Comparison of the dynamic response of wind turbine primary frequency controllers

This paper presents a comparison of a variety of control strategies for the primary frequency control of wind power plants. These strategies include inertial as well as pitch angle regulators. The inertial control is sensitive to both the frequency variation through a standard droop control, and the rate of change of frequency. Since these controllers tend to counteract the operation of the Maximum Power Point Tracking (MPPT), the paper also investigates the effect of blocking the MPPT whenever the inertial control is enabled. The pitch angle control allows for a power reserve and prevents the rotor speed from exceeding the nominal value. A modified version of the WSCC 9-bus, 3-machine system with a 30% of wind penetration and a type 3 wind turbine model is considered in the case study. The behavior of these controllers are first analyzed separately. Then a compound controller, which merges together all strategies above, is proposed and discussed.