阅读说明：本技术 动力电池管理系统跨铜排电压采样的补偿方法 (Compensation method for copper bar crossing voltage sampling of power battery management system ) 是由 张静 刘振 于 2019-11-13 设计创作，主要内容包括：本发明提供了一种动力电池管理系统跨铜排电压采样的补偿方法,包括以下步骤：电池管理系统和电流传感器上电；读取待采集电芯对应的铜排的标定参数；获取铜排电连接的电流传感器的电流值；计算铜排温度；根据铜排温度和电流传感器的电流值计算需要补偿的铜排电压；将采集的电芯电压加上补偿的铜排电压,得出电芯实际电压。本发明减少了动力电池管理系统单体电压采样通道的数量,降低了系统的成本,并且提高了动力电池系统的能量密度。(The invention provides a compensation method for copper bar crossing voltage sampling of a power battery management system, which comprises the following steps of: powering on a battery management system and a current sensor; reading calibration parameters of a copper bar corresponding to the electric core to be collected; acquiring a current value of a current sensor electrically connected with the copper bar; calculating the temperature of the copper bar; calculating the voltage of the copper bar to be compensated according to the temperature of the copper bar and the current value of the current sensor; and adding the acquired cell voltage to the compensated copper bar voltage to obtain the actual cell voltage. The invention reduces the number of single voltage sampling channels of the power battery management system, reduces the cost of the system and improves the energy density of the power battery system.)

1. A compensation method for copper bar crossing voltage sampling of a power battery management system is characterized by comprising the following steps:

powering on a battery management system and a current sensor; reading calibration parameters of a copper bar corresponding to the electric core to be collected; acquiring a measured value of a current sensor electrically connected with a copper bar corresponding to a battery cell to be acquired; calculating the temperature of the copper bar; calculating the voltage of the copper bar to be compensated according to the temperature of the copper bar, the actual resistance value of the copper bar and the measured value of the corresponding current sensor; and adding the acquired voltage of the battery cell to be acquired with the compensated copper bar voltage to obtain the actual voltage of the battery cell to be acquired.

2. The compensation method for the voltage sampling across the copper bar of the power battery management system according to claim 1, wherein the compensation method comprises the following steps: the calibration parameters of the copper bar comprise whether the electric core needs to be compensated, the position of the copper bar and the resistance value of the copper bar.

3. The method for compensating for the power battery management system voltage sampling across the copper bar according to claim 2, characterized by comprising the following steps:

judging whether the copper bar compensation algorithm is enabled or not according to the copper bar calibration parameters after the battery management system is powered on; determining whether a voltage acquisition channel of the battery cell to be acquired has copper bars or not after enabling a copper bar compensation algorithm; if so, continuously judging whether the current value of the current of the bus detected by the current sensor is received; after the judgment result is yes, calculating the temperature of the copper bar; if the judgment of any step is negative, the calculation of the compensated copper bar voltage is not carried out.

4. The compensation method for the voltage sampling across the copper bar of the power battery management system according to claim 3, wherein the calculation formula of the copper bar compensation voltage is as follows:

Ut＝IR₁+I[R₂+R₂(T-20)*k]

ut: compensation voltage generated by the copper bar; i: the current value of a current sensor electrically connected with the copper bar; r₁: the contact impedance of the copper bar; r₂: the resistance value of the copper bar is 20 ℃; t: the temperature of the copper bar; k: copper temperature rise coefficient 0.00393/DEG C; the contact internal resistance and the 20-degree resistance value of the copper bar are obtained through measurement, and the temperature rise coefficient of the copper resistor is a parameter of the product; before the battery management system is powered on, the parameter coefficients of the related copper bars are already input into the battery management system.

5. The compensation method for the voltage sampling across the copper bar of the power battery management system according to claim 4, wherein calculating the temperature of the copper bar comprises the following steps:

calculating the initial resistance value of the copper bar according to the temperature rise coefficient of the copper bar; calculating the heat productivity of the copper bar according to the initial resistance value of the copper bar, and calculating the temperature rise of the copper bar according to the heat productivity; calculating the heat dissipation capacity of the copper bar according to the temperature rise; calculating the accumulated heat of the copper bar by subtracting the heat dissipation amount from the heat productivity; calculating the actual temperature rise of the copper bar according to the accumulated temperature rise; and adding the actual temperature rise of the copper bar and the initial temperature to obtain the temperature of the copper bar.

