Topology review of doubly grounded transformer-less single-phase inverters

Photovoltaic (PV) transformer-less single-phase inverters are widely used in the solar generation systems because of low cost, high power density, and high efficiency. However, there is a common mode leakage current in the transformer-less inverters, which may endanger personal safety. In order to reduce the common mode leakage current, extra semiconductors should be added into the PV inverters to decouple the dc side from the ac side. However, the common mode leakage current is affected by the environmental condition and parameters of power devices. Since grounds of the PV array and the output terminal of the inverter are shorted, the common mode leakage current in the doubly grounded inverters can be eliminated thoroughly. Topologies of the doubly grounded inverters are reviewed in this paper, which can be divided into two categories, that is, hybrid topologies and topologies using energy storage elements. Derivation of the reviewed topologies is given. Different topologies of doubly grounded transformer-less single-phase inverters are compared.