Doubly Fed Induction Generators: Overview and Intelligent Control Strategies for Wind Energy Conversion Systems

Doubly Fed Induction Generators: Overview and Intelligent Control Strategies for Wind Energy Conversion Systems

Vinod Kumar, Steven Kong, Yateendra Mishra, Z.Y. Dong, Ramesh C. Bansal
DOI: 10.4018/978-1-60566-737-9.ch005
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Adjustable speed induction generators, especially the Doubly-Fed Induction Generators (DFIG) are becoming increasingly popular due to its various advantages over fixed speed generator systems. A DFIG in a wind turbine has ability to generate maximum power with varying rotational speed, ability to control active and reactive by integration of electronic power converters such as the back-to-back converter, low rotor power rating resulting in low cost converter components, etc, DFIG have become very popular in large wind power conversion systems. This chapter presents an extensive literature survey over past 25 years on the different aspects of DFIG. Application of H8 Controller for enhanced DFIG-WT performance in terms of robust stability and reference tracking to reduce mechanical stress and vibrations is also demonstrated in the chapter.
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2 Generator Overview

Wind technology has evolved over the years to today’s modern Wind Energy Conversion Systems (WECS) as shown in Fig. 1 (Chen and Blaabjerb, 2006).

Figure 1.

Main components of a wind turbine system (adapted from Chen and Blaabjerb, 2006)


All wind turbine systems are comprised of the components as shown in the Fig. 1. It is just a matter of including or excluding the optional components, which is decided by the application and the type of generator used. The generator forms the major link in converting mechanical power to electrical power. Induction generators are commonly used in such applications because of their major advantages such as reduced unit cost, ruggedness, reduced size, ease of maintenance and self-protection against severe overloads and short circuits (Chen and Blaabjerb, 2006; Bansal et al., 2003; Bansal, 2005; Simoes and Farret, 2004; Simoes and Farret, 2004).

The generators used in WECS can be categorized into two types: Fixed Speed Generators (FSGs) and Adjustable Speed Generators (ASGs). A novel detail on these generators is provided in Muller et al. 2002; Datta and Ranganathan, 2002; Holdsworth et al., 2003; Rodriguez et al., 2002; Badrzadeh and Salman, 2006). Overall, FSGs are more expensive in mechanical construction, especially at high- rated power as compared to ASGs, which are widely used in WECS.

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