Quasi 2N+1 Level Modulation Based Overvoltage Oscillation Mitigation in Long-cable-fed Cascaded H-bridge Motor Drives

For medium-voltage long-cable-fed motor drives, the inverter high-frequency pulse width modulation (PWM) pulse voltage will reflect at the motor terminal when the motor surge impedance and cable characteristic impedance do not match, causing serious overvoltage oscillation and damage to the motor winding and insulation. The mainstream passive-filter schemes have drawbacks such as large volume, high losses, additional costs, and poor flexibility. Thus, this article proposes a quasi 2N + 1 level modulation scheme for cascaded H-bridge (CHB) inverters, which can eliminate reflected waves on the cable and achieve overvoltage oscillation suppression by inserting the fixed-width quasi level at each rising/falling edge of the inverter output voltage. Finally, the proposed scheme is verified through simulation and experimentation. Compared with existing suppression schemes, the system efficiency is significantly improved, and no additional components are required, avoiding additional volume and cost.