SSRG International Journal of Electrical and Electronics Engineering (SSRG-IJEEE) – volume 3 Issue 5 May 2016
Integration of Transformer-less PV-FC system
with Reduced Leakage Current
Ramu Venkata Nagaraju1, SK Neelofar2
1pursuing M.Tech (EEE), 2working as Assistant Professor (EEE),
Nalanda Institute Of Engineering and Technology (NIET)Kantepudi(V), Sattenpalli(M), Guntur (D)522438,Andhra Pradesh.
Abstract- This letter presents a modulation
technique for the modified coupled-inductor singlestage boost inverter (CL-SSBI) based grid-connected
PV-FC system. The integration two systems which
improve voltage gain behaviour and can reduce the
system leakage current in a great deal and can meet
the VDE0126-1-1 standard. To maintain the
advantages of the impedance network, only a diode
is added in the front of the original topology, to
block the leakage current loop during the active
vectors and open-zero vectors. On the other hand,
the near state pulse width modulation (NSPWM)
technique is applied with one-leg shoot-through zero
vectors in order to reduce the leakage current
through the conduction path in the duration of
changing from and to open-zero vectors.
Simultaneously, the leakage current caused by other
transitions can also be reduced due to the fact that
the magnitude of common-mode voltages is reduced.
Simulation results of the transformer less Integration
of PV-FC system are presented in two cases:
modified CL-SSBI modulated by maximum constant
boost (MCB) control method and NSPWM.
Experimental results for both CLSSBI topology
modulated by the MCB control method and modified
CL-SSBI topology modulated by NSPWM are also
obtained to verify the accurateness of theoretical
and simulation models.
Keywords — Leakage current, photovoltaic (PV),
Fuel energy power system, shoot-through zero
vector, single-stage boost inverter, width modulation.
I. INTRODUCTION
The transformer less photovoltaic (PV)
power framework has been drawing in more
consideration for its lower cost, littler volume, and
also higher proficiency, contrasted with the ones
with transformer[1][5]. One of the specialized
difficulties is the wellbeing issue of the spillage
current brought on by the normal mode voltages
(CMV), leading on the up and up with parasitic
capacitors between the suns based board and the
ground.
For single stage help inverter transformer
less PV frameworks, for example, the Z-source
ISSN: 2348 – 8379
inverter[7]-based frameworks, the tweak procedure
is deliberately intended to keep up the steady CMV
to diminish the spillage current. In any case, the
OPWM or EPWM strategy utilizes just odd or even
dynamic vectors to integrate the yield reference
voltage, prompting just 57.7% of the greatest extent
contrasted with SVPWM, furthermore to exacerbate
consonant contortion of the yield waveforms.
A coupled inductor single-stage support
inverter (CL-SSBI) is [16] proposed in which
presented an impedance system, incorporating
coupled inductor in the front-end of the inverter
extension. The structure is straightforward, while
LCD can be seen as a snubber.
The converter uses shoot-through zero
vectors [17] to store and exchange vitality inside of
the novel impedance system, to venture up the
transport voltage. Turns proportion of the coupled
inductor inside of the impedance system can
likewise be intended to enhance the help pick up. So
the air conditioner yield voltage can be managed in a
wide range and can be ventured up to a higher worth.
Higher force misfortune and lower
productivity would be unavoidable if higher support
addition is required, which is the drawback of
inverters of this sort. As shoot-through zero vectors
uniformly disseminated among the three stage legs
amid an exchanging period [17], the equal changing
recurrence saw from the impedance system can be
six times the exchanging recurrence of the inverter
scaffold, which will incredibly lessen the force
thickness and expense of the inverter.
This letter shows the technique to lessen the
spillage current of the transformer less framework
associated PV framework taking into account
CLSSBI. A diode is included the front of the
topology to obstruct the spillage current circle when
in the dynamic vectors and open-zero vectors.
What's more, the close state PWM
(NSPWM) strategy is utilized with one-leg shoot-
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SSRG International Journal of Electrical and Electronics Engineering (SSRG-IJEEE) – volume 3 Issue 5 May 2016
through zero vectors to decrease the spillage current
created in the transient conditions of changing from
and to open-zero vectors.
