A novel three phase load flow algorithm based on symmetrical components for distribution systems

Abstract

The majority of distribution systems are either unearthed or indirectly earthed, resulting in practically no zero sequence voltages and currents during normal operation. Based on this assumption, a novel three phase load flow algorithm is proposed. The three phase power at the PQ node is first decomposed into positive sequence power, negative sequence power and the coupled power. The load flow for the positive sequence network can then be solved using conventional iterative algorithms, and the negative sequence network load flow can be solved by means of simple algebra. Finally, the three phase load flow is obtained by inverse symmetrical component transformation. In this algorithm, the unbalanced three phase load flow is simplified into positive sequence power flow. With the order of Jacobian matrix reduced from 3n times 3n to n times n, the complexity and computational cost are reduced significantly. The load flow analysis of a real 28-node distribution system confirms the validity of the proposed algorithm.