AC/DC converter based on instantaneous power balance control for reducing DC-link capacitance

In AC/DC converters for on-board chargers, the DC-link capacitor on the output side in a power factor correction (PFC) converter uses aluminum electrolytic capacitors in order to obtain a large capacitance with low voltage ripple and small size. Therefore, it is necessary to reduce the capacitance when using film capacitors without increasing the size of the converter in order to realize a capacitor with a long lifetime. This paper describes a control strategy for the AC/DC converter with a reduced DC-link capacitance. This strategy is based on the instantaneous power balance of a PFC converter and a DC/DC converter and controls the AC-side input current without being affected by the large ripple voltage of twice the utility line frequency owing to the reduction in the capacitance. The simulation and experimental results are presented to validate the proposed strategy, and it is confirmed that it is possible to reduce the DC-link capacitance to one-fifth when compared with the conventional AC/DC converter without additional circuits.