Analysis of Vector Estimating Modulation Method to ‎Eliminate Common Mode Voltage

The problem of common mode voltage in inverters can be considered as a major issue which leads to ‎motor bearing failures. To eliminate these voltages, proposing some methods seems to be necessary. This ‎paper has a comparative study on estimating modulation methods of eliminating common mode voltage. ‎The main idea of these methods is based on generation of reference vector with nearest vector/ vectors ‎with zero common mode voltage. Depending on the number of delivering nearest vectors, there are two ‎estimating methods. For the reference method, reference vector is synthesized only by the nearest vector. ‎But for the proposed method, the reference vector is synthesized by more than one vector. Dwell time ‎calculations of these vectors are based on the distance between the afore-mentioned vectors and the ‎reference vector. In this paper, some characteristics such as linear relationships among output voltage and ‎modulation index, and also total harmonic distortion of output voltage and stator current are considered. ‎Finally, it is concluded that the new method has more advantages such as more linear relationships and ‎lower THD of current with respect to the reference method.‎