An adaptive fuzzy logic power system stabilizer

The paper presents an adaptive fuzzy logic power system stabilizer (PSS) design for damping oscillatory electromechanical modes of oscillations and enhancing the first-swing synchronous stability margins. The novel design utilizes a multivariable damping signal vector consisting of machine speed deviation, rate of speed deviation, and voltage deviation. The design is based on a multizonal PID structure and fuzzy logic variable-gain scheduling to optimize the damping action. The fuzzy logic PSS is proposed for use in parallel with the conventional analog type PSS with added simple switching criteria. The two PSS blocks can be allowed independent, sequential, and/or combined operation with different effective stabilizing weighting. The paper investigates an individual conventional PSS, a rule based fuzzy PSS, and hybrid operation. The parallel operation of a conventional PSS and a fuzzy logic one provides optimal sharing of the damping action under small- as well as large-scale generation-load mismatch or variations in external network topology due to fault or switching conditions.