A COMPARATIVE ANALYSIS OF LEVEL SHIFT & PHASE SHIFT MODULATION SCHEME FOR SERIES CONNECTED MLI FED BLDC SYSTEM

Multilevel inverter is one of the most recent and popular type of advances in power electronics. It synthesizes desired output voltage waveform from several dc sources used as input for the multilevel inverter fed BLDC drive. Brushless DC motors are widely used in variable speed drive application. The torque produced by the Brushless DC (BLDC) motors with trapezoidal back Electromotive force (BEMF) is constant under ideal condition. However in practice the torque ripple appears on the delivered output torque. Smoothness of variable speed drive operation is critical due to this torque ripple. The brushless DC motors uses power electronic switches for the commutation purpose, it creates the Harmonics in armature current. This paper proposes Cascaded H-Bridge Multilevel Inverter with current controller used to reduce the torque ripple and the harmonics. This paper highlights the several modulation schemes for MLI fed BLDC drive applications. The simulation results based on Matlab/Simulink are discussed in detail in this paper