Grid Frequency Regulation and Stability Using Load Frequency Control in Power Plants
Unstable grid frequency impedes grid power system security, reliability and stability. Frequency outside the predefined range results to overheating, increases vibration, and destroys turbine shaft & blades. Underfrequency destroys equipment of consumers. Loadfrequency controller is used to create the balance between load and generation of each control area by means of speed control. In this work, frequency deviation problem associated with load frequency control is analyzed by Genetic Algorithm (GA) tuned proportional integral controller (PID) for Afam two area power system. MATLAB codes were developed for GA based PID controller tuning, the results of which were used to study the system step response. Three cases were considered during the load perturbation and the system frequency performances based on the settling time, rise time and % peak overshoot were analyzed. Initially the system was run without the use of the controller (i.e., with all the PID gains = 0) and with a load change of 10% in area 1, and it is found out that the system is unstable. But the introduction of GA tuned PID controller improved the power system dynamic responses as zero ACE was achieved. It is observed from the result that frequency reached steady state value within reasonable time (around 12 sec), peak overshoot was well below 25%, and rise time was around 0.5seconds. This illustrates that the improved technique (GA tuned PID controller) provides a lasting solution to the frequent grid frequency instability, caused by mismatch between load demand and generation, which threatens system security, reliability and stability.