IPWG: Removing Storage Charging Limitations in GIAs (PAC-2024-3) (20240604)

The charging limitation language in the BPM is a suggestion due to TO sector feedback that was dependent on the assumption that the TSR process was a sufficient study process.  In particular, their feedback was "the Owners are concerned about voltage stability issues that could result from the instantaneous withdrawal of energy from the transmission system energy that are not studied in the Transmission Service Request evaluations."  Given that the documented Transmission Owner's concerns are related to stability issues, we would suggest that MISO use the current charging case as a stability only analysis to capture any long term stability issues that need to be addressed.  This would allow the Energy Storage developer determine if modifying controls could address the issue, fund a network upgrade, or voluntarily agree to limit charging from the grid through plant control limitations.  Furthermore, we would suggest that this will also maintains FERC Order 2023 compliance regarding the charging study parameters.  TSR's would still be required to be procured and go through their screening processes to identify any steady state issues.  It is our opinion that this will satisfy the need for a long term planning study, leverage the existing TSR's study process capabilities, and streamline the interconnection study processes through minor scope reduction on one of the study models.

WEC Energy Group recommends that MISO leverage existing MISO and TO processes for the addition of new load to evaluate transmission service for energy storage resources that charge from the grid.  While existing processes at the TO level may require some adjustment to account for the seasonal timing, duration and magnitude of charging from the grid, those existing processes are already well established and provide an avenue for the evaluation of transmission service for energy storage resources charging from the grid.  For example, ATC has a Load Interconnection Request Form (LIRF) that, with minor adjustments, can be used to request evaluation of energy storage charging from the grid.  Any requisite network upgrades that result from the evaluation of charging from the grid would flow through normal MTEP channels, including use of the Expidited Project Review (EPS) process, if appropraite.

Longer-term, WEC Energy Group supports evaluation of enhancements to the generator interconnection process to include the local TO's new load addition evaluation process to obtain transmission service for charging from the grid.  We believe that concurrent evaluation of generation interconnection and transmission service for charging from the grid is one option to consider.

DTE appreciates the opportunity to provide feedback to MISO on its proposal on the different options to remove storage charging limitations in GIAs.  This is a critical topic as storage assets will play a very important role in reliability and resource adequacy as the generation fleet trends towards more wind and solar resources.  A trend, which in the state of Michigan has been accelerated recently with the passage of clean energy legislation last November.  It is important for MISO to adopt policies that will enable all attributes of storage so that these systems are optimized and can provide system-wide benefits.  As a matter of principle, the policy should be applied across all interconnection pathways including Generator Replacement and Surplus Interconnection so that 1) current process efficiencies aren't compromised 2) interconnection costs are minimized.  As a short-term solution we would recommend that the storage load is submitted through MTEP, and that MISO re-evaluate charging limitations on an annual basis so that the limits can be adjusted as system conditions change.   

We appreciate MISO placing a priority on this topic and look forward to more discussion.  

At the June 4 IPWG, MISO presented its initial response to the issue submission regarding the lack of a defined process to remove storage charging restrictions placed on the storage during the generator interconnection process.  MISO reviewed its considerations for existing processes that could potentially meet a short-term solution.  Of the processes considered, MISO determined three potential options to re-evaluate GIA charging limitations. 

1. Submit the load through the MTEP process
2. Re-enter the generation interconnection queue (injection rights would remain)
3. Obtain long-term firm transmission service for the load
   
   

In response to the three options presented, the MISO Transmission Owners (Owners) have the following comments. 

Load interconnection studies require the involvement of the local Load Serving Entity (LSE).  Transmission Owners and the LSEs serving load on their systems utilize the MTEP process for load interconnections today so this option would be an appropriate avenue provided that the battery storage system owner has contracted with the LSE to have the charging load served and the LSE submits the load interconnection request to the TO.

Similarly, obtaining long term firm transmission service (either network integration transmission service or point-to-point transmission service) for the load would also be an appropriate avenue and involve the local TO and the local LSE in the process. 

The generation interconnection queue studies have different dispatch assumptions and contingencies compared to a typical load interconnection or transmission service study, so it may not be appropriate for this type of analysis.  The longer-term solution discussions to occur later at the PSC may be able to address some of the modeling concerns, but at this time re-entering the interconnection queue would be the least favorable option of those presented. 

Regardless of the location of the load study, the analysis should utilize NERC TPL Standards for load interconnections including n-1-1 contingencies.

There are cost allocation considerations for the associated charging-related upgrades that need to be discussed as well, and the Owners anticipate having those discussions as part of the longer term process improvements.

Clean Grid Alliance Comments on Removing Storage Limitations in GIAs

June 25, 2024

Clean Grid Alliance appreciates MISO’s efforts to improve policy regarding storage limitations, including the presentation from the June 2^nd IPWG meeting. We offer the following comments and feedback to MISO and the IPWG for consideration:

• CGA would like to acknowledge and strongly support MISO’s effort in seeking a long term solution for interconnection studies related to storage “charging” to ensure Network Upgrades, based on the actual behavior of energy storage. We look forward to engaging in those discussions as storage is unique and different than thermal or variable generation in its behavior, and therefore requires different treatment. We encourage MISO to begin working on this urgent issue at the PSC as soon as possible.

