question

mcwidowmaker avatar image
mcwidowmaker asked

Moving load from grid to inverter when the load goes too high

I want to change my grid connection from 150A 3 phase to 80A 3 phase to save costs. The problem is I need to provision for load spikes that exceed the 80A supply and I do not have control over the loads (Commercial tenants). I am planning to add 3 x 15Kw Quatro inverters to the supply, but I want to know if there is a way to allow and control feedback from the battery bank / charge controllers to negate / mitigate load spikes when the loads reaches 70A or higher on a phase or more. So if a phase needs 100A, I want to supply 30A from the inverter / battery bank instead of causing the grid to trip.

Can this be done in ESS, MQQT or Modbus if I add a 3 phase CT meter to monitor the loads? How would one program this and what equipment is needed?

microgrid
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4 Answers
Alexandra avatar image
Alexandra answered ·

@Mcwidowmaker

Use the input current limit to control the maximum pulled from the grid.

It will then power assist the grid and peak shave.

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Kevin Windrem avatar image
Kevin Windrem answered ·

Is this a 120 volt or 230 volt system? If it's 230 volt you need more than 15 KVA to satisfy the 150 amps and limit the grid to 70. 15KVA is 65 amps at 230 volts but you would need to supply 80 amps to cover the shortfall (150 - 70). If it's a 120 volt system you should be fine.

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mcwidowmaker avatar image
mcwidowmaker answered ·

Thanks for the input. Its a 230V system, but the loads never get close to the full 150A. I suspect the most the inverters will need to add will be around 20A or so. But I would like to feed back from a microgrid inside to the loads if possible, but I suspect this is going to be too much.

grid.png

That is the preferred idea, if I can push back from the microgrid to reduce the loads on the main connection. If this is not possible, the only solution I can think of is to move the inverters to the main connection with input current control limiting, switching the microgrid to single phase and create a microgrid that way.


My problem is that I have a Kaco 3 phase 40KW inverter in the mix, reducing loads on the grid. I don't really want to add inverters inbetween that and the grid, as the will keep it on when the grid fails and I suspect controlling it will prove to be a bother. I also don't want the inverters that does input limiting to keep the grid alive if it fails. It must only prevent the loads from exceeding the max capacity. Only the microgrid must stay up when the grid fails.


grid.png (10.4 KiB)
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Kevin Windrem avatar image
Kevin Windrem answered ·

The Quattros will only feed back to the "other loads" if the grid is present. If the grid goes down, the Quattro's AC input relay will open isolating it and the "critical loads" from the grid and everything connected to it.

The AC input current limit is intended to limit current from the AC source. I'm not sure how it functions with inverters and loads connected to it's input. So I'm not sure if the Quattro will be able to feed power to the "other" loads and reduce the grid current.

You will certainly need an AC input power meter in this system, connected up stream of all components so it monitors only grid power flow.

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