Balancing Method Based on Flyback Converter for Series-Connected Cells

For the various imbalances of series-connected cells, the existing balancing methods has the disadvantages of limited energy flow direction and unnecessary charge transfer. Based on flyback converter, this paper proposes a multi-winding input and multi-winding output bi-directional equalization topology. It can realize any cell (s) to any cell (s) balancing, which has the advantage of flexible balancing energy flow path. This paper adopts the control strategy of time-sharing participation in equalization according to the order of the initial state of charge (SOC) of cells, it can solve the problem of unnecessary energy transfer and simplify the control logic. In addition, it gets rid of the influence of energy loss of the circuit components on the setting of the fixed equalization end judgment value, whether equalization ends or not depends on the difference between the discharge cells and the charge cells in this paper, which has the advantage of random adaptive adjustment. In this paper, the operational principle of the proposed circuit are analyzed and the equalization strategy is described in detail. A comparison in balancing performance between the conventional equalization topology based on flyback converter and proposed topology is shown in static state. To verify the validity of the proposed method, the simulation experiment of four cells series-connected is carried out, and the simulation results show that the balancing method proposed in this paper has faster equalization speed and higher equalization energy transfer efficiency.