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Optimal DC-link Voltage from Weight and Loss Perspective for eVTOLs

Abhijit Kulkarni, Torbjörn Thiringer, Remus Teodorescu

Abstract

Electric vertical takeoff and landing (eVTOL) aircraft are emerging as a modern transportation solution aimed at reducing urban traffic congestion and improving the carbon footprint. The power architecture in eVTOLs is defined by the dc bus formed by the battery packs and the power converter used to drive eVTOL motors. A high dc bus voltage is preferred for the power architecture since it can reduce the weight of power cables for a given power rating. However, the impact of high dc bus voltage on the efficiency of the drivetrain power converter must be considered, since reduced efficiency leads to poor battery pack utilization. In this paper, a systematic optimization study is performed considering SiC-based inverter for the drivetrain power converter. Optimal value of dc bus voltage is determined considering the flight profile of eVTOLs. A power converter topology is proposed that can provide optimal performance and enhance the lifetime of the batteries along with providing better monitoring, diagnostics and protection. The optimization strategy is validated experimentally, demonstrating the proposed power architecture's ability to maximize efficiency while enhancing the safety of the battery energy storage system in eVTOLs.

Optimal DC-link Voltage from Weight and Loss Perspective for eVTOLs

Abstract

Electric vertical takeoff and landing (eVTOL) aircraft are emerging as a modern transportation solution aimed at reducing urban traffic congestion and improving the carbon footprint. The power architecture in eVTOLs is defined by the dc bus formed by the battery packs and the power converter used to drive eVTOL motors. A high dc bus voltage is preferred for the power architecture since it can reduce the weight of power cables for a given power rating. However, the impact of high dc bus voltage on the efficiency of the drivetrain power converter must be considered, since reduced efficiency leads to poor battery pack utilization. In this paper, a systematic optimization study is performed considering SiC-based inverter for the drivetrain power converter. Optimal value of dc bus voltage is determined considering the flight profile of eVTOLs. A power converter topology is proposed that can provide optimal performance and enhance the lifetime of the batteries along with providing better monitoring, diagnostics and protection. The optimization strategy is validated experimentally, demonstrating the proposed power architecture's ability to maximize efficiency while enhancing the safety of the battery energy storage system in eVTOLs.
Paper Structure (11 sections, 16 equations, 19 figures, 5 tables)

This paper contains 11 sections, 16 equations, 19 figures, 5 tables.

Table of Contents

  1. INTRODUCTION
  2. DC Bus Voltage Optimization
  3. Power loss model for SiC-based drive inverter
  4. Modeling the impact of cable weight
  5. Proposed optimization
  6. Results
  7. Proposed Power Architecture
  8. Experimental Results
  9. Test for thermal model development
  10. Results with induction motor drive
  11. Conclusion

Figures (19)

  • Figure 1: Typical mission profile of an eVTOL.
  • Figure 2: Conventional power architecture in a multi-rotor eVTOL with FCC and BMS.
  • Figure 3: Conventional two-level three-phase drive inverter feeding eVTOL motor.
  • Figure 4: Cable cross sectional area versus current rating for 1.5kV rated dc power cables.
  • Figure 5: Radius of the copper in the power cable versus dc bus (battery) voltage for a 121hp motor.
  • ...and 14 more figures