面向电力系统暂态稳定分析的双馈风电机组动态模型

Dynamic Model of DFIG Wind Turbines for Power System Transient Stability Analysis

大规模风电并网对系统暂态和中长期稳定都有重要影响,提出能够用于电力系统稳定分析的风电机组、风电场简化模型对于深入研究风电与电网暂态互动是十分重要的。目前WECC、IEC、GE等研究机构已提出了各自的风电机组、风电场标准化通用模型,但模型均较为简化,对于双馈风电机组建模没有考虑暂态过程中的变流器闭锁和转子crowbar投切等机制,导致外特性准确性不足,使得暂态稳定分析结果过于乐观。针对该不足,文中按多时间尺度模型简化原理,系统地推导双馈风电机组气动、机械及电气部分的简化模型,并着重探讨电网电压扰动强度与风电变流器"电流源–电压源–无源阻性"3种状态特性的关系,从而导出能直接用于暂态稳定分析的简化模型和Crowbar投入、切出代数判据,在保证仿真效率的同时提高了模型暂态特性的精度。最后,通过与详细模型的仿真对比及与机组实验结果的对照,验证所提简化模型的有效性。

Large scale wind farm integration has great impact on power system transient and long term stability, in order to have a deep insight into this new phenomenon and the mechanism of dynamic interaction, generalized wind turbine or wind farm model for system stability analysis should be proposed. WECC, IEC, GE and other research organizations have already done some modeling work. ＇However, the models presented are focused on modeling of control loop of wind turbine and its parameters recognition. Therefore, little attention has been paid on the mechanisms of rotor crowbar protection and converter blocking during lower voltage of DFIG, so as to draw an Overly optimistic result for stability analysis. In this paper, DFIG stability model was deducted from the detailed electromagnetic transient model, based on the knowledge of multi-time scale modeling technics. More attentions were paid to the modeling and analysis of VSC- DFIG＇s dynamic behavior during grid transients. Three reduced state model of VSC-DFIG were put forward, which clear clarified the state transition from current-source behavior to passive-resistive and within which is voltage-source state behavior. Criterion for crowbar action was obtained through former analysis, which suit for transient program and the accuracy of DFIG transient behavior was greatly improved. Finally, simulation results using the reduced model were compared with that of detailed DFIG model and experiment results. It is shown that the model presented in this paper can reflect the electromechanical dynamic performance of DFIG wind turbine more precisely.