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Journal of Renewable Energy
Volume 2015, Article ID 978216, 10 pages
Research Article

Load Mitigation and Optimal Power Capture for Variable Speed Wind Turbine in Region 2

Department of Electrical Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore 575 025, India

Received 2 June 2015; Revised 20 August 2015; Accepted 7 September 2015

Academic Editor: Adnan Parlak

Copyright © 2015 Saravanakumar Rajendran and Debashisha Jena. This 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.


This paper proposes the two nonlinear controllers for variable speed wind turbine (VSWT) operating at below rated wind speed. The objective of the controller is to maximize the energy capture from the wind with reduced oscillation on the drive train. The conventional controllers such as aerodynamic torque feedforward (ATF) and indirect speed control (ISC) are adapted initially, which introduce more power loss, and the dynamic aspects of WT are not considered. In order to overcome the above drawbacks, modified nonlinear static state with feedback estimator (MNSSFE) and terminal sliding mode controller (TSMC) based on Modified Newton Raphson (MNR) wind speed estimator are proposed. The proposed controllers are simulated with nonlinear FAST (fatigue, aerodynamics, structures, and turbulence) WT dynamic simulation for different mean wind speeds at below rated wind speed. The frequency analysis of the drive train torque is done by taking the power spectral density (PSD) of low speed shaft torque. From the result, it is found that a trade-off is to be maintained between the transient load on the drive train and maximum power capture.