Research On Sliding-mode Variable Structure Control Of DC Microgrid

With the distributed generations such as solar,wind,biomass power generation booming,people have been paying more attention to grid-connection.To avoid the impact to grid when distributed power system connecting to grid,a conception of micro-grid was proposed,which means making the distributed power systems form micro-grid when connecting to grid.DC micro-grid become the research hot spot with the advantages of high reliability,high conversion efficiency,easy to control and less line loss.In DC micro-grid,the DC bus voltage is the sole indicator reflects the power balance of the whole System.Controlling the DC bus voltage stability can make DC micro-grid operate steadily.Bidirectional converter is used to interface a DC micro grid to utility grid,realize the bidirectional power flow control and DC bus voltage regulation,two stage bidirectional converter has the advantages larger voltage regulation range and faster dynamic response which can be used to low voltage DC microgrid.Considering the robustness of Sliding-mode variable structure control in case of disturbance and parameter variation,a sliding-mode variable structure control algorithm was designed.In this article,the DC micro-grid composed by photovoltaic power generation,energy storage device,fuel cell and load.In islandingmode adopts DC bus voltage signals(DC Bus Signaling,DBS)control strategy as the micro-grid energy management,In grid-connected mode the grid converter based on sliding mode variable structure control strategy of dc micro power grid voltage control,ensure stable of the DC bus voltage,specific work as follows:1)By the analysis of each micro-source output characteristic,choice the interface converter of each micro-source,and design the parameter of converters.2)By comparing the advantages and disadvantages of various control strategies of the DC micro-grid,selects the DBS control strategy to achieve coordinated control.3)Establishes the small signal modeling of micro-source interface converter,and designs of the controller parameters of the micro source interface converter.4)Using MATLAB/Simulink software to establish the DC micro-grid simulation model,the simulation results verify the DBS control strategy is feasible.5)Analyzing the DC micro-grid interconnection converter,and select the two stage interconnection converter as the DC micro-grid interface converter.At the same time,in order to stabilize the DC bus voltage,DC/DC converter uses voltage and current double loop PI control,DC/AC converter uses the voltage and current double loop control based on sliding mode variable structure,to achieve the stability of the DC side voltage DC micro power grid and the two-way control of AC power,establishing a simulation model in the MATLAB/Simulink software,the simulation results show that the control strategy is feasible.