In the July 23, 2024, meeting of the Interconnection Process Working Group (IPWG) stakeholders were invited to review and submit feedback on Recommended GFM BESS Requirements (PAC-2024-2).
MISO seeks feedback on details of MISO’s proposed requirements and simulation test approach, which could include input on:
Please provide feedback by August 14, 2024.
AES would like to thank MISO for their responsiveness to our prior sets of comments. AES appreciates MISO’s removal of the 60-degree phase jump, modification of the 30-degree phase jump to 25 degrees, simplification of the loss of last synchronous machine test, and MISO’s responsiveness to our suggestions for clarifications on GFM response times. We continue to support adoption of these requirements for stand-alone BESS systems only during this initial phase.
AES would support MISO utilizing the soft adoption approach for DPP 2023 projects and a full adoption starting in DPP 2024. Since these 2023 cycle projects have already been submitted, utilizing a soft adoption would ensure that customers have time to adjust to the new requirements, and give both MISO and stakeholders more information to adjust these requirements following evaluation of submitted test results. Additionally, because these tests will take time to complete and many companies may have to hire consultants (which could be limited), it would be more practical to require interconnection customers to submit test results at Decision Point 2 rather than 1 for this initial cycle.
While AES would support the majority of details of these requirements being outlined in the BPM, since these requirements will have a financial impact on projects, AES would prefer that MISO submit conforming tariff changes to support the adoption of these requirements and outline any consequences for failing to meet them.
Furthermore, AES would urge MISO to reconsider its stance that additional compensation is not needed in light of adoption of these requirements. AES is in the process of quantifying the total impact to projects but has identified several areas of added expense to comply: 1) we expect inverter manufactures to increase costs on GFM-capable inverters; 2) we expect additional cost and effort to model GFM projects, specifically additional time to prepare for GFM EMT tests and for models that are not entirely developed. A generic PSSE GFM model was only recently approved and UDM models are difficult to troubleshoot due to the black box nature of the models; 3) we expect additional time will be spent validating the models match the inverter performance with power hardware in the loop (PHIL) testing; 4) we expect additional time and cost to commission GFM-capable projects. Additionally, since all regions are adopting slightly different variants of IEEE 2800 and GFM requirements, this will increase time and costs to identify and qualify GFM inverters to meet the MISO specific requirements.
Storage resources are already expensive, and adopting these requirements without additional compensation for the grid service these grid forming capabilities will provide further jeopardizes the viability of energy storage in the MISO market. Storage has already driven increases in reliability and resilience of the electric grid in CAISO and ERCOT markets. By unlocking energy storage barriers to entry and adequately compensating for their value, MISO can accelerate and even lead the way for advanced grid performance.
MISO presented several implementation options for grid forming (GFM) controls for battery energy storage (BESS) at the July 23 IPWG and posted an updated version of the whitepaper. The MISO Transmission Owners (Owners) support establishing GFM requirements for BESS and generally support the framework MISO has proposed. The Owners see value in these capabilities and support the implementation of GFM requirements for BESS as soon as practical. Of the implementation options presented, the Owners favor “Option C”, with full implementation for DPP 2023 while allowing for learning opportunities with MISO working with the Interconnection Customers and OEMs ahead of the Phase 2 test results submission.
TO: Interconnection Process Working Group (IPWG)
FROM: The Entergy Operating Companies
SUBJECT: Recommended GFM BESS Requirements (PAC-2024-2)
Date: August 14, 2024
The Entergy Operating Companies ("EOCs") appreciate the opportunity to provide feedback on the Recommended GFM BESS Requirements, presented in the July 23, 2024 Interconnection Process Working Group (IPWG) Stakeholder meeting.
The EOCs support establishing GFM requirements for BESS, and generally support the framework MISO has proposed. From the options proposed for implementation, the EOCs support “Option C” for full implementation while also allowing MISO to work with ICs and OEMs to review test results ahead of Phase 2 test results submissions.
The EOCs have provided additional clarifying questions and comments below for MISO’s review:
In Figure 2, as mentioned by the commentor in the redline draft, Category 3 resources can “survive and ride-through grid disturbances”. Voltage/Frequency Ride Through is required per PRC-024. In addition, the statement “for the purposes of MISO’s GFM IBR adoption, only IBRs that are capable of surviving grid disturbances are in scope (i.e., unifi Category 4), namely the loss of the last synchronous machine” should add some clarity that this scenario is beyond the expected PRC-024 ride through requirements which is required for all resources (even under reasonable weak grid conditions).
MISO should provide a definition of “stand-alone BESS system”. Many hybrid interconnections have a separate MPT for the BESS resource. In planning and operation realms, these resources will be difficult to distinguish from stand-alone BESS resources that enter into a shared services agreement with a solar facility to interconnect on the shared gen-tie line with its own MPT and PPC. Clarity is requested in defining stand-alone BESS possibly as not being controlled by the same power plant controller as a solar or wind plant.
About half of the “battery” entries in Entergy for DPP 2023 are associated with a separate application request for a solar resource (separate J#).
Would these “battery” entries be considered as part of a hybrid resource particularly if they are being controlled by the same plant controller as the solar plant?
If a battery is added to a solar facility in a subsequent DPP cycle, would that battery be excluded from the GFM requirements given that it will become part of a hybrid facility involving a solar plant in an earlier queue cycle?
Did the 23% value referenced for DPP 2023 as “stand-alone battery requests” take into consideration the fact that many ICs entered their hybrid facility as two separate requests or entered the battery resource tied with a prior cycle solar/wind resource?
Conformance assessment simulation tests are necessary as proposed in the GFM whitepaper. Are similar conformance modeling simulation tests not needed for the P2800 requirements? If not, please describe why conformance for the P2800 requirements can be done through other means.
Why are GFM IBRs exempt from following Section 7.2.2.3.4 “Current Injection during Voltage Ride Through” of P2800? In terms of dynamic voltage stability, shouldn’t a GFM IBR be designed to inject reactive current to support the voltage when system voltages drop below 0.9 pu? Please clarify if exemption of this section does not preclude requirements for a GFM IBR to inject current during low voltage conditions.
With regards to GFM IBRs being exempt from Table 13 (Voltage Ride Through Performance Requirements), is it assumed the PRC-024 ride through requirements still apply?
While already included in Entergy’s IBR requirements, it is recommended that MISO consider “negative sequence current” injection as a requirement rather than a recommendation given the complex protection issues and the existing capability of IBRs to produce negative sequence current.
Please clarify that the EMT conformance tests do not prevent a TO from requiring an EMT weak grid test as part of the interconnection study. It was unclear if “dynamic impacts” specified in the guidelines referred to just positive sequence dynamics or included EMT as well.
In the process, the TO and any other affected adhoc participant should be given the opportunity to review the tests results along with MISO in step #3.