Research On The Control Strategy Of Motor Drive System Based On Modular Multilevel Converter

With the rapid development of social economy, the demand for power is increasing, so the rational use of power has become more urgent. The electricity consumption of motor drive system accounts the total electricity consumption of the whole society for a large proportion, so it is important to study on rational topology and efficient control methods for saving power. With many advantages in the field of multi-level, modular multilevel converter is concerned by the experts and scholars, and it is a good idea for applying it to the field of motor control.Firstly, the equivalent circuit of MMC is set up according to the topology of MMC and the working states of the submodules, and then its works and the submodule capacitor voltage control strategy are introduced. The expression of the submodule capacitor voltage fluctuation and the circulating current are derivated, and the mothed of decreasing the submodule capacitor voltage fluctuation and optimizing redundant module configuration of MMC are studied based on them.Secondly, the topology of the motor drive system based on MMC is given, and the control method of rectifier and inverter are studied. The precharging strategies of MMC are introduced based on the preceding analysis, then a fast and effective precharging strategy for back to back of MMC is proposed.Thirdly, simulation models are built using the software PSCAD, and simulation results demonstrate it can precharge quickly with small impact current and stable submodule capacitor voltage fluctuation. In the runtime, the grid side power factor is high and the output waveforms have good quality, meantime the inverter side drive motor with good dynamic performances, which verifies that the control strategies of the motor drive system based on MMC are feasible.Finally, the software and hardware of the control system are designed based on its overall framework. The experimental Prototype is finished with the experimental platform, and experimental results verify that the topology and the control strategies of the motor drive system based on MMC are feasible and valid.