Transcript Slide 1

Lessons Learned from the
Texas Synchrophasor Network
by
W. Mack Grady and Moses Kai, U.T. Austin
Bill Flerchinger and David Costello, Schweitzer Engineering Labs
Karen Forsten and Daniel Brooks, EPRI
Presented at the
North American Synchrophasor Initiative (NASPI) Meeting
Toronto, Ontario
Thursday, June 9, 2011
1
The Texas Synchrophasor Network
Six 120V single-phase PMUs, One 69kV three-phase PMU
Blue outlines:
Central ERCOT
Brazos Electric
PMU
McDonald
McDonald
Observatory
Waco
Wind
country
Austin
120V and
Austin
Harris 69kV
Boerne
(SEL)
Austin Energy
PMU
Houston
(SEL)
• Funding provided by EPRI
• Equipment provided by
Schweitzer Engineering
Labs
UT Pan Am
UT
Am
Concentrated distant load
2
Wind Generation in ERCOT - MW
March 25, 26, 2010
6000
Lesson 1. Every Day has
Synchrophasor Surprises
2 days
5000
Wind generation and
West Texas phase
angle can go through
large daily swings
3000
Thur
Fri
2000
1000
0
24
36
48
60
72
McDonald Observatory Voltage Phase Angle with respect to U.T. Austin
March 25, 26, 2010
60
West Texas voltage
phase angle swings
nearly 100º and back
with respect to U.T.
Austin in about 24
hours
40
20
Degrees
MW
4000
0
-20
-40
-60
24
36
48
60
4836 Hours Beginning 12am, March 24, 2010
72
3
Texas Nodal Market Has Created a New West Texas Resonant Mode with Time
Period = 30 minutes
12 hours
ERCOT’s graph of
West-to-North P flow
McDonald Observatory Voltage Phase Angle Relative to
Central ERCOT
40
Texas
Synchrophasor
Network’s graph
of West-to-Central
ERCOT Voltage
Angle
Degrees
30
20
10
0
-10
-20
0
1
2
Lesson 1. Daily surprises, cont.
3
4
5
6
7
8
Hour of March 11, 2011
9
10
11
12
4
Transmission Events Also Produce Angle Rings
2011/06/03, 00:54 GMT
McD Angle
2 minutes
• The angle ring observed at
McD and Waco was likely
caused by a transmission
event and was a precursor
to a gradual frequency
slump.
• Angle ring is approx. 1
degree peak to peak (2nd
significant digit)
• Frequency ring is only
about 0.01 Hz peak to peak
(4th significant digit)
60.02 Hz
McD, PanAm, Waco Frequencies
5 minutes
2 minutes
3600 points
Lesson 1. Daily surprises, cont.
59.94 Hz
Frequency Slump
5
Lesson 2. 120V Wall Outlets Work for Synchrophasors (of course, we would
prefer to have three-phase grid PMUs)
Voltage Ringdown at McDonald Observatory Observed at the Following Two Locations in Austin:
a 120V Wall Outlet
onObservatory
Campus,Voltage
and the
Harris
Substation
thatHarris
Feeds
McDonald
Phase
Angle69kV
w.r.t U.T.
Austin 120V and
69kVthe Campus
-10
20 seconds
10 seconds
Degrees
-11
w.r.t U.T. Austin
-12
w.r.t Harris 69kV
-13
-14
1600
1700
1800
1900
2000
2100
2200
Sample (30 samples per second)
• The fixed net multiple of 30 degree phase shift between U.T. Austin 120V and Harris 69kV has been
removed. The variable but steady power flow phase shift through the substation transformer has
also been removed.
6
Steady-State Voltage Angle Between Austin Energy 69kV Substation Monitor and
UT ECE Building 120V Wall Outlet Varies Slowly with UT Generation and Load
Week
Starting
Sunday,
Mayto29,
Voltage
Phase Angle
Relative
UT 2011
Austin
1-Minute Averages, Beginning Sunday, May 29, 2011, Beginning 00:00 CDT
1 week
Degrees
1
0
Ha
-1
0
24
Note – angles shown
were rounded to 0.1º
Lesson 2. 120V OK, cont.
