Research On DC Microgrid Control Method Based On Sliding Mode And DBS

The energy shortage and the environmental degradation have become increasingly significant,so human beings turn to the road of seeking new energy.New energy research in the field of electric power is getting more and more in-depth,and the microgrid has also received attention.The microgrid can act as a"bridge"to connect the distributed power supply and the distribution network so that the grid connection problem of new energy generation can be solved.There are many kinds of DC units such as photovoltaic units,energy storage units and DC loads in the microgrid,so the DC microgrid will obviously be better than the AC microgrid.Among them,the DC microgrid has become a current research hotspot because of its high reliability,high conversion efficiency,easy control and less line loss.Firstly,this paper summarizes the research status and related control technology of DC microgrid.Based on the introduction of the DC microgrid structure,a DC microgrid structure composed of two groups of photovoltaic power generation units,battery energy storage unit and resistive load is constructed as the research object of this paper,and the mathematical models of photovoltaic cells and batteries are established and the output characteristics and interface circuits are analyzed.Secondly,aiming at the DC microgrid in island mode,a control method of DC bus signal hierarchical is studied.This control method divides the operation mode into four layers with the bus voltage as the reference value,and the corresponding working mode of each layer is different.Besides,the control scheme of each converter is introduced in detail.The droop control and MPPT control are used for photovoltaic cells,the droop charge and discharge control and the limited power charge and discharge control are used for the storage battery,then the simulation verification is carried out.The results show that the control method can realize the independent switching between different working modes,and guarantee the power balance and bus voltage stability.Finally,the structure of the grid-connected controller-bidirectional DC/AC converter for DC microgrid is analyzed.Aiming at its typical nonlinear characteristics,an adaptive backstepping sliding mode control method for the controller design is studied.The coordinate transformation process of its mathematical model is expressed by three state quantities ofx₁,x ₂,x₃,and then the adaptive backstepping sliding mode controller is designed,and finally the simulation verification is carried out.The results show that the method can track the uncertain parameters of the system very well.And the response speed is fast,while also improving the robustness of the system.The paper contains 43 figures,table 6 and 87 references.