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energies
Article
Design and Application of a Power Unit to Use
Plug-In Electric Vehicles as an Uninterruptible
Power Supply
Gorkem Sen 1 , Ali Rifat Boynuegri 2 , Mehmet Uzunoglu 2, *, Ozan Erdinc 2,3 and
João P. S. Catalão 3,4,5
1
2
3
4
5
*
Department of Electronics and Automation, Ipsala Vocational School, Trakya University, Ipsala,
Edirne 22400, Turkey; [email protected]
Department of Electrical Engineering, Faculty of Electric-Electronics, Yildiz Technical University Davutpasa
Campus, Esenler, Istanbul 34220, Turkey; [email protected] (A.R.B.); [email protected] (O.E.)
Instituto de Engenharia de Sistemas e Computadores—Investigação e Desenvolvimento (INESC-ID),
Inst. Super. Tecn., University of Lisbon, Av. Rovisco Pais, 1, Lisbon 1049-001, Portugal; [email protected]
Faculty of Engineering, University of Porto, R. Dr. Roberto Frias, Porto 4200-465, Portugal
Department of Electromechanical Engineering, University of Beira Interior, R. Fonte do Lameiro,
Covilhã 6201-001, Portugal
Correspondence: [email protected]; Tel.: +90-212-383-5807
Academic Editor: K. T. Chau
Received: 8 January 2016; Accepted: 26 February 2016; Published: 7 March 2016
Abstract: Grid-enabled vehicles (GEVs) such as plug-in electric vehicles present environmental and
energy sustainability advantages compared to conventional vehicles. GEV runs solely on power
generated by its own battery group, which supplies power to its electric motor. This battery group can
be charged from external electric sources. Nowadays, the interaction of GEV with the power grid is
unidirectional by the charging process. However, GEV can be operated bi-directionally by modifying
its power unit. In such operating conditions, GEV can operate as an uninterruptible power supply
(UPS) and satisfy a portion or the total energy demand of the consumption center independent from
utility grid, which is known as vehicle-to-home (V2H). In this paper, a power unit is developed for
GEVs in the laboratory to conduct simulation and experimental studies to test the performance of
GEVs as a UPS unit in V2H mode at the time of need. The activation and deactivation of the power
unit and islanding protection unit are examined when energy is interrupted.
Keywords: grid-enabled vehicles; distributed generation; plug-in electric vehicles; plug-in hybrid
electric vehicles; vehicle-to-home; uninterruptible power supply
1. Introduction
The world faces an environmental crisis as the volatile prices of petroleum meet rising concerns
regarding each nation’s energy independence and global warming issues due to greenhouse gas
(GHG) emissions. In this regard, the transportation sector plays a crucial and growing role in world
energy use and, accordingly, GHG emissions, accounting for approximately 15% of overall GHG
emissions [1,2]. These factors contribute to increase interest in alternative vehicle technologies.
Nowadays, electrification of transportation has become an important, supported industry trend.
Along the past few years, grid-enabled vehicles (GEVs) such as plug-in electric vehicles (PEVs) and
plug-in hybrid electric vehicles (PHEVs) are growing in popularity due to increasing governmental
regulations on industries and public will to reduce GHG emissions [3]. Given GEVs’ popularity,
different types are estimated to constitute 35% of the automotive market by 2025 [4]. For this reason,
Energies 2016, 9, 171; doi:10.3390/en9030171
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Energies 2016, 9, 171
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many automotive manufacturers have already started to expand their productions to benefit from the
growing GEV market.
In the near future, increasing number of GEVs will be connected to power distribution systems
for charging their batteries [5]. In [6], Electric Power Research Institute (EPRI) estimates new vehicle
market shares of conventional vehicles (CVs) and PHEVs using a choice-based market modeling of
customer choice. Results of this report suggest that CVs will have a market share of 56%, 14%, and
5% and PHEVs will have a market share of 20%, 62%, and 80% by 2050 in low, medium, and high
penetration scenarios, respectively. In Morgan Stanley’s report [7], specific information is used to
forecast sales of GEVs. Market demand of GEV is forecasted to reach one million by 2020. The study
of Pacific Northwest National Laboratory (PNNL) [8] examines GEV market penetration scenarios.
Yearly market penetration ratios for PHEVs are estimated from 2013 to 2045 for three scenarios: hybrid
technology-based assessment, R&D goals achieved, and supply constrained scenarios, in which PHEV
market penetration is estimated to reach 9.7%, 9.9%, and 26.9% by 2023, and 11.9%, 29.8%, and 72.7%
by 2045, respectively. The study of Oak Ridge National Laboratory (ORNL) [9] estimates that the
demand for GEVs will be almost one million by 2015 [9]. It is clear that massive integration of GEVs
on the power distribution system will result in a significant increase in electric energy demand and
will raise load values at peak times [10]. Also, various studies have already been carried out to predict
the effects of GEVs on the power distribution system. As a result of these studies, GEVs have been
observed to cause some special effects such as phase imbalance, power quality issues, grid stability,
transformer degradation and failure, and circuit breaker and fuse blowout on the power distribution
systems [11–15].
All these problems can be prevented with well-designed GEV battery chargers and intelligent
charging as part of the smart grid technologies. Massive integration of batteries of GEVs into the
power grid can create some opportunities. With smart grid technologies, the function of the GEVs as
a mobile energy storage unit in the power grid includes some opportunities such as reactive power
compensation, harmonic filtering, voltage support, reducing frequency fluctuations, functioning as
an emergency power supply such as an uninterruptible power supply (UPS) which is often named
as vehicle-to-home (V2H), improving the effectiveness of home renewable energies by using GEV
as storage, load balancing, peak shaving unit [16–23]. However, the design and control of a GEV
on-board battery charger is important to perform specified operating conditions.
As it is well known, an energy storage unit that provides the required power for a vehicle is
employed in GEVs. This energy storage unit must be recharged at charging points. Nowadays, the
interaction of a commercial GEV with the grid is generally unidirectional—the charging process.
However, GEVs can be operated bi-directionally by modifying the design of power units of GEV.
Thus, the storage units can be supplied to small isolated systems such as single households without
the power grid in V2H mode. Due to the large amount of energy stored in batteries of GEVs, they can
supply the demand of the consumption center. The general scheme of the V2H operating condition
is illustrated in Figure 1. V2H operating conditions would offer the possibility of using a GEV as a
domestic back-up power as a UPS [24,25]. Instead, a power unit that can be utilized for the consumption
center connection of vehicular systems is important for the realization of this operating condition.
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Figure 1. Block scheme of the V2H operating condition.
Figure 1. Block scheme of the V2H operating condition.
The simulation studies are performed in MATLAB & Simulink environments. For the
The mainstudies,
idea presented
in this formed
paper isby
using
GEVsgroup,
as a power
supply
the consumption
experimental
a test platform
a battery
a power
unit, to
measurement
units,
center
when
needed.
The
proposed
study
contributes
to
the
relevant
literature
regarding
the
fact
an islanding protection unit, a load unit, a dead-time generation unit, and a dSPACE control unit
is
that
both
the
simulation
and
the
experimental
analyses
have
been
conducted
for
use
of
GEVs
as
UPS.
configured to test V2H operating conditions—different from the existing literature, which considers
The
concept
of using
GEVs aspoint
a UPSofunit
is different from the regular UPS structures. Firstly, the GEVs
the topic
a solely
theoretical
view.
are not
continuously
available
at
the
residential
as Section
the GEV2 owners
usethe
their
GEVs
during
The remainder of this paper is organized premises
as follows:
describes
V2H
simulation
daily
forhas
traveling
to work, etc.
of GEVs
for such purposes
should
be limited
modellife
that
been developed
and Besides,
explains the
the use
physical
configuration
of the test
platform
as well
by
comfort
conditions
as
the
GEV
owner
requiring
a
minimum
level
of
charge
for
his/her
GEV
for
as the testing methodology; Section 3 demonstrates the simulation and experimental results; and
possible
unexpected
GEV
use
during
the
evening,
etc.
