lalu document

8/17/2019 Lalu Document

1/53

SAG AND SWELL MITIGATION BY USING DISTRIBUTED POWER FLOWCONTROLLER

CHAPTER-1

ELECTRIC POWER QUALITY

1.1 Introduction

In the last decade, the electrical power quality issue has been the main concern

of the power companies. Power quality is defined as the index which both the delivery and

consumption of electric power affect on the performance of electrical apparatus. From a

customer point of view, a power quality problem can be defined as any problem is manifested

on voltage, current, or frequency deviation that results in power failure. The power electronics

progressive, especially in flexible alternating-current transmission system F!"T#$ and

custom power devices, affects power quality improvement. %enerally, custom power devices,

e.g., dynamic voltage restorer &'($, are used in medium-to-low voltage levels to improve

customer power quality .

)ost serious threats for sensitive equipment in electrical grids are voltage sags voltage dip$

and swells over voltage$ . These disturbances occur due to some events, e.g., short circuit in

the grid, inrush currents involved with the starting of large machines, or switching operations

in the grid. The F!"T# devices, such as unified power flow controller *PF"$ and

synchronous static compensator #T!T-"+)$, are used to alleviate the disturbance and

improve the power system quality and reliability. In this paper, a distributed power flow

controller, introduced in as a new F!"T# device, is used to mitigate voltage and current

waveform deviation and improve power quality in a matter of seconds.

1.2 Impacts o po!"r #ua$it% pro&$"ms on "nd us"rs

The causes of power quality problems are generally complex and difficult to detect.

Technically speaing, the ideal ac line supply by the utility system should be a pure sine wave

of fundamental frequency. In addition, the pea of the voltage should be of rated value.

*nfortunately the actual ac line supply that we receive everyday departs from the ideal

specifications. Table . lists various power quality problems, their characteriation methods

and possible causes.

Dept. of EEE Page 1 /swar "ollege of /ngineering


2/53


Ta&$" 1.1 po!"r #ua$it% pro&$"ms and t'"ir caus"s



3/53


.


0road

categories

#pecific

categories

)ethods of

"haracteriatio

n

Typical causes

Transients

Impulsive

+scillatory

Peamagnitude,

Time and

duration

Pea

magnitude,

Frequency

components

1ightning strie,Transformer energiation,

"apacitor switching

1ine or capacitor

+r load switching.

#hort duration

'oltage

variation

#ag

#well

Interruption

)agnitude,

duration

)agnitude,

duration

duration

Ferroresonant

transformers,

#ingle line to ground

faults

Ferroresonant

transformers,

#ingle line to ground

faults

Temporary faults

1ong duration

voltage

variations

*nder voltage

+vervoltage

#ustained

interruptions

)agnitude,

duration

)agnitude,

duration

&uration

#witching on loads,

capacitor deenergiation

#witching off loads,

"apacitor energiation

faults

'oltage

imbalance

#ymmetrical

components

#ingle-phase loads,

single-phasing condition

2aveform

distortion

3armonics

4otching

&" offset

T3&, harmonic

#pectrum

T3& , harmonic

#pectrum

'olts, amps

!d5ustable speed

&rives and other

nonlinear loads

Power electronic

"onverters

%eo-magnetic

disturbance,3alf-wave rectification

'oltage flicer Frequency of

+ccurrence,

)odeling

frequency

!rc furnace, arc

1amps


4/53


There are many ways in which the lac of quality power affects customers. Impulsive

transients do not travel very far from their point of entry. 3owever an impulsive transient can

give rise to an oscillatory transient can lead to transient over voltage and consequent damage

to the power line insulators.

#hort duration voltage variations have varied effects on consumers. 'oltage sag can

cause loss of production in automated process. #ince a voltage sag can trip a motor or cause its

controller to malfunction. also voltage swells can put stress on computers and many home

appliances.

1.( Cat")ori"s or po!"r #ua$it% *ariation

The impact of long duration voltage variations is greater than those of short

duration variations. The under voltage effects same as voltage sag and over voltage effects

same as voltage swell. The recent proliferation of electronic equipment and microprocessor-

based controls has caused electric utilities to redefine power quality in terms of the quality of

voltage supply rather than availability of power. In this regard, I/// #td. 67-776,

Recommended Practice for Monitoring Electric Power Quality as created categories of

power quality disturbances based upon duration, magnitude, and spectral content. Table 8-

shows the categories of power quality disturbances with spectral content, typical duration,

and typical magnitude.

Dept. of EEE Page /swar "ollege of /ngineering


5/53


Ta&$" 1.2 Cat")ori"s o Po!"r Qua$it% +ariation , IEEE 11-1

/p"ctra$ T%pica$

Cat")ori"s Cont"nt 0a)nitud"s

1. Transi"nts

. Impulsive 9 6 3.. 'oltage

..8 "urrent 9 6 3

.8 +scillatory

: 6;; 3.8. 1ow Frequency

.8.8 )edium Frequency


6/53


VoltageSags, Swells and Interruptions

Table .8 shows typical voltage sag, swell, and interruption. 'oltage sag is a short-

duration decrease of the ()# voltage value, lasting from ;.6 cycles to 8; seconds. #ags are

caused by faults on the power system or by the starting of are relatively large motor or other

large load. ! voltage swells may accompany voltage sag.

! voltage swell occurs when a single line-to-ground fault on the system results in a

temporary voltage rise on the *n faulted phases. (emoving a large load or adding a large

capacitor ban can also cause voltage swells, but these events tend to cause longer-duration

changes in the voltage magnitude and will usually be classified as long-duration variations

! voltage interruption is the complete loss of voltage. ! disconnection of electricity

causes an interruption, usually by the opening of circuit breaer, liner closer, or fuse. For

example, if a tree comes into contact with an overhead electricity line, a circuit breaer will

clear the fault short circuit$, and the customer who receives their power from the faulted

line will experience an interruption.

7i). 1.1 T%pica$ /'ort uration R0/ +o$ta)" +ariation

1.3 POWER QUALITY /TA5AR/

%eneva based international electro technical commission I/"$ and institute of

electrical and electronics engineers proposed various standards for power quality. The table

is shown below.

Dept. of EEE Page " /swar "ollege of /ngineering


7/53


Ta&$" 1.( po!"r #ua$it% standards

Dept. of EEE Page # /swar "ollege of /ngineering

Phenomena #tandards

"lassification of power quality I/" B;;;-8-6C776 D8E,

I/" B;;;-8-C77; DE

'oltage flicer I/" B;;;-?-6C 77AD7E


8/53

FACT$ %o&t'o((e'$

MEC)ANICAL PFCD$Po*e' e(e%t'o&+% PFCD$

T,-'+$t'o(tage $o/'%e %o&0e'te'

S,/&t L C

e0+%e$

45

SC SSC

44 Ot,e'$6 )DC DR

7Se'+e$ L C TCSC

e0+%e$

8

Stat+% $-&%,'o&o/$ $e'+e$ %o9pe&$ato'

Co9:+&e e0+%e$P,a$e $,+ft+&g T;f

<

U&+=e; +&te'(+&e po*e' >o* %o&t'o((e'


CHAPTER-2

7ACT/ E+ICE/

2.1 ROLE O7 7ACT/ E+ICE/

Flexible !lternating "urrent Transmission #ystems F!"T#$ devices have been

proposed for effective power flow control and regulating bus voltage in electrical power

systems, thus resulting in an increased transfer capability, low system losses and improved

stability.

