A Leakage Current Eliminated and Power Oscillation Suppressed Single-Phase Single-Stage Nonisolated Photovoltaic Grid-Tied Inverter and Its Improved Control Strategy

Abstract

Single-phase single-stage nonisolated photovoltaic (PV) grid-tied inverters mainly suffer from issues of the common-mode leakage current and double-line-frequency power oscillation. Aiming to address these issues, this article designs a new single-phase PV grid-tied inverter with only two switches. The structure of the proposed inverter allows the neutral line of the alternating current (ac) grid to be directly connected to the negative pole of the PV panel so that the common-mode leakage current can be completely eliminated. Additionally, a power decoupling method is proposed to suppress the double-line-frequency power oscillation. Then an improved control strategy is presented in this article to solve the stability problem of the proposed inverter when it is connected to a weak grid. It should be noted that the designed inverter can also output reactive power, achieve zero-voltage switching, track the maximum power point, and step up the input voltage. The validity of the proposed inverter and improved control strategy is verified by simulation and experimental results.