Parameter characterization of low frequency pulsating emissions from space vector PWM drives

Power converters in hybrid electric drives constitute a major source of electromagnetic disturbances. Recent studies have established that the space vector PWM scheme commonly employed in drive systems, generates low frequency pulsating (LFP) emissions, at a frequency of 6f₀, where f₀ is the fundamental frequency the phase voltages. The switching of voltage vectors generates common mode current (i_cm) spikes due to the presence of stray capacitances and inductances. Across sector boundaries, the i_cm spikes superpose forming spikes of double or tipple amplitude which constitute the LFP emissions. These pulsating emissions could pose EMC issues, and functionality issues like torque pulsations and speed fluctuations that could affect the reliability of the drive. This paper investigates the effects of drive speed, load, and converter slew rates, on the amplitude of the LFP emissions, using theoretical models.