Real-Time Estimation of MPPT Reference Point in Frequency Droop Controlled Wind Turbines

Conventional maximum power point tracking (MPPT) aims to control the operating point of a wind turbine to maintain maximum blade efficiency, despite varying wind conditions. However, when a wind turbine performs active power grid support functions such as frequency droop control, the generator speed and power may deviate from the MPPT operating point. This paper proposes a method to estimate the MPPT reference point for a frequency droop-controlled wind turbine in real time under the same turbulent wind speed. The proposed method is designed by serially coupling the output of a blade state estimator with the input of an MPPT state estimator. It is applied to a Type 4B wind turbine model, which includes a blade-generator two-mass model. Arbitrary errors are introduced to key parameters and variables to evaluate the robustness of the proposed method. Performance is quantified by calculating the mean absolute percentage error between the estimated value and the MPPT reference point. Simulation results demonstrate that the proposed method successfully estimates the generator speed and power of a wind turbine performing MPPT.