Control of Variable Speed Wind Turbines in Islanded Mode of Operation

Nat. Tech. Univ. of Athens, Athens
IEEE Transactions on Energy Conversion (Impact Factor: 3.35). 07/2008; DOI: 10.1109/TEC.2008.921553
Source: IEEE Xplore

ABSTRACT Nowadays, technology evolution and deregulation of the electric utility industry enable distributed generation (DG) to play an increasing role in locally satisfying the expanding power demand. In this paper, the islanded operation of an electrical grid supplied by wind turbines, which belong to the most rapidly expanding DG technologies, is studied. Control strategies for power electronics interface of variable speed wind turbines, ensuring fast control of frequency and voltage, are proposed.

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    • "To overcome this drawback, gain scheduling or switching between multiple linear controllers has been proposed. In [4], the authors used a linearized version of the system and applied model predictive control, whereas in [12], [13] training of neural networks and fuzzy logic techniques were used. Even if in some cases the performance of the system is satisfactory, its response to large wind variations may be unpredictable, since these methods are based on linearization and hence are valid only locally. "
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    ABSTRACT: The main contribution of this paper is the development of a nonlinear control technique for the control of individual wind turbines in a wind farm. For this purpose, a control scheme based on feedback linearization and gain scheduled linear quadratic regulator (LQR) is applied to a horizontal axis, variable speed, pitch regulated wind turbine. As a result of the physical constraints of their components, wind turbines operate at different control modes with different control objectives. To capture this hybrid nature, a flexible modeling framework based on the notion of hybrid systems is introduced, and the developed controller is designed so as to operate in all modes and over a wide range of wind speeds. The performance and the efficiency of the proposed approach is validated via simulations, and is compared with standard LQR approaches.
    01/2011; DOI:10.1109/CDC.2011.6160709
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    • "Because they are not tower mounted they don't have access to the higher wind speeds that the HAWTs have and they also have the disadvantage that they possess a lower power coefficient than HAWTs. Not being able to rotate faster than the speed of the wind often means that extensive gearing is required to match the optimal speed of the rotor with that of the generator (Kanellos and Hatziargyriou, 2008; Mozammel, 1978; Mutschler and Hoffmann, 2001; Yeh and Wang, 2008; Yigang and Zhixin, 2008). "
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    ABSTRACT: The main objective of this work is to determine and design a suitable wind turbine which could be employed for rural homes or other small-scale applications. A variety of horizontal and vertical axis wind turbines exist, each possessing a number of advantages and disadvantages which needed to be taken into account before a basis for the design is selected. A small robust design which is relatively simple and cheap to construct is in essence the main criteria for wind turbine selection. A Savonius type rotor, which is a rotor based on a modification of the ā€˜Sā€™ rotor, is selected as it best fitted the design criteria. A small prototype 1.5 m tall with a rotor diameter of 0.65 m is designed and built. The finished prototype is used to estimate the power obtainable under normal operating conditions.
    Energy for Sustainable Development 09/2009; 13(3):159-165. DOI:10.1016/j.esd.2009.06.005 · 2.36 Impact Factor
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    ABSTRACT: Pitch system is a complicated nonlinear system disturbed by many uncertainties and is a key part of wind turbine system. When wind speed exceeds rated cut-in speed, pitch angle is changed to control wind power conversion efficiency, thus capturing rated power from wind and protecting wind turbine from damage. In this paper, based on the analysis of wind turbine aerodynamic, an active disturbance rejection based pitch controller for variable speed wind turbine is presented to improve performance of key turbine variables including pitch angle, turbine rotor speed, and power output. Based on turbine rotor speed feedback, an extended state observer is designed to estimate state variables and disturbances. To verify the performance of the proposed controller, simulations for different turbulent winds are carried out. Simulation results show high performance of proposed scheme for high-precision control of pitch angle.
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