A photovoltaic three-phase topology to reduce common mode voltage

Abstract

At the present time most of the photovoltaic (PV) applications require to be integrated to the electrical grid. There are mainly two types of PV systems: with galvanic isolation (transformer) and transformerless. PV systems with low frequency transformer provide galvanic isolation from the grid. However, this transformer increases the losses, size and cost. On the other side, when the transformer is not included, the system can generate strong ground currents which are a function of the stray elements (capacitances). In this sense reducing the Common Mode Voltage (CMV), is an important issue in the design of power electronics converters for transformerless PV applications. In this paper a three-phase transformerless PV inverter with reduce common mode voltage is introduced. CMV is analyzed under different modulation schemes and an analysis of losses using a real model of the IGBT´s is included.