LTRP Tranche 2 Reliability Analysis Dispatch Scenarios (20230605)

NextEra Energy Transmission appreciates the opportunity to provide feedback on MISO’s proposed scenarios for future LRTP Tranche-2 studies. NextEra’s comments are focused on the assumption of capping total renewable penetration at 80% penetration of load in power flow and stability models during LRTP Tranche 2.

Based on the information presented during the workshop on June 5, MISO confirmed the renewable dispatch of the reliability models will be targeted as either the average of the 95th percentile of coincident renewables or capped at 80% of the highest load. Adhering to such an approach may result in the curtailment of a significant portion of low-cost energy within the MISO region. For example, per the scatter plot on slide 8 of the Reliability Analysis Update presentation, during the Average Load conditions (105-115GW), MISO may experience several hours with total renewable output in the range of ~180GW -103 GW. However, per slide 13 it appears MISO intends to model the total renewable output to only about 90 GW in the Average Load scenario. The pattern of high curtailment is also observed in Light Load and Winter peak core models. This methodology prevents the opportunity to build additional transmission infrastructure capable of accommodating renewable generation beyond the 80% level. Additionally, the methodology contradicts the objective of modeling high renewables as outlined in MISO's Future 2A models and would impede the attainment of higher decarbonization goals set by MISO States and the utilities in those states. Therefore, NextEra proposes the following feedback regarding credible dispatch scenarios:

1. MISO's 80% cap appears to be conservative and is not supported by any recent study. The MISO Renewable Integration Impact Assessment (RIIA) study successfully investigated and identified several solutions to address reliability and frequency stability issues related to up to a MISO-wide 89% instantaneous renewable penetration in the 50% RIIA milestone. The RIIA study indicated that 6 GW of batteries in the Eastern Interconnection with 600 MW in MISO was adequate to provide frequency support in the 50% milestone[1]. MISO Future 2A assumes 31 GW of batteries[2], which is significantly higher than the RIIA assumption.  Further, RIIA indicated that “A combination of multiple technologies — such as high-voltage direct current (HVDC) lines, synchronous condensers, motor-generator sets and emerging technology such as grid-forming inverters — are needed to provide support, along with operational and market changes to identify and react to this risk as it occurs.”[3]Hence, if in LRTP tranche-2, MISO were to dispatch renewables to a higher penetration level and encounter any potential reliability or stability issues, MISO should follow through on evaluating those options instead of simply opting to curtail renewables.
2. Further, as per the details provided on slide 9 of the MISO presentation, it is stated that the current study does not cover the achievement of an instantaneous renewable penetration exceeding 80%. Nevertheless, it remains uncertain when a subsequent study dedicated to addressing the transmission requirements associated with higher levels of renewable integration will be conducted.
3. MISO should reassess its LRTP Tranche-2 area interchange assumption, which is currently limited to long-term commitments for firm transmission service[4] levels. Instead, MISO should allow for a higher export to other regions, for example, up to 15% of the system peak load.  This approach would enable MISO to dispatch renewables at higher levels and is consistent with the goal of increasing inter-regional transfer capability to strengthen the grid against extreme weather events. This approach aligns with increasing resilience against frequent extreme weather events, a key concern identified in the LRPT[5] initiative. Additionally, this objective is also a priority for FERC and Congress. There is increasing evidence that interregional transmission is the preferred solution for increasing resilience during extreme events and increasing market efficiency. In recent FERC proceedings in docket AD23-3-000, U.S. Senator John Hickenlooper and other intervenors pointed to the resiliency and economic value of the interregional transmission.[6] Assuming the status quo in interchange practices and capabilities limits the value renewables can bring to the MISO system and its neighbors. MISO states possess renewable resource that far surpasses their regional needs. Limiting regional renewables to 80% of regional demand artificially constrains efficient markets.
4. The impact of limiting renewable penetration in reliability models on the adjusted production cost (APC), congestion, and curtailment should be analyzed using PROMOD. As a part of the iterative solution adopted by MISO for LRTP preferred candidate selection[7], additional transmission solutions should be identified through PROMOD-based analysis to reduce curtailment and maximize economic benefits to develop preferred candidates. Reliability analysis can then be conducted to ensure that no harm is done to the system.

The Transmission Owners (TOs) appreciate MISO’s presentation at the June 5, 2023 Long-Range Transmission Plan (LRTP) workshop describing the dispatch scenarios, core models and other aspects of the reliability analysis for Tranche 2. The reliability analysis is key to ensuring the portfolio of transmission projects identified are the preferred solutions in addressing customers’ needs and the TOs appreciate MISO’s collaboration with our sector and the stakeholders in this process.

