Appropriate generation rate constraint (GRC) modeling method for reheat thermal units to obtain optimal load frequency controller (LFC)

This paper focuses on choosing a suitable dynamic model for simulation of generation rate constraint (GRC) for load frequency control (LFC) of an interconnected realistic reheat thermal-thermal power system. Two different dynamic models for simulation of the GRC are investigated in details which are named as open loop and closed loop GRC models. These models have been used widely in literature interchangeably without any further description to the reason of selected modeling method and its suitability. This paper makes an attempt to help in choosing more effective and appropriate GRC structure pertained to reheat thermal units based on dynamic simulations to obtain optimal LFC. Reheat thermal units are examined with different GRC models. Then, integral of time multiplied squared error (ITSE) performance index is minimized by an improved particle swarm optimization (IPSO) algorithm to optimize proportional-integral-derivative (PID) controller parameters. All simulations are performed in MATLAB/SIMULINK environment. The results of eigenvalue analysis, dynamic simulations, and robustness analysis reveal the appropriate GRC modeling method for thermal units to attain high-performance and optimal LFC design.