| With the rapid economic development,continuous advancement of science and technology,and the rise of new energy industrial technologies,researching on energy storage technologies has become a research hotspot at home and abroad in recent years.Among many energy storage technologies,combining a battery and a super capacitor to form a composite energy storage system can give full play to their respective advantages and have broad application prospects.At this stage,the composite energy storage system generally uses two DC/DC converters to connect,but the use of two DC/DC converters will result in a substantial increase in cost,volume and quality,and the two converters generally need to add Communication devices have problems such as poor reliability.Two different energy storage devices are connected through a three-port DC/DC converter,thereby reducing the number of DC/DC converters used,optimizing the system structure,and achieving low volume quality,high integration,and high efficiency of the energy storage system.Therefore,it is of great significance to study the three-port DC/DC converter for composite energy storage.The vehicle-mounted composite energy storage system applied to rail transit has characteristics of large power and high voltage level,and the use of a three-level converter can effectively reduce the voltage stress of the switch tube.This paper proposes a novel flying capacitor three-level three-port DC/DC converter by improving the flying capacitor end of the traditional flying capacitor three-level DC/DC topology.The converter has not only the characteristics of a flying capacitor three-level converter but also a three-port DC/DC converter.This paper presented the topology structure of the new converter,focused on exploring and analyzing the working principle of each mode of the converter under different working conditions,and derived the relationship between the input voltage and output voltage in each state.Aiming at the flying capacitor voltage equalization control of the new converter,a control strategy for dynamically determining the duty cycle is proposed to realize the dynamic balance of the flying capacitor voltage.This article focused on the analysis of the voltage coupling between the three ports of the converter,and drawed a map of the voltage coupling between the ports of the converter,and performed storage for the applications of the rail transit vehicle battery and super capacitor composite energy storage system.The voltage range of the energy system and the parameter design of the new three-port DC/DC converter.Finally,the working principle,control strategy and working range of the converter were verified by MATLAB/Simulink simulation.The experiment platform was built by using dSPACE and Typhoon to verify the feasibility of the working principle of the converter. |
