State Estimator for Market and Reliability – Need for EMS Support Tools to fix Topology Errors and for

External model maintenance

(Veera Raju Vinnakota, Sirajul Chowdhury, Brian Cummins, Ankit Mishra, Hani Alarian, California ISO, U.S.A.)

12th International Electric Power Control Centers (EPCC) Workshop - June 2-5, 2013 Bedford Springs, PA, U.S.A

PRESENTATION OVERVIEW • ABSTRACT(Summary) • INTRODUCTION

– CAISO Overview – CAISO EMS Overview

• EMS Architecture • EMS Interfaces, Network Applications

• NEED FOR HIGHER QUALITY OF STATE ESTIMATOR (SE) SOLUTION IN EXTERNAL AREAS

– SE QUALITY MEASURES IN USE AND PLANS – ONGOING SUPPORT FOR SE SOLUTION QUALITY – RELATIVELY LARGER GROSS ERRORS IN EXTERNAL AREAS – NEW QUALITY METRICS IN WORKS AT CAISO FOR IMPROVING EXTERNAL

SOLUTION QUALITY – NEED FOR TOOLS FROM EMS VENDORS TO IMPROVE EXTERNAL AREAS’

SOLUTION QUALITY • CONCLUSIONS • ACKNOWLEDGEMENTS • REFERENCES

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ABSTRACT ( Summary)

• Criticality of State Estimator for CAISO Market and Reliability

• Higher quality of SE solution in CAISO Internal areas has been in place

• On-going Support for higher Quality of SE Solution • Need for improving external areas solution Quality • New Quality Metrics for improving external area Solution • Need for tools to pursue higher quality SE solution in

external areas to support : – Topology adjustments in external areas – Visuals of measurements, estimates, errors, etc.

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CAISO Overview - Independent System Operators and Regional Transmission Organizations

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Control flow of electricity on transmission grid Regulated by FERC Serve 66% of the US & more than 50% of Canada Do not own generation or transmission infrastructure

CAISO Overview – CAISO is part of Western interconnection

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Encompasses western half of North America -- 14 states, British Columbia, Alberta and parts of Mexico

Western Electricity Coordinating Council (WECC) coordinates regional reliability and planning -- governed by 32 board members

California -- ≈ 40% of WECC peak demand

No ISO or California investor-owned utility representatives on WECC board

CAISO Overview – Grid Operations

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• 50,270 MW record peak demand (July 24, 2006)

• 30,000 market transactions per day

• 25,526 circuit-miles of transmission lines

• 80% of California load served by the ISO

• 286 million megawatt-hours of electricity delivered annually

• Governing Board appointed by the governor and confirmed by the Senate

CAISO Overview – Main Office in Folsom, California

EMS Overview - architecture

EMS Overview - Interfaces, Network Applications

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EMS

AGC

ICCP RIG/DPG

PI Systems

Network Apps

Market System

Operator Displays

AGC Set

Points Network Applications Load flow State Estimator Contingency Analysis Outage Scheduler

VSA/ DSA

NEED FOR HIGHER QUALITY OF SE SOLUTION IN EXTERNAL AREAS

• MONTIRING CAISO ELEMENTS IMPACTING EXTERNAL AREAS

• MONITORING EXTERNAL ELEMENTS IMPACTING CASIO

• CONFORM TO WECC RELIABILITY REQUIREMENTS

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SE QUALITY MEASURES IN USE AND PLANS

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• Quality Indices on per Area / PTO basis • Quality Indices related primarily to specific run

o Performance Index active/reactive (Indicates difference between actual and estimate)

o Total Interchange residual (indicates degree of solution quality) o Total MW Generation Mismatch (indicates degree of solution quality) o Total –ve generation (indicates degree of solution quality) o Total MW load mismatch (indicates degree of solution quality) o Critical measurements at each KV level ( Indicates how well measurements are

spread)

• Quality Measures for long term improvement (Plans) o Availability of Measurements at each KV level (indicates amount of telemetry at

each KV level) o Measurements spread index based on local redundancy and regional redundancy

and total redundancy ( to be developed – indicates extent of spread of telemetry) o New Quality Metrics for Improving External Area Solution

ONGOING SUPPORT FOR SE SOLUTION QUALITY

1-16 weeks of Time frames - Periodic update of EMS network model - Periodic update of EMS measurements model consistent with Power network, Protection & Control, Data acquisition and Communication Network changes in the field

