1 security assessment: decision support tools for power system operators james d. mccalley,...
TRANSCRIPT
![Page 1: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/1.jpg)
1
Security assessment: decision support tools for power system operators
James D. McCalley, [email protected]
Iowa State University, Ames, Iowa
September 5, 2000
© Iowa State University. All rights reserved.
![Page 2: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/2.jpg)
2
Overview
Security-related decisions
Current approach and what’s wrong with it
Security assessment using probabilistic risk
Illustrations
Risk-based decision-making
Cumulative risk assessment
Conclusions
![Page 3: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/3.jpg)
3
On-line Operator How to constrain the Operating rules,assessment economic operation to on-line assessment,(min-hours) maintain the normal state ? and $$$$
Security-related decisions
Time-frame Decision maker Decision Basis for decision
Operational Analyst What should be the Minimum operating
planning operating rules ? criteria, reliability,
(hrs-months) and $$$$
Planning Analyst How to reinforce/maintain Reliability criteria
(months-years) the transmission system ? for system design,
and $$$$
![Page 4: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/4.jpg)
4
Decision-Drivers Security
Overloadsecurity
Voltage Security
Dynamic Security
Trans- former Overload
Line Overload
Low Voltage
Unstable Voltage
Transient(early-swing)instability
Oscillatory (damping)instability
![Page 5: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/5.jpg)
5
Number of operating studies for determining security limitsNational Grid Company, UK
1985: 3/quarter
1990: 120/week
2000: 1300/week
![Page 6: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/6.jpg)
6
Bus 1 500
Bus 1 230
Bus 1 115
Bus 2 500Bus 2 500
Bus2 230Bus2 230
Bus 2 115Bus 2 115
110%
Imports Operator’s view Operator’s view at 2:10 pm, at 2:10 pm, 8/12/998/12/99
200 MW flow
94%
93%
0.95 pu volts
A Stressed A Stressed SystemSystem
![Page 7: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/7.jpg)
7
Simulation Simulation Results of a Results of a Preventive ActionPreventive Action
Bus 1 500Bus 1 500
Bus 1 230Bus 1 230
Bus 1 115Bus 1 115
Bus 2 500Bus 2 500
Bus2 230Bus2 230
Bus 2 115Bus 2 115
103%
Imports
0 MW flow
101%
104%
0.91 pu volts
![Page 8: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/8.jpg)
8
Power system “states” and actions
Normal (secure)
Emergency
Restorative
Extreme emergency.Separation, cascading
delivery pointinterruption,
load shedding
Alert,Not secure
Off-economic dispatch
Controlled loadcurtailment
Transmission loading reliefprocedures
Other actions(e.g. switching)
![Page 9: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/9.jpg)
9
Model current conditions
Select contingencies
Compute post-contingency performance
Determine if alert(the action-trigger)
Identify possible actions
Select action
Assessment and decision today
Determine if alert(the action-trigger)
Identify possible actions
Select action
Perform assessment
a-priori
![Page 10: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/10.jpg)
10
What is wrong with this approach?
#2The decision is driven by the most severe credible contingency
#1Assessment is made of the past but the decision is made for the future.
![Page 11: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/11.jpg)
11
What is wrong with this approach?
#1Assessment is made of the past but the decision is made for the future.
• actions can come too late
• un-quantified future uncertainties requires large margin
![Page 12: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/12.jpg)
12
Actions can come too late;Un-quantified uncertainties require large margin
Line flowContingency-based flow limit
Time
MW
Select action
Assess Action trigger
Identifyaction set
Based on the previous condition
![Page 13: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/13.jpg)
13
What is wrong with this approach?
#2The decision is driven by the most severe credible contingency
• inaccurate assessment and consequently an inconsistent action trigger• selection of less effective actions
![Page 14: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/14.jpg)
14
4
3 2
1
5
1
2
3
4
5
6 7
8
Five-bus test system for illustrating concepts
Loss of cct 1 overloads cct 2
Loss of cct 6 overloads cct 7
Loss of cct 5 createslow voltage at bus 4.
![Page 15: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/15.jpg)
15
A
B
C D
E
![Page 16: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/16.jpg)
16
![Page 17: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/17.jpg)
17
What causes the inconsistency?Assumption that all contingencies in selected set are of equal probability
Ignoring risk contribution from problems that are not most constraining
Discrete quantification of severity
![Page 18: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/18.jpg)
18
What do we do then?
