Dynamic correction method for SOC (State of Charge) of power battery

Abstract

The invention discloses a dynamic correction method for the SOC of a power battery, and the main design concept of the method is as follows: calculating the difference value between the average voltage value of a single battery and the minimum voltage value of the single battery under the condition that the current is set in the running process of a vehicle, calculating the tolerance corresponding to the difference value according to the SOC range, and correcting the SOC of the power battery according to the tolerance. Therefore, after the tolerance or the voltage difference value respectively meets the corresponding preset standard, the SOC is dynamically corrected, and the SOC value needing to be corrected is continuously adjusted according to the preset SOC descent gradient in the discharging process, so that the SOC is corrected to be closest to the actual SOC. According to the invention, the situation that the vehicle lies down in advance due to inaccurate SOC when the power battery pack has undervoltage problems such as self-discharge is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a method for dynamically correcting the SOC of a power battery. Background Art

[0002] Power batteries are the energy source of new energy electric vehicles, and safe and effective battery management systems are key technologies for the development of the electric vehicle industry. In order to enable vehicles to meet people's requirements for endurance and safe driving under complex actual operating conditions, accurately estimating and correcting the state of charge (SOC) of power batteries has important engineering application significance.

[0003] Currently, open circuit voltage correction (OCV) is the most accurate SOC correction method. However, due to the characteristics of SOC-OCV, it needs to be left stationary for more than 30 minutes before it can be accurate. However, it is difficult to meet the stationary time requirement during vehicle driving, so the vehicle often breaks down prematurely. Summary of the invention

[0004] In view of the above, the present invention aims to provide a method for dynamically correcting the SOC of a power battery to solve the above-mentioned technical problems.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for dynamically correcting the SOC of a power battery, which includes:

[0007] During the driving process of the vehicle, if the predetermined battery current condition is met, the voltage difference between the current battery cell voltage average value and the battery cell minimum voltage value is calculated;

[0008] Acquire a corresponding SOC tolerance based on the pressure difference value;

[0009] After the SOC tolerance or the pressure difference value meets the preset standard, the SOC is dynamically corrected, and during the discharge process, the SOC value to be corrected is continuously adjusted according to a preset SOC decrease gradient.

[0010] In at least one possible implementation, the dynamic correction method further includes:

[0011] According to a pre-calibrated open circuit voltage correction table, an open circuit voltage difference corresponding to a predetermined tolerance within a preset SOC interval is calculated as a pressure difference critical value; or, the open circuit voltage difference is combined with a preset coefficient to serve as the pressure difference critical value.

[0012] In at least one possible implementation manner, the pressure difference value meeting a preset standard includes: the pressure difference value being greater than the pressure difference critical value.

[0013] In at least one possible implementation manner, the SOC tolerance meeting a preset standard includes: the SOC tolerance is greater than a preset SOC threshold.

[0014] In at least one possible implementation, the preset SOC decrease gradient includes: [(SOC 原 -△SOC) / △SOC]*0.1%, where SOC 原 To represent the original value of SOC before correction, △SOC is the SOC value to be corrected.

[0015] In at least one possible implementation manner, satisfying a predetermined battery current condition includes: an absolute value of the battery current is less than or equal to a preset current threshold.

[0016] Compared with the prior art, the main design concept of the present invention is to calculate the difference between the mean voltage of the battery cell and the minimum voltage value of the battery cell under the condition of the current setting during the vehicle driving process, and calculate the tolerance corresponding to the difference according to the SOC range, so that after the tolerance or the voltage difference value meets the corresponding preset standard, the SOC is dynamically corrected, and the SOC value to be corrected is continuously adjusted according to the preset SOC drop gradient during the discharge process, so as to correct the SOC to the SOC closest to the actual SOC. The present invention effectively avoids the situation where the vehicle breaks down early due to inaccurate SOC when the power battery pack has undervoltage problems such as self-discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described below with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of a power battery SOC dynamic correction method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0020] The present invention proposes an embodiment of a method for dynamically correcting the SOC of a power battery. Specifically, Figure 1 shown, including:

[0021] Step S1: during the driving process of the vehicle, if the predetermined battery current condition is met, the voltage difference between the current battery cell voltage average value and the battery cell minimum voltage value is obtained;

[0022] Step S2, obtaining a corresponding SOC tolerance based on the pressure difference value;

[0023] Step S3: After the SOC tolerance or the pressure difference value meets the preset standard, the SOC is dynamically corrected, and the SOC value to be corrected is continuously adjusted according to the preset SOC decreasing gradient during the discharge process.

