Dynamic Reduced Order Model of VSC with Phase Lock Loop Based on Singular Perturbation

Phase lock loop (PLL), served as a dedicated synchronization unit, is a crucial component for voltage source converter (VSC). As a nonlinear unit, the dynamics of PLL raise the order of the overall VSC system model, which finally increases the analysis complexity. To overcome these, this paper proposed a dynamic reduced order model of VSC with PLL based on singular perturbation. The states of the VSC system can be divided into three parts by time scales, i.e. relatively fast states, relatively slow states, and states with medium time scale, and then can be reduced by singular perturbation method. Thanks to the method, the variables in the reduced model reserves their physical meaning. And the proposed model can greatly decrease the computational burden and analysis complexity with little compromise of accuracy. The effectiveness of the proposed reduced model has been fully validated in PSCAD/EMTDC compared with full detailed model under static, dynamic operation conditions, as well as under voltage sag event.