感应发电机接入配电网的不对称短路电流峰值评估

摘要

The short circuit current calculation is an important foundation for planning and protection of distribution grid with distributed generation. The transient characteristics of induction generator (IG) are investigated when the unsymmetrical fault occurs in the distribution network, and the analytic formula of its stator current under unsymmetrical short circuit is derived. The impact of an IG rotor speed and the fault initial time (or phase) to the short circuit current under unsymmetrical fault are studied when the short circuit occurs. According to the equation of rotor motion and its steady-state circuits in the positive and negative sequence component networks, an evaluation method to determine the current peak of unsymmetrical short circuit for an IG in distribution grid is proposed by considering its rotor speed variations. The correctness of the method is verified by using the fifth electromagnetic transient model of IG in PSCAD/EMTDC simulation software.%短路电流计算是分布式发电接入配电网规划和保护的基础。研究了感应发电机(IG)的不对称故障暂态特性，推导配电网不对称故障时IG定子短路电流的解析式。由于配电网不同位置发生短路故障时，故障瞬间电压相位变化和发电机转速在故障过程中快速上升，都将对IG注入电网的短路电流产生影响。在计及配电网不对称故障后IG转子转速变化的同时，利用转子运动方程和正负序静态等值电路，得到了估计电网发生故障后IG的短路冲击电流算法，最后利用电磁暂态分析软件中IG的5阶动态模型仿真验证该方法的正确性。