You disabled the solver's "Max. number of consecutive zero-crossings" limit, likely because you were getting an error message. The error message is pointing to the fact that your PI output is changing faster than your carrier wave, leading to multiple comparator events per period. The result is an effective switching frequency much higher than you intended (100's of GHz). Disabling the zero-crossing limit simply masks the underlying issue and results in the long simulation times.
The solution is to fix the control scheme with an appropriately tuned PI controller. You can also insert a zero-order hold before the modulator to prevent multiple comparator events per period, but you will see the general control issue still remains, with the PI output toggling between the high and low limits.