IRJET - Design and Simulation of DSTATCOM using Fuzzy Logic Controller

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 08 Issue: 01 | Jan 2021 www.irjet.net p-ISSN: 2395-0072
© 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 157
Design and Simulation of DSTATCOM using Fuzzy Logic Controller
Mr. Amit S Ghantimath1, Mr. Vinayak K U2
1PG Student, EEE Dept. SIT Tumkur
2Assistant Professor, EEE Dept. SIT Tumkur
---------------------------------------------------------------------***----------------------------------------------------------------------
Abstract - This project mainly focuses on the DSTATCOM and
different control methodology of DC capacitor voltage
basically PI controller is used to regulate dc capacitor voltage,
by using different control algorithms i.e load compensation.
However, when loading changes, the DC capacitor voltage
effect on load compensation. In this topic, a fuzzy logic
technique is applied to improve the DC link transient
performance. The fuzzy logic-based supervisor varies the
proportional and integral gains of the PI controllerduringthe
transient period straightaway after a load change. A
significant drop in the error in dc-link capacitor voltage
during load change compared to a normal PI controller is
obtained. The proposed algorithm is proved by MATLAB
Simulation.
Key Words: Power Quality, Fuzzy logic, Harmonics,
Flicker, DATACOM
1. INTRODUCTION
The “Power Quality” is generally a broad theory and related
to electrical distribution as well as utilization schemes that
result from any voltage, frequency, a current abnormality
from normal operation. For ideal electrical supply systems,
power supplied accurate current and voltage are sinusoidal
waveforms, being reliable and safe. But the electric utilities
control voltage quality and levels but not able to control the
current since load profile dominates the shape of current
waveforms. Thus, the utility end must maintain the bus
voltage quality at always. This consideration leads to power
quality (PQ) is equal to voltage quality.
Defining accurately the Power Quality is a task; the common
definitions are:
Definition: “Power quality is a summarizing concept,
including different criteria to judge the technical quality of
an electric power delivery”. Another description is
introduced and accepted by Ontario Hydro.
Definition: “Power Quality is the degree to which both the
utilization and delivery of electric power affects the
performance of electric equipment”.
Definition: “Power quality problem is any power problem
manifested in voltage, current, or frequency deviation that
results in failure or misoperation of customer equipment”.
Delivering a definite level of voltage stability and sinusoidal
quality must worry for designers of the utility grid. When
electrical utilization/ distribution end is unified, electric
loads as well its profile, design of grid, utility maintenance
with the nonlinearity of electric load degree factors disturbs
power quality. Power Quality (PQ) has caused huge anxiety
to utilities with rising use of sensitive as a well susceptible
electronic as well computing device (e.g. desktop computer,
uninterruptible power supplies, computer-aided design
workstation, printers, fax, etc) different nonlinear loads.
2. The factors behind the increasing concern about the
quality of power are:
 With the introduction of modern microelectronics
and sensitive computer devices, the characteristics
of electrical loads have changed significantly.
 Harmonics induces devices to cause failureandalso
reduce the efficiency of electrical distribution and
network performance..
The electrical power system is currently interlinked,
automated and thus any system failure will major financial
consequences due to process shutdown, especially for large
industrial customers. The sudden changes in electric load
profile from initially linear sort of critically nonlinear, it
creates continuous power quality problems always
complicated to identify as well as complex.
Power Quality issues
 Harmonics (super, integral and
interharmonics)
 Voltage fluctuations, swells, flicker, sags and
Transients
 Voltage imbalance, voltage frequency and
magnitude.
In the power system, here types of power quality
instabilities. They are differentiated into types and their
explanation important to categorize results for
measurements as well as define electromagnetic
phenomena, which results in power quality aspect.
Instabilities derived from the supply side, as well as others
by load itself.
 Short duration variations in voltage
 Long duration variations in voltage

