Comparison of three reactive powers to analyze operation of wind turbines during voltage dips

Three instantaneous reactive power formulations - Delayed Voltage (DV) approach, Currents´ Physical Components (CPC) approach and fundamental positive reactive power (FPRP) - are used in this paper for obtaining useful quantities in order to improve the operation analysis of the wind turbines. By comparing those reactive powers, useful and useless magnetic field components in the doubly fed wind turbines are identified. Non-fundamental reactive power and, thus, wind turbine harmonic magnetic field is obtained by the comparison of DV and CPC´s approaches. Negative reactive power, responsible of reverse magnetic fields, is defined by the comparison of CPC´s fundamental reactive power and FPRP. Moreover, decomposition of the FPRP into two reactive power components, due to the reactors and caused by the imbalances, provides additional information about unbalance effects on the main magnetic field of the generator. These above established quantities are finally used to evaluate an actual wind-turbine subjected to a two-phase voltage dip.