Leakage current suppression and ripple power reduction for transformer-less single-phase photovoltaic inverters

Abstract

Transformer-less single-phase grid-tied inverter is attractive due to low cost, high efficiency, and small size. However, leakage current and second-order ripple power have to be well dealt with. Because the leakage current is a potential threat for body safety and the ripple power will decrease overall efficiency and system reliability. Both issues become obstacles for practical applications. This paper proposes a method to achieve leakage current suppression and ripple power reduce simultaneously. The main circuit is formed by adding an extra arm and a decoupling capacitor to the traditional single-phase voltage source inverter. The additional arm is controlled to keep the common voltage constant and divert the ripple power to the decoupling capacitor. A decoupled control method is also developed to achieve independent control of power factor correction and power decoupling. Finally, simulation results are presented to show the effectiveness.