分散式双馈风电机组接入配电网的不对称短路电流实用计算

针对现有双馈风电机组(double fed induction generator,DFIG)短路电流解析计算过于复杂,难以进行工程计算的情况,提出了一种针对DFIG不对称短路电流的实用计算方法.通过建立不对称故障的含DFIG配电网复合序网图及正序增广模型,分析DFIG短路电流各序分量构成;计及不对称故障后DFIG低电压穿越策略,分析撬棒投入和未投入时短路电流负序周期分量,推导了短路电流负序周期分量计算式.以正、负序等值电压,计算阻抗及转子电流为依据,分析撬棒投切动作区域,制订故障后DFIG不对称短路电流负序周期分量计算曲面,最后给出DFIG接入配电网的不对称短路电流实用计算步骤,并通过算例验证方法的正确性.所提方法能有效降低含DFIG配电网不对称短路电流的计算难度,适用于工程中DFIG不对称短路电流计算.

Practical calculation of asymmetric short circuit current of DFIG connected to distribution network

In view of the existing complex analytic calculations of DFIG short-circuit current are hardly applied in engineering projects, a practical calculation of asymmetric short-circuit current of DFIG is proposed. According to the complex sequence and their Thevenin equivalent model of DFIG network, the composition of each sequence component of DFIG short-circuit current is analyzed. Moreover, considering the low-voltage ride through strategy of DFIG, the negative sequence currents of periodic components of short circuit current are well analyzed when the crowbar activation and deactivation, and the formula of the negative sequence currents of periodic components of short circuit current is derived. On the basis of positive and negative sequence open circuit voltage, calculating impedance and rotor current, the judgement of crowbar activation is established. The pre-calculated surfaces of negative sequence currents of periodic components of short circuit current are proposed, and the procedure for calculating the asymmetric short-circuit current of DFIG is designed. Finally, the proposed method is verified by simulation.The method in this paper can effectively reduce the difficulty of calculating the asymmetric short-circuit current of the distribution network containing DFIG, and is suitable for the calculation of DFIG asym-metric short-circuit current in engineering.