We describe an energy-efficient, fuel cell (FC) powerconditioning system (PCS) for stationary application, which draws practically zero switching-ripple current from the FC and can potentially meet the $40/kW cost target. The PCS consists of a zero-ripple boost converter (ZRBC) followed by a soft-switched and multi-level high-frequency (HF) inverter and a single-phase cycloconverter. The zero-ripple input inductor significantly reduces the input current ripple which may be necessary to enhance the long-term durability of the fuel cell. A new phase-shifted sine-wave modulation of the multi-level high frequency inverter is proposed which results in the zero voltage turn-on (ZVS) of all four switches (without the use of any auxiliary circuit components). For such a sine-wave modulation technique a > 90 % ZVS range is obtained from 25% of the full load to full load. Further, the line-frequency switching of the cycloconverter (at close to unity power factor) results in extremely low switching losses. The intermediate high voltage DC (HVDC) bus facilitates the inclusion of power systems based on other forms of alternative-energy techniques. A cost effective 1 kW prototype of the proposed PCS is built, which achieved a high overall efficiency. We present a detailed description of the operation of the PCS along with its key features and advantages. Finally, experimental results showing the performance and operation of the PCS are demonstrated.

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