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Fuzzy Multi-Model Based Predictive Control for Offshore Wind Turbines

Sanaei, Behnam | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56622 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Sadati, Nasser
  7. Abstract:
  8. One of the main drivers for the substantial growth in wind energy utilization in the world is the growing demand for renewable energy sources to reduce greenhouse gas emissions. At greater distances from the coastline, more and steadier potential energy resources are available. This has led the world offshore wind energy industry to grow at a faster rate than onshore in the past two decades. In deep waters, the wind turbine is mounted on a floating platform, whose movements increase the complexity of the turbine control system and enhance the mechanical loads on the various components of the turbine. Reducing these mechanical stresses is equivalent to increasing the lifetime of the turbine and ultimately, reducing the final cost of energy production. In this thesis, a fuzzy multi-model based predictive controller is designed for offshore wind turbine with Spar-Buoy platform to operate in full load region. In this region, the wind power is greater than the nominal power of the turbine. As a result, the main objective is to limit the captured power from the wind by controlling blades pitch angle to adjust the generator speed. Generator torque is another actuator that can be used to improve output power quality. The second purpose is to reduce oscillations of the platform pitch in order to reduce the mechanical stress on the tower base. The main challenge in this control problem is the high interaction between the outputs of the generator speed and the platform pitch angle and the contradiction that accompanies these goals. Given the model-based controller, it is vital to use an accurate model that well describes the nonlinear behavior of the turbine. This motivated to develop a linear parameter varying model for wind turbines, utilizing the inherent ability of fuzzy logic in modeling nonlinear systems. The main advantage of this fuzzy modeling is its linearity, which decreases the computational cost of predictive controller. Rewriting the problem of finding the shape of membership functions in the form of an optimization problem, has minimized the number of fuzzy model rules. Also, relying on the physics of the problem, a new approach was used to formulate the cost function of the controller that resulted in its remarkable performance in damping the platform oscillations. Finally, the performance of this controller is evaluated using FAST simulator and its results are compared with the baseline controller
  9. Keywords:
  10. Wind Energy ; Offshore Wind Energy ; Floating Offshore Wind Turbine ; Spar Buoy Floating Platform ; Fuzzy Modeling ; Predictive Control ; Multi-Model Control

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