Transcript Presentation Title

NEW ENERGY MANAGEMENT
AND
HYBRID ENERGY STORAGE IN METRO RAILCAR
Istvan Szenasy
Szechenyi University, Dept. of Automation
Hungary
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
• Our approach uses modeling and simulation to evaluate the
potential of capacitive energy storage, an emerging
technology for renewable energy.
• Supercapacitors and other battery technologies can
contribute to rapid energy recovery.
• Fast energy recovery is especially important in electric
vehicles, in which powerful batteries enable regenerative
braking.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
• Renewing braking energy can significantly reduce the
total energy consumed in short-distance passenger traffic
using electrified lines or urban vehicles.
• Using Matlab-Simulink to model an urban-metro railcar
of the Budapest Metro Railway, we have demonstrated
that reducing the minimal capacitance value needed can
make supercapacitor-based energy storage more viable.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
Mass without load 34 t, fully loaded 44 t.
The total rated motor power is 200 kW,
the nominal speed is 75 km/h,
the maximum acceleration is greater than 1 m/s2,
the average distances are approximately 800 m between stations,
the overhead line voltage is 750V DC nominally.
The weakening of the DC motor fields begins over the speed of 36 km/h.
Charging-discharging of the SCAP ( abbreviated C) is executed by its bidirectional DC-DC
converter.
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NEW ENERGY MANAGEMENT
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IN METRO RAILCAR
Figure 2. Aim and direction of simulations and calculations in modelling
Our objective was to determine the lowest necessary capacitance value for a
supercapacitor (C) for the storage of all regenerative braking energy under different
conditions (mass, speeds, grades, stopping distances.)
We set the optimum initial supercapacitor voltage to 840 V DC before starting the railcar.
The lowest voltage of C was 400 V at the end of driving/start of braking.
We achieved this under all conditions by:
- tuning the variation of C, the capacitance value,
- applying the ‘beforehand charged energy to C’ ECo
applying the ‘constant charging power Pct’ from the overhead line,
through execution of a Matlab-Simulink simulation.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
The benefits of applying a constant charging-power Pct are:
• a system operating in a cycle in which capacitance charging is adequate,
• more equal grid,
• lower grid losses in the motoring operation mode.
In this investigation, the value of the factor d
d=(Ucmin /Ucmax)
(1)
is about 48 % if the Ucmin is 400 V. In a real-world application, this value of d is
acceptable.
Our simulation considered the two distances between stations.
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NEW ENERGY MANAGEMENT
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When varying the mass for a railcar from 30 to 55 t, the maximum motor current is a
function of mass to achieve similar acceleration and speed
Figure 7. The speed, the covered distance, the motor currents
and powers between two stations 800 m apart
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NEW ENERGY MANAGEMENT
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Energety characteristics (for the same case in figure 7)
Figure 8. Mass, m is varied from 35-55 t. Energy consumption of motors Emot,
energy of C Ec, voltage of C Uc and current of overhead line Ilinev. time. Due to constantly
charging power, line current remains constant.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
Improving the charging method
• If the charging power is not only a constant value but is varied by some
function of the total motor current or motor power over the time of
traction, then
• Line energy consumed is higher, energy derived from C is lower, and the
necessary value of C will be less.
• Consequently, the charging power has two components,
• - one as a function of motor power adjusted by a “correction factor”
• - another a much lower “constant charging power”, Pct.
• (In investigating other functions as well, the correction factor consistently
performed best, proportional to motor power.)
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Varied the set of energy management by a range of correction factor values, from 0 to 0.4
Figure 9 The energy consumption Eused does not depend on the correction factor. An increase in the current from
the line decreases the needed value of C.
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NEW ENERGY MANAGEMENT
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Calculating the actual energy Ech to charge into C by charging power Pch
may be realized with two components:
t
t
t
0
0
0
Ech   Pch dt   Pct dt  corrfact   Pm ot dt
At correction factor 0.4 the energy by motors flows in rate of 60
% from the C, and 40 % from overhead line.
These task is solvable by the adequate voltage-control of DC-DC
converters.
Energy management is executable with the controller, measuring
- motor current and voltage,
- speed,
- and line voltage
and calculating the motor power.
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NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
Application of the correction factor
v (km/h)
grade= -20,-10,0,10,20 %o, corrfact=0.4, d=800m, m=40 t, Imaxmot=f(grade)
60
20
s (m)
0
Imot (A)
400
Pmot (kW)
50
100
150
200 s
0
50
100
150
200 s
100
150
200 s
100
150
200 s
grade=20%o
200
0
-200
-400
0
50
400
grade=20%o
200
0
-200
400
I line (A)
0
1000
0
Figure 11. Overhead
line current is NOT
constant, varying in
proportion to the grade
at corrfact=0.4
grade=20%o
40
0
50
grade=20%o, C=11.6, Pct=48
200
0
grad=10%o, C=10.4, Pct=25
grade=0%o, C=10, Pct=2
grade= -20%o, C=15,
Pct=0
0
50
100
grade= -10%o, C=15, Pct=0
150
200 s
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NEW ENERGY MANAGEMENT
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The decrease of the needed capacitance by applied correct factor 0.4
Figure 14. The decreasing of the possible
need minimum values of the capacitance
between cases corrfact=0 and corrfact=0.4.
