Adaptive Fuzzy Sliding Mode Control of Variable Speed Wind Turbine for Maximum Power Extraction R.SARAVANAKUMAR, DEBASHISHA JENA Department of Electrical Engineering National Institute of Technology Karnataka Surathkal Mangalore INDIA sarrajoom@gmail.com bapu4002@gmail.com Abstract: - This paper deals with nonlinear control of variable speed wind turbine (VSWT), where the dynamics of the wind turbine (WT) is obtained from single mass model. The main objective of this work is to maximize the energy capture form the wind with reduced oscillation on the drive train. The generator torque is considered as the control input to the WT. In general the conventional control techniques such as Aerodynamic torque feed forward (ATF) and Indirect speed control (ISC) are unable to track the dynamic aspect of the WT. The nonlinear controllers such as nonlinear dynamic state feedback linearization with estimator (NDSFE) and nonlinear static state feedback linearization with estimator (NSSFE) are not robust with respect to model uncertainty and disturbances. To overcome the above drawbacks a Fuzzy Sliding mode controller (FSMC) with the estimation of effective wind speed is proposed. The Modified Newton Raphson (MNR) is used to estimate the effective wind speed from aero dynamic torque and rotor speed. The proposed controller is tested with different wind profiles with the presence of disturbances and model uncertainty. From the results the proposed controller was found to be suitable in maintaining a trade-off between the maximum energy capture and reduced transient on the drive train. Key-Words: - Variable speed Wind turbine, Fuzzy Sliding mode controller, Modified Newton Raphson, ATF and ISC. 1 Introduction Because of the power crises and environmental issues, renewable energy sources play a vital role in energy market. Among all renewable energy sources wind energy is one of the rapidly growing energy technology and its having own benefits such as pollution free, clean and environmental friendly. In recent years due to the advanced in drive technology and grid interconnection control the production of wind power is increased. Generally WT has two different types i.e. fixed speed WT (FSWT) and VSWT. By comparing these two technologies VSWT is more versatile then FSWT. The main advantages of VSWT over FSWT are the reduction in mechanical stress and power fluctuations [1-2]. Generally wind speed is classified in to two types i.e. below and above rated wind speed. Accordingly the WT control is classified into two types i.e. torque control and pitch control [3]. At below rated wind speed the main objective of the WT is maximize the wind energy capture from the wind by rotating the WT rotor at optimal rotor speed which is derived from effective wind speed. Direct measurement of effective wind speed is not available because anemometer only measures the wind speed at a single point of the rotor swept area. At above rated speed the main objective of the WT is to control the pitch angles which are corresponding to the reference power. In literature some of the authors have discussed the control of WT with the assumption of measurement of effective wind speed. In [3] the design of WT control using linear parameter varying (LPV) gain scheduling technique is introduced. The above control technique is applied for both FSWT and VSWT. In [4] a fuzzy controller used to maximize the power capture, improve the efficiency, and the controller was found to be more robust to the wind gust and oscillatory torque. In [5] control algorithm i.e. fuzzy logic control (FLC) tracks the maximum power by controlling the WT rotor speed without estimation the effective wind speed. Several literatures have reported to estimate the effective wind with WT control. In [6] the rotor speed and aerodynamic torque are estimated by the input and state based estimation with the known pitch angle, the effective wind speed is calculated by the inversion of the static aerodynamic model. In [7-9] WSEAS TRANSACTIONS on POWER SYSTEMS R. Saravanakumar, Debashisha Jena E-ISSN: 2224-350X 281 Volume 9, 2014