A Review on Optimization Techniques for Power Quality Improvement using DSTATCOM Neural Network Approach

International Journal of Trend in Scientific Research and Development (IJTSRD)
Volume 5 Issue 4, May-June 2021 Available Online: www.ijtsrd.com e-ISSN: 2456 – 6470
@ IJTSRD | Unique Paper ID – IJTSRD42403 | Volume – 5 | Issue – 4 | May-June 2021 Page 705
A Review on Optimization Techniques for Power Quality
Improvement using DSTATCOM (Neural Network Approach)
Amit Radhakrishna Parhad1, Pramod Kumar Rathore2
1Student, 2Assistant Professor,
1,2RKDF College of Engineering, Bhopal, Madhya Pradesh, India
ABSTRACT
As demand for electricity has risen exponentially, power production and
transmission are affected by scarce energy, environmental constraints and
other losses. Soft computing methods to fix the sag,swell anddisruptionofthe
supply voltage in the distributed device. At present, a broad variety of highly
versatile controls that leverage on newly available power electronics
components are evolving for custom power applications. Control electronic
equipment intended to improve the stability and efficiency of electricityflows
in low voltage distribution networks. The control algorithm is used to derive
the fundamental weighted value of the activeandreactive powercomponents.
Using a digital signal processor, DSTATCOM is built and its output as a
DSTATCOM is found to be satisfactory for different types of loads.
KEYWORDS: D-Statcom, DVR, Voltage Dips, Swells, Power Quality
How to cite this paper: Amit
Radhakrishna Parhad | Pramod Kumar
Rathore "A Review on Optimization
Techniques for Power Quality
Improvement using DSTATCOM (Neural
Network Approach)"
Published in
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of Trend in Scientific
Research and
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ISSN: 2456-6470,
Volume-5 | Issue-4,
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I. INTRODUCTION
As the power demand has been increasing rapidly, power
generation and transmission are being affected due to
limited resources, environmental restrictions and other
losses. The quality of available supply power has a direct
economic impact on industrial and domestic sectors which
affects the growth of any nation. This issueismoreserious in
electronic based systems. The level of harmonics and
reactive power demand are popular parameters thatspecify
the degree of distortion and reactive power demand at a
particular bus of the utility.
This implies that some measures must be taken in order to
achieve higher levels of Power Quality. The FACTS devices
and Custom power devices are introduced to electrical
system to improve the power quality of the electrical power.
DVR, STATCOM/DSTATCOM, ACTIVE FILTERs, UPFC, UPQC
etc are some of the devices used to improve the power
quality of the voltage and current. With the help of these
devices, we are capable to reduce the problems related to
power quality. Under the thesis work among the different
custom power devices DSTATCOMhasbeenusedtoimprove
the quality of power under different conditions.
the power system, the major power quality problems are
poor load power factor, harmoniccontentsinloads,notching
in load voltages, DC offset on load voltages, unbalanced
loads, supply voltage distortion, voltage sag, & voltageswell.
One of the most common power quality problems today is
voltage sag. Voltage sag is a short time event during which a
reduction in R.M.S. voltage magnitude occurs. It is often set
only by two parameters,depth/magnitudeandduration.The
voltage dip magnitude is ranged from 10-90% of nominal
voltage (which corresponds to 90-10% remaining voltage)
and with a duration from half a cycle to 1 minute. In a three-
phase system, the voltage sag is by nature a three-phase
phenomenon which affects both the phase-to-ground and
phase-to-phase voltages. The faults are single-phase or
multiple-phase short-circuit, which leads to high currents
[1].
The introduction of FACTS has giventhe newdirectionto the
power system to solve the power quality problems. At
present, a wide range of very flexible controllers are
emerging for custom power applications. The FACTS
controllers like SVC, TCSC, TCPST, STATCOM, SSSC, UPFC,
etc. are mainly used controllers. Among these,theSTATCOM
is the most effective device. The STATCOM is a shunt device
& based on VSC principle. The inverter circuit along with
interface transformers/inductors is called a STATCOM.
