MODELING AND SIMULATION OF SERIES PARALLEL HEV USING ... · Vehicle dynamics and motion (a) and Simscape block for vehicle body (b) In order to model vehicle dynamics and motion,

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November 2018, pp. 1590–1599, Article ID: IJMET_09_11_164

Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=11

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

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MODELING AND SIMULATION OF SERIES

PARALLEL HEV USING MATLAB/SIMULINK

Nguyen Khac Tuan

Automotive and Power Machinery Faculty, Thai Nguyen University of Technology Thai

Nguyen city, Vietnam

ABSTRACT

This paper introduced a method for modeling a series parallel hybrid vehicle using

Matlab/Simulink software. The components of the vehicle including internal combustion

engine, electric motor, generator machine, and vehicle body model and also control logic

is modeled. Some simulation results for the Toyota Prius when operating in several

driving cycles are presented. The results are discussed in respect to working status, power

combination between driving machine and engine and also generative braking power of

the vehicle due to driving conditions.

Keywords: hybrid vehicle, electric motor, generator, engine, modeling, power.

Cite this Article: Nguyen Khac Tuan, Modeling and Simulation of Series Parallel Hev

Using Matlab/Simulink, International Journal of Mechanical Engineering and

Technology, 9(11), 2018, pp. 1590–1599.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=11

1. INTRODUCTION

At present, hybrid electric vehicles (HEVs) are recognized as one of the most promising

technologies in significantly reducing the petroleum fuel consumption, toxic and greenhouse

gases emissions [1-10]. Hybrid drivetrains are usually categorized into series and parallel

configurations. The major advantage of the series hybrid drivetrain or electrically coupling hybrid

drivetrain is that the engine is mechanically decoupled from the vehicle wheels, and thus, can

operate in a narrow, high efficient speed and torque region. Its major disadvantage is that the

mechanical power of the engine needs to change its form twice mechanical to electrical and then

to mechanical again in delivering to the driven wheels, and thus more energy losses may occur.

On the other hand, in parallel hybrid vehicles or mechanically coupling hybrid drive train, the

engine directly delivers its mechanical power to the driven wheels without undergoing energy

form change. The advantages of parallel hybrid drivetrain are that the speeds and torques of the

two power plants can be chosen independently within constraints, the power plants can be

smaller, and therefore cheaper and more efficient. The major dis advantage is that the engine

cannot always operate in a narrow speed region, because of its mechanical coupling to the driven

wheels. Thus, the average engine efficiency is lower than that in series hybrid drivetrain. To

overcome the disadvantages of the series and parallel hybrid drivetrain, a new hybrid drivetrain,

called series-parallel hybrid drivetrain, has been developed [8].

Nguyen Khac Tuan


The structure of series-parallel hybrid drivetrain is shown as in Fig.1. Part of engine energy

drives the vehicle directly, and other part converts into electric energy, propelling the vehicle by

electric motors. The engine energy can be totally devoting to driving the vehicle or totally

converted into electric energy if necessary. The electric motor could be applied to propel the

vehicle solely or together with the engine and it also can be used as a generator to charge the

battery by regenerative braking. Comparing with the series and parallel hybrid drive systems, the

working modes of a series-parallel hybrid system are more flexible to enable the optimal

utilization of the different properties of different components.

Figure 1 Series-parallel hybrid HEV

The structure and control of a series-parallel hybrid drive system takes full advantages of the

features of a series and parallel drive system. It can be optimizing the operation of engines. The

structure ensures the possibility that the system works optimally under complex driving

conditions, thereby achieving the target of lower emission and fuel consumption. This system

relies less on energy storage than the series hybrid system does, and operation range of the engine

is less affected by driving cycles than parallel hybrid drive system. This paper introduced a

method for modeling a series parallel hybrid vehicle using MATLAB/Simulink software.

1.1. Series Parallel HEV model

In order to build the model of a complex system using Matlab/Simulink software [2], it is usually

divided the system into subsystems. For the series parallel hybrid vehicle model shown in figure

1, we divided into the following subsystems: vehicle body, engine, mechanical coupling devices,

motor, generator and control logic model.

1.1.1. Vehicle body model

The vehicle motion is a result of the net effect of all the forces and torques acting on it. The

longitudinal tire forces push the vehicle forward or backward. The weight mg of the vehicle acts

through its center of gravity (CG). Depending on the incline angle, the weight pulls the vehicle

to the ground and pulls it either backward or forward. Whether the vehicle travels forward or

backward, aerodynamic drag slows it down. For simplicity, the drag is assumed to act through

the CG.

