Low leakage current single-phase PV inverters with universal neutral-point-clamping method

Abstract

The transformerless inverters have the advantages of low cost and high efficiency, which attract more attentions in the field of photovoltaic (PV) power generation system. However, the transformerless grid connected system has the main challenge for keeping low leakage current due to the non-isolation configuration. To better attenuate the leakage current in single-phase system, a few of neutral point clamped (NPC) topologies have been proposed. This paper further proposes a kind of universal neutral point clamping method to build the single-phase NPC PV inverters, which only employs one additional switch to connect the midpoint of dc link and the circulating circuit. Since only the leakage current flows through the additional switch, the single-phase NPC inverter could still maintain the high operational efficiency with the significantly attenuated leakage current. The working principles of the proposed method and the corresponding NPC inverters are analyzed in detail. The simulation and experimental results verified the theoretical findings.