| An energy-efficient, fuel cell (FC) power-conditioning system (PCS) for stationary application, which reduces the variations in the current drawn from the FC and can potentially meet the {dollar}40/kW cost target is discussed in this work. 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 ZRBC comprises a new zero-ripple filter that significantly reduces the input current ripple, thereby potentially enhancing the long-term durability of the fuel cell. A new phase-shifted sine wave modulation of the multi-level HF 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 greater than 90% ZVS range is obtained. 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 5 kW prototype of the proposed PCS is built, which achieves a high overall efficiency of > 90%. A detailed description of the operation of the PCS along with its key features and advantages is presented. Finally, experimental results showing the performance and the operation of the PCS are demonstrated. |
