Most of these problems can be improved through a combination of software and policy changes, and the report makes some suggestions along those lines.
The inertia provided by generators with a lot of spinning metal (think hydroelectric or natural gas turbines) is generally thought to improve grid stability, but this analysis suggests that even tripling the amount of inertia would have only damped system oscillations by about 3 percent. So it’s not clear that having more traditional online power would have helped.
That said, there is one area where potential problems were clearly mapped to one form of renewable generation: rooftop solar. The problem there is less that the hardware was not following policy and more that no actual policy is being followed. Red Eléctrica, the Spanish grid operator, estimates that it has around 6.5 GW of small-scale solar power (< 1 MW) on the grid, with 75 percent (4.9 GW) connected to low-voltage networks at the consumer level. The committee obtained data from two inverter manufacturers, which together track the performance of about 15 percent of that capacity.
This data shows that a substantial fraction (more than 12 percent) of a manufacturer’s hardware was disconnected from the network during the first few oscillations and reconnected a few minutes later. Shortly after, more than 20 percent went offline again during the voltage spike that occurred about two minutes before the blackout. By contrast, the fraction of second-party hardware that left the network never exceeded 10 percent.
All of this suggests that small-scale generation could have seen hundreds of megawatts of production drop and return to the grid in the minutes before the blackout, and that the exact figures depend largely on inverter manufacturers, with the grid operator having a limited window to know its actual behavior. This is a case where further regulation is probably necessary.
Put learning into practice
The report is encouraging because it identifies numerous solutions that should be fairly easy to implement, including greater automation of shunt reactors, wider safety margins between alarms and shutdowns, and better alignment between network policies and hardware behavior. And it does not appear to identify any critical issues that require a rethinking of Spain’s approach to bringing its network to net zero emissions.
The economy is also likely to help the situation. Spain currently has little battery capacity, which can perform multiple functions to stabilize the grid. But the continued growth of renewables will increasingly lead to the overproduction that makes batteries economically viable.
The biggest question seems to be how quickly Spain can implement some of the report’s recommendations.
