FUZZY-LOGIC BASED UNIFIED POWER-FLOW CONTROLLERS FOR TRANSIENT STABILITY IMPROVEMENT

A fuzzy logic approach is applied to coordinate three control inputs: in-phase voltage control, quadrature voltage control, and shunt compen sation, of a unified power flow controller to improve the transient st ability of a power system. The fuzzy rules for the controller are crea ted based on a bang-bang control strategy whose objectives are minimis ing the first swing, damping the oscillations at an optimum rate, and maximising the transient stability margin. The proposed controller als o incorporates a technique of reducing the chattering of generator out put which naturally results from the application of bang-bang control. Simulation results show that the fuzzy logic based controller provide s satisfactory performance, meeting the design objectives. The results also show the robustness of the controller.