EP/I038543/1 VEHICLE ELECTRICAL SYSTEMS INTEGRATION (VESI) PROJECT Phil Mawby University of Warwick
2 Facts & Figures EPSRC-funded project: 3.8 M Low TRL (1-3) to support EV technology development 10 partners 4.5-year project: Oct 2011-Mar 2016. To develop new EV technologies to meet challenges + opportunities facing the EV market. 6 research themes + 3 technology demonstrators Integrate electrical motor + power electronics: reduce cost/weight and increase power density improve reliability of electrical power systems maintain manufacturability for a mass market
Location of Research Groups
4 University Partners Experts in power electronics, electrical machines, and mechanical engineering Prof Phil Mawby (Warwick) Prof Phil Mellor (Bristol) Prof Keith Pullen (City) Prof Patrick Luk (Cranfield) Prof Emil Levi (Liverpool John Moores) Prof Andrew Forsyth (Manchester) Prof Volker Pickert (Newcastle) Prof Mark Johnson (Nottingham) Prof David Stone (Sheffield) Prof Andrew Cruden (Southampton)
Industrial Supporters 5
6 Six Research Themes 1. Power Semiconductors (Warwick) 2. Design Tools (Newcastle, City, Manchester) 3. Packaging (Nottingham) 4. Motors (Cranfield and Newcastle) 5. Converters (Manchester, LJMU, Newcastle, Southampton) 6. Passive components (Bristol, Manchester, Sheffield) Demo 1: Integrated Non- Rare-Earth High Performance Drive 311,982 Demo 2: Integrated Power Conversion for Reduced EMI 310,661 Demo 3: An Integrated Onboard Battery Charger using a Nine-phase Machine, with V2G Capability 269,437
7 Theme 1: Semiconductors Aim was to create lateral MOSFET devices with: o medium/high blocking voltages S Finger vs circular structure: o high current permits high torque, high acceleration Target = 1200V and 10A = for high performing EV power trains. Passivation Oxide Gate Source Al Gate Ti/Ni Source Ti/Ni Drain Drain Passivation Oxide Fabricated lateral MOSFET A bare die (12 mm x 12 mm) containing multiple devices Commercial 4H- SiC: 40cm 2 /V.s Achieved: Grew 3C-SiC on Si wafers for high current and HV power devices. Lateral MOSFET with a channel mobility of around 90 cm 2 /Vs which is much higher compared to 4H-SiC.
T junction ( o C) 8 Pipes containing the liquid-metal coolant. Achieved: Newcastle have integrated a cooling medium to a power module to cool power chips individually. Temperature fluctuation reduced by 10 o C using liquidmetal material has potential to double chip lifetime compared to conventionally cooled power modules. Power supply for the internal pump (no mechanical rotational component). 160 140 120 Power module and cooling circuit 100 80 Red chip temp. cycle new module Blue chip temp. cycle traditional module 60 Proposed with periodic flowrate Conventional with constant flowrate 40 0 5 10 15 20 25 30 35 40 Time (s)
Theme 3: Packaging 9 Sintering process Multi-layer flex connect with sintered SiC JFETs AlN substrate with Ag nano-paste Basic power module cell (1200V, 80A, 150 khz) with integrated filter capacitors and Cu inductor coils soldered onto same DBC substrate as SiC devices. 9 Thermal image of integrated inductor under test at 100A/mm 2 DC-DC power converter, 300V In, 0-250V out, 52kW max rated power (12.8 x 16.3 x 3.3 cm)
Theme 4: Motors In-wheel direct-drive permanent magnet synchronous machine (PMSM) based on rare-earth PM (<1 krpm) o Pros: No gearbox or transmission system, so space for battery. o Cons: high-temperature demagnetization; expensive; restricted supply. In-wheel Motor Motor Controller Energy Source 10 Medium-speed high-performance PMSM using ferrite PM (5 krpm) o Pros: Working temperature 100⁰C higher than rare-earth PM, excellent corrosion resistance, low cost o Cons: low-temperature demagnetization; fragility; energy density (BH)max only 1/10 of rare earth). Medium-speed ferrite rotor Stator for in-wheel rare-earth PM motor High-speed switched reluctance machine (50 krpm) o Mechanical integrity design and analysis to ensure rotor safety and to improve the overall power density of the machine. High-speed SRM stator
Theme 5: Converters Investigate integrated on-board charger with bidirectional power flow for battery charging and V2G operation. Can use single-phase (slow), 3-phase, and multiphase charging (fast). No separate charger, instead RE-USE the pre-existing magnetic components and inverter installed for driving mode. No torque produced while charging. Advantages: Fewer new elements lower cost Lower weight faster vehicle Less space needed smaller vehicle Can use any type of power socket V2G operation helps with providing stored electricity to the grid 1 1
