基于C_p函数初值模型的并网DFIG稳定性分析

Stability Analysis of Grid-integrated DFIG Based on Initialization Model with C_p Function

双馈异步风电机组初值模型影响并网双馈异步风电机组稳定性分析结果的可信度。现有恒机械功率(P_(wt))模型未考虑转速变化对机械功率的影响,恒最优功率系数(k_(opt))模型不适用于转速限制、桨距角控制等降额运行状态。本文提出基于风能利用系数(C_p)函数的并网双馈异步风电机稳定性分析模型,其中初值模型的风速、转速与桨距角皆为可控变量,实现了不同转速、调度出力与桨距角条件下双馈异步风电机组初值求解与大/小扰动的稳定性分析。将C_p模型得到的稳定性分析结果与现有恒机械功率及恒最优功率系数模型进行对比,分析现有模型误差可发现,恒机械功率与恒最优功率系数模型的机械功率误差会导致降额运行时转速初值误差,降低大扰动下转速与机端功率动态仿真结果精度,机械转矩的误差也会影响小扰动稳定性分析结果。

The initialization model of doubly-fed induction generator(DFIG)affects the credibility of the stability analysis result of grid-integrated DFIG.The existing constant mechanical power(Pwt)model does not consider the influence of rotation speed change on the mechanical power,while the constant optimal power coefficient(kopt)model cannot be applied under the derating state operation conditions such as speed limit and pitch angle regulation.In this paper,a stability analysis model of grid-integrated DFIG based on wind utilization coefficient(Cp)function is proposed,in which wind speed,rotation speed and pitch angle are set as controlled variables.In this way,the solution of an initialization model of DFIG and the small/large disturbance stability analyses are realized at different rotor speeds,power dispatches and pitch angles.The stability analysis result obtained by the Cp model is compared with those from the constant Pwt and constant kopt models to analyze the errors of the existing models.It is found that for the constant Pwt and constant kopt models,the error of mechanical power will lead to the errors of initial rotation speeds under the derating state operation and reduce the precision of the rotation speed and terminal power obtained by dynamic simulations under large disturbances.Moreover,the error of mechanical torque will also affect the result of small disturbance stability analysis.