grid tie sync to off-grid inverter

R

rtgunner

Member
Joined
Jan 14, 2018
Messages
101
I wonder if it is possible to integrate a grid tie only inverter into an off grid system.

If the off grid inverter is a true sine wave inverter servicing
ac loads would the grid tie inverter look at this as "the grid" and just sync up to the wave form
and be happy?

I did a quick search and didn't get to any resounding results.

I would think it is possible as the power company grid varies quite a bit
as more loads come on and off the system - the grid tie inverter has to adjust to these variances
when "on grid."


Anyone tried this?
 
Nope, not really. It requires AC supplied so that it can match the frequency. If there's not AC on the Hot side, it won't power on as there's nothing for it to sync to.

You could use another inverter that's like 300W pure sine to generate the signal first, but not sure how well that'd work. Might end up blowing that one up, though
 
I didn't maybe explain myself well...


So, Hypothetical:

first system - Battery bank charged by solar panels and solar charge controller
Pure sine wave inverter using only battery power that is always on (I have a few phantom loads like my radon fan)

second system - another set of PV connected to a grid-tie pure sine wave grid tie inverter (no battery charging)

connect the grid tie side of the second system inverter to the AC loads that are being powered by the battery inverter system.

Shoulden't the grid-tie system sync to the always on pure sine wave provided by first system and thus add ac production to the loads?
 
I do believe that is exactly what I said in the 2nd sentence.

Korishan said:
You could use another inverter that's like 300W pure sine to generate the signal first, but not sure how well that'd work. Might end up blowing that one up, though
Click to expand...
 
Why would it blow up the first inverter? if it is a bi directional inverter it should be good to go no?
 
rtgunner said:
Why would it blow up the first inverter? if it is a bi directional inverter it should be good to go no?
Click to expand...

Your stand alone inverter probably will not handle being back fed by the grid tie inverter.
 
I belive Victrons Multi Plus inverter chargers can do this. In absnse of grid the Multi's will create a local grid which the gridtie inverter wil recognice and keep running and feeding in solar til the house and to the batteries. Problem arises, when PV production is bigger than demand from loads and batteries are full.
 
With a UPS (or most off grid inverters) as the AC source and load connected and then the grid tied plugged in with less generation than the load it would work. BUT....

Veyr, very big warning.... when the load attached to the system drops below the grid tied output the grid tied unit will ramp up the output voltage and try back feeding the UPS. The back feeding works by raising the voltage through the waveform and the lack of a load to pull the voltage down through the cycle will result in a + to - switch with full voltage, which promptly blows all the MOS units.
 
A normal grid-tie cannot and should not be used without a grid behind it that it can back feed to... With that said you have the hybrid version that is able to as DK100 do run its own system or even run grid + load. I run hybrid so my system have a load output that I can switch to.

There is also people that have gotten some smaller grid-tie inverters to work with a normal inverter at same time but its not recommended AT all. If you ask the question you should not fiddle with it is my recommendation. Unless you want to do a video about things blowing up :p
 
You must log in or register to reply here.
Back
Top