A Novel Leakage Current Reduction Method combining a PWM Method and Bypass Path with a Damping Network for Transformerless 3-Level Photovoltaic Power Conditioning System

摘要

In this paper, leakage current generation is analyzed through an equivalent model of the common mode voltage considering a significant parasitic capacitance existing between the photovoltaic array and ground, and combined two methods to reduce the leakage current, which are a new PWM method and leakage current bypass path with a damping network, are proposed. In the first, the leakage current is reduced significantly by a PWM method using two carriers with 180 degrees - phase difference without losing the voltage utilization rate. In the second, the leakage current is further reduced by adding a bypass path from LCL filter to the mid-point of DC link with a damping network. The combined two methods are verified by simulations and experiments with 1μF stray capacitance. The proposed method using the PWM method is verified to reduce the leakage current by 73% compared to the conventional SVPWM, and the bypass circuit with the damping network further reduces the leakage current by 93%, respectively.