双馈风电场频率响应模型的结构与参数联合辨识OA

Doubly-fed induction generator(DFIG)wind turbines can provide virtual inertia and active droop control to power systems through supplementary active power control.However,the frequency response modeling of DFIG-based wind farms are also affected by rotor speed control and pitch angle control.Therefore,directly applying the inertia-damping model commonly used for synchronous generators can result in significant errors.This paper proposes a frequency response model identification method for DFIG-based wind farms based on augmented UD decomposition identification(AUDI).First,it is demonstrated that the frequency response model exhibits high-order characteristics,with the effective model order changing to fifth and seventh order under pitch-angle control locking and activation,respectively.Second,considering that the internal states and control parameters of wind farm units are generally inaccessible to system operators,making a full-order dynamic model impractical for implementation,a polynomial discrete-time model is established for the frequency response of DFIG-based wind farms.The proposed model requires only PMU frequency measurements and active power sampling data at the point of common coupling.An AUDI recursive formulation is derived,and an optimal model-order selection method is developed based on the F-test theory,enabling joint structure and parameter identification of the wind farm frequency response model under small-disturbance conditions.Finally,simulations on a 5-machine,11-bus system demonstrate that the proposed method can accurately identify the model order under varying wind-speed conditions.The identification results are close to unbiased estimates,and the proposed method exhibits better numerical stability than least-squares-based methods.