II. VOLTAGE SOURCE CONVERTER (VSC) and
CUSTOM POWER DEVICES
A voltage-source converter is a power electronic device,
which can generate a sinusoidal voltage with any required
magnitude, frequency and phase angle. The VSC is used to
either completely replace the voltage or to inject the ‘Dip
IJTSRD42403

International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470
voltage’. The ‘Dip voltage’ is the difference between the
nominal voltage and the actual. The converter is normally
based on some kind of energy storage i.e. capacitor, which
will supply the converter with a DC voltage. The solid-state
electronics in the converter is then switched to get the
desired output voltage. Normally the VSCisnotonlyusedfor
voltage dip mitigation, but also for other power quality
issues, e.g. flicker and harmonics.
A. Shunt voltage controller [Distribution Static
Compensator (DSTATCOM)]
The D-STATCOM (Distribution Static Compensator)
configuration consists of a VSC, a DCenergystoragedevice;a
coupling transformer connected in shuntwiththeacsystem,
and associated control circuits. Fig. 1,
Figure 1 Schemetic Dig Of D-STATCOM
shows the basic configuration of D-STATCOM. Here, such
device is employed to provide continuousvoltageregulation
using an indirectly controlledconverter.Suitableadjustment
of the phase and magnitude of the D-STATCOM output
voltages allows effective control ofactiveandreactive power
exchanges between the D-STATCOM and the AC system.
The VSC connected in shunt with the AC system provides a
multifunctional topology which can be used for up to three
quite distinct purposes:
A. Voltage regulation and compensation of reactive power
B. Correction of power factor
C. Elimination of current harmonics.
Figure 1 shows the shunt injected current Ish corrects the
voltage sag by adjusting the voltage drop across the system
impedance Zth. The value of Ish can be controlledbyadjusting
the output voltage of the converter.
Ish = IL – Is
It is mentioned that the effectiveness of the STATCOM in
correcting voltage sag depends on the value of Zth or fault
level of the load bus. When the shunt injected current Ish is
kept in quadrature with VL the desired voltage correction
can be achieved without injecting any active power into the
system. On the other hand, when the value of Ish is
minimized, the same voltagecorrectioncan beachievedwith
minimum apparent power injection into the system.
B. Dynamic voltage restorer / regulator (DVR)
The Dynamic Voltage Restorer (DVR) is a series connected
device analogous to a SSSC. The main function of a DVR is to
eliminate or reduce voltage sags seenbysensitiveloadssuch
as semiconductor manufacturing plant or IT industry.. They
have been designed to compensate three phase voltage sags
up to 35% for duration of time less than half a second
(depending on the requirement). If the voltage sag occurs
only in one phase (caused by SLG faults) then the DVR may
be designed to provide compensation for sags exceeding
50%. A DVR is connected in series with the feeder using a
transformer. The low voltage winding is connected to the
converter. A DVR with IGBT/IGCT devices can be controlled
to act as a series active filter to isolate the load from voltage
harmonics on the source side. It is also possible to balance
the voltage on the load side by injecting negative and/or
zero sequence voltages in addition to harmonic voltages.
Figure 2: Basic configuration of DVR
C. UNIFIED POWER QUALITY CONDITIONER (UPQC)
Unified power quality conditioners are viable compensation
devices that are used to ensure that delivered power meets
all required standards and specifications at the point of
installation.
Figure 3: Basic Configuration of UPQC
The ideal UPQC can be represented as the combination of a
voltage source converter (injecting shunt current) and a
common DC link (connected to a DC capacitor).
UPQC consist of combined series active power filter that
compensates voltage harmonics of the power supply, and
shunt active power filter that compensates harmonic
currents of a non-linear load. This dual functionality makes
the UPQC as one of the most suitable devicesthatcouldsolve
the problems of both consumers as well as of utility. UPQC,
thus can help to improve voltage profile and hence the
overall health of power distribution system
III. SYSTEM CONFIGURATION AND CONTROL
ALGORITHM AND PROPOSE WORK
The performance of any custom power device depends very
much upon the control algorithm used for the reference
current estimation and gating pulse generation scheme. An
implementation of a three phase distribution static
compensator (DSTATCOM) using a control algorithm for its
functions under nonlinear loads such as load balancing and
reactive power compensation for power factor, and zero
voltage regulation. Themain advantageofthismethodisthat

it requires only waveformsofvoltagesandcurrents.Aneural
network with memory is used to identify the nonlinear load
admittance. Once training is achieved, the neural network
predicts the true harmoniccurrentoftheloadwhensupplied
with a clean sine wave. Feed forward back propagation (BP)
artificial neural network (ANN) consists of various layers
such as the input layer, hidden layer, and output layer. It is
based on feed forward BP with a high ability to deal with
complex nonlinear problems.
