| It is of great significance to configure an equalizer for a battery and supercapacitor pack to solve problems such as reduced security,shortened service life,and declined output power caused by voltage imbalance.Traditional independent equalization method requires more switches,inductors,transformers and other components,resulting in larger circuit volume.The integrated equalization method integrates the equalization circuit into the DC-DC circuit for charging/discharging the battery/supercapacitor pack,thus effectively reduces the volume of the equalizer.In order to further reduce the volume of integrated equalization equalizer,a design method of voltage equalization of battery/supercapacitor by current/voltage ripple in DC-DC converter is proposed in this thesis.The basic operation characteristics of two typical equalization structures based on multiwinding transformer and voltage multiplier are analyzed,and the external circuit conditions for realizing the equalization function of the two kinds of equalization structures are summarized.Secondly,the thesis analyzes the basic operation mode of a DC-DC converter.When the DC-DC converter is running,the current ripple and voltage ripple will be produced on the inductor and capacitor respectively,corresponding to the drive condition of multiwinding transformer and voltage multiplier.Therefore,the method using the current ripple and voltage ripple to achieve balance of battery/supercapacitor pack is proposed.In order to verify the feasibility of equalization using current ripple,this thesis firstly integrates the equalization structure based on multi-winding transformer into the Boost discharge circuit of battery pack by using current ripple,and proposes an integrated discharge equalizer based on Boost converter.The inductor of the Boost converter is reused as the primary inductor of the multi-winding transformer,which effectively reduces the size of the equalizer.The feasibility of integrated discharge equalizer based on Boost converter is verified by theoretical analysis and battery discharge equalization experiment.In addition,this thesis further applies the current ripple equalization method to the hybrid energy storage device composed of battery and supercapacitor,and proposes an integrated equalizer based on bidirectional Sepic-Zeta converter.A bidirectional Sepic-Zeta converter is used for energy exchange between the battery and supercapacitor pack.The battery pack and supercapacitor pack both are balanced based on multi-winding transformer,and the two inductors in SepicZeta converter are reused as the primary inductors of the two multi-winding transformers respectively.The feasibility of integrated equalizer based on bidirectional Sepic-Zeta converter is verified by theoretical analysis and experiment.In order to verify the feasibility of the method of using voltage ripple to achieve equalization,this thesis uses voltage ripple to integrate the voltage multiplier into the Cuk circuit,and proposes an integrated charging equalizer based on Cuk converter.When charging the battery pack,the circuit can charge and balance the supercapacitor pack.The feasibility of integrated charging equalizer based on Cuk converter is verified by theoretical analysis and supercapacitor charging equalization experiment. |
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