The system of differential equations describing the vehicle dynamics is written as follows

Modeling and Simulation of Series Parallel Hev Using Matlab/Simulink


( ) ( )

( )( )

( )( )

2

.sin

( )

1sgn

2

.sin . .cos

.sin . .cos

x x d

x xf xr

d d x x

d x

zf

d x

zr

mV F F mg

F n F F

F C A V V V V

h F mg mV b mgF

n a b

h F mg mV a mgF

n a b

ω ω

β

ρ

β β

β β

= − −

= +

= + +

− + + +=

+

+ + +=

+

&

&

&

(1)

Where:

g : gravitational acceleration; β : incline angle; m: mass of the vehicle; H: height of vehicle

center of gravity (CG) above the ground; a, b: distance of front and rear axles, respectively, from

the normal projection point of vehicle CG onto the common axle plane; Vx: velocity of the vehicle;

Vw: wind speed; N: number of wheels on each axle; Fxf, Fxr: longitudinal forces on each wheel at

the front and rear ground contact points, respectively; Fzf, Fzr: normal load forces on each wheel

at the front and rear ground contact points, respectively; A: effective frontal vehicle cross-

sectional area; Cd : aerodynamic drag coefficient; ρ: mass density of air; Fd : aerodynamic drag

force.

a) b)

Figure 2. Vehicle dynamics and motion (a) and Simscape block for vehicle body (b)

In order to model vehicle dynamics and motion, a Simulink model was built (figure 2b), in

which there are six ports, two input ports: W -Headwind speed, beta - Road incline angle; three

output ports: V - longitudinal velocity, NF - Front axle normal force, NR - Rear axle normal force

and a conserving port H associated with the horizontal motion of the vehicle body. Connect tire

traction motion to H port.

1.1.2. Mechanical coupling device model

In case of parallel hybrid and series-parallel hybrid drivetrains, the ICE and an electric motor

(EM) supply the required traction power. The power from ICE and EM are added together by a

mechanical coupling device. Generally, the mechanical coupling is of two types: torque coupling

and speed coupling [4]

Torque coupling. In this case the coupler adds the torques of the ICE and EM together and

delivers the total torque to the driven wheels. The ICE and EM torque can be independently

controlled. The speeds of the ICE, EM and the vehicle are linked together with a fixed relationship

and cannot be independently controlled because of the power conservation constraint. The torque

coupling is a two-degree-of-freedom mechanical device. Port 1 is a unidirectional input and Port

2 and 3 are bi-directional input or output, but both are not input at the same time (figure 3.a).

Here input means the energy flows into the device and output means the energy flows out of the

device. In case of HEV, port 1 is connected to the shaft of an ICE directly or through a mechanical

Nguyen Khac Tuan


transmission, port 2 is connected to the shaft of an electric motor directly or through a mechanical

transmission, port 3 is connected to the driven wheels through a mechanical linkage.

(a) (b)

Figure 3. Torque (a) and speed (b) coupling devices

For a losses torque coupler in steady state, the power input is always equal to the power output

from it. The power balance is:

3 3 1 1 2 2T T Tω ω ω= + (2)

Where T1 - propelling torque produced by ICE; T2 - propelling torque produced by electric

motor; ω1 - speed of ICE; ω2 -speed of motor; ω1 - speed of wheel.

The torque coupler can be expressed as

3 1 1 2 2T k T k T= + (3)

Where 1 2

1 2

3 3

;k kω ω

ω ω= = are the structural parameters of the torque coupler

Speed coupling. In this case the speeds of the ICE and EM can be added together and all

torques are linked together and cannot be independently controlled. The power produced by two

power plants may be coupled together by adding their speed. This is done with the help of speed

coupling devices (Figure 3b). The speed coupler is a three port two-degree-of-freedom device.

Port 1 is a unidirectional input and port 2 and 3 are bi-directional input or output, but both are not

input at the same time. Here input means the energy flows into the device and output means the

energy flows out of the device. In case of HEV, port 1 is connected to the shaft of an ICE directly

or through a mechanical transmission, port 2 is connected to the shaft of an electric motor directly

or through a mechanical transmission, port 3 is connected to the driven wheels through a

mechanical linkage.

For a losses speed coupler in steady state, the power input is always equal to the power output

from it. For the speed coupler shown in figure 3b, the speed and torque relations are:

3 1 1 2 2k kω ω ω= + (4)

1 2

3

1 2

T TT

k k= = (5)

Where k1, k2 are the structural parameters of the speed coupling device

Figure 4 - Simulink model for planetary gear set speed coupling device



A typical speed coupler is the planetary gear set. In Figure 4, a Simulink model for planetary

gear set speed coupling device is shown.

A. Engine model

In this paper the Generic Engine model [2] was used to model internal combustion engine (figure

5). By default, the Generic Engine model uses a programmed relationship between torque and

speed, modulated by the throttle signal.

