A Novel Multilevel AC/DC/AC Single phase to Three Phase Converter for Induction Motor Application

Power electronic inverters are widely used in various industrial drive applications. To overcome the problems of the limited voltage and current ratings of power semiconductors devices, some kinds of series and/or parallel connections are necessary. Recently, the multilevel inverters have received more attention in literature due to their ability to synthesize waveforms with a better harmonic spectrum and to attain higher voltages. They are applied in many industrial applications. In this concept we proposed development of single phase AC/DC/AC converter using three-leg inverter. A uniform fixed switching frequency method of current control for both AC/DC and DC/AC converter stages has been proposed. A multiple control loop is used to control the input AC current and DC link voltages of the AC/DC converter and a cascaded H-bridge multilevel inverter (CHBMLI) is used to obtain the multilevel AC output voltage for the DC/AC inverter. The ramp comparison method of current control facilitates the fixed switching frequency operation of the converter to provide uniform switching cycle for all the switches of the AC/DC converter. A unipolar multi-carrier PWM has been used for the cascaded Hbridge multilevel inverter to yield the uniform and fixed switching frequency operation for the DC/AC inverter. KeywordsCascaded multilevel inverter, multi-carrier unipolar modulation, ramp comparison control.