| In DC microgrid system,DC load and storage battery are widely used,and the parallel operation control technology of DC/DC converter is a key problem to be solved.In this thesis,the control strategy of bidirectional DC/DC converter and the suppression strategy of multi-machine parallel circulation are studied.On this basis,the bidirectional DC/DC converter is designed,and the effectiveness of the research strategy is verified by experiments in parallel operation.In this thesis,the topological structure of the three-phase Buck/Boost bidirectional DC/DC converter is analyzed,the AC small signal model of the bidirectional DC/DC converter is established,and the working state and control strategy of the converter in parallel operation mode are studied.In order to improve the circulation suppression performance and power distribution effect of the bidirectional DC/DC converter in parallel operation,and reduce the voltage sag of the bus in the parallel system,reactive power is introduced into the DC sag control.Based on this,an improved virtual frequency sag control strategy is studied and proposed to reduce the voltage sag of the bus.The results of power equalization and proportional distribution of DC/DC converters in parallel operation are improved,and the feasibility and effectiveness of the control strategy are verified by simulation.Based on the above work,a 30 k W non-isolated Buck/Boost bidirectional DC converter is designed and built with TMS320F28335 as the core.The main circuit component selection requirements are analyzed,and the energy storage inductance,energy storage capacitor and power switch tube are selected rationally.The main circuit,main control circuit,power circuit,sampling circuit and so on are designed according to the requirements of experimental prototype.Based on hardware design,complete the system software design,including the main program,interrupt program,flow control program,etc.Based on the above work system test.In the case of parallel operation,pulse test is carried out on the switching tube to ensure that each converter can run stably.Verify the feasibility and effectiveness of the control strategy of circulation suppression and power distribution studied in this paper,and verify the voltage stability of the bus when the control strategy is used in parallel operation.The output current voltage ripple of the converter is analyzed.The experimental results show that the converter control strategy can distribute power stably and efficiently,and stabilize the bus voltage.The experimental prototype runs reliably and stably. |
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