)ost serious threats for sensitive equipment in electrical grids are voltage sagsvoltage

dip$ and swells over voltage$ . These disturbances occur due to some events, e.g., short circuit

in the grid, inrush currents involved with the starting of large machines, or switching operations

in the grid.

2.2 Cat")ori:ation o P7Cs

7i) 2.1 cat")ori:ation o P7Cs

Dept. of EEE Page ? /swar "ollege of /ngineering


9/53


;a< /'unt 7ACT/ Contro$$"r= The shunt controllers are connected in parallel with the

transmission line. They in5ect the voltage and current in parallel with the transmission

system.

i$ /tatic /%nc'ronous Comp"nsator= !ccording to I/// definitions and standards, a

static synchronous generator operated as a shunt connected static var compensator

whose capacitive or inductive op current can be controlled independent of ac system

voltage.

! three-level voltage inverter based dynamic model of T!T"+) has been

established by way of lead-in switch function and using P2) current control technology for

realiing dynamic var compensation effectively.

! three-leg voltage source inverter '#I$ configuration with a dc bus capacitor as a

T!T"+) has been demonstrated through )!T1!0#I)*1I4G for power quality

improvement in a three-phase, three-wire distribution system .

&ifferent control strategies have been employed and compared lie hysteresis control,

P2) current controllers, PI controller and sliding mode controller.

In order to balance the supply current, and improving the power factor to a desired

value the theory of instantaneous symmetrical components has been used here to extract the

three-phase reference currents and then these reference currents are then traced using voltage

source inverter '#I$, operated in a hysteresis band control technique .

These disturbances occur due to some events, e.g., short circuit in the grid, inrush

currents involved with the starting of large machines, or switching operations in the grid.

The nonlinear state-space model of the multilevel T!T"+) has been presented

from the dq; reference frame that can adapt to load changes and have effective steady-state

compensation and a better dynamic response .

Dept. of EEE Page @ /swar "ollege of /ngineering


10/53


!ccording to I/// definitions and standards, a static synchronous generator or

dynamic voltage restorer operated without an external electrical energy source or a series

compensator where op voltage is in quadrature and controllable independently of the line

current for the purpose of increasing or decreasing the overall reactive voltage drop across the

line and there by controlling the transmitted electric power. ###" is also nown as dynamic

voltage restorer.



11/53


! #tatic synchronous "ompensator #T!T"+)$ as shown in Fig. 8 emulates an

inductive or a capacitive reactance at the point of connection with the transmission line by

in5ecting sinusoidal current, of variable magnitude, at the point of connection in quadrature

with the line voltage. The line voltage regulation can be achieved by regulating the reactive

current flow through #T!T"+) which has been verified by the modeling technique of

#T!T"+) using an /lectromagnetic Transients Program /)TP$ simulation pacage D7E.

&istribution static compensator T!T"+)$ is used in distribution system for the

compensation of reactive power and unbalance caused by various loads and it wors on the

principle of '#" voltage source converter$. To compensate the reactive power a current

in5ected into the system by &-#T!T"+) to correct the voltage sag, swell and interruption.

T!T"+) is shown below in Fig.


12/53


improving the power quality of power systems dynamic modeling and the control design of a

distribution static compensator coupled with ultra-capacitor energy storage *"/#$ has also

been proposed and the control technique employed is based on the instantaneous power theory

on the synchronous-rotating dq reference frame. Three modes of operation have been

considered, i.e. voltage control for voltage fluctuations ride-through, currentvoltage harmonics

mitigation and dynamic active power control.

! mathematical model of T!T"+) in voltage sag compensation mode along with

#'P2) switched T!T"+) simulation in power factor control mode has been presented

for power factor and voltage sag compensation. T!T"+) can also be applied to industrial

systems for mitigation of voltage dip problem which generally occurs during the starting of an

induction motor. The distribution system performance under all types of fault can be improved

by using a 8-pulse T!T"+) configuration with I%0T which can be modeled and

simulated using the P#"!&/)T&". ! T!T"+) can also be applied in three-phase, four-

wire distribution system feeding commercial and domestic consumers for load balancing,

neutral current elimination, power factor correction and voltage regulationTo maintain voltage

stability and improve power quality of distribution grid, a control strategy combining control of

state feedbac and feed forward has been employed using a nonlinear dynamic mathematical

model of T!T"+) and thus improving the transient response performance and anti-disturbing ability of the system .

! three-level voltage inverter based dynamic model of T!T"+) has been

established by way of lead-in switch function and using P2) current control technology for

realiing dynamic var compensation effectively. ! three-leg voltage source inverter '#I$

configuration with a dc bus capacitor as a T!T"+) has been demonstrated through

)!T1!0#I)*1I4G for power quality improvement in a three-phase, three-wire distribution

system . &ifferent control strategies have been employed and compared lie hysteresis control,

P2) current controllers, PI controller and sliding mode controller.

In order to balance the supply current, and improving the power factor to a desired

value the theory of instantaneous symmetrical components has been used here to extract the

three-phase reference currents and then these reference currents are then traced using voltage

source inverter '#I$, operated in a hysteresis band control technique . The nonlinear state-

space model of the multilevel T!T"+) has been presented from the dq; reference frame

that can adapt to load changes and have effective steady-state compensation and a better

dynamic response .



13/53


;ii< /tatic +AR Comp"nsator= !ccording to I/// definitions and standards, a shunt connected

static '!( generator or absorber whose output is ad5usted to exchange capacitive or inductive current so

as to maintain or control specific parameters of the electrical power system.

.

#tatic '!( compensator #'"$ can be seen in Fig. ?. ! comparative power flow study

using #'" and #T!T"+) models on I/// ?-0us Test 4etwor has been carried out and it

has been shown that in both cases, the state variables of #'" and #T!T"+) have been

combined with the bus voltage magnitudes and the angles of the networ for 4ewton Power

flow solution for achieving power quality and stability

;&< /"ri"s 7ACT/ Contro$$"r= These controllers are connected in series with the

transmission line and they in5ect the voltage and current in series with the transmission system..

;i< /tatic /%nc'ronous /"ri"s Comp"nsatorC

!ccording to I/// definitions and standards, a static synchronous generator or dynamic

voltage restorer operated without an external electrical energy source or a series compensator

where op voltage is in quadrature and controllable independently of the line current for the

purpose of increasing or decreasing the overall reactive voltage drop across the line and there



14/53


by controlling the transmitted electric power. ###" is also nown as dynamic voltage

restorer. The &'( was first installed in 77B and is shown in Fig. 6.

