IRJET- Analysis of Open Loop Distribution Static Compensator for Improving Power Quality

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 07 Issue: 02 | Feb 2020 www.irjet.net p-ISSN: 2395-0072
© 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 317
Analysis of Open Loop Distribution Static Compensator for Improving
Power Quality
Rinkesh G. Satpute1, Yashashri B. Deshmukh2, Poonam A. Shende3 Suryakant B. Morey4
1,2,3,4Assistant Professor, Dept. of Electrical Engineering, DMIETR, Wardha, Maharashtra, India.
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Abstract - This paper presents Distribution Static
Compensator (D-STATCOM) modeled in the MATLAB
SIMULINK toolbox for the mitigation of the power quality
issues in the distribution system. DSTATCOM is one of the
custom power device used in distribution system for power
conditioning. DSTATCOM is developed for the compensating
reactive power demanded by non-linear andunbalancedload.
Also power factor of the source is improved and the Total
Harmonic Distortion in the source currents is reduced.
DSTATCOM can correct voltage sag, swell, unbalance by
injecting the reactive current into the system. Instantaneous
reactive power theory is used for obtaining reference source
current for controlling DSTATCOM. The performance of the
DSTATCOM for unbalanced and nonlinear load is
demonstrated with the MATLAB simulation results.
Key Words: Distribution Static Compensator (D-
STATCOM); Power Quality; Battery energy storage
system (BESS); Total Harmonic Distortion (THD).
1. INTRODUCTION
Utility and customer-side disturbances result in terminal
voltage fluctuations,transients,andwaveformdistortionson
the electric grid. Just as flexible ac transmission systems
(FACTS) controllers permit to improve the reliability and
quality of transmission systems, thesedevicescanbeusedin
the distribution level with comparable benefits for bringing
solutions to a wide range of problems. In this sense, FACTS
based power electronic controllers for distribution systems,
namely custom power devices, are able to enhance the
reliability and quality of power that is delivered to
customers. A distribution static compensatororDSTATCOM
is a fast response, solid-state power controller that provides
flexible voltage control at the point of connection to the
utility distribution feeder for power quality (PQ)
improvements. The primary aims of a shunt compensator in
a distribution system are to cancel or suppress the effect of
poor load power factor such that the currentdrawnfrom the
source has a near unity power factor, the effect of harmonic
contents in loads such that current drawn from the sourceis
nearly sinusoidal, the dc offset in loads such that the current
drawn from the source has no offset,theeffectofunbalanced
loads such that the current drawn from the source is
balanced. It can exchange both active and reactive power
with the distribution system by varying the amplitude and
phase angle of the converter voltage with respect to the line
terminal voltage, if an energy storage system (ESS) is
included into the dc bus. The result is a controlled current
flow through the tie reactance between the DSTATCOM and
the distribution network. This enables the DSTATCOM to
mitigate voltage fluctuations and to correct the powerfactor
of weak distribution systems in instantaneous real-time.
This paper discusses the dynamic performance of a
DSTATCOM with ESS for improving the power quality of
distribution systems. Modelling approaches are proposed,
including a detailed modelling of the DSTATCOM.
1.1 Modeling of The STATCOM
A DSTATCOM consists of a three-phase voltage source
inverter shunt-connected to the distribution network by
means of a coupling transformer, as depicted in Fig. 1. Its
topology allows the device to generate a set of three almost
sinusoidal voltages at the fundamental frequency, with
controllable amplitude and phase angle. In general, the
DSTATCOM can be utilized for providing voltage regulation,
power factor correction, harmonics compensation and load
levelling. The addition of energy storage through an
appropriate interface to the power custom device leads to a
more flexible integrated controller. The ability of the
DSTATCOM/ESS of supplying effectively extra active power
allows expanding its compensating actions, reducing
transmission losses and enhancing the operation of the
electric grid. Various types of energy storage technologies
can be incorporated into the dc bus of the DSTATCOM,
namely superconducting magnetic energy storage (SMES),
super capacitors (SC), flywheels and battery energy storage
systems (BESS), among others.
However, lead-acid batteries offer a more economical
solution for applications in thedistributionlevel thatrequire
small devices for supplying power for short periods of time
and intermittently. Moreover, BESS can be directly added to
the dc bus of the inverter, thus avoiding the necessity of an
extra coupling interface and thus reducing investment costs
to illustrate the functioning of shunt compensator.
The use of power electronics based loads such as variable
speed drive, inverter-based air conditioning, distributed
generation and storage system, personal electronics and
electric vehicle has given rise in issue of power quality. This
Paper proposed a D-STATCOM for harmonic current
mitigation and power factor correction, which result due to
the use of non-linear loads in the modern EDN.

