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Balance strategy of active battery pack balancer

(Summary description)In order to increase the equalization speed and effectively and quickly increase the charge and discharge capacity of the battery pack, different active battery pack balancer strategies are adopted for different working states of the battery pack

Balance strategy of active battery pack balancer

(Summary description)In order to increase the equalization speed and effectively and quickly increase the charge and discharge capacity of the battery pack, different active battery pack balancer strategies are adopted for different working states of the battery pack

Information

In order to increase the equalization speed and effectively and quickly increase the charge and discharge capacity of the battery pack, different active battery pack balancer strategies are adopted for different working states of the battery pack, the equalization current is continuous and controllable, and the equalization circuit is easy to control and implement. This article analyzes in detail the balancing strategy and working principle of the active battery pack balancer, and builds an experimental platform to perform charging and discharging balancing experiments on series-connected lithium iron phosphate batteries. The results of the balancing experiments prove the effectiveness of the energy balancer.

active battery pack balancer

Lithium-ion batteries have the advantages of small size, light weight, high energy density, relatively high nominal voltage, long cycle life, and no memory effect, and are widely used in electric vehicle power supplies. The nominal voltage of the lithium-ion battery is low, and the lithium iron phosphate battery is only 3.2V. To meet different voltage levels, multiple single lithium-ion batteries are required in series.

However, there are performance differences between single lithium ion batteries. During the use of the battery pack, the energy inconsistency between each single lithium ion battery will occur, which causes the charging and discharging capacity of the battery system to gradually decrease. In order to solve the problem of energy inconsistency between single cells connected in series in a battery pack, effective measures must be taken to balance the energy of the battery pack, such as an active battery pack balancer.

According to different energy storage components, the current active battery pack balancer can be divided into resistance balance, capacitance balance, inductance balance, LC balance and transformer balance, etc. Among them, the resistance balance is energy consumption balance, and the other types are non-energy consumption balance. Capacitor equalization uses capacitors as the carrier of energy transfer, and achieves energy balance through the voltage difference between single cells. Because the voltage difference between batteries is small, it is difficult to balance energy transfer; inductance balance uses inductance as the carrier of energy transfer, and it is easy to balance current However, the equalizer performance is determined by the equalizer circuit structure and equalization strategy; LC equalization realizes capacitance equalization through the LC oscillation circuit, which makes up for the shortcomings of small capacitance equalization voltage difference, but the switching frequency is high, the equalization circuit control is complicated, and the equalization efficiency is low; Transformer balance mostly uses flyback transformer as the carrier of energy transfer. The size of the equalizer is large, and the equalization efficiency and equalization speed are both limited.

Due to the limited functions of the existing equalizers, the balanced topology circuit or balancing strategy is single, and different balanced topology circuits or balancing strategies are rarely adopted according to the working state of the battery. Therefore, the current active battery pack balancer generally has a slow balancing speed and a balanced energy. Poor controllability and unsatisfactory balance effect.

The high-speed energy equalizer for battery packs based on hybrid chopper circuit realizes energy balance under three states of battery pack charging, discharging and standing by different chopper circuits. The equalization speed is fast, the equalized energy is continuous, and the controllability is strong. At the same time, it can effectively and quickly increase the charging and discharging capacity of the battery pack. The two-way flow of energy is realized through the double-layer bridge arm, the active battery pack balancer has low energy loss, the control of the equalizer is simpler, and the circuit is easier to implement.

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