using the correct source

the controlled voltage and the three-phase source block appear to be ideal voltage sources because in a simulink model that has a dynamic load with any of these sources, i get high values of line voltage and current (way more than the voltage i set in the parameter tab) for high loads values.

......any idea how i can simulate a grid source i.e where the voltage varies (voltage sags and dips) if the varying load get too large?