Research On The Current Sharing Strategy Of Multi-phase Series-capacitor Interleaved Boost Converter

With the development of society,the demand for energy is increasing,and the energy transmission mode plays an important role.The non-isolated interleaved converter has become a research hotspot due to its high efficiency and low ripple.In addition to maintaining the advantages of the original interleaved connection,the series capacitor interleaved converter inherits the advantages of switching capacitance and staggered inductance technology,as well as the advantages of higher output gain,lower input current ripple,lower voltage resistance of the device,and higher efficiency.The average phase shift control is adopted in existing researches,which can obtain in the limited duty ratio n-times output voltage than traditional interleaved converter,phase current automatic partitioning,but other operating range and unable to maintain the features.It is not suitable for the practical application,which need wide range input.So a better control method is need to explore.In this paper,the working modes of capacitor series interleaved Boost converter are studied.the independent modes of two-phase structure and three-phase structure are analyzed in CCM mode,and the continuous working state in a switching cycle is calculated,so as to extract the mechanism of uneven flow of the converter.As an example,the research on DCM mode is based on the two-phase converter.Starting from the independent modes with different switching states,the continuous working states in a switching cycle are analyzed,and the principle of negative current generation in the converter is revealed.Based on the mechanism of uneven current,the unasymmetric duty cycle current sharing strategy is proposes for two-phase structures.Based on the principle of capacitor charge balance,by changing ratio of the charging and discharging time of the intermediate capacitor,starting with the switching mode of the current-unbalanced working interval,the unasymmetric duty cycle current sharing strategy is proposed by changing the conduction time and phase shift Angle of the switches.The two-phase current is balanced without adding any device or intermediate mode,and the output gain of a series capacitor Boost converter is double that of a conventional Boost converter in the full duty cycle range.As an example,the two-phase structure is analysis in DCM mode,the noncomplementary-conduction current sharing strategy and its boundary conditions are proposed to eliminate the negative current in a series capacitor interleaved Boost converter in DCM mode.In this paper,a charge balance current-sharing strategy is proposed for three-phase series capacitor interleaved Boost converter.In the two working regions where the converter cannot automatically balance the current,the charging and discharging current proportion relationship is obtained by adjusting the charging and discharging time based on the principle of capacitor charge balance,so as to achieve the goal of current balance between phases.The proposed current sharing strategy realizes phase current balancing without adding any devices or modes,and guarantees three times the output voltage gain of the conventional boost converter within the full duty cycle range,and maintains the continuity of duty cycle variation.By discussing the influence of inductance value on the current-sharing effect,analyzing the current stress and voltage stress of the devices,calculating the loss of the converter,the characteristics of the current-sharing strategy are evaluated.Finally,the implementation steps of the charge-balanced current-sharing strategy are explored to the multi-phase series capacitor structure,the application of strategy in the multi-phase topology is extended.It is implemented in the four-phase series capacitor interleaveing Boost converter,which verifies the effectiveness of the charge-balanced current-sharing strategy in the multi-phase concatenated capacitive structure.Finally,the proposed current sharing strategies are verified by the corresponding simulation and experimental platform.Experimental data and waveforms verify the correctness of the theoretical analysis and the effectiveness of the current sharing strategies.