 Open Access
 Total Downloads : 343
 Authors : Bhogapurapu Gayatri Subhadra, Srungarapu Naga Venkata Ganesh
 Paper ID : IJERTV5IS020014
 Volume & Issue : Volume 05, Issue 02 (February 2016)
 DOI : http://dx.doi.org/10.17577/IJERTV5IS020014
 Published (First Online): 01022016
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Modelling and Analysis of SEPIC using DVR for Solar PV System
Dr. S. N. V. Ganesh B. Gayatri Subhadra
Head of the Department Power Electronics Division Sri Sivani College of Engineering Sri Sivani College of Engineering
Chilakapalem Chilakapalem
Srikakulam (Dist.),India Srikakulam (Dist.),India
Abstract: Dynamic Voltage Restorer (DVR) is a series controller which has capability to control voltage profile at the load end under all operating conditions. The device is mainly used in distribution system with low and medium voltages. The controller has now much importance (due to its capability in maintaining power quality) as most of the loads are becoming very sensitive to power quality events like voltage sags, swells etc. However energy storage requirement has put limitations on high power rating of DVR. This project tries to find a solution to energy storage limitations: renewable sources. The project proposes modelling of PV array, Single Ended Primary Inductive Coil (SEPIC)/Boost converter for mitigating voltage disturbances using DVR. Performance of DVR will be investigated using motor load.
Keywords: Solar Photovoltaic, SEPIC, Power Quality, DVR

INTRODUCTION:
Now a days electrical energy plays a major role in day to day life of humans. For giving the supply voltage to DVR, in this project renewable energy sources are used. In this project Solar
represented by a current source connected parallel with diode as shown in Fig. 1.
Fig 1: Electrical Model of a PV cell
By writing the equation for the PV circuit using the Kirchhoffs current law for current is,
Energy is used as a source of energy for supplying the supply
=
……………(1)
voltage to DVR. In this solar energy is converted into electrical energy. From the Photo Voltaic array we can get low voltage, so we have to increase this voltage. For this purpose Single Ended Primary Inductor Converter (SEPIC) is used in this project. SEPIC converter can acts as both Buck converter and Boost converter. It has a switching device MOSFET, by adjusting the
gating signals of MOSFET we can get the desired output
Where, is the light generated current in the cell
is the voltage dependent current lost to recombination
is the current lost due to shunt resistance The diode model equation is represented as,
V IRS
voltage. For the purpose of controlling PI controller is used in
ID I 0 exp
nV 1
…………..(2)
this converter. The output of the SEPIC converter is given to the DVR as input. When there is any voltage sags or swells the DVR injects the missing voltage. By connecting different loads we can find out the performance of the DVR. This work is done in MATLAB/SIMULINK.

PHOTO VOLTAIC SYSTEM:
The SolarPV cells are used to produce electricity by directly converting solar energy to electrical energy. Each solar cell is basically a p n diode. As
T
Where, n is the diode ideality factor
I0 is the diode saturation current
VT is the thermal voltage
Now, the equation for the PV module is expressed as,
m m S S m m S S
m m S S m m S S
V I N R V I N R
Im I L Io exp 1
sunlight strikes a solar cell, the incident energy is converted directly into electrical energy without any
nN
SVT
NS Rp
mechanical effort. The voltage and current levels are produced from PV cells are very less, thus these PV cells are connected in series and parallel called modules and arrays to produce required voltage and current levels. The solar PV array is modelled by considering the output characteristics of PV panel which directly have relation with power converters which exists in the system. The solar PV cell is a non linear device which can be
Where, NS is the identical number of series cells
Vm is the module voltage and Im is the module current
The equation (3) is simulated using MATLAB/Simulink and PV and IV characteristics are obtained. The operating curves shows that solar PV output power is function of solar irradiation. Fig. 2 shows I V and PV
characteristics of a one PV module. The specification of a solar PV module for grid connected solar PV system is given in Table I.
Design of SEPIC converter:
For closed loop simulation we go for state space transfer function. For SEPIC the input to output relationship and associated signal state relationship can be represented as,
VOUT
Vin
D
(1 D)
D2V
I L1
in
(1 D)2 R
V V L
I L2
C1 in
D Vin
(1 D) RL
VC 2
D Vin
(1 D)
Fig 2: PV and IV characteristics
Now, duty cycle to output relationship can be expressed as,
Where,
V X S 3 X S 2 X S X
6
6
7
7
out (S ) 1 2 3 4 *Vin
Parameters
Values
Irradiation
1000W/m2
Short circuit current
5.45A
Open circuit voltage
22.2V
Current at Pmax
4.95A
Voltage at Pmax
18V
Parameters
Values
Irradiation
1000W/m2
Short circuit current
5.45A
Open circuit voltage
22.2V
Current at Pmax
4.95A
Voltage at Pmax
18V
D X 5
S 4 X
S 3 X
S 2 X
8 S X 9
..(4)
1
1
X L1C1L2D 1.4557 *1011
X 2 L1C1RL
D2 7.3062 *1011
Table 1: Parameters of the PV system

