LRTP Informal Feedback: Reliability Whitepaper (20230428)

Otter Tail Power Company (OTP) appreciates the opportunity to provide informal feedback on the LRTP Reliability Study Whitepaper. Here are OTP’s comments, in order of the report sections:

Section 2, Paragraph 2: “Value-based” is not defined in this document.

Section 3, Paragraph 3: Developing credible scenarios with high interregional transfers is also important. A case with uniform generation patterns throughout the MISO footprint, based on a MISO-wide "severity index", may miss acute constraints in certain transfer scenarios.

Section 3, Table 1: Wind turbine generators are prone to cutting out at very low temperatures. Having wind on for the winter peak may mask serious voltage concerns under credible peak conditions, particularly in the north region.

Section 4.1: Any fictitious var devices should be removed as soon as possible (e.g. when a proposed portfolio enables a model to solve without them). Optimal locations for var support may be different before & after the tranche 2 portfolio.

Section 5, Paragraph 3: Same comment as Section 3, Paragraph 3.

Section 5, Item 1.a: OTP believes there would be value in evaluating a low-renewable winter peak load case. Both the proposed peak load cases have high renewable generation.

Section 5, Item 2.b.i: OTP supports studying this proposed scenario, as it is representative of extended cold weather conditions with a renewable drought (e.g. Winter Storm Uri).

Section 5, Item 3: The area interchange should factor in Future 2A resource additions. For example, F2A wind resources in OTP’s area will be serving load outside OTP’s LBA for the most part.

Section 6.1.1: It’s not clear what the proposed methodology is for selecting P3 or P6 events.

Section 6.4, Paragraph 2: Does N-2 refer to P3/P6 events, or stuck breaker/single point of failure events (P4/P5)?

Section 6.4, Table 2: Some stuck breaker schemes or single point of failure events may result in higher clearing times than those listed under the N-2 column of this table.

The TDU Sector appreciates the opportunity to provide feedback on MISO’s proposed reliability analysis whitepaper. Provided below are numerous initial questions and comments the sector has on the document. The sector may also have further comments and feedback once MISO’s proposal is better understood. As a result, the sector requests MISO dedicate time to reviewing the proposed reliability study for the tranche 2 effort with stakeholders as well as reviewing feedback received. This analysis is critically important for the tranche 2 effort and warrants spending time to ensure the approach is robust and is adequate to identify potential future system needs as well as support any tranche 2 projects.

1. Study Scenarios

a. Describing its goal as “focus on the worst credible conditions from the system point of view,” MISO has selected four scenarios to examine in the Tranche 2 reliability analysis.
b. One scenario appears to be summer peak (gross) demand. We would suggest that MISO consider adding a scenario capturing conditions of a hot summer day near sunset, which we expect to be a particularly difficult time under an expected future resource mix.
c. While MISO considers varying levels of renewable output, it appears that MISO proposes to consider renewable output levels that would be geographically uniform. We expect that significant geographical variation in renewable output may pose greater operational challenges. We would suggest that MISO consider also modeling cases with high renewable output in some regions and lower output in other regions.
d. The majority of resources in MISO’s expansion plan are non-dispatchable renewable resources. The sector believes MISO needs to add a case to understand system impacts from low wind and solar output. Understanding potential reliability issues from low renewable energy output is important to determining how to prepare for these potential situations and the solutions needed.
e. MISO’s modeling is missing a high local resource output scenario. Given the continued high rate of resources being added to the distribution system as well as the continued advancement and adoption of storage, MISO needs to understand the impact to system flows from a larger percentage of load being served from the distribution system and more local resources. High penetrations of local resources could fundamentally change energy flows. MISO should understand potential system and reliability needs under this scenario.

