This paper proposes a new Artificial Intelligence technique known as Harmony Search (HS) for
optimal tuning of PID controllers for Load Frequency Control (LFC). The system proposed here is a three area
with reheat thermal system containing nonlinearities represented by Generation Rate Constraint (GRC), Dead
Band and Boiler Dynamics. The proposed system has been chosen especially to mimic typical system
behaviour in actual operation. Four different generations (versions) of HS have been used for tuning the PID
controllers. The closed loop response of the system using the optimized PID gains has been compared with
another one tuned by Genetic Algorithm (GA). Simulation results significantly verify that the sample controller
can favourable performance and contribute efficiently enhancing the system dynamic behaviour.