads with multiple voltage levels, which reduces the total harmonic distortion (THD) when compared with typical inverters. Reducing the THD makes the filter size smaller, which contributes to improving the overall performance of the power converter. These advantages make CMI one of the best energy conversion systems for single-phase grid-connected PV applications. However, eliminating the transformer causes leakage current to flow through the ground, which is hazardous. To minimize the effect of leakage current, the common-mode voltage (CMV) is usually maintained constant at all modes of operation. In this article, a different method in the CFB grid-connected PV systems is proposed, based on the evolution of capacitor leakage voltage, which reduces the leakage current issue in each PV panel, not only for the total, as is typical in the multilevel converters. No topology modifications were made, and a traditional current controller may be used. An experimental prototype is designed and tested, with the experimental findings confirming the theoretical results.