2. Initial New-Facility Assumptions

a. We understand that the models will include MTEP22 Target Appendix A projects. We don’t understand why MISO would use the MTEP22 TA topology when MTEP23 TA topology has been available for at least three months.
b. We would also suggest that MISO consider including significant MTEP23 Appendix B projects, given that these address identified near-future needs.
c. We are aware of some significant projects to be proposed in MTEP24 as well, and we believe tranche 2 analysis would benefit from inclusion of these projects.
d. We expect that it will be infeasible for MISO to prepare initial solved power-flow cases for F2A dispatch scenarios without including significant amounts of additional new transmission to the models. The document is silent on this critical step.

i. Does MISO plan to put its ‘indicative’ set of tranche 2 projects in the model?
ii. Some other set?
iii. How will MISO determine what additional facilities to model if even these projects are not enough?

The document is incomplete without addressing these questions.

3. Load Modeling

a. MISO should perform analysis to understand system impacts from a larger percentage of assumed load growth due to EVs being charged during off peak periods. The sector fully expects rate design solutions will incentive a significant portion of potential future EV load to be charged during times when the system is not stressed.

4. Generator Modeling & Dispatch

a. MISO has proposed to use simple assumptions related to the charging and discharging of storage resources. This approach is certain to underutilize these resources as well as overstate system impacts. The sector supports a planning approach that both stresses the system but also seeks to optimize planning and solutions. MISO should modify its modeling approach and/or analysis so that storage capability is not left on the table.
b. Also related to storage, MISO should incorporate the potential for storage durations longer than 4 hours. Given the long-range nature of this planning the sector does not believe it is reasonable to assume no advancement in storage durations. The sector suggests MISO study the potential impact of longer duration storage (e.g., 8, 12, 24 hour). This type of analysis would require additional efforts to complete but would be very helpful in understanding potential reliability issues and overall system needs.
c. Another issue related to MISO’s approach with storage is the dispatch profile that will be utilized. In general, MISO needs to understand potential impacts from a more rational dispatch of storage which reflects storage resources across the MISO footprint being discharged at different rates and timeframes as system needs require. Also, MISO has proposed an additional scenario representing early summer evening (sunset) that will assume 50% of the total nameplate of batteries are available to discharge. MISO should also understand system impacts if 25% or 75% of the total nameplate of batteries are available to discharge. It is very likely that a growing level of storage resources will have a material impact on energy flows across the footprint. Not capturing this impact creates a noticeable gap in MISO’s planning.
d. MISO has proposed that to ensure that projects are identified which enable MISO member plans and goals. It appears that natural gas combustion turbine (CT) dispatch may only be used in summer and winter peak cases. The sector believes these resources should be available for dispatch through all seasons. Resources added should be available for use to meet system needs. Also, advances in technology and fuel mix/use could enable a greater dispatch of these type of resources while meeting member plans and goals (as well as advances in the ability to add flexible resources other than gas CTs).
e. MSIO should clarify how the generic flexible resource type added to the expansion plan will be treated related to modeling and dispatch.

5. Sensitivity Analysis / Robustness Testing

a. A number of HVDC projects have been proposed that could significantly affect the future MISO system, including the MT-ND line proposed by Allete and Grid United, the IA-IL line proposed by Soo Green and the KS-MO-IN line proposed by Invenergy, and perhaps others. It appears to us imprudent to neglect to consider the potential impact of such lines on a Tranche 2 plan. Accordingly, we strongly suggest that MISO expand its study scope to evaluate such impacts. It is better to study the potential impact of these projects upfront than to ignore them and potentially create a material flaw in the business case supporting any final set of tranche 2 projects.
b. MISO’s initial F2A resource expansion and siting may be a reasonable initial future generation scenario, but further analysis may show that significantly more cost-effective resource mixes are available. We may find that different amounts of storage are an appropriate match to intermittent generation than assumed in the initial expansion, or that storage would be more effective if located differently than assumed, or that solar-output correlation indicates a different geographic distribution of solar. If these trends become evident over the next decade, we should expect them to be reflected in actual future resource expansion. We would suggest that MISO consider sensitivities with respect to these, and potentially other, resource-expansion and siting issues.
c. The sensitivities and robustness testing that MISO will perform with this planning effort is a critical component and should be described now. The sector requests MISO have focused discussions with stakeholders on the appropriate sensitives and robustness testing to complete. A key item which is needed is understanding of reliability issues and system needs from different resource mixes.

