Power system stability enhancement via STATCOM supplementary control based on fuzzy energy function

Following a disturbance, the machines in a stable power system initially oscillate, and then settle at the stable equilibrium point where the transient energy is zero. This paper aims at producing additional damping by means of by a fuzzy logic based static synchronous compensator (STATCOM) in coordination with a PSS. The stability of the system is evaluated by calculating the dissipation rate of the transient energy in post fault period. The control strategy of the STATCOM is selected very carefully to increase the rate of dissipation of the transient energy. The STATCOM´s supplementary controller is a fuzzy controller whose inputs are energy function and its derivative. The proposed approach is then successfully verified on Kundur´s four-machine two-area system.