An Improved H8 Topology for Common-mode Voltage Reduction

This paper presents an improved H8 power converter for common-mode voltage (CMV) reduction and electromagnetic interference suppression. The proposed H8 converter can realize zero CMV variation when entering and leaving the zero state, which is mainly achieved by both the improvement of the structure and the control strategy. For the system structure, two switches are added on the dc bus to float the ac part of the three-phase converter in the zero state. Besides, additional capacitors are used to realize controllable CMV. For the control strategy, a simple control strategy is proposed for the H8 converter. It can automatically adapt to the flowing orientation of the load current to realize synchronous switching of the power switches, which effectively eliminates the impact of the dead time. Through analysis, simulations, and experiment, a comparison between the proposed H8 converter and the conventional H6 converter is performed. Results validate the effectiveness of the H8 topology.