Constant Current and Constant Voltage Hybrid Bidirectional String-to-Cell Equalizer Based on C2L3 Resonant Topology

Key performance metrics in battery equalization systems include equalization speed, energy flow path length and control complexity. In this paper, we propose a string-to-cell equalizer based on the C2L3 resonant topology to achieve a good comprise among those metrics. The proposed equalizer hybridizes constant current (CC) and constant voltage (CV) balancing in different stages of equalization, ensuring both fast speed and high accuracy. Moreover, we adopt direct String-to-Cell (S2C) and Cell-to-String (C2S) connections to minimize energy flow path length. Besides, open loop control is analyzed and adopted, which can significantly reduce the control complexity. Simulations are conducted to verify feasibility of the proposed equalizer. An experimental prototype of C2L3 converter is designed. Experiment shows that it has a good ZVS ability.