Impact of emulated inertia from wind power on under-frequency protection schemes of future power systems

Future power systems face several challenges. One of them is the use of high power converters that decouple new energy sources from the AC power grid. This situation decreases the total system inertia affecting its ability to overcome system frequency disturbances. The wind power industry has created several controllers to enable inertial response on wind turbines generators: artificial, emulated, simulated, or synthetic inertial. This paper deals with the issues related to the emulated inertia of wind turbines based on full-converters and their effect on the under-frequency protection schemes during the recovery period after system frequency disturbances happen. The main contribution of this paper is to demonstrate the recovery period of under-frequency transients in future power systems which integrate wind turbines with emulated inertia capability does not completely avoid the worse scenarios in terms of under-frequency load shedding. The extra power delivered from a wind turbine during frequency disturbances can substantially reduce the rate of frequency change. Thus it provides time for the active governors to respond.