Design of PID controller for automatic voltage regulator and validation using hardware in the loop technique

The digital excitation control system (DECS) used for brushless synchronous generators has recently become popular owing to its ease of operation and flexibility to manage the operating parameters to achieve good maintenance of the output terminal voltage at the rated value. The latest industrial digital automatic voltage regulator (AVR) is used in the forward path of DECS. This paper addresses the issues of the DECS that are responsible for deviating the terminal voltage from the rated value and consequently making the power system unstable. A solution to the issue is provided using a new method of tuning the PID controller that eases the impact of discretization on the terminal voltage and keeps the DECS compatible with industrial standards. The controller designed in this way will be useful to maintain the terminal voltage of the synchronous generator to enhance the stability of the power system to which many renewable energy sources are interconnected. The proposed method improves the performance of the excitation control system by reducing the overshoot from 75% to 16%. The simulation results are presented using an industrial standard model of the excitation control system to demonstrate and compare the performance of the existing with the new digital excitation system. The newly designed controller was tested and validated using the “hardware in the loop” (HITL) technique.