The error seems to be noticed in 'MicrogridActivePowerControl/powergui/EquivalentModel1/Gates/From1'. I'm guessing this is the "PWM"-From-Block to the right. A few steps beforehand you have a "PID(s)"-Block that seems to have an issue.
Note that the numbers on the arrows show the dimensions of the signal. Everyehere where there is a "?(dimension)", the compiler does not know the size of the signal. Since before the PID-controller the size is known and afterwards it isn't, the problem is most likely there. Maybe replace the block with a default PID and check if it works. Then change the block settings one at a time and check when it breaks. This assumes you changed anything in the PID-controller.
Second option: When looking at you diagram it seems that PWM should be of size [1x1] (the same as 1) since you only conntrol one gate. Note that your "RMS Measurement" outputs a vector of size [3x1] already. Maybe this is something you don't actually want. If you only want one of the three signals, use a selector block after the "RMS Measurement"
To the Mux Block error I can not say anything, since I do not know where the "-T-" comes from. It most likely assumes a 5-vector output which is can not do if the first input is of dimension 3 already. But maybe this fixes if you fix the other problem.
