Loading...

Optimization of CLLC Resonant Converter for Increasing Reliability Considering Power Density of Bidirectional EV Charger

Fazli, Mohammad Reza | 2024

0 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57569 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Tahami, Farzad
  7. Abstract:
  8. With the proliferation of electric vehicles (EVs), the batteries in millions of EVs are anticipated to become the most cost-effective method of energy storage. By using a bidirectional charger, energy can be stored in vehicles during off-peak hours and then returned to the grid during peak consumption times. The CLLC resonant converter is a suitable circuit for bidirectional power conversion in applications like bidirectional EV chargers. This thesis aims to reduce power losses and increase operating frequency by incorporating wide bandgap (WBG) transistors. Additionally, the use of planar transformers is pursued due to their low profile and the capability to control both magnetizing and leakage inductance ratios, which is another key objective. Reliability is a critical performance metric in the design and manufacturing of electric vehicles. Reliability is defined as the probability that a product will perform its specified function without failure under specific conditions for a certain period. Due to the large number of interdependent components, the EV power electronics system is subject to various failure modes and mechanisms. At the system level, an EV charger designer must not only focus on the reliability of components like semiconductor switches but also consider aspects like the cooling system to ensure the designed charger performs reliably over the specified duration. Moreover, high power density and thermal losses directly impact system reliability; thus, reliability-centered design must be comprehensive and tailored to the battery charging profile used in each vehicle. In this thesis, to accurately calculate thermal losses and semiconductor switch stresses, results from time-domain analysis and the Nissan Leaf battery’s charging profile are used to ensure design precision. Time-domain methods are predominantly applied to LLC converters, where reliability and optimal design are thoroughly examined, but for the CLLC converter, the first harmonic analysis and numerical, statistical, and trial-and-error methods have been employed. The objective of this thesis is to design and construct a high-frequency CLLC converter using WBG transistors and planar transformers for bidirectional EV charging. The converter will feature high power density and efficiency (necessitated by the limited space in EVs) while being optimized for improved reliability. The reliability assessment of the CLLC converter will be based on the significance of various circuit components, following the 217plus handbook methodology. For validation, the designed charger—built to reduce losses and increase power density—will undergo voltage, current, and thermal stress analysis to evaluate the reliability of the converter. These results will then be compared with simulations and theoretical data. MATLAB is used for the optimization process, and the optimal inductor and capacitor values for the resonant tank are determined using Sequential Quadratic Programming (SQP) and Genetic Algorithm (GA) optimization techniques. In conclusion, the results obtained through MATLAB simulations and calculations demonstrate that the converter designed for enhanced reliability outperforms converters optimized solely for efficiency.
  9. Keywords:
  10. Wideband Gap Transistor ; Resonant Converter ; Reliability ; Optimization ; Electrical Vehicle ; Planar Transformer ; Galliume Nitride Semiconductor ; On-Board Battery Charger ; Sequential Quadratic Programming (SQP) ; Failure Rate ; Resonant Converter

 Digital Object List

 Bookmark

No TOC