6. Analysis Scope

a. The sector encourages MISO to consider how more efficient use of transmission lines can be integrated into this analysis and planning.
b. The sector is also interested in whether and how MISO is planning to capture the potential impact of addition of flow-control devices to the system.
c. MISO’s modeling and study analytics should include the study of system inertia and ramping capability under a high renewable energy scenario.

7. Branch Ratings

a. MISO has indicated with the Winter Peak Load case that different “winter” line ratings will be considered where applicable. The sector understands that MISO is not planning to integrate Ambient Adjusted Ratings for all facilities as required by FERC Order 881 into reliability planning. The sector is interested in how else MISO is planning to capture line rating impacts into planning. For example, day/night ratings, manually adjusting line ratings as appropriate in base cases or potentially in production costs or economic modeling to be performed.

Mississippi Public Service Commission (MPSC) Response to MISO LRTP Tranche 2 Reliability White Paper Feedback Request (20230428)

In the April 28, 2023, Long Range Transmission Planning (LRTP) Workshop, MISO requested stakeholder review of the LRTP Tranche 2 Reliability Study Whitepaper by Friday, May 19. Feedback should include new topics to be considered in subsequent update and clarification requests on the content of the whitepaper.

In the context of this feedback request, "informal" means that feedback will be taken into account in the development of next steps and creation of materials for future workshops; MISO may not provide individual written responses.

Feedback

Generally speaking, this document should not have been released without additional in-depth information. We have included suggestions below to improve this document.

Transmission reliability analyses stresses the transmission system configuration at a moment in time by increasing flows by increasing generation and or load, taking elements of the system out (outages), etc., to test whether thermal or voltage stability limits are exceeded. The analysis is about overloading the system and testing where it starts to fail.

In MISO, the problem is that many of the real challenges of transitioning to a system with high penetration of intermittent generation will be associated with temporal imbalances between supply and demand, when wind and/or solar generation is down, not necessarily overloads from rerouting power. The issue is insufficient generation or the wrong type of generation to accommodate rapid supply swings. MTEP22 did not fully address this issue and it’s just now that the need for ancillary services (or generation attributes) discussion is starting to take shape.

We question whether the tools and methodologies currently used by MISO are up to the task of assessing the need for ancillary services to accommodate intermittent generation. Hourly economic dispatch models like PROMOD are incapable of analyzing the intra-hourly commitment and dispatch of fast ramping supply resources such as inverter based generation and storage systems.

MISO’s “design criteria” are undefined. This document generates many more questions than it answers. And, importantly, this document ignores the importance of critical ancillary services (or attributes) that generation will have to provide to make certain the transmission system will actually operate.

This document ignores the renewable-related repercussions that MISO’s RIIA Study predicts by not considering future adequacy of ancillary services.

Here are some of the questions that need to be answered:

1. The White Paper (p 2) states: “The LRTP initiative endeavors to develop a transmission plan to facilitate 1) replacement of the existing resource fleet with a new type of resource fleet and 2) electrification-based load growth in a manner that balances value in the near-term and long-term.”

    Question: How does the initiative balance value in the near and long term?

2. The White Paper (p 2) states: “The initiative is intended to develop a comprehensive plan using the MISO Future 2A assumption set to address transmission issues and needs.”

    Questions:

    a. Does the White Paper evaluate whether sufficient ancillary services will be available to support reliable transmission service based on the “new type of resource                fleet”?

    b. Has MISO quantified the various levels of ancillary services that will be needed (e.g., reactive supply and voltage support, operating reserves, regulation, inertia) to          “reliably serve load via variable renewable energy and conventional resources,” as stated in Core Case 1?

    c. Does MISO agree that adequate ancillary services are needed to ensure reliable transmission and balancing area services?

3. The White Paper (pp 2-3) states: “MISO annually builds reliability models based on specific process needs. These models usually cover 2- 3, 5- and 10-year horizons. LRTP, as a future-focused planning paradigm, necessitates a longer time horizon so 10-year and 20-year models will be developed for Tranche 2 Reliability analysis.”

