Three-phase transformerless inverter for photovoltaic grid connected system with zero common mode noise

Abstract

The pervasion of transformerless grid connected photovoltaic (PV) inverters has triggered the concerns of many researchers since it can induce power quality problems. In these types of applications, the generation of common mode (CM) leakage current is one of the major factors that affects the reliability of the overall design. In single-phase systems, the concept of the common ground between the PV negative terminal and the neutral point of the grid is the only topology that “totally” cancels this CM noise. However, none of the existing three-phase inverter techniques is able to totally remove it. Therefore, this paper proposes a three-phase PV inverter based on the concept applied in the single-phase system in order to achieve, for the first time, a zero CM noise in three-phase grid-connected PV applications. The proposed inverter is simulated with a PV array, appropriate modulation technique, corresponding inverter controller, and a three-phase Y-connected alternating current (AC) grid voltage. The simulation of the overall system is done using Matlab/Simulink software. As compared with results of existing three-phase topologies, this is the only three-phase transformerless PV inverter technique that offers generation of multilevel output, total elimination of leakage current flow, simple inverter structure, and uncomplicated modulation technique.