DESIGN AND ANALYSIS OF DIFFERENT TYPES OF SINGLE-PHASE TRANSFORMERLESS GRID CONNECTED PV INVERTERS

Abstract

Most of the PV systems are designed with transformer for safety purpose with galvanic isolation. However, the transformer is big, heavy and expensive. Also, it reduces the overall efficiency of the conversion stage. Generally PV inverter with transformer will has less efficiency. To overcome these problems, transformerless PV system is introduced. It is smaller, lighter, cheaper and higher in efficiency. However, dangerous leakage current will flow between PV array and the grid due to the stray capacitance. The leakage current increases conducted and radiated electromagnetic interference, total harmonic distortion (THD) and losses. Moreover, injection of direct current (DC) to the grid will saturate the distribution transformer along the grid. To solve these issues, different conversion topologies have been proposed. This paper is to model several transformerless grid-connected PV inverter topologies. The operation and common mode performance of these topologies are compared and analyzed.