Three recent Alberta power system events illustrate the growing challenges our system is having in response to disturbances: June 7, 2020, October 16, 2020, and February 21/22, 2021. The changes in Alberta’s power system characteristics with increasing inverter-based resources (wind, solar, storage) and retiring/diminishing synchronous resources have resulted in a system that has become less resilient to disturbances and increasingly “brittle”. These system events are a preview to future, more significant events if improvements are not implemented soon. Below is a link to an analysis of these three events that was published by the AESO in March 2021 for those who wish to learn more.
In addition to the complexity being introduced by inverter-based resources (wind, solar, storage), Alberta has some unique characteristics relative to other grids that increase its complexity and require special consideration for planning and operations:
- Alberta is very weakly interconnected to other power systems, with only one major intertie to BC, a small intertie with Montana to the south, and a back-to-back HVDC connection to Saskatchewan. The BC intertie does not have a shield wire, making it susceptible to lightning strikes and resulting in frequent trips which also trip the Montana intertie because the northern Montana system cannot handle the variability of the Alberta system. This means Alberta is often electrically islanded and it must be planned and operated to be reliable in that configuration. This differs significantly from almost all other jurisdictions that are strongly interconnected, such as California, which relies on interties to act as a “shock absorber” to recover from system disturbances. Look no further than the Western Energy Imbalance Market for a great example of how multiple strongly interconnected jurisdictions are helping each other integrate increasing levels of renewable energy. We don’t have that luxury in Alberta and the BC intertie actually becomes a risk to manage instead of a tool to rely on in some instances.
- Alberta has two 500 kV HVDC lines embedded within its AC system. This leads to unique operational characteristics and challenges that must be considered as system inertia and short-circuit levels change with the addition of inverter-based resources.
The unique complexity of Alberta’s power system makes it imperative that policy makers understand the impacts that green energy and net zero policies are having on our system. These impacts must be considered so that reliability is a non-negotiable policy objective to ensure the pace of change on the system is controlled and coordinated and the AESO can continue providing the operational reliability and resilience that underpin Alberta’s economic well being as the grid evolves.
AESO Learnings and Actions in Response to Recent System Events