 Transient conditions
 Voltage uncertainty
 Distortion of waveform
2. DSTATCOM
There are many changes in recent development in the usage
of critical loads in all sectors, such as voltage sags, transient,
swells and unbalance. This kind of disruptions that have
triggered or shut down malfunctions and appeartolosesales.
There are many strategies available to avoid malfunctioning
of the devices due to voltage swells, sags. The usage of
DSTATCOM to reduce voltage swell as well voltage sag is one
of the broadly utilizedapproaches.Shuntcontroller,knownas
DistributionstaticcompensatorsorDSTATCOM.DSTATCOM is
an efficient tool in the distribution network to minimise
disruptions due to power quality issues. Voltage swells are
one of the critical disruptions in electricity systems. As seen
the new DSTATCOM consisting of a voltage source inverter
(VSI), a shunt inject transformer, a filtering unit and storage
for energy unit that can be attachedtothedc-link.Sags/swells
of voltage can appear more generally than other phenomena
of power quality. The most serious power quality challenges
in the method of power delivery are these sags/swells. In the
following segment. In an attempt to optimise certain devices
for voltage sag, swell reduction as well as reactive power
compensation in a network, the segment is intended to
analyse and suggest the design of DSTATCOM.
FIG-1: DSTATCOM basic model
2.1 DSTATCOM OPERATING PRINCIPLE
DSTATCOM is regulated reactivesourcethatcontainsa shunt-
connected Voltage Source Converter (VSC) and a DC
connection capacitor that can produce or absorb reactive
power. That similar to perfect synchronous system that
produces a stable series of three simple frequency sinusoidal
voltage with manageable amplitude and angle of phase. This
ideal device has no inertia, has an immediate replay may not
adjust the impedances of the device, andcanproducereactive
(together capacitive /inductivereactivepower)internally.No
reactive power is supplied to the device if t output voltage of
VSC is equivalent to AC terminal voltage. If the output voltage
is higher AC terminal voltage, the operating mode of
DSTATCOM is capacitive / vice versa. In two voltages, the
amount of reactive power flows will equal to variation.
FIG.2: Basic structure of DSTATCOM in transmission line
It should be remembered that voltage control at Point of
common coupling (PCC) as well modification of power factor
are being accomplished at the same time. The compensation
DSTATCOM applied for voltage control at PCC must be such
that supply current contributes to supplyvoltagesandsupply
current must in phase with supply voltages for power factor
improvement. To studies of performances of DSTATCOM for
reactive power compensation as well as power factor
improvement, control algorithms described in this document
are used.
3. CONTROLLING STRATEGY
This portion generally presents the DSTATCOM control
method for DC capacitor voltage, usually, dc capacitor
voltage controlled by the PI controller. Several control
algorithm managedforloadcompensation.However,thereis
significant variance in dc capacitor voltage through load
adjustments may influence compensation.Thetask forfuzzy
supervision method based on logic is developed to increase
dc link's transient performances. Through transient cycle
straightaway after load variation, fuzzy logic dependent
supervisor differs PI controller's proportional and integral
gains. Compared to a common PI controller, a significant
reduction in defect dc connection capacitor voltage all
through load variation is achieved. Using comprehensive
simulation tests, the effectiveness ofthesuggestedapproach
is shown.
3.1 DSTATCOM FOR REGULATION OF VOLTAGE
At consumer stages, DSTATCOM increases voltageswell,sag
in this method of the voltage controller (also named the
decouple method) is used as a DSTATCOM control method.
The dq0 revolving reference frame was used in this control
scheme since it provides greater precision than stationary
frame-based strategies. Three-phase voltage terminal are in
Vabc, Iabc 3 -phase currents pumped into the system by
DSTATCOM, Vrms is RMS at voltage terminal, Vdc is DC
voltage determined in the capacitor, aswell referencevalues

