Energy Management of a Series Hybrid Electric Powertrain System

(EMoSHEPS)By: Saifuddin Abdul Halim (Mech Eng MEng)Project Supervisor: Dr Saber Fallah

Introduction Why Hybrid?• Due to the increasing vehicle emissions, researchers and vehicle

manufacturers resorted to develop electric vehicle as an alternative.• Disadvantages of EV results in the introduction of hybrid vehicle.

Why series HEV?• Equivalent Consumption Minimization Strategy (ECMS) was originally

introduced by Paganelli et al., in 2002 for parallel configuration.• Series HEV has a huge potential due to the downsizing of the engine

as well as other factors such as the removal of gearbox, simplifying the configuration and reducing vehicle mass.

• Beneficial for urban-driving cycle.

What is ECMS?• The basis of ECMS is that discharging of power from the battery at

any instant will results in equivalent fuel being consumed by the ICE to recharge the battery in the future and vice versa.

• ECMS reduces the overall fuel consumption by minimizing the total equivalent fuel consumption.

• The total fuel consumption is the sum of fuel consumed by the ICE to drive the motor via generator and the fuel consumed to recharge the battery.

Disadvantages• Tendency of significant power source variation that leads to dramatic

wheel-torque oscillation.• Possibility of delayed and hesitation of torque response / poor throttle

response.• In series HEV, these problems can be reduced due to having only one

type of energy, electrical energy, supplied to the EM and since the ICE is decoupled from the driving the wheels.

Objectives Modelling a conventional and a series hybrid powertrain. Identifying and applying basic operating conditions. To simulate the Equivalent Consumption Minimization Strategy (ECMS)

control strategy. Carrying out forward simulations for both models under two different

driving conditions. Comparing fuel economy as well as the velocity performance of both

vehicles. Optimizing the ECMS parameters to achieve a minimum of 15% reduction

in fuel consumption.

Modelling Model of Series HEV

Model of Conventional vehicle

ECMS controller & power distribution

Driverdetermines current

angular speed

Accelerate

Decelerate

Increase in Angular Speed

Decrease in Angular Speed

Determine corresponding torque demand at EM via

characteristic curves;+ve for driving or -ve for RBS

Calculation of Power demand, P(dem); +ve for driving or

-ve for RBS

Negative Power(RBS)

Positive Power(Driving)SoC

P(ICE,opt)=P(maxICE)P(Battery,opt)=0

P(ICE,rchg)=0

P(ICE,opt)=P(dem)P(Battery,opt)=0

P(ICE,rchg)=P(maxICE)-P(dem)P(demand,EM)=P(ICE)+P(Battery) P(demand,EM) = P(Battery)

P(ICE,opt)=0P(Battery,opt)=0

P(ICE,rchg)=0P(EM,rchg)=P(dem)

SoC ≥ SoC (max)SoC ≤ SoC (min) SoC (min) < SoC < SoC (max)

P(dem)>P(maxICE) P(dem)<P(maxICE)

Fuel consumption

Determination of Fuel Consumption using ICE fuel

flow map

Calculation of torque

supplied to drivetrain

Drivetrain Transmission system

Vehicle velocity

Wheels

Simulation Driving conditions

Change in equivalency factor

The performance evaluated• Overall fuel consumption at the end of the drive.• Velocity trend of the vehicle.

Equivalency Factor, 1.125 (-10%)

1.2501.375 (+10%)

Results Cruising mode

  Series HEV ConventionalFuel consumption 0.989 1.199

Max Velocity 92.5 79.0Improvement in fuel

consumption (%) 17.5 N/A

Random driving mode

  Series HEV ConventionalFuel consumption 0.699 0.975

Max Velocity 113.5 159.7Improvement in fuel

consumption (%) 28.3 N/A

Change in equivalency factor, Sdis

Equivalency Factor, Total Fuel Consumption (L)Cruising mode Random Driving mode

1.125 (-10%) 0.985 0.6851.250 0.989 0.699

1.375 (+10%) 0.991 0.711N/A 1.199 0.975

Conclusion The implementation of ECMS in series HEV managed to reduce fuel

consumption up to 17.5% than the conventional vehicle under cruising mode and up to 28.3% under cruising mode.

Although fuel consumption is reduced, but the downsizing of engine in series HEV means that the benefit is achieved at the expense of vehicle velocity.

ECMS controller also able to adapt to change in its own parameter. In addition, the benefits of the ECMS are also transferable between

configurations and also driving conditions.