The TOs offer the comments below in response to MISO’s request for feedback on what was presented and appreciate them being considered.

• Prioritizing Scenarios and Identifying Duplicates:
  • The Twilight Summer, Winter Low Renewable, and Transfer #1 (west to east flows) described on slides 16-22 should have higher priority based on historical trends and expected future changes in the generation mix.
  • Given their potential impact on the system and to customers, the Twilight Summer and Winter Low Renewable scenarios should be incorporated into the core set of models to ensure they receive the full complement of reliability analysis as the other core scenarios.
  • Subregional east-to-west and Transfers #2 and 3 may represent duplicate types of transfers, so study of these could be combined for efficiency and/or to focus on higher-priority aspects of the analysis.

• Data Representation:
  • The TOs recommend presenting renewable output and load information on slide 8 of the reliability analysis presentation from the workshop in chronological order, as this could show if there are extended periods of time with renewable oversaturation or shortfalls. Along with showing renewables combined, it also might be helpful to separately show this information for wind and solar to see variations between these types of resources. Overall, representing the data in this manner could be helpful to identify seasonal renewable resource and load trends. 

• Model Base Assumptions:
  • MISO should confirm all dispatch scenarios respect the current contractual limits between MISO South and MISO North.
    • The Tranche 2 reliability study whitepaper (https://cdn.misoenergy.org/LRTP%20Tranche%202%20Reliability%20Study%20Whitepaper628669.pdf) does not specify how the contractual limit between sub-regions will be accounted for when dispatching generation.
    • Starting dispatch exceeding the current contractual limitations should be limited to Tranche 4 and beyond studies, where presumably new limits between the MISO South and MISO North subregions will be specifically evaluated.
  • LRZ 9 wind has the highest capacity factor in MISO, more than the expected highest areas of onshore wind generation in the upper Midwest. It appears the opposite occurs when reviewing solar output, where solar output in MISO South is expected to have the lowest capacity factor in MISO. The TOs request MISO to provide a review of capacity and energy by fuel type and region as a part of data review with the updated Future 2A assumptions.
  • The TOs request MISO to provide a regional review of resource and load patterns regarding daylight availability over time to address such questions as will there be a difference in Twilight hours between the eastern and western areas of MISO and northern and southern areas of MISO?
    
    
• Scenario Sensitivity and Robustness Testing:
  • Though not necessarily addressed in the workshop, the TOs suggest that MISO work with stakeholders to develop and conduct a sensitivity around a key variable that could greatly shape the preferred solutions identified in Tranche 2. Here are some possible variables to consider:
    • As was done for Tranche 1, a sensitivity could be conducted using high and low natural gas prices.
    • Load based on seasonal changes (especially winter peaking) or projected electrification (especially transportation).
    • A renewable resource drought. Using the chronologically sorted data from slide 8 of the presentation, MISO could identify a sensitivity to test a renewable drought using the following criteria: Prolonged lower solar and wind output; and depleted energy storage reserves.
    • Dispatchable resource unavailability due to outages.
    • Along with dispatching wind and solar at a given percentage, MISO could use wind and solar profiles from Ventyx or other source. 

• The TOs also request MISO to incorporate extreme weather event testing, particularly, extreme winter events.
  • As identified throughout the Renewable Integration Impact Assessment (RIIA), winter mornings will represent hours of highest system risk.
  • Due to the diurnal nature of northern winter load reaching peak in the morning and evening and transitioning solar horizontal irradiance over the course of the winter, there may be some evening winter hours with lower solar availability than morning hours causing evening hours to be more stressful to the system.

The TDU Sector appreciates the opportunity to provide feedback on LRTP tranche 2 reliability analysis dispatch scenarios.  Provided below are initial comments from the Sector.  In addition, the Sector previously provided feedback on MISO’s draft reliability analysis whitepaper and is looking for answers to questions and comments previously raised.  Understanding the whitepaper and MISO’s planned reliability analysis better will help inform the Sector’s thoughts and future feedback.  For example, the sector previous asked for clarification on the modeling and dispatch of the Flex units added to Future 2A as described at the April LRTP Workshop.  If MISO is planning to hold back the dispatch of flex units to only critical periods, the sector would like to see a scenario where these units are not held back.  The Sector’s previous feedback on the whitepaper is also provided below.

