Research On Hybrid Cascaded H-bridge Multilevel Converter With Energy Storage Module

With the development of the new energy industry and the pursuit of high efficiency of power electronics converter,large capacity multilevel converters have attracted more and more attention.Compared with the traditional converter,the hybrid cascaded converter can output more levels with fewer modules.This paper studies the control strategy of hybrid cascaded H-bridge converter to improve the performance of the converter.In this paper,the topology of hybrid cascaded H-bridge converter is introduced,and a simplified hybrid modulation strategy is proposed.On this basis,the strategy of injecting the instantaneous zero sequence component is designed,and the range of the instantaneous zero sequence component is calculated.In addition,the range of the instantaneous zero sequence component is further increased by the state reversal of the auxiliary module of the converter.According to the range of instantaneous zero sequence component,a strategy of injecting intermediate instantaneous zero sequence component is proposed,which extends the modulation of converter.In view of the inconsistency of the DC sources status of the H-bridge modules,which results the limit of the working time and power output capacity of the converter,this paper also designs the power control methods.The inner phase power control is realized by the opening angle of the main module,and the inter phase power control is realized by injecting instantaneous zero sequence components.Through these two power control methods,the redistribution of the power of each module of the converter is realized.In order to further take advantage of the hybrid cascaded multilevel converter,this paper proposes to use supercapacitors as the DC sources of the auxiliary module of the converter,which can achieve more output levels with less power supply.Based on the design of hybrid cascade H-bridge converter with energy storage module,the simplified hybrid modulation strategy is proposed when the capacitor voltage is unbalanced.In order to realize the effective regulation of the supercapacitor voltage,three methods for regulating the capacitor voltage of the auxiliary module are proposed,and the advantages and disadvantages of these three methods are analyzed.This paper also designs the grid-connected control strategy of the hybrid cascaded H-bridge converter and verifies its feasibility through simulation.The experimental platform of hybrid cascaded H-bridge multilevel converter is built.Finally,the software design of the experimental platform is finished,and the experimental verification of the proposed control methods is completed.