计及低电压穿越及故障全过程动态的双馈风电场等值方法

Equivalent Method of DFIG-based Wind Farm Considering Low Voltage Ride-through and Dynamics of Entire Fault Process

在分析双馈感应发电机(DFIG)故障各阶段动态的基础上,提出了一种计及低电压穿越控制的双馈风电场等值方法。首先,讨论了低电压穿越控制策略,给出了含双馈风电场的电力系统故障稳态潮流计算方法。在考虑电压暂态过程的条件下,分析了外部系统短路故障后DFIG转子电流的变化机理,指出电压跌落深度及风电功率是影响短路电流的主要因素,可根据动作分界线判断撬棒是否动作。然后,根据初始风速及撬棒状态将风电场中的DFIG分为3群,并对等值DFIG及集电网络进行聚合。为提高等值模型在恢复阶段的精度,根据故障稳态电压对双馈风电场功率恢复曲线进行预估,并在此基础上对等值DFIG恢复速率进行分段修正。最后,对含双馈风电场的算例系统进行了等值计算。仿真结果表明,等值模型较好地保持了原系统在故障各阶段的动态,在保持较高精度的前提下有效简化了系统,提高了计算速度。

Based on the analysis of the dynamics of the doubly-fed induction generator(DFIG)in each stage of the fault,an equivalent method of DFIG-based wind farm considering the low voltage ride-through(LVRT)control is proposed.First,the LVRT control strategy is discussed,and a method for calculating the fault steady-state power flow of the power system with a DFIG-based wind farm is proposed.Under the consideration of the voltage transient process,the mechanism of changes in the rotor current of the DFIG after the short-circuit fault in the external system is analyzed.It is pointed out that the depth of voltage dip and wind power are the dominant factors affecting the short-circuit current,and the state of the Crowbar can be determined by the operation division line.Then,DFIGs in the wind farm are clustered into 3 groups according to the initial wind speed and the Crowbar state,and the equivalent DFIGs and the collection grid are aggregated.To improve the accuracy of the equivalent model in the recovery stage,the power recovery curve of the DFIG-based wind farm is estimated according to the steady-state voltage of the fault.On this basis,the recovery rate of the equivalent DFIGs is piecewise modified.Finally,equivalent calculations are performed on a case system with a DFIG-based wind farm.The simulation results show that the equivalent model effectively maintains the dynamics of the original system in each stage of the fault,simplifies the system,and improves the calculation speed while maintaining high accuracy.