Bidirectional Converter-Based Hybrid Capacitor for Pulsed Power Suppression with 99% High Efficiency

The power fluctuations of pulsed power loads cause serious disturbances to the power system. To suppress the pulsed power, bulk passive capacitors are required, leading to significant increase in capacitor volume and weight. Although adopting active capacitor can reduce the capacitance, another high-power power converter with multiple power conversion stages must be used, which degrade the efficiency of the power system dramatically. In this paper, a hybrid capacitor is proposed for pulsed power suppression to overcome drawbacks of both passive and active capacitors. The proposed hybrid capacitor allows a trade-off between volume and efficiency by adjusting the ratio of active to passive capacitors. The active capacitor in this scheme is essentially a bidirectional converter and is connected in series with the passive capacitor. The voltages of the active and passive capacitors fluctuate in reverse with the same amplitude to keep the DC bus voltage constant. The capacitance voltage can fluctuate widely, which can reduce capacitance, size, and volume of capacitors. What's more, as the active capacitor only needs to handle partial pulsed power, its power rating and loss is much lower than conventional active capacitors. The structure derivation, operating principle, design considerations, and control strategy are analyzed in detail. Finally, a 5kW-peak power experimental demonstration is built to verify the effectiveness and feasibility of the proposed method.