Transformerless Grid-Connected Asymmetric PV Inverter with Constant CMV and Reactive Power Injection Capability

Abstract

Transformerless inverters have been commonly used in grid-connected photovoltaic (PV) systems due to their high power density, low weight and volume, and high efficiency. However, they also suffer from the issue of leakage current. On the other hand, the ability to inject reactive power is another challenge of transformerless grid-connected PV inverters. In order to reduce leakage current and provide reactive power injection (RPI) capability, a single-phase transformerless grid-connected asymmetric phase-legs PV inverter is presented in this paper. The proposed inverter improves the conventional hybrid phase-legs PV inverter, ensuring that the common-mode voltage (CMV) is always constant. As a result, the high-frequency CMV is avoided, and the leakage current is diminished. Also, the proposed inverter has the same performance in the grid power factor of unity and non-unity. In order to validate the operation of the proposed PV inverter, the simulation results are presented and compared with the conventional hybrid phase-legs inverter based on a 1 kW sample.