A Regenerative Hexagonal-Cascaded Multilevel Converter for Two-Motor Asynchronous Drive

This paper presents a hexagonal-cascaded multilevel converter for two-motor asynchronous drive application. By adding an ac input to the hexagonal configuration, this multilevel converter becomes a tri-port system with one input port and two output ports, which can drive two motors with asynchronous operation by sending different control commands. The detailed analysis of power distribution is presented, and it is found that the six branches are equivalent to two groups of three-phase voltage sources, which can share the power of two motors. The regenerative energy from one generating motor can be directly supplied to the other one in motoring mode. Consequently, the dc-link voltage overshoot can be suppressed, and the energy storage requirement of capacitors can be reduced as well. A two-motor drive system has been tested in MATLAB/Simulink and a downscaled laboratory prototype. Simulation and experimental results are provided to demonstrate the effectiveness of the proposed motor drive system and control strategies.