Analysis of Transient Stability of Photovoltaic Grid-connected System Considering Low Voltage Ride Through

With the increasing development of photovoltaic systems, the influence of converter dynamic characteristics on system transient stability is increasingly prominent. In the transient process, the photovoltaic grid-connected system is required to have a certain low voltage ride through(LVRT) capability, but the dynamic interaction between the control characteristics of fault ride through and phase-locked loop (PLL) may lead to the risk of instability. Therefore, considering the characteristics of LVRT and PLL, this paper theoretically analyzes the transient stability of photovoltaic system. Firstly, a photovoltaic grid-connected model considering LVRT is established. Then considering the influence of grid-connected impedance, PLL proportional coefficient and integral coefficient, establish an extended nonlinear model of PLL. On this basis, the equal area criterion(EAC) is used to analyze the influence of network parameters on the stability of photovoltaic grid-connected system. Finally, the correctness of the analysis is verified by simulation.