I'm not understanding the question here. If the purpose of the generator is to assist the generator in charging the batteries, then you don't need to convert the DC solar output to AC, just use both sources to charge the batteries. My solar panels are putting out any time the sun is shining. If my batteries are really low, or I just need to run the generator in the morning for the wife's hair drier, or something like that, then the 80 amp DC converter/charger pretty much takes over, generally limiting it's output based on battery state of charge. When I turn the generator off, the solar controller reacts to give the batteries as many amps as they can take, or in the case that the batteries can take more than the solar can put it, it just gives the batteries everything it's got.
To parallel the batteries with the generator you'll need a fairly expensive hybrid inverter. You'd use that for big AC loads like the microwave, or Air Conditioner that may be using more power than your generator alone can provide.
