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NERC Issues Recommendations Regarding Faults of Grid-Connected Solar Generation

Problems with inverter-based resources, such as solar and wind generation and battery storage systems, could result in “systemic performance issues” that could lead to “potential widespread outages if they persist,” the North American Electric Reliability Corporation, said in a November 30 report.

The report, Inverter-Based Resource Performance Issues, Findings from the Level 2 Alert, makes public the findings that came out of a Level 2 alert NERC issued in March.

The alert required generation owners of bulk power system connected solar photovoltaic facilities to provide site-specific data. The March alert also gave “strong” recommendations for those photovoltaic generator owners to improve the performance of their resources.

The March alert was issued in the wake of what NERC called numerous events that showed “strong evidence of systemic deficiencies in the performance of inverter-based resources” during grid events, including deficiencies in modeling and study accuracy of IBR integration and performance. The performance deficiencies appear to be of greatest risk in bulk power system connected solar photovoltaic resources, NERC said.

In September, NERC reiterated the need to address solar power system faults, and in October the Federal Energy Regulatory Commission, in Order 901, directed NERC to develop a suite of new or modified reliability standards to address inverter-based resources data sharing, model validation, planning and operational studies, and performance requirements.

NERC analyzed the data collected as a result of the March alert and released the following key findings:

  • Many generator owners indicated that they did not have the requested facility data readily available.
  • About one-quarter of the grid-connected IBR facilities use synchronization protection mechanisms that results in an increased likelihood of inadvertent tripping during normally cleared grid faults.
  • About one-quarter of the reported facilities use a fault ride-through mode that does not adequately support bulk power system reliability.
  • About one-third of the reported facilities have a significant amount of underused reactive power capability.

The November 30 report also included crucial recommendations that NERC said, “should be addressed in a timely manner.”

  • NERC said it plans to develop a standard authorization request for enhancements to support uniform IBR performance requirements established by transmission owners.
  • NERC also said it should consider proposing commissioning requirements for generator owners of IBRs.
  • NERC said it would develop two Reliability Standard Projects to produce performance and post-disturbance analytical expectations to address systemic IBR performance issues and support a more reliable IBR fleet. NERC said both projects are considered “high priority given the recent FERC Order No. 901.”
  • NERC also said it will issue a Level 2 alert in early 2024 to gather modeling and study information from generator owners and transmission providers regarding modeling and study enhancements and to gather data to assess the extent of condition of possible modeling and study risks.

“The findings in this report demonstrate that potential reliability gaps exist when those recommended practices are not implemented,” Ryan Quint, director of engineering and security integration at NERC, said in a statement regarding the November 30 alert.

Both the upcoming Level 2 alert on modeling and study practices and the current alert will inform the contents of a Level 3 alert, providing essential actions for high-risk IBR Issues that is slated to be issued in the first half of 2024, NERC said.

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