Impact of large-scale photovoltaic-energy storage power generation system access on differential protection of main transformer under symmetrical faults

The low voltage ride-through (LVRT) requirements demand large-scale photovoltaic (PV) power generation system remain connected to the grid during faults. It results in considerable impact on characteristics of fault current. This paper combines charge-discharge energy storage (ES) with PV enhance LVRT capability. Based inverter control strategy and specific requirements, current PV-ES is discussed this paper. In order analyze characteristic, expression as three-phase short-circuit faults occurs both sides main transformer calculated. Furthermore, taking winding connection into account, ratio differential braking further derived find out factors influencing performance protection. found that protection include rated capacity system, severity, length transmission line so on. And increase, would experience reduced sensitivity or even do not trip. findings can lay a foundation for improvement elaborate evaluation protection, including operation condition second harmonic element, presented verified by simulation using MATLAB/Simulink.