Moreover,
such
systems
should
be
continuously
finally, conclusions are made in Section 4.
controlled regarding the fact that battery charge/discharge lifetime is limited and uncontrolled daily
use
of GEVs
for such purposes
will present drawbacks in this regard. However, the GEVs can be
2. System
Description
and Methodology
considered as a mobile UPS unit readily available during energy outages, etc. for supplying at least the
In order to test and improve the effectiveness of the proposed methodology, an initial analysis
minimum level of electrical energy for sustaining daily activities at home, work, etc. as GEVs are also
is performed in a simulation environment before conducting experimental studies. In this simulation
mostly idle during the daytime (at work, etc.) even when the GEV is not at home. A limitation for the
study, the modeling and analysis of the prepared system are realized using MATLAB & Simulink,
minimum State-of-Charge (SoC) is implemented within the control structure. In addition, an islanding
Sim Power Systems. Afterwards, a test platform is established in order to use GEV as a UPS if
unit is designed specifically for the mentioned type of use for GEVs in this study.
necessary. The parameters of the components used in the test platform are normalized to real GEV
The simulation studies are performed in MATLAB & Simulink environments. For the experimental
specifications. The concept of the simulation model and test platform, control algorithms, and the
studies, a test platform formed by a battery group, a power unit, measurement units, an islanding
principle of the operation as well as the general structure of the V2H are explained in detail in the
protection unit, a load unit, a dead-time generation unit, and a dSPACE control unit is configured to
following subsections.
test V2H operating conditions—different from the existing literature, which considers the topic a solely
theoretical
point
of view.
2.1. Simulation
Model
The remainder of this paper is organized as follows: Section 2 describes the V2H simulation
allbeen
subsystems
of the
structure
in theconfiguration
performed simulation
areas
prepared
modelFirstly,
that has
developed
andgeneral
explains
the physical
of the test study
platform
well as
separately.
The
simulation
study
consists
of
four
units:
Battery,
DC-DC
converter,
DC-AC
converter
the testing methodology; Section 3 demonstrates the simulation and experimental results; and finally,
(inverter), and
load
conclusions
are the
made
in model.
Section The
4. block diagram of the prepared system is shown in Figure 2 and
the simulation model is given in Figure 3. Also, the parameter values used in the simulation are
given in Table1. In this simulation study, the charging process of the GEV is not included in order to
reduce the complexity in a model that mainly focuses on the V2H operating mode. For this reason,
the power grid and the islanding protection unit are not modeled and used in the simulation study.
Energies 2016, 9, 171
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2. System Description and Methodology
In order to test and improve the effectiveness of the proposed methodology, an initial analysis is
performed in a simulation environment before conducting experimental studies. In this simulation
study, the modeling and analysis of the prepared system are realized using MATLAB & Simulink,
Sim Power Systems. Afterwards, a test platform is established in order to use GEV as a UPS if
necessary. The parameters of the components used in the test platform are normalized to real GEV
specifications. The concept of the simulation model and test platform, control algorithms, and the
principle of the operation as well as the general structure of the V2H are explained in detail in the
following subsections.
2.1. Simulation Model
Firstly, all subsystems of the general structure in the performed simulation study are prepared
separately. The simulation study consists of four units: Battery, DC-DC converter, DC-AC converter
(inverter), and the load model. The block diagram of the prepared system is shown in Figure 2 and
the simulation model is given in Figure 3. Also, the parameter values used in the simulation are
given in Table 1. In this simulation study, the charging process of the GEV is not included in order to
reduce the complexity in a model that mainly focuses on the V2H operating mode. For this reason,
Energies 2016, 9, 171
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the power grid and the islanding protection unit are not modeled and used in the simulation study.
Under
operation is
is important
for safety
Under normal
normal conditions,
conditions, islanding
islanding operation
important for
safety as
as it
it separates
separates the
the power
power grid
grid
Energies
2016, 9, 171 center. Thus, the electrical energy generated by the GEV is only consumed
4 of 15
and
the
consumption
by the
and the consumption center. Thus, the electrical energy generated by the GEV is only consumed
by
consumption
center
in
the
V2H
operation
mode
by
this
way
the
staff
of
the
grid
operator
can
safely
the consumption
in the
V2H operation
by this
the
of thethe
grid
operator
Under normal center
conditions,
islanding
operation mode
is important
forway
safety
as staff
it separates
power
grid can
rectify
the fault.
Also
even
when
the
power
grid isgrid
powered
up again
the GEV
is
temporarily
kept
safelyand
rectify
the
fault.
Also
even
when
the
power
is
powered
up
again
the
GEV
is
temporarily
the consumption center. Thus, the electrical energy generated by the GEV is only consumed by
mechanically
isolated
to
protect
the
power
converters
from
transient
effects
that
may
occur.
kept the
mechanically
isolated
to the
protect
powermode
converters
transient
that
may occur.
consumption
center in
V2H the
operation
by thisfrom
way the
staff ofeffects
the grid
operator
can
safely rectify the fault. Also even when the power grid is powered up again the GEV is temporarily
kept mechanically isolated to protect the power converters from transient effects that may occur.
Figure 2.
2. General
scheme of
of the
the simulation
simulation model.
model.
Figure
General scheme
Figure 2. General scheme of the simulation model.
Figure3.
3. Simulation
Simulation model.
Figure
model.
Figure
3. Simulation
model.
Table1.1.Parameters
Parameters of
of the
Table
thesimulation
simulationsystem.
system.
Parameters
Parameters
Battery Voltage (V)
Battery Voltage (V)
Battery Ah Value (Ah)
Battery
AhSoC
Value
Battery
(%) (Ah)
Battery
SoC
(%)
DC/DC
Converter
Type
DC/DC
Converter
DC/DC
ConverterType
Output Voltage (V)
DC/DC
ConverterOutput
Switching
Frequency
DC/DC
Converter
Voltage
(V) (kHz)
DC/AC
Converter
Type
DC/DC Converter Switching Frequency (kHz)
DC/AC
ConverterType
Control Method
DC/AC
Converter
DC/AC
Converter
Switching
Frequency (kHz)
DC/AC Converter Control
Method
Filter Inductance Value (mH)
DC/AC Converter Switching Frequency (kHz)
Filter Capacitor Value (µ F)
Values
Values
240
240
10
10
100
100
Bidirectional
Bidirectional
450
15450
Full
15Bridge
Sinusoidal
PWM
Full Bridge
10Sinusoidal PWM
0.03
10
100
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Table 1. Parameters of the simulation system.
Parameters
Values
Battery Voltage (V)
Battery Ah Value (Ah)
Battery SoC (%)
DC/DC Converter Type
DC/DC Converter Output Voltage (V)
DC/DC Converter Switching Frequency (kHz)
DC/AC Converter Type
DC/AC Converter Control Method
DC/AC Converter Switching Frequency (kHz)
Filter Inductance Value (mH)
Filter Capacitor Value (µF)
240
10
100
Bidirectional
450
15
Full Bridge
Sinusoidal PWM
10
0.03
100
In this study, as the first unit in simulation, the existing battery model within the Simulink library
was selected. The type of battery is lithium-ion and the battery values determined as 240 V, 10 Ah, and
initial SoC of 100%.
