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Discrete Stability Controls for Transient and Oscillatory Stability
Douglas Wilson, Natheer Al-Ashwal (Psymetrix, UK)
Hallgrimur Halldorsson (Landsnet, Iceland)
Stephen Boroczky (AEMO, Australia)
24th July 2013
IEEE GM Discrete Control - 23/07/2013 - P 2
Introduction
Introduction
Oscillations
Transients
Conclusions
Qestions
Addressing dynamics issues
Constraint relief and security
Observing and controlling
Roadmap to Real-Time Stability Actions
7
15
22
2
Psymetrix & Alstom WAMS Activities
Advanced Phasor
Framework
• Data Management
• Analysis Tools
• Visualisation
Phasor
Applications
• Reliability
• Constraint Relief
• Dynamic Performance
• Renewables Integration
• Wide-Area Control &
Protection
Consulting
Services
• WAMS Deployment
• Dynamics & Control
• Operations & Planning
Guidance
• Power System Analysis
IEEE GM Discrete Control - 23/07/2013 - P 3
2012/13 Distribution:
Wind control; microgrid
1999 National Grid:
Security Constraint relief
Global Activities
Addressing Power System Challenges
2009 Energinet.dk: Renewable
integration, oscillations
2006 Iceland: PSS tuning,
Islanding Defence, Model
2009 Colombia: Frequency
stability, governor tuning
1995 Scottish Power: 1st
install, constraint relief
2000 Powerlink/AEMO: Synchronising
QND / NSW, constraint relief
2011 Eskom: Large WAMS, EMS integration (4,200 phasors)
2011 Manitoba:
SVC-POD tuning
WECC:
300+ PMUs,
CC integration
Short-Term Voltage Stability & Voltage Rise
Long-Term Voltage Stability
Oscillatory Stability
Frequency Stability
Local & Differential Fault Protection
Transient Stability
N-x Transient / Area Angular Stability
Thermal Limits
Phasor-based Wide Area Control
P5
15 minutes Operator Dispatch
Human-in-the-Loop
3-15 seconds Automated
Dispatch
200-600ms
Phasor Primed 16-200ms
Equipment
Protection
0.6-3s
Phasor Triggered
Guided Operator Response
Automated Control Response
Phasor-based Wide Area Control Control Room EMS/DMS/WAMS Protection
Pre-contingency operations
IEEE GM Discrete Control - 23/07/2013 - P 5
Measuring Dynamic Response
SCADA
WAMS
4 sec SCADA:
apparently small change
PMU data shows much
larger frequency swing and
poorly damped oscillations
WAMS Accurate time-
alignment, hence phase
displacement, is key to
identifying sources of
oscillation problems
WAMS shows grid
dynamic response,
hence use in transient &
oscillation applications
IEEE GM Discrete Control - 23/07/2013 - P 6
Oscillation Constraint Relief and Security
Introduction
Oscillations
Transients
Conclusions
Questions
Addressing dynamics issues
Constraint relief and security
Observing and controlling
Roadmap to Real-Time Stability Actions
7
15
22
2
IEEE GM Discrete Control - 23/07/2013 - P 7
• Australia – 3 damping constraints, ∑488MW, depending PhasorPoint
• Iceland – network procedures address oscillation risk (ring split)
• Colombia – Thermal / hydro dispatch constraint for frequency stability
• UK – oscillation security warning & operational guidance
Control-room Oscillation Management
Examples of WAMS-based oscillation management
Australia
3 Oscillation
Constraints
+128MW
+160MW +200MW
AREA 1
AREA 2
• Uncertainty in model limit
• Use margin if well damped
• Reduce limit if poorly damped
IEEE GM Discrete Control - 23/07/2013 - P 8
Examples of Control-Room Implementations
Presentation title - 23/07/2013 - P 9
Landsnet, Iceland WAMS mapboards for
Network & Balancing
Oscillation
Indicator
Since 1999
National Grid, UK Simple Oscillation warning
indicator & operational rules
XM Colombia V. Low frequency oscillation
monitoring hydro/thermal
balance
Oscillations Islanding
Oscillation Event Management, Australia
• Occasional instability events
• Onset time & mode frequency to diagnose
• Real-time location tools of interest
11:14:50 11:15:10 11:15:30 11:15:50 11:16:10 11:16:30
-220
-200
-180
-160
-140
Ra
w D
ata
P
ow
er
(M
W)
11:14:50 11:15:10 11:15:30 11:15:50 11:16:10 11:16:30 0
10
20
30
40
Time
0.6
Hz M
od
e
De
cay T
ime
(se
c)
3% damping
1% damping
Separation avoided, 10 April 2004
Event #1 2004 Generator returned to
service after maintenance with control
issue. Interstate line 150MW oscillations
@ 0.6Hz – separation risk. Generator
rejection restored stability.
Event #2 2010 Generator AVR
malfunction, instability of 0.3Hz QNI
mode, growing to 150MW. Operator
location tests, then AVR state change
restored stability, without generator
rejection.
#1
#2
Oscillation Source Location: Nearest PMU
P1
P2
c11 c
12
c22 c
21
Pd2 Pd1
P1
P2
c11
c12
c21
c22
Pd1
2 generators,
identical damping
2 generators,
only 1 damping
Identify PMU nearest contributing sources Which group of generators?
Which location within group?
