As inverter-based resources like wind turbines, solar photovoltaic, and battery energy storage systems are introduced to the grid, the associated risks are becoming more apparent.
The North American Electric Reliability Corporation (NERC), in conjunction with the Western Electricity Coordinating Council (WECC), recently released its 2022 California Battery Energy Storage System Disturbances report, which highlights two examples of unexpected, abnormal performance of bulk power system (BPS)-connected battery energy storage systems initiated by normally cleared faults in the Western Interconnection that occurred on March 9 and April 6 in 2022.
These instances were the first “significant” events involving battery storage systems, NERC said.
“These events are the first faint signal that the systemic performance issues we have identified with other inverter-based technologies may very likely apply here as well,” said Ryan Quint, NERC’s director of Engineering and Security Integration. “Battery energy storage systems will play a critical role during the energy transition; therefore, it is imperative that we design, study, commission, and operate them in a manner that supports BPS reliability.”
NERC found that battery energy storage systems may have the same systemic performance problems
as solar photovoltaic resources, and battery energy storage system ride-through performance is not adequately assessed during the interconnection process. Additionally, poor commissioning practices are a significant contributor to the unreliable performance of inverter-based resources.
The lack of adequate monitoring hinders performance and event analysis, NERC found.
Recommendations for generator owners
NERC recommends that all generator owners check with their inverter manufacturer to ensure that their inverters are not prone to tripping on the following causes, in addition to those previously reported, during normally cleared unbalanced grid faults:
- Unexpected, unbalanced AC current
- Unexpected DC bus overvoltage tripping
- Unstable DC bus voltage
NERC says all Generator Owners should ensure both inverter- and plant-level recording functions are configured to meet the requirements in the interconnection agreements. Additionally, Generator Owners should ensure fast logging is enabled and that meter data does not freeze on the last value when subjected to system transients during grid faults.
NERC and WECC encourage the industry to take timely action to implement the recommendations in this disturbance report as well as those from past disturbance reports and related NERC reliability guidelines. The ERO Enterprise, made up of NERC and the six Regional Entities, will continue to analyze disturbances that involve widespread reductions of inverter-based resources to identify any reliability issues, support affected facilities in developing mitigating measures, and share key findings and recommendations with the industry for increased awareness and action.
The full report can be read here.
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