SEPIC:
5
5
L
L
It is a converter which can converts the DC voltage from one level to another level that means it can
X D2 L1 3.645*103
3
3
4
4
X D2 R 21.573
stepup or stepdown the output voltage by varying the Duty cycle of the MOSFET. It has advantages like low component stresses, low energy storage requirements,
X (1 D)2 L1C1L2R
7.9128*1015
compact in size and the efficiency also high compared to BuckBoost converter. The circuit diagram of SEPIC is shown in fig.2;
L11
L11
C1
X (1 D)2 L1C1L2 3.966 *103
6
6
X 7 (1 D)2 RL[L1C1(1 D)2 L2C2(1 D)2 L2C1(1 D)2 L1C2D2]
8
8
9
9
L
L
DC Voltage Source
m
S
m
S
g
D
g
D
Mosfet
Diode
R
L2 C2
X (1 D)2 [L2(1 D)2 L1D2 ] 8.6923*105
Terminator
X (1 D)4 R
0.01601
Fig .3. Circuit diagram of the SEPIC converter
V out (S)
V
Y S 2 Y
1 2
1 2
Y S 4 Y S 3 Y S 2 Y S Y
………(5)
in 3 4 5 6 7
Where,
Y1 L2C1RL
(1 D) 1.5443*108
cost will depends on the power rating and other equipments.
Y2 D(1 D)
RL 3.8668
DVR works independently on the type of fault or any event that happens in the syste, provided that the total
Y3 L1C1L2C2RL
3.4249 *1013
system is remains constant and it is connected to the supply grid i.e., the line circuit breaker does not trip. For
4
4
Y L1C1L2 1.7167 *1011
L
L
5
5
Y R [L1C1(1 D)2 L2C2(1 D)2 L2C1(1 D)2 L1C2D2 ]
7.5061*105
most practical cases, a more economical design can be achieved by only compensating the positive and negative sequence components of the voltage disturbances seen at the input of the DVR. Because of infinite impedance the zero sequence component does not pass through the step down transformer.The injected voltage of the DVR can be
6
6
Y L1D2 L2(1 D)2 3.7622 *103
expressed as,
V
V V
…………..(8)
Y R (1 D)2 0.69312
inj
La Sa
L
L
By substi7tutingLthe L1, L2, C1, C2, R and D values we can get that input to output relationship,
Where,
VLa is the desired load voltage magnitude
Vout
1.5443*108S 2 3.8668
VSa is the source voltage during disturbance
(S)
Vin 3.4249*103S 4 1.7167*1011S3 7.506*105S 2 3.7622*103S 0.69312
The load current ILa is given by,
…(6)
PLa QLa
V
V
I
I
La
La
…………..(9)
By using the above transfer function we can get the desired output voltage.

SIMULATION AND RESULTS
The simulation circuit shown in below fig.3. Comprises of system with 3phase programmable voltage source with an A.C voltage of 440V, 50Hz. Here, asynchronous machine is placed as a load replacing with the resistive load. Here, the fault is placed in the 3phase programmable source with a time period of 0.3 to 0.4 in the total simulation time (0.5).
Element
Value
Supply Voltage
107V
Inductor, L1
5.069mH
Inductor, L2
5.069mH
Capacitor, C1
668.13pF
Capacitor, C2
665ÂµF
Diode Voltage drop, VD
0.8V
Resistance, R
33.33
Buck Output Voltage
52V
Boost Output Voltage
602V
Element
Value
Supply Voltage
107V
Inductor, L1
5.069mH
Inductor, L2
5.069mH
Capacitor, C1
668.13pF
Capacitor, C2
665ÂµF
Diode Voltage drop, VD
0.8V
Resistance, R
33.33
Buck Output Voltage
52V
Boost Output Voltage
602V
A Vabc
A Iabc
N B B a
b
b
C C c

Vabc Tm
Iabc A

a m
b B

c C

Table 2: SEPIC elements and its values


DYNAMIC VOLTAGE RESTORER:
DVR is a series controller which is used to compensate voltage sags and swells. DVR is used for short time faults
PV array
Continuous
Continuous
A B C
A B C
powergui
ThreePhase Programmable Voltage Source
g
+
+
+
A A A
s
–
s
–
C V S B B B
– C C