TDU Sector Feedback on Reliability Analysis Dispatch Scenarios 

• The Sector supports inclusion of additional scenarios, especially the prioritization of the Twilight and Winter Low Renewable scenarios.

• MISO should add a sub-regional west to east transfer scenario to the sub-regional east to west transfer scenario, which should encompass (and thus may replace the need for) Transfers 1 through 3.

• Rather than combining wind and solar output in a single bucket, it would be useful to establish and show wind and solar output levels separately.

• The scatter plot on slide 8 shows a large number of spring and fall periods where the renewable output is in excess of load. 
• MISO proposes an 80% upper limit on instantaneous renewable penetration for the LRTP Tranche 2 core models. 
• We would ask MISO to evaluate an additional shoulder-season scenario that considers renewable penetration up to 100%, with the excess above peak load used to charge batteries.  This may require additional storage resources (or construing some Flex resources as storage), which should be part of such a scenario.  We believe this would yield useful information – especially for those hours when wind energy output is used to charge batteries that are co-located with solar resources. 

• Coupled with potential SPP renewable output in excess of load, we can envision times when both SPP and MISO are exporting to the east.

• Alternatively (or perhaps in addition), a scenario that exports renewable output in excess of load to Manitoba and/or PJM could be examined, which could help identify inter-regional transmission expansion opportunities.

• MISO should add a MISO South-to-MISO North-Central transfer study.

TDU Sector Feedback on Draft Reliability Analysis Whitepaper – Posted 5/23/23

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

• 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.
• 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.
• 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.
• 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

• 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.
• We would also suggest that MISO consider including significant MTEP23 Appendix B projects, given that these address identified near-future needs.
• 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.
• 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

• 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

• 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.
• 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.
• 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.
• 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).
• 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 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.
• 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.
• 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

• The sector encourages MISO to consider how more efficient use of transmission lines can be integrated into this analysis and planning.
• 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.
• 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

• 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.

Submitted on behalf of Minnesota Power & Great River Energy - 

We appreciate MISO's attention to the impact of exports from MISO to Manitoba, as it is noted on Slide 15 that this condition will be incorporated into the Winter peak core model. In our joint comments with Grid North Partners, we have also suggested further consideration of this condition in a winter night time case with low renewables and depleted batteries. We think MISO should also consider the other end of the spectrum and evaluate a south flow case with the full Manitoba to MISO export level. MP mentioned this in slides from the October 2022 TO workshop illustrating the fact that the Future 1 study cases used for Tranche 1  did not exceed 1100 MW Manitoba export, which is nearly 2000 MW less than the firm export limit (3058 MW) and below typical Manitoba Hydro export levels throughout a good portion of the year based on hourly historical data. In the 2013 Wind Synergy Study, MISO found significant correlation between wind & hydro operations, with the ability to dispatch the hydro to fill gaps when the wind wasn’t blowing. We think this should be considered in the LRTP Tranche 2 analysis, perhaps as part of Transfer #1 Scenario or a different transfer scenario with low renewables in Zones 2-3 that looks a little more like the traditional simultaneous exports case with high NDEX, MHEX and MWEX.

Thank you for the opportunity to comment.

The OMS Transmission Planning Work Group (OMS TPWG) appreciates MISO’s work on the LRTP initiative and appreciates this opportunity to provide feedback. This feedback is from an OMS work group and does not represent a position of the OMS Board of Directors.

The energy transition detailed in MISO’s Future 2A will require a wider variety of cases for reliability planning due to the prevalence of intermittent resources and storage. The OMS TPWG believes that MISO’s core models appropriately capture several potential periods of heightened risk to system reliability. Given the crucial role that storage will play in maintaining system reliability, the OMS TPWG recommends that MISO examine storage under two additional dispatch scenarios during summer peak.

The first proposed scenario, full charging at highest renewable output, would inform the reliability risks on the system during the probable occurrence of storage charging during the gross peak load (and highest solar output) for dispatch during the net peak. MISO’s current summer peak case fails to consider the fact that storage is likely to be a load during the trough or belly of a future “duck curve.”

The second proposed scenario stresses the system in new ways by evaluating low coincident renewable output during the summer peak with storage discharging at 50% to make up for the lack of renewable output. This scenario assumes some storage is withheld for the net peak later in the day.  

