Read and weep – Review of market frameworks for power system security 14 July 2016 – No mention of “Elephant in the Room” sky-rocketing AEMO Regional Reference Prices in South Australia, Vic, NSW & Qld.
Quotes in italics –
Challenges in maintaining power system security are emerging because of the physics of maintaining technical generation parameters like voltage and grid frequency. And this was not predicted?
Conventional electricity generation, like hydro, coal and gas, operate with large spinning turbines that are synchronised to the frequency of the grid. These generators support the stability of the power system by working together to maintain a consistent operating frequency. And no electrical engineer told you this before the Grid was infested with wind turbines?
Less conventional forms of electricity generators, such as wind and rooftop solar, are not synchronised to the grid and are therefore limited in their ability to dampen rapid changes in frequency or respond to sudden large changes in electricity supply or consumption. This is no surprise to electrical engineers.
Why not sack the useless AEMC – get some engineers in to chart the future of the grid – wind back the uptake of subsidised renewables – make sure any future renewables pay their own way including the full cost of the grid coping with their production.
I’ve been wondering how they synch wind and solar to the grid AC cycle.
It appears they are not, which makes their inputs worse than useless.
Maybe Tony could enlighten us.
I heard a suggestion from an electrical engineer that wind and solar should output DC, that they build their own high voltage DC grid for distributing to whoever wants their `green’ product, and that they leave the HVAC grid to the pros.
Non-synchronous and non-dispatchable! Whoever would have guessed it? And bear in mind we are talking about less than 10% penetration of renewables at present (often MUCH less). How do we manage to get to 20%? 30%? 50%? One suspects it will involve having lots of “spinning reserve” on hand burning fossil fuels and emitting CO2. It would be interesting to know what the REAL contribution of renewables is to emissions reduction.
I think the grid connect solar are phase synced with the grid by sampling the power from the grid. However to feed into the grid the output from the grid connect inverters has to be higher than the standard grid voltage, so immediately there is potential instability.
The output of a grid connect inverter is not the clean, pure sine wave that you get from a good quality DC to AC inverter that you would use in a stand alone solar power system. The output of grid connect has harmonics up into the Khz range.
None of this was predicted Warwick because of course it was/is not "the vibe". An appropriate analogy is to think of a farmer selling off his draught horses then attempting to plough his paddock with 1500 uncooperative cats harnessed to his plough.
Some of the problems of operating the "hippy grid" are touched on in an interview with Electrical Engineer Andrew Dodson, available here, by Scott Medwid and Rick Maltese on the subject of grid stability, and the impact of "green energy".
Philip Bradley:
For a wind turbine to start generating it has to have grid power available, firstly to drive the yaw motor which turns the nacelle into the wind, and for the blade motors which set the right blade angle for the wind speed. That means the computer controller has the voltage and phase angle available. Certainly it has to set the right phase angle or the turbine winds up as a giant electric fan.