How does a grid solar inverter get power to flow to the grid?
I seem to get condradictory results in web searches. Some sources say the inverter only matches the grid voltage, while others say the inverter puts out a slighty higher synchronised voltage. If it just matches...than I gather to low resistance of the grid will allow current to sourced out? Appreciate any enlightment
SOLAR 2000 Watt Power Inverter
 | US $298.99 End Date: Wednesday May-23-2012 22:39:36 PDT Buy It Now for only: US $298.99 Buy it now | Add to watch list |
Fronius IG 4000 Grid Tie Solar Power Inverter
 | US $2,400.00 (0 Bid) End Date: Wednesday May-23-2012 22:45:10 PDT Bid now | Add to watch list |
A basic inverter converts DC into 120 VAC. The DC may come from batteries charged by a Solar panel or directly from a Solar Panel (during the day).
A more sophisticated Grid tie inverter will match the AC sine wave being produced by the inverter circuit with the sine wave of the line power being produced by the power company.
This is called synchronization, the matching of power sine waves being generated so that they may be electrically connected together.
As the home uses electricity its needs will be met by power being supplied by the power company or from what ever power is available from the solar system via the inverter.
If more power is being producd by the solar system than what is required. The excess is either stored in batteries OR is allowed to flow back onto the power line. If you can send power “back to the power company” (the grid) your electric meter will run backwards (Net metering) giving you credit for the power you are supplying to the grid.
If you need more power than what you generate then your electric meter would run slower because you are not using all of that power from the grid, you are generating some of the power so your electric meter only needs to pass the electricity to make up the difference .
Yes. Most of them simply monitor the current flow (‘in’ or ‘out’) and adjust the delivered voltage (to the grid) so that the current flow is ‘out’ onto the grid.
Doug
Mark has given you a pretty good explanation; however it is a bit more complex than that!
1most inverters do not produce a sine wave with acceptable distortion to be compatible with the grid.
Why would you want to do this?
The parameters of cost vary greatly over the planet. For example in Quebec Canada, the cost of electricity is low, so people leave lights ON all day long.
In Paris, the cost of electricity is so high that people buy timers (about $30) to tour OFF the lights in the stairway after just a few seconds.
To help you understand the complexity, imagine a car with an engine driving only one wheel.
You want to add another engine of a different rating and different parameters to add power to another wheel.
I am sure you can understand the car would anything but go straight, especially when slipping.
If you tell me why you want to do this I can explain more precisely.
The inverter has to produce more voltage than the grid it is connected to in order to push power into that grid. The grid has a very low impedance, so a very small excess voltage can deliver a lot of power.
For instance, if the impedance of the grid is 0.05 ohms (10 volts of sag with a 200 amp load) on a 120 volt circuit, then if the inverter current forces that line voltage up from 120 volts to 121 volts, it would take 1V/0.05ohm=20 amperes of output current and the delivered power would be 21A*120V=2520 watts.
–
Regards,
John Popelish
You need a “Transfer Switch”.
You can use this system to power up basically any appliance you have in your home: fridge, washing machine, computer, TVs, lights.
Moreover, you can even take this with yourself when you go camping, because it’s highly portable.