TRANSMISSION &
DISTRIBUTION
A Division of Global Power
POWER SYSTEM STABILITY CALCULATION TRAINING
D8
HVDC Si l ti P t 1
D
ay
8
-
HVDC

Si
mu
l
a
ti
on
P
ar
t

1
November 26, 2013Prepared by: Mohamed El Chehaly
eBook for You
OUTLINE
2
OUTLINE
• HVDC Configurations
• HVDC Static Characteristics
• Equivalent HVDC Model in Load Flo


CONFIGURATIONS
eBook for You
Different Configurations
4
HVDC CONFIGURATIONS
Different

Configurations
 Monopolar configuration with ground
return
 Monopolar configuration with metallic
return
 Monopolar configuration with midpoint
grounded
 Bipolar configuration with ground return
 Bipolar configuration with metallic return
 Back-to-back configuration
eBook for You
Mono
p
ola
r
Confi
g
uration with Ground
5
HVDC CONFIGURATIONS
p
g

p
oint
7
HVDC CONFIGURATIONS
p
gp
Grounded
 Economic alternative to monopolar
system with metallic return
 Two conductors required if ground return
current is not allowed
Source: ABB
eBook for You
Bi
p
olar Confi
g
uration with Ground
8
HVDC CONFIGURATIONS
pg
Return
 Most common configuration with 12-pulse
converters
 Balanced operation gives zero earth
current and low transmission losses
Source: ABB
eBook for You
Bi
p

 Used for interconnection of asynchronous
networks
 No transmission line is necessary
 Two converter stations in the same
geographical location
Source: ABB
eBook for You
11
HVDC STATIC
HVDC

STATIC

CHARACTERISTICS
eBook for You
Basic Rectifier Static Characteristics
12
HVDC STATIC CHARACTERISTICS
Basic

Rectifier

Static

Characteristics
 Static control and operation of HVDC links
 With HVDC transmission, one terminal sets the
DC voltage level while the other regulates the DC
current
current

th
e
DC
vo
lt
age an
d

th
e
AC voltage by varying the delay angle α
 By changing the converter AC voltage via load tap
h
c
h
angers
eBook for You
Basic Rectifier Static Characteristics
13
HVDC STATIC CHARACTERISTICS
Basic

Rectifier

Static

Characteristics
 Constant minimum firing angle control
(α
min

eBook for You
Basic Re
q
uirements of the Converter
15
HVDC STATIC CHARACTERISTICS
q
Control System
 Rectifier control
 Normally operated in DC current control
 If the rectifier’s AC terminal voltage is insufficient,
the rectifier will operate with alpha min control
 Inverter control

Normally operated in constant gamma control

Normally

operated

in

constant

gamma

control
 If the rectifier is unable to deliver the required DC
current, the inverter will operate with the DC
current control

WX: resulted current
from inverter
from

inverter
OP: operating point
Source: Alstom
eBook for You
Basic Re
q
uirements of the Converter
17
HVDC STATIC CHARACTERISTICS
q
Control System

Flow from converter B to converter A

Flow

from

converter

B

to

converter



V
AC
 B: Constant α
min
and variable V
AC
Source: Alstom
eBook for You
Extinction Angle Characteristics
19
HVDC STATIC CHARACTERISTICS
Extinction

Angle

Characteristics

A: Variable γ and constant V
AC

A:

Variable

γ

and

constant

Source: Alstom
eBook for You
Reactive Power Characteristics
21
HVDC STATIC CHARACTERISTICS
Reactive

Power

Characteristics
 When DC power is increased, the reactive
power consumed by the converters is
power

consumed

by

the

converters

is

increased as well
Source: Alstom
eBook for You
22
EQUIVALENT HVDC MODEL IN
EQUIVALENT

the

system

must

be

strong

at the converters
dc
P
S
SCR
min

eBook for You
Short
Circuit Level Requirements
24
EQUIVALENT HVDC MODEL IN LOAD FLOW
Short
-
Circuit

Level

Requirements
 Strong system if SCR > 3.0