   Question: Considering MISO’s LRTP future-focus planning doubles the planning period (from 10 to 20 years), and considering that the inaccuracy of forecast                   assumptions increases with time:

    a. What checks and balances does MISO include in the planning process to offset that increase in inaccuracy and focus on the most likely reliability issues?

    b. Will MISO focus on the reliability issues with the highest probability of occurrence?

    This question is relevant considering the potentially one hundred billion dollars in transmission investment that LRTP will require.

4. The White Paper (p 3) states: “As a regional planner, MISO is obligated to test transmission reliability under likely and possible dispatch patterns and develop transmission plans to ensure a reliable, robust, and resilient transmission system that can respond to the operational needs of the MISO region. Thus, MISO will focus on the worst credible conditions from the system point of view, while recognizing that local conditions may be different.”

     Questions:

      a. How does MISO define a “reliable system?”
      b. How does MISO define a “robust system?”
      c. How does MISO define a “resilient system?”
      d. Are any of these terms defined in the MISO Tariff or NERC Rules?
      e. If these terms are not defined, how will MISO “test” to ensure these “design parameters” have been achieved?
      f. What does MISO mean when it says, “focus on the worst credible conditions from the system point of view, while recognizing that local conditions may be                     different?”

      General Comment. Without defining the design criteria (the “three Rs”), there is no way for engineers to design a system that meets these criteria and certainly no           way to verify that the criteria are met.

5. The White Paper (pp 3-4) states “These broad base [4 Core] models will encompass multiple uncertainties around variable renewable energy output, load profiles, and seasons, thus providing the platform to perform a wide range of reliability studies.”

      Questions:

      a. Will these models address uncertainties around the availability/unavailability of ancillary services (or attributes) necessary to provide transmission service, e.g.,                reactive supply/voltage support, regulation, inertia, operating reserves, ramping capability?
      b. If not, where/when are the models tested against these services?
      c. Will MISO identify a minimum amount of each of these services that will be needed consistent assumed resource futures? {Note: Section 4.1 Generator Modeling            addresses what generators can provide, not what the system needs to accommodate the influx of renewable generation.]

6. The White Paper (p 4) describes Case 1 as “Summer Peak Load Represents summer peak demand which is the highest load on the annual load duration curve….” and renewable and storage dispatch as “Wind and solar maximum coincident output in the summer between 90% and 100% of the annual peak demand … with Storage off.”

      Question: Should MISO consider a Summer Peak Load case during a short or long period wind drought, solar drought, or both? That scenario, which is not far                  fetched at all, would seem relevant to the reliability of the system as it could represent a stressful system condition requiring large transfers from neighboring areas.

7. The White Paper (p 4) section entitled Topology Modeling, states that only “approved transmission planning projects from the MTEP22 planning cycle will be modeled including the LRTP Tranche 1 Portfolio.”

     Question: Why doesn’t MISO consider a case that incorporates an HVDC line that is advancing through state regulatory approval and is scheduled to be in operation       within the time horizon of the Study (Invenergy’s Grain Belt Express project). This project should at least be included as a sensitivity so that State Commissions can         consider its impact in the siting process.

8. What type of adjustments to Area Interchange limits does MISO expect to consider 20 years out (White Paper, p 5)?

9. The White Paper (p 5) states “the reliability models will add generation identified in in Future 2A expansion and siting.”

    Questions:

    a. Is that generation currently reflected in the interconnection queue with executed generator interconnection agreements?

    b. Is the generation incorporated in state integrated resource plans or similar state proceedings?

10. The White Paper (p 6) states that MISO is using Vibrant Clean Energy (VCE) renewable energy outputs.

    Questions:

     a. How does MISO expect to harmonize the generation expansion and siting of Future 2-identified renewable generation with the generation and siting in the VCE               Study? The VCE Study recognized the poor wind profiles that exist in MISO South and assumed that any wind generation requirements would be satisfied through           imports from SPP. In contrast, MISO Future 2 assumes that all renewable generation to serve MISO South load is sited in the MISO footprint.

     b. Was the “consecutive three-year weather and power dataset for wind and solar generators at 3-km, 5-minute resolution across the entire Eastern Interconnection               (EIC) footprint” that MISO proposes to use developed by VCE based on historical concurrent weather data?

     c. If not, what was the source of the data set and why is it reliable?

     d. If the VCE wind and solar data is not concurrent, will MISO develop current data? Without current data, it will be impossible to understand the benefits of the                   geographic weather diversity in MISO’s footprint.

