Reactive Power Coordination Workshop

Stephen Solis

System Operations Improvement Manager

ERCOT Public

September 6, 2019

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Antitrust Admonition

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Introductions

• Around the Room

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Reactive Power Coordination Workshop• Reactive Power Coordination (RPC Overview)

• Break

• NPRR 966

• Break

• Wrap Up/Discussion/Q&A

Presenter

Stephen Solis

System Operations Improvement Manager

ERCOT Public

September 6, 2019

PUBLIC

Reactive Coordination

• Conducted by ERCOT and ERCOT

Transmission Operators

• Several new ERCOT Transmission

Operators established in past few years

• Renewable generation capacity has grown

and continues to grow

• NERC Requirements continue to change

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Problem Statement

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The integration of renewable generation within the ERCOT

interconnection has introduced several new Transmission

Operators and fundamentally altered the generation

dispatch pattern in the region.

A new tool is needed to address multiple interrelated

objectives of coordination of voltage and reactive control

between TOs, maintaining reliability by preventing and or

correcting System Operating Limit (SOL) exceedances,

minimizing cost of maintenance resulting from increased

switching, and maintaining or improving transfer capability

both in real time and in operations planning timeframe.

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Increasing complexity of voltage control

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# of SVCs and Shunts continue to rise in ERCOT

# of new generation technologies increasing (solar,

wind, battery)

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Voltage Assessments and Monitoring

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• ERCOT and the TOs share responsibilities related to the TOP function. o Real Time

• ERCOT is responsible for monitoring (real-time monitoring) and

assessing (Real-Time Assessment) voltage both pre-contingency and

post-contingency voltages for voltage limit exceedances (i.e. voltage

violations) for the entire ERCOT system. ERCOT assesses the system

every 5 minutes.

• TOs are responsible for monitoring voltage pre-contingency in real time

for their respective area.

• ERCOT and TOs jointly responsible for VAR-001 R3

o Same-day Operations, Operations Planning• ERCOT is currently, solely responsible for VAR-001 R2 (scheduling

sufficient reactive resources for pre and post contingency voltage control)

• ERCOT is currently, solely responsible for the Operational Planning

Analysis (OPA) assessing voltage both pre-contingency and post-

contingency voltages for voltage limit exceedances.

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Relevant NERC Standards

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• IRO-008 R1-R6 (RC)

• TOP-001 R13-R15 (TOP)

• VAR-001 R1-R3 (TOP)

• Definition of Operational Planning Analysis (OPA)

• Definition of Real- Time Assessment (RTA)

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Operational Event

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• Prior to the event on March 20th, TOs had several transmission lines out for

construction or maintenance in the Del Rio, San Angelo, and Mesa View

area. These outages, combined with the forced extension of the Maverick

– Escondido 138 kV line outage, resulted in load in the South McCamey to

Sonora and South Hamilton Road being served by two 138 kV lines: North

McCamey – Santa Rita and San Angelo Power – Santiago – Live Oak. As

wind generation ramped down to zero in the area, the San Angelo Power –

Santiago – Live Oak 138 kV line loading increased to 100% of its

continuous rating. When the San Angelo Power – Santiago – Live Oak 138

kV line tripped, all of the load serving the area moved to the North

McCamey – Santa Rita 138 kV causing a local voltage collapse.

• The Maverick – Eagle Hydro – Escondido 138 kV line outage was first

extended on 3/19 at 15:13 to return on 3/20 at 16:00 which is after the

Next Day Study assessment. This means that the Next Day Study

assessment conducted on 3/19 expected the Maverick – Eagle Hydro –

Escondido 138 kV line to be in service during the study time frame.

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Real Time - Voltage Violations Trends

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• Significant improvements have been made for real time operations over last 5 years

• 2014 – Voltage Limits ERCOT/TO synchronizing

• 2015-2016 – 66kV system/chronic voltage violators

• 2016-2017 – State Estimator cleanup/TO operational changes

• 2018-2019 – NPRR 776 implementation and TRE audits

• ERCOT assesses both pre and post contingency every 5 minutes (includes 69kV)

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Real Time - Voltage Violations Trends

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2019 is trending less than 2017

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Voltage Violations January 2019 and April 2019

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type of exceedances# of exceedances in a month (1/1/19

to 1/31/19)

