Nonlinear Fuzzy Stabilizer Design for Power Systems with Time Delay

Due to the use of measurement devices and using communication links for transferring the measured data, time delays are usual problems in power systems. These time delays influence on small signal stability of systems and might decrease the damping of the low frequency fluctuations; hence, to have a desirable performance of power system stabilizer (PSS), the effect of time delays should be considered in design calculations. This paper investigates the effect of time delays on the small signal stability of a generator excitation control system compensated with PSS and by using T-S fuzzy control method, a PSS with inclusion of time delays in terminal voltage is designed. The stabilization conditions are obtained by suggesting delay-independent Lyapunov-Krasovskii functional in terms of Linear Matrix Inequality (LMI) and the controller gains are determined from numerical solutions of LMIs. The purposed stabilizer is tested on both single and multiple machine systems and the results are compared with the conventional stabilizers which generally neglect the effect of the time delays and with an adaptive delay compensator in design of which the effect of delays are taken into account. Simulations are performed by MATLAB software. The results of simulations show the efficiency of the presented stabilizer in comparison with conventional stabilizers.