Electric vehicle energy storage device and a control method thereof

Abstract

The invention discloses an electric vehicle energy storage device and a control method thereof; the device comprises N batteries serially connected in series, one end of the series circuit is connected to the power supply, the other end is grounded, and an inverter equalization module is connected in parallel between two adjacent batteries. Each inverter equalization module is composed of a capacitor C1, an inductor L1 / L2, a controllable switching device S1 / S2 and a diode D1 / D2. During operation, the controllable switching devices S1 / S2 are alternately turned on under the control of PWM pulses. When the controllable switching device S1 is turned on, the charging current of the battery B1 decreases and the inductor L1 starts to store energy when the controllable switching device S1 is turned off, the controllable switching device S2 is turned on, and the inductor L1 induces an induced electromotive force of left positive and right negative, and releases energy to the battery B2, so thatthe charging current thereof is higher than that of other batteries. The charge equalization of each cycle can be adjusted by controlling the pulse width of PWM pulses, and the direction of charge transfer can be controlled by changing the polarity of PWM pulses. The scheme can realize the lossless equalization of the battery.

Description

technical field [0001] The invention relates to the technology in the field of batteries, in particular to an electric vehicle energy storage device and a control method thereof. Background technique [0002] The electric vehicle power battery is composed of multiple single rechargeable batteries connected in series and parallel to meet the voltage and capacity requirements of the power source. Due to the influence of manufacturing process, aging and ambient temperature, there are inevitably inconsistencies in the capacity, internal resistance and other properties of single batteries. The cycle life of single cells working in groups is lower than that of single cells, which is mainly caused by the inconsistency of single cells. [0003] The inconsistency and harm of the battery are mainly manifested in: [0004] (1) Capacity inconsistency. First of all, batteries with different capacities have different discharge depths. In the same group of batteries, when the battery w...

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Problems solved by technology

In the same group of batteries, when the battery with a larger capacity is still in shallow discharge, the battery with a smaller capacity may have entered a deep discharge stage or has been discharged and become a load on the circuit. The reverse polarity of the battery occurs, making the entire battery pack abnormal. work, and at the same time have a great impact on the battery life of the opposite pole

Secondly, the best discharge currents of similar batteries with different capacities are different, but the working current of each battery is the same when working in groups, so it is impossible to take care of both

Finally, during the charging process, the voltage of the battery with smaller capacity rises faster, and it is very easy to overcharge when the charging is about to end.

A battery with a small capacity is prone to enter a vicious cycle and be damaged in advance during the charging and discharging process

[0005] (2) Internal resistance inconsistency

During the discharge process, the battery with large internal resistance has a large voltage drop and energy loss, which is easy to generate heat and cause the battery to heat up, and the inconsistency of the ambient temperature will further aggravate the imbalance of battery performance in the group

During the charging process, the charging voltage of the battery with larger internal resistance is higher, and it is easy to reach the upper voltage limit in advance

[0006] (3) Voltage inconsistency

The inconsistent capacity and internal resistance lead to increasingly serious voltage inconsistency during the use of the battery pack

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