UDAY PPT

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INSTANTANEOUS POWERINSTANTANEOUS POWERCONTROL OF D-STATCOMCONTROL OF D-STATCOMWITH CONSIDERATION OFWITH CONSIDERATION OF

POWER FACTORPOWER FACTORCORRECTIONCORRECTION Internal Guide

Mr RK.REDDY

Associate Professor

ByY.UDAYKIRAN

10C91D0718

M.Tech., EEE



OVERVIEWOVERVIEW Electric power distribution network have become moreElectric power distribution network have become more

increasingly important and plays an essential role in power increasingly important and plays an essential role in power

system planning.system planning. This type of power systems has a major function to serveThis type of power systems has a major function to serve

distributed customer loads along a feeder line; thereforedistributed customer loads along a feeder line; thereforeunder competitive environment of electricity market serviceunder competitive environment of electricity market serviceof electric energy transfer must not be interrupted and at theof electric energy transfer must not be interrupted and at thesame time there must provide reliable, stable and high qualitysame time there must provide reliable, stable and high qualityof electric power.of electric power.

To complete this challenge, it requires careful design for To complete this challenge, it requires careful design for power network planning. There exist many different ways to power network planning. There exist many different ways to

do so. However, one might consider an additional device todo so. However, one might consider an additional device to be installed somewhere in the network. be installed somewhere in the network.

Such devices are one of capacitor bank, shunt reactor, seriesSuch devices are one of capacitor bank, shunt reactor, series

reactors, automatic voltage regulators and recently developedreactors, automatic voltage regulators and recently developed

dynamic voltage restorers, distribution static compensator dynamic voltage restorers, distribution static compensator



BLOCK DIAGRAM OF IUPQCBLOCK DIAGRAM OF IUPQC



Block Diagram of IUPQCBlock Diagram of IUPQC

cont’dcont’d



OBJECTIVEOBJECTIVE

To regulate the bus voltage to which unbalanced load

and Non-Linear load are connected against sag/swell

and or disturbances in the system.

To protect the sensitive load from the disturbances

occurring in the system by regulating the voltage .



INTRODUCTIONINTRODUCTION

Def of Power qualityDef of Power quality

Voltage quality:Voltage quality:

Voltage quality is concerned with the deviation of actual voltage from idealVoltage quality is concerned with the deviation of actual voltage from ideal

voltagevoltage.. Current quality:Current quality:

current quality is concerned with the deviation of actual current from ideal voltage.current quality is concerned with the deviation of actual current from ideal voltage. Power quality- voltage as well as current should bePower quality- voltage as well as current should be

maintainedmaintained

Any deviation of voltage or current from the ideal is aAny deviation of voltage or current from the ideal is a

power quality disturbance. power quality disturbance.



Power Quality ProblemsPower Quality Problems

SagsSags

SwellsSwells

Voltage InterruptionVoltage Interruption Voltage Flicker Voltage Flicker

HarmonicsHarmonics

Voltage NotchingVoltage Notching



Power Quality Problems Cont’dPower Quality Problems Cont’d

Voltage SagVoltage Sag

Voltage sag is defined as a sudden reduction of supplyvoltage down 90% to 10% of nominal, followed by

a recovery after a short period of time which can causewhich can cause

damage and loss of production especially in industrial sector.damage and loss of production especially in industrial sector.

Voltage SwellVoltage Swell

Voltage swell, , is defined as a sudden increasing of

supply voltage up 110% to 180% in rms voltage at

the network fundamental frequency with duration from

10 ms to 1 minute Caused by system faults, load switching and capacitor Caused by system faults, load switching and capacitor

switching.switching. Voltage InterruptionVoltage Interruption

AA voltage interruptionvoltage interruption is the complete loss of electric voltage.is the complete loss of electric voltage.

Interruptions can be short duration (lasting less than 2 minutes)Interruptions can be short duration (lasting less than 2 minutes)

or long duration. A disconnection of electricity causes an interruption—usually byor long duration. A disconnection of electricity causes an interruption—usually by

the opening of a circuit breaker, fuse,the opening of a circuit breaker, fuse, power system faults, equipment failures,



Voltage FlickerVoltage Flicker A very rapid change in supply voltage is calledA very rapid change in supply voltage is called voltage flicker voltage flicker ..

