A FUZZY LINEAR-PROGRAMMING APPROACH TO THE REACTIVE POWER VOLTAGE CONTROL PROBLEM

The reactive power/voltage control problem has become a particularly important concern for utilities transmitting power over long distances. Linear programming approaches have been proposed for the steady-state control problem. Usually, simple linear programming formulations are inadequate in satisfying realistic system objectives and constraints. The practical voltage control problem consists of multiple objectives and soft (or fuzzy) constraints. Expert system approaches have been proposed to address these practical considerations. However, the required numerical computations are awkward within the expert system framework. In this paper, multiple objectives and soft constraints are modeled using fuzzy sets. Piece-wise linear convex membership functions for the fuzzy sets are defined. Under this definition, the fuzzy optimization problem is reformulated as a standard linear programming problem. The new objective function represents the compromise among the original competing objectives and the soft constraints. In addition, discrete constraints are considered. Numerical examples demonstrate the approach.