There were a number of issues at work during last year's system collapse in South Australia.
For a concise but highly informative discussion about this, the latest issue of Australasian Transmission and Distribution has reprinted a summary from the University of Queensland's Chair of Electrical Engineering. Contributing to this power blackout were the stability issues that a high proportion of distributed generation introduces.
Photovoltaic cells and wind turbines do not have the ability to respond correctly to abnormal system voltages. The South Australian system voltage surged after the Heywoods Feeder tripped off. That in turn caused four out of the five base load units in South Australia to trip off on overvoltage. Following this, massive load shedding had to take place to maintain system frequency. More than just the weather was at work here, despite what Malcolm Turnbull is quoted as saying.
Having been much involved in the commissioning of base load generation, I can vouch for the intense efforts that go into fine-tuning the turbine / generator controls so that these can react to correct system disturbances ( whether of voltage or frequency). These commissioning and post-commissioning tests can go on for many months afterwards, before the results are deemed as being satisfactory. Distributed (or "embedded") generation simply does not have that ability.
At the Electricity Engineers Association conference that I attended last June, this issue was raised a number of times. Not only was concern expressed about lack of sufficient corrective response from embedded generation, but also the difficulty in then putting the system back together afterwards. ("Islanding" is the term electrical engineers use for this situation, and from experience, I know that it can be a difficulty even in a small power system). When everything was owned and operated by one entity (which in the case of South Australia was ETSA), that was quite straightforward. It isn't anymore, and this introduces major delays in power restoration.
A stable electricity grid is still required - if anything, more so now. Not surprisingly, power system operators dread a system collapse, like South Australia recently experienced.
You can also have gas powered plants to pick up any slack. T
That still requires a stable grid - as do wind turbines.
Once again, the latest issue of Australasian Transmission and Distribution features a very informed discussion about what happened last year in South Australia.