Fig -1: Block Diagram of D-STATCOM
Consider the three phase, four-wire (3p-4w) distribution
system shown in Figure. All the currents and voltages that
are indicated in this figure are instantaneous quantities.
Here a three-phase balanced supply (Vsa, Vsb, Vsc)isconnected
across a star (Y) connected load. The loads are such that the
load currents (ila, ilb, ilc) may not be balanced, may contain
harmonics and de offset. In addition, the power factor of the
load may be poor. One implicationofloadnot being balanced
in this system is that there may be zero-sequence current iNn
flowing in the 4th wire, i.e., in the path n-n as shown in
Figure 2.
Fig -2: Distribution system
The shunt compensator is represented by three
ideal current sources ila , ilb and ilc The point of common
coupling (PCC) is encircled in Figure7.3.The currentsources
are connected in Y with their neutral n' being connected to
the 4th wire. The purpose of the shunt compensator is to
inject currents in such a way that the source currents Isa, Isb
Isc) are harmonic free balanced sinusoids and their phase
angle with respect to the source voltages (Vsa Vsb Vsc) has a
desired value.
2. SYSTEM CONFIGURATION
A distribution feeder connected to unbalanced and
nonlinear load is shown in the below Fig. 3 Working
performance of the DSTATCOM using instantaneousreactive
power theory (IRP) is analyzed by the modelling system
shown in Fig.1 in MATLAB Simulink tool.
Fig -3: Distribution system with D-STATCOM
In the system diagram shown in above Fig. 3, Zs represents
total impedance of phase which includes Rs and Ls
represents source resistance and source inductance. The
nonlinear load is realized by connecting the three phase
dioderectifiertoaResistive-Inductiveload(R-L).Unbalanced
load is realized by connectingdifferent values of impedances
in three phases. Three phase voltage source converter (VSC)
act as the DSTATCOM which consist of the six insulated gate
bipolar transistor (IGBT) and anti-parallel diodes are
connected to each IGBT. DC side of the Voltage source
converter (VSC) consists of a capacitor which is used to
maintain constant voltage for the switching operation of the
IGBT switches. The DC capacitor is not used for any reactive
power compensation. Interfacinginductor,Lfisconnectedon
the AC sideof the voltage source converter forcompensating
high frequency components of the compensating currents.
Storage capacitor Cdc does not exchange any active power
between DSTATCOM and the load. Breakerisusedtoobserve
the performance of the DSTATCOMbeforecompensationand
after compensation (i.e. For connecting and removing
DSTATCOM to and from the system)

