Phần 18 KHÓA ĐÀO TẠO TÍNH TOÁN ỔN ĐỊNH VÀ ỨNG DỤNG TRÊN PHẦN MỀM PSSE CHO KỸ SƯ HỆ THỐNG ĐIỆN (Mô hình đường dây Siêu cao áp HVDC trên Phần mềm PSSE)

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

w
CltHVDCMdliLdFl
•
C
omp
l
e
t
e
HVDC

M
o
d
e
l

i
n
L
oa
d

Fl
o
w
eBook for You
3
HVDC CONFIGURATIONS
HVDC

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

Return
 Simplest and least expensive systems
 Earth return gives low losses
Source: ABB
eBook for You
Mono
p
ola
r
Confi
g
uration with Metallic
6
HVDC CONFIGURATIONS
p
g
Return
 Used when earth return is not valid
 Also, back-up mode in bipolar
transmission if earth return is not allowed
and with one healthy pole
Source: ABB
eBook for You
Mono
p
ola
r
Confi
g
uration with Mid

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

olar Confi
g
uration with Metallic
9
HVDC CONFIGURATIONS
pg
Return
 More expensive than previous solution
 Case if no earth return is possible
 Balanced o
p
eration
g
ives zero earth
pg
current and low transmission losses
Source: ABB
eBook for You
Back
to
Back Configuration
10
HVDC CONFIGURATIONS
Back
-
to
-
Back

Configuration

 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

 Since the DC line resistance is low, large changes
in current
(
and
p
ower
)
can be made with relativel
y

(p ) y
small changes in firing angle
 Two methods to control DC output voltage

Bh ith tibt thDClt dth

B
y c
h
ang
i
ng
th
e ra
ti
o
b
e
t
ween

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

)
 Constant current control (I
order
)
 Current is kept constant with voltage variation by
varying the firing angle
AB: alpha min
BC: constant current
characteristic
Source: Alstom
eBook for You
Basic Rectifier/Inverter Static
14
HVDC STATIC CHARACTERISTICS
Characteristics
 Rectifier operation: firing angle below 90°
 Inverter operation: firing angle above
90°(extinction angle γ)
AB: alpha min
BC XC: constant current
BC
,
XC:

constant

current
Characteristic
XY: gamma min
Source: Alstom

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

Source: Alstom
eBook for You
Basic Re
q
uirements of the Converter
16
HVDC STATIC CHARACTERISTICS
q
Control System

Flow from converter A to converter B

Flow

from

converter

A

to

converter

B

AB: alpha min
BC: constant current
Characteristic
XY: constant gamma

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

A

Source: Alstom
eBook for You
Firing Angle Characteristics
18
HVDC STATIC CHARACTERISTICS
Firing

Angle

Characteristics

A: Variable
α
i
and constant V
AC

A:

Variable

α
m
i
n
and

constant

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

V
AC
 B: Constant γ and variable V
AC
Source: Alstom
eBook for You
DC Power Characteristics
20
HVDC STATIC CHARACTERISTICS
DC

Power

Characteristics
 A given increase in power order will have
a disproportionate change in DC current
a

disproportionate

change

in

DC

current

order (due to variation in DC voltage)

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

HVDC

MODEL

IN

LOAD FLOW
eBook for You
Short
Circuit Level Requirements
23
EQUIVALENT HVDC MODEL IN LOAD FLOW
Short
-
Circuit

Level

Requirements

For LCC
-
HVDC the system must be strong

For

LCC
HVDC
,

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

eBook for You
Reactive Power
25
EQUIVALENT HVDC MODEL IN LOAD FLOW
Reactive

Power
 LCC-HVDC converters consume reactive
power at both ends
 Reactive power requirements ≈ 50% of
P
rated
 Harmonic filters can provide between 50%
and 100% of the required VARS
eBook for You