6. The compensation method for voltage sampling across the copper bar of the power battery management system according to claim 5, wherein the initial resistance R of the copper bar is calculated by the following formula₀：

R₀＝R₂+R₂(T₀-20)*k，

Wherein, T₀The initial temperature of the copper bar is obtained through a temperature sensor of the battery cell.

7. The compensation method for the voltage sampling across the copper bar of the power battery management system according to claim 6, wherein the compensation method comprises the following steps:

according to the formula Q of resistance heating₁Calculating the heat productivity Q of the copper bar in an integral mode according to the I ^ 2. R.t₁The unit is J; wherein I is the current on the copper bar detected by the current sensor, and the unit is A; r₀The initial resistance value of the copper bar is in omega; t is time in units of s.

8. The compensation method for the voltage sampling across the copper bar of the power battery management system according to claim 7, wherein the compensation method comprises the following steps:

respectively calculating the temperature rise and the actual temperature rise of the copper bar according to a heat calculation formula Q (CM △ T), wherein C is the specific heat capacity of the copper bar, M is the mass of the copper bar and is in kg, and the current heat quantity Q1 brought into the copper bar is calculated to obtain the temperature rise △ T of the copper bar according to the formula J₁The unit is the temperature, the accumulated heat Q3 is brought into the formula, and the actual temperature rise △ T of the copper bar is calculated₂In units of ℃.

9. The compensation method for voltage sampling across the copper bar of the power battery management system according to claim 8, wherein the heat dissipation Q2 of the copper bar is calculated by means of integration according to a heat dissipation calculation formula Q2 ═ K · F · △ T · T, and the unit is J;

wherein K is the heat transfer coefficient of the copper bar and has the unit of W/square meter DEG C, F is the heat dissipation area (namely the surface area of the copper bar) of the copper bar and has the unit of square meter, △ T is the temperature rise of △ T of the copper bar₁In units of; t is time in units of s.

Technical Field

The invention relates to the technical field of new energy automobile power battery management systems, in particular to a compensation method for copper bar crossing voltage sampling of a power battery management system.

Background

With the popularization and application of new energy automobiles, the financial subsidy technology threshold is further improved, the technical indexes and the gears in the aspects of endurance mileage, battery energy density, energy consumption level subsidy and the like are refined, the market competition gradually becomes "white hot", and the requirements on the cost and the parameters of each part are further improved.

At present, a plurality of power battery modules are generally connected in series through a plurality of copper bars to form a power battery system. Taking an example that a 96-string power battery system is composed of 4 strings of power battery modules, the system needs 24 power battery modules and at least 23 copper bars to be connected in series.

The battery management system scheme of using always causes the influence for avoiding the partial pressure of copper bar when the overcurrent to monomer voltage's collection, can sample alone the voltage of copper bar, rejects the voltage of copper bar again, and the battery system of 96 strings about needs 119 voltage sampling channels to go to gather like this, very big waste that has caused sampling channel. Meanwhile, due to the increase of the sampling channel, the system cost is increased, the volume and the weight of the battery management system are increased, and the energy density and the cost of the whole power battery system are influenced.

There is also a scheme of voltage sampling across the copper bar, and 96 power battery systems in series adopt 96 voltage sampling channels, and do not process the partial pressure of the copper bar. However, when a large current flows, the error between the sampled voltage and the actual battery voltage is large, so that the problems of battery misprotection, misequalization, influence on SOC correction and the like are caused.

Disclosure of Invention

The invention aims to provide a compensation method for copper bar crossing voltage sampling of a power battery management system, aiming at the defects of the prior art, so that the number of single voltage sampling channels of the power battery management system is reduced, the cost of the system is reduced, and the energy density of the power battery system is improved.

The invention provides a compensation method for copper bar crossing voltage sampling of a power battery management system, which is characterized by comprising the following steps of:

powering on a battery management system and a current sensor; reading calibration parameters of a copper bar corresponding to a to-be-collected battery core, wherein the calibration parameters are set in a battery management system; acquiring a current value of a current sensor electrically connected with a copper bar, namely a bus current value of a battery cell to be acquired; calculating the temperature of the copper bar; calculating the voltage of the copper bar to be compensated according to the temperature of the copper bar, the actual resistance value of the copper bar and the measured value of the corresponding current sensor; and adding the acquired cell voltage to the compensated copper bar voltage to obtain the actual cell voltage.

In the above technical scheme, the calibration parameters of the copper bar include whether the battery cell needs to be compensated, the position of the copper bar, and the resistance value of the copper bar.