The second unit is a load model that models the consumption center in the simulation study.
This load model consists of a controlled voltage source, resistor, and the control block of the controlled
voltage source. As the basic operating principle of this system, control block of the load model
generates the reference voltage value of the controlled voltage source and current is drawn through 1
ohm virtual resistance. The control inputs of the load unit are active power (P), reactive power (Q),
and the instantaneous value of the voltage at the load connection point (V) is used as a feedback signal
to calculate reference current value. The mentioned P and Q values of a three-story office building are
used. The output of the load model is the voltage signal generated for the controlled voltage source.
The
signal
method for the controlled voltage source is shown in Figure 4.
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2016,production
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Figure 4. Control block of load model.
Figure 4. Control block of load model.
First, as in Figure 4, angle (φ) is calculated in the unit of radians. The power factor (cos φ) value
First, as in
Figure
4, angle
is calculated
in the unit
radians.
powerthe
factor
(cosdifference
ϕ) value
is calculated
with
φ. Also,
φ is(ϕ)
converted
to seconds
fromofradians
forThe
creating
phase
is
calculated
with ϕ. and
Also,
ϕ voltage.
is converted
to seconds
phase difference
between
the current
the
Afterwards,
thefrom
RMSradians
value offor
thecreating
currentthe
is calculated
so that
between
the
current
and
the
voltage.
Afterwards,
the
RMS
value
of
the
current
is
calculated
so wave
that the
the peak value of the current can be specified. After all of these processes, a pure sine
is
peak
valuewith
of the
current
can beangle
specified.
all of these
processes,
a pure
sine
wave
is generated
generated
the
same phase
with After
the voltage
of load
connection
point.
This
reference
wave
with
same phase
angleand
with
the voltage
point.
This
reference
wave form
is
form the
is shifted
to φ angle
multiplied
by of
theload
peakconnection
value of the
current
and
the reference
current
shifted
to
ϕ
angle
and
multiplied
by
the
peak
value
of
the
current
and
the
reference
current
signal
signal is produced. Finally, the measured current signal is subtracted from the voltage value on the
is
produced.
Finally,
measured
current
signal
is subtracted
from thesource
voltage
on the load
load
connection
point.the
Thus,
the control
signal
for the
voltage controlled
is value
produced.
connection
point.
Thus,
the
control
signal
for
the
voltage
controlled
source
is
produced.
The third unit is a DC–DC converter, which generates an appropriate DC voltage for the
The input.
third unit
a DC–DC
converter,
whichbi-directional
generates an operation
appropriate
DC voltage
the inverter
inverter
ThisisDC–DC
converter
requires
(charging
andfor
discharging
of
input.
This
DC–DC
converter
requires
bi-directional
operation
(charging
and
discharging
of
the
the battery). In this simulation study, the bi-directional DC–DC converter is operated only for
battery).
In this
study,
the bi-directional
is operated
for discharging
discharging
thesimulation
battery. The
charging
of the GEV DC–DC
battery converter
is not in the
scope of only
this study;
relevant
the
battery.
The charging
the GEV in
battery
is not in the
scope of this
study;converter
relevant control
charging
charging
methodologies
areofpresented
[24]. Therefore,
a bi-directional
DC–DC
is
methodologies
are
presented
in
[24].
Therefore,
a
bi-directional
DC–DC
converter
control
is
realized
realized just for the boost operating state. In control unit of the converter, the reference and
just
for the values
boost operating
state.
In control
unit of theFirst,
converter,
the reference
values of
measured
of DC bus
voltage
are required.
the control
unit ofand
themeasured
DC–DC converter
receives the information of the DC bus voltage in the DC–DC converter output. Then, the reference
voltage information is compared with the measured voltage in the PI controller. The DC reference
voltage value is chosen as 425 VDC for resembling the voltage value at load connection to the grid
voltage value. After this process, a pulse width modulation (PWM) signal is obtained by comparison
of a saw tooth signal, with the signal received from the output of PI controller. Afterward, zero
The third unit is a DC–DC converter, which generates an appropriate DC voltage for the
inverter input. This DC–DC converter requires bi-directional operation (charging and discharging of
the battery). In this simulation study, the bi-directional DC–DC converter is operated only for
discharging the battery. The charging of the GEV battery is not in the scope of this study; relevant
charging
methodologies
are presented in [24]. Therefore, a bi-directional DC–DC converter control
Energies
2016,
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realized just for the boost operating state. In control unit of the converter, the reference and
measured values of DC bus voltage are required. First, the control unit of the DC–DC converter
DC
bus voltage
are required.
First,
of the
DC–DC
converter
receives
thethe
information
receives
the information
of the
DCthe
buscontrol
voltageunit
in the
DC–DC
converter
output.
Then,
reference
of
the
DC
bus
voltage
in
the
DC–DC
converter
output.
Then,
the
reference
voltage
information
is
voltage information is compared with the measured voltage in the PI controller. The DC reference
compared
withisthe
measured
the PI controller.
The DC
reference
valuetoisthe
chosen
voltage value
chosen
as 425voltage
VDC forinresembling
the voltage
value
at loadvoltage
connection
grid
as
425
V
for
resembling
the
voltage
value
at
load
connection
to
the
grid
voltage
value.
After
this
DC
voltage value.
After this process, a pulse width modulation (PWM) signal is obtained by comparison
process,
a
pulse
width
modulation
(PWM)
signal
is
obtained
by
comparison
of
a
saw
tooth
signal,
with
of a saw tooth signal, with the signal received from the output of PI controller. Afterward, zero
the
signal
received
from
the output
controller.
zero
is S1
given
S1 switch
signal
is given
to the
S1 switch
and of
thePIPWM
signalAfterward,
is sent to the
S2signal
switch.
andto
S2the
switches
are
and
the
PWM
signal
is
sent
to
the
S2
switch.
S1
and
S2
switches
are
shown
in
Figure
3.
In
order to
shown in Figure 3. In order to maintain the DC bus voltage, the control algorithm presented
in
maintain
the
DC
bus
voltage,
the
control
algorithm
presented
in
Figure
5
is
used.
Figure 5 is used.
Figure 5. Control algorithm of DC–DC converter during V2H operation mode.
Figure 5. Control algorithm of DC–DC converter during V2H operation mode.
The fourth and the last unit is the power unit. This unit includes an inverter and the LC filter,
The
the last
unit is
the power
unit. Thispulse
unit width
includes
an inverter
and thecontrol
LC filter,
which
is fourth
locatedand
in the
inverter
output.
A sinusoidal
modulation
(SPWM)
is
which
is
located
in
the
inverter
output.
A
sinusoidal
pulse
width
modulation
(SPWM)
control
is
applied at the aforementioned inverter. Due to the SPWM method, the switching elements (IGBT,
applied
at are
the entered
aforementioned
Due
to the SPWM
method,
the switching
elements
MOSFET)
in cutoffinverter.
mode and
transmission
mode
to generate
a sinusoidal
wave(IGBT,
form
MOSFET)
areperiod.
enteredThus,
in cutoff
mode and
transmission
modesignal
to generate
sinusoidalAwave
form
during each
the variable
amplitude
sinusoidal
can bea obtained.
sinusoidal
during
period.
