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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
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
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:
5 of 13 busses
12 of 22 busses
11. PMU Project Lab
Brings PMU Data Directly to EMS
Initially, Utilize EMS Development/QA System for Testing and Comparisons
OSI PMU Implementation
13. 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
OSI PMU Implementation
15. OSI PMU Implementation Early Lessons Learned (Learning)
IEEE Standards Revisions
Visualization Tool Improvements
16. 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 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. Current and Future SRP PMU Uses
Instantaneous State of the Electric System View
Enhanced State Estimation (Measurement)
Black Start Visibility
Line Impedance Derivation
Island Phase Angle Studies PMU Implementation
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)
20. OSI Application Development OSI is Working to Bring PMU Data into the
EMS Environment to Meet Several Goals,
Ease of Implementation
Development of Enhanced Visualization Tools
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
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)
Solution accuracy for observable islands and boundaries
Bad data detection
Solution accuracy for the unobservable islands
25. Topological Observability
31. Selection of Reference Angles for SE (No PMUs)
33. Selection of Reference Angles for SE With PMUs
34. Selection of Reference Angles for SE With PMUs
35. Heuristic Selection of Reference Angles for SE With PMUs
36. Heuristic Selection of Reference Angles for SE With PMUs
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.