A current controller for 1-phase pwm rectifiers using real-time internal feedback of the pwm controller signals

A carrier-based unipolar PWM current controller for 1-phase PWM rectifiers is described that uses a PWM signal feedback loop with a low pass filter to force the current-error to be centred on zero. The proposed controller is intended for low cost discrete electronics and replaces the PI controller traditionally used to lower the current-error signal. A sawtooth carrier signal is used to synchronize the PWM waveforms and to obtain a constant switching frequency. A current-error signal and an amplitude modulation depth signal is obtained from the filtered PWM signal feedback and can be designed to take into account switch overlap and signal transmission delays. The filtered PWM signal more accurately represents the converter PWM output voltage waveform and, with an appropriately designed low pass filter, forces the current-error signal to be centred on zero over a PWM cycle. This signal feedback is internal to the controller and is illustrated using a second-order Butterworth filter. The maximum peak-peak ripple of the current-error signal is used as a design guideline for deciding the appropriate gain constant in the controller current feedback loop. The proposed controller has a performance comparable to PI and adaptive hysteresis current controllers that are more complex in structure to obtain the same performance. SPICE simulations and experimental results are used to demonstrate the controller operation