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[moved] Grid tie inverter problem

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electrochamp

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Hello,
i am working on a project of grid tie inverter and there are some problem related to that,
1) For sampling mains sine wave i am using voltage divider from 220V to 2.5vpp is this a good approach or transformer and then vdr will be mor handsome approach? Plz clarify the drawback in first approach..
2)For testing purpose i used an auto-transformer and rectify it to 290VDC which is provided to the drain of Bridge inverter. Is this a correct approach ?or there will be a problem due to common ground of both inverter and control circuit.

Thanks alot
 

1) Resistive dividers will always be the most accurate way to sample a higher voltage. Its only drawback is the lack of isolation.
A transformer does provide isolation, it must be designed with a winding resistance and a flux density lower than what you would expect on a "normal" application for power supply use.
 
here is ltspice simulation of circuit grid tie inverter, ltspice is free.

You do not need to always sense the mains, you just have to know when is the zero crossing, then you shovel in your sinusoidal current in phase with it.

You need to have a dc supply of voltage higher than the mains peak, so that you can always shovel power into the mains via the inverter....so whatever gives you that HVDC supply, it needs to be isolated...ie, its input must be isolated from the mains.....as you know, its output is not isolated from the mains because it feeds current into the mains directly.
 

Attachments

  • GTI _Open Loop_2.txt
    15.8 KB · Views: 53
Thanks schmitt trigger, if i didnt provide isolation between ac mains and control circuitry i-e i am just using Vdr then what will be the Possible problem?

I did not understand the purpose of isolation what will be the problems if they are not isolated?
 

Thanks Treez,
actually i am trying to control power by phase angle and i need to do continuous sampling. yes i will use dc supply greater than the peak value of mains but problem is that how to isolate their grounds? dc supply is connected to the same mains. and if i use battery and then boost my problem will be resolved?
 

use the isolation of your transformer of your power supply which you use to get the dc with
 

use the isolation of your transformer of your power supply which you use to get the dc with

Actually when i connected drain of inverter from autotransformer followed by rectifier my circuit blown off:bang:...... is this because of common ground between control circuit and inverter(autotransformer).??
 

here is ltspice simulation of circuit grid tie inverter, ltspice is free.

You do not need to always sense the mains, you just have to know when is the zero crossing, then you shovel in your sinusoidal current in phase with it.

You need to have a dc supply of voltage higher than the mains peak, so that you can always shovel power into the mains via the inverter....so whatever gives you that HVDC supply, it needs to be isolated...ie, its input must be isolated from the mains.....as you know, its output is not isolated from the mains because it feeds current into the mains directly.
Hi Freez, a small question about the added file (GTI_open_Loop_2.txt): I can not find the synchronisation between the grid and the inverter output, can you indicate the components responsible for this? Thanks in advance
 

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