&'( is useful for compensating voltage quality problems that are due to voltage sag.

&ue to its excellent dynamic capabilities, it is well suited to protect critical or sensitive load

from short duration voltage dips or swells. 2hen a fault occurs in a distribution networ, a

sudden voltage dip will appear on ad5acent load feeders. 2ith a &'( installed on a critical

load feeder, the line voltage is restored to its nominal value within the response time of a few

milliseconds thus avoiding any power disruption to the load.

&'( protects loads against voltage sags by series in5ection of the missing portion of the

utility voltage. To obtain missing voltage the distorted source voltage is compared with its

pre-fault value to generate the control signal for P2). The sie and rating of &'( depend

on its capability in supplying or absorbing real power in the steady-state .

&ynamic 'oltage (estorer &'($ is normally installed in a distribution system between

the supply and the critical load feeder. Its primary function is to rapidly boost up the load-

side voltage in the event of a disturbance in order to avoid any power disruption to that load.

There are various circuit topologies and control schemes that can be used to implement a

&'(.

To compensate the voltage deviation caused in a feeder the Interline &'( I&'($

operated by )ultiple Pulse 2idth )odulation P2)$ has been proposed which consists



15/53


several &'(s connected to different distribution feeders in the power system sharing

common energy storage. +ne &'( in the I&'( system wors in voltage-sagswell

compensation mode while the other &'( in the I&'( system operate in power-flow control

mode.

%!-based optimiation can be used for the location, the type and the rating of the various

F!"T# devices lie static var compensator, static compensator, and dynamic voltage restorer

and the performance of the proposed algorithm has been tested and illustrated on 876-bus

generic distribution system.

! schematic diagram of I&'( has been shown in Fig. B

! concept of interline dynam

i

c voltage restoration I&'($ has been proposed in which several &'(s in different feeders

are connected to a common &"-lin energy storage and thus reducing the cost of installation.

For both the voltage control and the power flow control modes a closed-loop controller that

consists of an inner current loop and an outer voltage loop has been incorporated into the

I&'( system.

Dept. of EEE Page 1! /swar "ollege of /ngineering


16/53


;ii< T'%ristor Contro$$"d /"ri"s Capacitor= !ccording to I/// definitions and

standards, a capacitive reactance compensator which consists of series capacitor ban

shunted by thyristor controlled reactor in order to provide a smoothly variable series

capacitive reactance. Fig. A shows a Thyristor "ontrolled #eries "apacitor

Thyristor "ontrolled #eries "apacitor T"#"$ has been modeled in a simple two bus

system with distributed parameter line. ! Fuy logic controller and a PI& controller have been

used to control firing angles of T"#" but it has been verified that the fuy logic controller can

generate better dynamic response

. ! single-machine infinite-bus power system installed with a T"#" has been proposed

whose control parameters have been optimied using genetic algorithm. The modeling and

simulation have validated the effectiveness of the proposed approach to achieve system

stability.

The T"#" controller can provide a very fast action to increase the synchroniation

power by quic change in the equivalent capacitive reactance to the full compensation during a

fault. The T"#" controller can be designed to control the power flow, to increase the transfer

limits or to improve the transient stability and damping the oscillations F!"T# devices such as

thyristor controlled series capacitors are difficult to model due to their nonlinear switching

behavior. It has been shown that passive damping has a significant effect on modal damping.

!s compared to the traditional control devices, the T"#" offers smooth and flexible

control of the line impedance with much faster response. The 4ewton-(aphson ac power flow

method has been used to perform the modeling of T"#" for power flow studies. The

performance of the proposed algorithm has been tested on I///-


17/53


;c< Com&in"d s"ri"s-s"ri"s contro$$"rs= These controllers have two series controllers

which are connected in series with the transmission line coupled via common dc power lin to

transmit the current, voltage and power.

;i< Int"r$in" Po!"r 7$o! Contro$$"r= !ccording to I/// definitions and standards, it

consists of two or more ###" which are coupled via common dc power lin to facilitate

bidirectional flow of real power between the ac terminals of ###". Interline Power Flow

"ontroller IPF"$ can be seen in Fig. >.

IPF" is a new concept for an overall real and reactive compensation and effective power flow

management of multi-line transmission systems by transferring the power from overloaded to

under loaded lines. It consists of a number of inverters with a common dc lin to facilitate

real Power transfer among the lines of transmission system. The prime inverters can be

controlled to provide totally different operating functions, e.g., independent P and control,

phase shifting transmission angle regulation$, transmission impedance control, etc.

In order to analye the flexibility of power flow control, the steady state operation of

the IPF" has been investigated through its mathematical model using improved control

strategies. ! mathematical model based on the d-q orthogonal coordinates was developed to

address the issues lie the relationship between the transmission angle and the IPF" controlled

region.

Dept. of EEE Page 1# /swar "ollege of /ngineering


18/53


The power in5ection model has been incorporated in 4ewton-(aphson 4($ power

flow solution method on I/// ?-bus system on the basis of a )!T1!0 program to

demonstrate the performance of the IPF" model and its effects in power flow studies

To verify the capability of IPF" in controlling the power flow in power system a case

study has been conducted on B-bus J


19/53


To investigate the inter-system oscillations, a linear model of '#"-based F!"T#

devices has been developed that taes into account the dynamics of dc lins and then

incorporated into production-grade software for small signal analysis of large power systems

For state estimation a model with IPF" has been introduced on the basis of

conventional power system state estimation model, in which power in5ection model has been

used and the effect of IPF" on the power flow has been transferred to the lines which are

connected to it .

;d< Com&in"d /"ri"s and /'unt Conn"ct"d Contro$$"r= In these controllers, one controller is

connected in series and another is connected in parallel and they both are coupled via a

coordinated control and a common dc power lin in transmission line to transmit the current,

voltage and power.

;i< Unii"d Po!"r 7$o! Contro$$"r= !ccording to I/// definitions and standards, *nified

Power Flow "ontroller *PF"$ consists of #T!T"+) and ###" which are coupled via

common dc power lin to allow bidirectional flow of real power between the series op terminals

of the ###" and shunt op terminals of the #T!T"+). The basic structure of *PF" has been

shown in Fig. 7.

The most promising F!"T# device, *PF", is capable of providing an adaptive voltage

magnitude control as well as active and reactive power control and their regulation. ! new

mathematical model of *PF" incorporated in 4ewton-(aphson load flow algorithm has been

developed. 'oltage #tability Index has been used for optimal location of *PF" and Particle

#warm +ptimiation P#+$ technique has been used to set the parameters of *PF" being

tested on I/// 6-0us and I/// ?-0us systems using )!T1!0.

