Research On Converter Technology In DC Micro-grid

As the situation of energy and environment become worse,more attention were paid to the efficient use of the clean energy,many clean energy are used in the form of distributed power,and micro-grid system is an efficient way to connect the distributed power to the grid.DC micro-grid is a typical form of micro-grid compared with AC micro-grid,there is no frequency,phase and other factors in the bus of the micro-grid,making the energy storage unit and micro-power easier to connect to the bus in the DC micro-grid,so the DC micro-grid is studied in this paper.In this paper,the background,the significance and the concept of micro-grid were described,and the status and key technologies of DC micro-grid were introduced.Then the structure of DC micro-grid,the principle of micro power operating,hardware configuration,system control method which commonly used in DC micro-grid system was described,and the principle of energy storage,characteristics of energy storage in storage unit commonly used was introduced,and then the importance and the performance requirement of the converter were analyzed.The converter in energy storage system was studied and designed: the principle of bi-directional DC-DC converter operating and the basic topologies was introduced,and the parallel technology in DC converter was simulated and analyzed,then the medium power interleaving bidirectional DC-DC converter was designed,including the converter protection technology needed in micro-grid system,isolated sampling,driving,circuitry detection,and the control strategy based on the battery charge and discharge characteristics and so on,then a prototype was produced to verify the theoretical characteristics in different patterns.The converter in micro-power system was studied and designed: the shortcomings of traditional full digital converter was analyzed,and then a new hybrid digital-analog converter was proposed,the advantages in efficiency,power density,cost,control effects of the hybrid analog-digital controller was analyzed,then a prototype was produced,the validity of the advantages of digital-analog hybrid control was verified.The algorithm of micro power system based on solar system was also studied in this paper.The simulation model of photovoltaic cell were built,the characteristics of PV cell was simulated and analyzed,then an improved MPPT method to improve the response characteristics was proposed based on the characteristics of a photovoltaic cell,this method was based on the slope of the PV curve,at the same time,an improved MPPT method according to the harsh environment based on the slope curve was proposed,the method can improve the stability in harsh environment efficiently,then a simulation model in the MATLAB / Simulink environment was built to verify the advantages of the improved method in both response characteristic and steady state stability,Finally,the validity of the algorithm was verified in the digital-analog hybrid converter prototype.