A novel optimum PI controller design based on stability boundary locus supported particle swarm optimization in AVR system

Abstract

This study proposes a new approach that combines stability and optimization in the design of proportional- integral (PI) controller of automatic voltage regulators (AVR) of synchronous generators with variable system parameters. Thanks to this approach, a PI controller, providing the desired performance and the stability of the AVR system, has been designed. The approach follows a method investigating the PI gain values to achieve the desired goals. In the first step of the study, a new stability boundary locus is calculated for the case in which AVR system's parameters have changed. The stability boundary locus (SBL) method is a graphic-based technique and is used for the calculation of a new stability boundary locus curve. In this technique, the stable region is obtained by using the roots of the characteristic equation of the AVR system, so it depends on the parameters of the AVR system. In the second step, the controller gains are searched by the particle swarm optimization (PSO) algorithm modified with respect to the proposed approach. In the last step, in order to validate the efficiency of the proposed approach, the system has been optimized by the classical PSO and proposed SBL PSO. The comparative results of both optimizations have been presented. The results show that the proposed approach shortens optimization time by 20%. Thanks to this approach, the AVR system always runs at the desired performance and is always stable. It also substantially contributes to the implementation of optimization of closed loop control systems.