Environmental Sector feedback re: LRTP Reliability Study for the Tranche 2 Effort

The Environmental Sector appreciates the opportunity to provide informal feedback on MISO’s LRTP Reliability Study for Tranche 2 Effort posted on the April 28, 2023 LRTP workshop. The document gives an overview of the proposed reliability analysis for Tranche 2 including base modeling approach and assumptions, and the Reliability Study Whitepaper (“Whitepaper”) is a good start to communicating this effort to stakeholders and improving the accessibility of this process more broadly. We understand the Whitepaper is a “living document” and will be updated and revised over time.  We applaud MISO for this effort, and offer the following suggestion for its updates:

1)      The Whitepaper should include clear and detailed descriptions of, and justifications for, all scenarios and sensitivities used in reliability modeling. Given the resource transition represented in Future 2A, assumptions around performance and capability of wind and solar resources are critical to the reliability analysis and a key element for stakeholders to understand as we explore results, issues, and solutions. Overall, MISO’s descriptions and offered justification for the four core cases are informative. But there are critical elements of these scenarios that should be fleshed out to better inform stakeholder engagement.

For example, the document states that since the MISO system is dispatched as one balancing authority, the renewable energy output will be evaluated for the whole system, but the Whitepaper does not clarify if this means that the whole MISO footprint will be modeled with the same meteorological assumptions. While we assume that MISO is using more granular wind/solar dispatch assumptions, the Whitepaper should include detailed discussion and explanation on how the meteorological data provided by Vibrant Clean Energy (VCE) was used and how these assumptions impact or inform the reliability analysis. Understanding how this level of granularity and any potential biases or gaps in the data informs MISO’s study will be critical for meaningful stakeholder engagement now, and going forward.[1]

Stakeholders need to understand MISO’s additional scenarios and sensitivities, which should be clearly described in the Whitepaper in the future. The March 10, 2023 LRTP workshop presentation on reliability dispatch methodology identified four additional scenarios to be studied via transfer analysis techniques. The Whitepaper, however, does not clearly identify the range of dispatch adjustments and transfer study scenarios that will be performed. If MISO intends further discussion with stakeholders to define those additional scenarios before including them in the Whitepaper, then we look forward to those ongoing discussions. Regardless, the range of dispatch and adjustments and transfer study scenarios needs to be clarified in the whitepaper.

2)      Battery storage dispatch assumptions need further discussion. We appreciate MISO’s ongoing efforts to refine battery storage dispatch assumptions and the changes that were recently made in response to stakeholder feedback. Capturing battery storage’s potential to provide energy during periods of system stress is a critical element to maintaining a reliable system with high penetrations of wind and solar resources, and an area where stakeholders believe modeling and methods should capture the full potential and capability of storage and hybrids during periods of  high stress. While many of the modeling tools currently available are simply not capable of capturing the full potential of storage, we urge MISO to:

a.       provide detailed evaluation of how storage resources and hybrid projects are modeled

b.       articulate the limitations of current modeling tools and datasets

c.        provide the thinking or process behind  MISO’s proposed assumptions for energy storage [2], and

d.       identify potential improvements for future analyses.

This will better inform the MISO stakeholder process and ultimately produce more meaningful and useful results. For example, a discussion of how the proposed “straightforward assumptions” might undermine the perceived value that batteries bring to the grid would be beneficial. This explanation would not compromise MISO’s credibility, but rather serves stakeholders by providing a deeper understanding of the challenges that must be overcome as we continue to refine our analytic capabilities to meet the demands of the changing system.

