Research On Supercapacitor Equalization Circuit Based On Constant Current

With the innovation and progress of the renewable power generation technology,the energy storage systems have also been rapidly developed.Among them,supercapacitors are widely used in various fields due to their short charging and discharging time and high power density.When the series-connected supercapacitors is charged and discharged,due to the inconsistency of the series-connected supercapacitors,some supercapacitors may be overcharged or over-discharged.In the long run,this will not only affect the performance of the series-connected supercapacitors,but also accelerate its aging speed.Therefore,it is necessary to use voltage equalization technology to avoid the adverse effects of the inconsistent voltage of the cells in the series-connected supercapacitors.Therefore,this thesis aims to study the supercapacitor equalization circuit with lower cost and better equalization performance,and designs three improved equalization circuits.Traditional switching networks usually require a large number of switches,while the control is complex and the circuit cost is high.Therefore,this thesis improves and designs a grouping equalization circuit based on the bidirectional Cuk structure on the basis of the existing switch network.The equalization circuit effectively reduces the number of the driving circuits and reduces the cost of the equalization circuit by combining the grouping switch network with the bidirectional Cuk converter.In this thesis,the energy transfer characteristics and control strategy of the equalization circuit are studied to realize the bidirectional transfer of energy between the two groups of supercapacitors until the voltages of all supercapacitors are balanced.The grouping equalization circuit based on the bidirectional Cuk structure slows down the equalization speed in the later stage of equalization.In order to solve the problem that it is difficult to take into account the equalization speed and accuracy,this thesis proposes a grouping equalization circuit based on the LC~3L structure.The equalization circuit outputs a constant equalizing current in a fixed-frequency open-loop state,which speeds up the equalizing speed and improves the equalizing precision.At the same time,this thesis analyzes the constant current sensitivity of the equalization circuit,and the influence of resonance parameter deviation on its constant current characteristics is studied in this thesis.In addition,by improving the equalization control strategy,the circuit equalization loss is reduced.With the increase in the number of supercapacitors,the switches and isolated power supplies in equalization circuit base on the switching network also increase accordingly.this thesis designs a constant-current output Full wave voltage multiplier by adding a parallel capacitors and designing the parameters of each component.The equalization circuit only needs to control two switches to realize the voltage equalization of the series-connected supercapacitors,thereby reducing the circuit volume and the circuit cost.And this thesis deduces its DC equivalent circuit and expounds its equalization principle.Compared with the traditional full-wave rectification equalization circuit,the equalization circuit outputs a constant equalization current,thereby improving the equalization speed.Finally,the feasibility and effectiveness of the proposed equalization circuits are verified by static and charging equalization experiments.