Comparison of voltage and current spectra using optimized forms of inverter pulsewidth modulation

Modern electrical drive technology tends toward application of alternating current machines (especially induction motors) for variable-speed drives. This in general requires providing of voltages with adjustable frequency and amplitude. This is achieved most advantageously with pulsewidth-modulated (PWM) inverters. After an overview of the basic concepts, the different optimization criteria important for practical applications are discussed. Of special interest are efficiency optimization and torque-ripple optimization. These two optimization criteria are treated in detail. Computer simulations for both cases and experimental results for efficiency optimization are presented and compared. Special attention is given to the various switching laws generating the PWM for the inverters and to the voltage and current spectra associated with them. The differences in drive dynamics optimization are also discussed.>