Common-Mode Voltage Suppression Strategy for CHB-Based Motor Drive Based on Topology and Modulation Optimization

The paper proposes a common-mode voltage (CMV) suppression strategy for the cascaded H-bridge (CHB) based mo-tor drive. CMV can be categorized into two components: the low-frequency component associated with the motor frequency, and the high-frequency component related to the switching frequency. Low-frequency CMV primarily originates from the voltage fluctuations of submodules (SMs), and a topology method of CHB cascading four-port dual-active bridges (CHB-FDAB) is proposed. The CHB-FDAB, in conjunction with synchronous modulation of FDAB three full-bridges cascading with three-phase SMs, can effectively mitigate SM voltage fluctuations and prevent the occurrence of low-frequency CMV, which can also create a reduction for cost and volume of system. High-frequency CMV is generated by the modulation of CHB-stage, and a novel carrier phase-shift pulse-optimization PWM (CPSPO-PWM) strategy is proposed. The CPSPO-PWM can ensure that the difference be-tween the output voltage sums of the left and right arms of the all three-phase SMs is zero, effectively suppressing the generation of high-frequency CMV. Additionally, CPSPO-PWM exhibits minimal increases in current ripple, torque ripple, and system power loss. As a result, the completer suppression of CMV throughout the entire speed range of motor can be achieved. Finally, simulation and experimental results validates the effectiveness of proposed strategy.