Realization of Constant Common Mode Voltage in Transformerless Photo Voltaic Inverter Topologies

摘要

Advances in Photo Voltaic (PV) cell technology, availability of power semiconductor modules and low cost controllers led to harvesting solar power abundantly in recent times. In low power PV applications, single phase full bridge inverter is favored over half bridge inverter because of low DC voltage. A transformer is essential in a PV system either on ac or dc side to provide galvonic isolation. In domestic applications, the transformer can be removed to optimize the size of the system. However, the full bridge topology generates variable common mode voltage. Due to high parasitic capacitance of PV panels, this results leakage currents, distortion of injected current and raises safety concerns. This paper investigates common mode voltage behavior of various popular single phase topologies. Detailed simulation study is carried out in MATLAB and results are presented.