Hybrid Drive Systems for Vehicles

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Janel Allen
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1 Hybrid Drive Systems for Vehicles L4 Alternative drive train Components Mats Alaküla EHS

2 Drawback with conventional drivetrains Limited ability to optimize operating point No ability to regenerate braking power

3 Solutions Smaller Engine + Reach higher operating points - Still cannot regenerate Store energy in the vehicle mass - Speed variations - Still cannot regenerate Secondary energy storage + Selectable operating point (Pstorage = Pice Proad) + Can regererate - Expensive

4 Smaller Engine cylinder deactivation IC E Clutch Batt IC E PE Clutch EM 100 GEAR DIFF

5 Combustion On Demand Cylinder deactivation via free valve control Mats Alaküla EHS

6 Optimized efficiency Number of Cylinders in use Torque [Nm] 0 0 Speed [rad/s] Torque [Nm] 0 0 Speed [rad/s] Torque [Nm] Speed [rad/s]

7 Max efficiency 0.35 Blue=2-cylinder std, Red=2-cylinder COD Optimal Efficiency ICE Power [W] x10 4

8 Secondary Energy Storage selection Why electric? Efficient secondary energy converters (Electrical machines) Safe, quiet, flexible installation Increasing need for Auxilliary electric power High torque density of Electrical Mchines Up to 30 Nm/kg ICE: <2 Nm/kg

9 Secondary energy storage Hybridisation IC E EM PE Batt PE EM IC E Clutch EM GEAR DIFF Batt PE DIFF Series Parallell

10 Energy Storage Systems Lund University, Sweden

11 How does a battery look? Mats Alaküla EHS

12 Design criteria Cost Vehicle Performance Operation Mats Alaküla EHS

13 Driving the Hybrid by the Atoms Source: Uppsala University Mats Alaküla EHS

14 Technologies NiMH Lead Li-ion S.C. Mats Alaküla EHS

15 Limiting Factors Durability NiMH Cost NiMH Weight Li-ion Cost Safety Charge Power Durability Lead Weight Maintenance S.C. Energy S.C. Initial Cost

16 Performance S.C Li-ion NiMH Pb- Acid Mats Alaküla EHS Energy Density Power Density Effpower

17 Relation to needs Power 100 kw 10 kw Propulsion Hybrid Hybrid Mode Mode Cranking Propulsion Electric Mode Mode Next Next Generation Need Need Energy

18 Battery Cell Properties All parameters are non-linear Strong dependance on SOC, temperature, current rate & direction, and history. No No Steady-State Operation!

19 Super Capacitor Cell Properties Fewer non-linear elements Strong dependance on SOC & temperature only Semi Steady-State Operation!

20 Combined Energy Storage System Battery Combined System SuperCaps Mats Alaküla EHS Energy Density Power Density

21 Driving Criteria Power output/regeneration at a specific time Charge and Discharge Properties Cooling Issues Pure Electric Range Upcoming energy need (GPS, weather and traffic info, etc.) Factors Determined by: State of Function = State of Charge + State

22 State of Charge Li-ion Mats Alaküla EHS Voltage NiMH S.C. 100% State of Charge 0%

23 State of Health Temperature and Temperature Changes Charge and Discharge Properties Pure Electric Range State of Charge individual cells in a battery system -- ALL need to be managed Management unit is needed

24 SAFT data Mats Alaküla EHS Mats Alaküla

25 SAFT Lithium teknologi Mats Alaküla EHS Mats Alaküla

26 Battery simulation model : 1 P term ( e batt R batt i batt ) i batt e batt i batt R batt i 2 batt i batt P P loss ch arg e batt ebatt 2 R R P batt term ch arg e P P term i batt 2 batt P loss e 2 R batt batt 2 e batt P R term batt P loss R batt Pch arg e i batt Pterm

27 Battery Simulation model : 2 2 Battery charge efficiency Efficiency Battery power [W] x10 5

28 Super Capacitors : 1 Low voltage -> series connection 1 W C u 2 C 2 C C system # units 1 C 1 unit

29 Supe Capacitors : 2 Size 22 liter / 15 kg Capacitance 145 Farads Max electric 50 V / 600 A specs Power density 2900 W/kg Energy density 2.3 Wh/kg

30 Fly wheel energy storage High speed rotating mass 1 W mech J 2 Mats Alaküla EHS 2 wheel

31 Electric Motor Drive Systems Lund University, Sweden

32 Torque and Power Torque = Force * radius on the shaft T = F * r Power = Torque*Speed on the shaft P = T * but, also Power = Voltage * Current on the electrical terminals P = U * I F r

33 Stator, Rotor and Airgap The stator is static (not moving) The rotor rotates The air gap seperates them Usually < 1 mm

34 Hybrid Topologies Diesel Engine El Ma ch El. mac h El. mach Mats Alaküla EHS

35 Inner or Outer Rotor, Radial or Axial flux Inner rotor Radial flux Stator Rotor Stator Stator Stator End winding Outer rotor Radial flux Rotor Axial flux Stator Stator Rotor

36 Distributed or Concentrated winding Axially shorter end winding Cheaper assembly Lowertorquequality Longer end winding More expensive assembly Higher torque quality

37 Shear Force & Torque Current and Flux interact for tangential force = Force/Unit area is a key figure A good design accomplish about = [N/m 2 ] in continuous operation and 2..4 times more in transient operation

