Double-Pulsing Reflected Wave Overvoltage Oscillation Suppression in Long-Cable VSI Motor Drives Induced by Narrow PWM Pulses

In the voltage source inverter (VSI)-fed motor drive system equipped with long cable connection, the differential reflected wave overvoltage (RW-OV) at AC motor terminals can typically reach a maximum of 2 per unit (pu) of the DC bus voltage when a single rising/falling switching is applied to an uncharged cable. However, under certain conditions, such as low-speed operation, the frequent narrow pulse-width-modulation (PWM) pulses will lead to the double-pulsing phenomenon, where the latest switching occurs while the voltage oscillation caused by the previous one has not fully decayed. This results in a differential RW-OV oscillation with an amplitude over 3 pu, which challenges the insulation capability of the motor and aggravates high-frequency electromagnetic interference (EMI) issues. Unfortunately, most solutions merely resort to passive ways to avoid this issue, i.e., either directly abandoning narrow PWM pulses below a minimum dwell time or extending their duration to allow prior voltage oscillations to decay. Therefore, the line-to-line double-pulsing RW-OV in three-phase motor drives has been insufficiently researched. This paper proposes a real-time duty-cycle-offset (RT-DCO) strategy that dynamically rotates which phase carries the maximum duty cycle and applies interleaved offsets to the other two phases, actively mitigating double-pulsing RW-OV behavior by leveraging residual oscillatory components to suppress subsequent voltage fluctuations while maximizing volt-second balance. Simulation and experimental results demonstrate the effectiveness of the proposed RT-DCO method in suppressing three-phase double-pulsing RW-OV oscillations.