3rd world utility company service. Generator + Solar power plant big mistake ?

[RRV]

I am a follower of your channel and find it to be very instructive. Recently a friend of mine brought up a question which would perhaps be of interest for a future video in your channel: If you have a home grid tie system up and working in a 3rd world country in which utility companies treat your home is a xmas tree (power goes and comes), it would be tempting to:

1- shut the main breaker down during an outage and
2- hook up a single split phase (120-neutral-120VAC) generator (batt or gas) feeding your temporarily grid isolated home. This generator would trick the solar inverter into thinking the grid is there... mmm...

Chances are bad things may happen as I believe that if your home´s load does not consume the 100% of the energy your grid tie system produces , the grid tie inverter would try to rise the line voltage continuously until either your appliances, the generator, or the inverter itself break. Can you please give your expert opinion on this ?

 

[timselectric]

Better option would be to add a hybrid inverter capable of ac coupling. So that it can control your existing system. And feed it with the generator.

 

[Ellis Redding]

I am a follower of your channel and find it to be very instructive. Recently a friend of mine brought up a question which would perhaps be of interest for a future video in your channel: If you have a home grid tie system up and working in a 3rd world country in which utility companies treat your home is a xmas tree (power goes and comes), it would be tempting to:

1- shut the main breaker down during an outage and
2- hook up a single split phase (120-neutral-120VAC) generator (batt or gas) feeding your temporarily grid isolated home. This generator would trick the solar inverter into thinking the grid is there... mmm...

Chances are bad things may happen as I believe that if your home´s load does not consume the 100% of the energy your grid tie system produces , the grid tie inverter would try to rise the line voltage continuously until either your appliances, the generator, or the inverter itself break. Can you please give your expert opinion on this ?

So the generator would definitely have to be a inverter generator. The general purpose ones do not produce clean sine wave power and the inverters, generally, won't like it.

 

[TorC]

You'd also have to be able to set the system to never backfeed the generator. That can do bad things to the sytem. The hybrid inverter, if it can control the rest of the system, will act as the generator safely, and the generator is optional. A battery bank will be needed, but depending on how long your outages are it may only need enough capacity to safely buffer your potential solar output.

 

[timselectric]

In my opinion. The best way to use a generator, is a small generator to charge batteries. The most efficient way to use fossil fuel.

 

[Hedges]

SMA describes use of PV inverters and Sunny Island AC coupled battery inverters with a generator.
Sunny Island will connect & start generator when needed, and disconnect to prevent backfeed from PV.

https://files.sma.de/downloads/SIGEN-11FD1212.pdf

The desired generator characteristics are presented, and one which rises slightly in RPM (Hz) unloaded but drops to 60 Hz (50 Hz in other markets) will allow the PV inverters to help supply loads. The GT PV inverters are configured for frequency-watts, where power output ramps down with increasing frequency from 100% up to 61 Hz down to 0% at 62 Hz. For off-grid use, they remain connected up to 64 Hz, ready to pick up load at a moment's notice.

With such generator RPM behavior and inverter behavior, it might even work with those two directly connected. But best to include the AC coupled inverter (with feature of frequency-shift management of generator). Depending on PV and battery capacity, generator may not be needed.

Alternatively ...

There are inverter generators with HV DC rail internally. I've wondered if PV array could feed that DC rail directly. Without MPPT to couple them, need to size array so Voc never exceeds maximum allowed on DC rail and Vmp is sufficient to power it.

Most reasonable and economical solution is to select a hybrid inverter, either requiring batteries or batteries optional.
The low-cost brands of such inverter are much less expensive than the AC coupled solutions.
If you are willing to pay the price of quality brands, there are good AC coupled battery inverters. But GT PV inverters used with them must do "frequency-watts" adjustment of output power in response to frequency.