Western Electricity Coordinating Council
Modeling and Validation Work Group
Progress Report to TSS
May 2015
The WECC Modeling and Validation Work Group (M&VWG) meeting, Renewable Energy
Modeling Task Force (REMTF), and Load Modeling Task Force (LMTF) meetings were
held in Salt Lake City, UT on March 17-19, 2015. REMTF was held the afternoon of Mar
17 and the morning of Mar 18, LMTF was held the morning of Mar 18, and M&VWG was
held the afternoon of Mar 18 and all day of Mar 19.
The following topics were discussed at the M&VWG meeting:
I. Next Meetings and Workshops
II. Load Modeling
III. Renewable Energy Modeling
IV. System Model Validation
V. Generator Modeling, Testing, and Model Validation
VI. HVDC Modeling
VII. RAS and Relay Modeling
VIII. NERC Updates
IX. WECC Project Updates
X. SRWG Updates
XI. Approved Dynamic Model Library and Status Update of Models
XII. Program Updates
XIII. Others
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I. NEXT MEETINGS AND WORKSHOPS
The next MVWG meeting is planned to be at Salt Lake, UT on June 16-18, 2015. The
REMTF will be held the afternoon of June 16 and the morning of June 17, the LMTF will
be held the morning of June 17, and M&VWG will be held the afternoon of June 17 and
18 all day.
A renewable model and model validation workshop will be held in conjunction with the
REMTF meeting in June. A WSM workshop was also discussed with the date yet to be
determined.
II. LOAD MODELING
A) Composite Load Model – Model Specifications
Bill Price went over the CMPLDW Model Specifications Document. The WECC Dynamic
Composite Load Model (CMPLDW) Specifications Document, dated January 27, 2015,
was unanimously approved.
B) Integrating DGs in Composite Load Model – Model Specifications
It was agreed by REMTF and LMTF to have the DGs in the Composite Load Model. Bill
Price (GE) presented the WECC Specifications for Modeling Distributed Generation in
Power Flow and Dynamics. The WECC Specifications for Modeling Distributed
Generation in Power Flow and Dynamics, dated February 27, 2015, was unanimously
approved. The Composite Load Model with DG is named as CMPLDWG. CMPLDW will be
retired upon implementation and approval of CMPLDWG.
Song Wang (PacificCorp) will coordinate the benchmark testing among the three
vendors for CMPLDWG. The target is to present the results in the Nov 2015 meeting.
C) Composite Load Model – Future Development
There are 130+ parameters in the Composite Load Model to manage. Software vendors
are moving towards the modular structure for better data management.
Bill Price showed a new version of CMPLDW with simplified data input, which was
implemented in PSLF version 19, called CMPLDWX. It uses several “data management”
models to input the data for the sub-models, which can be recognized by the “_” as the
first character of the model name.
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James Weber (PowerWorld) also showed how to model load models with better data
management by creating load model groups and distribution equivalent types. With
better data management, there are 45 times fewer records to maintain.
In addition to the data management, Pouyan Pourbeik (EPRI) questioned about the load
model data assumptions, for example, modifying feeder impedance when the local bus
voltage falls below 0.95 per unit. He suggested to re-visit the parameter assumptions in
the Phase 2 implementation.
Abe Ellis (Sandia) indicated that REMTF would want the flexibility to connect different
DGs to the Composite Load Model, which was also conveyed by Dmitry in a load
modeling discussion prior to the MVWG meeting.
Stephanie Lu (SCL) suggested that all three vendors should keep the consistency for
future implementation.
It was agreed that the next version of Composite Load Model will move towards a
modular structure and with the capability to have the hooks to the stand-alone DG
models. LMTF will take it for further discussion regarding the modular structure, the
capability of the hooks, and the data assumptions, and come back with a proposal.
D) Composite Load Model Monitoring Improvements in Software Implementation
GE provided an update on the load monitoring feature improvements, etc. that was
requested by users from the prior discussions:
 A new model was implemented to report total load being tripped per
area/zone/owner.
