Digital adaptive control approach to dynamic response improvement for compact PFC rectifiers

Abstract:
A simple digital controller capable of fast output voltage regulation of power factor correction (PFC) rectifiers with minimal output capacitance is presented in this paper. The method is based on the use of two controllers for the outer voltage loop: an inter-line-cycle controller with slow dynamic responses takes care of steady state operation and small deviations from the set point while a fast intra-line-cycle corrector observes any abrupt change in the load current, and accordingly force the power command level to avoid significant overshoot or undershoot at the output voltage. Unlike existing studies, both controllers are derived based on the idea of balancing the input and output power rather than minimizing output voltage errors, and as a consequence allow faster responses and globally stable operation. The practicality of the proposed controller is shown on a 200W four-level bridgeless PFC prototype with a switching frequency of 143kHz. Experimental results confirm that performance is significantly improved as compared to conventional controllers.