Thus, thewith
variable
amplitude
sinusoidal
signal
can for
be obtained.
sinusoidal
control each
signal
is compared
a higher
frequency
triangle
wave
achievingAthe
desired
control
signal
is
compared
with
a
higher
frequency
triangle
wave
for
achieving
the
desired
frequency
frequency of SPWM. In this comparison result, the SPWM signals required for cross-arms of the
of
SPWM.
thisobtained.
comparison
the SPWM
signals
for cross-arms
power
unitInare
An result,
LC passive
filter is
used required
to filter the
harmonics of
onthe
thepower
outputunit
of are
the
obtained.
An
LC
passive
filter
is
used
to
filter
the
harmonics
on
the
output
of
the
inverter.
The
filter’s
inverter. The filter’s inductance and capacitor values are selected as 0.03 mH and 100 μF,
inductance
and
capacitor
are and
selected
as 0.03 mH
100 µF,the
respectively.
The filter is designed
respectively.
The
filter is values
designed
implemented
toand
minimize
system harmonics.
and implemented
to
minimize
the
system
harmonics.
All subsystems in the simulation study are prepared separately, as mentioned before. Then, the
All
subsystems
in the
simulationisstudy
are prepared
mentioned
before. Then, the
interconnection
of these
subsystems
performed
and theseparately,
simulationas
results
are obtained.
interconnection of these subsystems is performed and the simulation results are obtained.
2.2. Test Platform
An experimental test platform is built to verify the controller system design and to implement a
successful connection between the GEV and the end-user premise. The parameters of the components
used in the test platform are normalized to certain values in order to reduce high costs, minimize the
size of the components, and achieve flexible controllability. This test platform consists of a battery, a
power unit (inverter), measurement units, an islanding protection unit, a dead-time generation unit,
and a dSPACE control unit. The block diagram of the mentioned system is given in Figure 6. The test
platform for experimental studies is shown in Figure 7. Also, the values of components used in the test
platform are given in Table 2.
components used in the test platform are normalized to certain values in order to reduce high costs,
minimize the size of the components, and achieve flexible controllability. This test platform consists
of a battery, a power unit (inverter), measurement units, an islanding protection unit, a dead-time
generation unit, and a dSPACE control unit. The block diagram of the mentioned system is given in
Figure
6.9,The
Energies
2016,
171 test platform for experimental studies is shown in Figure 7. Also, the values7 of
of 17
Figure 6. General scheme of the test platform.
components used in the test platform are given in Table 2.
Table 2. Parameters of the test platform.
Parameters
Values
Battery Voltage (V)
24
Battery Ah Value (Ah)
18
Battery SoC (%)
100
Power Unit Type
Inverter
Power Unit Control Method
Sinusoidal PWM
Power Unit Switching Frequency (kHz)
10
Filter Inductance Value (mH)
1
Filter Capacitor Value (µ F)
15
Figure 6. General scheme of the test platform.
Figure
6.
General
scheme
of
the
test
platform.
Load (Ω)
17
Table 2. Parameters of the test platform.
Parameters
Battery Voltage (V)
Battery Ah Value (Ah)
Battery SoC (%)
Power Unit Type
Power Unit Control Method
Power Unit Switching Frequency (kHz)
Filter Inductance Value (mH)
Filter Capacitor Value (µ F)
Load (Ω)
Values
24
18
100
Inverter
Sinusoidal PWM
10
1
15
17
Figure 7. Photograph of the test platform.
Figure 7. Photograph of the test platform.
Table 2. Parameters of the test platform.
Parameters
Values
Battery Voltage (V)
24
Battery Ah Value (Ah)
18
Battery SoC (%)
100
Power Unit Type
Inverter
Power Unit Control Method
Sinusoidal PWM
Power Unit Switching Frequency (kHz)
10
Filter Inductance Value
1
Figure(mH)
7. Photograph of the test platform.
Filter Capacitor Value (µF)
15
Load (Ω)
17
2.2.1. Control Algorithm
The control algorithm was developed utilizing MATLAB & Simulink and SimPowerSystems.
A dSPACE embedded control unit is used as the controller in experimental studies. The control
algorithm of the test platform, as illustrated in Figure 8, includes eight input and two output signals.
Five of the input signals are measurement data taken from sensors. At first, these measurement data
enter the calibration block and signals are converted to the actual values. Then, the calibrated signals
enter the data storage block. The grid voltage information is sent to the grid monitoring block from
The control algorithm was developed utilizing MATLAB & Simulink and SimPowerSystems.
A dSPACE embedded control unit is used as the controller in experimental studies. The control
algorithm of the test platform, as illustrated in Figure 8, includes eight input and two output signals.
Five of the input signals are measurement data taken from sensors. At first, these measurement data
Energies 2016, 9, 171
8 of 17
enter the calibration block and signals are converted to the actual values. Then, the calibrated signals
enter the data storage block. The grid voltage information is sent to the grid monitoring block from
the
of of
incoming
gridgrid
voltage
is checked
if it isifinit the
voltage
range
the data
datastorage
storageblock.
block.The
Theinformation
information
incoming
voltage
is checked
is in
the voltage
specified
by the grid
block. Accordingly,
the islanding the
protection
signal
is generated.
Also,
range specified
by monitoring
the grid monitoring
block. Accordingly,
islanding
protection
signal
is
some
data are
sent
to the
V2H
block,
which
provides
safe system
operation.
These
data are
generated.
Also,
some
data
are control
sent to the
V2H
control
block, which
provides
safe system
operation.
the
battery
the terminal
of the
powervoltage
unit, respectively.
Furthermore,
the V2H
These
datavoltage
are theand
battery
voltagevoltage
and the
terminal
of the power
unit, respectively.
control
block receives
confirmation
signal ofthe
theconfirmation
end-user, SoC
limit,of
the
price
of electricity,
and the
Furthermore,
the V2Hthe
control
block receives
signal
the
end-user,
SoC limit,
the
islanding
protectionand
signal
the grid
monitoring
block.
Depending
on these inputsV2H
operation
price of electricity,
thefrom
islanding
protection
signal
from
the grid monitoring
block. Depending
is
by generating
SPWM signal.
The
signalSPWM
generated
by dSPACE
is applied
to the power
onstarted
these inputsV2H
operation
is started
bySPWM
generating
signal.
The SPWM
signal generated
by
unit
through
the dead-time
generation
unit in order
to perform
the energy
transfer
from
the battery
dSPACE
is applied
to the power
unit through
the dead-time
generation
unit
in order
to perform
the
to
the load.
In addition
this generated
signal,
the dSPACE
unitsignal,
transmits
another control
energy
transfer
from thetobattery
to the load.
In addition
to thiscontrol
generated
the dSPACE
control
signal
to the islanding
protection
for commissioning
andprotection
decommissioning
Lastly,and
the
unit transmits
another
control unit
signal
to the islanding
unit forprocedures.
commissioning
decommissioning
procedures.
Lastly,
SPWM block
operates
to the
confirmation
signal
SPWM
block operates
according
to thethe
confirmation
signal
of theaccording
end-user and
generates
the driving
of the required
end-userfor
and
generates
the In
driving
signal required
forthe
theSPWM
powerblock
unit. for
In this
experimental
signal
the
power unit.
this experimental
study,
the power
unit is
study, theatSPWM
block for the power unit is operated at 10 kHz.
operated
10 kHz.
Figure 8.
