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California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
State Estimator for CA ISO Market -Relevance and Readiness
2008 EMS Users Conference Atlanta, Georgia
Sunday, Sept 7, 2008 - Wednesday, Sept 10, 2008
Soumen Ghosh, Ph.D.
CAISO
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
• Introduction
• CAISO Network Model (EMS Model) footprint;
• The Market Model footprint, Full Network Model (FNM);
• The models in Common Information Model/eXtensible Markup Language (CIM/XML) format;
• The relevant EMS applications;
• Orthogonal State Estimator (SE) and its comparison with Fast Decoupled SE;
• The relevance of SE solution in Real Time Nodal Market and VSA;
• The SE Readiness Metrics adopted at CAISO and the proposed acceptable range of the metrics.
• Conclusion
Overview
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
• Reliability tools and market systems depend on the results produced by the SE
• Monitoring & Analyzing the quality and availability of every SE solution
• At CAISO, the SE solution is used for Real Time Power Flow and Contingency Analysis, Real Time Nodal Market, and for Voltage Stability Analysis.
• In the evaluation of SE readiness,
• Several metrics used by the Midwest ISO (MISO) and Southwest Power Pool (SPP) were reviewed
• Several new SE performance metrics of the SE solution at the CAISO have been identified
• The new SE performance metrics are to identify an unreasonable SE solution even if the solution is valid.
• Our hope is to set up a framework for all stake holders to work collectively in identifying a standard set of SE metrics to determine the quality of the SE solution
Introduction
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
CAISO Network Model footprint
CAISO - EMS CAISO - FNM
Buses 5950 3190
Units 1809 1036
Loads 3150 1974
Lines 5398 3336
Transformers 2327 1082
Shunts 1420 199
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
Network Model
• EMS Network Model: This includes the detailed system (including sub-transmission) for the state of California and for all other WECC areas, the system is represented for voltage levels at 161 KV and above.
• Market Full Network Model: Detailed Network Model, mostly derived from the EMS Network Model,
• The power system model for the CAISO footprint,• Fictitious injections on inter-ties to areas not part of CAISO markets and• Commercial data for the market participants (ex: an association between a set of electrical buses to a specific LMP pricing node)
CIM/XML Model Format: A common model format that can be used and understood by different
platforms provided by a variety of vendors.
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
PSLF Model
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
</cim:ACLineSegment><cim:ACLineSegment rdf:ID="Conductor_2003">
<cim:Naming.name>POEPH-RIOOSO_230_BR_1_1</cim:Naming.name>
<cim:Naming.description>30280_POE _230_30330_RIO OSO _230_BR_1 _1</cim:Naming.description>
<cim:Conductor.x>43.8911</cim:Conductor.x>
<cim:Conductor.r>7.41658</cim:Conductor.r>
<cim:Conductor.bch>16.234</cim:Conductor.bch>
<cim:ACLineSegment.MemberOf_Line rdf:resource="#Line_7448"/>
<cim:ConductingEquipment.BaseVoltage rdf:resource="#230_BV"/>
CIM/XML Model
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
Detailed Model
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
STATE ESTIMATOR•State Estimation processes telemetered system power measurements to obtain an estimate of ‘State’ - the magnitudes and phase angles of bus voltages in the actual power systems.
• This calculation is based on the telemetered analog quantities (MW, MVAr, and KV) and the most current topology of the power system.
• Knowing the state of the power system, it calculates the MW, MVAr, and MVA flows through all the transmission lines and transformers and the MW and MVAr injections for all the loads and generation sources.
• These calculated voltage and power values provide useful operational information in cases when no telemetry is available. When valid telemetry does exist, the calculated quantities can be used to identify measurement errors.
EMS Relevant applications
REAL TIME LOAD FLOW & CONTINGENCY ANALYSIS •Real Time Load Flow provides the system operator with grid information like voltage and line flows for different short-term study conditions.•Real Time Contingency Analysis provides the system operator with the information on the ‘system state’ for different ‘what if’ conditions on the existing system. CAISO OUTAGE MODELING TOOL (COMT) •The COMT application is a Web-based tool which allows the users to search the CAISO Outage database and identify scheduled outages that impact the network topology. The tool allows the users to develop switching instructions (based on Network Model components) that need to be automatically applied to the network model at the appropriate time.
• In the Real-Time COMT is used to update the status of non-telemetered points and the status points with failed telemetry.
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
0
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60
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stage 1 stage 2 stage 3 stage 4
orthogonal
fast decoupled
COMPARISON : INVALID RUNS for ORTHOGONAL vs. FAST DECOUPLED
Stage 1
Run with existing ‘Convergence Tolerance’ Run with existing ‘Global Measurement Errors’
Stage 2 Set MW/ MVAR convergence tolerance for all Areas to 0.05 Revise the MW/ MVAR mismatch on ‘Zero Injection Buses’ measurement error tolerance to 0.1
Stage 3
Re-set convergence tolerance to values before Stage 2Reduce the minimum values for ‘Global Measurement Errors’ For Voltages, use decrements of 0.001 For Circuits, use decrements of 0.5 (then) .05 For gen/loads, use decrements of 0.1 (then) .01
Stage 4Repeat steps of Stage 2 with parameters of Stage 3
Orthogonal vs. Fast Decoupled Comparisons
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
Real Time Market • Real Time Pre Dispatch (RTPD)
• Executes every 15 minutes
• Real Time Interval Dispatch (RTID)• 5 Minutes dispatches
• RTPD & RTID• Utilizes the Full Network Model updated by the real time State Estimator solution to get the current operating conditions to initialize the power flow. State Estimator Solution resides in Enterprise Integration Bus to be used by RTPD and RTID.
State Estimation & Real Time Market
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
•In the RTM environment the static model is updated with dynamic data based upon real time operations that comes from the State Estimator application which is merged with commercial Market and Supplemental Market Data Maintenance (SMDM) system data for the various Market runs.
• The static market model from the GDB and the dynamic model of the power system are exported from the EMS to the RTM system.
• For the RTM analysis, the State Estimator solution along with Topology Information from the EMS is transmitted to the RTM System and used to initialize the Power Flow.
State Estimation & Market
Full Network Model
Dynamic Model from EMS for
RTM only
Outage Derates
Static ModelFrom EMS
Voltage/Tap Schedules
Load, Generation, and Reactive
Distribution Factors
Constraints/Exceptions
Contingencies
Market Analysis Engine(Topology Process, Power Flow, Security Analysis, Unit
Commitment, Unit Dispatch, Congestion Management, Loss Management, Locational Marginal Pricing)
RTM IFM
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
SE/ DLF Solution Quality Monitor
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
SE/ DLF Solution Quality Monitor
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
• Importance of the quality of the information provided by the SE to the various reliability and market tools
• At the California ISO, the SE solutions are required for (1) The Real Time Market and for (2) Security Applications such as Voltage Stability Analysis.
•This presentation proposes the formulation of metrics to study the availability and quality of the SE solution.
Conclusion
California Independent System Operator
Soumen Ghosh CAISO CONFIDENTIAL Created: 06/15/2008
Questions and Answers