Docslide.us Variable Frequency Transformer Ppt

7/24/2019 Docslide.us Variable Frequency Transformer Ppt

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Variable frequencytransformer

SUBMITTED BY:

SUHAIL AHMAD SUHAIL

E!"LL: #$%&'#

!"LL "( %)


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VA!IABLE *!E+UE,YT!AS*"!ME!

A new power transmission technology has recently been

made available which is simple and reliable.

This technology is called VARIABLE FREQE!"#TRA!$F%R&ER

A VFT has been in commercial operation since '(() and has

proven to be a reliable power transmission technology

There are presently two VFT*s in commercial operation. Theyare

+, Hy-ro.+uebec/s Lan0lois substation1,ana-a(

',Lare-o V*T substation1te2as(


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34at is 5ft((6

The variable -re/ency trans-ormer 0VFT, is a controllable1bi2directional transmission device that can trans-er power

between networ3s o- two grids /nder some or all operating

conditions

The two grids need not be synchrono/s. 4hile primarily designed to move power across an

asynchrono/s interconnection. the VFT has also shown itsel-

to have remar3able stabili5ing bene-its

The VFT is not only compatible with other devices b/t in

some cases enhances the per-ormance o- nearby e6isting

e/ipments


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Vft tec4nolo0y

The VFT is composed o- a rotary trans-ormer 1 a tor/e motorand an associated drive and control system.


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construction

The R%TAR# TRA!$F%R&ER is composed o- a stator

that is very m/ch li3e a stator o- hydro generator.

There are laminations o- steel stac3ed inside a stator

-rame.

4inding bars are con-ig/red into a three phase 1 -o/r pole

arrangement.

The rotar also contain three phase 1-o/r pole winding.

%ne grid is to the winding 1 while the other grid is

connected to the rotor.

The net e--ect is the circ/lar trans-ormer has been

prod/ced 1 with winding separated by an airgap.


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,ont((

In order to ma3e the connections to the rotor and the

rotor to t/rn -reely a slip ring arrangement is necessary.

The VFT contains a device 3nown as the "%LLE"T%R.

The collector consist o- three phases o- br/shes and

large copper slip rings

The n/mber and si5e o- the element o- collector that the

-/ll rating o- the machine c/rrent can be trans-erred

contin/o/sly thro/gh the -/ll range o- speeds in eitherdirection 1incl/ding 5ero speed.

Also on the sha-t o- the VFT is a T%RQE &%T%R.


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,ont(( This motor is /sed to align the rotor with respect to the stator

and maintain the rotation necessary bridge the di--erence in the-re/ency o- the two grids.

A motor and drive system are /sed to ad7/st the rotational

position o- the rotor relative to the stator1 thereby controlling

the magnit/de and direction o- the power -lowing thro/gh theVFT.


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o7eration "onsider VFT connected to two asynchrono/s grids.

The two grids shall be called as grid2A 1grid2B.

when both the grids are operating at e6actly same -re/ency 1say

8(9:1the rotor will stop.

I- grid2A -re/ency slightly increases to 8(.+951while grid2B*s

-re/ency remains constant. The rotor o- VFT will t/rn to allow -orthis di--erence.

Beca/se it*s -o/r pole machine 1 it will be rotate at ;rpm.

!ow the condition where grid2A -re/ency slow down to )


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"8E!ATI"AL

E98E!IE,EPerformance factor (PF) : The -orm/la established to eval/ate the VFT per-ormance -actor

was de-ined in the contract and is shown in 0;,.

4here &4h=real> is energy thro/gh the VFT and

&4h=shed/led >is Energy sched/led on the VFT.

A-ter the -irst three years o- commercial operation1 theo--icial per-ormance -actor o- the Langlois VFT was


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,ont((

Improved HVDC Performance :

&ore than one potential VFT c/stomer has st/died the

possibility o- placing a VFT in parallel with an e6isting bac32

to2bac3 9V".

$t/dies have shown that a n/mber o- advantages co/ld be

reali5ed with s/ch a hybrid interconnection.

Advantages incl/de increased system stability1 additional short

circ/it strength1 improved comm/tation1 low power level

operation 1improved damping1 and with the VFTs optional

blac3 start -eat/re1 one grid co/ld help blac3 start the other


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,ont((

Improved Range of Phase Angle Regulator:

The three VFTs are e--ectively in parallel with three ARs1 all

moving power between two di--erent control areas.

The res/lt o- paralleling the ARs is that the phase angle

between the two systems will be tightened thro/gh an

additional impedance path.

it act/ally improves the per-ormance

characteristics o- the closest AR


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8oer ;o

The power -low thro/gh a VFT behaves according to the

same r/les as any A" circ/it.

As in the case o- phase angle reg/lator 0AR, control o-

voltage angle can be an e--ective means o- controlling power-low between the two points.

4here1

VCsending end D receiving end voltages

?@ di--erence in voltage angle

Cimpedence between two points


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,ont((

Beca/se o- VFT*s /ni/e constr/ction simply t/rning on

one o- the trans-ormer winding with respect to another

can introd/ce o- di--erence in phase angles there by

e--ective power -low. The angle introd/ced in the rotor with respect to stator by

the tor/e motor is propotional to amo/nt o- tor/e

applied to sha-t.

Electrical angle between rotar and

stator shown in -ig/re.


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"ne.Line -ia0ram of a Variable *requency TransformerInterconnection(


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a-5anta0es

"ontin/o/s and no -i6ed set change

points

Response -or stability p/rposes

$imple model -or power system /se

9V" alternative

"an trans-er power at di--erent

-re/encies

&ore control o- the real power -low


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Disa-5anta0es

Limits on ma6im/m power -low capability

&ore lossy especially in reactive power losses

4or3s at low 3V range so it needs step /pdowntrans-ormers


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conclusion

The VFT has proven as a variable transmission technology.

It allows an ac connection to be made between

asynchrono/s ac grids -or reliable and precise power

trans-er.

It has help-/l in stabili5ing characterstics and does not

prod/ce any hormonics or tersional threats.

The operation o- VFT does not rely on grid strength -or

operation and wor3s well in wea3 grid conditions. There-ore 1VFT represents an alternative technology that

may be /sed in I!IA as the view o- electric power as a

b/ssiness emerges.


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THANK YOU

Date post:	21-Feb-2018
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Docslide.us Variable Frequency Transformer Ppt

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