Energy-based digital control of a ripple correction circuit of an unity-power-factor AC/DC converter

An unity-factor AC/DC converter in single-phase has a double-frequency ripple component in the input power. Usually a large output capacitor is inserted to reduce the component. However it is not desirable for efficiency and aging. It is necessary to develop an alternative energy-storage circuit to absorb the ripple power. This paper proposes a control method of a ripple correction circuit which is a bidirectional chopper in parallel with the small output capacitor and absorbs the ripple current. The control scheme is new and applied not only to the correction circuit but also to the main circuit because the idea is based on the energy balance equation between the input and output powers. The proposed method is validated through simulation with Saber and experiment with a FPGA digital control circuit.