Regular Member
Joined: 18/12/2020
Location: New ZealandPosts: 92
| Posted: 09:02am 02 Nov 2021 |
Some objectives of alternative energy systems at least for me include:
1) Reduce the grid cost as much as possible
2) Be able to run independently should the grid go down for an extended period
3) Get the most bang for my bucks.
4) Keep it legal if at all possible. Life is simple and easy with legal systems. (Sort of -Why do Australasian power standards have to be tighter and more expensive than the rest of the World? Surely CE, RoHS etc could have been good enough?!)
To my mind, when the grid is up, a grid tied inverter is the most efficient way to go, over the alternatives. Returns from selling excess power to the grid are pathetic, one is better to retain and use as much power as possible ones own green power in an efficient economic sense. Even if it means charging your battery from the mains drawing the excess green power (when excess is available to do that!)
Plainly a grid forming inverter is helpful when the grid is down (or not connected - storage capacities becomes a significant requirement in that case)
But show me a legal grid tied inverter for a wind turbine in Australasia....?
I have a 3 phase generator, expected to be good for 800W with power peaks well in excess of that. Currently it has the 3 wires exiting it. How to legally connect to a grid tied inverter in Australasia? One approach that has occurred to me is to use a multi channel solar micro-inverter that is certified to meet Australasian standards. They can take say four sets of 400W solar panels. So if I can match the power from each phase of the generator I can run 3 channels of the micro-inverter legally....and efficiently.
How to do that? I could maybe run 3 x isolating transformers, one on each phase, rectify / capacitate the 3 isolated DC outputs and feed each phase into 3 of the micro-inverters channels.... Probably need custom made transformers for that - with matching high current coils....
But then if the 3 phase coils can be separated within the generator with six leads coming out of the generator they will (it seems to me) already be isolated and avoid the transformer step just described.
Plainly the turbine needs to be speed managed when the power exceeds the micro-inverter draw, so dump loads needs to be flicked in and out when required.
I also think I read somewhere, but cannot find it now, that part of the NZS4777 standard includes the grid being able to turn off / reduce the power exported to the grid during times of excess generation over load to maintain grid power standards. (Does this ever happen in practice?) Plainly a turbine running full song needs a good dump load available to cover the grid turning the inverter off at its pleasure...!
Also sustainably switching AC is preferable to DC (Say 48V @ > 20 amps) so one can switch in dump loads on the AC side of things more cheaply than on the DC side with relatively standard relays. (Or some power electronics is desirable avoiding relays clicking)
If the grid goes down significantly the wind generator can be rewired to run into a controller / battery / gird forming inverter. The generator coils can be joined into the three wire config easy enough as a part of that.
Is this thinking missing something? Or is this a reasonable direction to run up?