Integration of Synchro-Phasor Measurements in Power Systems State Estimation for Enhanced Power System Reliability

1
(No Transcript)
2
Integration of Synchro-Phasor Measurements in
Power Systems State Estimation for Enhanced Power
System Reliability

• Hassan Ghoudjehbaklou, Ph.D. Open Systems
  International, Inc.
• Gary Roskos Open Systems International, Inc.

3
Agenda

• PMUs and the Smart Grid
• PMUs and the State Estimation (SE)
• Effect of PMU in Observability
• Enhancing Solutions for Unobservable Islands
• Certification Tests for SE PMU
• Conclusions How PMUs Can Help?

4
Applications of PMUs (Wikipedia)

• Power system automation, as in smart grids
• Load shedding and other load control techniques
  such as demand response mechanisms to manage a
  power system. (i.e. Directing power where it is
  needed in real-time)
• Increase the reliability of the power grid by
  detecting faults early, allowing for isolation of
  operative system, and the prevention of power
  outages.
• Increase power quality by precise analysis and
  automated correction of sources of system
  degradation.
• Wide Area measurement and control, in very wide
  area super grids, regional transmission networks,
  and local distribution grids.

5
PMUs and the Smart Grid

• Phasor Measurement Units (PMUs) Provide
  Synchronized, Wide-Area Power Measurements
• PMUs provide the Magnitude and Angle of all power
  measurements at all grid locations simultaneously
• Measurements are available as frequentlyas 30
  times each second

6
PMUs and the Smart Grid

• Thoughtful PMU deployment is a key element to
  Smart Grid development at the transmission level,
  accomplishing these Smart Grid goals
• Increased System Reliability
• High Quality, Real-time Data
• Advanced Analysis, Optimization and Controls
• Aggregate transmission operations and planning
• Enhance grid security and stability (reliability)
• Manage losses and congestion
• Enhanced Communications Infrastructure and Data
  Security

, Efficiency
and Security
7
Current Events and Challenges

• PMU Technology is Now Widely Available
• PMU Devices are Readily Available From Multiple
  Vendors
• Open Connectivity/Interoperability via IEEE
  Standards
• GPS and Communications Equipment is Affordable
  and Hardened for Substation Use
• Utility Communications Infrastructure is
  Improving Daily

8
Current Events and Challenges

• Multiple Active Pilot Projects and Research
  Programs are in Place
• Basic Research in Massive-Volume, Real-Time Data
  Processing and Dynamic Applications
• Basic Research in New Approaches to Grid
  Stability
• Strategic Deployment
• Post-event analysis
• Model verification
• Data integrity and visualization

9
Current Events and Challenges

• Implementation Hurdles
• Device Deployment ( )
• Communications Infrastructure Deployment (
  )
• Application Development - Chicken and Egg
  Problem
• Cant Justify Applications without Data
• Cant Justify Data Collection without
  Applications

10
Example of PMU Implementation

• PMU Deployments
• 500kV
• 5 of 13 busses
• 230kV
• 12 of 22 busses

11
PMU Project Lab
SEL 5076 Sychrowave SW
OSI monarch EMS System
12
OSI PMU Implementation

• OpenPMU
• Brings PMU Data Directly to EMS
• Initially, Utilize EMS Development/QA System for
  Testing and Comparisons

13
OSI PMU Implementation

• Data Collection, Visualization and Archiving
• Several tools have been created specifically for
  PMU data collection, visualization and Data
  Archiving
• Most of these tools allow for real-time,
  high-speed measurements viewing and storing
• Traditional EMS tools for viewing real-time data
  are being adapted to provide useful visualization
  of this high-speed data

14
Visualization Tools
15
OSI PMU Implementation

• Early Lessons Learned (Learning)
• IEEE Standards Revisions
• Communications Security/Redundancy/Failover
• Visualization Tool Improvements
• Troubleshooting

16
OSI PMU Implementation

• SRP Research with Arizona State University
• Optimal PMU positioning in electric power system
  based on achieving maximum State Estimation
  improvement (Prof. Heydt, Vittal)
• Synchrophasor technology in validation of T-line
  impedance parameters (Prof. Tylavsky)
• Decision tree assisted online Security Assessment
  using PMU measurements (Prof. Vittal)
• Generator dynamic parameters validation (Prof.
  Heydt)

