POLITECNICO DI TORINOMaster of Science in Automotive Engineering

Trade-off analysis of hybrid electric powertrains

Academic Tutors:Prof. Nicola Amati Students:Prof. Andrea Tonoli Stefano Di DonatoIng. Luca Castellazzi Chowdhury Foyz Ahamed Polas

Hybrid electric vehicles

• High pollutant emissions

• Global warming

• Increase of fossil fuel price

Introduction

2/25

Tighter regulations on vehicle emissions

Architectures

Hybrid Electric Vehicles (HEV)

Series

Power split (Series-Parallel)

Parallel

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Hybrid Electric Vehicles (HEV)

Hybridization Ratio

FrontDifferentia

l

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Modelled architectures• Through The Road (TTR)

Gearbox Cl

utc

h

Fuel

Internal Combustion Engine

Electric Machine/Inverter

48V Battery

Front Wheels

RearDifferentia

l

Rear Wheels

Differential

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Modelled architectures• Belt-driven Starter Generator (BSG)

Gearbox Cl

utc

h

Fuel

Internal Combustion Engine

Electric Machine/Inverter

48V Battery

Front Wheels

Belt Coupling

• Modelling and analysis of hybrid powertrains

• Energetic analysis, battery sizing

• Accessories energy consumption

• Comparison between different architectures

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Objectives

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Vehicle DataModelled vehicle: Fiat Panda

Internal combustion engine: 1.0 TwinAir (Naturally Aspirated)• Max Power: 65CV @6250 RPM• Max Torque: 88Nm @3500 RPM

Vehicle mass: 975 Kg

Wheelbase: 2.3 m

Powertrain components (Pure ICE Vehicle)

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Vehicle Model

Driving Cycle

Driver

Internal Combustion Engine

Clut

ch Gearbo

xDifferenti

al Wheels

Drivetrain

Ref. Speed

Actual Speed

Throttle Torque

Longitudinal Wheel Force (Fx)

Brakes

Fuel Consumption

Vehicle Dynamics

Fuel Consumption Evaluation

10/25

Vehicle Model

𝑝𝑚𝑒=𝑇 𝑛𝑐

10𝑉 𝑑2𝜋

- : mean effective pressure- : Instantaneous torque- : Number of revolutions per power

stroke (for a 4-stroke engine = 2),- : the displacement volume

g/CVh

g/CVh kg/J kg/s l/100km

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Validation of the model

Modelled vehicle Real vehicle

0-100 km/h acceleration test 15.28 s 15.7 s

Fuel Consumption comparison (NEDC) 4.4 l/100km 4.2 l/100km

BSG ImplementationVehicle Model

Internal Combustion Engine Belt

Coupling

- Belt Drive System Block (BDS)Pulleys• Alternator/EM • A/C compressor• Automatic Tensioner• Crankshaft• Idle

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48V Battery Electric Machine/Inverter

Modelled phenomena• Predict levels of slip in different pulley-

belt contact regions• Calculate the belt tensions for different

spans• Calculate power losses of the system 

- Electric motor

Battery ModelVehicle Model

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𝐸=𝐸0−𝐾 ( 𝑄𝑛𝑜𝑚

𝑄𝑛𝑜𝑚−𝑄 )+ 𝐴𝑒−𝐵𝑄

𝑆𝑂𝐶 [%]=100 (1− 𝑄𝑄𝑛𝑜𝑚 )

- = no-load voltage [V]- = battery nominal voltage [V]- = polarization voltage [V] - is the actual battery charge [Ah],- is the nominal battery capacity [Ah], - is the exponential zone amplitude [V],- is the exponential zone time constant inverse [Ah-1]

TTR Implementation

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Vehicle Model

Electric Machine/Inverter

48V Battery

RearDifferentia

l

• The BDS system is removed from the front driveline.

• A seperate 3 phase Brushless AC Motor powers the rear axle.

• The motor can generate maximum torque of 88 Nm and peak power 30 kW.

• Current absorption characteristics of the Electric Motor.

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Vehicle Model (TTR)

16

• Modelled as a one-dimensional linear model

• = Dissipated Power

• = Thermal resistance

• = Thermal time constant

Thermal Model

𝑡

𝑇 𝐸𝑀𝑃 𝐷𝑅 h𝑡

𝜏 h𝑡

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Control Strategy• Control parameters

• Battrey SOC%,

• Current,

• Temperature.

• Controlled parameters• Torque provided by the ICE,

• Torque provided by the EM.

• Control Objectives

• Obtain battery energy balance,

• Regeneration of maximum brake energy,

• Safety,

• Fuel consumption reduction.

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Control StrategyCurrent control SOC control Temperature control

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Validation of the Control strategy• NEDC cycle

• Battery capacity 35Ah

• Maximum current 175 A

• Initial SOC = 70%

• = 30 km/h

• Simulations varying Vswitch : ∆SOC evaluation

• Fuel consumption evaluation for each capacity

(Energetic equilibrium -> ∆SOC = 0)

• Battery sizing

• Comparison between BSG and TTR configurations

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Battery Sizing

• A part of battery energy is required by the electrified accessories,

• For example an electrified A/C compressor require a power of 1500W,

• The energy from the regenerative braking is not sufficient,

• A BSG or a conventional alternator will provide the necessary power.

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Electrified AccessoriesCapacity 17.5Ah @10C

BSG Model TTR Model

Available Current 12.19 A 23.5 A

Available Power 585 W 1130 W

Capacity 17.5Ah @10C

Belted A/C Compressor

Electric A/C Compressor

Fuel Consumption

5.265 l/100km

5.072 l/100km

• All the simulations are repeated for the TTR architecture,

• The TTR configuration consumes 12.5% less than the BSG.

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Electrified AccessoriesCapacity 17.5Ah @10C

BSG Model TTR Model

Applied torque (BSG or Alternator)

3.05 Nm 1.1 Nm

Available Power 1500 W 1500 W

Fuel consumption

5.072 l/100km

4.44 l/100km

Vehicle configuration BSG Model TTR Model ImprovementPure ICE 4.173 4.173

Hybrid (Battery 17.5 Ah @10C) 3.833 3.260 14.95%

Hybrid (Battery 17.5 Ah @10C)With electric A/C compressor (1500W)

5.072 4.440 12.45%

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Review of the results

• The TTR architecture is more efficient for electric traction and regenerative braking.

• The BSG architecture is useful to generate power for the accessories and as starter motor

• The optimal configuration can be a combination of the two architectures

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Conclusions

FrontDifferentia

l

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Conclusions• Optimal architecture

Gearbox Cl

utc

h

Internal Combustion Engine

Electric Machine/Inverter

48V Battery

Front Wheels

RearDifferentia

l

Rear WheelsBSG Machine/Inverter

Electrified Accessorie

s

Thank You for

Your Attention