This is caused by rapid variations in current magnitude of loads such as arc furnacesThis is caused by rapid variations in current magnitude of loads such as arc furnacesin which a large inrush current flows when the arc strikes first causing a dip in thein which a large inrush current flows when the arc strikes first causing a dip in the

bus voltage. bus voltage.

These variations are usually caused by rapid changes in load connected to the system.These variations are usually caused by rapid changes in load connected to the system.

Flicker problems can be corrected with the installation of filters, static VAR systems,Flicker problems can be corrected with the installation of filters, static VAR systems,or distribution static compensatorsor distribution static compensators

The maximum tolerable variation in supply frequency is often limited within + or – The maximum tolerable variation in supply frequency is often limited within + or –

0.5 Hz from the nominal frequency of 50 or 60 Hz.0.5 Hz from the nominal frequency of 50 or 60 Hz.


Example voltage waveforms showing flicker created by an arc furnace



Power System Harmonics Harmonic: Harmonics are components that make up a waveform where each

component has frequency that is an integer multiple of the fundamental frequency

Harmonic is applied to waveform components that have frequencies other thanHarmonic is applied to waveform components that have frequencies other than

fundamental frequency.fundamental frequency.

Power system harmonics: currents or voltages with frequencies that are integer

multiples (h=0,1,2,…N) of the fundamental power frequency

1st harmonic: 60Hz

2nd harmonic: 120Hz

3rd harmonic: 180Hz




How are Harmonics Produced ?

Power system harmonics: presenting deviations from a perfect sinusoidal-waveform ((voltage or current waveform).

The distortion comes from a Nonlinearity .




Why Bother about Harmonics?

50-60% of all electrical Ac Systems operate with non-linear type loads. Exponential Growth of Non-Linear Load over last decade

• Industrial, Commercial & Residential Power-Quality Problems Damage to Power Factor Correction capacitors Waveform Distortion can create

SAG/SWELL/NOTCHING/…

All can cause damage effects to consumer loads and power systems due to Over-Current/Over-Voltage or Waveform Distortion

Additional Power/Energy Losses




Distorted VoltageDistorted Voltage

WaveformsWaveforms

Solutions to problems caused by harmonic distortionSolutions to problems caused by harmonic distortion

include installing active or passive filters at the load orinclude installing active or passive filters at the load or

bus.bus.




Voltage NotchingVoltage Notching Voltage notching is caused by the commutation of power electronic rectifiers. ItVoltage notching is caused by the commutation of power electronic rectifiers. It

is an effect that can raise PQ issues in any facility where solid-state rectifiersis an effect that can raise PQ issues in any facility where solid-state rectifiers(for example, variable-speed drives) are used.(for example, variable-speed drives) are used.

When the drive DC link current is commutated from one rectifier thyristor to theWhen the drive DC link current is commutated from one rectifier thyristor to thenext, an instant exists during which a line-to-line short circuit occurs at the inputnext, an instant exists during which a line-to-line short circuit occurs at the input

terminals to the rectifier.terminals to the rectifier.

With this disturbance, any given phase voltage waveform will typically containWith this disturbance, any given phase voltage waveform will typically containfour notches per cycle as caused by a six-pulse electronic rectifier four notches per cycle as caused by a six-pulse electronic rectifier




Sources of Power QualitySources of Power Quality

ProblemsProblems Power electronic devicesPower electronic devices IT and office equipmentsIT and office equipments Arching devicesArching devices Load switchingLoad switching Large motor startingLarge motor starting Sensitive equipmentSensitive equipment Storm and environmental relatedStorm and environmental related

damagedamage Ca acitor switchingCapacitor switching

power quality problems cont’dpower quality problems cont’d



Why is Power QualityWhy is Power Quality

Important?Important?

It affects both utilities asIt affects both utilities as

suppliers andsuppliers andcustomers as userscustomers as users




Impact on Customer SideImpact on Customer Side Computers and communication equipment are susceptible toComputers and communication equipment are susceptible to

power system disturbances which can lead to loss of data and power system disturbances which can lead to loss of data and

erratic operation.erratic operation.

Automated manufacturing processes such as paper-makingAutomated manufacturing processes such as paper-making

machinery, chip-making assembly lines, etc. can shutdown inmachinery, chip-making assembly lines, etc. can shutdown incase of even short voltage sags.case of even short voltage sags.