! numerical method tested with )atlab consisting of a set of equations for a system

including the *PF" and an equivalent two bus power networ has been successfully validated

Dept. of EEE Page 1@ /swar "ollege of /ngineering


20/53


with analog model and /)TP. The mathematical models for new *PF" series control modes

have been presented which include direct voltage in5ection, bus voltage regulation, line

impedance compensation and phase angle regulation. In comparison with the classical

decoupled control strategy, for better stability and transient performance a modified control

structure with a predictive control loop and pre control signal has been designed for a dc-

voltage control and control of harmonic current The selection of damping control signal for the

design of *PF" damping controller and the effect of *PF" &" voltage regulator on power

system oscillation stability and the have been studied and demonstrated on the Phillips=3effron

model .

The modeling of converter-based controllers in which two or more '#"s are coupled to

a dc lin lie *PF", IPF" and %*PF" has been presented for load-flow calculations .The

modeling and simulation of I///


21/53


verify the performance of *PF" with different controllers lie PI& controller and !4FI#

controller.

For the analysis of the steady state operation of *nified Power Flow "ontroller

connected in a power system, an improved steady state mathematical model has been presented

employing conventional techniques such as 4ewton-(aphson method and has been simulated

on I///


22/53


system demonstrating the feasibility as well as the effectiveness of the %*PF" in the +PF

method has been presented.

"ompared with the conventional application of the *PF", the %*PF" have shown

great advantages. For the desired power flow distribution in #ichuan power grid, and also the

voltage control of a substation a control law for the four-converter %*PF" has been proposed.

)athematical models of the IPF" and %*PF" and their implementation in 4ewton power

flow based on the


23/53


The elimination of the common &" lin also allows the #" concept to be applied series

convertors. In that case, the reliability of the new device is further improved due to the reduency provided by the distributed series converters. In addition, series converter distribution reduces cost because no

high- voltage isolation and high power rating components are required at the series part. 0y applying the

two approaches =eliminating common &" lin and distributing series converter, the *PF" is further

developed into a new combined F!"T# device. The &PF" Flow chart and configuration are shown

in Fig.


24/53


(.2 P7C TOPOLO>Y

0y introducing the two approaches outlined in the previous section into *PF" , the

&PF" is achieved. #imilar as the *PF", the &PF" consists of shunt and series connected

convertes. The shunt converter is similar as a #T!T"+), while the series conerter employs the

#" concept, which is to use multiple single- phase converters instead of one three-phase

converter. /ach converter within the &PF" is independent and has its own &" capacitor to

provide the required &" voltage. The configuration of the &PF" is shown in fig


25/53


each side of the line. To ensure that the &PF" have the same control capability as the *PF", a

method that allows the exchange of active power between converters with eliminated dc lin is

the prerequisite.

A. E$iminat" C Lin8

2ithin the &PF", transmission line is the common connection between the !" terminal of

the shunt and series converters. Therefore it is possible to exchange the active power though

the terminals of the converters. The method is based on power theory of non sinusoidal

components. !ccording to the Fourier analysis, a non sinusoidal voltage and current can be

expressed by the sum of sinusoidal functions in different frequencies wit different amplitudes.

The active power resulting from this non sinusoidal voltage and current is defined as the mean

value of the product of voltage and current. #ince the integral of all the cross product of terms

with different frequencies are ero, the power can be expressed byC

2here 'i and Ii are the voltage and current at the ith harmonic frequency, respectively,

and Oi is the corresponding angle between the voltage and current. From this equation active

power at different frequencies is isolated from each other and voltage or current in one

frequency has no influence on active power at other frequencies. The independency of the

active power at different frequencies gives the possibility that a converter without power source

can generate active power at one frequency and absorb this power from other frequencies. 0y

applying this method to the &PF" the shunt converter can absorb the active power from the

grid at the fundamental frequency and in5ect the current bac into the grid at a harmonic

frequency. &ue to unique features of < rd harmonic frequency components in a three phase

system, the


26/53


&ue to the unique features of


27/53


!nother advantage of using the


28/53


the ith harmonic frequency Pi and the voltages generated by the converters is expressed by the well

nown the power flow equation and given asC

2here Qi is the line impedance at ith frequency, is the

voltage magnitudes of the harmonic of the shunt and series converters, and

is the angle difference between the two voltages. !s shown, the

impedance of the line limits the active power exchange capacity. To exchange the same amount

of active power, the line with high impedance requires higher voltages. 0ecause the

transmission line impedance is mostly inductive and proportional to frequency, high

transmission frequencies will cause high impedance and result in high voltage within

converters. "onsequently, the ero -sequence harmonic with the lowest frequency - the


29/53


(.3 Ad*anta)"s o P7C

The &PF" can be considered as a *PF" that employs the &F!"T# concept and the

concept of exchanging power through harmonic. Therefore, the &PF" inherits all the

advantages of the *PF" and the &-F!"T#, which are as follows.

1< Hi)' contro$ capa&i$it%= The &PF" can simultaneously control all the parameters of

the power systemC the line impedance, the transmission angle, and the bus voltage.

8$ Hi)' r"$ia&i$it%C The redundancy of the series converter gives an improved reliability.

In addition, the shunt and series converters are independent, and the failure at one place will

not influence the other converters. 2hen a failure occurs in the series converter, the

converter will be short-circuited by bypass protection, thereby having little influence to the

networ.

(< Lo! cost= There is no phase-to-phase voltage isolation required by the series

converter. !lso, the power rating of each converter is small and can be easily produced in

series production lines.



30/53


(. P7C CO5TROL

To control multiple converters, a &PF" consists of three types of controllersC

central control, shunt control and series control,

The shunt and series control are localied controllers and are responsible for maintaining their own

convertersK parameters. The central control taes care of the &PF" functions at the power system level.

The function of each controller is listedC

i< C"ntra$ contro$= The central control generates the reference signals for both the shunt

and series converters of the &PF". Its control function depends on the specifics of the &PF"

application at the power system level, such as power flow control, low frequency power

oscillation damping and balancing of asymmetrical components. !ccording to the system

requirements, the central control gives corresponding voltage reference signals for the series

converters and reactive current signal for the shunt converter. !ll the reference signals ge

nerated by the central control concern the fundamental frequency components.

ii< /"ri"s contro$= /ach series converter has its own series control. The controller is used to

maintain the capacitor &" voltage of its own converter, by using < rd harmonic frequency

components, in addition to generating series voltage at the fundamental frequency as required

by the central control.



31/53


!ny series controller has a low-pass and a < rd-pass filter to create fundamental and third

harmonic current, respectively. Two single-phase phase loc loop P11$ are used to tae

frequency and phase information from networ DE. The bloc diagram of series controller in

)atlab#imulin is shown in Fig. 6. The P2)-%enerator bloc manages switching processes.

iii< /'unt Contro$



32/53


The shunt converter includes a three-phase converter connected bac-to-bac to a

single-phase converter. The three-phase converter absorbs active power from grid at

fundamental frequency and controls the dc voltage of capacitor between this converter and

single-phase one. +ther tas of the shunt converter is to in5ect constant third-harmonic current

into lines through the neutral cable of R-M transformer.

