Enhanced Power Quality PV-Inverter with Leakage Current Suppression for Three-Phase SECS

This paper presents an enhanced power quality solar photovoltaic (PV) inverter enabling common-mode leakage current elimination. A three-phase transformer-less solar energy conversion system (SECS) is considered here, which, along with peak active-power production from PV- array, ensures different power quality improvement capabilities such as grid current harmonics mitigation, grid currents balancing, while also offering the grid reactive power support. Unlike conventional power quality inverters, this strategy is a robust with respect to abnormalities in grid-voltages at far radial ends, and does not compromise with the leakage currents caused by parasitic-capacitance of PV-array with ground. 

Common practice in the PV inverter power quality control is to neglect the PV leakage-currents, however, they considerably affect the system performance by deteriorating the power quality and causing the safety issues of operating personnel. The standards VDE-00126 and NB/T-32004, therefore, compel the transformer-less PV-systems to operate with leakage current under 300mA range. Various simulation and test results show the satisfactory performance of the presented strategy, even under various grid-side abnormalities. The comparative analysis with state-of-art techniques shows the effectiveness of the strategy. Under all test conditions, the harmonics in grid-currents are observed within limits as per the IEEE-519 and IEC-61727 standards, while the PV leakage-currents are maintained well within the range recommended by VDE-00126 standard.

Index Terms- Common mode voltage (CMV), Harmonics, Kalman filter (KF), Leakage Currents, Power quality and Voltage source Converter (VSC).