This chapter discusses the concepts of optimal power flow (OPF) and associated computational intelligence (CI) methods, namely artificial neural network (ANN) and ant colony optimisation (ACO). It presents an application of CI methods to solve voltage stability constrained OPF (VSCOPF) for preventive and corrective control actions. The chapter also presents two examples that apply CI techniques to determine optimal preventive and corrective control measures for enhancing voltage stability of the IEEE 30-bus test system. ACO is used to determine the optimal control action that will guarantee minimum voltage stability margin (VSM). The change in VSM due to load curtailment at effective locations is approximated by the sensitivity method in order to save computing time. Simulation results show the capability of the proposed method to improve VSM in normal operation and to restore stable operation in critical situations.
