中压不接地配电网三相潮流新方法

在大量分布式电源接入中低压配电网的新形势下，三相潮流计算是分析其影响的基本手段。针对现有中压不接地配电网三相潮流研究主要采用人为设置参考中性点/零序电压的方式，导致无法仿真分析中性点/零序电压偏移、不接地网络零序潮流和相-地电压不平衡等情况，提出一种中压不接地配电网三相潮流新算法。首先，提出不接地配电网三相潮流在节点变量和导纳矩阵方面的特殊性。然后，设计基于功率平衡方程和牛拉法，采用导纳矩阵可逆化处理和矩阵替换技术实现约束零序电流为零的不接地配电网三相潮流算法。最后，基于6节点系统和修改的IEEE123算例仿真不接地配网的潮流，结合PSCAD验证所提方法在不同场景下的准确性以及在大电网中的适用性和收敛性，并在地市电网中进行实际应用。算例分析表明，所提算法计算结果准确，具有良好的工程实用性。

A method for three-phase power flow in a medium-voltage ungrounded distribution network

With a large amount of distributed generation connected to the medium and low voltage distribution network, three-phase power flow calculation is the basic means to analyze their influence. The existing research on three-phase power flow for a medium-voltage ungrounded distribution network mainly adopts the method of manually setting the reference neutral point or zero-sequence voltage. This makes it difficult to simulate and analyze the neutral point or zero-sequence voltage offset, and the zero-sequence power flow and the imbalance of phase to ground voltage. Thus this paper proposes a new three-phase power flow algorithm for a medium-voltage ungrounded distribution network. First, the particularity of three-phase power flow for this network in terms of node variables and admittance matrix is analyzed. Second, based on a power balance equation and the Newton-Raphson method, a three-phase power flow algorithm for an ungrounded distribution network with constrained zero-sequence current is designed by using admittance matrix reversible processing and matrix replacement technology. Finally, the power flow for the ungrounded distribution network is simulated based on the 6-bus system and the modified IEEE123 test case. The accuracy of the proposed method in different scenarios and its applicability and convergence in large power grids are verified by PSCAD, and a practical application is carried out in local power grids. The example analysis shows that the proposed algorithm gives accurate calculation results and good engineering practicability.