The Research On Li-ion Battery Charge Control And Management

With the development of science and technology, lithium battery is widely used in domestic, military and other fields because of its special charge and discharge characteristics. But there are also some limitations in the usage of lithium batteries. For example, overheating and even explosion may be resulted in without the control of battery currents during the charge of a battery. It will cause a great threat to human’s safety. And if overcharge is generated on a lithium battery, its life will be reduced quickly. Therefore, it’s necessary to control and manage the charge for a lithium battery to avoid the overheating and overcharging phenomenon.In a lithium series connected battery pack, there is still more or less difference among the batteries, such as the capacity or inner resistance, due to their production technology even when they are produced in a batch, which can result in the overcharge for some batteries, while others are still not charged completely. This is called the unbalance in charge. Unbalance in charge can not only exert an influence on the usage performance of the battery pack, but also affect its life and safety. This is still a difficult problem all over the world. To avoid the unbalance in charge, the control and management must be exert on the batteries during the charge, which can also save the electrical energy for the battery charger.Active control on battery charging is studied in this thesis, including the current control on the charging for a lithium battery and equalization control on a series connected lithium battery pack. Firstly, a lithium battery charging control and management system is designed and developed, which include the design of all modules of the system and their programs for the current control and protection on the battery charge. Then an active equalization strategy is studied based on flyback transformers. Its mathematical models are built and an heuristic algorithm and a genetic algorithm are presented. They are simulated in the PSCAD software. In the simulation, the voltage of the batteries is monitoring and their curves are observed. The effectiveness of the algorithms is proved by the simulation.