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This paper presents a new topology for current fed push-pull-based DC-DC converters employing a low-voltage Fuel Cell (FC) as energy source. This DC-DC converter can be used in Single-Phase Distributed Generation (DG) systems. The work aims presenting new solutions for two important issues regarding fuel cells in DG applications. The first issue is related to the low-frequency ripple in the FC output current when the FC supplies a single-phase power conditioner. It is strongly recommended to minimize the low-frequency FC current ripple in order to increase its lifecycle and performance. Therefore, a simple and effective control strategy has been applied to sharply attenuate such current ripple. The second issue concerns the operation of the current fed push-pull DC-DC converter. An auxiliary circuit is proposed to protect the power switches against the overvoltage due to the transformer's leakage inductance. The auxiliary circuit regenerates also the energy stored in a clamping capacitor, thus improving the overall converter efficiency. Moreover, the auxiliary circuit allows implementing the DC-DC converter soft-start. Simulation and experimental results are provided for a 5 kW converter prototype, demonstrating the feasibility of the proposed solutions.
Date of Conference: 14-17 March 2010