Rseearch On Control Technology Of DC Current Bus Coupled Multi-Port Power Electronic Transformer

Power electronic transformer is an advanced energy routing equipment,which plays an important role in the future energy Internet.Multi-port power electronic transformer can support the flexible access of many different types of source,network,load,storage and other equipment to the power system,which is conducive to the realization of multi-energy complementarity and improve energy efficiency,so it has attracted more and more attention.However,some of the existing multi-port power electronic transformers which can realize medium-voltage AC grid connection have the problem of large volume,and the other part has the problem of port power decoupling.Therefore,it is necessary to propose a multi-port power electronic transformer which can realize the natural decoupling of the port and avoid the problem of large volume at the same time.DC current bus coupled multi-port power electronic transformer has the advantages of natural port decoupling and high power density,but the soft switching problem of hybrid dual active bridge limits the application of DC current bus coupled multi-port power electronic transformer.Further development is needed.In this thesis,taking the multi-port power electronic transformer with centralized current source converter as medium voltage grid-connected interface as the application scenario,a hybrid dual active bridge current bus coupled multi-port power electronic transformer architecture is proposed,the front stage is centralized current source converter(Current Source Converter),and the latter hybrid dual active bridge converter(Hybrid Dual Active Bridge).For the control of the front-stage current source converter,it is more mature.This paper focuses on the related technologies of the later stage hybrid dual active bridge converter.Firstly,the working principle of the centralized current source converter is introduced and analyzed,and several working modes of the centralized current source converter are discussed,and then a control technology applied to the centralized current source converter is introduced.that is,current outer loop current inner loop double closed loop control strategy and space vector modulation strategy.The effectiveness of the proposed control method is verified by simulation.Then it analysis the working characteristics of the hybrid dual active bridge circuit,analyzes the control strategies of the related circuits mentioned in the current research,puts forward the control strategy for the realization of the soft switching function of the two-way power transmission of the hybrid dual active bridge circuit,describes in detail the working principle and working mode of the hybrid dual active bridge circuit under forward and reverse power transmission.The effectiveness of the proposed control method is verified by simulation.Finally,the hardware experimental platform of multi-port power electronic transformer is built,which includes centralized current source converter and hybrid dual active bridge converter.According to the previous theoretical analysis,the experimental results verify the correctness and effectiveness of the proposed method.