8. The
The control
control algorithm
algorithm of
of the
the test
test platform.
platform.
Figure
2.2.2. Operation
Operation of
of the
the Test
Test Platform
Platform
2.2.2.
Initially, the
the battery
battery group
group and
and the
the power
power unit
unit representing
representing aa GEV
GEV are
are connected
connected to
to the
the grid
grid
Initially,
connectionpoint
pointvia
viaaatransformer.
transformer.However,
However,
this
study,
GEV
is operated
a UPS
therefore
connection
inin
this
study,
GEV
is operated
as aasUPS
andand
therefore
the
the
charging
of
the
battery
is
not
included
in
the
experimental
study
and
the
power
unit
is
employed
charging of the battery is not included in the experimental study and the power unit is employed only
only
for discharging
the battery.
The reason
for using
a transformer
theplatform
test platform
the quite
for
discharging
the battery.
The reason
for using
a transformer
in theintest
is theisquite
low
low level
of battery
voltage
according
togrid
the grid
voltage.
At beginning
the beginning
of experimental
the experimental
study,
level
of battery
voltage
according
to the
voltage.
At the
of the
study,
the
the grid
supplies
the load
and GEV
is in standby
depending
the of
status
of the grid.
power
grid.
grid
supplies
the load
and GEV
is in standby
mode,mode,
depending
on the on
status
the power
After
a
After
a
while,
the
power
failure
occurs
on
the
grid
side
and
the
load
does
not
remain
energized.
As
while, the power failure occurs on the grid side and the load does not remain energized. As a result ofa
result
of this
the recommended
V2H operating
mode
will
take action.
Frommoment,
this moment,
the power
this
fault,
thefault,
recommended
V2H operating
mode will
take
action.
From this
the power
unit
unit
requires
the
formation
of
the
necessary
conditions
to
operate
as
an
UPS.
Those
conditions
are:
requires the formation of the necessary conditions to operate as an UPS. Those conditions are:
the initial
initial SoC
SoC of
of the
the battery
batteryisisgreater
greaterthan
thanthe
thereference
referenceSoC
SoClimit,
limit,
‚ IfIf the
the end-user
end-user gives
gives permission
permissionfor
forV2H,
V2H,
‚ IfIf the

If the islanding protection process is realized (the grid is isolated from loads and power unit),
‚
If the islanding protection process is realized (the grid is isolated from loads and power unit),

If the voltage value of the power unit is approximately zero regarding the measurement unit signal,
‚
If the voltage value of the power unit is approximately zero regarding the measurement unit signal,

If the price of electricity is greater than the reference price value (optional).
‚
If the price of electricity is greater than the reference price value (optional).
If all of the foregoing conditions are met, the control system formed by dSPACE allows GEV to be
operated as a UPS. In this V2H operating mode, the power unit is operated as voltage-controlled and
the power flow is provided from the battery to the loads.
The last step is the termination of this operation mode. There are several conditions for the
termination of this operation mode. The mentioned conditions for operation termination are:
If all of the foregoing conditions are met, the control system formed by dSPACE allows GEV to
be operated as a UPS. In this V2H operating mode, the power unit is operated as voltage-controlled
and the power flow is provided from the battery to the loads.
The
last
step is the termination of this operation mode. There are several conditions for
Energies
2016,
9, 171
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17
termination of this operation mode. The mentioned conditions for operation termination are:
‚
‚
‚
If the
the SoC
SoC of
of the
the battery
battery is
is lower
lower than
than the
the reference
reference SoC
SoC limit,
limit,
If
If the
the end-user
end-user cancels
cancels the
the operation
operation status,
status,
If
If
the
measurement
signals
of
the
grid
side show
show existence
If the measurement signals of the grid side
existence of
of energy
energy (if
(if the
the voltage
voltage value
value of
of the
the
power
grid
is
within
appropriate
values
for
standards),
power grid is within appropriate values for standards),
‚
If the
the price
price of
of grid
grid electricity
electricity is
is more
more than
than the
the reference
reference value
value (optional).
(optional).
If
As a result of the provision of one or more termination conditions, dSPACE terminates sending
As a result of the provision of one or more termination conditions, dSPACE terminates sending
signals to the power unit through the dead-time generation unit. After that, dSPACE receives and
signals to the power unit through the dead-time generation unit. After that, dSPACE receives and
evaluates data coming from sensors. As a result of this evaluation, dSPACE interrupts the signal of
evaluates data coming from sensors. As a result of this evaluation, dSPACE interrupts the signal of the
the islanding protection unit (contactor) when there is no problem in terms of security
islanding protection unit (contactor) when there is no problem in terms of security (approximately two
(approximately two cycles). Consequently, the grid-load connection can be realized again.
cycles). Consequently, the grid-load connection can be realized again.
3.
3. Results
Results
In
In this
this section,
section, the
the behavior
behavior of
of the
the GEV
GEV in
in V2H
V2H operation
operation mode
mode is
is examined
examined firstly
firstly by
by the
the
simulation
studies
(results
presented
in
Section
3.1).
After
the
simulation
results
are
evaluated,
simulation studies (results presented in Section 3.1). After the simulation results are evaluated,
experimental
are shown
shown and
and discussed
discussed in
in Section
Section 3.2.
3.2.
experimental results
results are
3.1. Simulation Results
The load demand of a three-story office building located in Istanbul was used in the simulation
study.
On the
theday
dayofofmeasurement,
measurement,building
buildingrenovation
renovation
work
was
in progress.
Therefore,
some
of
study. On
work
was
in progress.
Therefore,
some
of the
the
electrical
loads
were
continuously
engaged
or
disengaged.
In
the
simulation
study,
these
power
electrical loads were continuously engaged or disengaged. In the simulation study, these power values
valuesused
were
as the
load demand
values
active
and power
reactivedrawn
powerfrom
drawn
from
GEV, as
were
asused
the load
demand
values for
activefor
and
reactive
GEV,
as shown
in
shown
inIn
Figure
order
show the results,
simulation
results,
a period
of 10 s was
the
Figure 9.
order9.toIn
show
thetosimulation
a period
of 10
s was selected
whenselected
the loadwhen
demand
load at
demand
was at the maximum.
was
the maximum.
Figure
Figure 9.
9. The
The load
load demand
demand values
values and
and power
power values
values drawn
drawn from
from the
the GEV.
GEV.
The load demand and the power values drawn from the GEV coincide with each other
The load demand and the power values drawn from the GEV coincide with each other successfully.
successfully. An abrupt change was observed at the time of an instant power change due to the
An abrupt change was observed at the time of an instant power change due to the instantaneous
instantaneous response of the mathematical operations performed in the simulation study.
response of the mathematical operations performed in the simulation study. Eventually, proper
Eventually, proper functioning of the prepared load model and accuracy of the control of the
functioning of the prepared load model and accuracy of the control of the converters can be observed
converters can be observed from Figure 9.
from Figure 9.
It is necessary to maintain the DC bus voltage at the reference voltage value for maintaining the
RMS value of the terminal voltage of the load model the same as the power grid. The mentioned DC
bus voltage variation is presented in Figure 10. As seen, some fluctuations can be observed in DC
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2016, 9, 171
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15
It is necessary to maintain the DC bus voltage at the reference voltage value for maintaining
the
RMS value of the terminal voltage of the load model the same as the power grid. The mentioned DC
It is necessary
to maintain
the DC
bus voltage
the reference
voltage value
maintaining
the
bus voltage
variation
is presented
in Figure
10. Asatseen,
some fluctuations
can for
be observed
in DC
bus voltage
as the
load
powervoltage
demand
varies.
