Optimum input-filter-capacitor sizing for fuel-cell based single-phase inverter for current-ripple mitigation

Most single-phase inverters, being sourced by fuel-cell stacks (FCSs), subject the stacks to reflected low-frequency (120 Hz) current ripples that ride on average dc currents. The ripple current impacts the sizing and efficiency of the FCS. As such and typically, a passive or active filter is required at the input of the inverter (or output of the FCS) to mitigate the ripple current. Towards that end, this paper outlines a guideline to choose the optimum size of a passive input-filter capacitor for a fuel-cell-based power system from the standpoints of the overall system energy density and cost. Detailed case-specific simulation results, based on an analytical approach, are provided to illustrate key issues for both unity-power-factor as well as harmonic loads.