FACTS and HVDC systems in Power Engineering

FACTS and HVDC systems in

Power Engineering

AE1M15PRE

2

What is FACTS?

• FACTS = Flexible AC Transmission Systems

• IEEE:

– FACTS: Alternating current transmission systems

with static regulator integrated or based on high

power electronic technology. Used for power flow

control and transmission line capacity increasing.

– FACTS controller: Unit with high power electronic or

static, which allows controlling of one or several

parameters of AC transmission system.

3

Power transmission

• Limits

– thermal (current)

– dialectical (voltage)

– stability (static and

dynamic)

• Power flow control

– Line impedance X

– Load angle d

– Voltage U, j

– Injection of P,Q

121

2 PsinX

UUP d

I XU

2U

1

P1+jQ

1 P2+jQ

2

X

Ucos

X

UUQ

2

2212 d

4

Power flow

I

U1

U2d

j2

j2

jXII X

U2

U1

P1+jQ

1 P2+jQ

2

222 cosIUP j

dj sinUcosXI 12

dj sinX

UcosI 1

2 121

2 PsinX

UUP d

5

Power flow

I

U1

U2d

j2

j2

jXI

I XU

2U

1

P1+jQ

1 P2+jQ

2

222 sinIUQ j

dj cosUUsinXI 122

X

Ucos

X

UsinI 21

2 dj

X

Ucos

X

UUQ

2

2212 d

2

21 XIQQ

d

d

cosUU2UUX

1

X

Ucos

X

UUQ

21

2

2

2

1

2

2211

d cosX

UU

X

UQ 21

2

11

6

P-Q transmission diagram

d sinX

UUP 21

2

X

Ucos

X

UUQ

2

2212 d

I XU

2U

1

P1+jQ

1 P2+jQ

2

2

21

22

22

2

2X

UU

X

UQP

dd

X

UUr

X

US 21

2

2 ,,0circle

7

Control principles - passive

• Shunt

• Series

8

Control principles - active

• Shunt

• Series

9

Convertors

• Thyristor unit

• Three phase

convertors (VSC)

10

Voltage Source Convertor(VSC)

• Switching element (GTO, IGBT, IGCT)

• Pulse Width Modulated (PWM) –Umax,j,50 Hz

• High harmonics filters

• DC circuit – high capacity C or DC source

– C – I orthogonal to U only Q control

– source – any phase shift P,Q control

• Connected to the line through transformer

– shunt – ind., cap. current U regulation

– series – voltage injection P,Q regulation

11

FACTS

1) series 3) combined (universal)

2) shunt U

Line

I

Line

I

Line

U

DC

12

FACTS

• Shunt

TSC – Thyristor Switched Capacitor

TCR – Thyristor Controlled Reactor

13

FACTS

• Shunt

SVC – Static Var Compensator

STATCOM – Static Synchronous Compensator

VSC

DC

14

FACTS

• Series SSSC – Static Synchronous Series Compensator

TCSC – Thyristor Controlled Series Capacitor

VSC

DC

15

FACTS

• Universal

UPFC – Unified Power Flow Controller

DC

16

Application

• Power flow control (P,Q)

• Transmission lines capacity improvement

(thermal limits)

• Safety rise (higher stability limits, short

circuit currents and overload reduction,

oscillation damping)

• Voltage control

• Controllable values (U, I, X, P, Q )

interconnected, some are dominant

17

Benefits

• Fast response to the demand

• Frequent change in output

• Continuously adjustable output

18

Admittance model

• suitable for thyristor controlled convertors

19

Model TCR

0,0

0,2

0,4

0,6

0,8

1,0

90 100 110 120 130 140 150 160 170 180

BT

CR(a

) (

p.u

.)

a ( )

aaaa

a

sincos32cos22BB LTCR

20

Model SVC, TCSC

-0,40

-0,20

0,00

0,20

0,40

0,60

0,80

1,00

90,0 100,0 110,0 120,0 130,0 140,0 150,0 160,0 170,0 180,0

B(a

) (p

.u.)

a ( )

