International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-9 Issue-2, December, 2019 4963 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: B5140129219/2019©BEIESP DOI: 10.35940/ijeat.B5140.129219 ABSTRACT---Load frequency control (LFC) of an interconnected three-area power system with HVDC link under deregulated environment in presence of wind system is investigated. Integration of renewable sources in to exiting plants will affect the system frequency and hence design of a suitable controller is needed to maintain frequency within limits. Study of impact of wind penetration in to deregulated environment is a key factor. The secondary PID controller improves the overall system performance during sudden load disturbances and random variations of wind input. The optimal values of PID controllers in all three areas and pitch control in wind system are tuned by using Differential Evaluation (DE) algorithm. Keywords— frequency control, Restructured environment, Wind system, DE algorithm I. INTRODUCTION Maintaining of power system frequency is one of the important aspects in system operation and control [1]. Recently, the electric power industry is applying open market system in which consumers will have an opportunity to make a choice among competing providers of electric energy [2][3]. Open market system consists of generation companies, distribution companies, and transmission companies and independent system operator (ISO). In open market, distribution companies can contract individually with any generation companies under the supervision of ISO. DISCO participation matrix concept is used for understanding of contract implementation [4][5]. The impact of wind system under open market with AC-DC link are not examined thoroughly, therefore the authors have made an attemptthe effect of wind system for single objective function. The organization of the paper includes: Chapter-1 reviews the introduction of the load frequency control and existed methodologies under deregulated environment. Chapter-2 describes the three area six-unit system and mathematical formation of DPM. Also discusses the model of wind system. Chapter-3 discusses regarding proposed DE algorithm. Chapter-4 and chapter-5 discusses the simulation results and conclusion respectively. Revised Manuscript Received on December, 30 2019. G. Pavan Kumar, Research Scholar, Dept of EED, AU college of Engineering (A), Visakhapatnam, A.P., India (Email: gpavan16@gmail.com) R. Srinu Naik, Asst. Prof., Dept. of EED, AU college of Engineering (A), Visakhapatnam, A.P., India (Email:naiknaiknaik@gmail.com) Maheswara Rao Kesamsetty, Lecturer, JIGJIGA University,Jigjiga, Ethiopia. (Email: mahe.219@gmail.com) II. SYSTEM STUDIED The system studied consists of two non- reheat turbine thermal units in area 1 and the same in area 2 and two hydro units in area-3. The system is integrated with HVDC link and wind system incorporated at the terminals of all the areas. The configuration of the three-area power system under open market system is given in Fig.1. The reheat thermal system may be stated by equation (1)                                   p p t r r r g T sT K sT sT T sK sT s G 1 1 1 1 1 1 (1) Similarly, the hydro-turbine power system may be stated by equation (2)                                           3 3 3 2 1 1 1 1 1 1 1 1 p p w H sT K sT s sT sK sT s G (2) Wind System: The impact of renewable systems under deregulation is an important aspect. The output of wind turbine generator depends on the wind speed at that instant. When a wind turbine uses its pitch controller, its output power varies between maximum, or rated power, and zero power [14]. Pitch control parameters are controlled by controller whose parameters are tuned by DE and are shown in results section. The output of pitch control is given to hydraulic pitch actuator. III. CONTROL STRATEGY Differential evolution (DE) is developed by Rainer Stron and Kenneth Price in 1995 for optimization problems [16]. Differential Evolution (DE) algorithm is a simple, efficient search based heuristic algorithm. The flow chart for Differential Evaluation is considered from reference [17]. Integral Square Error (ISE) criterion is considered as objective function described in equation (3).             t tieij i dt P f ISE J 0 2 2 (3) DE Optimized LFC of Three Area Interconnected Power System with DFIG Wind System under Deregulated Environment G. Pavan Kumar, R. Srinu Naik, Maheswara Rao Kesamsetty