By Amanda Durish Cook
MISO is planning to provide storage with make-whole payments for price volatility, subject storage resources to dispatch and regulation performance rules, and exempt storage from certain uplift charges, officials said last week at a special conference call on compliance with FERC Order 841.
The RTO is proposing to use the same uninstructed deviation threshold it uses for other generators, Market Quality Manager Jason Howard said during the call on Aug. 21. MISO is currently refining a proposal to implement a more performance-based uninstructed deviation threshold. (See “Final Uninstructed Deviation Proposal,” MISO Market Subcommittee Briefs: May 10, 2018.)
Electric storage resources will be eligible for day-ahead margin assistance payments when they are dispatched below their day-ahead megawatt commitment and revenue sufficiency guarantee payments when they are dispatched in real time above their day-ahead commitments. They will also receive RSG payments when committed above their real-time economic minimum limit when committed in real time under a must-run commitment.
Storage could also be manually redispatched by MISO operators to contradict their day-ahead schedule or real-time offers, even to zero output, RTO staff said.
The RTO is also planning to exempt storage from its revenue neutrality uplift charge, its demand response resource uplift charge, and load ratio share adjustments and ancillary distributions. However, MISO said there was a potential for storage resources to be assessed real-time RSG distribution charges.
MISO plans to vet its performance rules with its Independent Market Monitor.
“We’ve just begun our collaboration with the Market Monitor … so that they do have an initial glimpse of our thoughts,” Howard said. He added that MISO will return with any rule changes regarding threshold and performance at the Sept. 13 Market Subcommittee meeting.
Some stakeholders asked for more specifics about MISO’s Order 841 compliance filing. The RTO said in June it would respond to Order 841 by dividing storage bid parameters into four operating modes: discharging, charging, continuous operations and offline. Market participants will be left to choose a mode for individual dispatch intervals and will also be responsible for managing the state of charge of their storage units. (See MISO Weighing Feedback to Storage Proposal.)
The Energy Storage Association’s Rao Konidena, formerly a MISO adviser, said storage owners must be able to switch among multiple market services, for example regulation to spinning and energy to regulation.
The ESA wants MISO to revise its proposal so that the RTO receives telemetered data in real time when an offline storage resource “returns to interacting with the grid” and can update the state-of-charge in offer parameters for the next dispatch interval. Konidena said that MISO has agreed that a resource’s state-of-charge when returning from offline mode may deviate from the resource’s last metered setpoint.
“MISO has recognized that a storage asset may go into offline mode and leave the market but still remain active charging and discharging to and from other sources and sinks,” Konidena said.
He also said MISO and its Monitor must address how such state-of-charge deviations when returning from offline would be handled.
“The concern is we would be penalized for that behavior,” Konidena said.