TRANSMISSION &
DISTRIBUTION
A Division of Global Power
POWER SYSTEM STABILITY CALCULATION TRAINING
D8
HVDC Si l ti P t 2
D
ay
8
-
HVDC

Si
mu
l
a
ti
on
P
ar
t

2
November 26, 2013Prepared by: Mohamed El Chehaly
eBook for You
OUTLINE
2
OUTLINE
• General Considerations
•
HVDC Dynamic Models

that

of

PSS®E

 Each converter bridge is controlled by a
local feedback loop
local

feedback

loop
 These local loops work independently to
maintain bridge current or voltage at
maintain

bridge

current

or

voltage

at

desired value
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Introduction


bridges

and the AC power system
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Behavior of the Brid
g
es and their Inner
6
GENERAL CONSIDERATIONS
g
Control Loops
 A rectifier bridge may be regarded as an
adjustable voltage source forcing current
through transmission system resistance
di d t i tth t t
an
d

i
n
d
uc
t
ance aga
i
ns
t

th

PSS®E Models and Control Loops
9
GENERAL CONSIDERATIONS

Several PSS®E models (CDC4T CDC6T )
PSS®E

Models

and

Control

Loops

Several

PSS®E

models

(CDC4T
,
CDC6T
…
)

treat DC converter pairs as if they move
instantaneousl
y

with the
PSS®E

Models

and

Control

Loops

Several

models

are

not

concerned

with

the

internal dynamic behavior of converters
and DC lines
and

DC

(CDC4T
,
CDC6T
…
)
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PSS®E Models and Control Loops
11
GENERAL CONSIDERATIONS
 HVDC models such as CDCVUP re
p
resent
PSS®E

Models

and

Control

Loops
p
the temporary dynamic condition when
neither converter is at a firing angle or
margin angle limit and both are fighting for
control of current

PSS®E l i l d d l (CASEA1 d

PSS®E

dynamics of the DC transmission. These
m
ode
l
s

use

a
n in
te
rn
a
l in
teg
r
at
i
o
n
t
im
e

ode s use a te a teg at o t e
shorter than by other PSS®E models
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Actions by the Controls
12
GENERAL CONSIDERATIONS

em vo
lt
ages
d
ur
i
ng
f
au
lt
s
 Modulation of the DC power setpoint by a
supplementary control device
(assist in the
supplementary

control

device

(assist

in

the

damping of rotor angle swings)
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Actions by the Controls
13

Actions by the Controls
15
GENERAL CONSIDERATIONS
 Response following disturbance

When AC or DC voltages reach abnormal levels
Actions

by

the

Controls

When

AC

or

DC

voltages

reach

abnormal

levels



Protective blocking is used to stop the flow of both
Protective

Actions

Protective

blocking

is

used

to

stop

the

flow

of

both

AC and DC current in order to limit the effect of the
fault
 Rectifier usually blocked when an AC fault is
applied on the AC side of the rectifier

chan
g
in
g
the
gygg
appropriate ICON or by raising the blocking
voltage threshold to force a block
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Protective Actions
17
GENERAL CONSIDERATIONS
 Bypass

When fault signals of the inverter detect one of the
Protective

Actions

When

fault

signals

of

the

inverter


converter

bridge
 Blocking four valves in the 6-pulse bridge and
firing the remaining two as a bypass pair
 The DC side is shorted and the AC side is open

Th tifi ill ti t i l t l l l

Th
e rec
tifi
er w
ill
con
ti
nue
t
o c
i
rcu
l
a
t
e a
l
ow
l
eve

y
increased when volta
g
e on the AC side
yg
of the inverter is decreased by 0.1 p.u.
 Repeated commutation failures can lead to
bl ki f th l
bl
oc
ki
ng o
f

th
e va
l
ves
 Happen if the commutation of current from one
valve to another has not been com
p
leted before
p
the commutating voltage reverses across the
ongoing valve

Eti ti l i t ll

E
x

-
phase

bridge

converter
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Protective Actions
20
GENERAL CONSIDERATIONS
 Commutation failure

Due to voltage magnitude reduction
Protective

Actions

Due

to

voltage

magnitude

reduction
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Protective Actions
21
GENERAL CONSIDERATIONS


Due to increased DC current
Protective

Actions

Due

to

increased

DC

current
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Protective Actions
23
GENERAL CONSIDERATIONS
 Commutation failure
Protective

Actions
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24
HVDC DYNAMIC MODELS
HVDC

DYNAMIC