Research On Bi-directional DC/DC Converter For AC/DC Hybrid Microgrid System

In current society,with the continuous improvement of people's living conditions and the deepening of the degree of industrialization,the electricity consumption of load is also increasing,and the pressure of the large power grid is increasingly evident.At the same time,the coverage of the large power grid is still insufficient in remote areas and places with special geographical locations.The distributed power supply compensates for the shortcomings of the large power grid because of its advantages of not being geographically limited;the proposed AC/DC hybrid microgrid technology has made the distributed power supply more widely used.In island mode,the AC/DC hybrid microgrid which improves local living conditions can be used in areas where the grid cannot cover.In grid-connected mode,the AC/DC hybrid microgrid can be used in areas with large loads which have such advantages as relieving the pressure of the large power grid,ensuring the normal operation of the load,peak shaving and valley filling.In this thesis,the energy storage department in AC/DC hybrid microgrid system is studied.In order to solve the problem of power changing of PV and load,the energy storage system which composed of battery and bidirectional DC/DC converter is proposed to maintain the stability of DC bus voltage.After the analyzing of characteristics of various converters,a two-phase bidirectional DC/DC converter is finally adopted.The two-phase power switches of the converter are turned on in turns,which can not only reduce the volume and power loss of the inductor but also decrease the input and output current ripple.The charging and discharging principle of the battery is analyzed in this thesis,and the mathematic model of battery is established.Then,the simulation model of energy storage department is built in MATLAB/Simulink.The parameters of inductor and capacitor were calculated.And the auxiliary circuits,driving circuits,sampling circuits and the other hardware circuits were designed and an experimental platform was set up.FPGA EP8C25Q240C8 N and DSP TMS320F28335 were applied as the controller which function is to control the charging and discharging of battery.The software flow pattern is designed.The experimental results further verify the rationality and feasibility of the simulation.