On Daily basis and Real time - Real time monitoring of convergence of SE every cycle (typical range of 30” – 15’) - Trouble shoot and provide fixes in case of SE non-convergence in real time - Tune measurements, parameters for a better solution - Analysis of non-converged cases of State Estimator - ‘On-call’ support (24 hours x 7 Days a week) by a set-up of Help desk system

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LARGER SE GROSS MEASUREMENT ERROR IN EXTERNAL AREAS

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- For same number of Gross MW errors, error is large in external area ( Eg: CISO Int-2 Vs Ext-4)

NEW QUALITY METRICS AT CAISO • Primarily for tracking and improving external area solution • Metric to guide on priority Area and monitor Quality level • NEW METRICS

– *RBH-Load ( In trial use : encouraging results) – *RBH-Generation (In trial use : encouraging results) – *RBH-Interchange ( in works) – *RBH-Total ( in works)

RBH-Load = Abs(Meas Load – Est Load) /Meas Load in MW RBH-Generation = Abs(Meas Gen – Estimated Gen) /Meas Gen in MW RBH-Interchange = Abs(Meas Interch - Est Interch) /Meas Interch in MW RBH-Total = Abs(Meas load – Est load) + Abs(Meas Gen – Est Gen) + Abs(Meas interch – Est interch) /(Meas Gen + Meas Load + Meas Interch) in MW

• Measured Load, Generation and Interchange are consolidated from AGC Application into areas as a reference for Estimated values

*RBH (Raju-Brian-Hani Percentage Error)

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WESTERN INTERCONNECTON BALANCING AUTHORITIES ( Source WECC Web site)

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NEW QUALITY METRICS IN WORKS AT CAISO

• Values computed every SE run, tracked on PI • Metric value helps choose target quality level and track if improvements work • Need for tools with improved Visuals to enhance external area solution quality

– To help topology adjustments in external areas matching real time conditions – To provide better Visuals on measurements, estimates, errors, etc.

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5/19/2013 13:00

AREA Name RBH - Load RBH-Generation RBH-Total CAISO 1.97 3.73 2.68 CAISO Area 1 3.12 3.8 3.43 CAISO Area 2 1 5.01 2.2 CAISO Area 3 0.83 0.9 0.87 CAISO Area 4 1.05 1.05 External Area – 1 0.23 0.4 0.31 External Area - 2 34.47 1.85 12.39 External Area - 3 9.85 15.35 12.57 External Area - 4 14.51 15.54 15.02 External Area - 5 2.41 9.52 5.94 External Area - 6 3.79 83.86 34.67 External Area - 7 0.55 3.16 1.64 External Area - 8 15.51 8.35 10.91 External Area - 9 8.13 14.67 11.36 External Area - 10 33.74 2.39 18.49 External Area - 11 20.69 2.66 12.37 External Area - 12 11.01 0.91 6.32 External Area - 13 10.55 10.54 10.54 External Area - 14 0.24 35.66 11.35

CONCLUSIONS

• State Estimator is Critical for CAISO Market and Reliability • Higher quality of SE solution in CAISO internal areas has

been in place • On-going Support for higher Quality of Solution • External Area Solution needs better Quality • New Metrics in works for improving external area solution • New metric to guide Area of priority and Level of Quality • Need for tools for improving external area solution quality

– To help topology adjustments in external areas – To provide better Visuals of measurements, estimates, errors, etc.

preferably in Geographic/topological maps Page 17

ACKNOWLEDGEMENTS

• To CAISO for support and encouragement to present some of the works carried out at CAISO

• To Timothy Willenberg, Charlie Mogannam, James Bonham, Linda Monge Guerrero and David Lee for working hard to support high quality SE Solution

• To Wei Shao, Licheng Jin for Quality related improvements and for Supporting Network Applications in the past

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REFERENCES

• Dinesh Salem-Natarajan, Wei Shao, Mani Subramanian, Hsiao-Dong Chian, et.al., “State Estimator for CAISO Market and Security Applications – Relevance and Readiness”, presented at IEEE PES General Meeting 2008, Pittsburgh, Pennsylvania, U.S.A. July 20-24, 2008.

THANK YOU Contact : VVINNAKOTA@CAISO.COM

(Veera Raju VINNAKOTA)

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