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ATS on AC coupled grid tied system.
#11
(08-26-2019, 01:10 PM)completelycharged Wrote: Looking at the specification (from the manual) for your unit, DO NOT CONNECT ANY PV INVERTERS TO THE CRITICAL/UPS OUTPUT.

The inverter stage is a high frequency type (in the manual) and does not allow backfeed of any PV power, unlike the design of the Victron units which are a low frequency type setup.

The design of the unit is such that one of three things will happen :

1. The unit would burnout as the PV inverters fight the frequency following of the inverter
2. The unit would shutdown with over voltage when there is insufficient load attached
3. The PV inverters would shutdown on over voltage when there is insufficient load attached

Best case, the supply would be at the maximum voltage range when you have insufficient load (which will make all EU specific tollrance based, 220V, appliances fail before thier time).

This is effectively your inverter design :
48V Battery -> DC Boost only stage -> HV Capacitor -> Inversion stage -> 240V AC

The other interesting bit in the spec for the unit is the short circuit handling capability (100A 1uS) which with a typical fuse/breaker as protection any short near the unit will likely result in the output inverter stage blowing (FET replacement fix). Just be carefuls as to what and how much you attach as suirge handling from some appliances may be an issue.

Yeah

I’ve resigned myself to the fact that I’m only going to use the UPS or as they call it the EPS for a critical
loads board as intended.

I’m going to fit an additional consumer unit and put a couple of lights, maybe a couple of socket outlets for fridge etc and the heating controls onto it.
UK Southwest.

7 kWp Solar Panels (28 x 250Wp Shinetime Mono).
14 X APS YC500i Micro Inverters.
28 X 40P 18650 cell packs/modules configured as 14S 80P.
Sofar Mass Energy ME3000SP AC coupled charger/inverter.
Still sourcing and processing cells for powerwall.
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#12
Take a look at my build. I did exactly what you're looking to do. However, my inverter does allow power to be backfeed from the output into the battery and my Micros support curtailment so the inverter can shut them off by rising the frequency above 62.5hz (although this can also be accomplished with a contactor on the solar backfeed breaker)

https://secondlifestorage.com/showthread.php?tid=7743

Here's the document on curtailment for my micros
https://enphase.com/sites/default/files/...attery.pdf

I would also stay away from load sinks. If the device you're using as a sink fails that power has nowhere to go, I primarily use freq shift, if that fails my controller detecs power still being produced and it'll open the contactor for the solar shutting down all solar production and if those 2 fail the BMS will disconnect the battery if voltage goes above 4.1v per cell.

It's all about having redundancies to prevent a fire.
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#13
The inverter in the link (12kW) in the thread is a low frequency type driven by a H-Bridge (8 FET's x 4) arrangement, which work quite well charging (back feeding) or supplying loads. The inverters I have put together are the same principle.

Using frequency deviations to switch the solar off (causing automatic over frequency disconnection) requires the house to be running fully off the inverter at the time, so the house grid de-syncronises from the mains and then re-syncronises back so the inverter runs in line mode.

Not sure I would implement this type of control method because it is relying on the inverters automatically disconnecting and may be repeatedly emergency disconnecting under full load, which would not do the relays any good and may cause early failure depending on how the shutdown is implemented within the inverter firmware.
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#14
I'm out of my depth here - but what about a 'manual solution' where if the grid goes down
1) you disconnect from grid (switch the main breakers off)
2) feed in 'simulated' grid power from a generator or independent battery/inverter - to enable your system to think it has grid and keep active.

This would not be automatic but maybe a manual method is better than none?
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#15
(09-20-2019, 09:04 PM)completelycharged Wrote: The inverter in the link (12kW) in the thread is a low frequency type driven by a H-Bridge (8 FET's x 4) arrangement, which work quite well charging (back feeding) or supplying loads. The inverters I have put together are the same principle.

Using frequency deviations to switch the solar off (causing automatic over frequency disconnection) requires the house to be running fully off the inverter at the time, so the house grid de-syncronises from the mains and then re-syncronises back so the inverter runs in line mode.

Not sure I would implement this type of control method because it is relying on the inverters automatically disconnecting and may be repeatedly emergency disconnecting under full load, which would not do the relays any good and may cause early failure depending on how the shutdown is implemented within the inverter firmware.

Why would the whole house need to be on the inverter for freq shift to work? If you have a sub panel with only the loads you want backed up it would also work.

I see your point about repeated disconnections. Maybe I should have said "Use an energy diversion but have a failover that will kick in if your diversion fails."
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#16
My initial thought was to keep the micro inverters online to charge the Powerwall during daylight hours with the solar surplus power being generated that's not used by the house when a grid failure occurs.

I have now decided that I'm going to fit a separate consumer unit to supply some lighting a few socket outlets for frigde/freezers, phone chargers etc. and maybe the heating system.

The Sofar ME3000 has a EPS built in so makes it very easy to do with the just one contactor.
UK Southwest.

7 kWp Solar Panels (28 x 250Wp Shinetime Mono).
14 X APS YC500i Micro Inverters.
28 X 40P 18650 cell packs/modules configured as 14S 80P.
Sofar Mass Energy ME3000SP AC coupled charger/inverter.
Still sourcing and processing cells for powerwall.
Reply


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