Research Of Bidrectional DC-DC Conversion Technology Based On Super Capacitor

Nowadays，bidirectional DC-DC converter is an important component of theenergy management system in the urban rail transit, solar wind and other independentpower systems, elevator control and electric vehicles and other applications. As anemerging energy storage component, super capacitor has the advantage of high powerdensity and more charging and discharging times. In this dissertation, bidirectionalDC-DC conversion technology based on super capacitor is researched as follows.In high-power application occasions, as the limitation of magnetic material,isolated bidirectional converter technology is not suitable in these areas. For thissituation, this dissertation studies the non-isolated bidirectional conversion technology,especially the outstanding problems during the operation of the typical Buck/Boosttopology, such as oscillation problems in discontinuous operation mode, switchinglosses problems. This dissertation gives the conditions of eliminating oscillations andachieving soft switching Based on the above analysis, this dissertation studies thedesign method of passive parameters, to ensure eliminating parasitic oscillations andachieving soft switching in a wide range of input and output voltages.This dissertation also discusses the stability and dynamic characteristics of theopen loop small signal model in the main power circuit. On this basis, in order toachieve the system stability and fast response, this article presents an effectivecompensation measures combined with the super capacitor subparagraph charging anddischarging policies, a DSP-based digital controller is designed. For this control system,this article verified though simulation, and the simulation results show that the inductorcurrent namely super capacitor charging and discharging current can achievesegmentation control after adopting the compensatory measures.An experimental prototype is designed in this article based on the theoretical studyand the simulation. The prototype adopts the typical Buck/Boost topology and supercapacitor. Experimental results show that the soft-switching strategy proposed in thisdissertation is reasonable, achieving a soft opening of the switch, while the supercapacitor can achieving charging and discharging in constant current, the dynamiccharacteristics of the system is good.