Jay Dondeti, Pavan Addepalle, Chunling Yang, Blake BuescherMISO

Panel Session:External model and internal model inaccuracies impacting State Estimator Solution Quality for Reliability and Market Operations

2014 IEEE PES General Meeting31st July 2014

MISO Experiences of Network Model Maintenance - State Estimator and Contingency

Analysis Accuracy

1

Overview

• Model Building and Maintenance– Modeling Process– MISO Network Model statistics– Network Model Expansion Drivers– Network Model Maintenance– Future Equipment Process– Contingency Model Maintenance– Real-Time Data - ICCP

• State Estimator (SE) and Contingency Analysis (CA)– Measurements Observability & Visibility – SE & CA Execution– SE & CA Monitoring– Score Card Metrics– Real-Time Operations Feedback

2

• Models are updated every quarter. • Testing process is initiated 6 weeks in advance to verify and tune

V0 Testing

• EMS V0 Testing• Operations V0

Review

V1 Testing

• EMS V1 Testing• Operations V1

Review

V2 Testing

• EMS V2 Testing• Operations V2

Review

Modeling Team

Modeling Process3

Model Building

• MISO requests models/model updates from all the internal control areas and adjacent reliability areas on a quarterly basis.

• Model inputs in various formats (Web based tool, CIM, proprietary EMS vendor database format etc.,)

• Incremental changes are made to the models. All known potential equipment changes for next three months are included

• Double modeling of equipment and future equipment process are used to manage changes in the equipment within the quarter

• All tier-one areas are modeled for wide area representation in Market and Reliability analysis

• Extensive inclusion of Eastern Interconnect into the model enabled us to push solution errors far away from the internal areas

4

Model Validation• Various automated tools are used to catch modeling errors• Models go through 3 iterations of review before production

implementation• Models go through a month long testing by Real-Time and Forward

Operations personnel and feedback is incorporated into next version of the model prior to production implementation

• Models are posted on the MISO Extranet for review by the members. Inputs from the review are incorporated into next version of model update.

• Transmission members have access to MISO State Estimator solutions through Citrix access. This provides mutual benefit to tackle model/solution issues

5

Model Testing & Issue Resolution• EMS Model testing aspects

Application parameters are compared between the new and old models Limits, monitoring elements, accuracy classes, impedances, etc. are compared

and validated between the new and old models SE solution is tuned and maintained to meet production performance All application results are reviewed and validated

• Real-Time Operations testing aspects All the model changes are validated by Operations Engineers coordinating

with RCs and TOs Future Equipment and any special configurations, such as double-modeling

are checked by Operations Engineers All the One-Line displays for new and modified substations are checked by

Operations Engineers• Model issue resolution

Model issues are tracked similar to software bug reports on a continuous basis Issues are resolved working closely with the modeling team Updates to the models are tested continuously and during the model testing

process

6

MISO Network Model statisticsJune 2014

Market Reliability External TotalCB/Switches 82291 92325 130996 223321Bus 16226 17553 26899 44452Capacitor/Reactors 2412 2686 5066 7752Load 12786 13838 22431 36269Stations 11254 11972 16603 28575Units 1594 1832 4437 6269Transformers 4070 4588 10096 14684Lines 14862 16008 25239 41247ZBR 885 929 349 1278Mapped ICCP Data 150171 161431 128060 289491

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Network Model Expansion Drivers

• New membership and participation in the MISO Markets by various participants is a driver to revisit and expand modeling depth and details of an area

• Expanded monitoring requirement (lower KV inclusion)• Solution differences between MISO and stakeholders is

another driver for the model expansion• Changes in NERC Bulk electric definition and compliance

requirements are some other drivers• NERC Standards require Reliability Coordinators to have a

wide area view to ensure reliability of bulk electric system

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Network Model Maintenance• Web based tool is extensively used to collect ratings and

impedance changes from members. These changes are rolled into production as necessary between quarterly models.

• A SharePoint site is used by internal stakeholders to list and track model related issues.

• Web based collaborative tool is used to define, validate and upkeep contingency definitions against new model and operating conditions.

• MOD (Model On Demand) data keeps track of upcoming or planned construction projects.

• Internal daily and weekly meetings to share, gather and track issues and ongoing changes in the field.