During
periods
of
lower
power
demand,
the DC
DC bus
RMS
value
of
the
terminal
of
the
load
model
the
same
as
the
power
grid.
The
mentioned
bus voltage as the load power demand varies. During periods of lower power demand, the DC bus
voltage
can
successfully
be
maintained
at
the
reference
voltage
value.
As
the
power
demand
increases,
bus voltage
variation isbe
presented
in Figure
10. As seen,
some
fluctuations
can be
observed
in DC
voltage
can successfully
maintained
at the reference
voltage
value.
As the power
demand
increases,
the fluctuations
of
the
DC
bus
voltage
increase
as
well.
However,
the
controller
keeps
the
mentioned
bus
voltage
as
the
load
power
demand
varies.
During
periods
of
lower
power
demand,
the
DC
bus
the fluctuations of the DC bus voltage increase as well. However, the controller keeps the mentioned
voltage
can
successfully
be
maintained
at
the
reference
voltage
value.
As
the
power
demand
increases,
fluctuations
within
acceptable
limits
and
therefore
ensures
the
successful
operation
of
the
system.
fluctuations within acceptable limits and therefore ensures the successful operation of the system.
the fluctuations of the DC bus voltage increase as well. However, the controller keeps the mentioned
fluctuations within acceptable limits and therefore ensures the successful operation of the system.
Figure 10. The voltage of the DC bus.
Figure 10. The voltage of the DC bus.
Figureof
10.the
Thepower
voltageunit
of the
bus. in Figure 11. The RMS value of
The terminal voltage fluctuations
areDC
shown
the voltage
at the
end offluctuations
load is maintained
to 220
V are
in spite
of high
power values
drawn
The
terminal
voltage
of theclose
power
unit
shown
in Figure
11. The
RMSfrom
value of
The terminal
voltagefluctuation
fluctuations
of the power
unit areand
shown
in Figure
11. voltage
The RMS
value of
the
battery.
This
voltage
is
within
the
standards
therefore
proper
regulation
the voltage at the end of load is maintained close to 220 V in spite of high power values drawn from
theprovided.
voltage at the end of load is maintained close to 220 V in spite of high power values drawn from
is
the battery.
This voltage fluctuation is within the standards and therefore proper voltage regulation
the battery. This voltage fluctuation is within the standards and therefore proper voltage regulation
is provided.
is provided.
Figure 11. The terminal voltage fluctuations of the power unit.
Figure 11. The
terminal
voltage
of the power
unit.drawn by the load in
Finally, the change
load
voltage
valuefluctuations
and the current
Figureof11.the
The
terminal
voltage
fluctuations
of thevariation
power unit.
Figure 12 show that the whole system is operating successfully. It is important to notice whether the
Finally,
the change
of acceptably
the load voltage
and
thedemand
current variations.
variation drawn
by the of
load
in
voltage
waveform
is kept
steadyvalue
during
load
The change
load
Finally,
change
ofwhole
the load
voltage
value successfully.
and the current
variation
by the the
load in
Figure 12the
show
that the
system
is operating
It is important
to drawn
notice whether
voltage
waveform
is kept
acceptably
duringsuccessfully.
load demand It
variations.
The change
of load
Figure
12 show
that the
whole
system steady
is operating
is important
to notice
whether
the voltage waveform is kept acceptably steady during load demand variations. The change of load
terminal voltage when the highest change of active load occurs in the eighth second, shown in Figure 12,
indicates the change of the current drawn by the load at the same time range. After the change of the
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10 of 15
11 of 17
terminal voltage when the highest change of active load occurs in the eighth second, shown in
10 of 15
Figure 12, indicates the change of the current drawn by the load at the same time range. After the
load values at the eighth second, the prepared system has been successfully adapted to this change
change of the load values at the eighth second, the prepared system has been successfully adapted to
terminal
voltage
when
highest
change of active load occurs in the eighth second, shown in
and has
continued
into
the the
current
study.
this change and has continued into the current study.
Figure 12, indicates the change of the current drawn by the load at the same time range. After the
change of the load values at the eighth second, the prepared system has been successfully adapted to
this change and has continued into the current study.
Energies 2016, 9, 171
Figure 12. The waveform of the terminal voltage of load model and load current.
Figure 12. The waveform of the terminal voltage of load model and load current.
Eventually, all units of the simulation system operate successfully, as claimed by the data obtained
Figure 12. The waveform of the terminal voltage of load model and load current.
from
all figures.
Theseofresults
show that the
GEVs
can successfully
be used
as an UPS
necessary.
Eventually,
all units
the simulation
system
operate
successfully,
as claimed
byifthe
data obtained
from all figures.
These
results
show
that thesystem
GEVsoperate
can successfully
used asby
anthe
UPS
if obtained
necessary.
Eventually,
all units
of the
simulation
successfully,be
as claimed
data
3.2. Experimental Results
from all figures. These results show that the GEVs can successfully be used as an UPS if necessary.
3.2. Experimental
Once theResults
simulation results validated the control algorithms and V2H operation mode, the test
3.2.
Experimental
Results
platform
was built
to support the obtained simulation results. At the beginning of the experimental
Once the simulation
results validated the control algorithms and V2H operation mode, the test
study, the grid voltage is within specified limits and the grid supplies the load in this process. At the
the simulation
results
validated simulation
the control algorithms
operation
the test
platform Once
was built
to support
the obtained
results. Atand
theV2H
beginning
ofmode,
the experimental
same time, the GEV is awaiting at full charge depending on the grid. After that, the time of the grid
was
built to
support
the obtained
simulation
results.
At the beginning
ofinthe
experimental
study,platform
the
grid
voltage
is
within
specified
limits
and
the
grid
supplies
the
load
this
process.
At the
voltage is decreasing outside of the specified limits is shown in Figure 13. The dSPACE unit receives
study,
the
grid
voltage
is
within
specified
limits
and
the
grid
supplies
the
load
in
this
process.
At
the
samethe
time,
GEV is
awaiting
full charge
on the
the time
of the
gridthe
voltage
and
current at
values
from thedepending
measurement
unitgrid.
at theAfter
grid that,
side and
ensures
the grid
same time, the GEV is awaiting at full charge depending on the grid. After that, the time of the grid
voltage
is
decreasing
outside
of
the
specified
limits
is
shown
in
Figure
13.
The
dSPACE
unit
receives
opening of the contactor through sending a signal to the islanding protection unit. The islanding
voltage is decreasing outside of the specified limits is shown in Figure 13. The dSPACE unit receives
the grid
voltagesignal,
and current
values from
theRMS
measurement
the grid
and ensures
the13.
opening
protection
the waveform,
and the
value of theunit
gridatvoltage
areside
illustrated
in Figure
the grid voltage and current values from the measurement unit at the grid side and ensures the
of theopening
contactor
through
sending
a
signal
to
the
islanding
protection
unit.
The
islanding
protection
of the contactor through sending a signal to the islanding protection unit. The islanding
signal,
the waveform,
and
the RMSand
value
thevalue
grid of
voltage
are
illustrated
in Figure
protection
signal, the
waveform,
the of
RMS
the grid
voltage
are illustrated
in 13.
Figure 13.
Figure 13. The waveform of the grid voltage when the power grid fails. (a) Grid voltage [V] (b) Grid
voltage [Vrms] (c) Islanding protection signal.
