Study On Multi-port Converters For Micro-grid Based On Power Electronics Module Optimization Theory

DC micro-grid is with higher power transmission efficiency and flexibility compared to AC distributed network,and it is gradually becoming a complementary power distributed mode for AC distributed network.Therein,DC-DC converters are the key technology of the DC micro-grid.Normally,traditional converters are with conversion features of multi-stage and single-input-single-output,which results in disadvantages of complex structure and control,and then it cannot satisfy the requirements of multiple power supplies and multiple load distributed DC micro-grid.Besides,there are still some obvious problems such as large input current ripple and low voltage gain.To solve above problems,the main contributions of this dissertation are as follows.(1)To satisfy the special requirements of multi-port converters in micro-grdi,power electronics module optimization combination theory is firstly proposed in this dissertation.Therein,detailed design and construction process of multi-port converters are presented conducted based on optimal combination theory,which can well design high-efficiency singlestage multi-port power converter.(2)To solve the stable problem of micro-grid caused by output voltage ripple of multiport converters,a series of non-isolated single-stage multi-port converter topologies with few components and high power density are developed,based on the proposed design method,to meet the high-performance requirements of DC micro-grids.In order to further suppress the ripple of the converter,three ripple-free converters are artificially designed under the guidance of design optimization theory,which finally results in three single-stage multi-port converters with ripple suppression function.Detailed performance verification of the converters are conducted,including operational analysis,parameter design and simulation verification.(3)To resolve the limited output voltage and input current ripples problems of multi-port converters in micro-grid,this dissertation deeply reviews the state of the art of design theory of high voltage gain converters,and then combines these theories into the proposed method,then,a series of multi-port converters with wide voltage range and zero input current ripple are presented.In order to verify the performance and feasibility of the proposed converters,detailed topology derivation,theoretical analysis,simulations and experiments are conducted to validate their correctness and applicability.(4)To make up the shortage of single waveform of multiport converters in each port,this dissertation proposes a novel mathematical operation control strategy for the designed converter.Under this control strategy,the converter can not only achieve multi-level DC output,but also output a variety of voltage waveforms(sine,triangle,rectangular,pulse,etc.)via a single converter.Taking one of the converter as a typical case,the corresponding control strategy is designed,then,simulation and experiment prototype are set up.Finally,the effectiveness and feasibility of the converters are well validated via experimental results.In a word,the converter topology designed from the proposed method can well satisfy the requirements of DC micro-grids,which well validate its effectiveness.