Induction and synchronous motors can have excessive lossesInduction and synchronous motors can have excessive losses

and heating.and heating.

Equipment and process control malfunction translates to dollarsEquipment and process control malfunction translates to dollarsof expense for replacement parts and for down time, impactingof expense for replacement parts and for down time, impacting

adversely on profitability and product quality.adversely on profitability and product quality.




Impact on Utility SideImpact on Utility Side

Failure of power-factor correction capacitors due to resonanceFailure of power-factor correction capacitors due to resonance

conditions.conditions.

Increased losses in cables, transformers and conductors,Increased losses in cables, transformers and conductors,especially neutral wires.especially neutral wires.

Errors in energy meters, which are calibrated to operate under Errors in energy meters, which are calibrated to operate under

sinusoidal conditions.sinusoidal conditions.

Incorrect operation of protective relays, particularly in solid-Incorrect operation of protective relays, particularly in solid-state and microprocessor-controlled systems.state and microprocessor-controlled systems.

Unhappy customers as well as malfunction and failure of Unhappy customers as well as malfunction and failure of

system components and control systems, impacting adverselysystem components and control systems, impacting adversely

on profitabilityon profitability..




Focus on Three Aspects of Focus on Three Aspects of Power QualityPower Quality

HarmonicsHarmonics

UnbalanceUnbalance

Voltage SagsVoltage Sags




..

Electric Power QualityElectric Power Quality

Mitigation Techniques Mitigation Techniques

to Improve Power Qualityto Improve Power Quality



Possible SolutionsPossible Solutions Proper earthing practicesProper earthing practices

Online UPS/Hybrid UPSOnline UPS/Hybrid UPS

Energy storage systemEnergy storage system Ferro- resonant transformerFerro- resonant transformer

Network equipment and designNetwork equipment and design

Static Transfer SwitchesStatic Transfer Switches

Static Var CompensatorStatic Var Compensator

Uninterruptible Power SupplyUninterruptible Power Supply

Electric Power QualityElectric Power Quality Mitigation Techniques to Improve Power quality Mitigation Techniques to Improve Power quality



FACTS and Custom Power DevicesFACTS and Custom Power Devices

The other families of power electronic devices, veryThe other families of power electronic devices, very

closely related to the active filtersclosely related to the active filters, are, are Flexible AC Transmission System (FACTS) devices,Flexible AC Transmission System (FACTS) devices,

Custom Power Devices.Custom Power Devices. FACTS devices are intended for FACTS devices are intended for

greater control of power transmission,greater control of power transmission,

maximize utilization of existing transmission lines,maximize utilization of existing transmission lines,

reduction of generation reserve margin,reduction of generation reserve margin,

prevention of cascading outages, prevention of cascading outages,

damping of power system oscillationsdamping of power system oscillations..

Mitigation Techniques to Improve Power quality cont’d Mitigation Techniques to Improve Power quality cont’d



FAULTSFAULTS

Short circuit

(or)

Shunt fault

open circuit

(or) series fault



Distribution Static Compensator

(DSTATCOM )


The STATCOM, when used in low-voltage distribution

systems is normally identified as Distribution STATCOM

(D-STATCOM).

It consists of a two level VSC, a dc energy storage

device; a coupling transformer connected in shuntwith the ac system, and associated control circuits.

The static synchronous compensator (STATCOM) is a power electronic based

synchronous voltage generator that generates a three-phase voltage from a DC

capacitor.

The active power flow is controlled by the angle between the ac system and

VSC voltages and the reactive power flow is controlled by the difference

between the magnitudes of these voltages .

..



Dynamic Voltage RestorerDynamic Voltage Restorer

(DVR(DVR))

DVR is a series compensator which is able to protect a sensitive load from thedistortion in the supply side during fault or overloaded in power system.

The basic principle of a series compensator is simple, by inserting a voltage of required magnitude and frequency, the series compensator can restore the load sidevoltage to the desired amplitude and waveform even when the source voltage isunbalanced or distorted.


The DVR consists of a VSC, a switchingcontrol scheme, a DC energy storage

device and a coupling transformer similar toD-STATCOM, but here the couplingtransformer is connected in series with the

ac system.




The DVR can generate or absorb independently controllable real and

reactive power at the load side. The DVR also is made of a solid state dc to

ac switching power converter that injects a set of three phase ac output

voltages in series and synchronism with the distribution feeder voltages .

