双馈感应发电机接入电网的三相短路电流峰值评估

短路电流计算是电网规划和保护的基础,文中将双馈感应发电机(DFIG)定子磁链强制分量归算至定子侧,将定子磁链直流分量归算至转子侧,形成静态等值电路,分析转子感应磁链随转速的变化规律,研究转子电阻对故障时定子磁链直流分量动态衰减及其与转子绕组感应过程的影响,推导电网三相短路时DFIG定子短路电流解析式。比较了近端和远端故障时不同撬棒电阻对应定子短路电流特性,提出了DFIG接入电网的三相短路电流峰值评估方法。该方法能有效计算DFIG机端、馈线上下游和其他馈线故障时的三相短路电流峰值序列,采用MATLAB/Simulink软件仿真验证了所提出方法的正确性。

Evaluation of Three-phase Short-circuit Peak Current for Doubly-fed Induction Generators Integrated into Power Grids

The calculation of short-circuit current is an important foundation for power system planning and protection. This paper imputes the forced component of stator flux of doubly-fed induction generator (DFIG) to the stator side and the DC component of stator flux to the rotor side to form the static equivalent circuits. Then the law of variation of the rotor induction flux with its rotor speed is analyzed, and the impact of rotor resistance on the dynamic attenuation of the DC component of stator flux and its inducing process with the rotor winding during a fault is researched. Moreover, the analytic expression of stator current under three-phase short-circuit is derived. Furthermore, the stator short-circuit current characteristics with different crowbar resistance are compared when the short-circuit fault occurs near to or far from the DFIG. Finally, an evaluation method is proposed to determine the three-phase short-circuit peak current of DFIG integrated in the power grid. This method can efficiently calculate the three-phase short-circuit peak current sequence of DFIG when the faults occur at DFIG-side, feeder upstream and downstream, and other feeders in the grid. The correctness of the proposed method is verified in MATLAB/Simulink simulation software.