Network Constrained Fast Decoupled Load Flow Solutions Using Linear Programming

Abstract

The fast decoupled load flow method is now well established as a reliable means for evaluating the steady-state conditions of large scale power system networks. Although the method incorporates a limited number of constraints on control variables, noteably those on transformer taps and generator VAr injections, it is frequently necessary for planning purposes to perform repeated studies in order to achieve satisfactory voltage profiles and active and reactive power flows. The imposition of constraints on bus voltages and power flows, through control of power and reactive power injections and transformer and phase shifter tap changes, considerably reduces the number of studies required. This paper describes how the equations from the fast decoupled load flow method can be used in conjunction with linear models of control devices to apply the necessary constraints through linear programming. The method is to solve iteratively the fast decoupled load flow problem and a decomposed incremental 1 inear programming problem until all constraints are satisfied. Such are the accuracies of the incremental linear models that normally only one iteration is required, and overall computing effort is minimized by choosing common linear network models for load flow and linear programming.