Offline-Based SVM Techniques to Reduce Common-Mode Voltage of Six-Phase Cascaded-CSI

In this paper, space vector modulation (SVM) techniques are developed to operate the six-phase current-source inverters (CSI) while reducing the common-mode voltage (CMV) content associated with the switching of semiconductors. The CMV issue is a severe issue of high-power electronics converters that causes damage to electric drives and shortens their life span. Since the null states are the main contributor to CMV in SVM schemes, an optimum offline selection method is proposed in this paper for all the presented techniques. The SVM techniques discussed in this proposal are built on the renowned vector space decomposition (VSD) method. The modulation in all the techniques is based on studying the resultant CMV associated with all the possible switching states and then selecting the states that produce the lowest magnitude of CMV. Accordingly, the optimum sequences for the switching patterns are introduced, and the utilization of the dc-link current for each scheme is analyzed. A quantitative comparison is conducted to evaluate all the proposed schemes in the generated CMV in peak and RMS values versus the modulation index and load power factor range. A laboratory prototype is presented, and the experimental results to validate the proposals are illustrated with a detailed discussion.