Improved Vector Sequence Modulation Strategy for Suppressing Conducted EMI in Three-Phase PMSMs

Two-level three-phase voltage-source inverters are widely used in permanent magnet synchronous motor-drive systems. Using pulsewidth modulation (PWM) for control will generate a common-mode voltage (CMV), which acts on the stray capacitance of the motor to ground and generates common-mode leakage current, increasing the conducted electromagnetic interference (EMI). In this regard, this article proposes an improved vector sequence PWM that suppresses the amplitude of the CMV while reducing the conducted EMI caused by PWM without increasing system volume and cost. The vector action sequence and PWM waveforms of the proposed strategy within each sector are presented. The high-frequency harmonics of the CMV generated by the proposed strategy and the impact of deadtime on the proposed strategy have been analyzed. The switching loss of the proposed strategy has been calculated. Compared with other modulation strategies, the proposed improved vector sequence PWM can effectively reduce the conducted EMI. The experimental results have been provided to verify the effectiveness of the proposed strategy in suppressing CMV amplitude and conducted EMI.