The OMS TPWG encourages MISO to study the scenarios under which the transmission system will be the most stressed. If MISO believes that these two proposed cases do not stress the system to a higher degree than MISO’s proposed cases, the OMS TPWG requests that MISO explain why the two proposed cases do not stress the system to a higher degree than MISO’s proposed cases and conduct a sensitivity analyses using these two cases.

How did MISO take into account the recent carbon free Minnesota legislation when looking at the 80% instantaneous renewable penetration? If it is not taken into account, when will MISO address the carbon free Minnesota legislation in transmission planning?

Grid North Partners is a collection of utilities in the general Minnesota area and is made up of the following utilities: Central Municipal Power Agency/Services, Dairyland Power Cooperative, Great River Energy, Minnesota Power, Minnesota Power, Missouri River Energy Services, Otter Tail Power Company, Rochester Public Utilities, Southern Minnesota Municipal Power Agency, WPPI Energy, and Xcel Energy.

Collectively, the Grid North Partners Technical Team submit the following comments to MISO’s feedback request related to LRTP Tranche 2 dispatch scenarios for the reliability analysis.  The suggestions below pertain to the additional scenarios and would still result in six additional scenarios for consideration in Tranche 2 analysis.

1. Winter nighttime extreme cold with full Manitoba Hydro import level. 
1. LRZ 1-7 at winter peak
2. Depleted 4-hour battery and reduced efficiency due to extreme cold if some battery resources remain
3. Sources:  MISO south and external RTOs
2. High renewable, low load, extended heat period
1. Renewables at 80% with below average load in LRZ 1 and 3
2. Summer peak load in LRZ 2, 4, 5, 6 and 7 with limited renewables
3. Batteries depleted outside of LRZ 1 and 3, batteries available for charging to absorb some of the excess generation in those two zones.
3. Transfer #1 scenario: 
1. Keep the source as LRZs 1 and 3
2. The sink should be zone 6 and 7 to fully study across Midwest footprint (maximize delivery distance to save on multiple models)
4. Transfer #2 scenario:
1. Capture “Michigan Import”, no suggested changes
5. Transfer #3 scenario:
1. The sink should be Zone 1 and 3 to fully study across the Midwest region and reduce a scenario below the MISO proposed scenarios l?  Have LRZ 8-10 help support at maximum south to north. 
2. MISO could consider hydropower reduction for drought in Manitoba and the Dakotas, LRZ 2 and 4 will be part of transfer path in this scenario.
6. Keep Subregional East-to-West scenario

The Environmental Sector appreciates the opportunity to provide formal feedback on MISO’s LRTP Reliability Analysis for Tranche 2 as presented in the June 5, 2023 LRTP workshop. We appreciate that MISO is continuing to seek stakeholder comments on the Reliability Analysis, including on additional dispatch scenarios, as we requested in our comments on the Whitepaper.

We support MISO’s initial suite of scenarios that were presented at the Jun 5th LRTP Workshop and agree with MISO approach to studying high- and low-renewables output, to stress different transfer situations, and to understand the system’s ability to move power across subregions to take advantage of the geographic diversity of MISO’s future resource fleet. We also appreciate MISO’s more data-driven approach to identifying a reasonable lower bound to renewables output in the Winter Low Renewable Scenario, although we continue to have outstanding questions further articulated below. 

The Environmental Sector suggests additional reliability scenarios that build upon MISO’s proposed core and additional scenarios. First, we agree with other stakeholders that the JTIQ lines should be included in at least some of the modeled scenarios. The JTIQ lines are widely expected to be approved by MISO, perhaps before the LRTP Tranche 2 study process is complete. The absence of JTIQ projects from the reliability study models may prove difficult to navigate if, in fact, they are approved even as MISO is looking to finalize LRTP Tranche 2 project proposals. Specifically, we propose MISO consider iterations of the twilight summer scenario, the winter low renewable scenario, and the Transfer #1 Scenario that include the JTIQ lines. These iterations would maintain the current models, sources and sinks and provide valuable comparative analysis of the system issues with and without the JTIQ projects.

We also would like further analysis on how greater interregional connections would impact the system’s reliability. A number of assumptions go into the models designed to capture expected conditions in 2042 and an assumption of some reasonable increase in interregional transfer capacity between MISO and its neighbors is appropriate, particularly considering the growing attention interregional transfer capabilities are garnering at FERC, in Congress, and among stakeholders. For these scenarios, we would suggest two scenarios that include increased interregional transfer capability with SPP and PJM under a high-RE output (summer peak or summer twilight) and low-RE output (winter low renewable). Models, sources and sinks would remain constant in these scenarios with only the level of interregional transfer capacity as a variable. Even a modest increase of interregional transfer capacity could alleviate reliability issues or help MISO identify new issues that need to be addressed. Regardless, an understanding of how increased interregional transfer capability might impact the results of the reliability analysis - and the overall identified needs of LRTP Tranche 2 - will be valuable to MISO and stakeholders. 

