Comparison of Current Controllers that use Internal Feedback of the Controller PWM Signals to Produce a PWM-cycle Zero Average Current-error

The proposed carrier-based PWM current controller is described for a 1-phase PWM rectifier that uses a unipolar PWM signal generator to control the switching of the PWM rectifier. The current-error signal and an amplitude modulation depth signal form the input signal to the PWM signal generator. Similar to hysteresis-band controllers, changes in the slope of the current-error signal produces an automatic change in the PWM-cycle average of the PWM generator output signals. This PWM-cycle average is used to create the amplitude modulation depth signal, and the PWM-cycle current-error signal can be forced to be centred on zero as a result. Unlike hysteresis-band current controllers, the PWM generator input reference signal is compared with a sawtooth carrier signal and the PWM switching frequency is automatically fixed. The optimum peak-peak magnitude of the current-error signal relative to the magnitude of the carrier signal is discussed. The proposed current controller is examined using two different controller types implemented using analog circuit techniques. SPICE simulations and experimental results are used to examine the relative performances of the two controllers