A direct double-frequency ripple current control in a two-stage high-frequency-link (HFL) based fuel cell converter that can achieve low-frequency ripple free input current without using large electrolytic capacitors is provided. To eliminate the double-frequency ripple current disturbance introduced by the single-phase inverter load, a proportional-resonant (PR) controller is developed to achieve an extra high control gain at designed resonant frequency. This high gain can be viewed as the virtual high impedance for blocking the double-frequency ripple energy propagation from inverter load to fuel cell stack. More particularly, the proposed control system can realize the utilization of all capacitive ripple energy sources in the system by regulating all the capacitors to have large voltage swing and the voltage swing is synchronized to keep real-time balancing of the transformer primary-side and secondary-side voltages. As a result, the zero-voltage-switching (ZVS) operation for all switching devices in the dc-dc stage can be guaranteed.
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