I bet the first thing to go would be the capacitors, but if not as soon as you had a spike that exceeded what the IGBT/MOSFET can handle they would start a cascade failure. However if it's smart enough it wouldn't even turn on and just give you an over voltage warning.First the more generic questions: What are the limits on overvolting a controller? What breaks first?
I can see how switching would get dicey at too high a voltage. What if the controller was at 100% duty cycle, could you then switch in a higher than spec voltage?