Fuzzy Logic Based Successive LP Method for Reactive Power Optimization

Abstract

This paper presents a new Successive Fuzzy Linear Programming (SFLP) method for Reactive Power Optimization (RPO) to minimize the transmission loss and improve the voltage pro le. The SFLP method uses Fuzzy LP (FLP) model in the Successive Linear Programming (SLP) framework to solve the RPO problem. In the FLP model, the objective and each of the constraints are assigned a satisfaction parameter. The satisfaction parameter corresponding to the objective quanti es the degree of closeness of the objective in the current state to the optimum. The satisfaction parameter corresponding to a constraint describes the degree of enforcement of that constraint. By maximizing the minimum of these satisfaction parameters, the objective as well as the constraint enforcements are maximized. The SFLP method of RPO is e cient and reliable in scheduling systems having severe under-voltages and insucient reactive power, as the method is capable of maximizing the enforcement of the violated load bus voltage constraints, minimizing the transmission loss while simultaneously enforcing all the other constraints strictly. This method uses compactly stored, factorized constant matrices in all the LP steps, both for the construction of the FLP model as well as for the power ow solution. The control variables used in this method are generator bus voltage magnitudes, reactive powers of switchable VAR sources, and on-load tap changer (OLTC) settings of transformers. The method was tested on IEEE test systems and on a practical electric utility system. The merits of the proposed method compared to the SLP method using non-fuzzy approach are brought out.