Energy and environmental protection issues are increasingly receiving attention from people from all walks of life at home and abroad. In recent decades, the harmfulness and limitations of traditional energy have had a significant impact on the natural environment and fossil fuels. Countries have had to accelerate the promotion of new energy, and correspondingly, the development and utilization of new energy has become a priority for various countries.
Energy storage technology, as the core support for the development of new energy, its innovation and breakthroughs will become important leading technologies driving revolutionary and disruptive adjustments to the global energy landscape. As a carrier of energy storage technology, lithium-ion batteries have the advantages of high working voltage, high specific energy, long cycle life, and high environmental friendliness, making them widely used in rechargeable energy storage batteries. However, in a long chain energy storage power supply system, the voltage and capacity of a single battery are far from sufficient. In practical applications, a series parallel connection is often used to combine multiple batteries to form a suitable voltage level long chain power supply group. Due to inevitable manufacturing differences and the influence of different internal and external factors such as self discharge rate, aging degree, working state, and working environment during the charging and discharging process of batteries, the differences in these changes will become increasingly significant with the increase of usage times. The use of battery packs in series is affected by the inconsistency between batteries, which easily leads to overcharging and discharging, greatly reducing battery performance. How to solve the “short board effect” of battery capacity has become a bottleneck that restricts the safe and reliable operation of battery packs.
The introduction of balancing technology can greatly improve the performance of battery packs and enhance the security of their systems. However, the existing balancing technology still faces problems such as slow balancing speed, low balancing efficiency, and single balancing method when applied to long chain battery packs. To solve these problems, this paper proposes a distributed balancing charging system structure, This structure can be seen as a two-layer distributed balanced charging system consisting of multiple parallel input and series output balanced charging modules. By inputting a DC bus, the charging and discharging of the battery pack can be balanced across groups, and the local self balancing function of the battery pack can also be achieved. The speed of cross group balancing is much faster than that of local self balancing, which can quickly complete the balancing between battery packs at any position in the long chain battery pack. At the same time, with appropriate balancing control strategies, dynamic charging, discharging, and balancing effects of long chain battery packs can be more efficiently achieved, and the charging module can be perfectly matched with the battery voltage level, which has the advantages of high modularity, high scalability, and strong parallel balancing ability. Considering that each lower level unit circuit needs to be equipped with a bidirectional charging module, its cost will increase with the increase of the number of battery pack cells. Therefore, it is particularly important to determine the topology of the lower level units and develop a coordinated charging balance working mode. Therefore, studying the distributed balanced charging system and control strategy of series energy storage power sources is of great practical significance.