The ob5ective of the shunt control is to in5ect a constant < rd harmonic current into the

line to supply active power for the series converters. !t the same time, it maintains the

capacitor &" voltage of the shunt converter at a constant value by absorbing active power from

the grid at the fundamental frequency and in5ecting the required reactive current at the

fundamental frequency into the grid.

/ach converter has its own controller at different frequency operation fundamental and third-

harmonic frequency$. The shunt control structure bloc diagram is shown in Fig. B.



33/53


The third-harmonic frequency control is the ma5or control loop with the &PF" series converter

control. The principle of the vector control is used here for the dc-voltage control. The third-

harmonic current through the line is selected as the rotation reference frame for the single-phase

par transformation, because it is easy to be captured by the phase-loced loop P11$ in the

series converter. !s the line current contains two frequency components, a third high-pass filter

is needed to reduce the fundamental current. The d-component of the third harmonic voltage isthe parameter that is used to control the dc voltage, and its reference signal is generated by the

dc-voltage control loop. To minimie the reactive power that is caused by the third harmonic, the

series converter is controlled as a resistance at the third-harmonic frequency. The q-component

of the third harmonic voltage is ept ero during the +peration.

!s the series converter is single phase, there will be voltage ripple at the dc side of

each converter. The frequency of the ripple depends on the frequency of the current that flows

through the converter. !s the current contains the fundamental and third harmonic frequency

component, the dc-capacitor voltage will contain ;;-, 8;;-, and


34/53


at the fundamental frequency. The q-component of the reference signal of the shunt converter is

obtained from the central "ontroller and dc component is generated by the dc control.

CHAPTER-3

POWER QUALITY TER0/ A5 REACTI+E POWER

CO5TROL

3.1 5""d o R"acti*" po!"r contro$.

In an electric circuit is the rate of flow of energy past a given point of the circuit.

In alternating current circuits, energy storage elements such as inductors and capacitors may

result in periodic reversals of the direction of energy flow. The portion of power that averaged

over a complete cycle of the !" waveform, results in net transfer of energy in one direction is

nown as real power. The portion of power due to stored energy, which returns to the source in

each cycle, is nown as reactive power.

3.2 R"a$@ r"acti*"@ and appar"nt po!"r

In a simple alternating current !"$ circuit consisting of a source and a linear load, both

the current and voltage are sinusoidal. If the load is purely resistive, the two quantities reverse

their polarity at the same time. !t every instant the product of voltage and current is positiveL

indicating that the direction of energy flow does not reverse. In this case, only real power is

transferred.

If the loads are purely reactive, then the voltage and current are 7; degrees out of phase.

For half of each cycle, the product of voltage and current is positive, but on the other half of the

cycle, the product is negative, indicating that on average, exactly as much energy flows toward

the load as flows bac. There is no net energy flow over one cycle. In this case, only reactive

energy flowsthere is no net transfer of energy to the load.

Practical loads have resistance, inductance, and capacitance, so both real and reactive

power will flow to real loads. Power engineers measure apparent power as the magnitude of the

vector sum of real and reactive power. !pparent power is the product of the root-mean-

square of voltage and current.

/ngineers care about apparent power, because even though the current associated with

reactive power does no wor at the load, it heats the wires, wasting energy. "onductors,


http://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Inductorshttp://en.wikipedia.org/wiki/Inductorshttp://en.wikipedia.org/wiki/Capacitorshttp://en.wikipedia.org/wiki/Capacitorshttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Sine_wavehttp://en.wikipedia.org/wiki/Sine_wavehttp://en.wikipedia.org/wiki/Resistivehttp://en.wikipedia.org/wiki/Resistivehttp://en.wikipedia.org/wiki/Electrical_reactancehttp://en.wikipedia.org/wiki/Electrical_reactancehttp://en.wikipedia.org/wiki/Root-mean-squarehttp://en.wikipedia.org/wiki/Root-mean-squarehttp://en.wikipedia.org/wiki/Inductorshttp://en.wikipedia.org/wiki/Capacitorshttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Sine_wavehttp://en.wikipedia.org/wiki/Resistivehttp://en.wikipedia.org/wiki/Electrical_reactancehttp://en.wikipedia.org/wiki/Root-mean-squarehttp://en.wikipedia.org/wiki/Root-mean-squarehttp://en.wikipedia.org/wiki/Alternating_current


35/53


transformers and generators must be sied to carry the total current, not 5ust the current that

does useful wor.

!nother consequence is that adding the apparent power for two loads will not

accurately give the total apparent power unless they have the same displacement between

current and voltage the same power factor $.

"onventionally, capacitors are considered to generate reactive power and inductors to

consume it. If a capacitor and an inductor are placed in parallel, then the currents flowing

through the inductor and the capacitor tend to cancel rather than add. This is the fundamental

mechanism for controlling the power factor in electric power transmissionL capacitors or

inductors$ are inserted in a circuit to partially cancel reactive power UconsumedU by the load.

The complex power is the vector sum of real and reactive power. The apparent power is the

magnitude of the complex power.

R"a$ po!"r, P

R"acti*" po!"r, Q

Comp$" po!"r, S

Appar"nt po!"r, |S|

P'as" o curr"nt,

/ngineers use the following terms to describe energy flow in a system and assign each of them

a different unit to differentiate between them$C

• R"a$ po!"r, P , or acti*" po!"rC watt 2$

• R"acti*" po!"r, QC volt-ampere reactive var$

• Comp$" po!"r, S C volt-ampere '!$

Dept. of EEE Page 3! /swar "ollege of /ngineering

http://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Watthttp://en.wikipedia.org/wiki/Volt-ampere_reactivehttp://en.wikipedia.org/wiki/Volt-amperehttp://en.wikipedia.org/wiki/Volt-amperehttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Watthttp://en.wikipedia.org/wiki/Volt-ampere_reactivehttp://en.wikipedia.org/wiki/Volt-ampere


36/53


• Appar"nt po!"r, VS VC the magnitude of complex power S C volt-ampere '!$

• P'as" o *o$ta)" r"$ati*" to curr"nt, C the angle of difference in degrees$ between

voltage and currentL current lagging voltage quadrant I vector$, current leading voltage

quadrant I' vector$

In the diagram, P is the real power, Q is the reactive power in this case positive$, S is the

complex power and the length of S is the apparent power. (eactive power does not do any

wor, so it is represented as the ima)inar% ais of the vector diagram. (eal power does do

wor, so it is the real axis.

