You need a Simulink function, whose output port is connected to a "To workspace" block. Let's call this function RecordGenerationTime().
You also need a function to get the simulation time. This function contains a Digital clock block. Let's call this function GetSimulationTime().
In the Entry event action for all of the generators, you first get the current simulation time, and then record it:
CurrentSimulationTime = GetSimulationTime();
RecordGenerationTime(CurrentSimulationTime);
When Simulink is done executing the model, you can see the results in the structure created in the base workspace, which contains a timeseries object that contains the exact records for the generation times.