3)      More description and discussion of the modeling tools is needed. Core to any meaningful understanding of a modeling exercise is an understanding of the modeling tools being used, how they make decisions, what they can tell us and, perhaps just as important, what the modeling tools cannot tell us. Each modeling tool is different and has inherent attributes, shortcomings, and biases. We recognize the Whitepaper is intended for “transmission planners familiar with modeling processes at MISO and NERC,” however it may still be helpful for the Whitepaper to include a short  description of the tools being used, what those tools are designed to assess, and any relevant discussion of how MISO might address modeling gaps or shortcomings in future iterations of LRTP reliability studies. If more detailed descriptions of these modeling tools exist elsewhere, such as in MISO training modules, the Whitepaper could point to those other resources.

4)      More discussion of how demand is evolving would be helpful. The Whitepaper does a good job of describing the various load conditions that MISO intends to study, but is lacking in articulating the connection between what is detailed in the Futures Whitepaper and how those assumptions are reflected in the reliability scenarios. Particularly with respect to Future 2A, where more robust assumptions around electrification drive significant load growth and potential changes to load shape, understanding the connections between MISO’s input assumptions regarding evolving load and how those manifest into new or exacerbated challenges to be studied in the reliability study process will provide context for stakeholders. Also, the Whitepaper makes no mention of distributed energy resources that begin to show up in a meaningful way over the course of the study period and have been significantly ramping up in just the last 2 years. Again, stakeholders would greatly benefit from a description of the dispatch assumptions for DERs and how that impacts load.

In all, the Environmental Sector continues to appreciate MISO’s efforts to inform and educate stakeholders throughout the LRTP process. Stakeholders benefit from a robust Reliability Whitepaper for the Tranche 2 Efforts. The current version is a good start and with the additional pieces articulated above, will provide a strong foundation for stakeholder engagement in reliability studies going forward. Thank you for the opportunity to provide informal feedback. We look forward to the ongoing discussion.

[1] We want to commend VCE’s dataset for having robust documentation and yielding decent validation results. However, there are still biases within the dataset that have yet to be examined. As an example of an unanswered question regarding this dataset - is there a tendency to overpredict at low wind speeds? How these systematic biases could affect MISO’s reliability analysis should be further evaluated.

[2] For example, we note the battery storage dispatch assumptions articulated on page 7 of the Whitepaper reflect, at most 60% of battery storage nameplate capacity being available for discharge during any particular scenario. The Environmental Sector questions this assumption and strongly encourages MISO to provide justification for those assumptions in the Whitepaper.

The Transmission Owners (TOs) appreciate MISO’s development of the whitepaper describing its intended approach for the reliability modeling and analysis for Tranche 2 of the Long-Range Transmission Plan (LRTP) initiative that was discussed in the April 28, 2023, Long Range Transmission Planning (LRTP) Workshop. Clearly, the approach for this part of the Tranche 2 effort is key to ensuring the portfolio of transmission projects are the preferred solutions in addressing customers’ needs.

The TOs offer these comments in response to MISO’s request for feedback on the whitepaper:

