Comparative analysis of modular multilevel converter with different modulation technique for control of induction motor drive

Abstract

Modular multilevel converter (MMC) is an enhanced multilevel converter topology. It is widely used in research nowadays for its superior performance in high-voltage high-power applications. Modification is suggested in conventional MMC topology by connecting a single DC source to lower submodules This paper focuses on performance analysis of proposed configuration of MMC for control of induction motor (IM) drive with different modulation techniques. The modulation strategies used are sinusoidal pulse width modulation (SPWM) and selective harmonic pulse-width modulation (SHE-PWM). Simulation is carried out in MATLAB-SIMULINK with both techniques, to generate three level output by selecting suitable switching pattern. Initially, both the techniques are compared with same switching frequency of 500 Hz. Weighted total harmonic distortion (WTHD) is used as a performance indicator. Result shows that WTHD is less by employing SHE-PWM technique in comparison to SPWM technique. As WTHD is directly proportional to copper loss in IM, motor efficiency can be improved. Later, comparison is also carried out on basis of switching frequency required to eliminate same order of harmonics. Elimination up to 13th harmonic components requires frequency of 500 Hz in SHE-PWM and 1050 Hz in SPWM. As switching frequency required is almost double in SPWM, switching losses increases which is not desirable in high power application. Laboratory prototype was developed for the proposed configuration controlling IM drive. Experimental results were presented with both the techniques. SPWM pulses are generated using microcontroller DSPTMS320F2812. With advancement in microcontroller technology, SHE-PWM pulses are then generated with the help of microcontroller dsPIC33EP256MU810.