Vabc Iabc

a
A1+ A1 B1+ B1 C 1+ C1
A1+ A1 B1+ B1 C 1+ C1
Gain2
A2+ A2 B2+ B2 C 2+ C2
A2+ A2 B2+ B2 C 2+ C2
K
Vabc
PQ
Iabc
Scope5
Asynchronous Machine pu Units
only. DVR injects the voltage in phase to the supply. So,
num(s)
V
1.2

b
C c
Discrete
3phase
Instantaneous
that it can maintain a good power quality profile at the
den(s)
SEPIC
Gain1
PWM Generator Active & Reactive Power1
A B C
A B C
Unit Delay
load. DVR contains a Voltage Source Converter (VSC), an Energy Storage System, an Injection Transformer and a LCFilter. In this VSC will convert the DC into AC and by this converting process it will produce some
harmonics. To reduce these harmonics we use an LC
PV Array
Scope7
Scope1
node 10 node 10
Vabc (pu) Sin_Cos
node 10
1
Pulses Uref
z
Gain
K
A B C
A B C
Vabc Iabc
Scope3
PQ
Scope4
Filter and it doesnt allow harmonics across it. Filter is connected in between the VSC and Injection
Discrete
3phase PLL1
Scope2
dq0
3phase Instantaneous
Active & Reactive Power
Transformer. Injection Transformer will inject the voltage in series with the supply lines. Depending on the
A A Vabc
a
N B B
b
C C c
abc
sin_cos
dq0
abc
abc
sin_cos
K
Vabc
PQ
compensation the storage of energy will be stored and for energy storage capacitors and batteries are used. In this
ThreePhase Programmable Voltage Source1
sin_cos
dq0
Gain3
Iabc
3phase Instantaneous
Scope6
DVR we use fast switches, due to these fast switching
operations we can get the desired output. By using fast switches the cost of the DVR will increases and the DVR
Active & Reactive Power2
Fig.4. Simulink model of the system with motor load
Source Voltage
Voltage in pu
Voltage in pu
1
0
1
0 0.1 0.2 0.3 0.4 0.5
Voltage in pu
Voltage in pu
Load Voltage
1
0
1
0 0.1 0.2 0.3 0.4 0.5
DVR injected Voltage
Voltage in pu
Voltage in pu
0.5
0
0.5
0 0.1 0.2 0.3 0.4 0.5
Time (secs)
Fig .5. Output waveform of system with motor load in sag condition
VII. REFERENCES

Binod Kumar Padhi and Anirudha Narain, Controller Design For SEPIC Converter Using Model Order Reduction ASAR International Conference, Bangalore Chapter 2013, ISBN: 9788192714707.

R. W. Erickson and D. Makdimovic, Fundamental of Power Electronics, 2nd ed., Kluwer Academic Publishers, 2001.

Anwar Sahbela, Naggar Hassanb, Magdy M. Abdelhameedb, Abdelhalim Zekryb Experimental Performance Characterization of Photovoltaic Modules Using DAQ TerraGreen 13 International Conference 2013 – Advancements in Renewable Energy and Clean Environment.

Godsk Nielsen Design and Control of a Dynamic Voltage Restorer by John Copyright c 2002, ISBN: 8789179420.

A. P. Torres1, P. RonceroSanchez2, Design and Comparison of Two Control Strategies for Voltagesag Compensation using Dynamic Voltage Restorers BY X.del Toro Garcia2, V. Feliu2. http://dx.doi.org/10.5755/j01.eee.19.6.4553.

M. Ramasamya*, S. Thangavelb Photovoltaic Based Dynamic
4
x 10
15
Power (W)
Power (W)
10
Source Power
Voltage Restorer with Outage Handling Capability Using PI Controller BY Â© 2011 Published by Elsevier Ltd.
5
0
5
0 0.1 0.2 0.3 0.4 0.5
4
4
x 10 Load Power
15
Power (W)
Power (W)
10
5
0
5
0 0.1 0.2 0.3 0.4 0.5
Time (secs)
Fig.6. Output power waveform of system with motor load in sag condition.
VI. CONCLUSION
In this project SEPIC modeling is presented briely. The open loop and closed loop simulations are presented. A DC 600V output is obtained from only 107V as input. It is observed by varying duty cycle and output also changes, duty cycle above 50% it operate as a boost converter and below 50% it act like a buck converter. A current input PV model is developed using Matlab/Simulink in modeling. By this model the IV and PV characteristics are obtained.
The project proposes modeling of PV array, Single Ended Primary Inductive Coil (SEPIC)/Boost converter for mitigating voltage disturbances using DVR. Performance of DVR was investigated.