1 Analysis of Voltage Flicker due to Fixed Speed Wind Turbines Mehdi Mardani Abolfazl Jalilvand Kazem Mazlumi Electrical Engineering Department, Zanjan University Zanjan, Iran Keywords: Fixed speed wind turbines, voltage flicker, power fluctuation Abstract This paper presents an analysis of flicker emission from fixed speed wind turbines. Flicker emissions and power fluctuations of the wind turbines are compared in different conditions. At first, a wind farm connected to a network is considered and voltage fluctuation of that is formulated. Then, wind speed model is presented. At last, a wind farm connected to a network is simulated and flicker emission in the PCC and power fluctuations are analyzed in the Matlab/Simulink environment. In this paper, effects of variations of the following parameters are analyzed on the flicker emission and power fluctuations: 1) the line parameters; 2) the number of wind turbines in the wind farm along with wind characteristics; 3) the wind farm rated power. 1. Introduction Perfect power quality means that the voltage is continuous and sinusoidal having a constant amplitude and frequency [1]. Power quality is expressed in terms of physical characteristics and properties of electricity. It is often described in terms of voltage, frequency and interruptions. The quality of the voltage must fulfill requirements stipulated in national and international standards. In these standards, voltage disturbances are subdivided into voltage variations, flicker, transients and harmonic distortion [2]. Grid-connected wind turbines affect power quality. It has been established that the two main influences of wind turbines on the grid, with respect to power quality, are voltage fluctuations and harmonics [3]. Voltage fluctuations cause corresponding changes in the brightness of the light sources, known as flicker. Flicker produces very unpleasant visual sensations, leading to complaints from utility customers. The power quality depends on the interaction between the grid and the wind turbine (wind farm). Fixed speed wind turbines also produce voltage fluctuation and flicker [1]. This is because of the variability characteristics of the wind. Wind turbines produce a torque that is not constant during a revolution of the rotor, due to different aerodynamic effects such as tower shadow, yaw error, misalignment, wind shear, etc [4]. As a result, an output power drop occurs three times per revolution for the three-bladed wind turbines. This frequency is called the 3p frequency. The power pulsations of fixed-speed wind power generators get up to one-fourth of the average power at the frequency of 3p [4]. These power oscillationsproduce voltage fluctuations at PCC (Point of Common Coupling). Voltage flicker can become a limiting factor for connecting wind turbines at weak networks [5]. Different factors can affect on the voltage quality of the wind generators such as characteristics of the line that connects the 11-E-PQA-1974