A Novel Control Strategy for Modular Multilevel-Based Drives Considering the System Operating Point

Modular Multilevel Converters (MMC) are considered an attractive solution for high-power medium-voltage drives. However, in drive applications, the influence of the loading conditions leads to more complex control systems than the required ones for constant frequency applications. To solve this issue, a novel control methodology for the MMC-based drive is presented in this paper. The proposed scheme defines the best control structure to balance the voltage of the converter capacitors considering the drive operating point (e.g. the loading conditions and the machine frequency). The design of the converter parameters considering the desired behaviour of the converter is also discussed in this paper. Experimental results with an 18-power cells MMC are used to validate the proposed control strategy.