 DYTOOLS-HD was updated to be able to automatically detect Composite Load
Model and associated substation transformer and feeder and would trip them all
when specified to drop load.
 The in-run transient violation detection feature was updated so that it would
treat the high side bus associated with the Composite Load Model as the load
bus when checking for voltage and frequency violations.
The updates will be part of PSLF version 19.0_01, which is expected to release in early
April.
E) Phase 1, Phase 2 Studies and WECC-0100 Project
Jeni Mistry (SRP) presented SRP Phase 2 study results, and indicated slow recovery being
observed with the Phase 2 models.
Jun Wen (SCE) presented SCE study results on Phase 1, Phase 2, and sensitivity studies.
The Phase 1 study showed additional voltage dip violation could be seen when
compared to using the motorw. The phase 2 study showed that the voltage dip can go
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below 30%, the voltage recovery to pre-fault voltage typically takes 20 seconds, and the
post-voltage recovery can be as high as up to 120%. The sensitivity studies examined the
motor protection trip/reconnect settings. The differences are typically small but when
on the boundary can push the system to instability.
DOE awarded MEPPI to perform WECC load model sensitivity study. Joe Eto (LBNL) had
MEPPI team to the LMTF meeting and kicked off the project. PG&E, PacificCorp, SCE,
and SRP are four participating utilities. The objective of this project is to conduct a
parametric set of simulations that explore the sensitivity of WECC’s planning models to
uncertainties in the composition and behavior of loads. The results of the simulations
are expected to provide guidance that planners can follow in refining the composition of
loads used to conduct future planning studies. MEPPI will have a presentation at the
next LMTF meeting in June with proposed set of key sensitivity parameters and metrics
with test runs, then perform production studies with agreed large set of sensitivities
post June. MEPPI will meet with individual utilities between now and then to work
towards that.
WECC-0100 project is looking for MVWG on more studies to support the voltage
recovery criteria so they can get approval by the end of the year. Baj Agrawal (APS) who
is on the draft team specifically asked for model validation studies. Jun Wen (SCE), Jeni
Mistry (SRP), and Eric Bakie (Idaho Power) agreed to take the action and report back to
the next MVWG meeting.
F) Phase 2 model improvements
Phase 2 composite load model may include significant revisions.
Dmitry Kosterev (BPA) updated the analytic study that was done by Bernie Lesieutre
(University of Wisconsin) of sensitivity of AC motor stalling with respect to a point on
wave where a fault is applied and a rate of voltage decline. The results are consistent
with earlier observation made by John Undrill. AC motor stalls fast because of large
electric braking torque when an instantaneous fault is applied at voltage zero crossing.
Applying an instantaneous fault at a waveform crest or a voltage decline over a half to
one cycle seems to reduce the braking torque and improves motor’s chances to ride
through short-duration faults. The study implied that the existing performance model is
very conservative. If continuing with performance model, it is likely that we need a
curve for (Vstall, Tsall), and not just a single point.
Dmitry Kosterev (BPA) also updated on PSCAD modeling work done at BPA. Jeff Johnson
has been working with John Undrill on developing a “detailed” feeder model with
several commercial-type and residential-type loads. The model is subjected to
transmission level faults of various magnitude, duration and point-on-wave, to
determine the impact on single-phase compressor motor stalling. The model will be
used for benchmarking Phase 2 composite load model.
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The feeder equivalent structure may be revised based on the PSCAD studies and the
need to integrate various types of DGs.
Three-phase motor models may need improvement also, including protection and
control models.
John Kueck presented the table he compiled for commercial building motor load
response. Both “drop out” and recovery characteristic for typical motor loads were
provided. He also mentioned the BPA and SCE testing of VFD will be a complementary
information to what he has compiled.
III. RENEWABLE ENERGY MODELING
Abe Ellis (Sandia) provided an update of the REMTF work.
