DE optimized parallel 2-DOF PID controller for load frequency control of power system with governor dead-band nonlinearity

Abstract

In this paper, design and performance analysis of Differential Evolution (DE) algorithm based parallel 2-Degree Freedom of Proportional-Integral-Derivative (2-DOF PID) controller for Load Frequency Control (LFC) of interconnected power system is presented. A two area thermal system with governor dead-band nonlinearity is considered for the design and analysis purpose. The design problem is formulated as an optimization problem and DE is employed to search for optimal controller parameters. Conventional and modified objective functions are used for the design purpose. Conventional objective functions employed in the paper are Integral of Time multiplied by Squared Error (ITSE) and Integral of Squared Error (ISE). In order to further increase the performance of the controller, a modified objective function is derived using Integral Time multiply Absolute Error (ITAE), damping ratio of dominant eigenvalues, settling times of frequency and peak overshoots with appropriate weight coefficients. The superiority of the proposed approach has been demonstrated by comparing the results with a recently published technique, i.e. Craziness based Particle Swarm Optimization (CPSO) for the same interconnected power system. Further, sensitivity analysis is performed by varying the system parameters and operating load conditions from their nominal values. It is observed that the proposed controllers are quite robust for a wide range of the system parameters and operating load conditions from their nominal values. Finally, the proposed approach is extended to a more realistic power system model by considering the physical constraints such as time delay, reheat turbine, Generation Rate Constraint (GRC) and governor dead band.