Modeling and simulation of bidirectional buck/boost converter for parallel three-level photovoltaic energy storage

Abstract DC (Direct Current) converters play a key role in energy storage systems to realize the bidirectional flow of energy. The three-level bi-directional Buck/Boost DC converter is widely used because its switching tube voltage stress is half that of a normal Buck/Boost converter, and it has frequency doubling characteristics. In this chapter, the basic principle of the three-level bidirectional Buck/Boost DC converter is analyzed, and the modal analysis and mathematical modeling are performed for Buck mode and Boost mode, respectively. In the parallel three-level topology, the two voltage dividing capacitors on the input side are often unbalanced. This paper adopts the method of PI control to fine-tune the duty cycle of the main control switching tube, thus realizing the voltage balance, and there is also the phenomenon of inductor current unbalance in the parallel structure. Moreover, this paper samples the method of droop control to achieve the balance of the current. Finally, Simulink is used to simulate the system, and the simulation results prove the effectiveness and accuracy of the model.