Stability analysis of grid-connected PV generation with an adapted reactive power control strategy

The static VAR compensator is widely applied in large-scale grid-connected photovoltaic (PV) generation to participate in voltage regulation of power system, which ignores the reactive power regulation capability of PV inverter. In this study, firstly, the constraints of maximum operating current and output voltage's amplitude of PV inverter are considered, and the reactive power regulation capability of the PV generation is evaluated; secondly, an active participation in voltage regulation and control strategy of PV generation is proposed considering reactive power demand of system. This control method through the real-time detection and comparison with reference value of point of common coupling (PCC) voltage, automatically obtain the reactive demand to maintain PCC voltage by PI controller and realises the dynamic adjustment; finally, a time-domain small-signal model for PV generation is established, and based on this small-signal model, eigenvalue analysis is employed to study the influence of the grid strength, operating condition, and the reactive power control strategy on operating stability. Based on the time-domain simulation example in EMTDC/PSCAD, the validity of the theoretical analysis and the feasibility of the control strategy are verified.