Research On Dual-Buck High Frequency And High Efficiency Bidirectional Grid-Connected Inverter

Energy storage unit can effectively suppress the power fluctuation of distributed new energy grid-connected power generation system,increase generation revenue or reduce electricity cost,but the efficiency and power density of its supporting converter system need to be further improved.Among them,the bidirectional grid-connected converter,as an energy conversion device between energy storage system and power grid,needs to further improve efficiency,power density and safety and reliability.In this paper,an interleaved dual-Buck full bridge converter topology is proposed,and detailed research work is carried out from the aspects of modal composition,circuit characteristics,parameter optimization and control strategy.The specific work of this paper is as follows:(1)A novel interleaved dual-Buck full-bridge bidirectional converter is proposed to overcome the hidden trouble of traditional H-bridge inverters.It has the characteristics of low inductance current ripple and low current stress of switch.In this paper,based on the study of converter inversion and rectification principle and circuit characteristics,the common-mode current model of interleaved dual-Buck full bridge bidirectional converter is studied.In addition,the state equation of the proposed converter under inversion and rectification states is established by time domain modeling analysis method,and the mathematical transfer function of the converter is obtained,which provides a theoretical basis for the design of its controller.(2)A multi-objective parameter optimization design method for bidirectional grid-connected converter is proposed.The method considers the filter performance requirements both inversion and rectification states and the coupling relationship between filter parameters.The optimal combination of parameters is obtained by setting the priority of filter performance index.In addition,on the basis of parameter optimization design,the loss of the proposed topology in two states of inversion and rectification is modeled and studied.(3)A design method of controller based on system model compensation is proposed.This control method is based on the Bode diagram of the inversion state.On the one hand,it can eliminate the resonance peaks in the system and improve the stability of the system.On the other hand,it can improve the phase margin and amplitude margin of the system and improve the static and dynamic performance of the system.At the same time,the root locus diagram is used to design the controller of the system in the rectification state.Finally,under the premise of very small filter inductance,a high stability of the bidirectional power conversion process is achieved.(4)A 5k W experimental prototype based on Si C power device is built,and the detailed experimental research and verification of inversion and rectification are carried out respectively.The power density of the prototype reaches 26W/in~3.The maximum efficiency of the prototype is 98.8%and 98.66%in the inversion state and the rectification state,respectively.The THD of the full-load grid current is 2.7%and 4.5%respectively.The common-mode current in the inversion state is less than30 m A.The correctness of the theoretical analysis and the rationality of the parameters and controllers are verified.