Design and Application of SVC units in the Texas CREZ System
1
Presentation Overview
• Project Background
• CREZ Transmission System Characteristics
• SVC Design
• Reliability and Availability
• Control Features
• SVC Operation This Far
2
Project Background • Five Competitive Renewable Energy
Zones (CREZ)
• Transmission system to facilitate 12 GW Wind
• Future expansion to 24 GW
• ERCOT studies identified need and location for dynamic shunt and series compensation
• 2300 miles additional right of way required
3
Source ERCOT
System Properties • None or very limited amount of
conventional synchronous generation
• System sensitive to 345 kV double circuit outages
• Radial type of system bound by power angle criterion limitation
• Large portion of low inertia induction motor load
• Angles between WTG and receiving end over 90 transiently
• High sensitivity to overvoltage conditions
4
System Properties • This is a system subject to fast voltage
collapse
• In need of dynamic reactive power reserve – capacitive and inductive
• Sizing, Controllability and Location essential
• Sizing – Units to have wide enough dynamic range not to operate at limit
• Controllability – TCR/TSC based SVC units
• Location – Optimal location determined from studies by ERCOT
5
6
The CREZ Transmission System
Tesla
Source ERCOT
Hamilton Rd
The SVC Units – Tesla Substation
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-3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50
0.2
0.4
0.6
0.8
1
1.2
1.4
A BC D
<=================== Capacitive =============== SVC current [pu] =================== Inductive ==============>
Prim
ary
vo
lta
ge
[p
u]
AEP CREZ - TESLA SVC, 345 kV side VI-diagram
A - Nominal Initial Build Capacitive Rating
B - Nominal Initial Build Inductive Rating
C - Nominal Ultimate Build Capacitive Rating
D - Nominal Ultimate Build Inductive Rating
• Two SVC Units in Parallel at
Each Site
• 66 Mvar inductive
150 Mvar Capacitive
(initial build)
• 150 Mvar inductive
300 Mvar Capacitive
(ultimate build upgrade)
• Hamilton Rd units (138 kV)
25 Mvar inductive
100 Mvar capacitive
The SVC Units – Tesla Substation
8
TCR
122 Mvar
3rd
Harmonic
Filter
42 Mvar
TSC
94 Mvar
5th
Harmonic
Filter
14 Mvar
300 MVA
345/20.5 kV
300 MVA
345/20.5 kV
345 kV
TCR
122 Mvar
3rd
Harmonic
Filter
42 Mvar
TSC
94 Mvar
5th
Harmonic
Filter
14 Mvar
The SVC Units – Tesla Substation
9
SVC Design Criteria
10
• Dynamic Behavior
• Harmonic Performance – System Impact
• SVC Reliability
• SVC Controls
• Control Verification & Testing
SVC Harmonic Performance
11
• System Harmonic Impedance
– Varies with frequency
– Unlinear
– Varies depending on contingencies (N-0, N-1, N-2)
– Varies depending on type of generation
– Varies depending on type of load
– Result highly dependent on choice of modelling
© ABB Group May 2, 2014 | Slide 12
SVC
Znet
For each harmonic frequency
5 10 15 20 25 300
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4Harmonic Impedance Magnitude
Harmonic Frequency (n)
|Z| (
pu)
5 10 15 20 25 300
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4Harmonic Impedance Magnitude
Harmonic Frequency (n)
|Z| (
pu)
For many system conditions
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.15th Harmonic Impedance
Resistance (pu)
Rea
ctan
ce (pu
)
System Harmonic Impedance
System Harmonic Impedance
13
• Different wind scenarios sub-grouped in areas
• HIS based on peak load power flow cases
• Loads reduced to 50% to reduce system damping
• Series connected RL – RC combinations
• Modified Bergeron model T-line representation
• Transformer models, frequency dependent losses
• Wind turbines generic PSCAD models
Harmonic Impedance – Load Modelling
14
Harmonic Impedance – WTG Modelling
15
SVC Reliability & Availability
16
• Design to maximize contingency readiness
– Minimize number of forced outages
– Maximize up-time
< 2 Forced outages per year (< 3 first year)
99% FOA , 98.5% SOA, 97.5% Total Availability
SVC Reliability & Availability
17
• Auxiliary Power Supply of SVC MV bus
• UV strategies vary for different aux systems depending on their specific requirements
• Redundancy in Controls, thyristor valves, cooling pumps and fans
• Reduced mode operation
• On site spare transformer
SVC Reliability & Availability
18
Expected values
SVC Control & Protection
19
SVC Control & Protection
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• Parallel SVC operation – master/slave
• Undervoltage Strategies
• Slow var control
• Gain optimization control
Control Verification & Testing
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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1-2
-1
0
1
2
UP
1_
A [
pu
] U
P1
_B
[p
u]
UP
1_
C [
pu
]
File: CNT M2FA_S2P1CNTA1 1 20121121 03;38;32_252000.CFG
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1-4
-2
0
2
4
IP
1_
A [
pu
] I
P1
_B
[p
u]
IP
1_
C [
pu
]
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.10.2
0.4
0.6
0.8
1
1.2
VR
ES
P [
pu
]
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.10.75
0.8
0.85
0.9
0.95
1
RE
L_
GA
IN [
pu
]
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1-1
0
1
2
Time [s]
BR
EF
[p
u]
Thanks for Your Attention
Questions
Design and Application of SVC units in the Texas CREZ System
22