Chattering attenuation analysis in variable structure control for automatic voltage regulator with input constraints

Abstract

The present paper deals with the chattering attenuation analysis in Variable Structure Control (VSC) for Automatic Voltage Regulators (AVR). As the VSC suffers from the chattering phenomenon, the performances of the soft switching functions are investigated. Signum, saturation, tangent hyperbolic, and fractional approximation functions are used in the proposed controller, and optimum controller parameters are found out separately with Sine Cosine Algorithm. In the definition of the objective function, the overshoot of the step response is restricted by 0.5%. Since every real system has input constraints, the control input and the exciter of the linear AVR model are limited by the direction of IEEE recommendations. It is observed that the calculated control inputs are cropped at the upper and lower limits of the control input. Identical robustness measurements to the previous studies are performed, and the results are compared to each other. While the signum-based switching control exhibits undesirable oscillation, the smooth functions contribute highly acceptable control input. Among the soft switching functions, the tangent hyperbolic and saturation functions are more prominent concerning the disturbance rejection and parameter uncertainties.