1 The Faculty of Engineering and Science, Aalborg University, VBN2 Power Electronic Systems, The Faculty of Engineering and Science, Aalborg University, VBN3 Department of Energy Technology, The Faculty of Engineering and Science, Aalborg University, VBN
This paper focuses on the design, thermal loading, and reliability of a three-level neutral-point-clamped back-to-back full-scale converter for a 10-MW direct-drive wind turbine equipped with a permanent-magnet synchronous generator. The reliability performance of the three-level converter is strongly influenced by the thermal behavior of the semiconductor devices and their mission profile which directly affects the lifetime and the cost of the entire converter. Therefore, a simulation platform is developed in a Matlab/Simulink and PLECS simulation environment to analyze the dynamics of the system using different kinds of modulation strategies and analyzing the different wind-load conditions that are dependent on roughness classes. This paper shows that the 60 ° discontinuous pulsewidth-modulation strategies allow better thermal performance and increase the estimated lifetime of the converter. Furthermore, the increment of the wind roughness class causes a larger dispersion of the mean values and the variation of the junction temperatures, which also affect the lifetime of the converter. Hence, the cycle lifetime largely decreases considering the variable-wind-speed profile. In fact, the results show that the reliability of the converter is strongly affected by the temperature-cycle behavior and nonlinear factors of the mission profile such as turbulence, 3p effect, and gust.
Ieee Transactions on Industry Applications, 2014, Vol 50, Issue 1, p. 484-494