Application of Proportional-Integral and Disturbance Accommodating Control to Variable Speed Variable Pitch Horizontal Axis Wind Turbines

Variable speed operation of wind turbines allows increased energy capture over a large range of wind speeds, but in high wind speeds continuous energy capture is subject to the physical limitations of the turbine. The turbine rotor speed and power production must be held beneath certain threshold values and the fatigue of the mechanism that restricts the rotor speed should be minimized if possible. This paper investigates the application of Proportional-Integral (PI) control and Disturbance Accommodating Control (DAC) to satisfy the turbine physical constraints while operating the wind turbine. A simple, single-state nonlinear model of the turbine dynamics is developed for use in designing the controllers and in simulating their operating dynamics. The performance of each control scheme is evaluated qualitatively to examine functionality, as well as quantitatively to support a comparison. DAC and PI control are found to exhibit comparable performance. PI control is marginally superior, but it is limited to single-state control and the design is more turbine-specific than a DAC design.