IEEE, International Conference on Information, Communication, Instrumentation and Control (ICICIC – 2017) Paper Id: 279 A Robust PID Controller for Load Frequency Control of Single Area Re-heat Thermal Power Plant using Elephant Herding Optimization Techniques D K Sambariya Department of Electrical Engineering Rajasthan Technical University Kota, India 324010 Email: dsambariya_2003@yahoo.com Rajendra Fagna Department of Electrical Engineering Rajasthan Technical University Kota, India 324010 Email: rajendrafagna92@gmail.com Abstract—This paper presented a novel known as Elephant Herding Optimization for designing a load frequency controller for single area reheat thermal power plant to damping the oscillations of system frequency. The PID controller parameters are employed to search using Elephant Herding Optimization (EHO) techniques. The proposed controller for the power system is simulated in MATLAB/SIMULINK for a step change in load demand. The proposed method improves the performances of the power system in terms of time specifications such as settling time, overshoot and undershoot. Furthermore, it shows the robustness of the proposed PID controller under variation of system parameters. The performance is compared with the PID controllers in literature and found to be robust in performance. Keywords—Load Frequency Control (LFC), Frequency Deviation, Single Area Re-heat Power System, Proportional Integral Derivative (PID) Controller, Elephant Herding Optimization (EHO). I. INTRODUCTION The large-scale power system network is connected to several areas via tie-lines. Load Frequency Control plays a vital role for operating and controlling the power system. It is necessary for plant operator is to generate, transmit and distribute electric energy near to the standard value of system frequency and terminal voltages. The load frequency problem of a power system is occurred due to the unbalancing between the power generation and load demands. The unbalancing changes the system frequency. It is well known that the main motive of a power operator is to keep the system frequency within the nominal values. The conventional method of PID controller such as Ziegler- Nichols method, Cohen-Coon method, Fertik method, integral model control method (IMC) are used for damping the oscillation of frequency of the power system. In last decades, the researchers have proposed many control strategies based on soft computing techniques for load frequency control such as Bacterial Foraging Optimization Algorithm (BFOA) [1], Genetic Algorithm (GA) [1], Quasi- Oppositional Grey Wolf Optimization Algorithm (QOGWOA), Teaching Learning Based Optimization Algorithm (TLBO) [2]. The controller not only maintains constant frequency but also achieves zero steady state errors. Authors Anwar and Pan, 2015 [3] have designed a PID controller for solving the load frequency problem of re-heat thermal power system. Anwar and Pan compared the performances with other published paper PID controller. Padhan et al., 2013 [4] have designed a PID controller for LFC of single area power plant system using Laurent series. The parameters of PID controller are employed by the transfer function using Laurent series. Tan, 2010 [5] have proposed the application of unified tuning method of PID controller for LFC for single area reheat power system. Gozde et al., 2012[6] have presented the comparative analysis of LFC of multi-area reheat thermal power system using Artificial Bee Colony tuned PID controller. N. Sinha2008[6] suggested a PID controller for AGC of multi area reheat power system using GA. Magid et al., 2013 [7] have presented the use of Particle Swarm Optimization for deriving the parameters of PID controller for AGC. Authors Francis et al., 2012[8] have studied on the AGC for an interconnected reheat thermal power system using the neural network controller. Garg and Kaur [9]have designed a PID controller for AGC of the multi-area interconnected reheat power system. Farhangi et al. [10]estimated the LFC of inter connected power system using the intelligent controller. Sahu et al.[11] 2014 has used Fuzzy-PID controller for AGC of inter connected re-heat thermal power plant. The goal of this proposed work which is different from techniques in literature is that the Elephant Herding Optimization technique is used for LFC of the power system for deriving the parameters of the controller. The superiority of the controller is investigated comparatively by using different tuning methods for PID controller. This controller shows robustness at the change in system parameters. The proposed EHO based PID controller enhanced the performances of frequency deviation and tie line power. EHO presents a better fitter solution to benchmark function as compared to Bio- geography based optimization (BBO), DE and GA. II. PROBLEM FORMULATION A. System description The prototype of the single area reheat thermal power system with PID controller as shown in Fig 1. In re-heat thermal power plant, reheat turbines improved the efficiency of a power plant. The function of reheating turbines is steam is returned after partial expansion to the boiler for super heating and then allowable to expand the back pressure. The components of a reheat thermal power system are governor,