Framework for Determining Optimal Grid Filter and Frequency in SiC Wind Power Converter

Silicon carbide (SiC) power semiconductor allows wind energy conversion systems (WECS) to operate at higher frequency owing to its lower loss compared to the IGBT counterpart. To evaluate the impact of higher frequency on grid filter, a loss and volume optimization scheme within wide frequency range is developed, considering variation of ripple current and core material. Two typical filter structures, namely L and LCL, are analyzed regarding the tradeoffs between efficiency and volumetric power density. The selection criterion of two core materials under specific frequency band is proposed upon the optimization. The inductor design is accomplished with a 400 kW system combining analytic approach and finite element simulation (FEM). It turns out the higher switching frequency enables 70% lower losses and 75% lower volume for SiC converter's LCL filter at 14 kHz, compared to Si converter operating at typical 3 kHz. Preliminary iron loss measurement has partially verified the loss model.