Form Factor Low torque density but high acceleration For the same torque, a machine can be

1000 Nm, AND that the stator outer radius is 0.15 0.5 meter.

The long and slender machine will accelerate faster Torque ~ radius 2 *length Inertia ~

38 Form Factor Low torque density but high acceleration For the same torque, a machine can be either short and wide, or long and slender Assume [N/m 2 ], and a desired torque of 1000 Nm, AND that the stator outer radius is meter. How long will the machine be to fulfill the torque requirement? The long and slender machine will accelerate faster Torque ~ radius 2 *length Inertia ~ radius 4 *length Acceleration = Torque/Inertia ~ 1/radius Length Radius High torque density but low acceleration

39 Eaton ISAM Short and Wide Concentrated winding PM motor from Hitachi

40 Voith ExSAM Long and slender Induction motor from?? Probably very close to standard industrial good commonality 150 kw 520 motor or input shaft? Siemens 1FHX

41 Volvo/Renault/Mack/Nissan ISAM Short and Wide Mats Alaküla EHS

42 Mats Alaküla EHS Some Cars Toyota Complex Honda Parallell with CVT ISAM PM Motor Concentrated windings Complex PM Machines Distributed windings N/m 2!!!

Voltage * current Voltage = Force *speed / current = = Flux

43 Generic Force Force Force Power Current Flux density = Flux density * Current * length (twice) = Force * Speed = Voltage * current Voltage = Force *speed / current = = Flux density * length * speed Lorentz force = current in magnetic field

44 Linear movement from generic force Mats Alaküla EHS

45 Rotating movement from generic force Mats Alaküla EHS

46 Conclusions on force and movement The same generic circuit accomplish both linear and rotating movement. One phase is not enough for continuos force Qualitative: Voltage ~ Speed Current ~ Force

47 Field Weakening : I Remember: Voltage ~ flux density * speed Torque ~ flux density * current Power ~ speed*torque = voltage*current The required voltage hits the roof at some speed. What to do, to increase speed beyond? Answer: Reduce flux density Consequences: The voltage requirement is kept constant, as desired The torque capability drops as the flux density. The power is kept constant, since the speed increases in the same rate as the torque drops with increasing speed.

48 Field Weakening : II [Nm] 250 [kw, V] Mats Alaküla EHS Base speed [rpm] Const torque Constant power Field weakening ratio 1:4 Max torque Max voltage and power Max speed

49 Example from Toshiba Large Torque and High Efficiency Permanent Magnet Reluctance Motor for A Hybrid Truck - Masanori Arata et. Al, EVS-22

Permanent Magnet Synchronous Machines Same as the generic machine Voltage and frequency proportional to speed Current proportional to torque High torque density 1.

50 Permanent Magnet Synchronous Machines Same as the generic machine Voltage and frequency proportional to speed Current proportional to torque High torque density Nm/kg Compare to ICE Nm/kg High efficiency Up to 97% Higher efficiency, higher torque density and more expensive than other machines Due to the permanent magnets.

51 The Induction Machine : I Same stator as the PMSM The rotor is a short circuited cage The rotor current must be induced magnetically Losses related to magnetization competes with losses due to torque generation. Robust construction Low cost Low/no maintenance Heavily standardized for industrial applications

52 The Induction Machine : II Voltage and frequency proportional to speed, like PMSM

53 Comparison Electric Drives T max [Nm/kg] PM AC (IM) P continuous [kw/kg]

54 Electrical machine losses Several types: Copper losses (Ri 2 ) Iron losses (k 1 *f*b 2 + k 2 *(f*b) 2 ) Windage losses (surface speed) Other friction losses Hysteresis losses Approximately calculated by Eddy current losses [EtaEM,Tem,Wem] = CreateEMmap(Pem_max,wem_max,Tem_max) Electrical machine efficiency Torque [Nm] Speed [rad/s] Mats Alaküla EHS

55 The Traction motor efficiency Torque limit Electrical machine efficiency Power limit Torque [Nm] Speed [rad/s] Speed limit

56 Power Electronics Needed to condition the battery voltage to the different electrical drives Use switching technology for high efficiency Conventional converters (like loudspeaker amplifiers) efficiency % due to continuous control of the voltage. Switching means on/off control of voltage, leading to efficiency above 95 %.

57 1 Phase Pulse Width Modulation (PWM) Mats Alaküla EHS sa va Modulating wave Voltage reference Output voltage

58 Three-phase Converters +Ud/2 -Ud/2 0 id sa + ua - va sb vb sc vc + uab - + ubc - - uca + + ub - vo Traction motor + uc -

59 Three-phase Pulse Width Modulation The voltages contain high harmonics that cause: Audible noise Torque ripple EMC problems ua r ef & tri va vo v0 0 varef va tri ua u=va-v0 grundton 50 Hz

60 Power Electronics Efficiency + V DC Several types of losses Switching losses Conduction losses i S I 0 v S I 0 v S, i S V DC v on p S P cond t on t cond t off t t T sw

61 Power Electronic Efficiency Mostly depending on the ratio Output voltage DC link voltage Almost constant over wide operating range Can be represented by a constant, e.g. 0.97

Hybrid Drive Systems for Vehicles. Drawback with conventional drivetrains

Hybrid Drive Systems for Vehicles L4 Alternative drive train Components Drawback with conventional drivetrains Limited ability to optimize operating point No ability to regenerate braking power 1 Solutions