3. OPERATING MODE OF DSTATCOM
The DSTATCOM can be operated in two different modes as
follows:
1. Voltage regulations mode
2. Current regulation mode
The current regulation mode can be divided into
A. Reactive power compensation mode
B. Active power compensation mode
3.1 Reactive power compensations mode
The static synchronous compensator regulate voltage as it’s
connection point by controlling the amount of reactive
power that is absorbed from or injected into power system
through a voltage source converter. This mode is analyzed
by considering below three cases:
Case 1: When Vs = Vc
When source voltage Vs and voltage source converter [VSI]
voltage are in phase as well as same in magnitude then both
active and reactive power in the system is zero i.e. Q = 0 and
P = 0. This is represented by phasor diagram as shown
below:
Fig -4: Vs and Vc are in phase with equal magnitude
Case 2: When Vs <Vc
In this case, when source voltage is less than the voltage
source converter [VSC] voltage i.e. in phase but different in
magnitude then, the reactive power will inject by the
STATCOM from the system and active powerinthesystemis
zero i.e. Q = some value and P = 0. Therefore, it is also known
as capacitive mode, which is representedinphasorasshown
below
Fig -4: Vs< Vc are in phase with unequal magnitude
From the fig it shows that current lead the voltage drops by
90 degrees and also it leads 90 degrees by converter voltage
Case 3: When Vs >Vc
In this case, when source voltage is greater than the voltage
source converter [VSC] voltage i.e. in phase but different in
magnitude then, the reactive power absorbed by the
STATCOM to the line and active power in the system is zero
i.e. Q = some value and P = 0. Therefore, it is also known as
inductive mode, which is represented in phasor as shown
below
Fig -5: Vs> Vc are in phase with unequal magnitude
From the fig it shows that current lagthevoltagedropsby 90
degrees and also it lags 90 degrees by converter voltage
3.2 Active power compensations mode
The active power absorbed or injected by STATCOM is
depends upon the angle between source voltage andvoltage
source converter [VSI] voltage. This mode is analyzed by
considering below two cases
Case 1: When Vc < Vs
In this case, when the voltage source converter [VSI] voltage
i.e. Vc lags the source voltage i.e. Vs then, active as well as
reactive power it absorbedbytheSTATCOMfromthesystem
which is represented in below phasor
Fig -6: Vc<Vs with equal magnitude
Case 2: When Vc > Vs
In this case, when the voltage source converter [VSI] voltage
i.e. Vc leads the source voltage i.e. Vs then, active as well as
reactive power injected by the STATCOM from the system
which is represented in below phasor

Fig -7: Vc<Vs with unequal magnitude
4. SIMULATION RESULTS
The performance of the DSTATCOM for power quality
improvement in the distribution system is studied by
observing waveforms of the different parameters of the
system before compensation and after compensation.
A. Results before Compensation
It is observed that due to unbalanced and non-linear load,
source currents and load currents get unbalanced and some
distortion is present in their waveform. Also power factor of
the source is not unity, as voltage at PCC and sourcecurrents
are not in Phase with each other.
Fig. 8 shows the supply side voltage results of simulation
without connecting the DSTATCOM forstatic unbalanceload
Fig -8: Supply side Voltage (v)
Fig -9: Load side Voltage (V)
Fig. 9 shows the Load side voltage results of simulation
without connecting the DSTATCOM forstaticunbalanceload
Fig -10: Load side Current (A)
Fig. 10 shows the Load Side Current results of simulation
without connecting the DSTATCOM forstaticunbalanceload
As the non-linear load is the sources of Harmonics.
When the non -linear load is added in the load side, it
introduced harmonics in the system. When nonlinear load
added in the system the whole system becomesunstableand
the waveform of the voltage and current distracted. In this
paper Rectifier which is generally usedtoconvertACinto DC
considered as a non-linear load connected at the load side
which introduce harmonics in thesystem.PowerElectronics
devices is the source of Harmonics and same power
electronics device are used to mitigate the Harmonics.
Fig. 11 shows the Load Side Voltage results of simulation
after the connections of nonlinear load without connecting
the DSTATCOM
Fig -11: Supply side Voltage(V) after connection of Non
linear Load
Fig -12: Supply side Current (A) after connection of Non
linear Load

