Development of an Analytically Described Pitch Regulator for a Wind Turbine to Be Used for Grid Disturbance Studies

Abstract

In this paper, a pitch controller for a variable-speed wind turbine to be used in the high wind speed region is derived. The pitch regulator parameters are determined using analytical expressions and are compared with numerical calculations. In order to derive the pitch regulated wind turbine model, blade element momentum theory is utilized and reformulated analytically. Appropriate simplifications are made and, finally, the analytically derived pitch regulated wind turbine model is tested under grid disturbances such as voltage dips and spinning reserve provision. From this work it was found that by linearizing the blade profiles, one can analytically derive a fully functioned pitch regulator. In spite of all nonlinearities, a single pitch controller setting which is valid for the whole operation region is shown to be sufficient. This system is tested under grid disturbances and it is proven that the system is capable of operating well during a 0% remaining voltage dip and also during the voltage recovery back to the rated voltage level. Accordingly, grid codes commonly referred to can be handled with this simply derived pitch regulator. Moreover, it is shown that the derived system works well for a spinning reserve application using a 90% spinning reserve ability and still maintains a robust turbine control.