An increasing number of Albertans are now aware of the risks associated with dependency on wind and solar generators. These naturally produce less power during periods of peak seasonal demand. (For example, Arctic winter storms.) Less well-known is another risk that is emerging as these intermittent generators become further integrated into our grids — loss of frequency control, caused by intermittent power generators — wind and solar — leading to blackouts.This is what happened in Spain last month, when a massive blackout struck the Iberian Peninsula, affecting Spain, Portugal, and parts of southern France. Around 55-60 million people were left without power, some for nearly a day. The failure began around 12:30 p.m. when Spain’s grid, heavily reliant on wind and solar generation, experienced a sudden loss of 13 gigawatts (GW) of solar power within five seconds.Could it happen in Canada?Yes. Alberta experienced similar circumstances last October, although we had a more fortunate outcome than Spain — on that occasion..First however, a technical note. What is 'frequency control' and why does it matter?Here in North America, electricity is defined as an alternating current that oscillates at a frequency of approximately 60 cycles per second or 60 Hertz. (In Europe, it is 50 Hz.) Mechanically, this frequency is maintained by the rotation rate in revolutions per minute of the turbines that drive the electromagnetic generators.Considering that some turbine generators weigh more than 100 tonnes and typically rotate at 3,600 rpm, it is easy to see just how much rotational energy these synchronous generators possess.When we consider that a large national grid can have hundreds of such synchronous units operating in unison, it makes sense to suggest the modern grid possesses frequency inertia. In other words, if a single generator is suddenly tripped or taken offline, there is sufficient inertia in the system to absorb and compensate until a back up generator is brought on line..However, the physics of all this change when we introduce wind or solar generators. These rely on solid state electronics or inverters to synthetically modulate the output frequency to match that of the grid to which they are connected.This works fine most of the time, but to date there is no large scale grid operating that way. That means we are literally running an experiment, by rapidly introducing intermittent or non-synchronous power sources to a grid largely defined by synchronous generators..So, what happened in Alberta?During late September through early October of 2024, there was a planned maintenance outage on the 500-kV Alberta-BC Intertie. (The intertia is the line through which electricity is transmitted back and forth between BC and Alberta, to accommodate fluctuating demands on either side of the border.)For most of this outage, we experienced very windy and sunny conditions. Combined with the fact that there is reduced demand during the fall season, a unique situation was created wherein solar and wind power were pushing the limits of being in excess relative to demand. Likewise, synchronous generators were going through their seasonal maintenance cycles in preparation for the high demand winter season, while others were being forced to ramp down in response to high winds and sunshine intensities.Now, a normally stable situation had become unstable. It was like being forced to pull over to the side of the highway to make way for your neighbour’s car, which is notorious for suddenly and uncontrollably accelerating or braking irrespective of highway speed limits..The large volumes of inverter-based resources online, combined with the loss of frequency support from the Western Interconnection due to the inertia outage, reduced the system’s mechanical inertia and degraded dynamic frequency response of the grid.As a result, Alberta’s grid experienced 27 frequency excursions due to generator trips and sudden changes in wind generation levels. And this was during a planned event!When I spoke with the Alberta Electric System Operator (AESO) about these excursions, they acknowledged that these were expected and manageable. Let's hope they're right. In any case, Albertans dodged that bullet and these frequency excursions did not result in system wide failure..Too bad for Spain though, when an unplanned event happened there. A month later, there is still no official explanation for why there was such a large sudden drop in solar power. But, it was this massive drop in solar output that destabilized the grid’s frequency.This rapid frequency change then caused a cascading failure, as grid equipment tripped to prevent damage, leading to a total system collapse. The disconnection of the Franco-Spanish transmission interconnection exacerbated the issue, isolating the Iberian grid from Europe.The grid’s low frequency inertia, due to high renewable penetration and the absence of synchronous generators like coal or nuclear plants, was a key factor. So was Spain’s aggressive renewable expansion — tripling solar capacity since 2018 — and closure of coal plants, that reduced the grid’s ability to handle sudden disturbances.Hydroelectric facilities were no help. Used for balancing, they were at their regulation limit. No back up gas plants were readily available. The Spanish grid operator, Red Eléctrica Española (REE,) ruled out cyberattacks or weather as causes, pointing to generation disconnections and grid management issues..These situations are not irrecoverable; power restoration began within hours, with 99% of the peninsula reconnected by April 29, though full recovery took nearly 24 hours. But who needs the aggravation?After all, the blackout disrupted transport, businesses and hospitals. Eight people died as a consequence.The Spanish government, led by Prime Minister Pedro Sánchez, and REE declined to admit that renewables directly caused the outage... they did however acknowledge grid vulnerabilities.The Spanish market regulator, CNMC, had previously warned of voltage oscillations due to high renewable integration and low demand, a concern echoed by REE in February 2025. Since April 28th, REE has implemented policy directives that have resulted in more curtailment of solar PV and wind during peak generation periods in favor of synchronous power sources such as hydroelectric, natural gas and nuclear.Adopting this practice speaks volumes, for it shows that REE recognizes that inverter based power sources do not produce the same frequency stabilizing effect as turbine based power generation..The Spanish experience is something for Albertans to be aware of. While AESO down-played the Iberian blackout on the basis that Alberta has far less inverter-based resources connected to the grid as a percentage than does the Iberian grid, it is the direction that Alberta has been moving on.I will note that the Alberta Utility Commission (AUC) and AESO approved a record level of solar PV infrastructure in 2024. .In fact, when we look at AESO’s forward looking assessment of inverter based resource capacity (27,700 MW) relative to the 2-year average Alberta load on the grid (10,300 MW) there is every indication that Alberta’s grid is well on its way to becoming a near replica of the Iberian grid, with much more inverter-based power generation than synchronous gas power generation according to AESO’s current projection.Why are we doing this?
