Enhanced Frequency Regulation Strategy for Wind Turbines Based on Over-speed De-loading Control

Abstract

Wind turbines (WTs)can participate into frequency regulation of power systems by over-speed de-loading control. With conventional de-loading control, before frequency disturbances, the WT operates at a de-loading point with a reduced active power output instead of Maximum Power Point Tracking (MPPT), preserving a certain amount of wind power reserve for frequency support. During the frequency regulation, the operating point of the WT moves back to the MPPT curve, increasing its active power output to support system frequency regulation. However, since the WT can operate over a wide range of rotor speed, after reaching the MPPT curve, the WT can further provide active power support by decreasing its rotor speed and releasing the kinetic energy stored in its rotating mass. This paper proposes an enhanced frequency regulation strategy for WTs based on the conventional over-speed de-loading control. By exploiting both the wind power reserve and the kinetic energy, the active power support of the WT during frequency regulation can be significantly increased. Simulation results show that the proposed strategy can improve the system frequency response by reducing the frequency excursion. Meanwhile, the system secondary frequency drop can be avoided.