• The whitepaper does not address which set of transmission solutions MISO will start with nor how variations in that set of facilities will be added throughout the analysis. This is a key element of the analysis that should be addressed at this point. The TOs would also like to see MISO lay out the process for adding those mitigations in the model-solving phase and in the power-flow and dynamics analyses phases.
• The needs being addressed in the analysis should be addressed first and then possible solutions to address those needs should be considered. Again, we think this is a key part of the analysis that should be reflected in the whitepaper.
• MISO in the workshop (slide 4 of the Future 2A siting presentation) described a “twilight” scenario in which there is unserved energy at sunset (winter and summer) and sunrise (winter), but it is not reflected in the whitepaper. This is an important scenario to capture because the MISO footprint is starting to experience this now. Moreover, there is a potential reliability risk with this scenario. This is particularly the case in the winter, as it is projected that there will be a high level (80%) of renewable penetration expected in Future 2A and there are many hours throughout the year where MISO could potentially have challenges serving load with such factors as increased electrification (including heating), and periods of time beyond four hours without sun and low wind. There are times of the year and areas of MISO where these conditions are exacerbated and reliability is at a higher risk. This is especially true in the northern parts of MISO during winter, as there are longer nights, snow-covered solar panels, and higher loads due to electrification. The TOs would like to have assurance that Resource Adequacy standards (like 0.1 LOLE) are met in the final siting (2A) used for LRTP Tranche 2 reliability modeling.
• On p. 3, Case 2 includes a “wind moderate output”. What is meant by moderate output? How does this relate to the methodology described in section 5? The whitepaper should define quantitatively for all of the cases the meaning of low, moderate, and high output, including for each season and whether it changes over time.
• It appears MISO is not acknowledging the Regional Directional Transfer (RDT) limit between North/Central and South sub-regions. According to the whitepaper, MISO is dispatching the region as a single BA. MISO should either dispatch the entire region such that the 2500 MW and 3000 MW limits are enforced or dispatch MISO North/Central and MISO South as separate BAs. The economic cases for LRTP will have the RDT constrained and the limits enforced, so it makes sense the reliability cases need to have the same limits.
• Please clarify the types of events MISO is considering in Section 6.1.1, which states: “In addition, MISO will simulate contingencies representing a limited set of high impact events.” 
• Long Duration Storage will be considered by MISO as a Flexible Attribute Unit in addressing unserved energy in the “twilight” scenario and, seemingly, others. It would be helpful for MISO to provide more detail on how Long Duration Storage would operate and be dispatched in this capacity.
• It appears MISO proposes to consider fixed renewable output levels that would be geographically uniform. However, it is clear there is geographic variation in output levels. MISO should explore how to model cases with high renewable output in some regions and lower output in other regions.
• The TOs are noticing high amounts of curtailment in LRTP PROMOD studies that reflect high wind and solar coincident dispatch.  The TOs would like to see detail on the ways mismatch between generation and load will be handled in the T2 reliability models.  Specifically, section 5.3 of the whitepaper talks about satisfying generation=area interchange+load+losses.  The TOs would like to see detail added to show ways this balance is respected at times renewable dispatch is already greater than area interchange+load+losses.
• Large-scale dropout of inverter-based resources (IBR) should be incorporated into the study discussed in paragraph 4 of Section 6.4. Alternatively, please explain reasons this is not considered a realistic contingency.
• Firm transactions should be modeled (example: 1400 MW Manitoba Hydro import).
• The TOs recommend dispatch assumptions around EV, storage and other technologies from Future 2A should be reflected within the whitepaper.
• The TOs would like to see detail on the electrification-based load growth mentioned in the Overview section; the Load Modeling section does not provide detail.
• Please define “impact/transfer” in Table 1.
• A BAL-003 analysis may prove necessary in the light-load model, as was done for RIIA.
• Please explain more about the way the transmission topology in the reliability models will “generally align” with that in the economic models; ideally the most accurate topology is in the reliability models.
• Please explain more the ways the generator modeling will differ from reliability models to economic models. If it is only the reactive capability, please state this.
• Section 4.4 seems to only be discussing transactions to and from MISO (external). Please add a section about internal transfers within MISO. Section 5 indicates the transfers within MISO will be allowed to float, as needed, with different loads and dispatches. Please explain.
• Please elaborate on this sentence on p. 6: “This coincident peak variable renewable energy amount will be applied to the peak load on the system.”
• Please explain the reasons for assuming storge will have durations of 4 hours, as 4-hour batteries have been shown in RIIA to be insufficient.
• Section 5 states Area Interchange for each zone will be used. Please state the methods for determining the zones’ Area Interchange values.
• Please state the “other metrics” to be used in the Criteria section.
• Under section 6.4, please state the ways MISO will determine the necessity (“If necessary”) of study on additional models and scenarios.
• Please explain the CCT-cutoff in section 6.4 and ways severe faults can or cannot “slip through the cracks” with this method. It seems safer to run all the faults and automate the reporting for stability metrics.
• Section 6.4 says inadequate performance will result in a review of it in coordination with steady-state and regional needs. Another option MISO should consider is to add transmission facilities to solve the criteria violations.

Thank you in advance for consideration of this feedback.