17
PMU Implementation

• Continuing Efforts
• Expansion Plan Underway
• Continued deployments
• Continued OSI Development
• OpenPMU - EMS Integration
• Pursuing Specialized Visualization Packages
  (RTDMS)
• Evaluating Additional PMU Device Hardware and
  Upgrades
• WECC DMWG WAMS Task Force Involvement
• Becoming foundation for Smart Grid vision
• PMU Network at Transmission level
• AMI at Distribution level

18
PMU Implementation

• Current and Future SRP PMU Uses
• Instantaneous State of the Electric System View
• Enhanced State Estimation (Measurement)
• Operator Visualization
• Black Start Visibility
• Line Impedance Derivation
• Disturbance Post-analysis
• Island Phase Angle Studies

19
PMU Implementation

• PMU Observations
• Will be the Most Important Measuring Device in
  Transmission System Monitoring and Control
• Will Revolutionize Power Systems Monitoring and
  Control
• Gradual Migration Towards Full PMU Implementation
  for the Transmission Grid
• For Full Potential, a PMU System Must Have
  Communication Infrastructure Support Including
  Coverage and Speed to Match Streaming PMU
  Measurements
• WECC Synchronized Phasor Network (DMWG WAMTF)
• NASPInet

20
OSI Application Development

• OSI is Working to Bring PMU Data into the
• EMS Environment to Meet Several Goals,
• Including
• Ease of Implementation
• Solution Accuracy
• Input Data
• System Models
• Solution Speed
• Increased Observability
• Development of Enhanced Visualization Tools
• Situational Awareness
• Development of Enhanced Dynamic Analysis Tools
• Take advantage of a reduced solution cycle

21
OSI Application Development

• Short-term Enhancements
• Enhanced Communications Security
• Enhanced Fail-over Capabilities
• Enhanced Visualization Tools
• Current OSI PMU-Specific Development
• Enhanced Data Access
• Optimized Hybrid State Estimation
• Advanced Data Archive/Historian Capabilities
• Enhanced Dynamic Stability Analysis and Control
• More Real-time and Historical Visualization Tools
• Next-generation Data Security Tools
• -

22
PMU Deployment Strategies

• Limited Deployment
• Measurement and Model Improvement
• Both sides of a variable device (Phase-Shifter,
  LTC, DC Line, etc.)
• Measurement or Visibility Problem Areas
• Interconnections
• Large-Scale Deployments
• Start at Highest Voltages
• Cover 500kV, then 345kV, etc.
• Grow Contiguous PMU Measurement Areas
• Start at one end and work toward the other

23
PMU Deployment Strategies

• Long-Term Goals
• High-Quality, Sub-second State and Model
  Measurement
• System state measured, not estimated
• System parameters measured, not calculated
• Dynamic events detectable
• Add Applications to Capitalize on New Paradigm

24
PMUs and the State Estimation (SE)

• Effects on
• Observability
• Solution accuracy for observable islands and
  boundaries
• Bad data detection
• Solution accuracy for the unobservable islands

25
Topological Observability

• Step 1 Determine the measurement islands. All
  islands with PMUs will have the same group/island
  number
• Step 2 Reduce the effect of bad angle
  measurements (Use Median of the angles)
• Step 3 All Branches within a measurement islands
  will have observable flows

26
Topological Observability
Step 4 Enlarge the observable islands using n-1
rule recursively Step 5 If voltage/angle of
both sides of a branch are measured, add its
calculated flows as pseudo measurement, for added
stability and accuracy Step 6 Change
unobservable islands to observables, if all
injections are measured or at most one injection
is not measured
27
PMU measurements added to model studied by P.
Katsilas, et. al. (2003)
PMU Voltage/Angle Measurements Injection
Measurement Flow Measurement
28
Actual Flows
29
SE FLOWS (NO PMU)
30
SE Flows (W/ PMU)
31
Selection of Reference Angles for SE (No PMUs)
Electric Island 1
Electric Island 2
U2
O2
O1
U2
U3
Main Observable Island
O1
U1
U1
O2
Main Observable Island
O3
U4
32
Selection of Reference Angles for SE (No PMUs)

• Action
• In Flat start, initial angles are set to zero
• Convergence
• Good convergence of SE for Observable islands
• Poor convergence for unobservable islands
• Accuracy of the SE solution
• Good for inner observable island
• Poor for close to boundaries
• Worst for unobservable islands

