Module Lifetime Evaluation Method for the Power Converter of the DFIG Based on the Analysis of the Field Wind Speed Probability and Ambient Temperature

Abstract

The junction temperature fluctuation (ΔTj) of the doubly fed induction generator (DFIG) around the synchronous speed point, deteriorates the reliability of the power converter considerably. Therefore, a lifetime evaluation method for the power converter of DFIG is proposed in this paper. Combining the speed-power curve of the generator with the grid side converter (GSC) and the rotor side converter (RSC), and using the equivalent thermo-electric network of IGBT module, the junction temperature (Tj) model of the power converter is established to calculate the average junction temperature and fundamental frequency temperature fluctuation. Based on the field measured data of the wind speed probability and ambient temperature of three wind power plants in different latitude region, the operation life curves of GSC and RSC are obtained by curve fitting, and the life spans of five type of power modules are evaluated and compared. It can be seen that the lifetime of the converter could be reduced significantly due to the ambient temperature-induced low frequency temperature fluctuations in the thermal cycling, while, the fundamental frequency thermal cycle caused by the running frequency of the converter has slight effect on the overall life.