Mathematical analysis of hybrid topologies efficiency for PEM fuel cell power systems design

An efficiency mathematical analysis of the commonly used series and parallel hybrid topologies in distributed generation systems (DGS) is presented. The electrical architecture of the DGS consisting of PEM fuel cells, auxiliary storage devices and electrical loads allows regenerative power flow from the load bus. Criteria for a proper choice of the topology for a given load power profile are derived from the analysis and the inclusion of some practical considerations. A novel series-parallel hybrid topology for uncertain load power profiles is also disclosed. The proposed topology is compared with both series and parallel structures in terms of efficiency and number of converters under non-regenerative power conditions. The theoretical predictions of the mathematical analysis are verified by simulation using a Matlab/Simulink model that integrates a physical model of the PEM fuel cell with its control system, an electrical model of a battery with its state-of-charge regulator, and static models of DC/DC converters described in terms of efficiency.