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The paper discusses coordinated excitation and UPFC control to improve power system transient stability and voltage stability. In the design of an excitation controller, the power system is linearized 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 easurements 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, singleload
power system. Simulation results show that the coordinated 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 control of series and shunt controllers. It is shown that the feasibility region can be greatly increased.

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