Transient stability analysis of grid-following inverters with nonlinear characteristics of PLL
Phase-locked loop(PLL)is a key step to realize phase synchronization in grid-following inverter.Due to its inherent nonlinear characteristics,the traditional small-signal model may not be able to accurately predict the transient stability of PLL in weak grids.In order to ensure the stable operation of PLL after disturbance,a stability analysis method based on nonlinear mathematical model is proposed.First,according to the working principle of PLL,the second order nonlinear differential equation is established,and the output characteristics of PLL are qual-itatively analyzed by the phase plane method,and the effects of different parameters on the transient characteristics of PLL are evaluated.Then,based on the equal-area criterion(EAC),the transient instability mechanism of PLL is analyzed.Considering that traditional EAC may lead to misjudgment of stability,the nonlinear dynamics multi-scale method is used to solve the time-domain expression of the transient state after PLL is disturbed,and the tran-sient stability boundary of PLL is defined.Finally,the accuracy of the analytical solution and the PLL transient sta-bility domain is verified by MATLAB simulation and RT-LAB platform,which provides some reference for the se-lection of PLL control parameters and circuit parameters under weak grid conditions.
NETL
NSTL
万方数据