The unit for all forms of power is the watt symbolC 2$, but this unit is generally

reserved for real power. !pparent power is conventionally expressed in volt-amperes '!$

since it is the product of rms voltage and rms current. The unit for reactive power is expressed

as var, which stands for volt-ampere reactive. #ince reactive power transfers no net energy to

the load, it is sometimes called WwattlesW power. It does, however, serve an important function

in electrical grids and its lac has been cited as a significant factor in the 4ortheast 0lacout of

8;;


37/53


Purely capacitive circuits supply reactive power with the current waveform leading the voltage

waveform by 7; degrees, while purely inductive circuits absorb reactive power with the current

waveform lagging the voltage waveform by 7; degrees. The result of this is that capacitive and

inductive circuit elements tend to cancel each other out.

2here the waveforms are purely sinusoidal, the power factor is the cosine of the phase angle O$

between the current and voltage sinusoid waveforms. /quipment data sheets and nameplates

often will abbreviate power factor as W W for this reason.

/xampleC The real power is A;; 2 and the phase angle between voltage and current is ?6.BZ.

The power factor is cos ?6.BZ$ X ;.A;;. The apparent power is thenC A;; 2 cos ?6.BZ$ X ;;;

'!.

3.3 R"acti*" po!"r

(eactive power flow is needed in an alternating-current transmission system to support

the transfer of real power over the networ. In alternating current circuits, energy is stored

temporarily in inductive and capacitive elements, which can result in the periodic reversal of

the direction of energy flow. The portion of power flow remaining, after being averaged over a

complete !" waveform, is the real powerL that is, energy that can be used to do wor for

example overcome friction in a motor, or heat an element$. +n the other hand, the portion of

power flow that is temporarily stored in the form of magnetic or electric fields, due to inductive

and capacitive networ elements, and then returned to source, is nown as reactive power.

!" connected devices that store energy in the form of a magnetic field include devices

called inductors, which consist of a large coil of wire. 2hen a voltage is initially placed across

the coil, a magnetic field builds up, and it taes a period of time for the current to reach full

value. This causes the current to lag behind the voltage in phaseL hence, these devices are said

to a!sor! reactive power.

! capacitor is an !" device that stores energy in the form of an electric field. 2hen

current is driven through the capacitor, it taes a period of time for a charge to build up to

produce the full voltage difference. +n an !" networ, the voltage across a capacitor is

constantly changing = the capacitor will oppose this change, causing the voltage to lag behind

the current. In other words, the current leads the voltage in phaseL hence, these devices are said

to generate reactive power.

Dept. of EEE Page 3# /swar "ollege of /ngineering


38/53


/nergy stored in capacitive or inductive elements of the networ give rise to reactive

power flow. (eactive power flow strongly influences the voltage levels across the networ.

'oltage levels and reactive power flow must be carefully controlled to allow a power system to

be operated within acceptable limits.

3. R"acti*" po!"r contro$

Transmission connected generators are generally required to support reactive power

flow. For example on the *nited Gingdom transmission system generators are required by the

%rid "ode (equirements to supply their rated power between the limits of ;.>6 power factor

lagging and ;.7; power factor leading at the designated terminals. The system operator will

perform switching actions to maintain a secure and economical voltage profile while

maintaining a reactive power balance equationC

%enerator )'!(s Y #ystem gain Y #hunt capacitors X )'!( &emand Y (eactive losses Y

#hunt reactors

The H#ystem gainK is an important source of reactive power in the above power balance

equation, which is generated by the capacitive nature of the transmission networ itself. 0y

maing decisive switching actions in the early morning before the demand increases, the

system gain can be maximied early on, helping to secure the system for the whole day.

To balance the equation some pre-fault reactive generator use will be required. +ther

sources of reactive power that will also be used include shunt capacitors, shunt reactors, #tatic

'!( "ompensators and voltage control circuits.

Dept. of EEE Page 3? /swar "ollege of /ngineering


39/53


CHAPTER-

0ATLA?B/I0ULATIO5 RE/ULT/

Introduction

)!T1!0 is a high-performance language for technical computing. It integrates

computation, visualiation, and programming in an easy-to-use environment where problems

and solutions are expressed in familiar mathematical notation. Typical uses include-

)ath and computation

!lgorithm development

&ata acquisition

)odeling, simulation, and prototyping

&ata analysis, exploration, and visualiation

#cientific and engineering graphics

0ATLA?=

)atlab is a high-performance language for technical computing. It integrates

computation, visualiation, and programming in an easy-to-use environment where problems

and solutions are expressed in familiar mathematical notation. Typical uses include )ath and

computation !lgorithm development &ata acquisition )odeling, simulation, and prototyping

&ata analysis, exploration, and visualiation #cientific and engineering graphics !pplication

development, including graphical user interface building.

)atlab is an interactive system whose basic data element is an array that does not

require dimensioning. This allows you to solve many technical computing problems,

especially those with matrix and vector formulations, in a fraction of the time it would tae to

write a program in a scalar no interactive language such as " or F+(T(!4.



40/53


The name matlab stands for matrix laboratory. )atlab was originally written to provide

easy access to matrix software developed by the linpac and eispac pro5ects. Today, matlab

engines incorporate the lapac and blas libraries, embedding the state of the art in software

for matrix computation.

)atlab has evolved over a period of years with input from many users. In university

environments, it is the standard instructional tool for introductory and advanced courses in

mathematics, engineering, and science. In industry, matlab is the tool of choice for high-

productivity research, development, and analysis.

)atlab features a family of add-on application-specific solutions called toolboxes. 'ery

important to most users of matlab, toolboxes allow you to learn and apply specialied

technology. Toolboxes are comprehensive collections of matlab functions )-files$ that

extend the matlab environment to solve particular classes of problems. !reas in which

toolboxes are available include signal processing, control systems, neural networs, fuy

logic, wavelets, simulation, and many others.

T'" mat$a& s%st"m consists o i*" main partsC

&evelopment /nvironment. This is the set of tools and facilities that help you use

matlab functions and files. )any of these tools are graphical user interfaces. It includes the

matlab destop and "ommand 2indow, a command history, an editor and debugger, and

browsers for viewing help, the worspace, files, and the search path.

The matlab )athematical Function 1ibrary. This is a vast collection of computational

algorithms ranging from elementary functions, lie sum, sine, cosine, and complex

arithmetic, to more sophisticated functions lie matrix inverse, matrix /igen values, 0essel

functions, and fast Fourier transforms.

The matlab 1anguage. This is a high-level matrixarray language with control flow

statements, functions, data structures, inputoutput, and ob5ect-oriented programming

features. It allows both Wprogramming in the smallW to rapidly create quic and dirty throw-

away programs, and Wprogramming in the largeW to create large and complex application

programs.



41/53


)atlab has extensive facilities for displaying vectors and matrices as graphs, as well as

annotating and printing these graphs. It includes high-level functions for two-dimensional and

three-dimensional data visualiation, image processing, animation, and presentation graphics.

