Unloading and Frequency Regulating control for Direct-driven Permanent Magnet Wind Turbine by Changing Power Tracking Curves

This article firstly analyzes the unloading strategies of the wind turbine in different wind speeds, and designs a strategy to combine the over speed unloading and the pitch unloading. The droop characteristic is used to convert the active power increment required by the primary frequency regulation into the change of the unloading level, and the inertial response and primary frequency regulation are realized through changing power tracking curves. Finally, a simulation analysis of the unloading frequency regulating control under multiple wind speeds is carried out by using Matlab/Simulink software. The results show that the proposed strategy can achieve the expected target of the primary frequency regulation, eliminate the mutual influence between the additional droop control and the power tracking control, coordinate the inertial control and the primary frequency regulation control, and be restored to the initial state after the deviation of system frequency is eliminated.