Published in IET Electric Power Applications Received on 13th August 2008 Revised on 4th June 2009 doi: 10.1049/iet-epa.2009.0071 ISSN 1751-8660 Three-phase doubly fed induction generators: an overview M. Tazil 1 V. Kumar 2 R.C. Bansal 3 S. Kong 3 Z.Y. Dong 4 W. Freitas 5 H.D. Mathur 6 1 School of Engineering and Physics, The University of the South Pacific Suva, Fiji 2 Electrical Engineering Department, Maharana Pratap University of Agriculture & Technology, Udaipur, Rajasthan, India 3 School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia Campus, Qld 4072, Australia 4 Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong 5 Department of Electrical and Computer Engineering, State University of Campinas, Sa ˜o Paulo, Brazil 6 Electrical and Electronics Engineering Group, Birla Institute of Technology and Science, Pilani, Rajasthan, India E-mail: rcbansal@ieee.org Abstract: Adjustable speed induction generators, especially the doubly fed induction generators (DFIG), are becoming increasingly popular due to their various advantages over fixed speed generator systems. A DFIG in a wind turbine has the ability to generate maximum power with varying rotational speed, ability to control active and reactive power by the integration of electronic power converters such as the back-to-back converter, low rotor power rating resulting in low cost converter components, and so on. This study presents an extensive literature survey over past 25 years on the different aspects of DFIG. 1 Introduction Most of the electricity generated today uses non-renewable sources of fuel such as coal, oil and gas. These contribute to large quantities of CO 2 to the atmosphere, and cause an enhanced green house effect, leading to the warming of the earth’s atmosphere. The increasing rate of depletion of conventional energy sources has increased emphasis on renewable energy sources to provide the growing demand. The adverse effects of conventional systems have given rise to a shift in focus towards renewable energy sources such as wind, solar, hydro, tidal wave, biomass, and so on. As already known, renewable energy sources have virtually no adverse effects on the environment. The Global Wind Energy Council (GWEC) [1] states that wind energy developments has occurred in more than 70 countries around the world, with an installed capacity of 94,189 MW in 2007, with an increase of 27% from 2006 to 2007. The use of a doubly fed induction generator (DFIG) is becoming more and more popular for the generation of power from large wind systems. This paper presents an overview on various aspects of DFIG. The paper is organised as follows. Section 2 presents the generators overview. Sections 3 and 4, respectively, discuss DFIG, its equivalent circuit and modelling. Various control techniques and software simulation/hardware experimentation on DFIG have been discussed in Sections 5 and 6, respectively. Sections 7 and 8 present DFIG applications in grid connected and isolated systems, respectively. Section 9 presents some references on the various aspects on which some research has been carried out. Finally, important conclusions on DFIG are presented in Section 10. 2 Generator overview Wind technology has improved over the years to today’s modern wind power conversion systems as shown in Fig. 1 [2]. All wind turbine systems are comprised of the components shown in 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 IET Electr. Power Appl., 2010, Vol. 4, Iss. 2, pp. 75–89 75 doi: 10.1049/iet-epa.2009.0071 & The Institution of Engineering and Technology 2010 www.ietdl.org