Compact On-board Drivetrain-Integrated Level II Electric ... Recently proposed drivetrain composite

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  • Usama Anwar, Hyeokjin Kim, Hua Chen, Robert Erickson, Dragan Maksimović and Khurram K. Afridi Colorado Power Electronics Center, ECEE Department

    University of Colorado Boulder

    Compact On-board Drivetrain-Integrated Level II Electric Vehicle Charger

    SELECT Annual Meeting and Technology Showcase – Logan, Utah – September 27-28, 2016

    INTRODUCTION  On-board electric vehicle (EV) charger size and weight reduction helps:

     Incorporate higher power (Level II) on-board chargers

     Minimize vehicle styling constraints

     Reduce range anxiety

     Accelerate EV adoption

     Existing approaches to incorporate on-board Level II chargers:  On-board charger separate from drivetrain power electronics – adds excessive size and weight

     On-board charger integrated with drivetrain using traction motor windings – adds complexity, cost and reliability issues

     Recently proposed composite boost converter provides opportunity for new approaches for charger integration  Composite boost converter has superior performance than conventional boost converter

     Comprises buck, boost and DCX modules

     Utilizes lower voltage devices due to stacked nature

     Modular nature allows multiple options for on-board charger integration


    Architecture A

     Bridgeless Boost + PSFB converter

     Achieves low level of integration

     Only utilizes composite converter filter



    OPPORTUNITY  Goal of research is to identify and develop optimal way to integrate on-board charger with EV drivetrains utilizing

    composite boost converter:  Achieve on-board Level II charging functionality with minimal additional size and weight, while maintaining high efficiency

     Maximize reuse of existing drivetrain parts

     Minimize additional switches and passive components

    Architecture A

    Architecture B

    Architecture B

     Rectifier + PFC Boost Isolated DC/DC converter + Buck converter

     Achieves high level of integration

     Reduced efficiency due to hard switching in Isolated PFC Boost converter

    Architecture C

    Architecture D

    Architecture C

     Bridgeless Boost + DAB + Buck converter

     Achieves high level of integration

     Energy buffering at two places

    Architecture D

     Bridgeless Boost + DAB + Buck converter

     Three winding transformer reduces weight

     Achieves high level of integration

     Energy buffering at two places

     Architecture D selected as it offers best tradeoff between weight and losses

     Designed using Silicon super-junction FETs

     Interfaced with existing drivetrain by adding third winding to DCX transformer

     Energy buffering at two places reduces capacitor weight

     Added Module:

     PFC bridgeless boost converter + H-bridge + one transformer winding

     Proposed architectures compared in terms of added weight and losses

     Factors considered for comparison:  Weight of added charger module components:

    capacitors, inductors, heat sink

     Losses introduced by added components

    Architecture Added Weight [kg] Losses [W]

    A 2.67 238

    B 1.97 322

    C 2.07 268

    D 1.90 265

     Recently proposed drivetrain composite boost converter well suited for on-board charger integration

     Four alternative approaches for achieving charger integration explored and quantitatively compared  Selected charger architecture only adds bridgeless boost converter, one

    H-bridge and one extra winding to the existing converter

     PFC stage of the selected charger architecture uses a bridgeless boost converter  The converter is operated in DCM at 20 kHz

     Hybrid feedforward control architecture is used to achieve PFC functionality

     Effective zero crossing mitigation techniques employed to achieve natural commutation of input current between the half bridge legs

     Second stage DAB is controlled by introducing phase shift between primary and secondary H-bridges

     Third stage boost converter regulates battery power by controlling input current. Current reference is generated by sensing input voltage of the converter


    Measured zero crossing

     Hybrid feedforward control eliminates high bandwidth current sensor

     Control objective: 𝑖𝑖𝑛 𝑇𝑠 = 𝑣𝑖𝑛


     Inductor current

    𝑖𝑖𝑛 𝑇𝑠 = 𝑇𝑠 2𝐿

    . 𝑑2

    1 − 𝑣𝑖𝑛 𝑣𝑜𝑢𝑡


     Duty cycle modulation equation:

    𝑑 = 2𝐿

    𝑅𝑒𝑇𝑠 1 −

    𝑣𝑖𝑛 𝑣𝑜𝑢𝑡

     Zero crossing distortion mitigated by switching both switches with same duty cycle command around input voltage zero crossing


    Switching Waveforms

    Low Power

    6.6kW Results

    Input voltage and current and output voltage waveforms

    REFERENCES  U. Anwar, D. Maksimovic and K.K. Afridi,

    “Generalized Hybrid Feedforward Control of Pulse Width Modulated Switching Converters,” IEEE Workshop on Control and Modeling for Power Converter (COMPEL), Trondheim, Norway, June 2016.

     B. Whitaker, A. Barkley, Z. Cole, B. Passmore, D. Martin, T. McNutt, A. Lostetter, J. S. Lee, K. Shiozaki, “A High-Density, High-Efficiency, Isolated On-Board Vehicle Battery Charger Utilizing Silicon Carbide Power Devices,” IEEE Transactions on Power Electronics, vol. 29, no. 5, May 2014.

     J. Sun, “On the Zero-Crossing Distortion in Single-Phase PFC Converters,” IEEE Transactions on Power Electronics, vol. 19, no. 3, May 2004.

     R.W. Erickson and D. Maksimović, Fundamentals of Power Electronics, Second Ed., Kluwer Academic Publishers, 2001

    ISOLATION AND REGULATION STAGES Dual Active Bridge Isolation Stage

     Each half bridge switches at ~50% duty cycle

     Output voltage regulated by control of primary and secondary phase shifts

     ZVS can be achieved on both primary and secondary H-bridges

     DAB output capacitor performs energy buffering

    Input and output voltage waveform

    Boost Power Regulation Stage

     Regulates power flowing into the battery

     Controls input current and generates current reference by sensing input voltage

    Simulation Results

    Inductor current waveform

    Boost converter topology, model and control architecture

    Converter simulation waveforms