Two New Switching Methods to Speed Control of Induction Motor with Eleven Levels Inverter

By using usual industrial switching methods, two new multicarrier PWM (MCPWM) methods are proposed in this paper to improve the output voltage characteristics for eleven levels diode-clamped inverter. DC component and Even harmonic orders of the output voltage are totally eliminated in the proposed VFCBOD and COOD methods by applying the phase shift in the carrier wave (carrier-based); so total harmonic distortion (THD) and torque ripple are reduced. By using the both proposed methods, the number of pulses per cycle equally are distributed and increased the lifetime of the switches. In this paper, a full bridge has been series with each phase of eleven levels diode-clamped inverter to change the polarity of the voltage to produce more switching patterns to generate the specified voltage levels. Then, by determining suitable switching patterns, the inverter can be driven with the least of switches when there is a failure and finally increased the reliability of the whole system.