33
Selection of Reference Angles for SE With PMUs
Electric Island 1
Electric Island 2
U2
O2
O1
U2
U3
Main Observable Island
O1
U1
U1
O2
Main Observable Island
O3
U4
34
Selection of Reference Angles for SE With PMUs

• Action
• In Flat start, initial angles of the observable
  islands are set to the Median angles of all PMUs
  of that island. Initial angles of unobservable
  islands are set to zero.
• Convergence
• Good convergence of SE for Observable islands
• Poor convergence for unobservable islands
• Accuracy of the SE solution
• Good for inner observable island
• Poor for close to boundaries
• Worst for unobservable islands

35
Heuristic Selection of Reference Angles for SE
With PMUs
Electric Island 1
Electric Island 2
U2
O2
O1
U2
U3
Main Observable Island
O1
U1
U1
O2
Main Observable Island
O3
U4
Selection of PMU Based Reference Angle for SE
36
Heuristic Selection of Reference Angles for SE
With PMUs

• Action
• In Flat start, initial angles of the observable
  islands are set to the Median angles of all PMUs
  of that island. Initial angles of unobservable
  islands are set to angle reference of the
  electrical island.
• Convergence
• Good convergence of SE for Observable islands
• Better chance of convergence for unobservable
  islands
• Accuracy of the SE solution
• Good for observable island
• Good for close to boundaries
• Good for unobservable islands (depends on
  schedules)

37
PMU SE Certification Databases

• Following slides present results for series of
  tests for Phasor Measurement Units (PMU)
  implementation in State Estimation (SE). Four
  different databases are considered for this
  study
• IEEE-14 (Power Flow solution as PMU
  Measurements)
• Large Customer no. 1 (With actual PMU
  measurements)
• Larger Customer no. 2 (No PMU Measurements)

38
PMU SE Certification Test 1

• Test 1 Verify Observability and solvability of
  the PMU SE with only Phase angle and Voltage
  Magnitude Measurements at all buses with no other
  measurements. Compare the results with only bus
  injection measurements or only branch flow
  measurements.
• Action Summary All tests completed with
  solution matching within the tolerances
• Conclusion When all measurements are good,
  phase angles and voltage magnitudes provide good
  observability and accurate solution (This fact
  has been reported by other researchers as well.)

39
PMU SE Certification Test 2

• Test2 Introduce some bad angle measurements to
  the cases with all phase angle and voltage
  magnitude measurements. Note the effect on the
  solution quality and convergence.
• Action Summary Initially some tests completed
  and bad angles detected. Later Median angle
  enhancement was employed for the reference angle
  of the measurement islands. That made all cases
  converge, when only few angles were bad.
• Conclusion SE solution is very susceptible to
  bad angle measurements (As reported by other
  researchers) and some heuristics should be
  deployed.

40
PMU SE Certification Test 3

• Test3 Use databases with PMU measurements for
  the existing large customers (if the large
  customer does not have PMU, introduce some PMUs
  in the model and use phase angles from a Power
  Flow solution as measurement.) Verify Convergence
  of PMU SE.
• Action Summary Initially some tests completed
  when phase angles where small. Later with
  enhancement for large angles, all cases
  converged, when all angles where good. Using the
  enhancement of Power Flow for PMU, all cases
  converged and good results were obtained for the
  unobservable as well as observable islands.
• Conclusion Classical SE and PF need to be
  enhanced to handle both large and bad angle
  measurements..

41
PMU SE Certification Test 4

• Test4 Verify that adding phase angle and
  voltage magnitude measurements actually changes
  observable islands.
• Action Summary To observe any change in the
  observable island the PMU measurements need to be
  close to the boundaries in the unobservable
  islands.
• Conclusion Not all PMUs directly impact the
  quality of the solution of the network. Some have
  more effect than the others.

42
Conclusions

• How PMUs can help SE.
• Provides redundant measurement that could enhance
  observability and improve quality of the solution
  for the observable island.
• Provides angle reference for measurement islands
  that enhances stability and accuracy of the
  solution for the unobservable island.

43
Conclusions

• What Enhancements are needed for PMU SE?
• Enhancing Observability algorithm for PMU
  measurements.
• Good selection of PMU phase angles for
  measurements islands.
• Improved heuristics for handling unobservable
  islands.
• What Other improvements are possible for PMU SE?
• Model verification (parameter estimation).
• Real-time State Estimation of a critical
  sub-network.
• Enhanced Visualizations.

44
Questions?