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Future Equipment Process

• MISO uses double modeling technique to accommodate changes happening asynchronous to model update time

• Information is laid out for internal stakeholders on how and when to switch in/out equipment from the model. Model is initialized to be in tune with the topology at cut-over time

• Outage Coordination and Real-Time Operations Engineering teams track and coordinate these changes to be in sync with the construction activity

• Monthly calls are hosted with External Reliability Coordinators to share and keep track of the future equipment changes

10

Contingency Model Maintenance• Contingency definitions that are affected by quarterly

model updates are reviewed and modified before the new model load

• All contingency definitions are maintained by Operations Engineers

• All contingency changes are checked and implemented into CA by EMS Engineers

• Temporary pre-positioning contingencies may be built to support planned outages

• Review of a definition may be performed to verify validity of N-1 constraints in real-time

• Over 12,000 contingencies are activated in RTCA

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Real-Time Data - ICCP

• Close to 300K points acquired from members and external entities

• ICCP data is acquired either through direct WAN connections or through NERC Net

• When new members are integrated, MISO conducts open loop testing for all the points and closed loop testing on Market units before getting certified as an RC/BA for that member

• Data is scanned at two second scan rate• All status data is acquired as report by exception

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Measurement Observability

Jun 2014(69KV and

Above)Redundancy

RatioMeasurement Observability

MARKET 1.444 79.4

RELIABILITY 1.435 79.4

First Tier 1.17 68.0

Jun 2014 (100KV and

Above)

Redundancy Ratio

Measurement Observability

(Percent)

MARKET 2.335 93.5

RELIABILITY 2.30 93.0

First Tier 1.44 72.0

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SE & CA Execution

• State Estimator runs on every minute schedule

• MISO implemented two CAs in Real-Time

• Quick CA runs in Sequence with Stator Estimator every minute. It only processes contingencies associated with Constraints and calculates shift factors for Market applications

• Full CA runs every four minutes on its own timer. It processes all active contingencies for reliability operations. Currently working to improve Full CA execution time to one minute.

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Real Time Network Sequence

Marke

t Inter

face

Real

Time N

etwork

Se

quen

ceUs

er Int

erfac

eCo

ntrol

Room

Op

erator

s

Operator Adding

constraints

EngineerMonitor &

debug

Operator Constraint Selection

OperatorMonitor

violations

State Estimator Losses

Quick CA(RTCA.EMS)

Full CA(RTCA.EMS2)

Valid SE

SE Out File Constraints File

EMSOUT

Quick CA Displays

UDS UDS

Full CA Displays

RT Displays

CLOGGER

SE & CA Execution Sequence15

SE & CA Monitoring• State Estimator solution is monitored and maintained by EMS Engineers working

on 24x7 shift to ensure solution availability and accuracy are within the criteria• Displays, alarms, pagers, and e-mail notifications are used to communicate

solution status issues. Logs are maintained for all the changes• Tools are built in EMS to monitor solution performance over time and provide

more detailed problem diagnostics

16

SE & CA Monitoring• Overall solution quality is rolled into a single performance index with capability to zoom in by

control area and by type of problem • Performance index is a weighted average of line residuals, bus mismatches, MW Anomalies,

and area load errors

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Score Card Metrics• Three components rolled into EMS Score as part of RT Ops daily performance

report:– SE (5 min) & RTCA (10 min) Solution Availability and RTCA Unsolved Contingency (<5) Index (SAI)

– SE Solution Performance Quality Index (Internal PI < 36, External PI < 60) (SPI)

– Line Residual Index (> 40 MW) (LRI)

• Continuous revisions to metrics to deliver the best solutions possible

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Real-Time Operations Feedback• Real-Time Operations relies on SE and CA solutions for situational

awareness and decision making• RCs are in regular contact with TOs and neighboring entities• Discrepancies between MISO model and coordinating entity are

investigated between RC, ROE, and Real-Time EMS and EMS Model Engineers

• RCs are alerted to new N-1 constraints at a lower threshold (normally 85-90%) for early warning

• Monitored element limits and contingencies are verified with TOs for all N-1 constraints before mitigation actions are taken

• Contingency definition corrections are made by on-shift ROE and implemented into RTCA by on-shift EMS Engineer, if necessary

• Dedicated RC and ROE positions for each MISO Region: North, Central, and South

• RCs and ROEs monitor the footprint 24x7

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Discussion20