Implementation of Transformerless PV Inverters for leakage current reduction

Abstract

Today, the power demand increases tremendously due to the rapid growth of human population and fast-growing industries. As a result, CO2 emissions are increasing substantially, which results in newlineglobal warming. These problems can be mitigated via renewable energy sources such as photovoltaic (PV) energy because it is pollution free, green and inexhaustible. Therefore, global installation of PV system has been increasing in recent decades. Grid connected PV systems are classified into two types, namely with transformer and without transformer. Generally, a high newlinefrequency transformer is employed on DC side or low frequency transformer on the AC side of the system. The transformer provides galvanic isolation which guarantees the safety. However, PV inverter with a transformer is bulky, heavy and low efficiency. In order to newlineresolve these issues, PV inverter without using a transformer, also known as a Transformerless PV (TPV) inverter has been introduced. Nonetheless, there is no galvanic isolation in TPV inverter which newlineresults in dangerous leakage currents flowing between the PV array and the grid. Therefore, single-phase TPV inverters are investigated in this thesis. Generally, common mode voltage is the key factor to limit the ground leakage current. Therefore, a simple common model circuit newlinehas developed here to study the common mode behaviour of TPV inverters. According to that, several types of TPV inverters are examined, i.e., single-phase full-bridge neutral point clamped (NPC) inverters and three phase inverters.