A novel fuzzy logic synchronous machine stabilizer

In this paper, the authors describe a novel fuzzy proportional integral derivative (PID) type power system stabilizer (PSS) that uses just the speed error and its rate of change as inputs. This was achieved by connecting an integrator at the output of a proportional derivative (PD) type controller which allowed the application of customized decision rules on the usually available expert knowledge. The developed fuzzy PSS uses a recently proposed defuzzification method which does not require fuzzy output membership functions and its crisp output is directly correlated with the inference rules. This allows the system response to belong to a desired class by directly modifying these rules. Hence, more adequate controls can be derived for various error cases and smoother control surfaces are achieved. The proposed PSS reduces the settling time and overshoot of the disturbed generation system and eliminates steady state error. Simulations have shown that its performance is superior to that of traditional and existing fuzzy PSS. The proposed PSS is coordinated with an AVR whose response is controlled using linear state feedback (LSF) to relocate its dominant poles according to supplied desired transient specifications.