are shown by superscripts. A phase-locked loop (PLL) is
used in such a controller to synchronise 3phase voltage at
converter output with zero crossings of the basic portion of
phase-A terminal voltage. The angle f of the abc- dq0 (and
dq0-abc) transition is then given by the PLL. For
proportional-integral (PI) regulators still exist. First one is
answerable to regulating the terminal voltages with ac
network via the reactive power exchange. The reactive
current reference Iq* is given by this PI regulator, which
confined between pulse 1pu capacitive and minus 1pu
inductive. Another PI regulator was responsible for
maintaining dc voltage stable with the ac network by a
limited active power transfer, reimbursing transformer as
well inverter for active power losses. The active current
reference Id* is offered by this PI regulator. After a dq0-to-
abc transition, other two PI regulator evaluate voltage
reference Vd* and Vq* send to converter's PWM signal
generator. Finally, the 3-phase voltage needed at converters
output Vab*.
FIG-3: PROPOSED CONTROL TECHNIQUE OF DSTATCOM
3.2 DC -LINK PI CONTROLLER AND FUZZY CONTROLLER
It is assumed that the source voltages are controlled and
rigid.
For maintaining unity power factor initially being source
equal to zero and hence equal zero. The word Pl avg is the
mean load power rate and if there is no load adjustment, will
be a fixed value. This is measured using the half-cycle
moving average filter. Ploss is the amount of power must be
taken from the source in an attempt to correct for the
blackouts in the inverter. If this concept is not used, then the
dc capacitor can supply these errors and the dc-link voltage
will decrease. However, the specific losses that exist in the
inverter are highly difficult to compute a PI controller, Ploss
is thus obtained. The value of Ploss is differing at every half
period cycle or regular interval 1800 at steady state. The
sum of the term for P loss and Pl avg defines quantity power
obtained from the source. It takes half a cycle for the moving
average filter used to calculate Pl avgtoresolvedowntonew
average power valuation. The power for the load is
momentarily delivered from DSTATCOM at period. If the
load is increased, this tends to the down value of dc-link
voltage of enhances appeared capacitor voltage unless the
load is decreased. The capacitor voltage must stay as near to
the reference value as possible for good compensation.
Afterwards load change occurred, capacitor voltage takes 8
cycles to resolve, based on the Kp and Ki values. Profits are
selected by trial and error most of the time. For the
DSTATCOM programme, a methodisgiventoobtaingood Kp
and Ki value. This was used during stable action as the basic
values. Although likely to boost the qualityofdclink through
transient activity by modifying the PI controller's gains
applied a set of the heuristic rule on skilled information.
Also, technological advances such quicker DSPs allows us to
rise the testing rate for a better inputonhowdeviceanswers
to updates. Fuzzy based controller shown to function with
nonlinear systems, such as DSTATCOM. It was shown in this
article that fuzzy logic-based monitoring of gain of the dc-
link PI controller enhances transient as well settling voltage
regulation output of dc link. The applied fuzzy logic is
programmed as acceptable. In the usual sequence, this
article has been decided. A description of VSI configuration
for DSTATCOM is mostly provided first and state-space
analysis applied to simulate DSTATCOM operation is
clarified. For this method, the fuzzy supervisor's model is
explained. In the final section, the methods andresults ofthe
simulation are shown, showing increased performanceofdc
connections. There few active power-sharing among
DSTATCOM and load throughoutloadchanges.Thatrefersto
dc capacitor voltage being decreased or increased. The word
Ploss is regulated using the PI controller to indicate that the
voltage of the dc capacitor will not differ from the standard
control output of the PI controller.
The inaccuracy in dc-link voltage is input to the PI controller
and output is the Ploss value. The valueofPlossisdependent
on the Kp, Ki value and dc-link voltage error. Thus it
important to properly tune Kp as well Ki.Duetothesystem's
inherent non-linearity and difficult, it is impossible to tune
the controller's gains. Usually, it was worked through
experimentation. Using the energy theory proposed in, the
basic values of Kp and Ki were designed. It has also been
seen in the literary works that fuzzy monitoringinnonlinear
systems could even boost performances of PID controller.
However, most focus on setpoint alteration in control
executions. The term derivative control not operated so
when was using only with proportional control,
enhancement instability may but may not be achievedthat if

