Ha-Rang Jo, "계통 연계형 하이브리드 ANPC인버터의 전 영역 전압 변조 지수 기반 LCL-필터 설계," 아주대학교 공학석사 학위 논문, 2022. > Paper

This thesis proposes the design method of LCL-filter considering to all modulation index for grid-connected HANPC inverters. The HANPC inverters 

are three-level inverter and consist of Si-IGBTs and SiC-MOSFETs. According to capacity increasement, the filter size and cost are risen. To solve the problem, the LCL-filter is used. The various design method of LCL-filter is fixed to only one modulation index. Using the conventional methods 

makes the output quality worse in low modulation index. Therefore, the LCL-filter is designed considering modulation index in this thesis. The current 

ripple of LCL-filter is determined with an inductor voltage. The changed inductor voltage according to the modulation index is analyzed and calculated 

for the current ripple factor which is related to current THD. The inductor on the inverter is designed by the current ripple factor. The filter capacitor 

and the inductor on the grid side are designed by the current ripple attenuation and the reactive power absorption, respectively. The validity of the 

proposed designed method is demonstrated by the simulation and experimental results.