Research On Backstepping Sliding Mode Control Strategy Of DC Micro Grid Energy Storage Device

Energy storage device,as the important part of micro grid,is connected to the bus with bidirectional DC/DC converter.It can provide electric when the power system overloads or fails.Thus build reasonable and accurate models of energy storage device and bidirectional DC/DC converter,make the rule of charging and discharging modes change and design backstepping sliding mode control strategy can avoid energy storage device changing modes frequently and reduce current fluctuation during transfer.It has vital meanings to improve micro gird stability,reduce power cost and guarantee power supply reliability.Construct whole structure of DC micro grid and build battery third-order dynamic model on the basis of researching characteristics and principle of DC micro grid.Choose lead-acid battery as the energy storage device to do the charging and discharging test.Get the simulation parameters according to the result and build simulation model in Matlab/Simulink which includes SOC and DOC calculation models.Do the simulation test of it,compare with test result and verify the accuracy of the model.Select bidirectional half bridge converter as the connection device between battery and DC bus to transfer current and build its structure.Determine the relationship between working modes and current direction.Build simulation model according to the structure and do the simulation tests of Boost and Buck modes.Get the current and voltage of inductance,turning tube and diode as well as the current and voltage output by the converter,then compare with theoretical results.Design backstepping sliding mode controller to control the bidirectional DC/DC converter and reduce the jitter in the process of battery switching operating modes.Establish a state space model of bidirectional DC/DC converter and do the feedback linearization.Get backstepping control function considering uncertain parameters like component aging.Then combine with sliding mode item to finish the design of backstepping sliding mode controller.At last set up the whole model of DC micro grid in Matlab/Simulink.Set simulation parameters and do the simulations according to the situations of different load requirements and different SOC.Get the curves of bus voltages and SOC in different situations.Compare with the curves under traditional PI control and verify the effectiveness and accuracy of backstepping sliding mode control strategy.