-85- 3 rd International Conference on Energy Systems and Technologies 16 – 19 Feb. 2015, Cairo, Egypt EVALUATION OF VOLTAGE FLICKER EMISSIONS OF VARIABLE SPEED DFIG-BASED WIND TURBINES Walid S. E. Abdellatif 1 , Ali H. Kasem Alaboudy 1 and Ahmed M. Azmy 2 1 Faculty of Industrial Education, Suez University, Suez, Egypt 2 Faculty of Engineering, Tanta University, Tanta, Egypt Wind-energy systems cause fluctuations more than any other sources and hence, voltage fluctuations are expected with these units. This paper addresses the problem of voltage fluctuation caused by doubly fed induction generators (DFIG)-based variable-speed wind turbines. Flicker emission of these units is investigated during continuous operation. The effects of grid strength, angle of grid impedance and site parameters, such as wind speed and wind turbulence, on voltage fluctuation are investigated. A flickermeter model, implemented according to IEC61000-4-15, and all system components are implemented in MATLAB/SIMULINK environment. Finally, a comparison between variable-speed and constant-speed technologies, related to short-term flicker severity is introduced. Keywords: Variable-speed wind turbines, DFIG, Maximum power point tracking (MPPT), Voltage flicker. 1. INTRODUCTION The growing demand for electric energy throughout the world has highly motivated the use of renewable sources of energy. Among the unconventional renewable-based energy sources that have been intensively studied, wind energy seems to have a vital role in the near future. Over the last ten years, the global wind energy capacity has increased rapidly and became the fastest developing renewable energy technology. Basically, there are many reasons for using more wind energy within power grids. For instance, wind generation represents a clean and renewable source with minimal running cost requirements [1]. Variable speed wind turbine (VSWT) topologies include many different generator/converter configurations, based on cost, efficiency, annual energy capturing, and control complexity of the overall system. The doubly-fed induction generator (DFIG) is the most commonly used device for wind power generation, The DFIG consists of a wound rotor induction generator (WRIG) with the stator directly connected to the grid, whereas the rotor is connected through a power electronic converter. The power converter controls the rotor frequency and thus the rotor speed. This concept supports a wide speed range operation, depending on the size of the frequency converter. Typically, the variable speed range is about ±30% around the