A) Energy Storage Modeling
A WECC REMTF Ad-hoc group on Battery Energy Storage System (BESS) led by Shengli
Huang (PSE) has actively worked with REMTF on the BESS since the Nov 2014 MVWG
meeting. A new model was proposed, called REEC_C, to be added to the set of recently
approved renewable energy models. The REEC_C model is essential based on the
REEC_A model, and when incorporated with the REGC_A model can then be used to
represent an energy storage system. Furthermore, the plant controller model can also
be used with these models to allow emulate various functionalities such as frequency
regulation. Since the last MVWG, the group has met and conducted several discussions.
A model specification document has been developed, beta version has been
implemented in PSLF, PSSE, and PowerWorld and tested. Pouyan Pourbeik (EPRI) has
also conducted one model validation study, the results of which are included in the final
model specification sent to the REMTF and MVWG chairs.
The Simple Model Specification REEC_C for Battery Energy Storage System was
unanimously approved.
The new model REEC_C was unanimously approved to be added to the WECC
approved dynamic model list.
This model is implemented in all three software vendors:
 PowerWorld – version 18 batch, expect to be released late March, early April
 PSLF – version 19.0_01, expect to be released early April.
 PSSE – version 34, expect to be released early April. (Also available in version 33)
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B) Enhanced Plant Level Control
The enhanced high-level plant controller work is in progress. The REPC_B model will
have additional new features, including interface with multiple WTGs, interface with
reactive support devices, and plant level power factor control option. The REPC_B
model specification and model are expected for approval at the next meeting. A draft
specification, prepared by EPRI, has already been circulated, based upon which the
software vendors are developing the beta version of the model for testing.
C) Enhanced Inverter-based DG
Driven by increasing interest in deploying PV inverters with grid support functionality
and standards activity (e.g., California Smart Inverter Working Group and Rule 21 effort,
IEEE Standard 1547 revisions), REMTF is considering to develop a new DG model that
can model the additional advanced features that are required. The new model will be
named as PVD2, and would include the following features: additional active power
controls, addition of time dimension to trip functions, auxiliary input for other
functionality. It is expected that the PVD2 model specification and model will be ready
for approval at the Nov MVWG meeting.
REMTF also recommended to add hooks in the Composite Load Model to allow different
DG models (Please see Load Modeling section).
D) PV Model Validation Guide
The existing MDB on the renewable models is deficient. Almost none of the wind/PV
data in the MDB has been validated. REMTF is developing model validation guide to help
improve the modeling and validation of the renewable models. The PV Plant Model
Validation Guide (drafted by Sandia) is under development, and is expected for approval
at the next meeting. The Wind Plant Model Validation Guide will be the next. REMTF is
also planning a model validation webinar in the summer of 2015.
E) Transition Plan for Renewable Models
The target completion date to remove the Phase 1 models is June 5, 2015. Eric Bakie
(Idaho Power) who is also a member of SRWG indicated that the WECC transition is
underway, but it will not be completed by June 2015 as planned last year. There are
discussions on how REMTF can help the transition. Pouyan Pourbeik (EPRI) commented
that REMTF can help provide the mapping between the 1st and 2nd generation
renewable models which the software vendors can take to implement the conversion
routines. This tool will help the conversion of the models without changing the
functions. The Generator Owner and Transmission Planner still hold the responsibility
for the data. REMTF and SRWG will report back at the next meeting on the progress.
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Phase 2 renewable generation models are not well understood outside REMTF, and
REMTF needs to conduct webinars to educate model users on the model structure, data,
including data differences between various manufactures.
It was also discussed that the missing renewable models are of higher concern than the
transition, Jun Wen (SCE) will relay it to John Gross (Avista).
F) White paper on limitations of generic models
The generic models deployed in the positive sequence program like any other model
have limitation, for example they are not applicable to very low short-circuit ratio
scenarios. Pouyan Pourbeik (EPRI) had agreed to take the lead in helping within REMTF
to develop a white paper on the generic model limitations. The white paper is expected
for approval at the next meeting.
