Vehicle Electrical Systems Integration (VESI) Project Prof Phil Mawby University of Warwick

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1 EP/I038543/1 Vehicle Electrical Systems Integration (VESI) Project Prof Phil Mawby University of Warwick

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3 Overview Background VESI project summary Six research themes Three demonstrator projects

4 EPSRC funding: 3,154,532 VESI project summary Low technology-readiness level (1-3) to support EV technology development 1 October 2011 to 30 September 2015 Overall objective = to have a fully integrated vehicle electrical power conversion system. VESI project focuses on electrical motor and power electronics Key issues: Reduce cost, increase power density, improve reliability of electrical power systems, maintain manufacturability for a mass market. Underpinning basic research divide problem into 6 research themes. 3 technology demonstrators (Oct 2013 to Sep 2015) provide a physical realisation of the research outputs from the themes.

5 Location of Research Groups 3

6 Car manufacturing companies Energy supplier Semiconductor manufacturers Component Manufacturers Consultancies Key Industrial Supporters

7 Six Research Themes

8 Warwick Newcastle, City, Manchester, Sheffield Nottingham Newcastle, Cranfield Manchester, Southampton, Liverpool JM, Newcastle Bristol, Manchester, Sheffield Demonstrator 3: An Integrated On-board Battery Charger using a Highly Integrated Drive and a Nine-phase Machine, with V2G Capability Demonstrator 2: Integrated Power Conversion for Reduced EMI Demonstrator 1: Integrated Non-Rare-Earth High Performance Drive

9 Theme 1 Power Semiconductors (Warwick) Grow layers of 3C polytypes of Silicon Carbide (SiC) on a Si wafer using Warwick s SiC epitaxial reactor. Develop 1200V lateral Schottky power diodes and 1200V lateral metal-oxide semi-conductor field-effect transistors (MOSFETs).

10 2D Device Modelling N+ 3C N 3C-SiC P Si 4 μm 1.1e16 cm μm 1e15 cm-3 2 MV/cm Cathode Field Plate Anode Lateral Electric Field at Contact Interface 2D simulation show promising results: breakdown voltage of 1870 V and forward current density of 426 A/cm2. Vertical Electric Field

11 Approach: Theme 2 Design Tools Step 1 Step 2 Step 3 Characterise missing electrical, thermal and mechanical links of today s simulators Select missing links and describe effects analytically and validate by experiments. Of particular interest is: Prediction of convective heat transfer in electric machines Physics-of-failure based models of new assembly techniques Loss mechanism and heat removal in inductors for dc/dc converters Development of new heat removal techniques Of particular interest is: Cooling plate with locally changing thermal impedances High thermal conductivity potting compounds

12 Comparison of valve techniques SMA spring (SAES Group, Italy) Solenoid valve (Orion Valves Ltd, Japan) Micro-valve (Kemikro, Germany)

13 Theme 3: Packaging and Integration Multi cellular approach to high power Multiple smaller switching cells Reduced commutation loops System performance (overshoot / EMI) ensured by physical design Circuit simulations EMI / switching behaviour comparison of VESI modular topology with traditional power modules Finite element extraction of parasitic inductances result in a reduction in commutation inductance by an order of magnitude Integrated inductance demonstrator rig: High inductor current density achieved (100A/mm 2 ) Energy density 2.5 times typical inductor using a ferrite core material Validation of thermal simulations Convection coefficients used in thermal models fine tuned following tests on the integrated inductance

14 Double sided structure Inductors soldered into place

15 Theme 4 Motors (Professor Patrick Luk, Cranfield University) Rare Earth in-wheel Permanent Magnet Synchronous Machine Electromagnetic optimization with different poleslot combinations by Particle Swarm Optimization (PSO) Further electromagnetic optimization based on NEDC to achieve cycle Magnetic radial force and vibration analysis of the machine Mechanical design of the final optimal machine Ferrite Interior Permanent Magnet Synchronous Machine Electromagnetic Optimizations with different magnet layer numbers for flux enhancement Rotor mechanical integrity analysis at maximum operational speed Performance comparison with rare earth counterparts

16 WP5 Converters AC-DC and DC-AC converters Analysis of multi-function topologies for traction drive and grid-linked battery charging (LJM) DC-DC converters Analysis of instability in dual interleaved boost converters (Ncl) Comparison of topologies for 48 V auxiliary supplies (Mcr) Vehicle-to-grid systems Hardware-in-the-loop testing of communication channel and algorithms for vehicle-to-grid control (Soton)

17 Theme 6 Compact passive components High fidelity reduced order thermal models for wound components (Bristol PDRA) Implementing thin strip aluminium windings in wound components (Sheffield PhD) Use of lumped elements gives high accuracy (compared to experiment) and significantly reduced computational times (compared to FEA) Aluminium oxide insulation Improved loss models for DC inductors with nanocrystalline cores (Manchester PhD) Thermal image of inductor

18 Three Demonstrator Projects

19 Demonstrator Project 1: Integrated Non-Rare-Earth High Performance Drive PI: CoI(s): Professor Patrick Luk (Cranfield University) Professor Volker Pickert (Newcastle University) Professor Keith Pullen (City University) Dr Weizhong Fei (Cranfield University) Start Date: 01/10/2013 Duration: 18 months Industry support: Liberty E-Tech; Scorpion Power Systems; Motor Design Ltd.