[0024] Specifically, when the vehicle is discharging, when the absolute value of the battery current is ≤5A (this threshold can be adjusted as needed), calculate V cell平均 With V cellmin The difference △V is then calculated according to the preset voltage range to calculate the corresponding SOC tolerance. This is because the SOC is usually calculated by ampere-hour integration during vehicle discharge. If the battery base capacity remains unchanged, it is impossible to actively identify the capacity difference caused by undervoltage.

[0025] Next, if the tolerance calculated by △V is greater than 5% SOC, the SOC is decreased according to the preset SOC decrease gradient, for example, every decrease of [(SOC 原 -△SOC) / △SOC]*0.1%, △SOC is eliminated by 0.1%, where △SOC is the SOC value to be corrected.

[0026] Take a ternary battery as an example (it should be understood that the lithium iron phosphate battery can achieve dynamic SOC correction at the end, i.e., in the SOC < 20% interval. The concept of the present invention can be used for both ternary batteries and lithium iron phosphate batteries, but when applied to lithium iron phosphate batteries, the above-mentioned applicable conditions need to be taken into account).

[0027] The open circuit voltage difference with a tolerance of 5% in the preset SOC range is calculated in advance according to the pre-calibrated open circuit voltage correction table (such as Table 1 attached below): △OCV; for example, in the SOC∈[95,100] range, when Tmin=25°C (for other SOC ranges, linear interpolation is taken at each temperature), △OCV=61mV; further, considering consistency, △OCV can be multiplied by a coefficient of 1.2 as the voltage difference critical value with a tolerance greater than 5%.

[0028] Table 1

[0029] 2. If the absolute value of the current meets the given conditions during driving, and when V cell平均 With V cellmin When the difference △V>1.2*△OCV (i.e., the tolerance calculated based on △V>5%), the SOC is dynamically corrected;

[0030] 3. During the discharge process, every decrease in SOC [(SOC 原-△SOC) / △SOC]*0.1%, △SOC is eliminated by 0.1% until 5% SOC is corrected.

[0031] In summary, the main design concept of the present invention is to calculate the difference between the mean voltage of the battery cell and the minimum voltage value of the battery cell under the condition of the predetermined current during the vehicle driving process, and calculate the tolerance corresponding to the difference according to the SOC range, so that after the tolerance or the voltage difference value meets the corresponding preset standard, the SOC is dynamically corrected, and the SOC value to be corrected is continuously adjusted according to the preset SOC drop gradient during the discharge process, so as to correct the SOC to the SOC closest to the actual SOC. The present invention effectively avoids the situation where the vehicle breaks down early due to inaccurate SOC when the power battery pack has undervoltage problems such as self-discharge.

[0032] If the expressions expressing orientation are mentioned in the embodiments of the present invention, they are relative concepts based on the embodiments. In addition, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, a and b, a and c, b and c, or a and b and c, wherein a, b, c can be single or multiple.

[0033] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings, but the above is only a preferred embodiment of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred methods can be reasonably combined and matched into a variety of equivalent schemes by those skilled in the art without departing from or changing the design ideas and technical effects of the present invention; therefore, the present invention is not limited to the scope of implementation shown in the drawings, and all changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the specification and drawings, should be within the protection scope of the present invention.

Claims

1. A method for dynamically correcting SOC of a power battery, characterized in that: include: During the driving process of the vehicle, if the predetermined battery current condition is met, the voltage difference between the current battery cell voltage average value and the battery cell minimum voltage value is calculated; Acquire a corresponding SOC tolerance based on the pressure difference value; After the SOC tolerance or the pressure difference value meets the preset standard, the SOC is dynamically corrected, and during the discharge process, the SOC value to be corrected is continuously adjusted according to a preset SOC decrease gradient.

2. The method for dynamic correction of power battery SOC according to claim 1, characterized in that: The dynamic correction method also includes: According to a pre-calibrated open circuit voltage correction table, an open circuit voltage difference corresponding to a predetermined tolerance within a preset SOC interval is calculated as a voltage difference critical value; or, the open circuit voltage difference is combined with a preset coefficient to serve as the voltage difference critical value.

3. The method for dynamic correction of power battery SOC according to claim 2, characterized in that: The pressure difference value meets the preset standard includes: the pressure difference value is greater than the pressure difference critical value.

4. The method for dynamic correction of power battery SOC according to claim 1, characterized in that: The SOC tolerance meeting a preset standard includes: the SOC tolerance being greater than a preset SOC threshold.

5. The method for dynamic correction of power battery SOC according to claim 1, characterized in that: The preset SOC reduction gradient includes: [(SOC 原 -△SOC) / △SOC]*0.1%, where SOC 原 To represent the original value of SOC before correction, △SOC is the SOC value to be corrected.

6. The method for dynamic correction of power battery SOC according to any one of claims 1 to 5, characterized in that: The predetermined battery current condition is satisfied, including: the absolute value of the battery current is less than or equal to a preset current threshold.

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