Efficiency comparison of 690V-converter topologies for wind power plants with DFIG

2-Level-converters with 1700V-IGBTs and 1100V dc-link voltage are common in wind power generation. However, this dc-link voltage is not sufficient to fulfill reactive power requirements of grid operators in any circumstances. In case of high active and reactive power generation of the wind power plant and an overvoltage in the grid the dc-link voltage has to be increased. In this paper the power losses of a 2-level-converter with a fictitious 2kV-IGBT and a 3-level-converter with 1200V-IGBTs are calculated for 1250V dc-link voltage and compared to each other. The loss calculation is done over a wind speed range from 0 to 12m/s. Additionally the converter energy losses in 20 years are determined assuming a IEC III wind speed distribution. It was found that the 2-level-converter with 2kV-IGBTs produces the highest power losses in any operation points. The losses with the 1200V-IGBT 3-level-converter and 1250V dc-link voltage are even smaller than for the 2-level-converter with 1700V-IGBT and 1100V dc-link voltage. The values for the 20 years energy losses are corresponding. Therefore it can be said that the 3-level-converter is a good alternative to the 2-level-converter with 1700V-IGBT due to reduced power losses and the capability to fulfill grid code requirements.