IV. SYSTEM MODEL VALIDATION
A) JSIS Update
Dmitry Kosterev (BPA) provided an update on the JSIS activities. The presentations are
available at https://www.wecc.biz/Lists/WECCMeetings/DispForm.aspx?ID=10693
Nothing major after the last Nov MVWG meeting. The significant events detected by
PMUs between Nov. 1 2014 and March 19, 2015 are listed below:
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B) Model Validation Studies
Dmitry Kosterev (BPA) indicated that the validation studies for May 26 2014 DC RAS
event was in progress, and plan for approval at the next MVWG meeting.
Hamody Hindi (BPA) provided an update on the Chief Joseph Brake modeling, which was
still under testing. He will provide a presentation at the next MVWG meeting.
Slaven Kincic (Peak RC) and Brian Thomas (GE) presented the node-breaker validation
study on Oct 18 2014 Colstrip event. The simulation results showed optimistic frequency
response than in reality. As the next steps, Dmitry suggested to perform governor deadband sensitivity study. In addition to the dead-band, Brian suggested to focus on the
performance of hydro units and the impact of station service loads. The work will be
conducted under the Power Plant Model Validation and Data Task Force. It was also
discussed the use of node-breaker case for WECC planning case validation.
C) MOD-033
After last Nov MVWG meeting, a small group of MVWG members have discussed on
how WECC can help to comply with MOD-033. Kent Bolton (WECC) drafted a guide on
how WECC is currently performing the system wide model validation, which can be
leveraged by PC for local event model validation. This was discussed and reviewed at the
MVWG meeting. More work is needed. Jun Wen (SCE) will work with Kent on the guide.
It was mentioned that NATF also has a working group on MOD-033 that MVWG may be
interested at coordinating with. Joseph Gillette (SMUD) provided an update on the NATF
model validation field trial. The major turn-out was that a process flow chart was added
to the MWG procedure, and a template was developed. Joseph also shared SMUD’s
experience on power flow model validation. They can do local matches well with tie
represented with equivalents. Their planning case and state estimation case match
exactly so they can prepare a planning case for a local event within 4 hours.
V. GENERATOR MODELING, TESTING, AND MODEL VALIDATION
A) Cross Current Compensation Model
Pouyan Pourbeik (EPRI) and Shawn Patterson (USBR) briefed the group that the Cross
Current Compensation should really use reactive current. The total current is used
historically due to technology limitations. Pouyan completed the memo of the proposed
new Cross Current Compensation model. The new model, named as CCOMP4, will use
the reactive current for feedback, and allow up to four units. The CCOMP4 model
specification and model are expected for final approval at the next MVWG meeting once
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the software vendors have implemented it. Pouyan will work with Baj Agrawal (APS)
who offered to provide data to test/validate the new model.
B) Excitation System Models
Shawn Patterson (USBR) provided an update on the IEE 421.5, which is still in progress,
close to go out for ballot. The new target is to complete before the July IEEE PES General
Meeting. Shawn also brought up the reactive current feedback to IEEE 421.5. The IEEE
working group agreed to discuss and probably put some explanation to the total current
feedback, but not likely to change it.
C) Power Plant Testing and Model Validation
Steve Yang (BPA) presented the Power Plant Model Validation tool that was developed
by BPA. The tool is available for other interested members to use. Some set up work is
initially required for the tool to work, and Steve is willing to help.
Brandon Bouwman (Army Corps) presented testing results of all the units at Dalles. One
unit, which had some damage had different parameter (Kis was 5% different from its
sister units). This is a good example of testing all units instead of just one of the sister
units.
D) Power Plant Model Validation and Data Task Force
It was discussed to expand the scope of the Power Plant Model Data Task Force to
become the Power Plant Model Validation and Data Task Force with the additional tasks
on power plant model validation. The charter of the Power Plant Model Validation and
Data Task Force was unanimously approved.