# of exceedances

> 30 min% > 30 min

post-voltage-high 1,029 49 4.76%

post-voltage-low 6,535 172 2.63%

Pre-voltage-high 8,415 246 2.92%

Pre-voltage-low 429 6 1.40%

total 28194 797 2.83%

type of exceedances# of exceedances in a month (4/1/19

to 4/30/19)

# of exceedances

> 30 min% > 30 min

post-voltage-high 1,013 47 4.64%

post-voltage-low 4,734 132 2.79%

Pre-voltage-high 4,877 167 3.42%

Pre-voltage-low 282 7 2.48%

total 23,607 780 3.30%

• This data is meant to convey the breakdown of different types of voltage violations

• Every 5 minute interval exceeded counts as 1 and this data does not include 69kV

• One contingency can cause multiple exceedances (both local impact and multiple

nodes)

• One local area can have multiple pre-contingency and post contingency exceedances

• Could include some invalid exceedances if caused by bad telemetry, etc.

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Reactive Power Coordination “Tool”

• ERCOT is actively working on a project to develop a multi

hour look ahead tool to improve reactive power coordination

within the ERCOT region.

• This tool is being called the Reactive Power Coordination

(RPC) tool.

• The RPC tool will optimize reactive power controls (shunt

devices, Generator Voltage Set Points, Static Var

Compensators (SVCs), etc.) across a multi-hour interval to

resolve reactive power and voltage-related constraints

(voltage limits, temporal constraints, reactive reserves, etc.)

under both normal and contingency conditions.

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Reactive Power Coordination “Tool”

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Power FlowContingency

AnalysisMW SCOPF

Model

COP

Outages

Constraints

Limits

Contingencies

RPC

Remaining Violations

Reactive Dispatch to

TOs

Commit Additional Generation

Create Manual Operating Plans

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Reactive Power Coordination “Tool” benefits

• Allows for more realistic and reliable future look ahead

studies

• Fewer real time voltage limit exceedances

• Help to ensure that sufficient reactive reserves are

maintained

• Fewer real time Constraint Management Plans (CMPs) and

more identified in advance of real time.

• Improved reactive flows and transfer capabilities (e.g. lower

MVAR flows in some areas, fewer areas with circulating

MVAR flows, increased voltage stability limits, etc.)

• Enhanced coordination between TOs

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Reactive Power Coordination “Tool” benefits

• To perform more realistic and reliable future look ahead

studies, ERCOT needs to have reliable information on how

the reactive controls on the system will be utilized.

– Looking at multiple hours in advance allows better evaluation for

outage conflicts and reactive deficiencies within the operating days

– Hourly 4 hour ahead look ahead study is still challenged in knowing

what manual switching actions beyond those which are automatic

(determined via AVR schedules (set point and deviation band)).

– Manual reactive control movements vary from each operator/engineer

and may not reflect how a TO would operate the manual controls

• Engineers performing look ahead studies will have an

automatic and consistent reactive dispatch that is more

realistic to real–time operations.

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Operator Awareness

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• Transmission Operators will still have to deal with

remaining real time issues as forced outages and system

issues will still surface in real time, however there will be

fewer voltage violations that need to be addressed in

Real-Time.

• Regular training should be administered to maintain skills

in addressing voltage issues for when the tool is

unavailable or potentially not factoring in risks like severe

weather.

• Operators will have improved awareness of potential

reactive deficiencies in the current and next day time

frames.

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Reduced Switching Actions

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• One vendor demonstrated that over a 24 hour period,

without temporal constraints yet, they were able to

reduce the total tap movements from 166 to 75 and shunt

switching from 279 to 206.

• Optimizing the reactive controls will reduce the overall

number of switching actions

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Increased Transfer Capability

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• Optimizing reactive controls can help increase transfer capability in

areas with voltage stability concerns. Ex. Below

• 60-80 MW improvement for worst line outage (gray)

• 250-350 MW improvement for unit 1 (blue) and unit 2 (orange) outage

outage

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Reactive Power Coordination “Tool”

• The RPC tool will have 3 “modes”.

– Daily study that optimizes the same window as Daily Reliability Unit

Commitment (RUC).

– Hourly study that optimizes across the next 12 hours.

– Offline study mode capable of optimizing up to 48 hours.

• The Daily study reactive dispatch will be more informational

in nature to identify needs for additional coordination or

correction.

