Great River Energy is urging MISO to account for the effects of inverter-based generation in the RTO’s transmission planning studies.
Inverter-based generation — often new technology resources asynchronously connected to the grid via an electronic interface — can harm reliability in weak power systems, Great River Energy’s Mike Steckelberg said at an Aug. 15 MISO Planning Subcommittee meeting. The Minnesota utility discovered the issue during a recent analysis, he said.
Steckelberg cited a June NERC report warning that such resources can affect dispatch and reliability — including voltage control, frequency response and ramping — when too many of them are interconnected into weak power systems.
The company said MISO’s annual Transmission Expansion Plan study process should include screening for transmission with low short-circuit currents, comparing the megavolt-ampere level before a inverter-based resource is connected to the nominal power rating of that resource. If the calculation does not meet a certain threshold, MISO should remedy the transmission by modifying controls, connecting to a stronger source, planning for more transmission or reducing the size of the generation project.
“This is a fairly easy screen to be doing ahead of time,” Steckelberg said. While the screen would not have to be a “full-blown study,” it does need to be incorporated into MISO’s generation interconnection studies.
Steckelberg said MISO’s Interconnection Process Task Force and Planning Subcommittee both need to address the issue, and transmission owners and planners should be able to review new interconnection requests for low short-circuit current issues.
Entergy’s Yarrow Etheredge and American Transmission Co.’s Patrick Gerum said their companies shared GRE’s concerns.
Customized Energy Solutions’ Ginger Hodge asked for MISO’s response on the issue.
MISO Director of Planning Jeff Webb said he and his staff would review the request and put together a response at the Planning Subcommittee’s next meeting in October.
— Amanda Durish Cook
