Protected Pulse Width Modulation in Nine-Switch Inverter

The nine-switch inverters with two sets of three phase terminals are one of the improved topologies and in place of the back to back twelve inverters which are interested for many authors in recent years. This inverter is used by two modes of pulse width modulation: constant frequency (CF) and different frequency (DF). One of the disadvantages of using conventional methods, the Shoot-through probability in the arms of inverter, which leads to a decrease in circuit reliability. This paper proposes a new modulation method that by using two auxiliary carrier waves in addition to the main carrier wave generates gating signals of nine-switch inverter. In this method, adjustable three phase voltages are generated in inverter’s terminals, without any shoot-through in inverter’s legs. The new protected modulation doesn’t need to realize the load currents direction and it generates simple and protected gating signals such that the quality of terminal waveform has considerable improvement respect to other methods. These performances of the proposed modulation are verified by the Matlab simulations results.