In order to suppress leakage current and improve the efficiency of the transformer-free grid-connected inverter, a novel topology and control method is proposed. The proposed inverter consists of a power inverter unit and an auxiliary converter unit, and the two units are connected by a capacitor on the dc side. The power inverter unit transmits power to the grid at a low switching frequency for reducing power losses. The auxiliary converter unit operates at a high switching frequency, and adopts a feedforward control method to eliminate the grid current switching ripples. The voltage of parasitic capacitance between the photovoltaic array and the ground is stabilized by the auxiliary converter unit with the bipolar modulation scheme, so the leakage current can be suppressed more effectively. A 1-kW prototype was built and tested, and the experimental results are finally presented to show the performance of the proposed inverter.

中文翻译：

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无变压器双频并网逆变器拓扑及控制方法研究


为了抑制漏电流并提高无变压器并网逆变器的效率，提出了一种新颖的拓扑和控制方法。所提出的逆变器由功率逆变器单元和辅助变流器单元组成，这两个单元通过直流侧的电容器连接。功率逆变器单元以低开关频率向电网传输功率，以减少功率损耗。辅助变流器单元工作在高开关频率下，并采用前馈控制方法来消除电网电流开关纹波。辅助变流单元采用双极调制方案稳定光伏阵列与地之间的寄生电容电压，因此可以更有效地抑制漏电流。建造并测试了 1 kW 原型机，最终提供了实验结果以展示所提出的逆变器的性能。