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Analysis and Enhancement of Low Voltage Ride Through Of Wind Turbines with Brushless Doubly Fed Induction Generator

Gholizadeh, Mahyar | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 50506 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Oraee Mirzamani, Hashem; Tohidi, Sajjad
  7. Abstract:
  8. Wind energy technologies guarantee low pollution and operational costs. Using a DFIG and a fractionally rated power electronics converter gives variable speed operation with a low cost drive train. As energy policy organizations have allocated a considerable quota of wind energy generation to offshore wind farms, the absence of slip rings and brushes in the brushless DFIG (BDFIG) is an advantage for offshore wind turbines where maintenance is vital and expensive. With increasing wind power penetration in power systems, grid code requirements are an important consideration for the ride-through capability of wind farms through voltage dips, particularly for multi- MW wind turbine generators. In view of these requirements, wind turbine generators must have the ability to remain connected to grid and to play a role in reactive power control during the faults occurrences, in order to provide voltage compensation of the point of common coupling. Therefore, the Brushless Doubly-fed Induction Generator (BDFIG) has high potential for wind energy systems, especially for offshore applications. The machine low voltage ride through (LVRT) capability in the light of current grid code requirements was investigated using a precise dynamic model. This thesis shows the necessity for improvements of the BDFIG LVRT capability with presenting a comprehensive analytical study during voltage dips. Moreover, an accurate method for parameter extraction of BDFIG equivalent circuit model is proposed and its performance is verified by experimental measurements. Analytical studies are conducted to extract a more precise equivalent circuit model of the BDFIG used for analyzing machine dynamic behavior under various fault conditions. In addition, a comparison between different voltage dips is performed to identify critical operating points for LVRT assessment. This study also proposes effective approaches for determining appropriate protection to be able to improve the brushless doubly fed induction generator ride through capability during any voltage dip scenarios. Important limits and constraints in the use of crowbar and Series Dynamic Resistor (SDR) are identified and discussed in detail. The results of the study are verified by coupled-circuit model, simulated in MATLAB/SIMULINK for a BDFIG prototype
  9. Keywords:
  10. Low Voltage Ride Through (LVRT) ; Brushless Doubly Fed Induction Machine ; Crowbar ; Coupled Circuit Model ; Series Dynamic Resistor ; Asymmetrical Voltage Dips

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