FERC last week told MISO to provide more details around its plan to exclude wind and solar generation from supplying ramping service.
The commission issued a May 5 deficiency letter asking the grid operator to explain by midyear its proposal to disqualify its dispatchable intermittent class of resources from providing ramping capability (ER23-1195).
MISO staff have said that its wind resources are ineffective at ramping because their output is often trapped behind transmission congestion. They said when that occurs, they are forced to curtail intermittent resources from supplying energy but clear them for ramp capability, even though they’re undeliverable. (See MISO Plans to Bar Intermittent Resources from Ramp Capability.)
FERC asked the RTO to describe any operational challenges it has encountered with ramping supply issues and explain why it intends to only block intermittent resources from providing ramp capability. The commission pointed out that energy storage and other resources “are similarly undeliverable” when MISO clears up their ramp capability behind the same transmission constraints.
The agency also said the grid operator should describe how its plan is not discriminatory, an indication it believes the proposal could discriminate among resource types.
FERC said MISO should calculate the percentage of non-deliverable ramping megawatts from its intermittent resource class and the proportion of intermittent and traditional generation that clears for ramping from behind transmission constraints. It asked whether the RTO would consider non-intermittent and intermittent generation “similarly situated” when they’re located behind an identical constraint.
FERC also responded to MISO’s narrative that solar resources experience about 90% less congestion because they tend to be closer to load and are less likely to be curtailed. The commission asked why the grid operator wants to uniformly prevent intermittent resources from ramp eligibility when solar resources face fewer transmission obstructions than wind resources. It asked for an explanation about why the blanket exclusion should be considered reasonable.
J.T. Smith, executive director of market operations, has told stakeholders that MISO understands the criticism of its filing. He said staff doesn’t plan to make a permanent change, but they want to put the issue on “hold for the near term.”
“Under the current market conditions, the complication versus the benefit doesn’t make sense,” he told stakeholders in March.
Smith said MISO strives to make market participation available to all resources capable of providing services.