The BP control algorithm is also used to design the pattern
classification model based on decision support system. The
standard BP model has been used with the full connection of
each node in the layers from input to theoutputlayers.Some
applications of this algorithm are as to the identification of
user faces, industrial processes, data analysis,mappingdata,
control of power quality improvement devices, etc. The
control of power quality devicesbyneural network isa latest
research area in the field of power engineering. The
extractionofharmoniccomponentsdecidestheperformance
of compensating devices. The BP algorithm which trained
the sample can detect the signal of the power quality
problem in real time. Its simulation study for harmonic
detection is presented. The proposed control algorithm is
used for harmonic suppression and load balancing in PFC
and zero voltage regulation (ZVR) modes with dc voltage
regulation of DSTATCOM. In this work, the proposedcontrol
algorithm on a DSTATCOM is implemented for the
compensation of nonlinear loads.
A voltage source converter(VSC)-based DSTATCOM is
connected to a three phase ac mains feeding three phase
linear/nonlinearloadswithinternal gridimpedancewhichis
shown in Fig. 4
Figure 4 Schematic diagram of VSC-based DSTATCOM.
The performance of DSTATCOM depends upon the accuracy
of harmonic current detection. For reducing ripple in
compensating currents, the tuned values of interfacing
inductors (Lf) are connected at the ac output of the VSC. A
three-phase series combination of capacitor (Cf) and a
resistor (Rf) represents the shunt passive ripple filter which
is connected at a point of common coupling (PCC) for
reducing the high frequency switching noise of the VSC. The
DSTATCOM currents (icabc) are injected as required
compensating currents to cancel the reactive power
components and harmonics of the load currents so that
loading due to reactive power component/harmonics is
reduced on the distribution system. In this algorithm, the
phase PCC voltages, source current (isa,,isb, isc) and (iLa,,iLb, iLc)
and dc bus voltage (Vdc) are required for the extraction of
reference source currents. There are two primarymodesfor
the operation of this algorithm: The first one is a feed
forward, and the second is the BP of error or supervised
learning.
A BP training algorithm is used to estimate the three phase
weighted value of load active power current components
(Wap,Wbp,Wcp) and reactive power current components
(Waq,Wbq,Wcq) from polluted load currents using the feed
forward and supervised principle. In this estimation, the
input layer for three phases (a, b, and c) is expressed as
The detail application of this algorithm for the estimation of
various control parameters is given as follows.
Ilap=WO+iLauap+iLbubp++iLcucp (1)
Ilbp=WO+iLauap+iLbubp++iLcucp (2)
Ilcp=WO+iLauap+iLbubp++iLcucp (3)
Where Wo is the selected value of the initial weight and
(uap,ubp,ucp) are the in-phase unit templates. In-phase unit
templates are estimated using sensed PCC phase voltages
(Vsa,Vsb,Vsc) It is the relation of the phase voltage and the
amplitude of the PCC voltage (Vt). The amplitude of sensed
PCC voltages is estimated as
(4)
The in-phase unit templates of PCC voltages (uap,ubp,ucp) are
estimated as
(5)
The extracted values of ILap, ILbp, ILcp are passed through a
sigmoid function as an activation function, and the output
signals Zap,Zbp,Zcp of the feedforwardsectionare expressedas
(6)
(7)
(8)
The estimated values of Zap,Zbp,Zcparefedtoa hiddenlayeras
input signals. The three phase outputs of this layer ILap1,ILbp1,
ILcp1 before the activation function are expressed as
Ilap1 = wO1+wapzap+wbpwbp++wcpucp (9)
Where ( W01, Wap,Wbp,Wcp) are the selected value of the
initial weight in the hidden layer and the updated values of
three phase weights using the average weighted value (Wp)
of the active power current component as a feedback signal,
respectively. The updated weight of phase “a” active power
