A variable-structure adaptive fuzzy-logic stabilizer for single and multi-machine power systems

This paper proposes a new power system stabilizer based on adaptive fuzzy systems. The new controller is a fuzzy-logic-based stabilizer that has the capability to adaptively tune its rule-base on line. The change in the fuzzy rule base is done using a variable-structure direct adaptive control algorithm to achieve the pre-defined control objectives. This algorithm has two merits. First, it has a good performance in the training phase as it makes use of the initial rule base defined for the fuzzy logic stabilizer. Second, it has a robust estimator since it depends on a variable structure technique. The adaptive nature of the new controller significantly reduces the rule base size and improves its performance. This statement is confirmed by simulation results of a single-machine infinite-bus system under different operating points and exposed to both small and large disturbances. Extension to the multi-machine case is also included to illustrate the effectiveness of the proposed stabilizer in damping oscillations that follow a three-phase to ground short circuit.