An integrated common-mode voltage filter for a PM synchronous motor: characterization and control adaptation

Abstract

The high-frequency common-mode voltage generated by switching of semiconductor devices especially for the high frequency wide bandgap semiconductors may cause premature failure of the insulation system and metallic bearings in the motor drive systems, the false trigger of the relay devices, and electromagnetic interference. In this project, an inserted integrated CMV filter is proposed to reduce the hazards caused by the common-mode voltage in the permanent magnet synchronous motor system. In this filter design, partial motor windings that function both as inductive components in CMV filter and for generating magnetic flux are integrated with passive components. Compared to systems utilizing conventional passive filters, the integrated common-mode voltage filter, which eliminates the need for a separate filtering inductor, reduces the overall weight and volume of the motor drive system while maintaining effective common-mode voltage reduction capability.
The inherent parameters of the motor, including inductance parameters and distributed parasitic capacitance, significantly influence the performance of the proposed plug-in integrated common mode filter. Specifically, the inductance parameters can induce equivalent mutual inductance on the passive branch of the filter, altering its electrical characteristics and thereby impacting the filter's effectiveness in suppressing common mode signals. Additionally, different winding segmentation methods affect both the common mode voltage reduction and overall motor performance. Changes in winding segmentation modify the electromagnetic coupling between windings influence the suppression of common mode voltage and performance metrics like motor efficiency and torque ripple. Reducing the hazards of common mode voltage is critical for the PMSM system. The common mode voltage on each winding couples through parasitic capacitance within the motor system, necessitating the identification of optimal insertion positions for the integrated filter to ensure stable and efficient operation.
Adaptive control is utilized in the PMSM system incorporating an integrated filter to achieve more effective CMV reduction while enhancing motor performance. This includes optimizing both modulation methods and control strategies. The synergistic effect between modulation techniques that reduce common-mode voltage and integrated filters is investigated. Modulation techniques alter the voltage output waveform at the inverter's terminal, and then integrated filters exert varying influences on mitigating the harmonic components of the common-mode voltage. The combination of these methods has a synergistic impact on reducing common-mode voltage. Based on these research findings, a more comprehensive parameter selection approach has been proposed. This approach takes into account the interrelationships among modulation techniques, filter parameters, and inherent parameters of permanent magnet synchronous motors (i.e., inductance, distributed parasitic capacitance) to ensure optimal coordination between modulation techniques and integrated filters, thereby minimizing common-mode voltage and enhancing system performance. From a control perspective, enhancing the performance of the PMSM system integrated with a CMV filter necessitates modifications to the control object. The discrepancies between the filter-branch and the motor-branch can be attributed to variations in both time and space. The temporal difference is caused by the inserted RC branch while spatial differences arise from variations in winding distributions of filter-branch and motor-branch. The specialized control strategy optimized the current distribution within the motor windings and enhanced the magnetic field distribution. By considering these two critical parameters, this tailored control approach improves overall motor performance.
Therefore, by combining the characterizations and adapted control strategies for the PMSM system with the integrated filter, the reduction in the system's common mode voltage while maintaining optimal performance could be achieved.

Date of Award	15 Oct 2025
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Xiaochen Zhang (Supervisor), Chunyang Gu (Supervisor) & Jing Li (Supervisor)