• The Hourly study will be more accurate and give a 12 hour

rolling window of expected reactive controls dispatch.

• The Offline study mode will allow scenario testing as

necessary (e.g. severe weather) and potentially serve as a

backup study mode if the normal study mode is unavailable.

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RPC Tool Inputs

• Hourly power flow cases

– Load Forecast

– Wind/Solar Forecast

– RUC/COP data

– Outages

– DC Tie schedules

• Constraints

– Physical

– Temporal

• Contingency definitions

• Remedial Action Scheme definitions

• Historical information

– Previous hours switching information for temporal constraints

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RPC Tool Constraints

• System voltage limits

– Normal (Pre-contingency)

– Emergency (Post-contingency)

• Dynamic reactive reserves

• Voltage stability limits

• Physical constraints (e.g. reactive capability curves for

generation resources, reactive capability of SVC, AVR status

etc.)

• Temporal constraints (e.g. startup time, minimum run time,

max # of operations within 24 hours, etc.)

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RPC Tool Controls

• Static reactive resources

– Shunts

• Reactors

• Capacitors

– Transformer control taps

• Dynamic reactive resources

– SVCs

– STATCOMs

– Synchronous Condensers

– Generating Units

• Unit Commitment, Line Switching, Distribution side reactive

power, Load Shed plans will be handled as needed if RPC

tool cannot solve a constraint.

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RPC Output Mock-up Screenshot

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Run TimeTransmission

OperatorDevice Type STATION

Device

NameKV

Total # of

Control

Actions

HE 01 HE 02 HE 03 HE 04 HE 05 HE 06 HE 07 HE 08 HE 09 HE 10 HE 11 HE 12

1/1/2018 0:02 ERCOT REACTOR MET R1 69 2 ON ON ON OFF OFF OFF OFF OFF OFF ON ON ON

1/1/2018 0:02 ERCOT CAPACITOR MET C1 69 4 OFF ON ON ON OFF ON ON ON OFF OFF OFF OFF

1/1/2018 0:02 ERCOT CAPACITOR MET C2 69 0 OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF

1/1/2018 0:02 ERCOT CAPACITOR MET C3 69 0 OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT

1/1/2018 0:02 ERCOT SVC MET SVC1 138 2 141 141 141 141 141 141 142 141 141 141 141 141

1/1/2018 0:02 ERCOT GENERATOR AUSTIN UNIT 1 138 4 142 141 141 142 142 142 143 143 143 142 142 142

1/1/2018 0:02 ONCOR REACTOR HILLSIDE RX1 138 0 OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF

1/1/2018 0:02 ONCOR REACTOR SIDEHILL RX2 138 1 ON ON OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF

1/1/2018 0:02 ONCOR CAPACITOR SIDEHILL CX1 345 1 ON ON ON ON ON ON ON ON OFF OFF OFF OFF

1/1/2018 0:02 ONCOR CAPACITOR SIDEHILL CX2 345 2 OFF OFF OFF OFF ON ON ON OFF OFF OFF OFF OFF

1/1/2018 0:02 ONCOR LTC LEFTDRIVE LTC1 69 0 5 5 5 5 5 5 5 5 5 5 5 5

1/1/2018 0:02 ONCOR LTC LEFTDRIVE LTC2 69 3 5 5 5 5 5 6 7 7 5 5 5 5

1/1/2018 0:02 CENTERPOINT GENERATOR BEACHSAND U1 69 2 70 70 70 70 72 72 72 72 72 70 70 70

1/1/2018 0:02 CENTERPOINT GENERATOR BEACHSAND U2 69 2 70 70 70 70 72 72 72 72 72 70 70 70

1/1/2018 0:02 CENTERPOINT GENERATOR BEACHSAND U3 69 0 OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT

1/1/2018 0:02 CENTERPOINT CAPACITOR NASA CAP1 69 2 OFF OFF OFF OFF OFF ON ON ON ON OFF OFF OFF

1/1/2018 0:02 CENTERPOINT CAPACITOR NASA CAP2 69 2 OFF OFF OFF OFF OFF OFF OFF ON ON OFF OFF OFF

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RPC Grid Geo

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There is currently plans in the project to also make the reactive dispatch

available in Grid Geo

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Coordination between ERCOT and TOs

• Project Implementation

– Coordinate on necessary constraints for the RPC tool (e.g. temporal

constraints)

