Step-wise optimum adaptive variable-structure load-frequency control design using simulated annealing

This paper presents three optimum adaptive variable-structure controllers and their applications to load frequency control (LFC) of an interconnected power system, namely, optimum Dither (DT), optimum Proportional-Integral (PI), and optimum Variable Input (VI) control. The aim of this work is to maintain robustness while reducing the chattering effect in Variable Structure Control (VSC) at the same time fulfilling the LFC requirements. Contrary to the widely used trial-and-error technique, the proposed approaches allow the determination of the controller gains systematically and adaptively in a step-wise fashion using simulating annealing, a well known robust optimization technique. The VSC gains computation problem is converted to an optimization problem using a suitable cost function that is based on Lyapunov theory of VSC. Comparison study is carried out between the proposed approaches as applied to the power system subjected to disturbances variation and parameters change with the presence of the system inherent nonlinearity.