How does domestically-generated electricity reach the grid?

[chakka35]

Solar panels produce d.c. Where and how is that converted to 50Hz a.c.?

Assuming that wind turbines have alternators to produce a.c. how is the output maintained at 50Hz regardless of the speed of rotation? Or are various conversions done at a central base? What is the electrical connection between the house and the central base, the ordinary mains circuit?

[Teddio]

An invertor is used to convert the low voltage dc inputt to a high voltage ac output. The frequency and phase must be matched to the grid's. The frequency of the National Grid isn't necessarily 50Hz, it typically varies between 49 and 51Hz.

[chakka35]

Zacmaster, I'm talking about that surplus electricity that, we're told, home producers can sell back to the grid.

Yes, Teddio, that's what must happen. What I'd like to know is..how? Is the conversion done in the home? Presumably not, because there would be no information about phase and exact frequency available there. So is the raw output sent to some base for processing? If so, how? You can hardly send d.c. back down the main.

There must be someone out there who is actually doing this. If so, please explain.

[Clanad]

At least here in the western U.S. (I assume the same standards apply in most countries using turbine supplied electricity), the electricity from the turbine (or multiple turbines in the case of a farm) is routed to a local collection device rather like a mini-grid, where the "raw" current is stabilized and "standardized" by transformers before being fed to the national (or area) grid. The newer generation of turbines are equipped with internal solid-state converters between the turbine generator and the local collector system to assist in a stable voltage before being sent to the local collector system.
I've a friend that's an engineer for two of the local co-op farms near our place in the western U.S., and we discussed this very item not long ago. (Small world,no?)
There are many old, abandoned wind-mill powered generators on homesteads around here.. They, of course only supplied electricity to the homeowner (rural) and stored the wind-mill powered electricity in a large bank of truck batteries at the base of the mill. This was fed to the house from the battery bank and was fairly stable for its era (mid-1930's).
It was 12 volt and I still have an old catalog where 12 volt appliances, ranging from irons to refrigerators could be purchased using that voltage...

[mibn2cweus]

http://wapedia.mobi/en/Grid_tie_inverter

voltage feedback determines current input

http://www.electro-te...ion-block-circuit.png

[BillyBB]

There is an estate near here where all the houses got solar panels from new. They have an exciter feed from the main meter to ensure the home made AC is synchronised and a special meter set up that monitors those times when it back feeds the grid. Even with the special rates enforced by government policy it will still be many years before the savings meet the initial investment.

[beso]

The grid frequency is actually very stable.

Many large wind turbines operate at relatively constant speed and become less efficient as the wind speed rises. This is what is required anyway since a stable ouput is more useful than great surges in energy that could easily cause damage. In fact during lulls the turbines are often driven by the grid. With wind the ability to not be efficient when the wind gets too high is fundamental to the art.

As power electronics advances it is becoming increasingly attractive to build an inverter.

Solar generation is now working mainly with high DC voltages fed into inverters. A similar concept can be used in wind farms. The DC is an easy common interface to work with and keeping all the electronics at the farm gate is very efficient becuse it allows for one large unit. DC also allows efficient transmission under seawater where many wind farms are located.