Maybe the breaker that trips is the main 30A breaker? If there's some other non-negligible loads as well (particularly a water heater), it would not be hard at all to exceed 30A...and possibly not otherwise depending on the microwave and the air conditioner in question.
If it is the 30A breaker that's popping, it may also be that the breaker is old/worn and tripping below its rating. That happens sometimes; replacing it would help in that case.
If you have a generator with a transfer switch, you'd have to upgrade the transfer switch at the same time.
I suspect it won't be too difficult to find a 50A panel that fits in the space of your 30A panel. The Parallax 3050-15 and WFCO 8930/50 are both pretty compact AC and DC distribution panels with 50A capacity. Neither one has a converter built in; if the panel you're replacing does (and is of this approximately 9" high size), you'd have to put it in a box or buy a deck-mount converter or something equivalent.