Kent Bolton (WECC) reviewed the dynamics error list. Kent also showed the data error
list that was generated from John Undrill’s data checker tool, and there were over 6600
suspected data errors. Ken indicated that the Task Force will prioritize and take some of
the identified errors here to build into the dynamics error list. The renewable model
checking was also planned to be added to the dynamics error list.
As discussed during REMTF meeting, PPMVDTF drafted a roadmap for implementing
models of wind and solar power plants. Because models are not well understood and
have had limited use outside REMTF, a phased approach is more appropriate, similar to
work done with load models.
PPMVDTF developed an epcl for extracting wind and solar power plant model data from
WECC base case and dynamic data file. For 2015 light summer operating case:
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WECC case has close to 29 GW of total wind and solar generation
100 MW of generation connected at 69, 115, and 138-kV levels
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74 plants with 5 GW of generating capacity are connected at 24 to 35-V level, and
therefore have no collector system representation, as required by WECC Data
Preparation Manual, mainly Alberta and Colorado
94 plants with 5.2 GW of generating capacity have no dynamic models, mainly in
Southern California and Alberta
54 plants with 2.8 GW of generating capacity are modeled with inappropriate
dynamic models – “motor1”, “gentpf”, “genrou”, mainly in BC and Alberta
Looks like significant opportunity for model improvement.
VI. HVDC MODELING
Pouyan Pourbeik (EPRI) provided an update on HVDC modeling.
The LCC power flow model has always been available. There are some questions from
GE and PowerWorld yet to address. The LCC dynamics point-to-point model
specification is complete, the prototype is done, and the codes and specs have been
sent by EPRI to the software vendors for beta testing. The goal is to have the LCC model
specification and model for approval in the Nov MVWG meeting.
The VSC power flow model is completed in all three software tools now, the interface
with the dynamic model still needs to be decided and finalized.
The current status of WECC base case models for PDCI, IPP DC, and TBC was also
discussed.
PDCI is going through an upgrade. It is expected that the model specification and model
will look for approval early 2016. All at the meeting agreed that WECC does not accept
black box modeling. Thus, the MVWG chair requested that the new open source userwritten model for the PDCI HVDC being worked on by BPA, in collaboration we assume
with the equipment vendor, should be submitted to MVWG through the HVDC TF. The
HVDC TF offered to take a first look at the model and model documentation. Hamody
Hindi (BPA) took the action to pass this message back to the BPA contact person for this
project.
IPP DC also has an upgrade project. The current model is a user-written epcl with hidden
code. Saw Linn (LADWP) will also pass the WECC non-hidden code requirement to the
vendor and report back to the group with the upgrade information.
TBC has a user-written model as well. Ronnie Lau (PG&E) will send the latest code and
documentation to Pouyan (HVDC TF chair). Pouyan (with the HVDC TF) will review and
check to see if TBC can be represented with the generic VSC model that is under
development. It is realized that this is all a matter of timing, as the TF VSC model is still
under discussion.
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VII. RAS AND RELAY MODELING
James O’Brien (Peak RC) gave a presentation on where we are regarding the RAS
modeling. A WECC RAS standard format for power flow studies has been approved and
in place. Currently, only PowerWorld can read and write in this format. The target for
PSLF to implement is by the end of 2015. Talks are also in place with PSSE for
implementation. For RAS modeling in transient stability, James indicated that RAS
engineers are the ones who typically know the details, and asked for members to
understand their RAS and bring the information to him so that a common format can be
developed.
James Weber (PowerWorld) informed the group that a WECC RAS modeling webinar has
been scheduled on Apr 2nd, and an in-person workshop has been scheduled on May 2729.
Eric Bahr (NWE) provided an overview of the Colstrip ATR scheme and the model
specifications. The rough draft has been sent to MVWG. The ATR model specification
and model approval will be postponed to the next MVWG meeting. Eric is currently
performing more validation cases, and working with PowerWorld to clean up model
specification. Eric will also share draft model specification with PSLF and PSSE so they
can start working on it.
