The increase of power transmission and interconnection of power system have led to an increasingly complex system which has to be operated close to the limits of security/stability. The problems related to voltage/transient instability have become a major concern for secure operation of many power systems. Consideration of voltage/transient stability constraints in optimal power flow (OPF) problems is increasingly important in the modern power systems operation. The OPF problem with voltage/transient stability constraints is however a nonlinear optimization problem with both algebraic and differential equations, which is difficult to be solved even for small power systems. This paper develops a robust and efficient method for solving OPF problems with voltage/transient stability constraints in the power system operation. The proposed method is based on differential evolution (DE), which is a branch of evolutionary algorithms with strong ability in searching global optimal solutions of highly nonlinear and non-convex problems. Numerical tests on the IEEE six- generator, 30-bus system have demonstrated the robustness and effectiveness of the proposed approach for solving optimal operation of power systems.
