Implementation of a PWM Regular Sampling Strategy for AC Drives

The regular sampling technique offers a feasible basis for the microprocessor-control of inverters in pulsewidth modulated (PWM) ac drives. An implementation of this technique is presented for the speed control of an induction motor in the frequency range 5-105 Hz. Hardware and software design principles are outlined and discussed for an 8-bit microprocessor. Spectral analyses of the sampling technique with a sinusoidal modulating function and with a third harmonic added to this function are derived, with emphasis on the fundamental and dominant components. Experimental and computed results are presented for the motor control in steadystate, and for transient current and speed in closed-loop operation, with excellent correlation.