Maximum Likelihood Output Curve and Modal Bounds for Active Pitch-Regulated Wind Turbine

A scatter of operating points is commonly observed over time whenever a pitch angle controlled (PAC) wind energy conversion system (WECS) operates in source wind susceptible to short duration variations caused by turbulence and gusts. A suitable interpretation of the distributed operating points can be useful in the context of real-time performance of WECS, and its evaluation once integrated within a conventional power network. This paper provides conceptual background culminating in an algorithm that allows estimation of most probable (maximum likelihood) operating points for a pitch angle-controlled WECS. It further allows establishment of modal bounds, within which short duration operating points are expected to occur given a modal cumulative probability. The concepts and algorithm are illustrated for a popular make of WECS assumed to operate in source wind conditions according to IEC61400-1 standards. Following from the concepts proposed, indications are provided for possible refinement of WECS output power curves thereby aiming to achieve better short duration unit performance.