TRANSMISSION &
DISTRIBUTION
A Division of Global Power
POWER SYSTEM STABILITY CALCULATION TRAINING
D9
Aliti fL
T St bilit
D
ay
9
-
A
pp
li
ca
ti
on o
f

L
ong-
T
erm
St
a
bilit
y
July 16, 2013Prepared by: Mohamed El Chehaly
OUTLINE
2
OUTLINE

seconds to several minutes
 The need to model additional effects not
normally considered in stability runs of
normally

considered

in

stability

runs

of

several seconds
 Computer time requirements would be
excessive
excessive
Long
Term Stability
5
LONG-TERM STABILITY IN PSS®E
Long
-
Term

Stability
 If simulation time is extended to several
d

LONG-TERM STABILITY IN PSS®E
Extended

Term

Module

Additi l d l th t h t b

Additi
ona
l
mo
d
u
l
e
th
a
t

h
as
t
o
b
e
purchased

Includes the following:

y
t
o c
h
ange
th
e s
i
mu
l
a
ti
on
ti
me s
t
ep
during the simulation

Several additions to the model library

Several

additions

to

the

model

f
ormer
t
ap a
dj
us
t
men
t
s
to help control system voltage

Two main components:

Two

main

components:
 Voltage sensor: if the voltage input is out of the
specified bandwidth, the control will operate after
specified

bandwidth,

the

control

will

or
longer than a preset time
On
load Tap Changer OLTC1
8
LONG-TERM STABILITY IN PSS®E
On
-
load

Tap

Changer

OLTC1

Ti d l 30 d

Ti
me
d
e
l
ay =
30
secon
d
s
On
load Tap Changer OLTC1

On
load Phase Shifter OLPS1
10
LONG-TERM STABILITY IN PSS®E
On
-
load

Phase

Shifter

OLPS1

Mdlf th t ti t ft

M
o
d
e
l

f
or
th
e au
t
oma
ti
c movemen

difference

is

that

the

input

is

real

power instead of voltage
On
load Phase Shifter OLPS1
11
LONG-TERM STABILITY IN PSS®E
On
-
load

Phase

Shifter

OLPS1

M d l OLPS1 t i l l

D
es
i
gne
d

t
o pro
t
ec
t

th
e genera
t
or
fi
e
ld

with automatic excitation control from
overheating due to prolonged
overheating

due

to

prolonged


MAXEX1

I ti h t i ti f MAXEX1

I
nverse
ti
me c
h
arac
t
er
i
s
ti
cs o
f

MAXEX1
Maximum Excitation Limiters MAXEX1
14
LONG-TERM STABILITY IN PSS®E
Maximum

Excitation

Limiters

MAXEX1


MAXEX1

t
yp
i
ca
l
va
l
ues
Steam Turbine and Boiler TGOV5
16
LONG-TERM STABILITY IN PSS®E
Steam

Turbine

and

Boiler

TGOV5

Rt tiiht

R
epresen
t
s governor ac
ti

e
n
t
i
o
n
a
l
co e t o a
Steam Turbine and Boiler TGOV5
17
LONG-TERM STABILITY IN PSS®E
Steam

Turbine

and

Boiler

TGOV5

Gdl

G
overnor mo
d
e
l


pp p
throttle pressure and the valve area
 Proper selection of time constants and gains
allows the modeling of the
reheater
and
allows

the

modeling

of

the

reheater
and

intermediate and low pressure turbine effects
Steam Turbine and Boiler TGOV5
18
LONG-TERM STABILITY IN PSS®E
Steam

Turbine

and

Boiler


steam

flow

out

of

the

boiler
 Throttle pressure (P
T
) is equal to drum pressure
less a pressure drop across superheaters and
steam leads

The pressure drop varies as square of steam flow

The

pressure

drop

varies

as


and

Boiler

TGOV5

Ctiltl

C
onven
ti
ona
l
con
t
ro
l
 Boiler follow mode: changes in generation are
initiated by turbine control valves
initiated

by

turbine

control

valves
 Boiler controls respond with necessary control
action upon sensing the changes in steam flow

w
 Use of the turbine control valves to regulate boiler
pressure
pressure
 Can be done without time delay
 Boiler
p
ressure suffers virtuall
y
no transient
py
deviations
 Stored energy in the boiler is not used

St fl th h th t bi d t bi

St
eam
fl
ow
th
roug
h

th
e
t
ur
bi
ne an

Turbine

and

Boiler

TGOV5
 Coordinated optimal
 Recognize the advantages of the conventional and
turbine follow modes

Compromise between the desire for fast response

Compromise

between

the

desire

for

fast

response

to load changes and the desire for boiler safety
and good quality control of steam conditions
 New demand signal modified by frequency

ar
i
a
bl
e pressure
 The pressure set point is proportional to MW
demand
demand
 The pressure error between set point and actual
throttle pressure drives steam generation
 No coupling occurs between the demand signal
and the turbine control valve position
Steam Turbine and Boiler TGOV5
24
LONG-TERM STABILITY IN PSS®E
Steam

Turbine

and

Boiler

TGOV5
 Typical data for TGOV5
Underfre
q
uenc
y
Load Sheddin

 LDSHAR: loads in a specific area
 LDSHAL: all loads
 Represent solid-state type load-shedding
relays based on low frequency
 Disconnect either a fraction of load or sets
fl t it h li it
fl
ags
t
o sw
it
c
h

li
nes, capac
it
ors…