What's more, the spillage current brought
about by different moves can likewise be decreased
because of the way that the greatness of CMVs is
diminished. Note that the spillage current can be
decreased successfully without bringing down the
most extreme extent of the yield reference voltage,
for the balance record of NSPWM stays in the high
adjustment segment.
Proposed Transformer less Grid
Connected PV System Based On CLSSBI
The modified CL-SSBI is shown in Fig. 1.
Only a diode is added in the front of the topology
compared to the original structure, to block the
leakage current loop during the active vectors and
open-zero vectors, of which the CMVvCM [4]
2B
0
0
-
(1-
0
0
III.PROPOSED SIMULINK SYSTEM
The proposed model implements the
modulation technique for the modified coupledinductor single-stage boost inverter (CL-SSBI)based grid-connected photovoltaic fuel cell (PV-FC)
system. This technique can reduce the system
leakage current in a great deal and can meet the
required voltage levels the advantages of the
impedance network.
And it consists of one converter (3 phase
inverter), and a coupled inductor with capacitors and
diodes. the presence of diode at the front and of
voltage source inverter reduces the leakage currents
and protect the VSI from the leakage currents and
also reduce the stress on switches of VSI and the
presence of capacitors and inductors reduces the
ripples in voltage and current wave forms
respectively .
The
developed
Simulink
model
representing the Transformer-less grid-connected
PVFC system based on CL-SSBI with an additional
diode with SVPWM controlling strategy is shown in
following figure 2.
PV cell:
Fig. 1. Transformer-less grid-connected PV
system based on CL-SSBI with an
additional diode.
Space
Vectors
5-N/6N
5-N/6N
0
0
3-N/2N
3-N/2N
0
0
6N-(5-N)B/6N
2N-
Space
Vectors
2B
ISSN: 2348 – 8379
-
(1-2B/3)
Photovoltaic (PV) is the name of a technique
for changing over sun based vitality into direct
current power utilizing semiconducting materials
that display the photovoltaic impact, a wonder
normally
examined
in
material
science,
photochemistry
and
electrochemistry.
A
photovoltaic system employs sun oriented boards
made out of various sunlight based cells to supply
usable sun based force
The procedure is both physical and
substance in nature, as the first step includes the
photoelectric impact from which a second
electrochemical procedure happen including
solidified iotas being ionized in an arrangement,
creating an electric current.
Power era from sun oriented PV has long
been seen as a clean sustainable vitality innovation
which draws upon the planet’s most abundant and
broadly circulated renewable vitality source – the
sun.
The immediate transformation of daylight
to power happens with no moving parts or natural
outflows amid operation. It is well demonstrated, as
photovoltaic frameworks have now been utilized for
a long time as a part of particular applications, and
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SSRG International Journal of Electrical and Electronics Engineering (SSRG-IJEEE) – volume 3 Issue 5 May 2016
lattice joined PV frameworks have been being used
for more than a quarter century.
A circuit based simulation model for a pv
cell for estimating the IV characteristics curves of
photovoltaic panel with respect to changes on
environmental
parameters (temperature and
irradiance) and cell parameters ( parasitic resistance
and ideality factor)
The output from PV cell is low voltage and
high current dc .is shown in fig 3.The output current
is high and voltages are low so we use the controlled
current source as input by using resistance and
capacitors we can improve current and voltage
because resistor oppose the flow of current and
capacitor improve the voltage some improved
voltage Vpv and current Ipv are produced as shown
in fig.4
Fig.4. PV array model
Fig.2. Simulink model for proposed PV-FC
system
Fig.3. PV internal diagram System
ISSN: 2348 – 8379
Fuel Cell:
An energy unit is an electrochemical cell
that changes over a source fuel into an electric
current. It creates power inside a cell through
responses between a fuel also, an oxidant, activated
near an electrolyte. The simulation model is given in
below figure5.
The reactants stream into the cell, and the
response items stream out of it, whiles the
electrolyte stays inside of it. Energy units can work
consistently for whatever length of time that the
fundamental reactant and oxidant streams are kept
up. The 72- cell system generated 50V with the help
of flow rate controller.
