Grid Frequency Trajectory Fitting under Transient Power Impact Caused by Highly Proportional Wind Power Fault Ride

With the continuous increase of wind power penetration, the temporary power shortage generated by the low-voltage ride-through (LVRT) characteristics of wind power will bring a huge impact on the power system, even triggering a rapid drop in grid frequency and the risk of under-frequency load-shedding (UFLS), and it is necessary to study the rapid prediction and fitting technology of frequency trajectory under the temporary power shock. The active power recovery curves of wind turbines with different LVRT strategies show different patterns, and if the power recovery process is ignored to directly resolve this power disturbance as a permanent power disturbance or step disturbance superposition, it will cause a huge error in frequency evaluation. To solve the problem above, a system power disturbance resolution method, which takes the power recovery process into account, is proposed to resolve the active power disturbances in the LVRT, recovery, and normal periods of wind power using segmentation functions. Then, an optimized system frequency response (SFR) equivalent model is proposed considering the frequency modulation (FM) and virtual inertia of wind power; based on the equivalent power principles, the frequency response (FR) transfer function of the equivalent wind turbine considering multiform LVRT trajectories can be parametrically identified and the frequency trajectory will be fitted or predicted quickly. Finally, the accuracy and effectiveness of the proposed method are verified through the simulation of the IEEE 39-bus system in the case study.