To maximize the potential benefits of the structure and function of grid connected inverters and integrate the function of filtering and reactive power compensation into PV power plant inverters, while achieving multi-function reusing, such as active grid, harmonic suppression, reactive power compensation and voltage compensation. After researching the controlling strategies of inverter and power quality characteristics and controlling methods, the topology of PV power plant is improved, based on which the reactive power allocation strategy of dynamic stability margin of inverter is proposed, and the controlling strategy of shunt connected inverter and series connected inverter are researched in detail. The use of the controlling strategy mentioned above effectively implements the power quality complex governance of large-scale grid-connected photovoltaic, and the correctness and effectiveness of the proposed controlling strategy is verified by PSCAD/EMTDC.