Performance Degradation of Discrete PID Controller for Digital Excitation Control System Due to Variation of Sampling Time

Modern digital AVR are consisting PID controller in forward path ensures fast response in the event of disturbance. Digital keypad is used for setting PID gains to improve performance of the system. Digital PID controller reads the error signal at regular interval unlike analog controller that reads the error signal continuously. Regular interval at which digital processor reads error signal is called sampling time that has substantial effect on the performance of the controller and consequently affects the stability of the power system where synchronous generator using digital excitation system is connected in parallel. This paper addresses the issues of variation of sampling time on the performance of digital excitation control system. Analysis is carried out using model of excitation control system, and result is duly validated using industrial controller board by using hardware in the loop experimentation.