Ultra-capacitor

as a new energy storage device

is used widely in the new energy generation place and energy feedback and energy recovery system. However

the development and application of the capacitor is limited by its grading problem. In this paper

Buck-Boost circuit is adopted

and the inductance in the grading circuit is used as medium of energy transfer between 2 capacitors to complete grading of the 2 capacitor bank. For the control circuit part

a kind of hysteresis current control method with hysteresis width constant frequency is adopted

which in the time of maintaining such series features of hysteresis control as fast response speed and good stability

overcomes such shortcoming as unfixed switching frequency and the correctness of theoretical scheme is verified by simulation.