International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 03 Issue: 11 | Nov -2016 www.irjet.net p-ISSN: 2395-0072 © 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 427 A Review on Different Pitch Angle Control Methods for Wind Turbines Sunil Kumar 1 , Gagan Deep Yadav 2 1 M-Tech Scholar, YIET Gadhauli, India 2 Assistant Professor, YIET, Gadhauli, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - This paper summarizes current research and applications of wind turbine individual pitch control, reviews the basic concepts and working principles of individual pitch control methods, analyses the individual pitch control strategies for reducing the load, and mitigating grid voltage fluctuations, finally, the possible development prospects of wind turbine individual pitch control are discussed. Key Words: individual pitch control; pitch angle; unbalanced load; power fluctuations 1. INTRODUCTION Wind turbines develop to large-scale with the installed capacity of wind turbines rapidly develop, Currently offshore wind turbines have a diameter of over 100 meters. Such as: the wind turbines Vestas V164-8MV was produced by VESTAS company, it has diameter of 177m and length of 80m for each blade, the first prototype unit was installed in northern Denmark in January 2014[1], and the first industrial units are scheduled for installation in 2016 off the coast of the UK[2]. The rotor blades to produce a wide range of moments, at the same time, wind turbine blade have to subject to turbulent, wind shear, tower shadow etc. The impacts become more significant with the diameter increase, large-scale wind turbines are subject to more complex unbalanced load. When megawatt generators runs at rated wind speed, the absorbed power can be 20% difference [3], between the highest position and lowest position of the wind turbine blade. The unbalanced load aggravates the mechanical stress and shortens lifetime of wind turbine, at the same time, the output power of wind turbines will fluctuate. Currently, the pitch control has been implemented for large and medium-sized wind turbines. In general, the wind turbine blade pitch angles are adjusted in response to random variation of wind speed, so as to realise the optimum utilization of wind energy within a certain range of the wind speed. The pitch control may be classified into two types, collective pitch control and individual pitch control. In a collective pitch control system implements to synchronization adjustment control system, all the three blades of a wind turbine are adjusted in the same speed and the same degree. Obviously collective pitch control cannot be well adjusted to the above situation. Clearly, only individual pitch control can solve the above problems, because each blade has a set of independent variable pitch drive system in Individual pitch control system, and can be adjusted to the different situation of each blade. 2. CURRENT RESEARCH AND APPLICATION OF THE INDIVIDUAL PITCH CONTROL TECHNOLOGY Individual pitch control has been studied since the beginning of this century, after the development in a few years, some of universities, research institutes and industrial companies have now involved the research and development about the individual pitch control. Such as: Aalborg University in Denmark, Technical University of Denmark, Vestas Wind Systems A/S in Denmark, GL Garrad Hassan in the United Kingdom, Shenyang University of Technology, North China Electric Power University, State Key Laboratory of Fluid Power and Control at Zhejiang University and also researchers at Norway, Germany, France, the United States, the Netherlands, New Zealand and other countries have conducted the research activities, and obtain a lot of results about the individual pitch control. At present, the most studies of individual pitch control are at the stage of the simulation, a number of studies get into a stage of the semi-physical simulation, a very few of research and development studies are in the stage of field test. Such as: In China, State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University and Zhejiang Windey Wind Generating Engineering Co., Ltd. jointly conducted VSCF individual pitch control research and development based on semiphysical simulation[4] In China Hangzhou, State Key Laboratory of wind power system and Zhejiang Windey Co., Ltd. Hangzhou have conducted the joint simulation study and field test on individual pitch control technology of large scale wind turbine[5]. In UK, validation of individual pitch control by field tests on two- and three-bladed wind turbines has been reported.[6] The results demonstrate convincingly that the predicted load reductions can be achieved in practice; the output voltage has been stabilizing too. 3. THE FOUNDATION OF INDIVIDUAL PITCH CONTROL Wind energy is converted into mechanical energy by the rotation of the wind rotor that is driven by the wind, then mechanical energy drives generator to output power.