 The Environmental Sector also has a number of unanswered questions regarding MISO’s input assumptions that we request further clarity on:

1. While we appreciate MISO’s data driven approach to determine a lower bound for renewable energy output in the Winter Low Renewable Scenario, we remain concerned that MISO is using a single data point to establish that level rather than an average of the lower 95th percentile that would mirror how it approaches establishing an upper bound for renewables output (notwithstanding the 80 percent cap that MISO is proposing). Simply using the lowest wind and solar coincident output does not alleviate one of our principal concerns that MISO is planning for a scenario that is unreasonably improbable from a statistical standpoint.  We would like further clarity on the statistical probability of MISO’s lower bound for renewable output and why MISO chose not to use a similar methodology as used in developing its upper bound. 

2. Has MISO considered an assumption that a subset of future renewable resources will adopt grid-forming inverters that may alleviate some of the issues MISO is seeing above 80 percent instantaneous penetration? Considering MISO is willing to assume a yet-to-be-determined “flexible attribute resource” to get the models to solve, it would seem reasonable to assume some level of adoption of grid-forming inverters - a currently commercially available technology - to also get the model to solve at above 80 percent instantaneous renewable energy penetration. 

We also have several questions regarding the implications of MISO’s 80 percent upper limit on instantaneous renewable penetration: 

1. How often does renewable energy exceed this cap, by how much, and for how long?

2. How does this cap impact the information previously provided by MISO regarding overall levels of renewable penetration, carbon emission reductions, the achievement of carbon reduction goals and targets, etc.?  Specifically, can states and utilities reach their carbon reduction goals with this 80 percent cap?   

3. Common understanding is that to achieve high levels of decarbonization, there will need to be an overbuilding of wind and solar generation.  How does this work with the 80 percent cap?

4. Does this cap impact MISO’s assumptions regarding the level of charge for storage resources, particularly with respect to hybrid resources that are charging directly from co-located renewables? Is there an assumption that charging of storage will assist in keeping the instantaneous renewable injection at or below 80% while still maintaining appropriate levels of decarbonization? If not, this must be taken into consideration. 

5. How is MISO coordinating and sharing the analytic results that initiated the imposition of the 80 percent cap? If issues were identified that are beyond the scope of the LRTP process, what is the proper venue to learn about those issues and participate in the search for solutions. We are concerned that MISO has not set this limit based on a technical analysis of the increased generation mix and siting assumptions used in LRTP, but on earlier studies under different conditions and scenarios. We request that MISO clearly document using LRTP models and assumptions and the need for any limitation that caps renewable generation.

Finally, we also have outstanding questions regarding the assumptions of storage and hybrid charging and dispatching:

1. How are storage inputs to the power flow model determined and what is the basis for those determinations?

2. Does, for example, “50% discharge” mean that only 50% of batteries are available at the relevant moment for the power flow model? If so, what is the justification for that assumption? Or is the 50% discharge meant to extend the temporal availability of storage as some sort of proxy for battery stacking? If so, we have concerns about that approach even as we continue to encourage MISO to consider stacking batteries as a way to maximize their value to the system. 

3. Do all battery resources have the same assumed battery availability percentage or does it vary by LRZ or some other metric?

4. Are the modeled charging and discharging of storage based on the relationship between load and price? If not, it must be, and if so, stakeholders need to see a chart or methodology that demonstrates that relationship.

We understand that the questions above are outside the scope of MISO’s formal feedback request on the reliability scenarios, but we include them here to highlight the number and breadth of outstanding questions. As always, we would welcome a call with MISO staff to talk through these outstanding questions, but believe the Environmental Sector is not alone in its confusion over MISO’s treatment of renewables, storage, and hybrid resources in the reliability modeling and request MISO consider hosting a “Q&A” session with stakeholders to make sure we are all on the same page as we head into our assessment of modeling results, identified issues, and potential solutions. 

Thank you again for the opportunity to provide this feedback. We appreciate all of your work to progress with LRTP Tranche 2. 

The Environmental Sector

ITC appreciates the opportunity to provide feedback. We propose the following transfer scenarios for consideration: