Effect of nonlinear energy on wind farm generators connected to a distribution grid Labar Hocine * , Mekki Mounira Department of Electrical Engineering, Faculty of Engineering Sciences, University of Badji, Mokhtar-Annaba 23000, Algeria article info Article history: Received 29 September 2010 Received in revised form 1 February 2011 Accepted 5 March 2011 Available online 22 April 2011 Keywords: Wind Generator Power quality Impedance Errors abstract The wind farm generators are new energies sources in the Algerian electrical networks, as every project their placements are determined by the wind assets of the site suitability (economic evaluation), its proximity to the power grid of which it will be connected (technical assessments). The other problem which is not taken into account or not studied in a satisfactory way is the electrical environments in witch the wind generators are to be subjected. So it is shown in this paper, that in the case of a power distribution under strongly nonlinear loads, the wind farm presents difficulties in maintaining an acceptable power quality, due to the measurement apparatus errors incompatible to this type of non linearity. Wind generator MPPT are controlled and regulated mainly by 3 loops, based on active power, reactive power (sometimes substituted to a power factor) and bus bare voltage measurements. So, in this paper it is shown that in nonlinear condition these parameters are faultily measured. Thus, new relevant definitions and formulation of active power and true power factor correction with other types of power are proved and detailed in order to improve the governor wind farm energy management. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The concept of power quality was induced by the nature evolution of the loads [1]. Nowadays, they are mostly non-linear and sensitive devices. Power quality deals with measurements, analysis and improvement of bus bare voltage features, to preserve the sinusoidal waveform with constant RMS voltage and frequency [2]. The topic deals with study, evaluation and classification of harmonics interactions [3]. The concept of harmonics refers to the distortion of sinusoidal waveforms. These distorted waveforms are usually periodicals. By Fourier analysis, they can be expressed as a fundamental sinusoidal frequency component addition to other higher-order frequency sinusoidal components (i.e., the harmonics) [4]. Restricting the power quality application coverage, attention may be focused on specific kind of problems. This narrower defi- nition of power quality allows to focus on supply waveform prob- lems, its frequency and magnitude. Harmonic terminal voltages may be partially produced by the power generator itself (i.e. wind farm) and also, by non-sinusoidal load currents flowing through the internal impedance of the generator (load harmonics) [5]. Filters are often required at the terminals of AC power generating systems to remove these problems. Nowadays, harmonic pollution in electricity distribution systems is so serious that the quality of public supply becomes barely acceptable. In spite of poor quality of power supply, the connection of non-linear loads to the system is constantly increased. In some weak network areas, the voltage and current distortions are so large that it is essential to use filters to avoid damage or malfunction in sensitive electric equipment [6]. 2. Power quality indices under harmonic distortion Linear loads are those in which voltage and current signals follow each other very closely, such as the voltage drop that develops across a constant resistance, which varies as a direct function of the current that passes through it. This relation is better known as Ohm’s law and states that the current through a resis- tance fed by a varying voltage source is equal to the relation between the voltage and the resistance. On the other hand nonlinear loads are those in which the current waveform does not resemble the applied voltage waveform due to a number of reasons [3], i.e., the use of electronic switches that conduct load current only during a fraction of the power frequency period. Therefore, we can consider nonlinear loads as those in which Ohm’s law cannot describe the relation between V and I. Among the most common * Corresponding author. Tel./fax: þ213 3887 5398. E-mail address: hocine.labar@univ-annaba.org (L. Hocine). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2011.03.017 Energy 36 (2011) 3255e3261