Expert system for enhancing voltage security/stability in power systems

The paper presents an expert system for enhancing both the voltage security and the voltage stability in power systems. The expert system is implemented to improve the voltage profile when contingencies are less severe and to adopt appropriate control actions to prevent the system from collapsing when severe contingencies are encountered. The sensitivity for a change of the load voltage to a variation of the on-load-tap-changer (OLTC) tap is used to verify the requirement of locking OLTC taps for operators. A new model, incorporated with variables for both the real power and the terminal voltage, for the reactive-power limit of a generator is presented for the voltage-stability studies. A real 256-bus system is used to serve as an example for demonstrating the performance of the proposed expert system