Research On Series And Parallel Connections Change Over Technology Of Supercapacitor

Supercapacitor has a very broad application in hybrid car starting and accelerating system and high power pulse power system because of large capacity, high power density, long circle-life in charge and discharge and so on, but the disadvantage of low energy density seriously restricts development.of the supercapacitor. The supercapacitor will stop discharge when its voltage reaches the half of the nominal voltage in the energy storage applications and this will leave the supercapacitor energy in the idle state. In this paper, to solve this problems and trying to reduce the depth of discharge of supercapacitor, the research on series and parallel change over technology of supercapacitor is carried out.In this paper, supercapacitor equivalent circuit model was established firstly, and the supercapacitor series and parallel structure was designed. And then the super capacitor charging and discharging methods were analyzed, and based this, the methods of series and parallel change over was analyzed and the system control strategy was made on the basis of the design method and the amount of voltage and current as the reference of series and parallel change over. And the half-bridge bi-directional converter topology was analyzed and choosed, and then the relationship between input and output transformer ratio and the efficiency of the converter were analyzed, and finally determine the system input and output transformer ratio limit within 3.Due to the introduction of the series and parallel change over technology of supercapacitor, the input voltage of bidirectional half bridge Buck-Boost circuit step mutations occur in the Boost mode. However separate feedback control is delay control system, and can not make the load side voltage fluctuation when then series and parallel change to meet the system requirements. This paper adopt the compound control, the feedforward-feedback to two-way half bridge Buck-Boost converter modeling, and make the simulation system.we set up the system experimental platform.we design the main circuit of system, control circuit and software of the system Through charging and discharging experiments, series-parallel conversion technology make the discharge time increased from 546s to 708s, the depth of discharge change from 50V to 12.5V,so we achieved the desired results.