Thermal behavior optimization in multi-MW wind power converter by reactive power circulation

In the paper, an actively controlled reactive power influence to the thermal behavior of multi-MW wind power converter with Doubly-Fed Induction Generator (DFIG) is investigated. The allowable range of internal reactive power circulation is firstly mapped depending on the DC-link voltage as well as the induction generator and power device capacity. Then the effects of reactive power circulation towards current characteristic and thermal distribution of the two-level back-to-back power converter is analyzed and compared. Finally the thermal-oriented reactive power is introduced to the system in 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 in the wind turbine system and thereby be able to reduce the thermal cycling and enhance the reliability.