The engine model is specified by an engine power demand function g(Ω). The function

provides the maximum power available for a given engine speed Ω. The block parameters

(maximum power, speed at maximum power, and maximum speed) normalize this function to

physical maximum torque and speed values. The normalized throttle input signal T specifies the

actual engine power. The power is delivered as a fraction of the maximum power possible in a

steady state at a fixed engine speed. It modulates the actual power delivered, P, from the engine:

P(Ω,T)= T·g(Ω). The engine torque is τ = P/Ω.

B. Electric machines

Figure 5. Simulink model for engine

In the series - parallel hybrid vehicle, the powertrain comprises the internal combustion

engine as the primary power source and two electric machines. The first one (Generator) is

typically operated in the generator mode thus being able to keep the engine in the desired optimal

operating point), while the second (Motor) operates as a traction motor (during normal driving),

or a generator (during regenerative braking intervals) [1, 8, 10]. The electrical power can also be

supplied from the battery (e.g. when the driver demand is increased), or it can be stored within

the battery during regenerative braking or low-power demand intervals.

Figure 6. Synchronous Generator model

Nguyen Khac Tuan


There are several types of electric motors and generator can be used in hybrid vehicle such as

DC, synchronous with permanent magnets or electromagnetic [1,8]… In figure 6 the model of a

synchronous generator is depicted. The generator can turn backwards - this happens when

accelerating from rest. The generator also acts as a starter for the engine. If the engine is running,

then the generator controller is used to manage battery charging using torque-control mode,

otherwise the generator controller controls generator speed.

C. Control logic model

a) b)

Figure 7. Battery charge controller (a) and control logic (b) models.

Driving mode. For the series - parallel HEV shown in fig 1, there are six driving modes as

follow: During startup and driving at light load, the battery solely feeds the electric motor to

propel the vehicle while the ICE is in the off mode; For both full-throttle acceleration and normal

driving, both the ICE and electric motor work together to propel the vehicle. The key difference

is that the electrical energy used for full-throttle acceleration comes from both the generator and

battery whereas that for normal driving is solely from the generator driven by the ICE. Notice

that a planetary gear is usually employed to split up the ICE output, hence to propel the vehicle

and to drive the generator. During braking or deceleration, the electric motor acts as a generator

to charge the battery via the power converter. Also, for battery charging during driving, the ICE

not only drives the vehicle but also the generator to charge the battery. When the vehicle is at a

standstill, the ICE can maintain driving the generator to charge the battery.

Control logic is developed to realize good driving performance and good battery energy

management and good fuel economy in these driving modes. The battery charge controller and

control logic models are seen in fig.7

By combining the above models, the full model of series parallel hybrid electrical vehicle has

been built in Matlab- Simulink R18 can be seen in Figure 8[3].



Figure 8. Simulink model used to simulate series-parallel HEV

2. RESULT AND DISCUSSION

Nowadays, Toyota Prius is a typical series–parallel hybrid electric vehicle [8,9]. Thus, in this

section, the authors use the Simulink model built in section 2 to simulate the operation of this

vehicle. Model has been run on ECE 15 and EUDC driving cycles. The results can be seen in

Figure 9 and Figure 10.

The simulation results for the Toyota Prius running on the UEDC [4,5] cycle shown that:

period 1-2 the vehicle stand still; period 2-3, vehicle start from rest and vehicle speed less than

25km/h, vehicle is driven only by motor torque, battery supplies power to motor to drive vehicle,

so motor power is equal to battery power and the SOC of battery drops during this period; period

3-4, the vehicle continue accelerate from 25km/h to 70 km/h, Vehicle is driven by both motor

and part of ICE, both battery and generator supply motor, so motor power is equal to the sum of

motor torque and battery power; during period 4-5, the vehicle moves steady at speed of 70 km/h,

HEV driven by engine, part of engine power is transferred to generator to charge the battery, the

motor do not provide power for vehicle; during period 5-6, vehicle decelerate to 50 km/h, motor

operates as a generator in order to decrease speed rapidly, which generates electricity to charge

battery, so the SOC of battery rises during this period; during period 6-7, vehicle moves steady

at speed of 50 km/h, again HEV driven by engine, part of engine power is transferred to generator

to charge the battery, the motor do not provide power for vehicle; during period 7-8, vehicle speed

up from 50km/h to 70km/h, vehicle is driven by both motor and part of ICE both battery and

generator supply motor, the SOC of battery drops; during period 8-9, the vehicle moves steady

at speed of 70 km/h, HEV driven by engine, part of engine power is transferred to generator to

charge the battery, the motor do not provide power for vehicle; during period 9-10, vehicle

accelerate to 90 km/h, both engine and motor propel the vehicle, battery supplies power to motor,

the SOC of battery drops; during period 10-11, the vehicle moves steady at speed of 90 km/h,

HEV driven by engine, part of engine power is transferred to generator to charge the battery, the

motor do not provide power for vehicle; during period 11-12, the vehicle decelerate from 90 km/h

to 25 km/h, motor operates as a generator in order to decrease speed rapidly, which generates

electricity to charge battery, so the SOC of battery rises during this period; during period 12-13,

vehicle continue decelerating from 25 km/h to 0 km/h, vehicle only driven by motor, engine in

off status; period 13-14, end of cycle, both engine and motor in off status.

