Comparison of 5th order and 3rd order machine models for doubly fed induction generator (DFIG) wind turbines J.B. Ekanayake a,c, *, L. Holdsworth b , N. Jenkins b,c a Department of Electrical and Electronics Engineering, University of Peradeniya, Peradeniya, Sri Lanka b The Manchester Center for Electrical Energy (MCEE), UMIST, Manchester, UK c Tyndall Center for Climate Change Research, Norwich, UK Received 24 September 2002; received in revised form 28 March 2003; accepted 1 April 2003 Abstract With increasing concern over climate change, a number of countries have implemented new renewable energy targets, which require significant amounts of wind generation. It is now recognized that much of this new wind generation plant will be variable speed type using doubly fed induction generators (DFIG). In order to investigate the impacts of these DFIG installations on the operation and control of the power system, accurate models are required. A fifth order and reduced order (3rd) machine models are described and the control of the wind turbine discussed. The capability of the DFIG for voltage control (VC) and its performance during a network fault is also addressed. # 2003 Elsevier B.V. All rights reserved. Keywords: Machine models; DFIG; Wind turbines 1. Introduction The exploitation of the wind as a source of renewable energy continues to increase with some 25 GW of wind turbine capacity installed worldwide. In some countries the penetration of wind energy is such that already it is a significant fraction of generation capacity and projec- tions of future installations indicate that the number of wind turbines will increase rapidly over the next 10 years. Hence, wind farms must be included in computer simulations to study both the development and opera- tion of the power system. At present variable speed operation of wind turbines, using doubly fed induction generators (DFIG), is emerging as the preferred technology. This is due mainly to the reduced mechanical loads on the wind turbines that arise from variable speed operation [1]. However, a secondary advantage is the increased possibilities of control of both real and reactive power to allow easier integration of wind turbines into the power system. In comparison to conventional synchronous genera- tion, wind power is developed in relatively small units. Typical wind turbine ratings vary between 800 kW and 3 MW with wind farms ranging from 1 to 200 MW. Thus it is important to determine the simplest possible models of wind turbines that give an accurate representation in the various studies that are undertaken on the power system. In this paper a comparison is made between a 5th order model of the DFIG wind turbine and a 3rd order representation where the stator transients are neglected. The development of the models is described and it is shown that for dynamic modeling the 3rd order model is adequate. For detailed representation of fault current contribution, the 5th order model provides better resolution although it must be recognized that the behavior of the converter control systems is likely to have a dominant effect on fault currents. 2. Doubly fed induction generator (DFIG) DFIG wind turbines utilize a wound rotor induction generator, where the rotor winding is fed through back- to-back variable frequency, voltage source converters. A * Corresponding author. Electric Power Systems Research 67 (2003) 207 /215 www.elsevier.com/locate/epsr 0378-7796/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0378-7796(03)00109-3