Douglas Wilson, Natheer Al-Ashwal

October 2014

Identifying Sources of Oscillations Using Wide Area Measurements

2014 Grid of the Future Symposium

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 2

Introduction

Need for Source Location in Managing Oscillations • Oscillation Identification long established

− Real-time control-room measures on known modes since 1998 (GB inter-area 0.5Hz) − Monitoring reveals previously unseen behaviour and risks

• Oscillation behaviour can be complex − Many plants, loads, controllers participating over wide area − Issues not replicated in models e.g. interaction/resonance, plant malfunction, forcing

• Decisions on actions (real-time or planning) require information to identify sources − Applicable to interconnection (is source in my area?) − “Largest amplitude” an unreliable indicator − Assume incomplete observability (especially currents)

12 minutes 30 mHz

100MW (1 line)

0.26Hz

New method yields Source Identification using Sparse Voltage Bus Measurements

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 3

Oscillation Phase Relations for a Single Machine

• P and δ lag ω by about 90°, determined by damping. E.g. damping ratio 20%, angle lags 90°+12° and power lag speed by 90°-12°

• Power (P) in phase with speed (ω) produces positive damping.

• Power out of phase with speed produces negative damping.

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 4

2-Machine Example

Lagging generator contributes more damping than leading generator Leading generator is “source”

More Damping Contribution from Generator 1

Equal Damping Contributions More Damping Contribution from Generator 1

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 5

Identifying Sources of Oscillations

Example • Leading phase indicates less

damping contribution.

• The “source” is the location with the lowest damping contribution (possibly negative).

• To find the source of an oscillation: 1. Divide into opposing groups. The

group leading by less than 180° is the group containing the source.

2. Find the most leading location within the leading group.

0.005

0.01

0.015

30

210

60

240

90

270

120

300

150

330

180 0

Gen 1Gen2Gen3Gen4

Gen 2 is the Source

Gen 1 & 2 are the leading group.

Gen 2 leading within group

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 6

-4

-2

0

2

4

Angle

Osc

illatio

ns (D

egre

es)

0 100 200 300 400 500 600Time from start of oscillations(seconds)

Real System Case from ISO-NE Undamped 0.9 Hz oscillations after disturbance, 10 minutes.

621.8 622 622.2 622.4 622.6 622.8 623 623.2 623.4-0.2

-0.1

0

0.1

0.2

0.3

0.4

Time (seconds)

Ang

le O

scill

atio

ns (D

egre

es)

PMU19PMU30PMU31PMU34

• Amplitude and Phase differences in time domain signals.

• Group of PMUs 19,30,31 leads PMU 34 by less than 180° source group is PMUs 19, 30, 31

• Within source group, phase

PMU31PMU30PMU19. PMU31 is source

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 7

Mode Shape from all 39 measured locations.

0.2

0.4

0.6

0.8

1

30

210

60

240

90

270

120

300

150

330

180 0

0.2

Group1Group2

Angle Only

Angle & Magnitude

Group 1 Leading (cluster)

Leading within G1

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 8

Group Phase difference

0 100 200 300 400 500 600 700

90

100

110

120

130

140

150

160

Time from start of oscillations(seconds)

Gro

up1-

Gro

up2

Pha

se (D

egre

es)

• First results obtained after 10 seconds.

• Group weighted average angles

• Group 1 is leading by 130-150º (i.e. leading by <180º), less damping provided by Group 1 than Group 2.

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 9

Most Leading Locations Within Group 1

0 100 200 300 400 500 600 700-10

0

10

20

30

40

50

60

Time from start of oscillations(seconds)

Pha

se (D

egre

es)

PMU19PMU23PMU30PMU31

• Within Group 1, PMU31 is leading small or negative damping near PMU31.

• If PMU31 was not available, PMU30 would be indicated, which is near PMU31, but much lower mode amplitude. Correct conclusion would be reached without PMU31.

Correct Conclusion to Nearest PMU, even without Large Amplitude

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 10

Application to Large Interconnection

Largest Contribution Change

Group 1 Contributions Group 2 Contributions

Reference time Current / selected time

Largest Group Change

Group 1 Contribution

Reference Current

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 11

Concern • Are there significant oscillations

in interconnection?

• Is my system involved?

• Can the oscillation be controlled within my area?

• What measures can I take?

− Operationally

− Planning & control design

Solution • Alarm on unusually large or poorly

damped oscillations

• Check high level geographic interconnection source location view

• Compare contributions inside & outside system – action if source(s) within system

• Identify specific source plant(s) in detailed measurements

− Change V/VAR dispatch, P dispatch if necessary. Inform plant.

− Improve PSS, SVC-POD control design at key plant(s). Confirm wide-area response after commissioning

Application to Large Interconnections

Approach can be applied to a large interconnection by sharing a high-level sparse set of voltage phasor measurements

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 12

Application to PSS tuning

Identify damping contribution with different PSS settings

SIG-PSS

Network Switch

PSS Enabled

PSS Disabled

Switching Tests (opening)

Mode Frq Damping SIG-FLJ

Phase Change

PSS OFF 0.34 4.2% -167.1 0 PSS #1 ON 0.33 6.8% -156.2 10.9 PSS #2 ON 0.33 2.3% -167.3 -0.2 PSS #3 ON 0.33 6.3% -154.3 12.8

Freq

uenc

y, D

ampi

ng, P

HAS

E

FLJ

FLJ

SIG-PSS #1, #3

SIG-PSS OFF, #2

Group Contribution

Improves

© ALSTOM 2014. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

Presentation title - 23/10/2014 – P 13

Conclusions

• Novel measurement-based oscillation source location − Applied to voltage phasors − Uses oscillation phase relationships for contributions − Not dependent on observing largest amplitude

• Applied to recorded example from ISO-NE − Instability at 0.9Hz observed throughout ISONE − Leading phase indicated source of oscillation (large amplitude only in 1 measurement) − Phase method gives correct outcome, even without the

large-amplitude measurement

• Applicable from small systems to large interconnections − High-level wide-area view − Detailed control area view

• Applicable in Real-Time or Analysis timeframe

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