Excitation Systems Models 2019 - WECC · Excitation Systems Many location options for different...

Excitation Systems

Models

2019

November 21, 2019

Shawn Patterson

Bureau of Reclamation

PPMVDTF

▪ AVRs raise/lower excitation as far as necessary to control terminal voltage

▪ Excitation changes can force operation of a machine beyond its capability

▪ Excitation Systems incorporate automatic limiters to prevent operation beyond what is desired, e.g.,

• Overexcitation Limiter

• Underexcitation Limiter

• V/Hz Limiters

• Voltage limiters

• Stator Current Limiters

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Review

▪ WECC database excitation system models currently do not incorporate excitation limiters

▪ There is little in the collection of plant models in the database to prevent a generator from behaving unrealistically during simulations

▪ Simulation results in these cases are wrong. Always on the optimistic side.

▪ Solution: Get the excitation limiters modeled

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Models for Studies

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Generator Capability

Nothing to prevent modelsfrom operating here

Or here

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Voltage Dependency

Limiters and limiter modelswill properly accountfor voltage dependency(Think MOD-025)

▪ Excitation models in use do not include the

control points needed to interact with limiters

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Problem

▪ IEEE working group issued standard 421.5,

which defines some standard limiter models

▪ All existing excitation system model

structures were redefined to include the

necessary limiter control points

▪ Some new excitation models were also

included

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Solution, Part 1

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Limiters – OEL2

To excitation system model

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Limiters – UEL2

To excitation system model

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Excitation Systems

Many location options for different limiter signal inputs

▪ Add limiter models to the software libraries

▪ Add or modify excitation system models to

software libraries to work with the limiters

▪ Solution, part 3:

• Use the models. Duh!

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Solution, Part 2

▪ Limiter models to be added

• 2 UELs, 4 OELs, 2 SCLs

▪ Lots of models in the libraries need to be added/modified to work with the limiters

• 17 standard models used in WECC cases

• 6 new standard models not yet used in WECC

▪ This is a significant task, so prioritizing based on popularity in a recent WECC case:

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Solution Problem

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Popularity

▪ OEL2, UEL2, UEL1, OEL4, OEL5, OEL3

▪ ST1, ST4, AC8, AC7, DC1

• 84% of total

▪ AC1, DC4, ST6

• 10% of total

▪ DC2, ST2, AC2, AC5, AC6, ST5, ST3, AC4, ST7, AC3

• 6% of total

▪ AC9, AC10, AC11, ST8, ST9, ST10

• New Models

▪ PF1, PF2, VAR1, VAR2

• Controllers

▪ SCL1, SCL2

• Limiters

▪ New Stabilizers

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Suggested Implementation Priority of 421.5

Models

▪ Updated models will have the same list of

parameters and will work the same way

▪ Only the limiter connections are new

▪ The existing models can be replaced in the

software and database

▪ Add new versions or replace old versions?

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Old vs. New

Contact:

Shawn Patterson , Bureau of

Reclamation

spatterson@usbr.gov

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