Transient Synchronization Stability Mechanism of PLL-Based VSC During Grid Fault Considering Different LVRT Strategies

Aiming at the stability issue of voltage source converter (VSC) interfaced renewable power system, the transient synchronization stability mechanism of phase-locked loop (PLL)-based VSC during low-voltage-ride-through (LVRT) process is analyzed in this paper considering two typical active power strategies, i.e. the zero active power strategy and the maximum active power strategy. The existence condition of stable equilibrium point (SEP) during LVRT is deduced. The PLL transient stability mechanism is revealed and the transient stability criteria are given based on virtual swing equation and the equal area criterion. In case study, a single-VSC-infinite-bus system is used to verify the theoretical analysis conclusion.