20 High Performance Ferrite Motor The Design Tools and the Motors themes join forces to develop a high performance ferrite motor: with full functional integration with its converter incorporating Smart cooling in the power converter for the motor undertaking mechanical and thermal integration of the motor and controller Rotor mechanical integrity (stress limitation) Sufficient PM air-gap flux density (flux focussing) Expensive materials such as rare earth permanent magnetics will be mitigated and even eliminated. Efficiency of converter (PWM frequency) Rotor pole number Rotor complexity Aspect ratio (rotor inertia)

21 Motor assembly design Water cooled aluminium cast body, with integrated cooling passages for semiconductors. Oil lubricated bearings. Oil pumped using centrifugal action. No internal fan required. Helical cooling fins on motor body maximise heat transfer by returning water from left to the right of the motor. The outer jacket casting surrounds the fins and forms the semiconductor heat sink plenum.

22 Demonstrator Project 2: Integrated Power Conversion for Reduced EMI PI: CoI(s): Professor Phil Mellor (University of Bristol) Professor Andrew Forsyth (University of Manchester) Professor Mark Johnson (University of Nottingham) Start Date: 01/10/13 Duration: 24 months Industry support: Jaguar Land Rover; Motor Design Ltd; IST Power Products; Lyra Electronics; Tirius.

23 Challenges/Objectives Provide an integrated, optimised, controllable converter interface for at least three elements within the on-board electrical system, each element having dissimilar and variable voltages Integrate multiple functional elements: a propulsion converter; a high power bi-directional DC to DC converter; and high voltage distribution and EMI filters, within a single enclosure sharing a common cooling circuit. Aim to demonstrate: Improved electromagnetic compatibility between the units Significantly reduced electromagnetic emissions compared to the individual elements Volume and weight saving through a shared enclosure and cooling, and system weight benefits from higher semiconductor switching speeds. 0.43J/ kg Investigated the optimal geometry of filter inductor for minimum weight and packaging. Al windings and thin SiFe laminates offer performance /weight benefits. 0.76J/ kg

24 Scope and responsibilities Power module test bench is now under construction. Power module for control FPGA control boards DC to DC converter for a 30kW buffer store Main power module. Modular switching cells for high power conversion 24

25 Demonstrator Project 3: An Integrated On-board Battery Charger using a Highly Integrated Drive and a Nine-phase Machine, with V2G Capability PI: CoI(s): Professor Emil Levi (Liverpool John Moores University) Professor Andrew Cruden (Southampton University) Dr Lee Empringham (University of Nottingham) Start Date: 01/10/13 Duration: 24 months

26 Objective 1 Develop a working prototype system that enables bi-directional power flow and uses the same hardware components in propulsion, battery charging, and V2G operation. Progress made: laboratory prototype of the demonstrator has been assembled, control developed for all operating modes and tested with a nine-phase induction machine. Completed power module Three phase output boards Three gate driver boards High current DC-DC converter A nine-phase inverter motor drive system and dc-dc boost converter One of the three 3-phase converters with gate driver board (positioned on top) FPGA based control system Measured values sent back to main controller and displayed on Human-Machine Interface

27 Human-Machine Interface Touch screen control and visual display of: Battery voltage DC bus voltage Power Flow (To/From Grid) Power module temp. Each 3 phase output DC-DC converter module Converter status indicator Trip signal display 27

28 Battery charging current i L (A) Speed (rpm) Battery charging current i L (A) Speed (rpm) Objectives 2 and 3 Develop a high-power-density modular power converter that serves as the power interface between the dc source (battery) and the machine in propulsion mode, i.e. grid (charging and V2G). Design hardware and software for laptop/dsp communication to enable automated demonstrator operation with rapid 2-way data transfer and visual display in wired/wireless modes. 2 i L Speed Speed Time (s) -2 0 i L Time (s) Battery current and machine s speed during charging (left) and V2G modes (right) Transition from charging to V2G operation

29 Lab Based V2G Demonstrator Looking at compression algorithms to help implement V2G comms on 3G/4G networks. Basic demonstration GUI developed in C++ to showcase the main functionality of the V2G interface. Software updated : main UK map now segmented into smaller regional areas allowing demand and vehicle availability to be seen in the areas..

30 Summary 10 Leading Universities 6 Fundamental Underpinning technologies 3 Demonstrators Better Vehicle Electrical Systems integration