Simulation of low voltage ride through scheme for inverters connected to distribution system with high R/X ratio

Solar Photovoltaic (PV) inverters are used to feed power to the grid. These PV inverters are equipped with anti islanding protection technique. As the PV penetration in the grid increases, this feature would affect the operation and reliability of grid during fault conditions. Thus, Low Voltage Ride Through (LVRT) capability is suggested for PV inverters connected to High Voltage (HV) and Medium Voltage (MV) lines. During voltage sag condition, LVRT prevents the inverters from being disconnected and supports the grid voltage through reactive power injection. Low Voltage (LV) systems, unlike HV and MV systems, have resisitive characteristics of the line, thereby making the LVRT techniques based on reactive power injection ineffective in case of LV system. To address this issue, sensitivity matrices are derived in this paper. These matrices determine the effect of active and reactive power on voltage magnitude in case of HV and LV systems. A voltage support scheme for LV system is proposed in this paper. Detailed simulation studies are carried out and results are included in this paper. Performance of the the proposed scheme is compared with a conventional LVRT scheme.