The technical scheme comprises the following steps:

judging whether the copper bar compensation algorithm is enabled or not according to the copper bar calibration parameters after the battery management system is powered on; determining whether a voltage acquisition channel of the battery cell to be acquired has copper bars or not after enabling a copper bar compensation algorithm; if so, continuously judging whether the current value of the current of the bus detected by the current sensor is received; after the judgment result is yes, calculating the temperature of the copper bar; if the judgment of any step is negative, the calculation of the compensated copper bar voltage is not carried out.

In the above technical solution, the calculation formula of the compensation voltage of the copper bar is as follows:

Ut＝I R₁+I[R₂+R₂(T-20)*k]

ut: compensation voltage generated by the copper bar; i: bus current; r₁: the contact impedance of the copper bar; r₂: the resistance value of the copper bar is 20 ℃; t: the temperature of the copper bar; k: the copper temperature rise coefficient is 0.00393/DEG C. The contact impedance and 20-degree resistance of the copper bar are obtained by measurement, and the temperature rise coefficient of the resistance is obtained by the self parameter of the product through reference data.

In the above technical scheme, calculating the temperature of the copper bar comprises the following steps:

calculating the initial resistance value of the copper bar according to the temperature rise coefficient of the copper bar; calculating the heat productivity of the copper bar according to the initial resistance value of the copper bar, and calculating the temperature rise of the copper bar according to the heat productivity; calculating the heat dissipation capacity of the copper bar according to the temperature rise; calculating the accumulated heat of the copper bar by subtracting the heat dissipation amount from the heat productivity; calculating the actual temperature rise of the copper bar according to the accumulated temperature rise; and adding the actual temperature rise of the copper bar and the initial temperature to obtain the temperature of the copper bar.

In the above technical scheme, the following formula is adopted to calculate the initial resistance value R of the copper bar₀：

R₀＝R₂+R₂(T₀-20)*k，

Wherein, T₀The initial temperature can be obtained through a temperature sensor of the battery cell.

In the above technical scheme, the formula Q is generated according to the resistance₁Calculating copper by means of integrationHeat generation amount Q of row₁The unit is J; wherein I is the current on the copper bar detected by the current sensor, and the unit is A; r₀The initial resistance value of the copper bar is in omega; t is time in units of s.

In the technical scheme, the temperature rise and the actual temperature rise of the copper bar are respectively calculated according to a heat calculation formula Q ═ CM △ T, wherein C is the specific heat capacity of the copper bar, M is the mass of the copper bar and is in kg, the current heat productivity Q1 of the copper bar is brought into the formula, and is in J, and the temperature rise △ T of the copper bar can be calculated₁The unit is the temperature, the accumulated heat Q3 is brought into the formula, and the actual temperature rise △ T of the copper bar is calculated₂In units of ℃.

In the technical scheme, the heat dissipation capacity Q2 of the copper bar is calculated in an integral mode according to a heat dissipation capacity calculation formula Q which is K.F. △ T.t, and the unit is J;

wherein K is the heat transfer coefficient of the copper bar and has the unit of W/square meter DEG C, F is the heat dissipation area (namely the surface area of the copper bar) of the copper bar and has the unit of square meter, △ T is the temperature rise of △ T of the copper bar₁In units of; t is time in units of s.

The invention reduces the number of single voltage sampling channels of the power battery management system, reduces the cost of the system and improves the energy density of the power battery system. According to the invention, the temperature of the copper bar is estimated in a heat accumulation manner, so that the problem that a temperature sensor is difficult to arrange on the copper bar is solved, and the system complexity is reduced. According to the invention, the sampling precision of the monomer voltage of the power battery cell is improved by compensating the partial pressure of the copper bar.

Drawings

FIG. 1 is a partial schematic view of a system embodying the present invention;

FIG. 2 is a flow chart of the present invention.

Detailed Description

The invention will be further described in detail with reference to the following drawings and specific examples, which are not intended to limit the invention, but are for clear understanding.

Fig. 1 is a partial schematic view of a system to which the present invention is applied, and as shown in fig. 1, 4 strings of 1 battery module, 3 battery modules are connected in series by using two copper bars, B-to B12+ are monomer voltage samples, and each two adjacent groups of sampling lines collect the monomer voltage of 1 cell. The BAT5 collects voltage through the B4+ and the B5+ and samples voltage through the B8+ and the B9+ of the BAT9, voltage drop can be generated when the copper bar passes through current, and voltage drop of the copper bar needs to be compensated on the basis of the sampled voltage.