12 Achieved: Developed a thermo-electric design optimisation tool to demonstrate energydense wound components. Established high fidelity models to accurately analyse parasitic loss effects due to gap fringing and AC winding losses. Investigated alternative methods of cooling and heat extraction within wound components, including alternative encapsulates and heat spreaders. VESI filter inductor prototype: - 80 μh inductance - 200 A rated current - 400 Hz operating frequency - SiFe core - Aluminium conductors - 2.5 kg weight Interleaved DC-DC converter inductor incorporating gap loss mitigation Inductor Design Energy density Commercial 0.1-0.2 J/kg Publications 0.2-0.8 J/kg VESI 1.2 J/kg Encapsulated component
13 Integrated Non-Rare-Earth High Performance Drive Total Funding: 311,982 Demonstrator Project 1 Objectives: To develop a high performance ferrite motor with full functional integration with its converter. Mechanical and thermal integration of the motor and the controller. Theme 2: Design Tools (Newcastle, City, Manchester) Theme 4: Motors (Cranfield and Newcastle)
Overall Demo 1 Design 14 Material weight Cost (inc. manufacture) Rare-earth motor (with Demo 1 specs) Lamination: 9.0 kg Cu wire: 1.2 kg Rare earth PM: 0.75 kg Total = ~11 kg Demo 1: Ferrite PM motor Lamination: 12.0 kg Cu wire: 1.7 kg Ferrite PM: 1.0 kg Total = ~15 kg High. Rare-earth PM = 50/kg Low. Ferrite PM = 7/kg Nominal rating: 20 kw at 10,000 rpm (max. 20,000 rpm). Cross-sectional view of the final assembly Overview of the final assembly. Integration of controller board on top.
Stator Assembly Employ Nippon Steel 0.2mm lamination 20HTH1200 to minimize the stator core loss at high rotational speed. 15 Stator lamination with windings Partially assembled stator Aluminium casing DC capacitor and power module (converter and DSP inside) mounted on Al casing on stator
16 Integrated Power Conversion for Reduced EMI Total Funding: 310,661 Demonstrator Project 2 Objectives: Save weight and volume through having a sealed enclosure and shared cooling circuit. Reduce electromagnetic emissions by using filters and Al enclosure. Reduce the passive component size to reduce converter size and increase power density. Theme 3: Packaging (Nottingham) Theme 6: Passives (Bristol, Manchester, Sheffield)
By mounting the main power conversion elements within a single enclosure, with appropriate 17 power and signal filtering, the associated EMI challenges can be eliminated. Integration at least a 20% reduction in volume and weight. COLD PLATE LAYOUT DC-DC converter Power module for traction motor FPGA control board Bi-directional DC-DC converter interface to 30kW supercapacitor buffer store
18 An Integrated On-board Battery Charger using a Nine-phase Machine, with V2G Capability Total Funding: 269,437 Demonstrator Project 3 Objectives: To develop a working prototype system of an onboard charger with bi-directional power flow. To develop a high-power-density power converter, based on WBG devices. To design control software for charging and V2G functionality. Theme 3: Packaging (Nottingham) Theme 5: Converters (Manchester, LJMU, Newcastle, Southampton)
Theme 5: Converters (LJMU) 19 Concept is applied to 5,6, and to 9-phase configurations. three-phase grid v ag+ v bg+ v cg+ i ag i bg i cg EMI filter (onboard ) S 1 S 2 hardware reconfig. i ag i bg five-phase machine b i cg i bg /2 d c a i cg /2 i ag i bg /2 i cg /2 i c i b i a i e i d v c v b v a v e v d i dc i c v dc C i L BAT e Switches open grid is connected and can charge the battery. Switches closed grid is disconnected, so the inverter can perform propulsion control of the machine.
Demo 3: An Integrated On-board Battery Charger using a Nine-phase Machine, with V2G Capability 20 Oscilloscope displaying waveforms Laptop DSP control unit Grid voltage sensor 10 x 12V, 40Ah LiFePO 4 batteries 7.5kW DC/DC converter and ninephase inverter Nine-phase induction machine
21 Conclusions 1. Completed the research into the underpinning technology. 2. 55 publications. 3. Investigated ways to reduce cost, increase power density, improve reliability of electrical power systems. 4. Applied the research to creating three demonstrators. 5. Desire to take the three demonstrators to higher TRLs. www.warwick.ac.uk/vesi