Common-Mode Voltage Mitigation Technique in Motor Drive Applications by Applying a Sampling-Time Adaptive Multi-Carrier PWM Method

Common-mode voltage (CMV) in electric drives causes leakage current causing consequently EMI problems, loss and reduction of their components’ lifetime. Several solutions have been proposed which usually lead to higher cost because additional components are used. This paper is focused on the mitigation of the resulting CMV produced by the operation of the VSD by means of a specifically designed PWM method. The proposal is based on the analysis of the CMV harmonic spectrum using the Fourier analysis. The CMV mitigation is achieved by modifying the time-shift displacement of the carriers each sampling time considering a multi-carrier PWM technique. The resulting method has been evaluated in a down scaled experimental setup and it is easily implementable on mostly off-the-shelf mid-range micro-controller control platforms.