After pulling its initial proposal to facilitate better use of fast-ramping resources in managing power system supply and demand mismatches, the Midcontinent ISO has received the go-ahead to move forward with its amended plan for handling increased supply-side volatility brought on by the growing integration of intermittent renewable resources.
MISO determined in October 2019 that its original filing submitted a few months earlier warranted “clarification and further explanation." It, therefore, asked the Federal Energy Regulatory Commission to postpone action on that filing and subsequently submitting an amended proposal on Nov. 19, 2019.
FERC on Jan. 14 approved the amended proposal, which added new terms, definitions and offer parameters to MISO’s tariff in preparation for enhancements to the automatic generation control, or AGC, system MISO uses to balance supply and demand on its system.
Under the revised tariff language, the AGC will send resources instructions at least every six seconds to either raise or lower output to address imbalances between supply and demand.
The AGC’s deployment of regulating reserves was previously load-following because traditional resources are slow-moving. With more intermittent renewables being connected to the grid, MISO determined alternative AGC signals were needed to provide better system control and crafted the “Fast First” AGC enhancement to better use newer fast-ramping resources, such as batteries, for frequency regulation, the ancillary service that manages supply-and-demand imbalances.
MISO defines fast-ramping resources as those with a ramp rate greater than 80 MW/minute, at least a 70% performance score when responding to regulation signals and must be able to operate for more than 20 minutes.
Resources that do not qualify as fast-ramping will continue to receive the existing regular regulation signals from the AGC, while fast-regulation signals will be sent to those offered as fast-ramping resources. The pricing and compensation rate of resources will not change, regardless of whether a resource is fast ramping or not.
The grid operator said the AGC enhancements were not specifically designed to accommodate energy storage batteries, but those resources would likely be able to respond to fast-ramping signals. By contract, MISO said it was less likely that mechanically-based storage resources like pumped hydro would be able to meet the MW/minute ramp-rate limit as those resources require the operation of physical equipment to increase or decrease water flow.
MISO’s interconnection queue, as of December, included 2.5 GW of battery storage projects. S&P Global Platts Analytics expects less than 300 MW of batteries to be commissioned in MISO by 2024, accounting for the delayed implementation of FERC’s electric storage market participation order.
“Today, MISO has less than 50 MW installed, but the new AGC enhancement may accelerate deployments,” said Felix Maire, clean energy and storage senior analyst at Platts Analytics.
The Fast First AGC framework allows market participants to optimally manage the operating conditions of stored energy resources by accounting for state of charge and adhering to MWh limits representing the percentage of a fast-ramping resource’s capacity up to which it would be offered.
“Fast regulation signals would enable fast-ramping resources to be deployed first, and also un-deployed first, thereby helping preserve their useful life,” MISO said.
Specifically, “the Fast First AGC would deploy regulating reserves through the fast-ramping resources first, thereby achieving the system balance quickly,” MISO explained. “In each AGC cycle’s continuation, this deployment will then be shifted on to the slow responding resources. As the slow responding resources start responding to the deployment signal, the fast-ramping resource deployment would be decayed down, thereby preserving them for longer participation in future regulation deployments.”
MISO expects fast-ramping resources to reduce the amount of regulation deployment that is needed and to free up traditional, slower ramping resources that would “otherwise be ‘stranded’ by commitments to provide regulation service.” Further, the grid operator found $14 million in benefits from enhancing the AGC. (FERC docket ER19-2619).
Jasmin Melvin is a reporter for S&P Global Platts. S&P Global Platts and S&P Global Market Intelligence are owned by S&P Global Inc.