Research on the structure of low voltage DC distribution network based on MMC improvement

In this paper, the AC-DC-AC low-voltage DC distribution network is studied on the AC-DC side. Firstly, this paper proposed an improved sub-module capacitor voltage balance control model predictive control (MPC) strategy, which established objective functions for the modular multilevel converter (MMC) phase current, circulating current and submodule capacitor voltage respectively, and this paper selected the best combination of switch states through rolling optimization, eliminating the weight coefficient and simplifying the traditional MPC strategy.Secondly, by reducing the number of predicted sub-module switch state combinations, the computational complexity of the algorithm is reduced, and combined with the calculation of other MPC strategies to verify its correctness. Finally,through the II-level MMC system built in Matlab/Simulink environment, it is verified that the improved MPC strategy has good steady-state characteristics and dynamic characteristics.