Advancements in energy storage are prompting MISO to expand its definition of non-transmission alternatives to include a new category: non-traditional transmission alternatives.
Storage behaves like transmission in several ways, Matt Tackett, MISO principal, told the Planning Subcommittee during an April 19 meeting.
“We started to realize that we’re struggling because we’re trying to make this thing too broad,” Tackett said. “We need to compartmentalize. Trying to force everything into one bucket is counterproductive.”
Non-transmission planning work is still in a “conceptual stage,” and a storage battery could be categorized as either a non-transmission alternative or a non-traditional alternative depending on how it solves a transmission issue.
MISO will seek stakeholder feedback on the issue until May 20. (See “MISO: More Time Needed to Refine Non-Transmission Alternatives Process,” MISO Planning Subcommittee Briefs.)
MISO to Revise Transmission Service Requests for Pseudo-Ties
MISO plans to revise the requirements for pseudo-tied resources to prevent them from generating without transmission rights, said Ankit Pahwa, MISO senior transmission planning engineer.
Pahwa said MISO is concerned that pseudo-tied resources might let their transmission rights expire continuing to import or export power. The RTO is proposing to add language to transmission service requests specifying that transmission rights be firm, point-to-point and maintained for the life of a pseudo-tie.
“What we’re saying is you have to maintain that transmission right to continue pseudo-tying out of MISO,” Pahwa said.
Additionally, MISO is considering performing system impact studies for all such transmission service requests. The RTO currently performs such studies only for pseudo-ties lasting longer than 18 months.
The proposed changes are part of a recent Planning Advisory Committee directive to “appropriately capture pseudo-tie impacts to MISO’s transmission system.”
MISO Questions Need for Transient Stability Analyses in MTEP
A new MISO white paper questions the need for completing a yearly long-term transient stability analysis as part of MISO’s Transmission Expansion Planning (MTEP) process.
The analysis models the dynamics and power flow of the entire system to provide insight into how the grid can return to stability after a significant disturbance, such as the loss of a generator.
A 10-year study during each planning cycle would satisfy NERC and MISO’s long-term planning horizon requirements, but MISO is wondering if it is necessary.
“The question is: Do you or do you not have to run the 10-year-out summer peak transient stability study?” Pat Jehring, of MISO’s planning expansion department, asked stakeholders.
According to Jehring, the RTO could conduct a long-term study using a broad approach — where the scope is widened to include all modeling changes and how they could affect the system — or a narrower interpretation of such changes. Jehring said MISO took the narrower approach with MTEP15 to save time. The RTO might now follow the broader option for MTEP16, with the analysis accounting for the impact of transmission, load changes and dispatch changes on the system.
Jehring said transmission owners have varying opinions about whether a long-term transient stability analysis would be needed for every MTEP.
Will Kenney, also with the planning expansion department, provided insight into the preliminary MTEP16 voltage stability scope, which identifies future reliability risks to MISO’s system.
Kenney said the MTEP16 scope will model a 2021 summer power flow and a shoulder power flow that assumes a 40% wind power contribution. The RTO will evaluate eight transfer paths during the 2021 summer peak, adding new analysis on the impact of eastbound transfers from Ameren Missouri and Ameren Illinois that sink in American Electric Power’s territory. Analysis of the U.S.-Canada interface will model a winter peak to examine transfers from Manitoba to the U.S. portion of MISO North.
The full scope of the voltage study will be presented at June’s Planning Subcommittee meeting, according to Kenney. The project should be completed in time for the board’s approval of the MTEP in December, he said.
— Amanda Durish Cook
