Active Ripple Energy Storage Circuit with Extended Hold-Up Time Capability and Minimum Capacitance for High Power Dense Rectifiers

Industrial single-phase rectifiers typically require a bulky passive energy storage device to both handle the double-line frequency power ripple and to maintain operation during AC line drops out, affecting power density and lifetime. A possible approach allowing a strong reduction of the volume of the required storage device is the adoption of active energy storage systems (ARES). This is normally implemented through a bi-directional converter interfacing the PFC output bus and an auxiliary storage capacitor, allowing a wider voltage span across this last and a wider exploitation of energy flow needed to compensate for the ripple power/voltage. Among possible ARES topologies, the buck (from the bus) type is popular for its low component count and voltage stress, but it has poor hold-up time capability due to the lack of the buck/boost capabilities from the storage. In this paper, a buck/boost ARES circuit is proposed, with extended hold-up time capability for high power dense rectifiers. Dual voltage loop regulation method based on a 2-pole 2-zero and a resonant controller is considered for the buck/boost mode from the bus (i.e., compensation of the bus voltage ripple), whilst a 3-pole 2-zero controller allows to sustain the PFC bus voltage during AC line drops, i.e. buck/boost mode from the storage. The proposed ARES solution has been fully validated through simulations. A 2 kW prototype has been developed, based on SiC power MOSFETs and digital control, to confirm the effectiveness of the solution and validity of the simulation results.