Optimal bidding strategy of power generation companies is one of the most important problems of the restructured power systems. This problem must maximize generation companies’ profit in a competitive electricity market environment. The concept of Fuzzy Expectation Value (FEV) is proposed in this paper for building of optimal bidding strategies. Based on historical data, the production cost and the experts' knowledge, the well-known fuzzy set theory is employed to represent the bidding behaviors of rival generation companies. Then a fuzzy programming model is developed and a solution method is proposed.

A numerical example with six suppliers and two large consumers is performed to and the results are compared with the Particle Swarm Optimization (PSO), Genetic Algorithm (GA), and Monte Carlo method. The obtained results show the capability and the viability of the proposed method.