Does a SolarEdge 3phase inverter function when only 1 phase is active?

[PaulvL]

I own a SolarEdge 7k 3-phase 230/400VAC is grid tied (6yrs old);
A nice system but what I don't like that in case of a blackout, it doesn't supply me with power
(even though we have very few power-outages in the NL 1 per 1-2 years).
Suppose during a blackout I ATS the system from the grid,
would the SE system work if I connect a small
offgrid 500-1000W with its own pure sine-wave inverter to only one phase
and 'trick' the SolarEdge inverter seeing the '(off-)grid, but then only 1 phase? or does it need to 'see' all 3 phases?

If so could I use a (variable) motor control drive for a 3-phase motor to create these 3 phases
(with very little actual power), again to trick the SolarEdge?
This could then even be done from a battery I guess?

 

[kernel]

You will need 3 clean phases either way. Not sure about the motor as an interface, but... maybe worth poking around.

 

[PaulvL]

Thx for the reply. To be specific:
3 phases to get 3 phases.
1 phase does not yield 1 phase from the SolarEdge.

 

[Hedges]

I own a SolarEdge 7k 3-phase 230/400VAC is grid tied (6yrs old);
A nice system but what I don't like that in case of a blackout, it doesn't supply me with power
(even though we have very few power-outages in the NL 1 per 1-2 years).
Suppose during a blackout I ATS the system from the grid,
would the SE system work if I connect a small
offgrid 500-1000W with its own pure sine-wave inverter to only one phase
and 'trick' the SolarEdge inverter seeing the '(off-)grid, but then only 1 phase? or does it need to 'see' all 3 phases?

If so could I use a (variable) motor control drive for a 3-phase motor to create these 3 phases7 kW
(with very little actual power), again to trick the SolarEdge?
This could then even be done from a battery I guess?

I think that Solar Edge inverter is strictly grid-interactive. If you succeed in tricking it into thinking your poor little 1kW off-grid inverter is the grid, Solar Edge will proceed to shove 7 kW into the little one. Same if you feed it from a spinning generator. More likely, whatever you hook up won't have the impedance of the bottomless pit that is the grid; the grid-interactive inverters actively test impedance by shoving in pulses of current at various frequencies, so they can distinguish the entire grid from an "island" where you are powering just the neighborhood and possibly zapping a utility worker. So probably won't produce anything.

What would probably work is if you purchased three Sunny Island (which can be had for a song right now, about $1500 each). So long as batteries are low enough to absorb whatever is left from the Solar Edge powering your loads, it should operate. As soon as batteries approach full charge and Sunny Island wants to taper off the current, it'll raise the frequency a couple Hz expecting a Sunny Boy to throttle back PV production. At 60.5 Hz the Solar Edge will shut off for five minutes. Not very well behaved.

You can buy some new PV inverters which are grid interactive and rated up to 7.7 kW from SMA, which also provide a single phase output during power failures good for up to 2 kW. No battery, no surge capability. Cost about $1500.

Or, get some sort of UPS, keep plugged in, and add a solar panel and PV battery charger.

PV panel and inverter prices have come down so much I'm swapping out perfectly good hardware just to get interoperability and more watts in the same mounting rack area.

 

[PaulvL]

The SE is 6 yrs now, lifetime expectancy 10 yrs. So looking at your advice swap it out with a better hybrid inverter. I can still wait a while in the NL the method of using the grid as a battery is stil valid until 2023. After that they gradually start charging you for 'use' of the grid as a battery.
Thk you for your elaborate comment.

 

[Hedges]

Even if we have to pay to use the grid it is still a good deal. According to my math, batteries cost as much or more than buying power from the grid (considering kWh cycle life), and you can never win $$ by banking either PV power or grid power in a battery to use at times of day when grid is more expensive. Battery only makes sense if you are willing to pay a premium to keep power on (e.g. for communications and convenience), or to avoid cost of stringing power lines. I'd be happy enough paying a modest fee of a few cents per kWh to bank them on the grid. I figure wet-cell would cost $0.20/kWh, AGM $0.40 kWh, Lithium in the same range.

Batteries are perhaps 80% efficient. Net metering used to be 150% efficient for me (I got back more kWh than I produced) but not since time of use terms were changed.

For now in California I pay $10/month for grid connection and have net metering. Peak times used to be after Noon, then after 2:00 PM, but now 4:00 to 9:00 PM. $0.15 off-peak, $0.45 on-peak, $0.30 part-peak for some hours. I could make three off-peak kWh for $0.05 each and get one on-peak hour in return. Not as good as before. But new PV costs me $0.05 vs. $0.20 for my original system.

If we ever get bumped to "We buy your power for $0.04 and sell you power for $0.45" instead of net metering, then the only way to win will be to use power as we produce it.

 

[PaulvL]

True, I would aim for a small battery to mitigate partly outages and in summertime optimize energy usage from the net.