| Recent years,with the depletion of fossil resources and the development of new energy,electric vehicles(EVs),as a part of the new energy industry,have naturally attracted widespread attention from industry and academia all over the world.Among them,the charging technology is one of the key points of its research for EVs.Moreover,onboard charging technology has been studied by more and more researchers due to its flexibility and convenience.In the onboard charging system,the high and low frequency charging and discharging ripple current of power/auxiliary batteries will cause temperature rise and result in shorter battery life.Therefore,an isolated bidirectional DC-DC converter with low input/output ripple current is required as the power interface between DC bus and power/auxiliary battery.In addition,a pulsating power at twice the frequency of the grid voltage is generated in the DC bus side of the integrated onboard single-phase PWM rectifier charging system,which will generate low frequency(second-harmonic)ripple current.Therefore,to suppress the high and low frequency ripple current generated in the single-phase integrated onboard charging system is of great importance.Firstly,an isolated bidirectional DC-DC converter with low input/output ripple current as an interface between DC bus and power/auxiliary batteries is presented in the integrated onboard charging system.Compared with the traditional dual active bridge,the converter can achieve lower charge-discharge ripple current,and all power switches can realize ZVS under a full load range.In this paper,the operating principle,parameter design and soft switching range of the bidirectional DCDC converter are analyzed in detail.Finally,experimental prototype is developed and the experimental results are used to validate the performance and feasibility of the converter.Secondly,in order to suppress the low-frequency ripple current in the DC side during the integrated single-phase PWM rectifier charging,this paper proposes the inductive energy storage scheme of multiplexing machine windings.The higher integration can be achieved of the proposed method without additional hardware circuits.In this paper,the principle of the proposed low-frequency ripple current suppression methods are analyzed in detail.Finally,the experimental results are used to verify the correctness and effectiveness of the proposed converter and its control methods.Finally,to solve the problem of excessive current stress in low-frequency ripple suppression method based on inductive energy storage,this paper proposes a capacitive energy storage method based on multiplexing auxiliary power,which can effectively alleviate the device pressure in active filter with inductive energy storage.Similarly,the proposed method can achieve higher integration and lower cost without additional devices.In this paper,the principle of the low frequency ripple current suppression method is analyzed in detail.Finally,the experimental results of the charging system are used to verify the correctness and effectiveness of the proposed method. |
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