My Solar PV system correctly shuts off power during a blackout - I want to safely override that

Question

For obvious safety reasons my residential PV system disconnects from the grid if it notes the grid is down. The thing is it also shuts itself off so that during a grid blackout rather than providing me power but detaching from the grid the inverter disconnects itself from both the grid and the panels leaving me without power. I want to safely defeat this safety feature that is to say I want to be able to use solar power when the grid is down without frying the guy in the cherry-picker working on the lines to fix them.

Edit to add: I was hoping I could do something more clever along the lines of : 1) manually throw knife switch to disconnect grid from my home. 2) turn on little liar circuit that puts out a drip of 240vac (powered by say a motor cycle batter) to make my inverter think the grid is live and then uses the inverter power feed to keep the 240vac liar circuit powered (as well as the battery charger for the motorcycle battery). Seems safe for the line workers and simple enough to build assuming the inverter will be fooled.

Answer 1

If your inverter shuts down completely when there is no line power, it is probably not capable of putting out AC without AC present. Some inverters assume the power line is essentially a 0 Ω source. They look at the voltage and decide what current to dump onto it. These types of inverters don't actually synthesize the 60 Hz themselves. They count on that being a input.

If you want to be self-powered during a blackout, you have to get the right inverter for that, which probably costs more. Then the inverter also has to deal with not being able to hold up the line to the proper voltage, and what to do about it. It gets complicated, which is why many inveters require the voltage waveform to already be there.

Answer 2

If your inverter is currently grid-tied, I don't think the anti-islanding feature is something you'll be able to defeat, since it's integral to the safety approval of the inverter (and is a gross violation of most electrical codes)

What it sounds like you need is a separate, off-grid inverter with an automatic transfer switch, that will keep the inverter isolated from the mains when not in use but power your loads after the mains drop out (with some small delay, of course). These schemes generally also involve battery banks to stabilize / provide at least some power when clouds or other solar obstructions occur.

I cannot say for sure if the particular model you've targeted can operate in off-grid mode. (People I know who have this model use it grid-tied.)

Considering the costs involved with a second inverter, you may be better off just going with a gasoline-fired generator for your backup power.

Answer 3

You would need a separate UPS that only provides standby power to a load it can handle and deal with diverting the DC power from the PV to charge the UPS instead of the grid supply. So all the Statement of work is done at the DC side.