Gain scheduled active power control for wind turbines

Traditional wind turbine control algorithms attempt to maximize power capture at low speeds and maintain rated power at high wind speeds. Active power control refers to a mode of operation where the turbine tracks a desired power reference command. Active power control enables wind farms to perform frequency regulation and to provide ancillary services in the energy markets. This paper presents a multiple input, multiple output strategy for active power control. An H∞ controller is designed at several operating points to coordinate the blade pitch angle and generator torque. The objective is to track a given power reference command while also minimizing the structural loads. The controller is gain-scheduled based on the wind speed and the power output in order to compensate for the nonlinear turbine dynamics. This allows the turbine to be operated smoothly anywhere within the power / wind speed envelope. The performance of this gain-scheduled design is evaluated using high fidelity simulations.