For which application are you using MOSFETs ? Is it an inverter ?
If yes, I can give one possible workaround in order to avoid the use of MOSFET and make the model "bit less non-linear".
If the dynamics arising due to switching of MOSFET are not of much concern to you, and your primary focus is to study the overall operation of the system from the stability, performance and control system point of view, you can use the "Average value inverter" block from the simulink library browser. Refer to the below given documentation for more clarity.
As per my understanding, it will take less computation time as compared to the "MOSFETs". You can also use it in single phase full bridge configuration, by utilising only the "A" phase and "B" phase "duty ratio" input signal and connecting a single phase load between the above mentioned two phases.
I hope it helps !
