Research Progress of Non-isolated High Step-up DC/DC Converters Based on Combinational Switched Impedance Network

With increasing concern on environmental pollution and shortage of traditional fossil energy, renewable energy including photovoltaics, fuel cells, and wind energy, etc. has drawn more attention to support future power system. However, fuel cells and photovoltaics cannot be directly connected to the grid without high step-up DC/DC converter due to the performance of low output voltage and high output current. A lot of topologies with high voltage gain and low current ripple have been developed to meet the demand of fuel cells and photovoltaics. This paper focuses on classification and comparative analysis on recent non-isolated converter topologies based on combinational switched impedance network including switched capacitor, switched inductor or coupled inductor. Loss breakdown analysis and efficiency comparison on different topologies are given with output power from 25% to 100% load while fuel cell output voltage varies from 105V down to 72V. Finally, the challenges and existing problems of current DC/DC converters used in fuel cells are pointed out in order for practical design.