Multi-Cell-to-Multi-Cell Battery Equalization in Series Battery Packs Based on Variable Duty Cycle

Abstract

Batteries are widely used in our lives, but the inevitable inconsistencies in series-connected battery packs will seriously impact their energy utilization, cycle life and even jeopardize their safety in use. This paper proposes a balancing topology structure combining Buck-Boost circuit and switch array to reduce this inconsistency. This structure can realize multi-cell-to-multi-cell (MC2MC) battery balancing by controlling the switch array and having a fast balancing speed, easy expansion and few magnetic components. Then, the operation principle of the proposed balancing topology is analyzed, and the simulation model is verified. In addition, the effects of switching frequency and voltage difference on the equalization effect are further analyzed. The results show that the higher the switching frequency, the lower the time efficiency, but the higher the energy efficiency. The voltage difference significantly impacts the duty cycle, so it is absolutely necessary to introduce a variable duty cycle in the multi-cell-to-multi-cell equalization. Finally, eight series batteries are selected for simulation verification. The simulation results show that, compared with any-cell-to-any-cell (AC2AC) equalization, the time efficiency of multi-cell-to-multi-cell equalization is improved considerably, the energy efficiency is improved slightly, and the variance of the completed equalization is reduced, demonstrating the excellent performance of multi-cell-to-multi-cell equalization.

Multi-Mode Lithium-Ion Battery Balancing Circuit Based on Forward Converter with Resonant Reset

“…Compared with the aforementioned balancing methods, Multi-Cell-to-Multi-Cell (MC2MC) [36][37][38] not only allows multiple cells to participate in a single balancing process for energy transfer, but also enables energy transfer between battery clusters. The concentration of energy transfer during the balancing process enhances balancing speed and reduces energy losses during the transfer.…”

“…Luo. S et al [38] proposed a balancing circuit based on a Buck-Boost converter, which simplifies the structure of the switch matrix through cell grouping. However, the LC resonant converters used in [36][37][38] often require bulky magnetic components and high-voltage switches when applied to balance high-voltage and large-capacity battery packs [39].…”

“…S et al [38] proposed a balancing circuit based on a Buck-Boost converter, which simplifies the structure of the switch matrix through cell grouping. However, the LC resonant converters used in [36][37][38] often require bulky magnetic components and high-voltage switches when applied to balance high-voltage and large-capacity battery packs [39]. Additionally, the use of numerous MOSFETs in the switch matrix in [37] not only requires complex driver circuits, increasing circuit costs, but also adds complexity to circuit control.…”

“…Additionally, the use of numerous MOSFETs in the switch matrix in [37] not only requires complex driver circuits, increasing circuit costs, but also adds complexity to circuit control. Although the structure of the switch matrix is simplified in [38], there is a possibility of circuit malfunction when cells within the same group are involved in balancing, indicating a lower robustness of the circuit.…”