Electric Drives Challenges and solutions for the future Robert Eriksson Nikitas Sidiropoulos Swedish Hybrid Center WS Challenges with electric drives for vehicles Lund 2014-04-04 1
VCC Electrification plan/ World leading PHEV VCC s history and Future regarding Electrification Efficiency in focus for 40 years Hybrid and Plug-In Hybrid vehicles studied and implemented World first Diesel PHEV BEV Test Fleet cars, C30 Electric We plan for massive renewal of our product program with Electrification as a key ingredients 2
Strategies for VCC 2015 Green Connected Safe 3
Efficiency & Electrification CO2 reduction Kinetic Energy Recovery CO2 fleet average - 95 g by 2020 Finding optimum customer benefit at lowest possible added cost Plug-In Technology Implications from Feature growth New attributes added Increased electrical power higher efficiency. ZEV mandate Local/regional requirements Robustness to dynamic load 4
Electric Drives Challenges and solutions for the future Nikitas Sidiropoulos M.Sc. Electric Drives System Leader Volvo Car Group April 4th, 2014 5
Electric Drives Present solutions V60 PHEV Future eawd PHEV CIDD ISG IEM erad EM Generator power / 270-420 V Front Electric Drive System Inverter: IGBT power modules (bondless) gen I Electric Machine: PMSM Traction power / 270-420 V Rear Electric Drive System Inverter: IGBT power modules (bonded) gen I Electric Machine: PMSM 6
Electric Drives Challenges of the future Advantages - Proven technology - High performance and driveability - Electric efficiency and range. Technical and commercial challenges - Double Inverter and Electric machine systems high system cost - Expensive HV components such as HVAC cables and connectors - EMC / EMF - Thermal performance and lifetime of IGBT modules - Scaleability - Battery energy still expensive further efficiency improvements needed - Switching noise - PMSM rare earth element cost fluctuation - Compactness 7
Electric Drives Future solutions How do we face the technical and commercial challenges? Technologies under investigation: - Single Inverter and Electric Machine system topology impact - Maximisation of common parts of Inverter and Electric Machines in different platforms / topologies - Integrated Inverter and Electric Machine - Next generation power module (bondless, more efficient, scaleable) - Increased switching frequency / reduced IGBT losses with new materials such as SiC / GaN - Electric Machine with reduced REE content 8
Electric Drives Future solutions efad/hyfad Single Electric Drive system Maximisation of common parts with erad topology C30 EV Future EV Future FWD PHEV Advantages - Single Electric Drive system reduced system cost - Inverter parts commonality with ISG/eRAD topology - Strategic partnership with Electric Drive system supplier Challenges - Increased complexity (Electric Machine transmission interface) - Engine bay package 9
Electric Drives Future solutions IED Integrated Electric Drive Inverter and Electric Machine as one unit Integrated cooling and housing Using next generation of power module Package protected for all targeted platform variants Close co-op with strategic partner Decision for production pending Advantages - Elimination of HVAC cables, connectors, brackets... part numbers and cost reduced - Significant weight reduction - Free space can be used for spare wheel or increased luggage capacity - Improved EMC - Common parts with Front Electric Drive components - C/o Electric Machine from present solution - Could be used for both erad and efad topology - Could be an enabler for high power charger Challenges - Vibration withstandability of power electronics - Packageability in engine bay (HyFAD topology) - Investment - Scaleability 10
Electric Drives Future solutions Next Gen power modules Next generation power module (~2017) From bonded wires bondless technology Sintered no solder joints Reduced conduction and switching losses by use of more efficient chip Improved scaleability (phase current rating 400 700 A, voltage rate 650 V) Power cycling and life time studied with in-house developed software tool (rainflow analysis of IGBT and Diode delta Tj) Increased in-house SW control Advantages - Improved thermal performance and life time (~8 x higher for VCC customer profile) - Reduced inverter losses and improved vehicle duty cycle efficiency (range & CO2) - Package protected Challenges - IGBTs in <200 V region (Mosfet can be more efficient but no commonality with 400 V) - High temperature operation 11
Electric Drives Future solutions SiC / GaN SiC / GaN power module (~2020) Improved material enables smaller chip for same current rating compared to Si SiC Mosfet 600-1200 V (switch transient in VCC applications <750 V) GaN Fet 70-600 V SiC thermal conductivity ~3 x better than Si Mosfet Ron @ 1 kv Si 10000 mω mm2 (3600) SiC 35 mω mm2 (13) GaN 2.8 mω mm2 (1) much smaller conductive losses for same chip size OR same conductive losses but for much smaller chip size Advantages - Smaller chip size compactness lower switching losses enabler for higher switch frequencies (16-20 khz) & reduced switching noise & lower DC link capacitance Trade off versus - Reduced conductive losses and improved vehicle duty cycle efficiency - Thermal capability Challenges - Cost (SiC module today ~ same cost as complete inverter) - Chip size, current capability & manufacturing (material imperfections, difficult to process) - Tier 1 ability / willingness to shift to new power module technology 12
Electric Drives Future solutions MBPM EM with reduced REE content Idea: MBPM Multi Barrier Permanent Magnet Machine Similar to conv. PMSM but higher utilisation of reluctance Volvo Cars in-house study of different rotor designs Maxwell used as software tool Target is to reduce magnet content with ~20% and keep acceptable performance density Other machine concepts such as IM, SyRM, SRM and EMSM benchmarked and studied conclusion is that torque and power density is too inferior to meet VCC installation requirements Advantages - Less Nd, Dy and thus lower component cost and sensitivity to market price - Close co-operation with supplier to ensure feasiblity - C/o Inverter and stator solution with conv. PMSM (tbd) - Could be used for both efad (larger space available) and erad applications - Could be an enabler for sensorless drive (if Ld/Lq distinction kept at saturation) Challenges - Performance with same active dimensions as conv. PMSM design - Harmonics 13