Active rotor speed protection for DFIG synthetic inertia control

DFIG-based wind turbine can participate into system frequency regulation through synthetic inertia control, which needs the rotor to decelerate and release its kinetic energy to meet the system demand. However, kinetic energy stored in the rotor is limited and if too much of it is released, wind turbine must exit frequency regulation through decreasing its output active power immediately and this will lead to a secondary drop of system frequency. To protect the rotor speed from decreasing too much and prevent the secondary drop of system frequency caused by exiting frequency regulation of wind turbine, this paper proposes an additional control strategy named active rotor speed protection which can cooperate with synthetic inertia control and prevent excessive drop of the rotor speed, the new strategy is based on analysis of kinetic energy of the wind turbine's rotor and simulation results proved the effectiveness of this strategy.