An Optimized H6-Type Single-Phase PV Inverter with Bi-Directional Quasi-Diode Clamping

Abstract

Transformerless inverters (TLIs) have become increasingly popular in single-phase distributed photovoltaic power generation systems due to the superiorities of their high efficiency, slighter volume, moreover lower cost than the one with the transformer. However, in the absence of a transformer, high-frequency common-mode voltage (CMV) brings about hazardous ground leakage current flow. To reduce the leakage current, plenty of TLI structures have been published in the works, and among them, H5, H6, and Heric topologies are the three topology’s very popular mainstays. The third has the highest efficiency but the worst CM behavior owning to the switches’ junction capacitances. Consequently, the CM leakage current may exceed the recommended limit. In this paper, an optimized HERIC inverter with a quasi-diode clamp structure, namely OHERIC-BQDC topology, is suggested, in that a bidirectional clamping based upon MOSFETs, but like a diode clamping without dead time, is added on the basic HERIC inverter to eradicate the common-mode voltage fluctuation in freewheeling periods. A Matlab/Simulink pattern is constructed to investigate the feasibility of the suggested approach. In addition, PSIM’s software package is used to confirm the effectiveness of the suggested HERIC-based inverter.