Switch-mode rectifier with digital robust ripple compensation and current waveform controls

For a switch-mode rectifier (SMR), the inherent existence of a double frequency output voltage ripple renders the contradiction between the input current waveform and voltage regulation control performances. In this paper, the approaches for the ripple compensation and the improvement of input current waveform control of SMR are presented. First, a robust ripple compensation controller is developed, such that the effect of double frequency ripple contaminated in the output voltage feedback signal can be cancelled as far as possible. It follows that the current command yielded by the voltage control loop will be nearly ripple-free. Then a current control scheme, which consists of a feedback controller, a command feedforward controller and a robust disturbance feedforward controller, is proposed to let the SMR possess improved robust input current waveform control performance. Theoretical basis, design and implementation of the proposed controllers are described in detail. All the designed controllers are carried out digitally using DSP TMS320C240. The measured results indicate that under well-regulated dc output voltage, improved input current waveforms with high power quality are obtained by the proposed control approach, and the results are rather insensitive to input voltage and load variations.