Journal of Power Sources 205 (2012) 354–366 Contents lists available at SciVerse ScienceDirect Journal of Power Sources jou rnal h omepa g e: www.elsevier.com/locate/jpowsour Coordinate operation of power sources in a doubly-fed induction generator wind turbine/battery hybrid power system Raúl Sarrias a , Luis M. Fernández b , Carlos A. García b , Francisco Jurado c,∗ a Industrial Technologies Research Institute, University of Cádiz, 11202 EPS Algeciras, Algeciras (Cádiz), Spain b Department of Electrical Engineering, University of Cádiz, 11202 EPS Algeciras, Algeciras (Cádiz), Spain c Department of Electrical Engineering, University of Jaén, 23700 EPS Linares, Linares (Jaén), Spain a r t i c l e i n f o Article history: Received 5 September 2011 Accepted 1 January 2012 Available online 25 January 2012 Keywords: Wind power Battery Hybrid system Modeling Control system a b s t r a c t This paper deals with the modeling and control of a hybrid system integrating a doubly-fed induction generator (DFIG) wind turbine and batteries as energy storage system (ESS). The modeling of the mechan- ical and electrical main components of a 1.5 MW wind turbine is described. Specific focus is to be taken on the power converter of the DFIG, since it allows the interconnection of the ESS to the generator and a proper energy management. A lead-acid battery is used as energy storage device, which is connected through a bidirectional DC/DC converter to the DC bus of the DFIG power converter. A new supervisory control system, responsible for the coordinate operation of power sources (DFIG wind turbine and ESS), is described and evaluated by simulation under wind speed fluctuations and grid demand changes. It is based on using the wind turbine as primary power source and the ESS as auxiliary power source, provid- ing or storing the power mismatching between the actual wind power and grid demand, whenever the battery state-of-charge (SOC) remains within the recommended limits. This configuration increases the generation capability and smooths the output power fluctuations caused by the wind speed variability, and therefore, improves the grid integration of wind turbines. © 2012 Elsevier B.V. All rights reserved. 1. Introduction In the recent years, wind power generation is experiencing a remarkable growth in terms of installed power and energy gen- eration in many countries. USA and China are currently the world leaders in installed wind power [1]. In Europe, Germany and Spain lead the total cumulative installed capacity. The expansion of this renewable resource has also led to important improvements in the technology of wind turbines and auxiliary equipment. Nonethe- less, wind power generation presents certain characteristics that hamper a broader penetration, especially in weak grids [2–4]. Since wind energy is based upon a natural resource, it is an intermittent, uncontrollable, and, to some extent, unpredictable energy source. Therefore, many authors have dealt with the uncertainty that a high penetration of wind power in electric power systems involves [2–7]. Energy storage systems (ESS) are regarded as a viable solu- tion to some of these problems [2–5,8–11]. In [10,12–15], different aspects of several energy storage technologies are studied for wind ∗ Corresponding author. Tel.: +34 953 648518; fax: +34 953 648586. E-mail addresses: raul.sarrias@uca.es (R. Sarrias), luis.fernandez@uca.es (L.M. Fernández), carlosandres.garcia@uca.es (C.A. García), fjurado@ujaen.es (F. Jurado). power and other renewable energy applications. Some devices, such as batteries, flywheels, superconducting magnetic energy storage (SMES), supercapacitors, compressed air energy storage (CAES), hydropumped storage or hydrogen technology, are con- sidered appropriate for reducing the power output fluctuations in wind farms. Among them, batteries are known to provide an ade- quate behavior with high power or energy requirements [16,17]. Furthermore, lead-acid batteries are the oldest and most mature technology [14–17], and have shown acceptable performance in large scale applications [16]. For these reasons, they have been chosen in this work to operate coordinately with the wind turbine. For variable speed wind turbines, DFIG and permanent magnet synchronous generator (PMSG) are the most outstanding technolo- gies [18–21]. Their modeling and simulation together with different ESS has been addressed in [4,21–24]. However, in some of these cases [4,21,22], the ESS is placed somewhere between the wind tur- bine output and the grid, which contrasts with the ESS location and energy management philosophy proposed herein. Currently, the most widely used wind turbine is based on a DFIG, since it operates at variable speed by the use of a partial power converter of 25%–30% of the generator-rated power, which makes it advantageous from an economic point of view. Furthermore, this system allows reac- tive power compensation and smooth grid connection [18–20]. For these reasons, a DFIG has been considered in this work. Its struc- ture allows connecting the ESS to the DC bus, within the generator 0378-7753/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2012.01.005