– Coordinate on necessary “cost”/weighting factors for control selection

in the RPC Tool (i.e. prioritizing which reactive devices should be

utilized in what sequence)

– Coordinate on the RPC tool reactive dispatch output file design

• Rule Changes

– Coordinate and implement NPRR 966

– Gray boxed until project goes live

• Testing

– Manual review of RPC tool reactive dispatch for issues

– Pilots and tests of implementing actual RPC tool reactive dispatch

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Q&A

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Reactive Power Coordination Workshop• Reactive Power Coordination (RPC Overview)

• Break

• NPRR 966

• Break

• Wrap Up/Discussion/Q&A

Presenter

Stephen Solis

System Operations Improvement Manager

ERCOT Public

September 6, 2019

We will return at 11:00 AM.

Reactive Power Coordination Workshop• Reactive Power Coordination (RPC Overview)

• Break

• NPRR 966

• Break

• Wrap Up/Discussion/Q&A

Presenter

Stephen Solis

System Operations Improvement Manager

ERCOT Public

September 6, 2019

PUBLIC

NPRR 966 – Outage Coordination

• Sections 3.1.4.3 and 3.1.4.4 clarifies expectations for

entering Outages for reactors, capacitors, reactive controlled

sources for Resource Entities and TSPs so that the Reactive

Power Coordination tool can have accurate awareness of

the availability of the reactors, capacitors, and reactive

controlled sources;

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NPRR 966 – Modeling

• Sections 3.10.7.1.4 and Section 3.10.7.1.5 specify the need

to add temporal constraints to the Network Operations Model

for transformers and reactive devices so that the Reactive

Power Coordination tool can have accurate awareness of

any temporal constraints of the reactors, capacitors, or other

reactive controlled sources (e.g. how many times a capacitor

can be switched in or out in a 12 hour period); and

• This will be similar to the information received as part of a

survey in 2017.

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NPRR 966 – Voltage Support Service

• Paragraph (7) added to Section 6.5.7.7 for ERCOT to provide the hourly optimized

reactive power dispatch via a TSP-specific Messaging System and also to post the

schedule on the MIS Secure Area accessible by the TSPs.

• This Messaging System will operate very similarly to the one utilized with Qualified

Scheduling Entities (QSEs) but will be for TSPs. This will require the TSPs to

implement an application programming interface (API) on the TSP side to interface

with the Messaging System.

• The TSPs will be responsible for providing this Dispatch schedule to their operators.

• The TSPs will also be required to send an acknowledgement of receipt each hour.

• The TSPs would be required to implement and or instruct others to implement the

Dispatch schedule unless they determine they should not due to reliability reasons

(e.g. a Forced Outage occurs that modifies the necessary reactive Dispatch or the

inability to implement the Dispatch, severe weather, etc.).

• ERCOT will be required to notify the TSPs when the Reactive Power Coordination

tool is unavailable and then when it is available again.

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NPRR 966 – Messaging System

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ERCOT Messaging System API

Transmission Operator Messaging System

APIEMS

ERCOT RPC Tool

ERCOT Operator

TO Operator

Suggested Reactive Dispatch

Messaging System

Dispatch ReceivedAcknowledgement

Provide Dispatch To Operator

Operator Receipt

Acknowledgement

Messaging System

Dispatchxml

Approved dispatch

ReceiptAcknowledgement

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Time Frame

• ERCOT would like to have NPRR 966 make the

December 2019 Board meeting to support

finalization of planning activities in 2019.

• Preliminary scheduling estimates would make

production capability sometime mid-2021. This

schedule will be finalized by end of 2019.

• ERCOT expects to test or pilot results for 3 to 6

months to tune, stabilize and build confidence in

the reactive dispatch prior to un gray boxing

NPRR 966 language.

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Reactive Power Coordination Workshop• Reactive Power Coordination (RPC Overview)

• Break

• NPRR 966

• Break

• Wrap Up/Discussion/Q&A

Presenter

Stephen Solis

System Operations Improvement Manager

ERCOT Public

September 6, 2019

We will return at 11:45 AM.

Reactive Power Coordination Workshop• Reactive Power Coordination (RPC Overview)

• Break

• NPRR 966

• Break

• Wrap Up/Discussion/Q&A

Presenter

Stephen Solis

System Operations Improvement Manager

ERCOT Public

September 6, 2019

PUBLIC

Q&A

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