Dual-Layer Energy Equalization for Series Battery Packs by Scheduling the Balancing Current With an Improved Model Prediction Controller

This paper designs a dual-layer hardware topology for series battery packs to realize the synchronous energy transfer among cells in the same module and cells across different modules. A bus-type flying-inductor structure is employed as the bottom-layer functional block, with sufficient dead-time gaps inserted between switches to mitigate MOSFET heating caused by short-circuits. In order to maintain the energy throughput capability, auxiliary components are added for inductor current freewheeling, thereby facilitating the charge transfer between target cells. Then, a typical transformer is adopted as the top-layer functional block to directly balance the selected cells in different modules. Subsequently, considering constraints regarding the withstand voltage and maximum current of the tubes, the model prediction control is improved with multi-objective optimization gain-scheduling mechanism to determine the balancing currents for both layers, wherein the gain matrix is adjusted according to the remaining charge deviations between cells. Experimental verifications conducted on a pack consisting of 9 cells divided into 3 modules indicate that compared with traditional methods, the proposed equalization scheme exhibits superior performance in terms of balanced energy transfer timeliness and efficiency.