Design and analysis of Linear Active Disturbance Rejection Controller for AVR system

Proportional Derivative Integral (PID) controllers are extensively used in most of the industrial applications. But often, PID frame work fails to address some serious issues like susceptibility to noise, instability due to integral term etc. On the other hand Active Disturbance Rejection Control (ADRC) addresses these issues quite successfully. The problem considered in this work is to control Automatic Voltage Regulator (AVR) with Linear ADRC (LADRC) under presence of plant parameter uncertainties and sudden load variations.A fifth-order Extended State Observer (ESO) was designed which estimates generalized disturbance which includes both system uncertainties and external disturbances. This information is used to actively cancel the effects of disturbances. The effectiveness of LADRC scheme has been illustrated by comparing with conventional PID tuning method in the presence of plant parameter and sudden load variations. Further to study the frequency response characteristics of control system, transfer function of LADRC has been derived. From the simulations it can be observed that there is significant improvement in system response which can be reconfirmed from the frequency response analysis.