Transient and voltage stability enhancement via coordinated excitation and UPFC control

The paper discusses co-ordinated excitation and UPFC control to improve power system transient stability and voltage stability. In the design of an excitation controller, the power system is linearised using a direct feedback technique. A robust approach is used to deal with the uncertainties caused by parameter variations and the inclusion of UPFC controller. Only local measurements are required for designing the excitation controller. The series branch of the UPFC is designed to damp the power oscillation during transients, while the shunt branch aims at maintaining the bus voltage. The performance of the proposed controller is tested on a single-machine, single-load power system. Simulation results show that the co-ordinated excitation and UPFC control is effective for transient stability enhancement. Both of the series and shunt branch control of UPFC help improve transient stability. The impact of the controller on voltage stability is studied through bifurcation analysis. It is shown that the feasibility region can be greatly increased