PID, LQR, and LQG Controllers to Maintain the Stability of an AVR System at Varied Model Parameters

Abstract

This research demonstrates the time-domain performance characteristics of proportional-integral-derivative (PID), linear quadratic regulator (LQR), and linear quadratic gaussian (LQG) controllers when the gain parameters and time constants of an automatic voltage regulator (AVR) system change. We tuned the amplifier and sensor block gains and scrutinized the change in the stability. Also, we investigated the system response while the time constant of the amplifier, exciter, generator, and sensor blocks are set to their maximum permissible limit. We determined the eigenvalues of the system and observed that the location of close loop poles is very much susceptive to time constant variations. The LQG controller provides a comparatively faster and stable response than LQR and PID. When the gain parameters and time constants of the static AVR system are varied, the PID performance decreases significantly, but LQR and LQG can track the change rapidly. This analysis indicates that the impact of plant parameters on the controller response will be crucial while implementing the dynamic power system with distributed generators and interconnected grids.