(In the case of corrfact=0, C increases by
5.5 F)
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NEW ENERGY MANAGEMENT
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The energy saving vs. the speed and the distance
Figure12. The rated energy saving vs. the
speed (km/h) and the distance (m) between
stations.
(The value of 0.55 is 55 %.) Energy saved
does not depend on the correction factor.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
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The actually needed minimum capacitance vs. the speed and mass
Figure 13. The actually needed
minimum values of the capacitance C
needed vs. the speed (km/h) and
mass (t) at corrfact=0.4,
by its two-varied function
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NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
Hybrid energy storage by Li-ion batteries and by supercapacitor
Fig. 10: The model of hybrid energy storage system on a railcar: the battery is parallel switched
with scap and both controlled by energy-management through own DC-DC converter. We sold a
separately variable method for handle the control of capacitive energy storage and one of the battery.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
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The curves of the Matlab’2009-modelled Li-ion battery (750 V, 30 Ah)
Fig. .The curves of the Li-ion battery. If the discharge current is low as like 40 A the discharging
time is 2,25 hour and this time decreases to 8,2 minutes if the current set to 180 A.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
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• Searching of a suitable control method
• We set a model according to Fig. 11, and we solved the separately variable
method for handle the control of capacitive energy storage and one of the
battery.
• For managing all these tasks we investigated the behaviour of two control
for the two energy-storage. In this model we applicate a current-limit
method instead of a current control: we had searched and set the suitable
upper and lower current values of the battery.
• We could show that the values of battery current are suitable all
operation cycle.
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NEW ENERGY MANAGEMENT
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• The limitations of battery current are suitable all operation
cycle.
• When the limitation operates the need current flows to or
from capacitor only.
• These peaks of current are proved by the capacitor in both
direction.
• In this solution achived an aime that the energy storage is
firstly proved by battery, but for giving or receiving the peakcurrent there is a little supercapacitor.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
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The system features in grade + 40 %o in 5 distances :
grade = 40% o, d = 5*800 m, I max mot = 300 A, m = 40 t
grade = 40% o, d = 5*800 m, I max mot = 300 A, m = 40 t
900
Ubatt, V
40
20
0
s, m
0
4000
100
200
300
400
500
2000
0
400
0
100
200
300
400
500
560s
800
700
560s
SOC batt, %
v, km/h
60
0
100
200
300
400
500
560s
0
100
200
300
400
500
560s
0
100
200
300
400
500
560s
0
100
200
300
400
500
560s
0
100
200
300
400
500
560s
68
66
64
62
60
58
200
Ibatt, A
Imot, A
200
0
-200
0
-200
0
100
200
300
400
500
560s
100
Icap, A
Pmot, kW
400
200
0
-100
-200
0
100
200
300
400
500
560s
300
Ucap, V
I line, A
0
200
0
100
200
300
400
500
Figure 14: Speed, distance, motor current, motor
power and line current. Grade = + 40%o.
560s
800
600
Figure 15: Battery voltage, S.O.C., current battery, current SCAP, voltage
SCAP according to Fig. 14. PCt=124 kW, cf=0.271, SOCo=66 %, current
limits +172, - 180 A.
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NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
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The system features in grade - 30 %o :
Fig. 26. The grade is - 30 %o.
The speed of energy
consumption (‘dch’) is high,
and under regenerativ
braking at charging (‘ch’) is
longer and moderate.
PCt=0 kW, cf=0, SOCo=66 %,
current limits +180, - 217 A
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NEW ENERGY MANAGEMENT
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The needed capacitance: 1 to 1.6 F, the decreasing is
very significant
(for a hybrid energy
storage, with cooperation a Li-ion battery 750V, 30 Ah)
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
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• The available decreasing ratio of the needed hybrid energy storage system
at case SCAP is 30 % to 60 % - with this improved hybrid energy control
method.
• These are significant values as decreasing in volume, mass and price.
• This novel process and its results are practically independent of the type
of the traction motor.
• For these tasks the mass of SCAP is about 1500 kg. The mass of 800 kg
about with presented Li-ion battery + SCAP hybrid storage-system, without
converters.
• Mass reduction of this hybrid storage system is significant, about 50 %
rated to supercapacitor type energy storage.
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
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The correction factor must be varied, 0.1 to 0.4, instead
of a constant value 0.4
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
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• The change of Pct, constant power from line is larger:
GREAT MINDS THINK ELECTRIC / WWW.EVS26.ORG
NEW ENERGY MANAGEMENT
AND HYBRID ENERGY STORAGE
IN METRO RAILCAR
Thanks for your attantion
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