Review of common-mode voltage in transformerless inverter topologies for PV systems

Abstract

When a galvanic connection between the grid and the PV array is made, a common-mode voltage exists which generates common-mode currents. These common-mode currents may produce electromagnetic interferences, grid current distortion and additional losses in the system. Therefore, to avoid the leakage currents that would penalize the transformerless power chains, it is worth focusing on topologies which do not generate common-mode currents. Some topologies available in the market touch more or less such a crucial requirement. However, some drawbacks generated by the non-utilization of the line transformer still exist.This is said, a small room for improvement still exists. The first goalof this reviewis to focus on recently developed topologies which do not generate common-mode voltage. Analysis and simulation results show that the HERIC topology has higher efficiency and does not generate a common-mode voltage. The second goal is to present the different ways to reduce harmonics in the inverter output and to maximize the PV cells output power. © Springer-Verlag Berlin Heidelberg 2012.