H8 Inverter to Reduce Leakage Current in Transformerless Three-Phase Grid-Connected Photovoltaic systems

In this paper, a three-phase grid-connected photovoltaic (PV) topology (named H8) is proposed to address the leakage current issue. AC common-mode voltage and earth leakage current cause problems in the transformerless grid-connected PV systems. Leakage current increases the distortion of the current injected into the grid and the losses, also it generates unwanted radiated and conducted electromagnetic interference. The voltage source full-bridge inverter, which is also known as B6-type converter is widely used for three-phase PV systems. The B6-type inverter suffers from the leakage current, which limits its application to transformerless grid-connected PV systems. The proposed H8 topology reduces the leakage current as well as common-mode voltage variations through the separation of the PV array from the grid during the zero voltage states. Through analysis, simulations, and experimental results, a comparison between the proposed topology and the conventional B6-type topology is performed. Results validate the performance improvements of H8 inverter in terms of leakage current and total harmonic distortion of the output currents injected into the grid. Experimental results are presented for a 2-kW grid-connected PV system.