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

7

-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

20

• Parallel SVC operation – master/slave

• Undervoltage Strategies

• Slow var control

• Gain optimization control

Control Verification & Testing

21

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