Discrete-Time Current Control of Modular Multilevel Converter for Medium Voltage High Power High-Speed PMSM

High-speed permanent magnet motors (HSPMMs) have gained ever-increasing interests in high speed direct-drive applications due to their advantages of high-power density, small size and high efficiency. However, the low stator inductance of the HSPMM causes large current ripple in the stator current, therefore brings additional iron loss. The modular multilevel converter (MMC) increases both voltage level and equivalent switching frequency, which help reducing current ripple. In this paper, an exact discrete-time model of modular multilevel converter for medium voltage high power high-speed PMSM is developed. Based on this model, a discrete-time current control considering one-sampling step digital delay is proposed. Simulation results show that the proposed discrete-time current control method has significant performance.