Grid Tied System With Limiter and Battery Backup



This is my version of grid-tied with battery backup system. This is just basically a grid-tie + off grid system combined.  My main purpose of  the grid tie inverter is to cut down my electricity bill and off-grid inverter to give me an uninterruptible power supply for my SMS servers at home.  Nowadays,  you can simply buy single inverter or what we called hybrid inverter and you will have grid-tied and off grid inverter instantly in one box. But this is not the case with me since I started  to build Off grid system, then later expanded to grid-tied system. I do not have a choice but to use the existing  equipment I have. 🙂  If you have the time, build a system like this on your own instead of buying a ready made hybrid inverter because this is far more exciting to install than the ready made ones.  🙂



This is what it looks like in the real world .




Now we discuss what each component does.  Please refer to the first image  above.

  • Grid tie inverter  -  A solar system that is connected to the utility power gridpulling electricity from the grid when needed, then pushing excess electricity back into the grid when you aren't using the full capacity being generated by PV panels (photovoltaic).  As long as the grid stays up, it's a clever solution because it reduces or even eliminates the customer's electric bills while generating "clean" energy.  Grid-tied systems do not provide protection from power outages. When the electrical grid fails, grid-tied systems will not continue to operate.  Because of the very fact that these systems are tied into the power grid, however, they all have a safety feature that disconnects them from the grid when the grid goes down. In other words, if the power grid goes offline, your entire grid-tie solar array becomes instantly useless and you can't power a laptop computer even if you have $100,000 worth of solar panels sitting on your roof. In a grid-tie system, they all are instantly shut off.
  • You can watch this video to understand more how grid tie inverter works .

    • Limiter - This thing controls the amount of power that the grid tie inverters (GTI) can generate so that the amount of excess power produced by the solar panels are reduced to insignificant levels, if not eliminated --- because in some countries like the Philippines the producer pays for the excess power it gives to the distribution grid. This is because the electric power meters (the one provided by the electricity provider in the area) are not aware of the direction of power flow. In other words it only adds even if power is exported to the grid, thus, the consumers will be charged for power even if it is given to the grid, and this is the problem.gtil connection
      lm module
  • Off-Grid Inverter  -  When the power grid goes down, your entire PV array is instantly disabled by your grid-tie inverter, and you cannot use your PV array for anything! Even if the sun is shining, you will have no power from it. This is where the off-grid inverter (The inverter that is connected in the battery bank as seen in the diagram above) comes in. As you can see this inverter has its own solar panels connected. This is just a small (300watts) solar panels used just to float charge my battery and ready to kick in automatically anytime when a power interruption occurs. By default the large array of solar panel are connected to the grid tie inverter and when during  power interruption  I can easily transfer it to the charge controller by flipping the DPDT ( left side dpdt switch ) switch if I want to connect heavy loads or charge the battery bank and flip it back to the grid tie inverter when utility power is back.   The load that you can connect to the off-grid inverter is just within or limited by its capacity that is why I'm using a grid tie inverter as the default system since it has no overload.  I'm using the pip-hs-series off grid inverter of MPP Solar and you can configure it to power the loads from the utility grid when sun goes down so that your battery stays full at night as preparation for any power failure. This off grid inverter can sense power failure automatically and use the the power bank as power source. The DPDT switch at the right is used to transfer the load directly to the utility grid or to the off-grid inverter.


Off-grid inverter is very easy to connect. there are always two wires from the solar panels (take note of the polarity), two wires from the utility grid and  to the load. You can follow it easily  in your inverter's  manual when you buy one.  🙂

* Other components not discussed in the picture are  safety switches that the system can operate without it but it is highly recommended  *

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