This thesis proposes the design method of LCL-filter considering to all modulation index for grid-connected HANPC inverters. The three level HANPC inverters consist of Si IGBTs and SiC MOSFETs. The HANPC inverters are used for high-capacity system with high output quality using SiC MOSFETs. According to capacity increasement, the filter size and cost are risen. The large L-filter occurs control dynamic reduction and voltage drop. To solve these problems, the LCL-filter has been 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 design is proposed considering to the 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 LCL-filter design is demonstrated by the simulation and experimental results.