VIII. NERC UPDATES
Eric Allen (NERC) provided an update on the NERC standards and NERC MWG group
activities.
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The Disturbance Monitoring Equipment standard PRC-002 was filed and pending
regulatory approval.
NERC MWG has drafted a report to address the third step of the node-breaker
implementation plan; this step is the development of power system analysis
software with the capability of using “node-breaker” representation. The fourth
step is to look for pilot program.
A new TF was approved under MWG for turbine control modeling.
The revision of MWG Model Validation Procedure is planned to be posed around
end of 2015.
The event data sharing obstacle was also briefly discussed.
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IX. WECC PROJECT UPDATES
Shawn Patterson (USBR) briefed the team that WECC-0101 project (Generator
Validation Conversion) has been up for comments three times. The project is to decide if
WECC is just to follow MOD-026, MOD-027 or turn the existing WECC policy into a
regional variation. Either way, the WECC Policy will be withdrawn. Comments and
feedback have been light. He encouraged more MVWG member involvement since the
Policy is a MVWG creation.
Shawn also provided an update on the WECC-0107 project (PSS Design and
Performance), which is an effort to convert WECC policy on PSS into a standard.
Elements currently under discussion are documenting when PSS should be operational
and grandfathering existing units.
X. SRWG UPDATES
SRWG chair John Gross (Avista) provided an update on SRWG activities.
MOD-032 shifts the data preparation responsibility from TP to PC, there were
discussions on how PC and TP are coordinated. The DPM was revised for preparation of
the implementation of MOD-032 R1 by July 2015, John will provide MVWG the updates
to which one is the approved version when applicable.
The case data checks are going out with base case reviews, both power flow and
dynamics.
SRGW is working on collecting TPL-007 GMD data, no support was requested from
MVWG.
TPL-001-4 requires monitoring voltage ride through. PowerWorld is capable of using
lhvrt structure to convert dynamic data into power flow. John encouraged PSLF and
PSSE users to request the functions if they want it.
Eric Bakie (Idaho Power) asked for the capability of automatic capacitor/reactor
switching. James Weber (PowerWorld) suggested that Eric make a request to both
MVWG and vendors for quicker implementation.
XI. APPROVED DYNAMIC MODEL LIBRARY AND STATUS UPDATE OF MODELS
The REEC_C model will be added to the Approved Dynamic Model list.
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XII. PROGRAM UPDATES
GE PSLF, PTI PSS®E, PowerWorld, and PowerTech provided program updates.
XIII. OTHERS
MVWG members again raised concern that it is very hard to locate MVWG documents
at the new WECC website. Kent Bolton (WECC) updated the group that he was able to
get the MVWG page, the next steps would be to upload the documents to the MVWG
page. It was also discussed that MVWG will obtain a share drive as what SRWG has
done. Kent took the action and will report back at the next meeting.
Stephanie Lu (SCL) announced new MVWG chair and TF chairs:
 MVWG chair: Stephanie Lu (SCL) will be the outgoing chair, and Jun Wen (SCE)
will be the incoming chair.
 Load Modeling Task Force (LMTF): Jeni Mistry (SRP) will be the outgoing chair,
and Hamody Hindi (BPA) will the incoming chair.
 Power Plant Model Validation and Data Task Force (PPMVDTF): Kent Bolton
(WECC) will be the outgoing chair, and Steve Yang (BPA) will be the incoming
chair.
Jun Wen (SCE) reviewed the status of MVWG model, documents, and tools document.
This document will be available on the MVWG page and serve as a reference document
of the available documents and tools for MVWG members.
Jun Wen (SCE) reviewed the MVWG action item log. The MVWG charter and priority, as
suggested by Stephanie Lu (SCL), will be reviewed at the June MVWG meeting.
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