Dynamic Duty Modulation to Enhance Voltage Equalization Performance of the Advanced Cell Balancer

Cell balancing is a critical requirement for ensuring the safety and longevity of supercapacitor (SC)-based energy storage systems (ESSs). While conventional series-parallel active balancing methods predominantly utilize a fixed 50% duty ratio, this static control mechanism fundamentally limits the energy transfer rate, particularly under severe initial voltage imbalances and non-ideal cell variations. To accelerate the equalization process without incurring the cost, volume, and complexity penalties of hardware modifications, this paper proposes a dynamic duty modulation (DDM) technique. The proposed DDM algorithm adaptively adjusts the switching duty ratios in real-time based on the instantaneous voltage deviations of individual cells. A discrete-time mathematical model is derived to evaluate the convergence behavior, analytically proving that the dynamic approach requires significantly fewer switching cycles than the conventional fixed-duty method. The mathematical superiority and practical feasibility of the proposed technique are strictly validated through comprehensive PSIM simulations. Quantitative simulation results confirm that the proposed DDM reduced the balancing time by over 48% and proportionally decreased the total number of switching cycles compared to the conventional method, providing an enhanced dynamic performance suitable for advanced battery management systems (BMSs).