Analysis of ripple current, power losses and high efficiency of DC–DC converters for fuel cell power generating systems

Abstract

The voltage produced by the fuel cell (FC) device is unregulated and varies from 0.4 to 0.8V on full load to no-load respectively. When these devices are used in high voltage applications the DC–DC boost converters are required to boost the low FC voltage. In order to get the high voltage the high voltage gain with less duty cycles is preferred to ensure less conduction losses and device stresses. The FC devices are high current low voltage devices and draw the current with larger ripples in it. The conventional Boost converters are less efficient to integrate directly with the FC devices. For high performance FC applications employing multi phase interleaved converter topologies have gained much interest in recent years. In this paper the different DC–DC Converter topologies i.e., Boost Converter (BC), Multi Device Boost Converter (MDBC), Multi Phase Interleaved Boost Converters (MPIBC) and Multi Device Multi Phase Interleaved Boost Converters (MDMPIBC) are analyzed with respect to the ripple current reduction which is drawn by the fuel cell (FC) stack. Further, the total converter power losses are classified and analyzed in detail for individual converters under study. A 6000W, 180V PEMFC stack is developed in MATLAB/SIMULINK and the power converters under study are analyzed with respect to the their performance parameters like ripple current, size of passive components, power losses and system efficiency. The converters are compared for a constant rated fuel cell current flow through them, a fixed DC-Load across the converter is connected to make sure that the converters operate under rated fuel cell current conditions. All the converters performance are compared to each other and the superiority of multi phase and multi device technology is emphasized and the simulation results demonstrates that the MDMPIBC converter topologies are more efficient than the other converter topologies employed in high performance applications.