Research Article Rotor Speed Control of a Direct-Driven Permanent Magnet Synchronous Generator-Based Wind Turbine Using Phase-Lag Compensators to Optimize Wind Power Extraction Ester Hamatwi, 1 Innocent E. Davidson, 2 and Michael N. Gitau 3 1 Department of Electrical, Electronic and Computer Engineering, University of KwaZulu-Natal, University Road, Durban 4000, South Africa 2 Department of Electric Power Engineering, Durban University of Technology, Corner of Botanic Gardens and Steve Biko Roads, Durban 4000, South Africa 3 Department of Electrical, Electronics and Computer Engineering, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa Correspondence should be addressed to Ester Hamatwi; esterhamatwi@gmail.com Received 12 January 2017; Revised 30 March 2017; Accepted 20 April 2017; Published 28 May 2017 Academic Editor: Carlos-Andr´ es Garc´ ıa Copyright © 2017 Ester Hamatwi et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Due to the intermittent nature of wind, the wind power output tends to be inconsistent, and hence maximum power point tracking (MPPT) is usually employed to optimize the power extracted from the wind resource at a wide range of wind speeds. Tis paper deals with the rotor speed control of a 2 MW direct-driven permanent magnet synchronous generator (PMSG) to achieve MPPT. Te proportional-integral (PI), proportional-derivative (PD), and proportional-integral-derivative (PID) controllers have widely been employed in MPPT studies owing to their simple structure and simple design procedure. However, there are a number of shortcomings associated with these controllers; the trial-and-error design procedure used to determine the P, I, and D gains presents a possibility for poorly tuned controller gains, which reduces the accuracy and the dynamic performance of the entire control system. Moreover, these controllers’ linear nature, constricted operating range, and their sensitivity to changes in machine parameters make them inefective when applied to nonlinear and uncertain systems. On the other hand, phase-lag compensators are associated with a design procedure that is well defned from fundamental principles as opposed to the aforementioned trial- and-error design procedure. Tis makes the latter controller type more accurate, although it is not well developed yet, and hence it is the focus of this paper. Te simulation results demonstrated the efectiveness of the proposed MPPT controller. 1. Introduction Te increasing energy demand across the globe has led to an enormous interest in the cost-competitive, environmental friendly, and reliable renewable energy (RE) technologies to complement the conventional methods of generating electricity [1, 2]. Wind energy has recently been proven to be technologically mature and fast-growing among all other RE sources due to the growth in the size of commercial wind turbine (WT) designs and the increase in the installed capacity worldwide [2–12]. Modern variable speed wind energy conversion systems (WECSs) are based on doubly fed induction generators (DFIGs) and permanent magnet synchronous generators (PMSGs) [3]. Although the DFIGs are well developed and have previously been widely applied in WECS due to their ability to achieve variable speed control with the reduced cost of converter requirements, the use of slip rings and the protection issues in the event of grid faults are the major drawbacks [8]. As a result, the PMSG- based WECSs have gained more popularity and preference over DFIG-based WECSs owing to their advantages such as high energy density, simple control methodology, high reli- ability, low maintenance cost, and the self-excitation system [1, 13, 14]. Moreover, direct-driven multipole PMSGs have been adopted to exclude the gearbox, which improves the efciency of the WT and cuts down the weight of the nacelle Hindawi Journal of Control Science and Engineering Volume 2017, Article ID 6375680, 17 pages https://doi.org/10.1155/2017/6375680