Fig 5: fuel cell based Simulink model
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SSRG International Journal of Electrical and Electronics Engineering (SSRG-IJEEE) – volume 3 Issue 5 May 2016
The integration of two systems we can
achieve effective ripple elimination and we can
improve the voltage levels this are transferred to
single stage boost three phase converter.
In the boost converter mechanism we have
the parameters like as diodes inductances and
capacitances to improve the voltage levels from the
input system. Which can regulate the leakage
currents from the diodes and also maintained the
voltage levels from the capacitances by the
inductances we can control the current ripples.
Controlling strategy:
In this topology we use the SVPWM
generator technology to generate the pulses required
for switching the IGBT in inverter circuit. The
developed Simulink model for SVPWM is shown in
figure given below
Fig.8.Generated voltages from pv array
Fig.6. Simulink model for SVPWM technique
In svpwm technique we will generate the
pulses by performing the relational operation
between the carrier signal and reference signal in
this method our reference signal is sinusoidal and
carrier signal is triangular which can be obtained by
using repetitive signal.
Fig.9.Generated voltages from FC
The internal diagram of control signal
consists of three sinusoidal signal by with the phase
difference of 120. We can generate the control signal
as shown in fig.7. Mentioned below.
Fig.7.simulink model for internal diagram of
space vector pwm
Fig 10.Dc voltage across the capacitor and
current through capacitor
There is chance of getting short circuit if
both switches are switched on at a time so for
generating alternate signals we use the not gate as
shown in fig 6.
ISSN: 2348 – 8379
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SSRG International Journal of Electrical and Electronics Engineering (SSRG-IJEEE) – volume 3 Issue 5 May 2016
The leakage current caused in the transient
states of changing from and to shoot-through zero
vectors is also reduced by using the SVPWM
technique with one-leg shoot-through zero vectors,
when open-zero vectors are omitted.
The CMVs and the caused leakage currents
are compared between CL-SSBI with MCB control
and CL-SSBID with NSPWM.
According to the simulation and
experimental results, the amplitude and RMS value
of the leakage current can be well below the
threshold level required by the VDE0126-11standards, indicating an effective leakage current
reduction.
REFERENCES
Fig.11.Generated voltage and current
across the load
The generated dc voltage which is fed back
to the inverter. The inverter consisting of six IGBTs.
TYPE
GRI
D
CUR
REN
TS
CMV
VOLT
AGE
LEKA
GE
CURR
ENT
Dc bus
Voltag
e
Existing
Technique
Proposed
Technique
2.5
A
2A
120V
0.06A
400V
100V
0.049
A
400V
Table: Grid currents, CMV voltages & leakage
currents for existed controller and proposed
controller
Which are used to convert the dc voltages
into required ac module applications. The inverter is
controlled by the SVPWM technique by the sine
wave signal with triangular signals, finally the pulses
are given to the inverter it generates ac power. Here
filter parameters also utilized to reduce the ripple
contents in the ac power. Finally it can maintain
purified ac power from the inverter.
IV. CONCLUSION
This paper has presented a transformer less
grid-connected PVFC system based on a coupled
inductor single-stage boost three phase inverter.
Due to the presence of Diode D4 at the front
of the topology together with D1, the flow of leakage
currents during the active vectors and open-zero
vectors.
The magnitude of common mode voltage is
reduced so the leakage currents caused by other
transition also reduced.
ISSN: 2348 – 8379
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ISSN: 2348 – 8379
AUTHOR DETAILS:
Ramu Venkata Nagaraju pursuing
M.Tech (EEE) from Nalanda Institute
of Technology and sciences (NIT),
Kantepudi(V),
Sattenpalli(M),
Guntur (D)-522438,Andhra Pradesh.
Shaik Neelofar working as Assistant
Professor (EEE) from Nalanda
Institute
of
Engineering
&
Technology (NIET),Kantepudi(V),
Sattenpalli
(M),
Guntur
(D)522438,Andhra Pradesh.
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