• MISO can address the immediate/short term need without any BPM or Tariff changes. BPM 15, Section 6.1.3.1[1]currently provides for charging limitations only under specific conditions and not 8760 hours of the year due to the plural on “rate(s)” over a single “rate” for all 8760 hours. Storage will not be charging under congested/constrained conditions because the costs will be high. Furthermore, many of the Network Upgrades identified may be a byproduct of the differences between load study procedures in the GIP vs MTEP and not show up in MTEP studies. Storage is not a generator itself, but financially depends on arbitrage –buying power inexpensively and selling it at a higher cost. It will de facto not charge when congestion is high, plus storage is hardware and software capable of ensuring it will not charge under conditions that it is programmed to avoid. This limitation would be similar to MISO allowing projects to oversize, while strictly adhering to a lower than full capable output set injection limit.

• While we consider the use of multiple charging rates as BPM 15 would allow for a viable solution, CGA also could support multiple simultaneous options to address charging limitations if MISO deems additional studies are needed. Long Term Firm Transmission Service cannot be a sole option to remove charging limitations, as it would be insufficient and unfair to non-NITS MISO customers, who are not eligible to obtain NITS transmission service at no additional charge. Long Term Firm Transmission Service for non-NITS customers is extremely costly and a significant barrier/unattainable for most storage projects, especially given the tight economic margins. While we have concerns about cost inequity in Transmission Service between utilities (NITS) and IPPs, we also do not oppose NITS, so long as other viable avenues are available to non-NITS/non-utility interconnection customers, such as AERIS/QOL, or an “Out of Cycle” process.

• CGA believes that any concerns regarding a loophole to circumvent the Generator Interconnection Process can easily be avoided. If charging limitations in GIAs were condition specific and not limited 8760 hours, no additional studies or processes may be needed and therefore no opportunity for loopholes exists. If MISO deems additional studies necessary, the Annual ERIS/QOL process would be a natural fit due to serving a similar function for injection GIA constraints, plus it requires a GIA to qualify for this process. The existing GIA requirement could potentially prevent circumvention of the GIP without any additional language.

• Clean Grid Alliance also supports an out of cycle type study process for storage charging that is similar to Surplus Interconnection and utilizes the latest completed MTEP or DPP Phase 3 cycle (whichever is most current) to evaluate storage charging. In fact, MISO could consider using either of these models as a starting point in the DPP as part of a longer term solution.

• Re-entry to the MISO queue process is not currently a viable solution. It could potentially be in the future, if new reforms are applied to the GIP study process to produce more accurate results for storage charging, and if actual queue proces timing was closer to the Tariff timelines. However, given these two limitations today, it is the least practical solution and not likely to meet the need.

Clean Grid Alliance greatly appreciates MISO’s efforts and consideration of this feedback.

[1] MISO BPM 15, Section 6.1.3.1. Storage Charging from the Grid

If a storage interconnection application indicates that it will charge from the grid, it will be modeled at its default maximum charging capability in the DPP Shoulder Peak charging case as shown in Table 6.1. For system constraints that appear only in the DPP Shoulder Peak charging case, limiting the battery charging rate(s) is an acceptable mitigation option. Any lower charging limit identified would be documented in the GIA as a control scheme requirement.

The Environmental Sector appreciates Clean Grid Alliance (CGA) bringing this issue of the policy gap regarding eliminating storage charging limitations in GIAs to the PAC and IPWG, as well as MISO’s concurrence that this issue should be addressed.  At the June IPWG meeting MISO suggested that three options were best suited to address this issue in the short-term for storage units with signed GIAs and has requested input on short-term options.

1. Submit the load through the MTEP process
2. Re-enter the generation interconnection queue (injection rights would remain)
3. Obtain long-term firm transmission service for the load

As CGA has laid out in its issue submission, MISO can assign charging limitations to storage projects that would be memorialized in a Generator Interconnection Agreement (GIA) if any constraints are found in the GIP shoulder case study for charging battery storage. It is possible that these same limitations may not be present in the future, but currently there is no Tariff or BPM mechanism to remove/adjust charging limitations in GIAs for battery storage when those limitations are demonstrated to not be needed. The Environmental Sector agrees that establishing a process and policy mechanism to remove or adjust any unnecessary charging limitations from energy storage GIAs would allow for more efficient market operations, including ancillary and emergency service, and increased reliability on the MISO system. 

Regarding the three options MISO has identified, the Environmental Sector does not have a preferred approach, but urges MISO to explore all options and to implement as many of these options as are reasonable, as each approach may work best for some energy storage resources but not others.  In the near term, we urge MISO to consider the short-term options CGA has submitted in their comments, and believe that three of those options - 1) employing the flexibility in setting charging limitations only during specific conditions rather than all hours of the year under BPM 015; 2) using the existing ERIS/QOL process; and 3) using the existing Surplus Interconnection study processes -  would require the least amount of change or extra effort on MISO’s behalf.

We also support continued discussion of long-term solutions through the PSC but agree that identifying one or more appropriate short-term solutions should be the first priority for MISO and stakeholders. However, we strongly believe that MISO needs to fully commit to finding a long-term solution, and not let this issue slide for many years, which we have seen occur in the past with respect to other issues related to inverter based resources (e.g. their ability to participate in the ramp product). In addition, considering the rapidly changing nature of the grid, we believe that the development of a long-term solution can be a good opportunity to take a broader look at MISO’s planning process to better incorporate rapidly evolving load characteristics and capabilities, and to better integrate the unique tools battery electric storage resources can offer to help maintain grid reliability under more dynamic conditions. As such, we put our full support behind a more robust, long-term resolution once a short-term fix is established.