FACTs - STATCOM for Q power Compensation

STATCOM presentation

1. H64APCH64APC
FACTsFACTsandDistributedandDistributed
PowerSystemsPowerSystems
1
STATCOMSTATCOM––APowerAPower
ElectronicSystemElectronicSystem

2. STATCOM
Powerconverterconnectedviaacoupling
inductortothepowersystem
Behavesasacurrentcontrolledsource
Injectscurrentwithleadingorlagging
powerfactorontothepowersystem
IfVpcc(Voltageatpointofcommon
coupling)remainsreasonablyconstant,
2
coupling)remainsreasonablyconstant,
theSTATCOMcanbeconsideredasa
sourceofleadingorlaggingreactive
power
Hasveryfastcurrentcontrolloopsand
canreactquicklytomaintainsystemvoltage

3. STATCOM
pwm
V
dc
V
pcc
V
3
ControlledCurrentSource
ControlVpwmwithrespecttoVpccto
controlthecurrentintheinductor
(andinjectedintothesupply)
IdenticalstructuretoSinusoidal(PWM)
Rectifier

4. PrincipleofOperation
IstatcontrolledtoleadVpcc(phase)by90
o
MagnitudeofIstatdeterminedby
1.Specificreactivepowerdemandfrom
systemwidecontroller
2.LocallycontrolledtoregulateVpcc
Weconsidertheapplicationwhereitisused
4
Weconsidertheapplicationwhereitisused
tocontrolVpcc
Considerbehaviourofasimplesysteminthe
presenceofaloadchange

5. PhasorDiagrams
5

6. Control
Nestedcontrolsystemnormallyemployed
OuterloopmeasuresandcontrolsVpccto
matchareferencevalueVpcc*
Outerloopprovidesreferenceforthe
magnitudeofIstat
Innerloopprovidesfastcontrolofthe
current.
6

7. ControlDesign
Assumeidealinnercurrentloop
E.g.vectorcontrolorhysteresiscontrol
Needmodelofthesystemtodesignouter
voltagecontroller
Considersteadystate
7

8. ControlDesign
8

9. ControlledVoltageSource
pwm
V
dc
V
pcc
V
9
VoltageSourceInverter(VSI)
ConvertsDCtoAC(forsimplicityassume
Vdcisanidealvoltagesource
Usespulsewidthmodulation(PWM)
Vpwmapproximatesasinewavewithlarge
carrierharmonics
Inductorreducestheeffectofthecarrier
harmonics

10. PWM
Consider one leg only–care must be taken not to switch Q1
and Q2 simultaneously–a lockout delay is introduced between
the switching off of 1 device and the switching on of its partner
10
Sa Sb Ia V
ax Conducting Device
1 0 + Vdc/2 Q1
1 0 - Vdc/2 D1
0 1 + -Vdc/2 D2
0 1 - -Vdc/2 Q2

11. PWM
Vax, Vbx and Vcx are switched between Vdc/2 and–Vdc/2
and have pulse widths which vary sinusoidally at the desired
frequency–pulsewidth modulation (PWM)
11

12. PWM
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Modulation and
Carrierwaves for PWM
12
0 0.010.020.030.040.050.060.070.080.090.1
-1
0 0.010.020.030.040.050.060.070.080.090.1
-0.5
0
0.5
1
1.5
PWM
Output

13. PWMSpectrum
A typical spectrum of V
AX
would look like:
0.2
0.25
0.3
0.35
0.4
0.45
h
a
r
m
o
n
ic

a
m
p
lit
u
d
e
output voltage spectrum
fundamental
13
0 10 20 30 40 50 60 70 80 90 100
0
0.05
0.1
0.15
harmonic
h
a
r
m
o
n
ic

a
m
p
lit
u
d
e
carrier and sidebands
second carrier and sidebands
Would probably employ a passive shunt bandpass
filter tuned to the switching frequency

14. ABBStatcom
14
•STATCOM connected to 32kV secondarybus
•95MVA
•Series connection of IGBTs
•Diode Clamped Converters