The amplitude and phase angle of the injected voltages are variable thereby

allowing control of the real and reactive power exchange between the DVR

and the distribution system ..

Functions: Reactive Power Compensation

Voltage Regulation Compensation for Voltage sag and Swell

Unbalance Voltage Compensation (for 3-phase systems)

Dynamic Voltage Restorer (DVR)Dynamic Voltage Restorer (DVR)



Unified Power QualityUnified Power QualityConditioner (UPQC)Conditioner (UPQC)

Functions

Reactive Power Compensation

Voltage Regulation

Compensation for Voltage sag and swell

Unbalance Compensation for current and

voltage (for 3-phase systems)



InterlineInterline Unified Power Quality Conditioner cont’dUnified Power Quality Conditioner cont’d

..

Single-line diagram of an IUPQC-connected distribution systemSingle-line diagram of an IUPQC-connected distribution system..



BLOCK DIAGRAM OFBLOCK DIAGRAM OF

IUPQCIUPQC




Main parts in IUPQCMain parts in IUPQC

Shunt connected voltage source converter(D-STATCOM)

Series connected voltage source converter

(DVR)

Energy storage DC capacitor

Feeder 1 containingFeeder 1 containing

Unbalanced loadUnbalanced loadNon-Linear loadNon-Linear load

Feeder 2 containingFeeder 2 containing

Sensitive LoadSensitive Load




Schematic structure of a VSSchematic structure of a VSC


Each of the two VSCs is realized bythree H-bridge inverters.

In this structure, each switch

represents a power semiconductor

device and an anti-parallel diode .

All the inverters are supplied from a

common single dc capacitor and each

inverter has a transformer connected

at its output.

Features of vscFeatures of vsc

OPERATION :The Inverter is supplied by a dc source with a voltage of Vdc .

The switches of each leg have complementary values,

e.g. when S1 is ON,S4 is OFF and vice versa.

when S1 &S2 ON ,S3 & S4 OFF

when S3 & S4 ON, S1 &S2 OFF



Function of VSCFunction of VSC

A voltage-source converter is a power electronic device, whichcan 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 ‘missing voltage’. The ‘missing voltage’ is thedifference between the nominal voltage and the actual.

The converter is normally based on some kind of energystorage, which will supply the converter with a DC voltage.

The solid-state electronics in the converter is then switched toget the desired output voltage. Normally the VSC is not onlyused for voltage dip mitigation, but also for other power qualityissues, e.g. flicker and harmonics.




Complete structure of anComplete structure of an

IUPQCIUPQC

..




Description of Description of complete structure of a three-phase IUPQC The complete structure of a three-phase IUPQC consists of two

VSCs .

The secondary (distribution) sides of the shunt-connectedtransformers (VSC-1) are connected in star with the neutral

point being connected to the load neutral.

The secondary winding of the series-connected transformers

(VSC-2) are directly connected in series with the bus (B-2) and

sensitive load (L-2).

The ac filter capacitors also connected in each phase to prevent the flow of the harmonic currents generated due toswitching.

The six inverters of the IUPQC are controlled independently.


I liI t li U ifi d P Q li C di i ’dU ifi d P Q lit C diti t’d



PWM CONTROL SCHEME PWM-based control scheme with reference to the

D-STATCOM and DVR

The aim of the control scheme is to maintain constant voltagemagnitude at the point where a sensitive load is connected,under system disturbances. The control system only measures

the rms voltage at the load point.

The VSC switching strategy is based on a sinusoidal PWM technique which offers simplicity and good response.

Besides, high switching frequencies can be used to improve onthe efficiency of the converter, without incurring significantswitching losses.


mu n oc agram omu n oc agram o



mu n oc agram omu n oc agram oIUPQCIUPQC



Structure of Shunt connectedStructure of Shunt connected

V V 1VSC VSC1

Simulink block Diagram of IUPQC cont’dSimulink block Diagram of IUPQC cont’d



Structure of Series connectedStructure of Series connectedVSC VSC2VSC(VSC2)

Simulink block Diagram of IUPQC cont’dSimulink block Diagram of IUPQC cont’d



Simulation ResultsSimulation Results

Voltages and currentsVoltages and currents

With and withoutWith and without

IUPQCIUPQC



..

