Now you also say you want it to operate from teh 2 sources. IF bose sources are the same voltage output, just use 2 diodes to OR them together (into as big of a DC-link capacitor you can get!!!).
IF they dont, like I just said you are only going to be able to run off one at a time (without alot more complexity).
So lets say you now have a 30V DC-link (from whatever means), you need to get this upto 120V AC (which is 170V)
Thus you will need out ouput transformer to upp your inverter voltage to 120Vrms.
However, from your DC-link to your transformed voltage will be losses.
Thus the aim will be to make a 20V peak, this provides your voltage headroom needed. With a higher link, your control will still cope and still make a 20V peak waveform.
So the inverter. You will need MOSFETS (since low voltage) But ones that can handle 150A or greater (assuming a link of 30V, a higher link will cause less amps)
All this inverter needs to be is two FETS one on top of each other, the star point will be teh AC output. This needs to be connected to a L-C filter to remove the switching frequency. After the filter you will take the feedback signal as well as feeding it into teh trasformer.
OK I know this is alot, IF you give me abt 15min I will quickly draw up a conceptual drawing, it will be analogue and no specific IC/parts, but from that you should be able to isolate what needs to be done in the microprossor and also find the relevant parts