Energy Transition Challenge 2: System Stability
Stable vs. Unstable System
However, if the load surpasses the combined generation capacity of the system or the fault is not cleared fast enough, some generators start slowing down and operating at a lower frequency than others.
This places additional electrical and mechanical strains on the system as a whole. All components are no longer operating at the same frequency (or in synchronism) and the system becomes unstable.
In order to prevent damage to components throughout the system, additional measures have to be taken. This typically involves the operation of backup protections or measures to reduce the load. This has the intent to bring the system back into a stable condition.
If the system is not controlled in time, it can lead to a large system black-out. These events tend to have devastating consequences for the community and the economy as a whole.
The "low inertia" of renewables
Now, what does all this have to do with the energy transformation?
Well, as it turns out, some renewable sources of energy such as solar and wind, do not have the same mechanical inertia than the large rotating generating machines.
This means that systems that source their energy from these types of renewables in large proportion, tend to be more vulnerable to instability caused by large faults or sudden increases in load.
Another peculiarity of system with this mix is that whilst load might not suddenly increase, the generating capacity could drop relatively quickly if the solar irradiation reduces quickly. This happens when large clouds pass over the solar panels producing all this power.
What can be done?
All these challenges are well known to system and market operators around the world.
Depending on various factors such as the specific mix of generation sources, the state of the local economy or the particular goals of the political jurisdiction, there are various countermeasures that are being devised and implemented across the globe.
Amongst others, these solutions include:
Management of reserve generation capacity
This is a good video talking about the effects of large power outages