Transient Synchronous Stability of PLL-based Wind Power-synchronous Generation Interconnected Power System in Rotor Speed Control Timescale

To peak carbon emissions and achieve carbon neutrality, a power system based on new energy will be built. Wind turbine (WT) is gradually replacing the synchronous machine (SG) to be a main resources in future. Different from SG, whose transient characteristic is decided by rotor speed equation, the transient characteristic of WT is determined by its control strategy. Thus, the synchronizing process of system gradually evolves from "physical-dominated synchronization" to "control-dominated synchronization". The transient synchronous mechanism and stability of power system are more complicated. Present researches usually apply numerical simulation to analyze the impact of WT on power angle transient stability of SG. However, there is not clearly understanding of the synchronous mechanism between WT and SG, much less to the possible transient synchronous stability problems. This paper lucubrated the synchronous process of PLL-based WT-SG connected power system. From the perspective of internal voltage, the transient stability and instability mechanism of WT in rotor speed control timescale (about seconds and corresponding to electromechanical timescale) were also analyzed. The results show that, the PLL-synchronized mechanism of WT brings an additional phase limitation to system, and leads to a new loss-of- synchronism phenomenon. Besides, the rectangular-polar coordinate transformation of WT makes the amplitude and phase of its internal voltage coupled inherently, which is a new causation of the phase-amplitude jointly instability of power system. © 2021 Chin. Soc. for Elec. Eng.