处理不接地配电网三相潮流不收敛的变压器建模新方法

A Novel Transformer Modeling Method for Overcoming Divergence of Three-phase Power Flow in Ungrounded Power Distribution Networks

中性点不接地的变压器导纳阵奇异,导致配电网的三相潮流很难收敛。三相潮流不收敛的原因是系统中的零序电压是漂浮的。为此,文中提出一种设定零序电压参考值的方法,通过增广变压器导纳阵解决其奇异性问题。该方法在变压器模型中副边侧增加一个零序电压设定值,该设定值的大小不会影响中压配电网的电流分布以及配电网其他部分的潮流计算结果。所提出的三相变压器模型既适用于前推回推潮流法,也适用于隐式ZBus高斯法。算例验证了新方法的正确性。

In ungrounded distribution networks,the three-phase power flow may diverge because the admittance matrix of transformer is singular.With a given reference for zero-sequence voltage,this paper proposes a novel method for modeling three-phase transformers able to overcome the singularity.The transformer admittance matrix is augmented by adding a constraint of the voltage on the secondary side,certain that the value of the constant zero-sequence voltage reference will not affect the calculated current in the medium voltage(MV)network or the power flow in other segments.The proposed model can be used in the popular three-phase power flows such as backward/forward sweep(BFS)and implicit ZBusalgorithms.Numerical tests show the correctness of the proposed method.