Design of Inverter Side Inductance for LCL Filter in Modular Multilevel Converters

The modular multilevel converter (MMC) is promising in the low voltage applications with less submodule (SM) numbers. However, one of the significant challenge is that the output voltage harmonics are relatively high in these applications. To improve the AC side harmonic characteristics and decrease the cost of the filter, the LCL filter is introduced into the grid-connected MMCs. This paper design the parameters of the LCL filter based on the output characteristics of the MMC. In addition, the impedance model with different device parameters is derived to do stability analysis. With the proposed method, the output current harmonics are effectively suppressed. The effectiveness of the proposed method is verified with MATLAB/SIMULINK.