Model a forecasted future
using probabilistic modeling of uncertainties
and assess it with
quantitative evaluation of contingency severity for each possible condition
![Page 19: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/19.jpg)
19
Forecast the future load and transactions
forecasted line flow95% confidence limitsactual line flow
Time
MW Loading
Select action
Assess Action trigger
Identifyaction set
(Based on future Conditions)
![Page 20: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/20.jpg)
20
On-line risk-based assessment
∑∑ ×=i j
jtiftjtift XESevXXEXSevRisk ),()|Pr()Pr()|( ,,,,
Uncertainty inoutage conditions
Uncertainty in operating conditions Severity
function
Forecasted operating conditions for future time t
![Page 21: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/21.jpg)
21
Possible near-future operating cdts (bus injections)
Selected near-futurecontingency states
Determine low voltageseverity for each bus
Determine overloadseverity for each circuit
Determine voltage instability severity for the system
MM
Forecasted operating
conditions Determine cascadingseverity for each circuit
![Page 22: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/22.jpg)
22
• Xt,f is forecasted severity measures: flows, voltages, loadability
• Xt,j is small deviation from forecasted value due to variation (or uncertainty) in parameters k:
kk
XXX ftjt Δ
∂∂
+= ,,
Then, the pdf on Xt+1 can be obtained as:
),(~)|Pr( ,,,
T
ftftjt k
XC
k
XXNormalXX ⎥⎦
⎤⎢⎣
⎡∂∂
⎥⎦
⎤⎢⎣
⎡∂∂
C is the covariance matrix for the vector of uncertain parameters k
Uncertainty in operating conditions...
![Page 23: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/23.jpg)
23
Severity modeling
LOLP, EUE, Cost of re-dispatch, as indices for use in security-related decision-making, each pre-suppose adecision and are therefore inappropriate.
It’s modeling should NOT depend on a pre-supposed decision as this constrains the decision space, which is the space of investigation.
Re-dispatch
Loa
d cu
rtai
lmen
t
Trans
miss
ion
load
ing
relie
f
Identified by CIGRE TF38.02.21 Task Force asmost difficult problem in probabilistic security assessment.
![Page 24: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/24.jpg)
24
Severity modeling: essential features
Definition: Severity is an unavoidable consequence of a specified condition.
It provides a quantitative evaluation of what would happen to the power system in the specified condition.
One uses it, together with probability of the condition, to decide whether to re-dispatch, call for TLR, or interrupt load.
![Page 25: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/25.jpg)
25
Severity modeling
Economic quantification is attractive but difficult and can give a false sense of precision.
Essential features• Simple.• Reasonable reflection of relative severity between outcomes to enable calculation of a composite index. • Increase continuously as the performance indicator (e.g., flow, voltage, loading margin, cascaded lines) gets worse.• Interpretable in physical and deterministic terms.
![Page 26: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/26.jpg)
26
Voltage in per unit
Severity
Flow as % of rating
10090
1
Severity
0.950.92
1
OVERLOAD
Severity
MW loading margin
1100 100
1
Severity
Number of cascaded circuits
1 2 3 4 5 …
654321
Severity functions...
Because all severity functions evaluate to 1.0 at the deterministic threshold, a risk level R may be roughly thought of as the expectationOf the number of violations in the next hour.
100
LOW VOLTAGE
CASCADINGNote: non-convergenceat any level of cascading evaluates to 100.
VOLTAGEINSTABILITY
![Page 27: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/27.jpg)
27
))},(CasNum()),(VCMargin(
)),(Voltage()),(Flow({
)|Pr()Pr()|(
,1,1
,1,1
,1
jtiCasjtiVC
bjtibb
cjticc
i jtjtit
XESevXESev
XESevXESev
XXEXSevRisk
++
++
+
++
+
×=
∑∑
∑∑Decomposability
The above expresses system risk.
Interchanging summations allows us to obtain:• What incurs risk: total risk for a single component (bus or branch risk) or a set of them (regional risk)• What causes risk:
system, regional, or component risk for a specific contingency system, regional, or component risk for a specific problem type
![Page 28: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/28.jpg)
28
![Page 29: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/29.jpg)
29
![Page 30: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/30.jpg)
30
![Page 31: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/31.jpg)
31
Decision-making by RBOPF
Traditional OPF:
Minimize: generation cost
Subject to:
Power flow equations
Generation limits
Branch flow & bus voltage constraints
Other security constraints
A variation:
Minimize: a(generation cost) + b(total system risk)
Subject to:
Power flow equations
Generation limits
Regional risk constraints
![Page 32: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/32.jpg)
32
Cumulative risk assessment
![Page 33: 1 Security assessment: decision support tools for power system operators James D. McCalley, jdm@iastate.edu Iowa State University, Ames, Iowa September](https://reader036.vdocuments.site/reader036/viewer/2022062308/56649ebc5503460f94bc54e5/html5/thumbnails/33.jpg)
33
Final CommentsThe “secure” and “alert” states
only differ in terms of how insecure they are, and we need a measurable
index to reflect this.
Risk is a computable quantity thatcan be used to integrate security with
economics in formal decision-making algorithms.