Fig. 12 shows the Load Side Current results of simulation
after the connections of nonlinear load without connecting
the DSTATCOM.
It is Observed that when any nonlinear loadconnectedinthe
system then all system becomes unstable and harmonics is
introduced in the system. Now Distribution Static
Compensator is device which is used to improve Quality of
power which means it make distorted waveform intopurely
sinusoidal waveform. Now After connection of such type of
device the system becomes stable and remove harmonic
contain from the voltage and current.
B. Results After Compensation
The main function of DSTATCOM is to provide
reactive power as demanded by the load and mitigate the
harmonics from the system. Therefore, with the help of
DSTATCOM source currents are maintained at unity power
factor and reactive power burden on the system gets
reduced. Due to the compensation of the reactive power by
DSTATCOM source has to supply only real power.
Traditionally, power quality issues have been
addressed by the use basic devices such as passivefilter, and
more advanced filtering technologies, such as a static
synchronous compensator, active power filter(APF),
Dynamic Voltage Regulator, and Unified power quality
conditioner (UPQC). After connecting DSTATCOM to the
system it is observed from Fig. that load current is same
which is drawn by load but source current is approximately
sine wave, also source current and voltage at PCC are in
phase with each other. So, power factor is maintained equal
to unity.
Fig -13: Supply Side Voltage(V) after the connection of D-
STATCOM
As result shown in fig 13. The waveform of supply side
voltage is become exactly sinusoidal after the connecting D-
STATCOM; this is because of the mitigation of Harmonics
from the system voltage.
Similarly, the harmonic mitigation done with the help of D-
STATCOM from Load side voltage also. The result of Load
side voltage after the connection of D-STATCOM is shown in
Fig14
Fig -14: Load Side Voltage(V) after the connection of D-
STATCOM
Fig -15: Load Side Current(A) after the connection of D-
STATCOM
As the D-STATCOM is mitigate the harmonics from the
system fig15 shows the current waveform of load which is
nearly sinusoidal after the connection of custom power
device like D-STATCOM.
VI. CONCLUSION
A Static compensator (STATCOM) is a flexible AC
transmission system(FACTS) controller, which can either
absorb or deliver reactive power to a power system.
Distribution static Compensator(D-STATCOM) is proposed
for compensation of reactive power and unbalance caused
by various load in distribution system. Custom power
devices can be used for power quality improvement in the
distribution system. This paper proposed the working
principal of D-STATCOM whichisbasedonVSCprincipleand
analysis done in system for normal operation, introduce
harmonics in the system then connect D-STATCOM and
Annalise the system after the connection of device. A D-
STATCOM inject a current into the system to correct the
voltage sag, swell, and power factor and also mitigate the
harmonic contain introduce in the system because of non
linear load.
REFERENCES
[1] H. Akagi, Y. Kanazawa, and A. Nabae, “Instantaneous
Reactive power compensators comprising Switching
Devices without Energy Storage Components,” IEEE
Transactions on Industry Applications,vol.IA-30 , no. 3,
pp. 625-630, 1984.

[2] Mr.Sharad S.Pawar, Mr.A.P.Deshpande, Mrs.Meera
Murali, “Modelling and Simulation of DSTATCOM for
Power Quality Improvement in Distribution System
Using MATLAB Simulink Tool”, 2015 International
Conference on Energy Systems and Applications (ICESA
2015)
[3] B. Singh and J. Solanki, “A Comparision of Control
Algorithms for DSTATCOM”,IEEE TRANSACTIONS ON,
INDUSTRIAL ELECTRONICS ,vol.56,no.7,pp.2738-
2745,2009.
[4] R. C. Dugan, M. F. Mc Granaghan, and H. W. Beaty,
“Electrical power system quality,” New York,
NY:McGraw-Hill,c1996,vol.1,1996.Eason,
[5] N.G. Hingorani, “Introducing Custom Power”,IEEE
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SCIENCE A, ISSN 1673-565X (Print); ISSN 1862-1775
(Online)
BIOGRAPHIES
Rinkesh G. Satpute PursuingMBA
in Power Management and also
received his Bachelor degree in
Electrical Engineering in 2017
from RGCER, Nagpur and
completed Mtech from YCCE,
Nagpur in Integrated Power
System in 2019. Now Currently
working as an Assistant Professor
in the Electrical Engineering
Department, DMIETR, Wardha.
Yashashri B. Deshmukh received
her Diploma in Electronics and
Telecommunication from PDGP,
Amaravati then Bachelor degreein
Electrical Engineering in 2017
from SSGMC, Shegaon and
completed Mtech from YCCE,
Nagpur in Integrated Power
Poonam A. Shende received her
Bachelor degree in Electrical
Engineering in 2016 from PCE,
Nagpur and completedMtechfrom
YCCE, Nagpur in Integrated Power
Suryakant B.Morey received his
Bachelor degree in Electrical
Engineering in 2013 from KDK,
Nagpur and completedMtechfrom
GCE Karad in Electrical Power

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