lecture 1 - loadflow

8/11/2019 Lecture 1 - Loadflow

1/19

THE POWER FLOW

(LOADFLOW) PROBLEM

1


2/19

Introduction

Thepower flow problemis a er! "e##$no"n %roe' in the ie#d o %o"ers!ste's enineerin* "here o#tae

'anitudes and an#es or one set o&uses are desired* ien that o#tae'anitudes and %o"er #ee#s or anotherset o &uses are $no"n and that a 'ode#o the net"or$ coniuration (unitco''it'ent and circuit to%o#o!) isaai#ae+


3/19

Apower flow solution procedureis a nu'erica#'ethod that is e'%#o!ed to so#e the %o"er #o"%roe'+

Apower flow programis a co'%uter code thati'%#e'ents a %o"er #o" so#ution %rocedure+

Thepower flow solutioncontains the o#taesand an#es at a## &uses* and ro' this

inor'ation* "e 'a! co'%ute the rea# andreactie eneration and #oad #ee#s at a## &usesand the rea# and reactie #o"s across a##circuits+


4/19

The a&oe ter'ino#o! is oten used "ith

the "ord ,#oad- su&stituted or ,%o"er*-

i+e+* #oad #o" %roe'* #oad #o" so#ution

%rocedure* #oad #o" %rora'* and #oad

#o" so#ution+ Ho"eer* the or'er

ter'ino#o! is %reerred as one nor'a##!

does not thin$ o ,#oad- as so'ethin that,#o"s+-


5/19

The %o"er #o" %roe' "as oriina##! 'otiated

"ithin %#annin eniron'ents "here enineers

considered dierent net"or$ coniurations

necessar! to sere an e.%ected uture #oad+ Later* it &eca'e an o%erationa# %roe' as

o%erators and o%eratin enineers "ere

re/uired to 'onitor the rea#0ti'e status o the

net"or$ in ter's o o#tae 'anitudes andcircuit #o"s+


6/19

Toda!* the %o"er #o" %roe' is "ide#!reconied as a unda'enta# %roe' or%o"er s!ste' ana#!sis* and there are

'an! adanced* co''ercia# %o"er #o"%rora's to address it+

Po"er s!ste' co'%onents 20

3 4enerator3 Load

3 Trans'ission #ines


7/19

The Power Flow Problem


8/19

4enerator

4enerators hae 'a.i'u' and 'ini'u' rea# andreactie %o"er ca%a&i#ities+

The 'a.i'u' reactie %o"er ca%a&i#it! corres%onds tothe 'a.i'u' reactie %o"er that the enerator 'a!

%roduce "hen o%eratin "ith a #ain %o"er actor+ The'ini'u' reactie %o"er ca%a&i#it! corres%onds to the'a.i'u' reactie %o"er the enerator 'a! a&sor&

"hen o%eratin "ith a #eadin %o"er actor+ These#i'itations are a unction o the rea# %o"er out%ut o the

enerator* that is* as the rea# %o"er increases* thereactie %o"er #i'itations 'oe c#oser to ero+


9/19

Fi+ T5+6


10/19

Fi+ T5+6 i##ustrates seera# i'%ortant

e#e'ents o the %o"er #o" %roe'+ First*

one notices "e 'a! cateorie each &us

de%endin on "hether eneration and7or

#oad is connected to it+ 8%eciica##!* a &us

'a! hae eneration on#! (&uses B1* B6*

and B9)* #oad on#! (&uses B:* B5* andB;)* or neither eneration or #oad (&uses

B)+


11/19

A &us 'a! hae &oth eneration and #oad+

This cateoriation* "hich ocuses on the

#oad and eneration* #eads us to deine

the ter' ,&us in?ection- or 'ore si'%#!*

,in?ection+- Its 'eanin 'ust &e u##!

understood


12/19

An injectionis the %o"er* either rea# or reactie*that is &ein in?ected into or "ithdra"n ro' a&us &! an e#e'ent hain its other ter'ina# (inthe %er0%hase e/uia#ent circuit) connected toround+ 8uch an e#e'ent "ou#d &e either aenerator or a #oad+

Positie in?ection is deined as one "here %o"eris #o"in ro' the e#e'ent into the &us+

@eatie in?ection is then "hen %o"er is #o"inro' the &us* into the e#e'ent+


13/19

4enerators nor'a##! hae %ositie rea# %o"erin?ections* a#thouh the! 'a! a#so &e assinedneatie rea# %o"er in?ections* in "hich casethe! are o%eratin as a 'otor+

4enerators 'a! hae either %ositie or neatiereactie %o"er in?ections2 %ositie i theenerator is o%eratin #ain and de#ierinreactie %o"er to the &us* neatie i theenerator is o%eratin #eadin and a&sor&inreactie %o"er ro' the &us* and ero i theenerator is o%eratin at unit! %o"er actor+


14/19

Loads nor'a##! hae neatie rea# and

reactie %o"er in?ections+

Fi T5+92 I##ustration o (a) %ositie in?ection* (&) neatie in?ection*

and (c) net in?ection

Pk=100Qk=30

(a)

Pk= - 40Qk= -20

(b)

Pk=100+(-40)=60Qk=30+(-20)=10

(c)


15/19


16/19

For each &us* there are our %ossie

ariaes that characterie the &uses

e#ectrica# condition+

The our ariaes are rea# and reactie

%o"er in?ection* P$ and C$* res%ectie#!*

and o#tae 'anitude and an#e* $

and $* res%ectie#!+


17/19

There are three &asic t!%es o &uses203 The swing bus - t"o other co''on ter's or this &us are slack

busand reference bus+ There is on#! one s"in &us* and it can&e desinated &! the enineer to &e an! enerator &us in the

s!ste'+ For the s"in &us* "e $no" and + The act that "e

$no" is the reason "h! it is so'eti'es ca##ed the reerence&us+ This enerator ,s"ins- to co'%ensate or the net"or$#osses* or* one 'a! sa! that it ,ta$es u% the s#ac$+-

3 PV Buses2 For t!%e P &uses* "e $no" P$ and $ &ut not C$

or $+ These &uses a## under the cateor! o voltage-controlledbuses&ecause o the a&i#it! to s%eci! (and thereore to $no")the o#tae 'anitude o this &us+ Most enerator &uses a## intothis cateor!* inde%endent o "hether it a#so has #oad


18/19

PQ Buses2 For t!%e PC &uses* "e $no"

P$ and C$ &ut not $ or $+ A## #oad

&uses a## into this cateor!* inc#udin&uses that hae not either #oad or

eneration+


19/19

The AC Power Flow

lecture 1 - loadflow

Documents