Identify changes where damping degraded
Can use sparse PMU monitoring
No currents
IEEE GM Discrete Control - 23/07/2013 - P 11
Western Power, Australia
MGA
NBT
PJR
KW
ALB
MU
MRT
EMDWKT
50mHz, 0.045Hz
Low frequency common mode, 0.045Hz
Same amplitude everywhere
Small phase difference identify sources
IEEE GM Discrete Control - 23/07/2013 - P 12
Western Power, Australia
Source/Sink Location Map, 0.045Hz
Geographic area of main
source identified.
Degrees of 0.045Hz
Mode Phase Shift (NOT 50Hz voltage angle)
IEEE GM Discrete Control - 23/07/2013 - P 13
Manitoba Hydro 0.009Hz Governor Mode Northern Collector System
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3
6
8
10
12
14
x 10-3
Fre
quency (
Hz)
Event_MH121001_1100to1500LocalMH
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 320
40
60
80
100
120
140
P2P
Am
plitu
de (
mH
z)
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3
-0.6
-0.4
-0.2
0
0.2
0.4
P A
mplitu
de in p
hase w
ith F
(M
W))
Time (Hours)
Kettle : K3-dc
Kettle : K1-nac
Kettle : K1-dc
Kettle : K2-dc
Limestone : H1
Limestone : H2
Longspruce : GS-L1
Longspruce : GS-L2
Longspruce : GS-L3
Longspruce : GS-L4
Longspruce : GS-L5
Osc
illat
ion
Am
plit
ude
O
scill
atio
n C
ontr
ibu
tion
Raised oscillation
amplitude
Specific signals
show raised
contribution
(NOT Amplitude)
NOTE: The oscillations occur in the Northern Collector System, connected to the
Eastern Interconnection by a DC corridor
Un
it Po
we
r Ou
tpu
ts
IEEE GM Discrete Control - 23/07/2013 - P 14
Observing and Controlling Transient Stability
Introduction
Oscillations
Transients
Conclusions
Questions
Addressing dynamics issues
Constraint relief and security
Observing and controlling
Roadmap to Real-Time Stability Actions
7
15
22
2
IEEE GM Discrete Control - 23/07/2013 - P 15
Angle-based Wide Area Defence
SW FREQ
E FREQ
Smelter load
132kV ring power
Main generation area
Loss of Large
Smelter in SW
Islanding
Frequency rises
rapidly
Nearby generators change
speed/angle quickly
Frequency rises
more slowly
Trip Gen
proportionally
in correct zone
Angle difference
increase
IEEE GM Discrete Control - 23/07/2013 - P 16
Disturbance Record – 1 Sept 2010
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-100
-80
-60
-40
-20
0
20
40
Time (sec)
Angle
diffe
rence (
rad)
SIGALDABLANDA
A
BLANDAB
FLJOTSDALUR
KRAFLAFLJ
BusA
FLJBusB
HRA
HRA-FLJ
Diff: 25º
Time: 0.23s
HRA-FLJ
Diff: 50º
Time: 0.41s
Blanda bus tie
opening T=0.5s
-0.2 0 0.2 0.4 0.6 0.8 1
50
50.2
50.4
50.6
50.8
51
Time (sec)
Syste
m F
requency (
Hz)
SIGALDABLANDA
A
BLANDAB
FLJOTSDALUR
KRAFLAFLJ
BusA
FLJBusB
HRA
HRA Frq >50.2Hz
Time: 0.04s
Slower Frq
rise at FLJ
HRA
FLJ
IEEE GM Discrete Control - 23/07/2013 - P 17
∆𝛿 Threshold ∆𝛿
∆𝑓
∆𝑓 Threshold
∆𝛿, ∆𝑓 Relationship
WADS Generation Tripping
Angle Difference
Frequency Difference
Landsnet WADS Triggering Zone
IEEE GM Discrete Control - 23/07/2013 - P 18
Testing with Measurements & Simulation
Pink background =
trip criteria met
Measurements show:
• Restraint when not
required
• Triggering when required
• Confirm thresholds
Simulations show:
• Triggering conditions
met for “family” of
problems
• Threshold levels
• Effectiveness of actions
IEEE GM Discrete Control - 23/07/2013 - P 19
Brazil Separation Example
Other systems show same Area Transient Stability Behaviour
• Similar Δδ & ΔF characteristics
• Separation occurs 5 sec from initial fault
• Other separation events 0.5 to 5s
• Feasible timeframe for action
Loss of Sync
Angle diff
increase 5s
ΔF sustained
5s
Fault
Event Fault Loss of Sync
#1 3 sec & 5 sec
#2 0.8 sec
#3 2.1 sec
#4 0.5s & 0.9s
GB Transient Stability Boundary with Wind
δ
(δ)
δ P
Scotland-England Boundary
~ 3.5GW Transient Stability Limit (P)
~ 1.5GW Wind Capacity in Corridor
Volatility in corridor capability
Expressing Limit as Angle?
• Transient stability closely related
to angle difference
• Should operators run to
Angle, not MW limit?
• Should new HVDC link
control by Angle?
Observing and Controlling Transient Stability
Introduction
Oscillations
Transients
Conclusions
Questions
Addressing dynamics issues
Constraint relief and security
Observing and controlling
Roadmap to Real-Time Stability Actions
7
15
22
2
IEEE GM Discrete Control - 23/07/2013 - P 22
Control Room
• Procedures for oscillations established
• Further operator guidance needed
• Transient stability benefits from angle limit thresholds
Conclusions
Automation
• Δδ, Δf for defence action proportional to system need
• Response time for wide area angle separation is feasible
• Principle applies to many inter-angle separation threats
Roadmap to Real-Time Stability Actions
Growing experience through WAMS improves control actions
www.psymetrix.com