A New Common-Mode Transformerless Photovoltaic Inverter

Transformerless inverters are being widely used in grid-connected photovoltaic (PV) generation systems. Transformer elimination, in grid-connected PV systems, has many advantages. This not only reduces cost, size, and weight, but also increases the whole system efficiency. However, once the transformer is removed, there is no galvanic isolation between grid and PV array; as a consequence, leakage current appears due to parasitic capacitance to the ground, resulting in prohibitive electromagnetic interference and security issues. This paper presents a novel topology in order to reduce this ground leakage current. It is established that the neutral line in the grid is the same as that of the negative terminal in a PV system, eliminating this way, any possibility of leakage current in this terminal. A sliding mode controller that controls the output current has been employed. The principle of operation of the transformerless inverter is analyzed, but also the topology has been simulated and experimentally tested.