感应发电机接入配电网的短路计算序分量模型及算法

Symmetrical Components Model and Analytical Method of Short Circuit Current Calculation for Induction Generators Integrated into Distribution Network

分布式发电大规模接入电网将改变潮流和短路电流的分布。利用感应发电机(induction generator,IG)正负序静态等值电路,研究电网不对称故障时定转子磁链序分量相关系数,并结合故障过程中IG暂态磁链特性和转差,建立IG短路计算的序分量电流源模型。比较计及转差前后和不同接入容量时多感应发电机(induction generators,IGs)端电压和短路电流响应,揭示出IGs短路电流与电网节点电压的耦合关系。推导电网故障瞬间IG暂态等值电势,提出计及转差变化的多IGs配电网短路电流的对称分量迭代算法。采用PSCAD/EMTDC仿真软件中IG的5阶动态模型,仿真验证了所提方法的正确性。

When the large-scale distributed generation is embedded in power system, the distribution of power flow and short circuit current will be changed. Using the positive and negative sequence steady-state equivalent circuit of induction generator （IG）, the correlation coefficients of flux sequence components between stator and rotor under distribution grid unsymmetrical fault were analyzed. According to the transient flux characteristics and rotor slip of IG during the fault process, the current source model based on symmetrical components of IG was established for short circuit current calculation. Then, the terminal voltage and current responses of induction generators （IGs） with and without rotor slip change and under different penetration levels were compared to investigate the coupling relation between the short circuit currents of IGs and nodal voltages in distribution network. The transient equivalent potential of IG at the instant of grid fault was subsequently derived. Finally, an iterative algorithm to determine the sequence components of short circuit current taking into account rotor slip changes for multiple IGs in distribution network was proposed. The correctness of proposed method was verified by the fifth electromagnetic transient model of IG in PSCAD/EMTDC simulation software.