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How load sharing can be done in ac mains and inverter?


Arijeet
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Question- There's a question to which I've been looking for an answer but I haven't found a clear one yet so I hope this forum will help.
How is the load shared between a grid-tie inverter and the grid? I understand that the inverter feeds the loads with all the available solar power and imports the remaining balance from the grid if needed or exports the excess if any. I would like to understand the technical details behind this process (how does the inverter have feeding priority over the grid?) because so far I haven't found a clear explanation online.

Objective to ask this question -In the above line, many experts will not understand the question, so I am just explaining a simple example below:- Suppose we need to drive a load of 10 kW( load can anything or mostly all the loads are combined to form the 10 KW) in our household. But in my area, the utility sector provides only 5 KW to drive the load. but if I go above beyond this we need to pay for this extra.but in my home I have an inverter (inverter can be any type may be a solar or conventional system with battery) which is rated of 6KW, so why we will purchase extra energy from the utility sector if we have an inverter. so what we will do we want to share the power or bypass the load, in simple terms if we set the limit of ac mains to 4KW and after beyond going to 4Kw my power will be shared by the inverter which will 6 KW. Now this power distribution will be done by the microcontroller and some hardware apparatus (e.g.IC's, gates).

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Let me try to answer this: A grid tie inverter synchronises it's supply to the mains. So they will be in phase with each other. (So if these are connected to each other then there will be little or no current that will flow between them)

The PV panels are used to power the inverter and this will produce AC voltage which is used to feed the loads in your house. If there isn't enough power from the PV panels the AC supply voltage will drop and there will then be a voltage difference between the grid and the inverter. The inverter control system will detect this and feed power in from the grid to assist the inverter.

Likewise if there is a higher output voltage produced by the inverter from the PV panels this will be detected and the controller will connect this to the grid allowing the power to be fed into the grid.

These grid tie inverters are smart devices, way smarter than a regular off grid solar inverter!

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7 hours ago, FixAMess said:

So the inverter "controls" / manipulates the voltage its producing to feed the loads?

Some do, some are much simpler and just pour everything that they can generate into the AC output (unless that would result in too high a voltage). If your utility doesn't want you exporting power, then the inverter might try to limit its output so that this rarely happens.

You can think of it as conservation of energy/power: with 10 kW going out, and say 5.5 kW from the inverter, then the remaining 4.5 kW has to come from somewhere; this will be from the grid.

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I glad to happy that expertise got my question.sir i want to this implement this method.Actually in my country smart inverters has now to start be manufactured but it very costly to purchase for normal people. companies are manipulating to the consumers that their smart inverters have this type of inbuilt function.well i am research engineer under the power utility supervision , so my team said to me built this type of controller who controls the load sharing between and grid tie on and inverter for the load. but i am stuck where should i start. i just need to know how i can built controller part, i don't need any exact answer just need to know the methods and research papers which may be you all expertise can provide me in this platform. i request please share your reviews on the same.

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"Let me try to answer this: A grid tie inverter synchronises it's supply to the mains. So they will be in phase with each other. (So if these are connected to each other then there will be little or no current that will flow between them)

The PV panels are used to power the inverter and this will produce AC voltage which is used to feed the loads in your house. If there isn't enough power from the PV panels the AC supply voltage will drop and there will then be a voltage difference between the grid and the inverter. The inverter control system will detect this and feed power in from the grid to assist the inverter.

Likewise if there is a higher output voltage produced by the inverter from the PV panels this will be detected and the controller will connect this to the grid allowing the power to be fed into the grid.

These grid tie inverters are smart devices, way smarter than a regular off grid solar inverter!"

Sir what you have said ,it is true, but what i want to do drive the load from the inverter when grid supply is also available ,grid is disconnected with power supply , its just we are trying to minimizing the power and taking power from the inverter which is already stored before in the battery or from solar panel.so i just want reverse the process of controller part but i need to study about the controller part which is inbuilt with smart inverter.Hope you will understand.

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13 hours ago, FixAMess said:

So the inverter "controls" / manipulates the voltage its producing to feed the loads?

 

Yes. If you think of a regular inverter it will draw power from the battery to produce mains voltage. If you overload it the inverter will trip (hopefully)

A grid tie inverter has another 'battery' in the form of the grid. When the load gets too great it seamlessly starts adding grid power to the mix. As mentioned it is in step with the grid so this is possible without transients etc.

What I find quite puzzling is why the info (on its display or available on a data connection) of how much power is being drawn from/fed back to the grid isn't easy to see. The inverter is controlling this. So when you're looking at the inverter providing power you can't determine where it's getting it's power from. :(

 

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2 hours ago, Richard Mackay said:

What I find quite puzzling is why the info (on its display or available on a data connection) of how much power is being drawn from/fed back to the grid isn't easy to see. The inverter is controlling this. So when you're looking at the inverter providing power you can't determine where it's getting it's power from. :(

 

Which inverter doesn't show this information. 

 

My hybrid sunsynk inverter shows exactly where power is coming from or going to. 

First pic shows pv generation, loads supplied by the inverter, battery power and grid power. 

Second pic is from their app and the direction changes depending on where power is going or coming from. 

Screenshot_20201004-130901_Photos.jpg

LiveMessage_2020-08-16-17-45-14.gif

Edited by Achmat
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