It also includes low-level functions that allow you to fully customie the appearance of

graphics as well as to build complete graphical user interfaces on your matlab applications.

The matlab !pplication Program Interface !PI$. This is a library that allows you to

write " and F+(T(!4 programs that interact with matlab. It includes facilities for calling

routines from matlab dynamic lining$, calling matlab as a computational engine, and for

reading and writing )!T-files.

/I0ULI5

#I)*1I4G

#imulin, developed by )ath2ors, is a data flow graphical programming language tool

for modeling, simulating and analying multidomain dynamic systems. Its primary interface is

a graphical bloc diagramming tool and a customiable set of bloc libraries. It offers tight

integration with the rest of the)!T1!0 environment and can either drive )!T1!0 or be

scripted from it. #imulin is widely used in control theory and digital signal processing for

multidomain simulation and )odel-0ased &esign.

A. "dd#on products

! number of )ath 2ors and third-party hardware and software products are available

for use with #imulin. For example, #tate flow extends #imulin with a design environment for

developing state machines and flow charts.

"oupled with #imulin "oder , another product from )ath 2ors, #imulin can automatically

generate #ource for real-time implementation of systems. !s the efficiency and flexibility of the

code improves, this is becoming more widely adopted for production systems, in addition to

being a popular tool for embedded design wor because of its flexibility and capacity for quic

iteration. "ode creates code efficient enough for use in embedded systems.

QP" Target together with x>B-based real-time systems provides an environment to

simulate and test #imulin and #tate flow models in real-time on the physical system. /mbedded


http://en.wikipedia.org/wiki/MathWorkshttp://en.wikipedia.org/wiki/MathWorkshttp://en.wikipedia.org/wiki/Data_flowhttp://en.wikipedia.org/wiki/Dynamic_systemshttp://en.wikipedia.org/wiki/Visual_modelinghttp://en.wikipedia.org/wiki/Visual_modelinghttp://en.wikipedia.org/wiki/Library_(computer_science)http://en.wikipedia.org/wiki/Library_(computer_science)http://en.wikipedia.org/wiki/MATLABhttp://en.wikipedia.org/wiki/MATLABhttp://en.wikipedia.org/wiki/Control_theoryhttp://en.wikipedia.org/wiki/Digital_signal_processinghttp://en.wikipedia.org/wiki/Model-based_designhttp://en.wikipedia.org/wiki/Stateflowhttp://en.wikipedia.org/wiki/State_machineshttp://en.wikipedia.org/wiki/Flowcharthttp://www.mathworks.com/products/simulink-coder?s_cid=wiki_simulink_3http://en.wikipedia.org/wiki/MathWorkshttp://en.wikipedia.org/wiki/Real-time_computinghttp://www.mathworks.com/products/embedded-coder?s_cid=wiki_simulink_5http://en.wikipedia.org/wiki/MathWorkshttp://en.wikipedia.org/wiki/Data_flowhttp://en.wikipedia.org/wiki/Dynamic_systemshttp://en.wikipedia.org/wiki/Visual_modelinghttp://en.wikipedia.org/wiki/Library_(computer_science)http://en.wikipedia.org/wiki/MATLABhttp://en.wikipedia.org/wiki/Control_theoryhttp://en.wikipedia.org/wiki/Digital_signal_processinghttp://en.wikipedia.org/wiki/Model-based_designhttp://en.wikipedia.org/wiki/Stateflowhttp://en.wikipedia.org/wiki/State_machineshttp://en.wikipedia.org/wiki/Flowcharthttp://www.mathworks.com/products/simulink-coder?s_cid=wiki_simulink_3http://en.wikipedia.org/wiki/MathWorkshttp://en.wikipedia.org/wiki/Real-time_computinghttp://www.mathworks.com/products/embedded-coder?s_cid=wiki_simulink_5


42/53


"oder also supports specific embedded targets, including Infineon "BB, )otorola B>3"8,

)otorola )P"666, TI"8;;;, TI"B;;;, (enesas '>6; and (enesas #uper3. 2ith 3&1 "oder ,

also from )ath 2ors, #imulin and #tate flow can automatically generate synthesiable

'3&1 and 'erilog. #imulin 'erification and 'alidation enables systematic verification and

validation of models through modeling style checing, requirements traceability and model

coverage analysis. #imulin &esign 'erifier uses formal methods to identify design errors

lie integer overflow, division by ero and dead logic, and generates test case scenarios

for model checing within the #imulin environment.

The systematic testing tool TPT offers one way to perform formal test- verification and

validation process to stimulate #imulin models but also during the development phase where

the developer generates inputs to test the system. 0y the substitution of the "onstant and #ignal

generator blocs of #imulin the stimulation becomes reproducible.

#im/vents adds a library of graphical building blocs for modeling queuing systems to

the #imulin environment. It also adds an event-based simulation engine to the time-based

simulation engine in #imulin.

Introduction=

#imulin is a software add-on to matlab which is a mathematical tool developed by The

)ath wors,httpCwww.mathwors.com$ a company based in 4atic. )atlab is powered by

extensive numerical analysis capability. #imulin is a tool used to visually program a

dynamic system those governed by &ifferential equations$ and loo at results. !ny logic

circuit, or control system for a dynamic system can be built by using standard building blocs

available in #imulin 1ibraries. 'arious toolboxes for different techniques, such as Fuy

1ogic, 4eural 4etwors, dsp, #tatistics etc. are available with #imulin, which enhance the

processing power of the tool. The main advantage is the availability of templates building

blocs, which avoid the necessity of typing code for small mathematical processes.

Conc"pt o si)na$ and $o)ic $o!=

In #imulin, datainformation from various blocs are sent to another bloc by lines

connecting the relevant blocs. #ignals can be generated and fed into blocs dynamic

static$.&ata can be fed into functions. &ata can then be dumped into sins, which could be


