The effects of large rapid changes in generation from large arrays of wind turbine generators on the operation of automatic generation control (AGC) and frequency regulation will be assessed. The theoretical worst case change and rates of change of generation from an array of wind turbines due to passage of a thunderstorm front is given for a coastal farm. Constraints on the penetration of the portion of an echelon and farm that are affected by the front are derived so that power variation rates from a farm satisfying these constraints will not exceed the response rate capability of a typical system. These penetration constraints would eliminate the occurrence of excessive frequency excursions and violations of NAPSIC performance requirements on automatic generation control. The penetration constraints effect on the size of an array and the maximum power variation rates allowed on a particular system are discussed. The effects of simultaneous load and Wind Electric Conversion System (WECS) generation changes on automatic generation control, frequency regulation, and economic dispatch are then determined via simulation. It is shown that the total of load and WECS generation change in a ten minute interval must be less than load following capability for that period or a severe saturation problem occurs. A cycling problem is shown to occur if storm induced WECS generation change will cause frequency deviations that exceed governor deadband.