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Common Mode Noise Reduction of LLC Resonant Converter with Planar Transformer for Electric Vehicle Applications

Pashaee, Mohammad Reza | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54730 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Tahami, Farzad
  7. Abstract:
  8. converters in electric vehicles, it is necessary to reduce their dimensions and increase their efficiency. It is expected that in the near future wide band gap semiconductors will be used to achieve these goals. On the other hand, usage of planar transformers is necessary to achieve slim and compact converter designs in electric vehicles. Clearly, planar transformers offer a significant advantage in replacing bulky wired transformers in high frequency LLC resonant converters with WBG transistors. planar transformers also have several other advantages, including low flux leakage, modular structure, and low thermal resistance.However, in planar transformers, due to the proximity and large area of overlap of the flat layers of the primary winding with the secondary winding, large parasitic capacitances are created between the layers. At high frequencies, parasitic capacitances are exposed to large dv/dt, which results in the generation of leakage currents, or common mode noise, that circulates between the primary and secondary windings through the ground and causes electromagnetic interferences with other electronic devices in electric vehicles.so although, increasment in frequency usually helps to reduce the size of the transformer, but to reduce the common mode noise, large common mode filter should be used. In this dissertation, a suitable solution for designing high frequency LLC resonant converter with planar transformer used in it to reduce common mode noise in electric vehicle application will be presented. This solution includes the optimization of the converter by selecting the most suitable structure, frequency, switches, resonant elements and transformer for the converter with the power and voltage used in the electric vehicle.In the proposed structure, because of using 3 phase structure, most noise source harmonics have phase difference of 120 degrees with each other, these harmonics are aggregated and neutralized at some points in the converter. Another advantage of the 3 phase structure is the reduction of parasitic capacitances in the converter transformer, due to the reduction of the transformer volume, which reduces the noise transmitted to the input and output of the converter by reducing these capacitors as the main conductors of electrical interference. In this dissertation to prove these theories, a 1ph fullbridge LLC resonant converter and a 3ph LLC resonant converter for the use of electric vehicle battery charger are built. These two converters have the same conditions in the input filter, output filter, resonant tank elements and other conditions. The conducted interference in the inpute of these two conververters have been measured in the same condition and as a result, the contents of the 3 phase structure have been proved and the common and differential mode conducted electrical noise have been reduced in the 3 phase structure
  9. Keywords:
  10. Resonant Converter ; Planar Transformer ; Electromagnetic Interference (EMI) ; Electrical Vehicle ; Common Mode Noise ; Wide Band Gap Semiconductors ; LLC Resonant Converter

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