operated with integral control and tuning for better
performance is impossible.
3.3 DESIGN FOR THE SUPERVISOR FUZZY LOGIC FOR PI
CONTROLLER
For a wide variety of control procedures, the PID controller
is commonly utilized in the industry and provides adequate
output until calibrated when the parameters are well
established and there is not much variance. Because
operational conditions differ, more adjustment for good
performance might be required. Since many methods are
dynamic and nonlinear, a good alternative appears to be
fuzzy control. The literature demonstrates many methods
where a fuzzy controller has removed the PI controller.
However, it is necessary to use a conduct a detailed
regulation instead of fully changing the control operation by
tracking the gains by fuzzy technique to boost device ability.
A PI controller chosen to manage the voltage of the dc
connection as the inclusion of an integral termconfirmszero
steadies for state error. A disturbance used in dc connection
capacitor voltage waveform since instantaneous
symmetrical portion principle worked the compensator
often supplies the oscillating portion of active control. The
mean fluctuatingpowerexchangeinamongthecompensator
As well load is therefore often zero. In the simulation
performance, this disturbancecanbeseenin.Thelevelling of
the fuzzy controller has configured to present a better
output during the transient phase, regardless of the ripple
involvement. Choosing the proper inputs and outputs and
constructing each of four elements of fuzzy controller logic
are some of the key facets of fuzzy design controller. In the
paragraphs below, both of these will be mentioned: fuzzy
controller also triggered during at transient condition and
until the value of the dc connection voltage stabilises, gains
of the controller are constant at a value of the stable state. A
detailed explanation was already given for configuration of
the fuzzy logic regulator.
Fig 3.3 FUZZY CONTROLLER ARCHITECTURE
3.4 DEFFUZIFICATION
The interface for fuzzification alters the inputs to a shape in
which the control algorithm can use them. It carries in crisp
data input and allocates the membership function in a range
of input signal drops to a membership value. Trapezoidal,
exponential or triangular are standard input membership
features. Seven triangular membership functions were
chosen: NL (Negative Large), NS (Negative Small),NM
(Negative Medium), Z (Zero), PM (Positive Medium),PS
(Positive Small) and PL (Positive Large) forbotherrors(err)
and error change (derr) the input membership functions.
Based on the requirements of the method, the adjustment of
the input membership function iscarriedout.Amembership
value relating to [0 1] applies to each membership function.
It can be noted that either one or two membership functions
will be effective for each error value or change in error.
The major functions for inference mechanism are a) the
rules applicable to the present situation are decided based
on the active membership in error functions and alter in
error input. (b) As once rules are laid down, the assurance of
the control action is determined on the membership values.
This is known as the quantitative analysis of the premise.
Thus, we will have a set of rules at end of this method, each
with the specific assurance of being appropriate.Inrule base
through which control action is gained, the database
carrying these rules is available. The next part the rule base
addressed.
FIG 3.4 (a Functions for Membership for error inputs.
(b) Membership functionality for error input shift in error
inputs

This is regarded as the estimation of the premise. Thus, we
will have a set of rules after such a process, each with a
definite guarantee of being true. In the rule base through
which control action is taken, the database holding these
rules is available. In the next chapter, the rule base would be
addressed. An instance of a rule is given. . (7). "change in
error" is PM (positive medium) and If "error" is PL (positive
large) "THEN "_Kp" is L (Large Kp) "_Ki" is SKi (Small Ki)The
lowest operation used toevaluateguaranteecalledμpremise
of law established by addition. The words PL and PM are the
membership functions for inaccuracy and for alteration in
inaccuracy respectively.
3.5 THE RULE BASED
A crucial factor in building the model is designing the rule
base. How the rule base has been built is crucial to consider..
After a rise in the load without the implied ripple due to
adjustment, displays a standard dc connection voltage
waveform. Based upon the sign of erroraswell asthechange
of error, the waveform was separated into separate parts.
Dependent on the part in the graph the waveform is in the
rules in rule base are configured. The main points related in
the design of rule. The following are significant points
related in construction of rule base: a) If the error will high
and error shift indicates a waveform of dc-link diverging
through reference, Kp increases. B) If waveform exceeds
reference value after to minimise overshoot and boost
settling time, increase the Ki value.Tworulebasematrice for
Kp and Ki were created keeping these aspects in mind. Uh,
the table gives the matrix base rule Kp and the table. The
rule base matrix for Ki is given. LKi, SKi and Z are output
membership features for proportional gain,andL,M,SandZ
are the output membership features for the gain of integral.
These matrices have laws, such as theexampleseenin,for all
different pairs of error and error adjustment membership
functions. Thus the rule and its surety are dictated by the
rule base using data from the rule base. The mechanism for
transforming the fuzzy outcome to a crisp control operation.
FIG 3.5Typical dc-link voltage waveform after a load
change
FIG-3.6 A.Rule base for change in kp . B. Rule base for
change Ki
3.6. DEFUZZIFICATION
Inference mechanism gives us a list of norms with a
μpremise each. These rules and about there various
μpremise values are considered by the defuzzification
mechanism, their impact is combined, and crisp, numerical
outputs obtained. Thus the behaviour of the fuzzy controller
is converted into a nonfuzzy controlled action. In this task,
the' gravity of the centre' technique was working. If we're
using the technique, the resulting crisp output is responsive
to all the inference mechanism's effective fuzzy outputs. .
The output membership features selected for Kp and Ki are
shown below. The weighted element of centre value for
active output membership values taken as the output
according to this method, weights becoming area below the
level line output. Upremise.
FIG 3.6 Output membership function
(a) For Kp (b) For Ki
4. Simulations and Result
FIG-4.1: MATLAB Simulink model without DSTATCOM

