Blackouts in grids with high penetration of inverter-based renewables (IBRs) raise a challenge for renewable energy because of degradation of system strength. Rightly or wrongly all renewables are “tarred with the same brush” in spite of the fact that hydro-power, biofueled stations, solar thermal power and Type 5 wind power are all renewables which have synchronous generators, and thus are not IBRs.

The South Australian blackout of 2016 and the Spanish blackout of 2025 are two examples which had very different mixes of IBRs and synchronous generators on-line and very different root causes. However, in both cases the majority of load was being met by IBRs, and the grid was presented with a sequence of stability challenges which included:

1. Voltage fluctuations initially
2. Local disconnections followed by some successful and unsuccessful attempts at reclosure
3. A final stage of widespread, rapid voltage and frequency collapse.

This sequence of events follows from a hierarchy of characteristics that the system needs to remain stable. In other words:

1. if voltage fluctuations can be managed robustly, disconnections are less likely and in turn,
2. if reclosures after disconnections can also be managed robustly,
3. the frequency collapse that marks an actual blackout can be avoided.

In the South Australia blackout some IBR wind farms failed to manage a series of voltage fluctuations robustly, whereas in Spain the synchronous generators on the system and other non-IBR elements collectively failed in this respect, partly because they were minor contributors to the real and reactive loads at the time.

This paper examines the Spanish blackout, using data from the March 2026 Final Report by the ENTSO-E ICS Incident Investigation Expert Panel, to answer how Type 5 wind turbines could have contributed if they had been on the grid. Our examination is prompted by the observation that, at the time of the blackout, wind power was much lower than solar PV generation in Spain. A synergy would arise because reactive power capability of Type 5 wind turbines increases when their real power output falls. Thus, in the conditions of the Spanish blackout, Type 5 wind turbines would have had close to their maximum reactive power capability available for voltage regulation. This paper concludes that the large scale of wind power in Spain would, if capable of voltage regulation, have reinforced the small number of synchronous generators on the system to achieve the voltage control which was lacking on the day. The converse situation would apply on a windy night if solar PV inverters were able to export or import reactive power.

The paper concludes with a discussion of a further, related synergy between wind and solar PV power. This relates to the ability of solar PV with grid-forming inverters to manage robustly events of disconnection followed by attempted reclosure, whereas wind turbines with grid-forming inverters are very intolerant of even small phase jumps. However Type 5 wind turbines are phase-jump tolerant. Together with grid-forming IBR solar PV, they underpin a robust pathway to renewable grid stability.