Crowbar电阻取值对双馈感应风力发电机过渡过程影响的分析

The Influence of Crowbar Resistance to the Transition Process of Doubly Fed Induction Generator during Grid Faults

电网故障时双馈感应发电机(doubly fed induction generator,DFIG)会发生转子侧过电流和变换器直流链过电压,同时过电流会造成DFIG电磁转矩的冲击,对风电机组机械系统产生很大的扭切应力冲击。为此,本文首先建立了基于定子磁链定向矢量控制策略的双馈风力发电系统暂态数学模型。在此基础上,研究了撬棒电阻在电网故障条件下,对DFIG过电压过电流以及冲击转矩的影响,同时也对不同双馈电机参数在电网故障时,投入撬棒电阻的过渡过程进行了分析研究,探讨了DFIG采用撬棒保护下低电压穿越过程中的发电机电磁参量峰值特性,深入研究了Crowbar电阻取值以及不同双馈电机参数对电网故障下的电压、电流以及转矩冲击的影响。研究结果表明,Crowbar电阻取值既要考虑过电压、过电流的影响,同时还必须考虑冲击转矩的影响,相同容量双馈发电机其Crowbar电阻的取值也会因电机参数的不同而不同。

For wind turbines with doubly fed induction generator （DFIG）, the over-current of the rotor and the over-voltage of the dc-link will occur during grid faults. Furthermore, the dramatic fluctuations of the stator and rotor current result in oscillating of the electromagnetic torque of DFIG; and the high shear stress impact on the wind turbine mechanical systems will be produced. In order to study the influence of the Crowbar resistance to the voltage, current restrictions and the ectromagnetic torque of DFIG during voltage dips, the transient model of DFIG was presented in this paper based on the stator flux oriented vector control strategy. On this basis, the transient behaviors and the peak characteristics of the electromagnetic quantities of DFIG were investigated with different motor parameters and different value of Crowbar resistance during grid faults. The results show that, the value of Crowbar resistor is not only necessary to consider the effects of over-voltage and over-current, but also to consider the impact of the ectromagnefic torque. For the DFIGs with the same capacity, the value of Crowbar resistor will vary for the different motor parameters.