Nguyen Khac Tuan


Figure 9. Simulation results for Extra Urban driving cycle: On/off Status of ICE and motor and Power

of ICE, motor and Generator and battery SOC (b)

Thus, it can be seen in the UEDC cycle in figure 9 that, series- parallel HEV operate in the

following modes: (I). Electric motor mode solely: periods 1-2 and 13-14; (II). Hybrid mode:

including modes 3-4, 7-8 and 9-10; (III). Engine only mode: periods 4-5, 6-7, 8-9 and 10-11. In

these stages the engine power maintains the velocity the stability of the car and part of engine

power used to charge the battery; (IV) Regenerative braking modes include deceleration cycles

5-6 and 11-12.

Carry out the same simulation for the case of HEV running in the ECE driving cycle, the

results also shows that, at speeds of less than 25 km/h, HEV operate in electric motor mode and

when the vehicle speed bigger than 25 km/h HEV in hybrid mode. Beside these modes, the car

also operates in regenerative brake mode during this driving cycle (figure 9).

Performance simulation of the vehicle with several different driving cycle also allows us to

determine the working modes of ICE, Motor, Generator, the combining power between the power

sources as well as the regenerative power obtained in the cycle. The total power value of ICE,

Motor, the regenerative braking power in several driving cycles is shown in Table 1.



(a) (b)

Figure 10. Simulation results for ECE driving cycle: On/off Status of ICE, motor and Generator (a) and

Power of ICE, motor and Generator and battery SOC(b).

Table 1 Total power of ICE, Motor and Generative braking power in several driving cycles

Driving Cycle

Propulsion

Power demand

(W) * 105

Propulsion

power of ICE

(W) * 105

Propulsion

power of Motor

(W)*105

Generative

power

(W)*105

ECE 15 7.162 3.936 3.2253 1.2920

UEDC 23.385 15.750 7.6356 6.0264

UECD for lower

power vehicle 17.376 11.948 5.4279 3.6390

3. CONCLUSION

This paper introduced a method for modeling a series parallel hybrid vehicle using

Matlab/Simulink software. The model includes detailed models of electric motors, internal

combustion engines, and vehicle body and control logic. The controller is designed base on the

power demand from the pedal position in order to choose how to combine this power between

the two power sources to obtain better fuel economy.

The simulation model allows to quickly change architecture, parameters, power management

strategy as well as the driving cycles to view output data graphically. Thus, this model can be

used for optimal study of structural parameters and control of series-parallel hybrid vehicle.

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310 p. — ISBN 0 19 850416 0.

[2] www.mathworks.com

[3] MATLAB Simulink Software,” Hybrid Electric Vehicle model”.

[4] M. Ehsani, Y. Gao, A. Emadi, Modern Electric, Hybrid Electric and Fuel cell vehicles,

Fundamentals, Theory and Design, 2nd Ed. CRC Press, 2010

[5] T. J. Barlow et al. A reference book of driving cycles for use in the measurement of road

vehicle emissions, Report PPR354, TRL Limited.

[6] Can GOKCE et al Modeling And Simulation Of A Serial–Parallel Hybrid Electrical Vehicle

Nguyen Khac Tuan


[7] Mahesh Pandit et al Design and Simulation of Split Parallel Hybrid Electric Vehicle

International Journal of Current Engineering and Technology 2017.

[8] Xiaohua Zeng, Jixin Wang, Analysis and Design of the Power-Split Device for Hybrid

Systems. Springer 2018.

[9] Li Yaohua, Wang Ying, Zhao Xuan, Modelling and Simulation Study on a Series-parallel

Hybrid Electric Vehicle, World Electric Vehicle Journal Vol. 7 , 2015.

[10] Hiva Nasiri Maziar Parizadeh Ahmad Radan Abbas Ghayebloo , A MATLAB Simulink

Model for Toyota Prius 2004 based on DOE reports, IEEE, 2011.

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MODELING AND SIMULATION OF SERIES PARALLEL HEV USING ... · Vehicle dynamics and motion (a) and Simscape block for vehicle body (b) In order to model vehicle dynamics and motion,