FIG-4.2 Current Waveforms
FIG-4.3: Voltage waveform.
FIG-4.4: MATLAB Simulink model with DSTATCOM
FIG-4.5: MATLAB Simulink model with fuzzy logic
DSTATCOM
FIG-4.6: Output voltage introducing the fuzzy logic
Dstatcom
FIG-4.7: Output current introducing the fuzzy logic
Dstatcom

5. CONCLUSION
The fuzzy supervisory logic control in a D-STATCOM was
suggested to DC link PI controller. In a way that promotes
quality, the supervisor changes the gain of the PI controller
also through a transient phase. The MATLAB technological
environment, the scheme was modelledandsimulatedusing
a case study. With and without the fuzzy boss, the output of
DC connection voltage aswell itsperformancecompensation
remained observed. The result of the simulations shows a
50-60% decrease on the voltage deviance of DC connection
voltage with a fastest settling time.Bettercompensation was
noted. Consequently, the execution of a fuzzy supervisor for
DC link voltage control in D-STATCOM for load
compensation has proved through simulations. For load
compensation, the instantaneous symmetrical component
hypothesis wasused.Worthycompensationhasperceivedas
source current THDs for each phase is 1.63%, 1.77% and
1.58% while load THDs are 12.37%, 10.5% and 14.54%
consequential. Thus, simulation work for the
implementation of a fuzzy supervisor for DC link voltage
control in DSTATCOM by using the instantaneous
symmetrical component concept for the load compensation
has been performed.
REFERENCES
[1] Harish Suryanarayana andMaheshk.Mishra,“Fuzzylogic
based supervision of DC link PI control in aDSTATCOM“,
IEEE India conference 2008, volume-2, pages 453-458
[2] J.L.Aguero,F. Issouribehere, P.E.Battaiotto,” STATCOM
Modelling for mitigation of voltage fluctuations caused by
Electric Arc Furnaces”, IEEE Argentina conference 2006, pp:
1-6.
[3] N. Hingorani , Lasjlo Gyugyi, “Understanding FACTS,”1st
edition ,IEEE pres , Standard publishers, 2001,pp: 135-205.
[4] R. Mohan Mathur, Rajiv K. Varma, “Thyristor-Based
FACTS Controllers For Electrical Transmission Systems”,
IEEE press series on power engineering, John Wiley & sons
publishers,2002, pp: 413-457
[5]A. Ghosh and G. Ledwich; “Power Quality enhancement
using custompower devices,” Kluwer Academic Publishers,
Boston, 2002
[6] H. Akagi, Y. Kanazawa, and A. Nabae, “Instantaneous
reactive power compensators comprising switchingdevices
without energy storage components,” IEEE Trans. on Ind.
Appl. Vol. 20, no. 3, 625-630, 1984.
[7] F. Z. Peng and J. S. Lai, “Generalized instantaneous
reactive power theory for three-phase powersystems,”IEEE
Trans. on Instrumentation and Measurement. Vol. 45, no. 1,
293-297, 1996
[8] H. Kim, F. Blaabjerg, B. B. Jemsen and J. Choi,
“Instantaneous power compensationinthree-phasesystems
by using p-q-r theory,” IEEE Trans. on Power Electronics,
Vol. 17, no 5, 701-709, 2002.
[9] A. Ghosh and A. Joshi, “A new approach to load balancing
and power factor correction in power distribution system,”
IEEE TranS.onPowerDelivery,Vol.15,no1pp.417-422,2000.

IRJET - Design and Simulation of DSTATCOM using Fuzzy Logic Controller

More Related Content

What's hot (18)

Similar to IRJET - Design and Simulation of DSTATCOM using Fuzzy Logic Controller (20)

More from IRJET Journal (20)

Recently uploaded (20)

IRJET - Design and Simulation of DSTATCOM using Fuzzy Logic Controller