Mitigation of electromagnetic vibration in PMSM: A rotor position related variable switching frequency technique

In this paper, a rotor position related variable switching frequency strategy is proposed to mitigate the electromagnetic vibration and noise due to pulse width modulated (PWM) harmonic current. It begins with an introduction of mathematical models for permanent magnet synchronous motor (PMSM) and space vector pulse width modulation (SVPWM). Then, connection between PWM current ripple in d-q reference frame and electromagnetic radial force are analyzed. Next, switching frequency is modified online to adapt current ripple and vibration requirement, thus ameliorate the acoustic noise. It is expected that rotor position related variable switching frequency has the advantages of reducing radial force ripple and spreading the vibration spectrum. Experimental results comparing constant switching frequency and variable switching frequency have been presented.