Modeling and development of hybrid Cascaded multilevel inverter for Fuel cell power conditioning system

Abstract

In this thesis a Hybrid Cascaded MultiLevel Inverter HCMLI for newlinefuel cell powered system is analyzed by modeling various units of the system newlineperforming mathematical analyses and simulation studies Suitable control newlinestrategies are designed for the specific units of the system in order to achieve newlinethe desired operating performance Initially the mathematical model of a newline750W Proton Exchange Membrane Fuel Cell PEMFC is developed by newlinemodeling the open circuit output voltage of the PEMFC irreversible voltage newlinelosses in the PEMFC and formation of a charge double layer in the fuel cell newlinealong with thermodynamic energy balance in the PEMFC system The newlinemathematical model is experimentally validated and then used to study the newlinedynamic behavior of the PEMFC under different input conditions newlineResponse of a fuel cell to quick changes in load is slow A newlinepolyphase Interleaved Boost Converter IBC between the fuel cell and the newlineHCMLI is therefore required to reduce the input current ripples and also to newlineconvert low voltage high current input into a high voltage low current output newlineThe design methodology of IBC for fuel cell applications has been carried newlineOut Theoretical analysis has been performed and informative simulation newlineresults are provided in the thesis With low loss SiC diode and COOLMOS newlineswitches the efficiency of IBC has been improved Simulations have been newlinecarried out and it is found that the inductor current ripple is 7 80 and the newline6 input current ripple is 0 04 The output voltage ripple is 0 03 which is newlinewell below the designed ripple of 2 and output current ripple is 0 026 newlineHardware prototypes have also been developed to validate the results newlineDC output voltage of IBC is to be inverted to get the desired AC newlineOutput Hence this work presents the design of a single phase seven level newlineHCMLI based on transformerless topology It uses a hybrid approach newlineinvolving Silicon Carbide SiC power BJT and Silicon Si IGBT operating newlinein synergism newline newline