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 compensation, of a unified power flow controller to improve the transient stability of a power system. The fuzzy rules for the controller are created based on a bang-bang control strategy whose objectives are minimising the first swing, damping the oscillations at an optimum rate, and maximising the transient stability margin. The proposed controller also incorporates a technique of reducing the chattering of generator output which naturally results from the application of bang-bang control. Simulation results show that the fuzzy logic based controller provides satisfactory performance, meeting the design objectives. The results also show the robustness of the controller.