Figure 13. The waveform of the grid voltage when the power grid fails. (a) Grid voltage [V] (b) Grid
Figure 13. The waveform of the grid voltage when the power grid fails. (a) Grid voltage [V] (b) Grid
voltage [Vrms] (c) Islanding protection signal.
voltage [Vrms] (c) Islanding protection signal.
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The signal shown in Figure 13c is the control signal sent from dSPACE to the islanding protection
The signal shown in Figure 13c is the control signal sent from dSPACE to the islanding
unit. protection
The islanding
unit
is disabled
the control
signal
value
is 0.value
Thus,
the
energy
unit. protection
The islanding
protection
unitwhen
is disabled
when the
control
signal
is 0.
Thus,
the flow
from energy
the power
thepower
loads grid
is realized.
The islanding
unitprotection
is activated
and
mechanically
flowgrid
fromtothe
to the loads
is realized.protection
The islanding
unit
is activated
separates
loads and power
grid
from
thepower
moment
that the
control signal
is signal
1. Furthermore,
and mechanically
separates
loads
and
grid from
the moment
that thevalue
control
value is 1. the
RMS Furthermore,
value of gridthe
voltage
is reduced
zero after
a period
waveforms;
thisofsituation
is shown
RMS value
of gridtovoltage
is reduced
to of
zero
after a period
waveforms;
this in
situation
is main
shownreasons
in Figure
The main are
reasons
for measuring
this situation
are that the
Figure
13b. The
for 13b.
this situation
that the
equipment
canmeasuring
measure RMS
equipment
measure
values afterreduction
one periodisand
the displayed
is within
values
after onecan
period
andRMS
the displayed
within
a period reduction
of the power
grid.a period
of the
grid. of the experimental study, the waveform of the terminal voltage of the power
In
thepower
first stage
In the first stage of the experimental study, the waveform of the terminal voltage of the power
unit is shown in Figure 14a and the RMS value of voltage of the power unit is shown in Figure 14b.
unit is shown in Figure 14a and the RMS value of voltage of the power unit is shown in Figure 14b.
After the islanding protection unit is activated, GEV begins to supply loads after a short time. This
After the islanding protection unit is activated, GEV begins to supply loads after a short time.
situation
presented
in Figurein14c.
Approximately
one-period
delay is
set by
dSPACE
to secure
This is
situation
is presented
Figure
14c. Approximately
one-period
delay
is set
by dSPACE
to the
operating
status
of
the
test
platform,
which
was
expressed
previously
in
Section
2.
secure the operating status of the test platform, which was expressed previously in Section 2.
Figure 14. The waveform of the terminal voltage of the power unit when the power grid fails. (a) Terminal
Figure 14. The waveform of the terminal voltage of the power unit when the power grid fails.
voltage of the power unit [V] (b) Terminal voltage of the power unit [Vrms] (c) Islanding protection signal.
(a) Terminal voltage of the power unit [V] (b) Terminal voltage of the power unit [Vrms] (c) Islanding
protection signal.
Lastly, the change of the battery voltage is shown in Figure 15 at the time of the islanding protection
signal received. Initially, the fully charged battery is in standby mode until the islanding protection
process is performed. After the islanding protection process, the battery voltage remains at the same
value while the inverter is waiting for the provision of the necessary conditions for operation. When
the power unit starts, the battery supplies the load and the battery voltage value decreases slightly.
Figure 15. The change of the battery voltage when the power grid fails. (a) Battery voltage [V]
(b) Islanding protection signal.
Figure
14.9,The
Energies
2016,
171waveform of the terminal voltage of the power unit when the power grid fails. (a) Terminal
13 of 17
voltage of the power unit [V] (b) Terminal voltage of the power unit [Vrms] (c) Islanding protection signal.
Energies 2016, 9, 171
12 of 15
Lastly, the change of the battery voltage is shown in Figure 15 at the time of the islanding
protection signal received. Initially, the fully charged battery is in standby mode until the islanding
protection process is performed. After the islanding protection process, the battery voltage remains
at the same value while the inverter is waiting for the provision of the necessary conditions for
operation. When the power unit starts, the battery supplies the load and the battery voltage value
decreases slightly.
In the last stage of the experimental study, the response of the test platform is examined when
the power grid is powered up again. When the voltage value of the grid is within standard limits
again, the flow of energy from GEV to the load is terminated and load demand is satisfied by the
grid again. These situations are illustrated in Figures 16–18.
Figure 15.
15. The
The change
change of
ofthe
thebattery
battery voltagewhen
when thepower
power grid
fails.
Battery
voltage
Figure
fails.
(a)(a)
Battery
voltage
[V] [V]
(b)
The waveform
of the grid
voltagevoltage
and its RMSthe
value aregrid
shown
in
Figure
16a,b
respectively,
(b)
Islanding
protection
signal.
Islanding
protection
signal.
when the power grid is online again. As seen in Figure 16c, the value of the islanding protection
signal is 0 shortly after the grid voltage is within specified limits. Thus, the islanding protection unit
In the
last stage of
thethe
experimental
study,
response
of the
platform is of
examined
the
remains
inactivated
and
grid supplies
the the
loads.
Despite
the test
improvement
the gridwhen
voltage,
power
grid
powered
upprotection
again. When
theisvoltage
value
of the
grid istime.
within
standard
limitsfor
again,
the value
ofisthe
islanding
signal
zero again
after
a certain
The
main reason
this
the
flow
of
energy
from
GEV
to
the
load
is
terminated
and
load
demand
is
satisfied
by
the
grid
again.
is that dSPACE waits for the realization of the previously mentioned security requirements in
These
are safety
illustrated
in Figuresensure
16–18.the safe and effective operation of the whole system.
Sectionsituations
2.2.2. These
requirements
Figure 16. The waveform of the grid voltage when the power grid is powered up again. (a) Grid
Figure 16. The waveform of the grid voltage when the power grid is powered up again. (a) Grid
voltage [V] (b) Grid voltage [Vrms] (c) Islanding protection signal.
voltage [V] (b) Grid voltage [Vrms] (c) Islanding protection signal.
Figure 17 shows the change of the terminal voltage of the power unit and the islanding
protection signal when the power grid is online again. After receiving the information indicating
that the grid voltage is within specified limits, the operation of the power unit is terminated. Before
islanding operation is terminated, the RMS value of the output voltage of the power unit reaches
nearly zero in terms of security. Thus, the grid can be used to supply the load again. Lastly, the
change of the battery voltage is shown in Figure 18. Primarily, the grid voltage reaches the specified
limit. Then, dSPACE stops the operation of the power unit. From this moment on, the battery
voltage is restored to the initial values. After obtaining all the safety requirements, dSPACE
terminates the islanding protection.
The results of the experimental study show that all the units of the test platform perform
successfully under the normalized conditions. Consequently, GEVs can be used as a UPS if the
electrical infrastructure and power unit control are prepared properly.
Energies 2016, 9, 171
14 of 17
Energies 2016, 9, 171
Energies 2016, 9, 171
13 of 15
13 of 15
Figure
17. The
The waveform of
the terminal
voltage of
the power
unit when
the power
grid is
powered
Figure
Figure 17.
17. The waveform
waveform of
of the
the terminal
terminal voltage
voltage of
of the
the power
power unit
unit when
when the
the power
power grid
grid is
is powered
powered
up
again.
