Convergence of the fast decoupled load flow for systems with heavy reactive power compensation

Abstract

This paper presents an alternative formulation for the shunt elements in the fast decoupled load flow equations to improve the convergence performance of the algorithm for systems operating under heavy reactive power compensation conditions. The formulation proposes a sign change for the diagonal terms corresponding to the contribution of the capacitive shunt elements while calculating the load flow matrices. A spectral analysis has been carried out to examine the convergence performance of the algorithm with the proposed formulation by calculating the spectral norm of the iteration matrix in the load flow equations. It is shown that this index exhibits a strong dependence on the convergence of the algorithm; it is reduced when the rate of convergence is improved. It is shown in this paper that this norm is significantly reduced when the shunt elements are represented by the proposed formulation. The proposed formulation has been exhaustively tested on four IEEE test systems, and it is shown that the algorithm proposed is consistently superior to the other formulations given in the literature. The proposed formulations may therefore be used for solving systems with heavy capacitive power compensation, such as systems having load flow equivalent circuits or EHV cables.