Power quality assessment of wind turbines and comparison with conventional legal regulations: A case study in Turkey A. Tascikaraoglu, M. Uzunoglu, B. Vural ⇑ , O. Erdinc Department of Electrical Engineering, Yildiz Technical University, Barbaros Bulvari, Besiktas, Istanbul 34349, Turkey article info Article history: Received 28 July 2010 Received in revised form 6 November 2010 Accepted 1 December 2010 Available online 30 December 2010 Keywords: Wind turbines Power quality Flickermeter abstract Renewable energy sources have been investigated for use instead of conventional fossil fuels in many areas. Among these renewable energy sources, wind energy has come into prominence owing to the fact that it is a clean, sustainable and cost-effective type of energy. However, the connection of large wind farms to the grid may cause problems in terms of power quality due to the variability of the energy extracted from the wind. The mentioned power quality problems are generally taken into consideration after the grid integration of wind farms. However, the precautions that can be taken by means of the assessments before the installation of the turbines represent an easier and more economic way. In this study, the possible effects of the grid connected wind turbines on the power quality characteristics have been defined and the MATLAB based models have been constructed so as to calculate these effects. Par- ticularly, fast voltage variations that are difficult to model due to their relations with the human factor have been analyzed in detail. It has been aimed that the models are suitable for use in practice while uti- lizing various standards such as IEC 61400-21 and IEC 61000-4-15 in order to setup the models. The anal- yses of the implementations that represent constraints for exploiting the wind resources in Turkey have been realized in terms of production and consumption with a case study. The realized calculations pres- ent the applicability of the model to grid conditions with different characteristics. It is also presented that the wind energy penetration can be increased without deteriorating the power quality of the grid with the use of the proposed model. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The rapid depletion of fossil fuel resources and the rising public awareness for environmental protection on a worldwide basis have necessitated an urgent search for alternative energy sources. Par- ticularly, among the many types of competitive alternative sources of energy, wind power generation has experienced a very fast development in the whole world [1]. However, wind power may cause problems to the existing grid in terms of power quality [2,3]. One of the fundamental definitions to power quality prob- lems is any power problem manifested in voltage, current or fre- quency deviations that results in failure or miss operation of customer equipment [4]. Power quality decrement is generally caused by many factors such as impulsive and transients, over volt- age or under voltage variations, voltage imbalance, waveform dis- tortion, such as dc offset, harmonics, notching and noise, voltage fluctuation and frequency variations. In recent years, concern over power quality has increased significantly due to economic reasons and problems that can affect the manufacturing industries and the other customers [5]. Depending on wind turbine technology, there are different ef- fects that could damage power quality of a specific grid. Several Transmission System Operators (TSOs) have published grid codes for wind turbines. The codes require wind turbines and/or wind farms to participate in voltage regulation and frequency control. Also according to these codes, the wind power plants must be able to produce the required active and reactive power during transient grid fault to support the grid [6,7]. However in some situations, although the wind power plants provide the essential conditions, the limit values may be exceeded in terms of power quality. Thus, most of the countries have the rules such as that the wind turbines should not cause a voltage increment of more than 1% which limit the wind turbine installation to a specific grid [8,9]. Similar to that case, specifically in Turkey, a rule such as that the total wind power should not exceed 5% of the short circuit power of the grid is mostly applied [10]. Although these kinds of rules are usable for preventing the power quality problems caused by wind power in a grid, the wind power exploitation, particularly in weak grids is greatly decreased due to these rules. In order to increase the exploitation, it is quiet convenient to utilize the power quality standards for wind turbines, issued by the International Electro- technical Commission (IEC). With utilizing the standard IEC 61400-21, which defines the power quality characteristic of grid 0306-2619/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2010.12.001 ⇑ Corresponding author. Tel.: +90 212 383 2439; fax: +90 212 259 4869. E-mail address: bvural@yildiz.edu.tr (B. Vural). Applied Energy 88 (2011) 1864–1872 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy