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Hybrid Electric Vehicle (HEV) Power Train
Using Battery Model
Demonstration of a hybrid electric vehicle (HEV) power train using
SimPowerSystems™ and SimDriveline™.
Olivier Tremblay, Louis-A. Dessaint (Ecole de Technologie Superieure).
Contents
Circuit Description
Demonstration
Notes
References
See Also
Circuit Description
This example shows a multi-domain simulation of a HEV power train based on
SimPowerSystems and SimDriveline. The HEV power train is of the series-parallel
type, such as the one found in the Toyota Prius car [2]. This HEV has two kinds of
motive power sources: an electric motor and an internal combustion engine (ICE), in
order to increase the drive train efficiency and reduce air pollution. It combines the
advantages of the electric motor drive (no pollution and high available power at low
speed) and the advantages of an internal combustion engine (high dynamic
performance and low pollution at high speeds).
The Electrical Subsystem is composed of four parts: The electrical motor, the
generator, the battery, and the DC/DC converter.
The electrical motor is a 500 Vdc, 50 kW interior Permanent Magnet
Synchronous Machine (PMSM) with the associated drive (based on AC6
blocks of the SimPowerSystems Electric Drives library). This motor has 8
pole and the magnets are buried (salient rotor's type). A flux weakening vector
control is used to achieve a maximum motor speed of 6 000 rpm.
The generator is a 500 Vdc, 2 pole, 30 kW PMSM with the associated drive
(based on AC6 blocks of the SimPowerSystems Electric Drives library). A
vector control is used to achieve a maximum motor speed of 13000 rpm.
The battery is a 6.5 Ah, 200 Vdc, 21 kW Nickel-Metal-Hydride battery.
The DC/DC converter (boost type) is voltage-regulated. The DC/DC converter
adapts the low voltage of the battery (200 V) to the DC bus which feeds the
AC motor at a voltage of 500 V.
The Planetary Gear Subsystem models the power split device. It uses a planetary
device, which transmits the mechanical motive force from the engine, the motor and
the generator by allocating and combining them.
The Internal Combustion Engine subsystem models a 57 kW @ 6000 rpm gasoline
fuel engine with speed governor. The throttle input signal lies between zero and one
and specifies the torque demanded from the engine as a fraction of the maximum
possible torque. This signal also indirectly controls the engine speed. The engine
model does not include air-fuel combustion dynamics.
The Vehicle Dynamics subsystem models all the mechanical parts of the vehicle:
The single reduction gear reduces the motor's speed and increases the torque.
The differential splits the input torque in two equal torques for wheels.
The tires dynamics represent the force applied to the ground.
The vehicle dynamics represent the motion influence on the overall system.
The viscous friction models all the losses of the mechanical system.
The Energy Management Subsystem (EMS) determines the reference signals for the
electric motor drive, the electric generator drive and the internal combustion engine in
order to distribute accurately the power from these three sources. These signals are
calculated using mainly the position of the accelerator, which is between -100% and
100%, and the measured HEV speed. Note that a negative accelerator position
represents a positive brake position.
The Battery management system maintains the State-Of-Charge (SOC)
between 40 and 80%. Also, it prevents against voltage collapse by controlling
the power required from the battery.
The Hybrid Management System controls the reference power of the electrical
motor by splitting the power demand as a function of the available power of
the battery and the generator. The required generator power is achieved by
controlling the generator torque and the ICE speed.
There are five main scopes in the model:
The scope in the Main System named Car shows the accelerator position, the
car speed, the drive torque and the power flow.
The scope in the Electrical Subsystem named PMSM Motor Drive shows the
results for the motor drive. You can observe the stator currents ia, the rotor
speed and the motor torque (electromagnetic and reference).
The scope in the Electrical Subsystem named PMSM Generator
Drive shows the results for the generator drive. You can observe the stator
currents ia, the rotor speed and the motor torque (electromagnetic and
reference).
The scope in the Electrical Subsystem/Electrical measurements shows the
voltages (DC/DC converter, DC bus and battery), the currents (motor,
generator and battery) and the battery SOC.
The scope in the Energy Management Subsystem/Power Management
Systemshows the power references applied to the electrical components.
Demonstration
The demonstration shows different operating modes of the HEV over one complete
cycle: accelerating, cruising, recharging the battery while accelerating and
regenerative braking. Start the simulation. It should run for about one minute when
you use the accelerator mode. You can see that the HEV speed starts from 0 km/h and
reaches 73 km/h at 14 s, and finally decreases to 61 km/h at 16 s. This result is
obtained by maintaining the accelerator pedal constant to 70% for the first 4 s, and to
10% for the next 4 s when the pedal is released, then to 85% when the pedal is pushed
again for 5 s and finally sets to -70% (braking) until the end of the simulation. Open
the scope “Car” in the main system. The following explains what happens when the
HEV is moving:
At t = 0 s, the HEV is stopped and the driver pushes the accelerator pedal to
70%. As long as the required power is lower than 12 kW, the HEV moves
using only the electric motor power fed by the battery. The generator and the
ICE provide no power.
At t = 1.4 s, the required power becomes greater than 12 kW triggering the
hybrid mode. In this case, the HEV power comes from the ICE and the battery
(via the motor). The motor is fed by the battery and also by the generator. In
the planetary gear, the ICE is connected to the carrier gear, the generator to
the sun gear and the motor and transmission to the ring gear. The ICE power
is split to the sun and the ring. This operating mode corresponds to
acceleration.
At t = 4 s, the accelerator pedal is released to 10% (cruising mode). The ICE
cannot decrease its power instantaneously; therefore the battery absorbs the
generator power in order to reduce the required torque.
At t = 4.4 s, the generator is completely stopped. The required electrical power
is only provided by the battery.
At t = 8 s, the accelerator pedal is pushed to 85%. The ICE is restarted to
provide the extra required power. The total electrical power (generator and
battery) cannot reach the required power due to the generator-ICE assembly
response time. Hence the measured drive torque is not equal to the reference.
At t = 8.7 s, the measured torque reaches the reference. The generator provides
the maximum power.
At t = 10 s, the battery SOC becomes lower than 40% (it was initialised to
41.53 % at the beginning of the simulation) therefore the battery needs to be
recharged. The generator shares its power between the battery and the motor.
You can observe that the battery power becomes negative. It means that the
battery receives power from the generator and recharges while the HEV is
accelerating. At this moment, the required torque cannot be met anymore
because the electric motor reduces its power demand to recharge the battery.
At t = 13 s, the accelerator pedal is set to -70% (regenerative braking is
simulated). This is done by switching off the generator (the generator power
takes 0.5 s to decrease to zero) and by ordering the motor to act as a generator
driven by the vehicle’s wheels. The kinetic energy of the HEV is transformed
as electrical energy which is stored in the battery. For this pedal position, the
required torque of -250 Nm cannot be reached because the battery can only
absorb 21 kW of energy.
At t = 13.5 s, the generator power is completely stopped.
Some interesting observations can be made in each scope. During the whole
simulation, you can observe the DC bus voltage of the electrical system well regulated
at 500 V. In the planetary gear subsystem, you can observe that the Willis relation is
equal to -2.6 and the power law of the planetary gear is equal to 0 during the whole
simulation.
Notes
1. The power system has been discretized with a 60 us time step.
2. In order to reduce the number of points stored in the scope memory, a decimation
factor of 10 is used.
3. The AC6 blocks of SimPowerSystems (representing the motor and the generator)
and the DC/DC converter use the average value option of the detailed level. This
option allows to use a larger simulation time step.
ICE
