Leakage Current Mitigation in Roof-Top Grid Tied Photo Voltaic Systems

Abstract: Photovoltaic is desirable due to its ubiquity, abundance, sustainability, ecofriendly nature, cheapness etc. Solar plants are struck by several technical as well as non-technical challenges. Transformer less inverters are highly efficient, light and cost effective. Leakage current is a major threat for transformer less PV systems. Parasitic capacitance and high frequency varying common mode voltage is responsible for leakage current. This cologne current cause losses, radiated interferences, damage of PV array, harmonic distortion in grid and safety disasters. The causes, magnitude, path, detrimental, point of measurement and preventive measures of leakage current are analyzed. Details of leakage current study in a rooftop grid tied systems near to the college is cited to substantiate problem identification. DC decoupling implemented through H5 topology of inverter can mitigate leakage current to great extent. An efficient system is designed with solar panel, MPPT using perturb and observe method utilizing cuk converter and H5 inverter. LLCL filter is used to suppress harmonics. MATLAB simulation is done for 230V, 50 Hz system to get topological verification. The leakage current profile is compared with conventional H bridge, HERIC and H6 topologies. H5 topology gave minimum leakage current.

Keywords: Leakage current, Common mode voltage, differential mode voltage, parasitic capacitance, transformer less inverter, Maximum Power Point Tracking (MPPT), LLCL filter, hysteresis control.