http://www.mathworks.com/products/embedded-coder?s_cid=wiki_simulink_5http://en.wikipedia.org/wiki/Infineonhttp://en.wikipedia.org/wiki/Motorolahttp://en.wikipedia.org/wiki/68HC12http://en.wikipedia.org/wiki/Motorolahttp://en.wikipedia.org/wiki/Texas_Instruments_TMS320http://en.wikipedia.org/wiki/Texas_Instruments_TMS320http://en.wikipedia.org/wiki/Renesashttp://en.wikipedia.org/wiki/V850http://en.wikipedia.org/wiki/Renesashttp://en.wikipedia.org/wiki/SuperHhttp://www.mathworks.com/products/slhdlcoder?s_cid=wiki_simulink_6http://en.wikipedia.org/wiki/MathWorkshttp://en.wikipedia.org/wiki/Logic_synthesishttp://en.wikipedia.org/wiki/VHDLhttp://en.wikipedia.org/wiki/Veriloghttp://en.wikipedia.org/wiki/Requirements_traceabilityhttp://en.wikipedia.org/wiki/Formal_methodshttp://en.wikipedia.org/wiki/Integer_overflowhttp://en.wikipedia.org/wiki/Division_by_zerohttp://en.wikipedia.org/wiki/Model_checkinghttp://en.wikipedia.org/wiki/TPT_(Software)http://en.wikipedia.org/wiki/Verification_and_validation_(software)http://en.wikipedia.org/wiki/Verification_and_validation_(software)http://en.wikipedia.org/wiki/SimEventshttp://www.mathworks.com/products/embedded-coder?s_cid=wiki_simulink_5http://en.wikipedia.org/wiki/Infineonhttp://en.wikipedia.org/wiki/Motorolahttp://en.wikipedia.org/wiki/68HC12http://en.wikipedia.org/wiki/Motorolahttp://en.wikipedia.org/wiki/Texas_Instruments_TMS320http://en.wikipedia.org/wiki/Texas_Instruments_TMS320http://en.wikipedia.org/wiki/Renesashttp://en.wikipedia.org/wiki/V850http://en.wikipedia.org/wiki/Renesashttp://en.wikipedia.org/wiki/SuperHhttp://www.mathworks.com/products/slhdlcoder?s_cid=wiki_simulink_6http://en.wikipedia.org/wiki/MathWorkshttp://en.wikipedia.org/wiki/Logic_synthesishttp://en.wikipedia.org/wiki/VHDLhttp://en.wikipedia.org/wiki/Veriloghttp://en.wikipedia.org/wiki/Requirements_traceabilityhttp://en.wikipedia.org/wiki/Formal_methodshttp://en.wikipedia.org/wiki/Integer_overflowhttp://en.wikipedia.org/wiki/Division_by_zerohttp://en.wikipedia.org/wiki/Model_checkinghttp://en.wikipedia.org/wiki/TPT_(Software)http://en.wikipedia.org/wiki/Verification_and_validation_(software)http://en.wikipedia.org/wiki/Verification_and_validation_(software)http://en.wikipedia.org/wiki/SimEvents


43/53


scopes, displays or could be saved to a file. &ata can be connected from one bloc to another,

can be branched, multiplexed etc. In simulation, data is processed and transferred only at

discrete times, since all computers are discrete systems. Thus, a simulation time step

otherwise called an integration time step$ is essential, and the selection of that step is

determined by the fastest dynamics in the simulated system.

Fig 6. #imulin library browser

Conn"ctin) &$oc8s=



44/53


"onnectung blocs

To connect blocs, left-clic and drag the mouse from the output of one bloc to the

input of another bloc.

/ourc"s and sin8s=

The sources library contains the sources of datasignals that one would use in a dynamic

system simulation. +ne may want to use a constant input, a sinusoidal wave, a step, a

repeating sequence such as a pulse train, a ramp etc. +ne may want to test disturbance effects,

and can use the random signal generator to simulate noise. The cloc may be used to create a

time index for plotting purposes. The ground could be used to connect to any unused port, to

avoid warning messages indicating unconnected ports.

The sins are blocs where signals are terminated or ultimately used. In most cases, we

would want to store the resulting data in a file, or a matrix of variables. The data could bedisplayed or even stored to a file. the stop bloc could be used to stop the simulation if the

input to that bloc the signal being sun$ is non-ero. Figure < shows the available blocs in

the sources and sins libraries. *nused signals must be terminated, to prevent warnings about

unconnected signals.



45/53


Fig 6.8 #ources and sins

Continuous and discr"t" s%st"ms=

!ll dynamic systems can be analyed as continuous or discrete time systems. #imulin

allows you to represent these systems using transfer functions, integration blocs, delay blocs etc.

CHAPTER-4

/I0ULATIO5 0OEL A5 /I0ULATIO5 RE/ULT/

4.1 /imu$ation mod"$s

Dept. of EEE Page ! /swar "ollege of /ngineering


46/53


7i). 4.1 /imu$ation dia)ram o T'r""-p'as" s%st"m !it'out P7C

Dept. of EEE Page " /swar "ollege of /ngineering


47/53


7i).4.2. /imu$ation dia)ram o T'r""-p'as" s%st"m !it' P7C

Dept. of EEE Page # /swar "ollege of /ngineering


48/53


4.2 EDA0I5I5> /I0ULATIO5 RE/ULT/

Fig. ; depicts the load current swell about . per- unit, during the fault. !fter

implementation of the &PF", the load current swell is removed effectively. The current swell

mitigation for this case can be observed from Fig. .

Dept. of EEE Page ? /swar "ollege of /ngineering


49/53


The load voltage harmonic analysis without presence of &PF" is illustrated in Fig. 8.

It can be seen, after &PF" implementation in system, the even harmonics is eliminated , the

odd harmonics are reduced within acceptable limits, and total harmonic distortion T3&$ of

load voltage is minimied from ?6.BA to ;.B6 percentage Fig.


50/53


Dept. of EEE Page ! /swar "ollege of /ngineering


51/53


4.( POWER QUALITY I0PRO+E0E5T

The whole model of system under study is shown in Fig. B.>. The system contains a

three-phase source connected to a nonlinear (1" load through parallel transmission lines 1ine

and 1ine 8$ with the same lengths. The &PF" is placed in transmission line, which the shunt

converter is connected to the transmission line 8 in parallel through a M-R three-phase

transformer, and series converters is distributed through this line. The system parameters are

listed in appendix T!01/ I. To simulate the dynamic performance, a three-phase fault is

considered near the load. The time duration of the fault is ;.6 seconds 6;;-;;; millisecond$.

!s shown in Fig.B.6 , significant voltage sag is observable during the fault, without any

compensation. The voltage sag value is about ;.6 per unit per unit. !fter adding a &PF", load

voltage sag can be mitigated effectively, as shown in Fig. B.B

Ta&$" 4.1 simu$ation s%st"m param"t"rs

Parameters 'alues

Three phase source

(ated voltage 8


52/53


line impedance, transmission angle, and bus voltage magnitude. 3owever, the &PF" offers

some advantages, in comparisons with *PF", such as high control capability, high reliability,

and low cost. The &PF" is modeled and three phase control loops i.e.L central controller,

series control, and shunt control are design. The system under study is a machine infinite =bus

system, with and without &PF". To simulate the dynamic performance, a three-phase fault is

considered near the load. It is shown that the &PF" gives an acceptable performance in

power quality mitigation and power flow control.

RE7ERE5CE/

DE Power uality Improvement and )itigation "ase #tudy *sing &istributed Power Flow

"ontroller, !hmad \amshidi,a, #. )asoud 0araati,b, and )ohammad )oradi %hahderi5ani,

" /"/ &epartment, *niversity of #istan and 0aluchistan, Iran.

Dept. of EEE Page !2 /swar "ollege of /ngineering


53/53


D8E %uide boo, on "ustom Power &evices by /P(I Pro5ect )anager !.#undaram

D

lalu document

Documents