Bus voltage toBus voltage to which unbalanced loads connectedwhich unbalanced loads connected with IUPQCwith IUPQC

Vabc_b21Vabc_b21

Bus voltage to which unbalanced loads connected without IUPQCBus voltage to which unbalanced loads connected without IUPQC Vabc_b21Vabc_b21

U b l d L d L 11 l d I b b31U b l d L d L 11 l d t I b b31 i h IUQCith t IUQC



Unbalanced Load L-11 load currents Iabc_b31Unbalanced Load L-11 load currents Iabc_b31 without IUQCwithout IUQC

Non Linear Load L-12 load currents Iabc_b41Non Linear Load L-12 load currents Iabc_b41 without IUPQCwithout IUPQC

Feeder-1 currents Iabc_b21Feeder-1 currents Iabc_b21 with IUPQCwith IUPQC



TRANSIENT PERFORMANCE OFTRANSIENT PERFORMANCE OF

IUPQCIUPQC

The performance of IUPQC has been The performance of IUPQC has been

evaluated considering various disturbanceevaluated considering various disturbanceconditions likeconditions like

voltage sag in feeder1 ,voltage sag in feeder1 ,

voltage sag in feeder2,voltage sag in feeder2,Faults(L-G,L-L-G,Three phase) inFaults(L-G,L-L-G,Three phase) in

feeder2feeder2



System response duringSystem response during

voltage sag in Feeder-1voltage sag in Feeder-1

without and with IUPQCwithout and with IUPQC

..

Voltage at the bus to which unbalanced load is connected Vabc b31Voltage at the bus to which unbalanced load is connected Vabc b31



Voltage at the bus to which unbalanced load is connected Vabc_b31Voltage at the bus to which unbalanced load is connected Vabc_b31

without IUPQCwithout IUPQC

With IUPQCWith IUPQC



Voltage at the bus to which Non linear load is connected Vabc_b41Voltage at the bus to which Non linear load is connected Vabc_b41



F d 1F d 1 t I b b21I b b21



Feeder-1 current Feeder-1 current Iabc_b21Iabc_b21





System parametersSystem parameters

..



..

The performance under some of the major

concerns of both customer and utility e.g.,

harmonic contents in loads, unbalancedloads, supply voltage distortion, systemdisturbances such as voltage sag, swelland fault has been studied.

The IUPQC has been shown to compensatefor several of these events successfully

conclusionsonclusions

Reference PapersReference Papers



Reference PapersReference Papers G. Ledwich and A. Ghosh, “A flexible DSTATCOM

operating in voltage and current control mode,” Proc.Inst. Elect. Eng., Gen.,Transm. Distrib., vol. 149, no.

2, pp. 215–224, 2002 M. K. Mishra, A. Ghosh, and A. Joshi, “Operation of a

DSTATCOM in voltage control mode,” IEEE Trans.Power Del., vol. 18, no. 1, pp.258–264, Jan. 2003.

N. H. Woodley, L. Morgan, and A. Sundaram,“Experience with an inverter-based dynamicvoltage restorer,” IEEE Trans. Power Del.,vol. 14, no. 3, pp. 1181–1186, Jul. 1999.

A. Ghosh, A. K. Jindal, and A. Joshi, “Designof a capacitor-supported Dynamic VoltageRestorer (DVR) for unbalanced and distortedloads,” IEEE Trans. Power Del., vol. 19, no. 1,pp. 405–413, Jan. 2004.

R fR f



Reference papersReference paperscontd….contd….

H. Fujita and H. Akagi, “ The unified power qualityconditioner: the integration of series- and shunt-activefilters,” IEEE Trans. Power Electron., vol. 13, no. 2, pp. 315–322, Mar. 1998.

F. Kamran and T. G. Habetler, “Combined deadbeatcontrol of a series parallel converter combinationused as a universal power filter,” IEEE Trans. Power Electron., vol. 13, no. 1, pp. 160–168, Jan. 1998.



Text BooksText Books

Power Quality in Power systems andPower Quality in Power systems and

Electrical Machines-Electrical Machines- Ewald F.FuchsEwald F.Fuchs

and A.S.Masoumand A.S.Masoum Power quality enhancement usingPower quality enhancement using

custom power devices-custom power devices-

Amit Kumar Jindal, Student Member, IEEE,Arindam Ghosh, Fellow, IEEE, and Avinash Joshi



..

THANK YOU THANK YOU

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UDAY PPT