FS-MPC Method for MMCs with Large Number of Submodules with Reduced Computational Cost

The model predictive control (MPC) strategy has been extensively investigated for the control of modular multilevel converters (MMCs). To avoid the high amount of calculation for the evaluation of all switching states, the MPC can be used to determine only the arm voltage level while the submodule (SM) gate signals are further determined by capacitor voltage sorting scheme. Among such techniques, there are some methods based on the evaluation of adjacent voltage levels, the effectiveness of which diminishes as the number of SMs of MMC increases. To overcome this drawback, this paper proposes a solution based on SM-grouping technique considering the current-regulating capacity. Several simulation tests are carried out on an MMC-based high power system with 128 SMs per arm, the results of which validate the enhancement of performance (steady-state and dynamic) of the MPC method resulted from the proposed approach.