As shown in fig. 2, the present invention provides a compensation method for copper bar crossing voltage sampling of a power battery management system, which comprises the following steps:

firstly, a battery management system and a current sensor are powered on;

secondly, reading calibration parameters of the copper bar corresponding to the electric core to be collected, wherein the calibration parameters comprise the resistance value of the copper bar, whether compensation is needed or not and the position of the copper bar;

thirdly, acquiring the current value of a current sensor electrically connected with a copper bar corresponding to the battery cell to be acquired;

fourthly, estimating the temperature of the copper bar, and calculating the temperature compensation of the copper bar;

fifthly, calculating the voltage to be compensated of the electric core to be acquired under the current according to a formula;

and sixthly, adding the acquired voltage of the cell to be acquired and the compensated copper bar voltage to obtain the actual voltage of the cell to upload.

The calculation formula of the actual voltage of the battery cell is as follows:

U＝U₁+I R₁+I[R₂+R₂(T-20)*k]

wherein, U: the voltage of the battery cell after compensation; i: bus current; u shape₁: sampling voltage by using a battery core; r₁: the contact impedance of the copper bar; r₂: the resistance value of the copper bar is 20 ℃; t: the temperature of the copper bar; k: copper resistance temperature rise coefficient 0.00393/° C

In this embodiment, when the normal temperature of the copper bar, that is, 20 degrees, is measured by the high-precision internal resistance measuring instrument, the internal resistance and the internal contact resistance between the copper bar and the busbar are measured, and the measured result is calibrated in the battery management system.

In the present embodiment, the current of the bus bar is collected by the current sensor.

In this embodiment, the temperature of the copper bar can be calculated by calculating the accumulated heat, as follows.

(1) Calculating the initial resistance value R of the copper bar through the temperature rise coefficient of the copper₀＝R₂+R₂(T₀-20)*k，T₀The initial temperature can be obtained through a temperature sensor of the battery cell. Setting 20 ℃ resistance R of copper bar₂0.05 m.OMEGA., initial temperature T₀At 0 ℃ and R is calculated by the formula₀＝0.04607mΩ。

(2) Calculating the heat productivity Q of the copper bar by an integral mode according to a resistance heat productivity formula Q ═ I ^ 2. R.t₁The unit is J. Wherein I is the current on the copper bar detected by the current sensor, and the unit is A; r₀The initial resistance value of the copper bar is in omega; t is time in units of s; when the current is set to be 100A, calculating the heat productivity Q of the copper bar for 1 minute through a formula₁＝27.642J。

(3) According to a heat quantity calculation formula Q-CM △ T, the temperature rise △ T of the copper bar is calculated through Q1₁Wherein Q1 is the current heat productivity of the copper bar in J, C is the specific heat capacity of the copper bar in J/(kg. DEG C), known as 0.39 x 10^3, M is the mass of the copper bar in kg, M is 0.2kg, and the 1-minute temperature rise △ T is calculated by the formula₁≈0.354℃。

(4) Calculating the heat dissipation capacity Q2 of the copper bar in an integral mode according to a heat dissipation capacity calculation formula Q & ltK & gt △ T & ltt & gt, wherein the unit is J, wherein K is the heat transfer coefficient of the copper bar and the unit is W/square meter & ltDEG C, F is the heat dissipation area (namely the surface area of the copper bar) of the copper bar and the unit is a square meter, and △ T is the △ T calculated in the second step₁In units of; t is time in units of s. The heat transfer coefficient K of the copper bar is 10W/square meter per square meter, the heat dissipation area F is 0.01 square meter, and the heat dissipation capacity Q2 of 1 minute is calculated by a formula, namely 2.124J.

(5) The cumulative heat Q3 of the copper bar was calculated in J. According to the heat quantity Q1 and the heat dissipation quantity Q2 of the copper bar calculated in the first step and the third step, the accumulated heat quantity Q3-Q1-Q2-27.642-2.124-25.518J of the copper bar is calculated.

(6) Again based on the heat quantity calculation formula Q ═CM △ T, calculating the actual temperature rise △ T of the copper bar through the accumulated heat Q3₂Actual temperature rise △ T at ℃₂＝0.327℃

(7) The actual temperature T of the copper bar is △ T₂+T₀，△T₂For the sixth calculation, T₀Is the initial temperature.

Details not described in this specification are within the skill of the art that are well known to those skilled in the art.