考虑撬棒保护接入的双馈感应发电机转子磁链动态特性

Rotor Flux Dynamic Characteristics of Doubly-fed Induction Generator with Crowbar Protection

撬棒保护电路的接入会改变低电压穿越过程中双馈感应发电机(DFIG)定转子磁链间的耦合过程和耦合强度,由此将影响机组磁链衰减动态和撬棒保护性能。针对这一问题,提出了一种刻画定子磁链与转子绕组交链感应作用的磁链耦合系数,将电网故障后电机的磁链暂态耦合过程处理为不同状态的叠加,综合研究撬棒电阻对转子感应磁链正序、负序和暂态反向交流分量幅值和相角的耦合规律,用转子磁链空间矢量图和矢量轨迹图描述转子磁链动态响应过程。最后,针对电网不对称故障下撬棒取值的问题,提出了一种基于转子磁链幅值配比原理和最优倾角的撬棒阻值选取方法。该方法可减小磁链耦合不当对机组的暂态冲击,从而有效改善机组的无功外特性和瞬态性能。采用MATLAB/Simulink仿真验证了理论分析和所提方法的正确性。

The activation of crowbar protection will change the doubly-fed induction generator(DFIG)stator and rotor flux coupling process and its coupling strength during the low voltage ride-through(LVRT)period,which will affect the dynamic attenuation of the unit fluxes and the crowbar protection performance.Facing this problem,this paper proposes a kind of flux coupling coefficients to characterize the induction effect between stator flux and rotor winding,which deals with the flux transient coupling process of generator following agrid fault as the superposition of different states,while analyzing the coupling laws of crowbar resistance on the amplitude and phase angle of the positive sequence,negative sequence,as well as transient reverse ac rotor induction flux component.On this basis,the dynamic response of the motor rotor flux is described by the rotor flux space vector diagram and vector locus.Finally,an optimal configuration method of crowbar resistance is proposed based on the principle of rotor flux amplitude ratio and the optimum inclination angles to deal with the grid asymmetrical faults,which can weaken the DFIG transient response due to improper flux coupling while effectively improving the reactive power characteristics and transient performance of the unit.The correctness of the proposed theoretical analysis and method is verified using MATLAB/Simulink simulation software.