C

1L

CLTCR Bsincos32cos22

BB aaaa

a

21

Model SVC, TCSC

-20,0

-15,0

-10,0

-5,0

0,0

5,0

10,0

15,0

20,0

90,0 100,0 110,0 120,0 130,0 140,0 150,0 160,0 170,0 180,0

X(a

) (p

.u.)

a ( )

induktivní mód činnosti

kapacitníní mód činnosti

rezonance

• Resonance (TCSC) aaaaa resres

Inductive mode

Capacitive mode

22

TCSC

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

0,0 30,0 60,0 90,0 120,0 150,0 180,0

PS

(p.u

.)

d ( °)

without compensation

with compensation XTCSC = XCmin.

with compensation XTCSC = XCmax.

23

Power characteristics - TCSC

24

Power characteristics - TCSC

0,0

0,5

1,0

1,5

2,0

2,5

3,0

0,0 30,0 60,0 90,0 120,0 150,0 180,0

QS

(p.u

.)

d ( °)

without compensation

with compensation XTCSC = XCmin.

with compensation XTCSC = XCmax.

25

SVC

26

Power characteristics - SVC

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

0,0 30,0 60,0 90,0 120,0 150,0 180,0

PS

(p.u

.)

d ( °)

without comp.

with comp. XCmax.

with comp.XLmax.

27

Power characteristics - SVC

0,0

0,5

1,0

1,5

2,0

2,5

3,0

0,0 30,0 60,0 90,0 120,0 150,0 180,0

QS

(p.u

.)

d ( °)

without comp.

with comp.XLmax.

with comp. XCmax.

28

SSSC

• Power flow control

• Oscillation damping

• Transmission stability

improvement

• Voltage stability

improvement

29

SSSC

• Power flow regulation

(generation or

absorption of Q),

Upq ILine

• Injection of Upq XL,

XC in series with line

• DC source

– P supply Rline

compensation

30

SSSC

• Inductive mode

– Upq in phase with

drop UL XL

– Upq < UL else

reverse power flow

31

SSSC

Without regulation

With regulation

32

STATCOM

• Voltage value and

curve control

• Stability limits and line

capacity improvement

• Oscillation damping

• Load symmetrisation

• Voltage stability and

quality improvement

• Transmission,

distribution and

industrial application

33

STATCOM

• Voltage regulation

(load,U ; load, U),

line capacity rise P,

stability improvement

• Capacity C P

consumed to cover

losses in switches

– P low

IAC ± 90 from UAC

34

STATCOM

• Q regulation – amplitude Uout

– Uout > UAC injection Q to the system (C mode)

– Uout < UAC consumption Q (L mode)

• P regulation – by angle between Uout and UAC

a) P = 0 b) P from grid c) P to grid

35

STATCOM

Without

regulation

With

regulation

36

UPFC = STATCOM + SSSC

37

UPFC

38

UPFC

• U, P, Q regulation

– QSH, QSER independent control

– P flows from VSC1 to VSC2 (and other way)

→ performance area is circuit

– Independent control U1, U2, X, d

• VSC2

– 0 ≤ USE ≤ USEmax, 0 ≤ jSE ≤ 2, f = 50Hz

– P, Q both ways

• VSC1

– P consumption for VSC2 + losses, Q both ways

39

UPFC in the grid

• At the beginning of transmission lain is

placesed

– Operates as 2 voltage sources with variable voltage

amplitude and phase

40

UPFC – performance regimes

• Regimes : 1. Voltage regulation

2. Series compensation

3. Voltage phase control

4. Power flow control

41

UPFC – power flow control

2

2SE2

2SESE

2

2SESEX

UUQ,QP,P

djddjd

42

PST

• Phase-shifting transformer

• Active power flow control

43

PST quadrature-boosting

transformers (QBT)

phase-angle regulators (PAR)

44

HVDC

• Long-distance

transmission

• Interconnection of

power systems

• Submarine cables

• Distant sources

connection

• City and power

islands supply

• thyristors x IGBT

45

Conclusion

• FACTS = high power electronic equipment

for voltage and power control

• Lot of kinds with different properties and

characteristics

• Improve stability and reliability of

transmission system

• Numbers of applications x high price