Active and Passive Control of Nine-Phase Wind Turbine Conversion Systems: A Comparison

This paper compares active and passive 9-phase rectification schemes in a wind turbine (WT) conversion system with a hybrid generator (HG). The passive stage consists of 9-leg uncontrolled rectifier while the active converter is a 9-phase 3-level neutral point clamped (NPC) converter controlled by a proposed space vector modulation (SVM) technique. The output of WT in both cases is connected to a medium voltage DC (MVDC) collector grid. A benchmark WT from offshore Walney wind farm in the United Kingdom is used for the basis of the study. The voltage, current, and power of the two converters are simulated and compared, and the study concludes that the use of a 9-phase 3-level converter has advantages over the passive rectification with HG. The simulation findings are in good agreement with expected results, indicating that the models and methodology are valid.