Study on the improvement of generators capabilyty in control of power system stability by ASPAC

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The object of this project is to analize the negative dampimng phenomena in the electric power system from the viewpoint of internal behavior of magnetic flux, to develop a new concept of its monitoring and control, and to scrutinize some of the practical problems associated with engineering implementation of this concept.Results in this study are summarized as follows:A. Analysis of negative damping phenomena caused by high-response AVR. The basic essential features of the interaction among electrical torque, air gap flux, and rotating speed in the synchronous machine during dynamic oscillationswere made clear. This result forms the basis for understanding the machine's physical behavior related to dynamic stability more precisely than ever.B. Monitoring of dynamic stability. Monitoring of dynamic stability and prediction of negative damping could be successfully made by calculating changes in both the damping torque coefficient and the synchronizing torque coefficient directly from measured data such as electrical torque, air gap flux, rotating speed and so on.C. Control scheme of dynamic stability. It was confirmed by both experiment and simulation that the proposed control scheme for canceling the undamping effect of AVR and extending the stability limit worked effectively in the one-machine connected to an infinite system. It was also made clear that these functions, accompanying by the previously developed one for steady-state stability, would contribute to add up the capability of ASPAC( Automatic Stability Prediction and Control) in enhancing the power system stability. But further research about the feasibility in the multi-machine system, which was beyond the scope of this project, will still be needed to apply this scheme eventually to the real electric power system.