Online and offline load frequency controller design

Abstract

A good quality of electric power system is that both the frequency and voltage remain at the desired values during operation and transmission of power. If the load power changes, the frequency will oscillate and deviate from its rated value, leading to instability issues. Thus, a design of efficient load frequency control (LFC) is needed to maintain the frequency constant against continuous variation of loads, which is also referred as unknown external load disturbance. A proportional-integral-derivative (PID) controller has been used for decades as the load frequency controller to keep frequency approximately at the nominal value by tuning the proportional, integral and derivative gains of the PID controller. In this paper, we propose two methods to tune the PID controller. The first method is online tuning based on neural networks and the second method is offline tuning based on particle swarm optimization. The two tuning methods are applied on a single and two interconnected power areas. Both tuning methods are compared with each other and both show good performance in terms of the overshoot, undershoot and settling time, but online tuning method gives better results in damping out the frequency deviation compared to the offline tuning method.