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Wind Turbine Transformer Design Improvement to Resolve Its Transient Concerns

Elhaminia, Pedram | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51215 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Vakilian, Mehdi
  7. Abstract:
  8. One of the special regimes of a wind turbine transformer operation is its repetitive connection and disconnection from the wind turbine (or the grid) via a short length of cable. Energizing the transformer will stress the transformer in two ways: the passage of inrush currents, and the initiation of possible high frequency resonances in the windings. In this thesis, first the 3D-wound core transformer design is investigated as a mean for reduction of the transformer inrush currents drawn from the grid. It is shown that this desirable performance is due to H-balance equation in this type of core and therefore the transformers of this type preserve a suitable response under energization to be employed for wind turbine transformer applications. In the next step, the effect of design parameters; including: the disk spaces, the turn insulation thickness and the distance between LV and HV windings; on the high frequency response of the winding is studied. For simulation of those design parameters effects; the equivalent RLC ladder network is utilized for the high frequency modeling of the transformer. Using these simulation results, it is shown that reducing the equivalent series capacitance and increasing the equivalent shunt capacitance will have adverse effects on the high frequency response which is compatible with the current insulation design practice of the manufacturers. The multiple-design algorithm for manipulation of the transformer frequency response is introduced (through which designers can achieve many acceptable designs). Using this method the expected frequency responses could be evaluated in advance, and the best pattern among those can be selected for the wind turbine transformer design. Finally, it is concluded that: the best way to control the values of the resonance frequencies is to change the distance between LV and HV windings, and the best way to control the resonance amplitude factor is to use multiple design algorithm. The proposed methods are verified against a real, dry type, 3D wound core wind turbine transformer of 400 kVA, 20 kV/ 690 V
  9. Keywords:
  10. Inrush Current ; Resonance ; Frequency Response ; Wind Turbine Transformer ; Three Dimentional Wound Care ; RLC Ladder Network ; Multiple Design Algorithm

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