(a)
Terminal
voltage
of
the
power
unit
[V]
(b)
Terminal
voltage
of
the
power
unit
up
again. (a)
(a) Terminal
Terminal voltage
voltage of
of the
the power
power unit
unit [V]
[V] (b)
(b) Terminal
Terminal voltage
of the
the power
power unit
unit [Vrms]
[Vrms]
up again.
voltage of
[Vrms]
(c) Islanding
Islanding protection
protection signal.
signal.
(c)
(c) Islanding protection signal.
Figure 18. Change of the battery voltage when the power grid is powered up again.
Figure 18. Change of the battery voltage when the power grid is powered up again.
Figure
18. Change
voltage
when the
power grid is powered up again. (a) Battery voltage
(a)
Battery
voltage of
[V]the
(b)battery
Islanding
protection
signal.
(a) Battery voltage [V] (b) Islanding protection signal.
[V] (b) Islanding protection signal.
4. Conclusions
4. Conclusions
The waveform
of the
grid voltage
and have
its RMS
value
are shown
Figurewhich
16a,b respectively,
when
Recently,
a great
number
of studies
been
performed
oninGEVs,
are considered
to
Recently,
aisgreat
number
of studies
have been
performed
on
GEVs,
which
are considered
the
power
grid
online
again.
As
seen
in
Figure
16c,
the
value
of
the
islanding
protection
signal
isto
0
provide zero emissions. In these studies, it is declared that this GEV technology will gradually
provideafter
zerothe
emissions.
In these
studies,
it is declared
that the
thisislanding
GEV technology
will
gradually
shortly
grid
voltage
is
within
specified
limits.
Thus,
protection
unit
remains
become widespread in the near future. As it is well known, an energy storage unit that provides the
become widespread
in the
near future.
As it Despite
is well known,
an energy storage
unitvoltage,
that provides
the
inactivated
and the
supplies
the loads.
the improvement
the should
grid
the value
required
power
for agrid
vehicle
is employed
in GEVs. This
energy storageofunit
be recharged
at
required
power for
a vehicle
is employed
in GEVs.
energy
storage
should
befor
recharged
at
of
the islanding
signal
is zero
afterThis
certain
The unit
main
reason
this can
is that
charging
points. protection
Also, another
reason
foragain
this type
ofa GEV
to time.
be popular
is that
the vehicle
be
charging
points.
Also,
another
reason
for
this
type
of
GEV
to
be
popular
is
that
the
vehicle
can
be
dSPACE waits
forgrid.
the realization
of the
the interaction
previously mentioned
security
requirements
in Section
connected
to the
Nowadays,
of GEV with
the grid
is bi-directional,
as is2.2.2.
the
connected
torequirements
the grid. Nowadays,
the
interaction
of GEV
with the
grid
is bi-directional,
as is the
These
safety
ensure
the
safe
and
effective
operation
of
the
whole
system.
charging process. However, GEVs can be operated bi-directionally by modifying the design of a
charging
process.
However,
GEVs
can
be operated
bi-directionally
by modifying
the design
of a
Figure
17 shows
change
the
terminal
voltage
of the power
the islanding
vehicle’s
power
unit the
or units.
Inofsuch
operating
condition,
a GEVunit
can and
be operated
as aprotection
UPS and
vehicle’s
power
unit
or
units.
In
such
operating
condition,
a
GEV
can
be
operated
as
a
UPS
and
signal when
the power
gridofisthe
online
again. After
receiving the information indicating that the grid
supply
the energy
demand
consumption
center.
supply the energy demand of the consumption center.
Before starting the study, it was assumed that battery of a GEV can supply a portion of an
Before starting the study, it was assumed that battery of a GEV can supply a portion of an
end-user premise’s load. The test system was prepared primarily in a simulation environment for
end-user premise’s load. The test system was prepared primarily in a simulation environment for
Energies 2016, 9, 171
15 of 17
voltage is within specified limits, the operation of the power unit is terminated. Before islanding
operation is terminated, the RMS value of the output voltage of the power unit reaches nearly zero in
terms of security. Thus, the grid can be used to supply the load again. Lastly, the change of the battery
voltage is shown in Figure 18. Primarily, the grid voltage reaches the specified limit. Then, dSPACE
stops the operation of the power unit. From this moment on, the battery voltage is restored to the
initial values. After obtaining all the safety requirements, dSPACE terminates the islanding protection.
The results of the experimental study show that all the units of the test platform perform
successfully under the normalized conditions. Consequently, GEVs can be used as a UPS if the
electrical infrastructure and power unit control are prepared properly.
4. Conclusions
Recently, a great number of studies have been performed on GEVs, which are considered to
provide zero emissions. In these studies, it is declared that this GEV technology will gradually become
widespread in the near future. As it is well known, an energy storage unit that provides the required
power for a vehicle is employed in GEVs. This energy storage unit should be recharged at charging
points. Also, another reason for this type of GEV to be popular is that the vehicle can be connected to
the grid. Nowadays, the interaction of GEV with the grid is bi-directional, as is the charging process.
However, GEVs can be operated bi-directionally by modifying the design of a vehicle’s power unit or
units. In such operating condition, a GEV can be operated as a UPS and supply the energy demand of
the consumption center.
Before starting the study, it was assumed that battery of a GEV can supply a portion of an end-user
premise’s load. The test system was prepared primarily in a simulation environment for testing and
improving the accuracy of the planned system and algorithm and the system was tested with the real
measured power data of a building. The voltage, frequency, etc., values remained within standards and
the building could be supplied with high-quality energy. The results of the simulation study showed
that the proposed test system can be used successfully in daily life as a UPS.
Afterwards, the test platform was established to present the verification of the controller system
design and to implement a successful vehicle–home connection. The experimental results showed
that the established test platform performed successfully under normalized conditions and can be
practically implemented. The activation and deactivation of the power unit and islanding protection
unit were realized in as rapid (approximately two cycles) and safe a way as possible when energy was
interrupted on the test platform.
To this end, it should be noted that the idea of the V2H operating conditions has been confirmed
by successful simulation and experimental studies. It is expected that the developed test platform can
also be adapted to any GEV and end-user type, thus enabling GEVs to be employed for other purposes
apart from transportation. In addition, this concept can also be used in different situations, such as
emergency disasters such as earthquakes and blackouts.
Acknowledgments: This work was supported in part by the Istanbul Chamber of Industry research projects
fund. Besides, this work was supported by FEDER funds through COMPETE and by Portuguese funds through
FCT, under FCOMP-01-0124-FEDER-020282 (Ref. PTDC/EEA-EEL/118519/2010), UID/CEC/50021/2013 and
SFRH/BPD/103744/2014. Also, the research leading to these results has received funding from the EU Seventh
Framework Programme FP7/2007-2013 under grant agreement no. 309048 (project SiNGULAR).
Author Contributions: Gorkem Sen and Ali Rifat Boynuegri mainly contributed by realizing the simulation and
experimental analyses. Besides, all co-authors contributed by significant technical suggestions and improvements
through the research steps and also contributed to the writing of the final research paper.
Conflicts of Interest: The authors declare no conflict of interest.
Abbreviations
The following abbreviations are used in this manuscript:
CV
conventional vehicle
Energies 2016, 9, 171
EPRI
GEV
GHG
ORNL
PEV
PHEV
PNNL
SoC
UPS
V2H
16 of 17
Electric Power Research Institute
grid-enabled vehicle
greenhouse gas
Oak Ridge National Laboratory
plug-in electric vehicle
plug-in hybrid electric vehicle
Pacific Northwest National Laboratory
state of charge
uninterruptible power supply
vehicle-to-home
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