Development of three-phase Newton optimal power flow for studying imbalance/security in transmission systems

This paper presents a three-phase optimal power flow (TOPF) method based on Newton's method for the off-line balance/imbalance and security analysis of large scale transmission systems. The TOPF deals with minimization of the system three-phase MW losses while satisfying three-phase power flow equations, three-phase security constraints and voltage imbalance factor (VIF) constraints, etc. The three-phase models considering the coupling effect among the phases are used in this method. All models are based on the phase frame representation. The sparse matrix technique is used and the pivoting programming techniques for reducing the computer memory required is addressed. Several functions are implemented in the proposed software for a more realistic simulation; these functions include the reduction of the controller set, treatment of infeasibility, implementation of static VAR compensators (SVCs), selection of load models, and initialization, etc. An algorithm covering the main and trial iterations is used for identifying an accurate set of active inequality constraints. The 265-bus Taipower system is used to serve as an example for illustrating the performance of the proposed method in studying the imbalance problem caused by the upcoming high-speed electric railway load in Taiwan. (C) 2000 Elsevier Science S.A. All rights reserved.