Thermal Behavior Optimization in Multi-MW Wind Power Converter by Reactive Power Circulation

The influence of actively controlled reactive power on the thermal behavior of a multimegawatt wind power converter with a doubly fed induction generator is investigated. First, the allowable range of internal reactive power circulation is mapped depending on the dc-link voltage and the induction generator and power device capacity. Then, the effects of reactive power circulation on current characteristic and thermal distribution of the two-level back-to-back power converter are analyzed and compared. Finally, the thermal-oriented reactive power control method is introduced to the system for the conditions of constant wind speed and during wind gust. It is concluded that the thermal performance will be improved by injecting proper reactive power circulation within the wind turbine system, thereby being able to reduce the thermal cycling and enhance the reliability of the power converter.