what are the methods to protect mosfets in a high current and high voltage inverter?
you can use snubbers for high voltage spikes during switching, while for current mostly people use current limiter method to limit current.
I don't know if I fully understand your question, I hope I will address it properly, you want to know about protection methods or design strategies to avoid damage in the MOSFETs, right?
For avoiding an over-voltage in MOSFET active clamping can be used to limit the voltage during turn-off but that will lead to increase in losses.
Two steps turn-off or slow turn-off could be used but there is a trade-off with losses.
Reducing your commutation loop inductance also helps, as during the turn-off transient the peak voltage will be lowered.
Also, some GD monitor Vds and in case the voltage is above a threshold during OFF state, a fault signal is sent to the controller to trip the inverter.
For avoiding over-current, normally it is possible to sense Vds during the Turn-ON and during ON state to detect fault currents. As the current raises steeply towards the saturation current Vds will raise as well. Or the current could be sensed using other strategy (Rogowski, CT, etc). Once the fault is detect the turn-off process must be done carefully as high fault currents even with low inductances commutation loops could cause high overvoltages in the switch.
Moreover, temperature is very important, so designing your converter accordingly and monitoring it is quite important. Coolant/Air temperature as well as load current could be measure and a prediction for the MOSFET temperature made, if it is not possible to measure the temperature right away.
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