Modulation technique for Four‐Leg Voltage Source Inverter without a Look‐Up Table

Three‐dimensional space‐vector modulation (3D SVM) has more popularity among the other modulation techniques of the four‐leg inverter due to higher DC‐link voltage utilisation. Sequencing schemes of the switching vectors in the 3D SVM are divided into Class I and II categories. Each of these classes itself has four kinds: (a) rising‐edge aligned, (b) falling‐edge aligned, (c) symmetrically aligned and (d) alternative sequence. In this study, implementation of the conventional 3D SVM technique in abc ‐coordinate for four‐leg voltage source inverters is simplified, while it can be so easily adopted in all kinds of sequencing schemes. Unlike conventional techniques, the proposed technique needs no switching vector determination and duty ratio calculation as well as reduces the computational burden. In this technique, turn‐on interval of the upper switches, in every switching period, is calculated without need of a look‐up table and complex equations. Applying the dead time by software is very straightforward in the proposed technique. In addition, by simplification of the proposed modulation technique, it can be applied to the three‐leg inverters. Simulation results in PSCAD/EMTDC environment confirm the validity and effectiveness of the proposed technique. Experimental results are also provided to confirm the validity of the new approach.