Leakage current elimination mechanism for photovoltaic grid-tied inverters

The elimination of leakage current is of first importance for transformerless grid-tied photovoltaic (PV) inverters. A unified leakage current analytical model for single phase inverters, which unifies topologies of both transformer and transformerless, is presented in this paper. It is suitable for the analysis of leakage current elimination mechanism for all the bridge topologies, which are systematically analyzed and categorized. After that, the topologies of H5, Heric and a H6-type configuration are optimized. The leakage current of these optimized inverters can be better eliminated by changing the topology configuration and substituting the suppressor way of changing the common impedance with the way of constant common voltage. On the other hand, the inverters can operate in any power factors by means of the optimization of the modulation strategies. A grid-tied photovoltaic inverter experiment is conducted with a 5kW optimized Heric prototype, and the theoretical analysis is verified.