48
72
96
120
144
168
Hour of the Week, CDT
7
Lesson 3. You Can Estimate Thevenin Equivalent Impedances Across the
Grid with Synchrophasors
Vangle = δ
Pexport
Bus 7
WIND
500 km
Thevenin Impedance
jXTH
Central
ERCOT
Vangle = 0
Local conventional
Pload,conv − Pgen,conv
Use the Excel Solver with angle measurements to minimize least-squared error
and obtain Xth
McDonald Observatory Voltage Phase Angle Relative to
Central ERCOT
40
Degrees
30
V1V2
P
 sin( )
X TH
20
10
0
-10
-20
0
1
2
3
4
5
6
7
8
Hour of March 11, 2011
9
10
11
12
8
Lesson 4. A Small but Tightly-Clustered 2 Hz Mode in Ambient Oscillation
Sometimes Forms with High Wind Generation
Small Wind (2%) without 2 Hz Cluster
March 12, 02:00 – 03:00
Wind Generation ≈ 2%
Big Wind (20%) with 2 Hz Cluster
March 18, 02:00 – 03:00
Wind Generation > 20%
1 hour
2 Hz
Cluster
9
Lesson 5. Wind Generation Does Not Appear to Impact System Damping or
Damped Resonant Frequency
5 minutes of frequencies
59.74
McD
Modest
wind
1 minute of angles
PanAm
Waco
10
Let Excel Solver Curve Fit the 2nd Order Damped Response
Start Sec
5.5
Stop Sec
11
Exponential Steady State Transition Curve
A
B
T1
Tau1
17.05
18.58
5.91
0.24
Steady-State Change
= 18.58 – 17.05 = 1.53
degrees
C
1.73
T2
6.18
Damped Sinusoidal Term
Tau2
Tdamp
Fdamp
4.64
1.59
0.628
Zeta
0.055
Damped Resonant
Frequency, Hz
Ring Magnitude, degrees
Unit Trip 2011/05/30 03:03:00 GMT. UT Pan Am Relative to U.T. Austin.
Measured
Avg. Sum
Squared Error
0.0044
Alpha
0.215
F0
0.629
Normalized
Damping Ratio
Total Curve Fit
21
10 seconds
Degrees
20
19
18
(t T1 )
17
B   A  B   e 1
16
5
6
7
8
(t T2 )
 u(t  T1)  C  e  2
9
10
11
 sind (t  T2 ) u(t  T2 )
12
13
14
15
Second
Lesson 5. Wind does not impact damping, cont.
11
Ringdown Analysis of More Than 100 Unit Trips Yields No Clear Relationship
Between Wind MW and Normalized Damping Ratio
Damping Ratio vs Wind Generation (% of Total), Sep 2009 - Feb 2010
1.2
Does Wind
Generation
Impact Grid
Stability?
Normalized Damping Ratio
6 months
1
0.8
0.6
0.4
0.2
0
0
2
4
6
8
10
12
14
16
18
20
Wind Generation (% of Total)
Lesson 5. Wind does not impact damping, cont.
12
Lesson 6. Wind Generation Does Not Appear to Reduce System Inertia
(but no generator operating at max power can contribute to governor
response)
EPRI Study. Purpose – to compute ERCOT System Inertia Constant H From Frequency
Response During 42 Unit Trips Having 0.1 Hz or Greater Freq. Drop.
2 minutes
Zoom
10 seconds
Event 7, 8/24/2010 07:31:00 PM GMT Minute
60.00
59.98
59.96
Frequency
59.94
UT Austin
59.92
Harris 69
McD
Nadir
slope
59.90
59.88
59.86
UT PanAm
Inertia
slope
59.84
59.82
56
57
58
59
60
61
62
Second of the Minute
63
64
65
66
13
42 Major Unit Trips, 0.1 Hz or Greater. Any Correlation Between System
Inertia and Wind Generation (% of Total Gen)?
6 months
Estimated System H versus % Wind Generation
(42 Unit Trip Events, June through November 2010)
12
Estimated H
10
8
6
4
2
0
0
5
10
15
20
Wind Generation - % of Total Generation
Lesson 6. Wind does not reduce system inertia, cont.
14
Texas Synchrophasor Network
Thanks to
•
Schweitzer Engineering Laboratories, especially Mr. David Costello,
for providing all the equipment and technical support that we need
•
EPRI, especially Ms. Karen Forsten and Mr. Daniel Brooks, for past,
present, and future funding of graduate students and faculty summer
support
•
Startup money in 2008 from the Texas Governor Rick Perry’s Emerging
Technology Fund through CCET, Dr. Milton Holloway
•
Austin Energy, especially Mr. Scott Bayer, for installing the 69kV
phasor measurement unit, and providing advice on system operating
and protection
•
Mr. Andrew Mattei of Brazos Electric, Waco, for installing and
operating a 120V PMU
•
PhD student Moses Kai at U.T. Austin for his dedication and research
in synchrophasors and their applications to power grids
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