Research On New Control Strategy Of DC Microgrid Based On Droop Method

With the energy shortage and environmental pollution problems become increasingly serious,the new structure of micro grid which is different from the traditional large power grid appears.It can not only solve the islands,mountains and other regions of the power supply problems,but also integrate distributed energy and improve energy use rate.Compared with the AC microgrid,the DC microgrid does not need to consider the phase and frequency,but the related research is still at the initial stage.Therefore,this paper studies the new control strategy of DC micro-grid based on droop method,and makes a contribution to the development and application of DC micro-grid.Firstly,the concept and research significance of DC microgrid are introduced.The common control strategies are described and the advantages and disadvantages are analyzed.Then the principle of traditional droop method and two main shortcomings are introduced.Then,according to the structure of DC microgrid used in this paper,the mathematical models of PV cells and battery are deduced,and the respective control modes are given.According to the derived mathematical formula,the models are established in Matlab/Simulink,and the control strategy is verified by simulation.Next,two different new droop methods are proposed.The first new droop method introduces the battery remaining capacity SOC into the droop coefficient.When the batteries run in parallel,the battery with large remaining capacity outputs more power,and finally the remaining capacity and output power of each battery are equal.The droop coefficient of the second new droop method is adjusted by the current loop to improve the current unbalance of the parallel converters using the traditional droop method.Using the voltage loop to raise the reference voltage,so the shortcoming that the traditional droop method leads to bus voltage drop more can be overcomed.And the simulation of two new droop methods proposed by Matlab/Simulink platform is carried out.Finally,the prototype based on exchanging adjacent converter information is made and tested.After making and welding PCB,DSP28335 is used to finish control part,and the prototype is debugged to confirm the correctness of theoretical analysis.