Common-Mode Analysis and Suppression Method for Series-End Winding Motor Drive

The series-end winding motor drive (SWMD) is a new type of motor drive topology with wide speed range and high power density. However, current modulation methods for this topology suffer from significant fluctuations in common-mode voltage (CMV). Different from regular star-connected motor whose CMV is clearly defined, the series connection of the windings of SWMD makes its CMV analysis difficult. This article aims to solve this problem and improve the common-mode electromagnetic interference of SWMD. First, the common-mode conduction circuit of the electric drive system is analyzed and modeled. The relationship between system CMV and inverter switching states under different motor drive topologies is revealed. Then, it is clarified for the first time that due to the asymmetry of the SWMD, the CMVs on the motor and inverter sides are different. Then, the article proposes common-mode suppression methods for SWMD, including a constant CMV pulsewidth modulation method which can be applied at low modulation index and a reduced CMV PWM method suitable for the full modulation range. These two methods complement each other in terms of common-mode suppression and modulation range. Experimental results verify the accuracy of the CMV calculation method for the electric drive system and the effectiveness of the proposed common-mode suppression methods for SWMD.