current component of load current “Wap” at the nthsampling
instant is expressed as

where (n) and (n) are `the average weighted value of the
active power component of load currents and the updated
weighted value of phase “a” at the nth sampling instant,
respectively and wap1(n) and Zap(n) are the phase “a”
fundamental weighted amplitude of the active power
component of the load current and the output of the feed
forward section of the algorithm at the nth instant,
respectively. f(Iap1) and μ arerepresentedasthederivativeof
Iap1 components and the learning rate. Similarly, for phase
“b” and phase “c,” the updated weighted values of the active
power current components of the load current are also
expressed as same. The extracted values of Iap1, Ibp1, and Icp1
are passed through a sigmoid function as an activation
function to the estimation of the fundamental active
components in terms of three phase weights wap1, wbp1, and
wcp1 as
(13)
(14)
(15)
IV. CONCLUSION
This study is used to examine the role of DSTATCOM in
improving the power efficiency of static linear and non-
linear load delivery networks. The PI controller is used with
the system to increase its efficiency. The evaluation method
is analysed, and the findings are discussed in the previous
portion. DSTATCOM in distribution networks undervarying
fault conditions and it can be inferred that DSTATCOM
effectively increases the power efficiency of static linear
distribution networks. A VSC-based DSTATCOM was
acknowledged as the most favored solution for optimizing
power efficiency as a PFC and retaining a rated PCC voltage.
A three-phase DSTATCOM has been introduced to
compensate for non-linear loads by utilizing a BPT control
algorithm to check its efficacy. For the extraction of
reference source currents, the proposed BPT control
algorithm was used to produce switching pulses for
DSTATCOM VSC IGBTs.
V. REFERENCES
[1] International Journal of Scientific and Research
Publications, Volume 4, Issue 4, April 2014 ISSN
2250-3153.
[2] Roger C. Dugan, Mark F. McGranaghan and H. Wayne
Beaty, Electrical Power, Systems Quality, Tata Mc
Graw- Hill. Pages 1-8 and 39-80.
[3] Bhim Singh, Alka Adya, A. P. Mittal, J. R. P Gupta,
“Power Quality Enhancement with DSTATCOM for
Small Isolated Alternator feeding Distribution
System”, conference on Power Electronics and Drive
Systems, vol. 1, pp. 274-279, 2005.
[4] Alexander Kusko, Sc. D., P. E., Marc T. Thompson, Ph.
D., Power Quality in Electrical Systems,Tata McGraw-
Hill publications, 2007.
[5] H. Nasiraghdam and A. Jalilian, “Balanced and
Unbalanced Voltage Sag Mitigation UsingDSTATCOM
with Linear and Nonlinear Loads”, Conference on
World Academy of Science, Engineering and
Technology, pp. 20–25, 2007.
[6] J. Sun, D. Czarkowski and Z. Zabar, “Voltage Flicker
MitigationUsingPWM-BasedDistributionSTATCOM”,
Conference on Power Engineering Society Summer
Meeting, Publication, vol. 1 , pp. 616 – 621, 2002.
[7] Sung-Min, Woo Dae-Wook Kang, Woo-Chol Lee and
Dong-Seok Hyun, “The Distribution STATCOM for
Reducing the Effect of Voltage Sag and Swell”,
Conference on IECON’O1: The 27th Annual
Conference of the IEEE Industrial Electronics Society
Publication, vol. 2, pp. 1132 - 1137, 2001.
[8] M. G. Molina, P. E. Mercado, “Control Design and
Simulation of DSTATCOM with Energy Storage for
Power Quality Improvements”, Conference on IEEE
PES Transmission and Distribution Conference and
Exposition Latin America, Venezuela, pp. 1 - 7, 2006.
[9] Pierre Giroux, Gilbert Sybille Hoang Le-Huy,
“Modeling and Simulation of a DistributionSTATCOM
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[10] Afshin Lashkar Ara and Seyed Ali Nabavi Niaki,
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Distribution Barcelona, vol. 2, pp. 44, 2003.
[11] Ben-Sheng Chen and Yuan-Yih Hsu, “An Analytical
Approach to HarmonicAnalysisandControllerDesign
of STATCOM”, Conference on IEEE Transactions on
Power Delivery, vol. 22, 2007

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