Motor Overvoltage Limitation by Means of a New EMI-Reducing PWM Strategy for Three-Level Inverters

Pulsewidth-modulated (PWM) voltage-source inverters are known to provoke high-frequency disturbances in motor-drive applications, particularly when long cables are used. Indeed, the parasitic elements of the cable, along with steep voltage transitions due to semiconductor switchings, are responsible for the conducted electromagnetic emissions and high overvoltages on the motor terminals. Therefore, several specific PWM schemes have been proposed in order to reduce these phenomena without requiring large passive filters. However, strategies that reduce common-mode currents (mainly conducted electromagnetic emissions) tend to increase the overvoltages generated on the motor. This paper focuses on a new PWM strategy that reduces the common-mode currents generated by three-level inverters. It provides a control algorithm that makes sure that the motor overvoltages never exceed those of conventional strategies while improving the electromagnetic-compatibility performance of the drive.