Method for dynamically correcting soc of power battery

Abstract

The application discloses a power battery SOC dynamic correction method, and the main design concept of the application is that, in the condition that the current meets the established condition in the vehicle driving process, the difference between the average voltage of the battery monomer and the minimum voltage of the battery monomer is calculated, the tolerance corresponding to the difference is calculated according to the SOC range, and the SOC is dynamically corrected after the tolerance or the voltage difference value meets the corresponding preset standard, and the SOC value to be corrected is continuously adjusted according to the preset SOC descending gradient in the discharging process, so that the SOC is corrected to the most close to the actual SOC. The application effectively avoids the situation that the vehicle is in advance in the prone position due to the inaccurate SOC when the power battery pack has the self-discharge and other under-voltage problems.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, and in particular to a method for dynamic correction of the state of charge (SOC) of a power battery. Background Technology

[0002] As the energy source for new energy electric vehicles, the power battery's safe and effective battery management system is a key technology for the development of the electric vehicle industry. To ensure that vehicles meet people's requirements for driving range and safe driving under complex real-world operating conditions, accurately estimating and correcting the power battery's state of charge (SOC) has significant engineering application implications.

[0003] Currently, Open Circuit Voltage Correction (OCV) is the most accurate SOC correction method. However, due to the characteristics of SOC-OCV, it requires more than 30 minutes of rest before accurate table lookup, which is difficult to achieve while the vehicle is in motion, often resulting in vehicles breaking down prematurely. Summary of the Invention

[0004] In view of the above, the present invention aims to provide a method for dynamic correction of the state of charge (SOC) of a power battery to solve the aforementioned technical problems.

[0005] The technical solution adopted in this invention is as follows:

[0006] This invention provides a method for dynamic correction of the state of charge (SOC) of a power battery, including:

[0007] During vehicle operation, if the predetermined battery current conditions are met, the voltage difference between the current average voltage of a single battery cell and the minimum voltage of a single battery cell is calculated.

[0008] The corresponding SOC tolerance is obtained based on the pressure difference value;

[0009] After the SOC tolerance or the differential pressure 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 decrease gradient during the discharge process.

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

[0011] Based on a pre-calibrated open-circuit voltage correction table, calculate the open-circuit voltage difference corresponding to a predetermined tolerance within a preset SOC range, and use it as the critical value of the voltage difference; or, combine the open-circuit voltage difference with a preset coefficient, and use it as the critical value of the voltage difference.

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

[0013] In at least one of the possible implementations, the SOC tolerance conforming to the preset standard includes: the SOC tolerance being greater than a preset SOC threshold.

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

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

[0016] Compared with existing technologies, the main design concept of this invention lies in calculating the difference between the average voltage of a battery cell and the minimum voltage of a battery cell under the condition of a fixed current during vehicle operation. Based on the State of Charge (SOC) range, the tolerance corresponding to this difference is calculated. Then, after the tolerance or voltage difference value meets the corresponding preset standards, the SOC is dynamically corrected. During discharge, the SOC value to be corrected is continuously adjusted according to a preset SOC descent gradient, thereby correcting the SOC to be as close as possible to the actual SOC. This invention effectively avoids the situation where the vehicle breaks down prematurely due to inaccurate SOC when the power battery pack has undervoltage problems such as self-discharge. Attached Figure Description

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings, wherein:

[0018] Figure 1 This is a schematic diagram of the dynamic correction method for the SOC of a power battery provided in an embodiment of the present invention. Detailed Implementation

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

[0020] This invention proposes an embodiment of a dynamic correction method for the state of charge (SOC) of a power battery, specifically, as follows: Figure 1 As shown, it includes:

[0021] Step S1: During vehicle operation, if the predetermined battery current conditions are met, calculate the voltage difference between the current average voltage of a battery cell and the minimum voltage of a battery cell.

[0022] Step S2: Obtain the corresponding SOC tolerance based on the pressure difference value;

[0023] Step S3: After the SOC tolerance or the differential pressure 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 decrease gradient during the discharge process.

[0024] To elaborate, when the battery current is discharged while the vehicle is in motion, and the absolute value of the battery current is ≤5A (this threshold is adjustable as needed), calculate V. cell平均 With V cellmin The difference ΔV is calculated, and then the corresponding SOC tolerance is calculated based on the preset voltage range. This is because the SOC is usually calculated by ampere-hour integration during vehicle discharge, and the capacity difference caused by undervoltage cannot be actively identified when the battery reference capacity remains unchanged.

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

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

[0027] Calculate the open-circuit voltage difference with a 5% tolerance in the preset SOC range in advance based on the pre-calibrated open-circuit voltage correction table (Table 1 attached below); for example, in the SOC ∈ [95,100] range, at Tmin=25℃ (for other SOC ranges, take linear interpolation at each temperature), △OCV=61mV; furthermore, considering consistency, △OCV can be multiplied by a coefficient of 1.2 as the critical value of the voltage difference with a tolerance greater than 5%.

[0028] Table 1

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

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

[0031] In summary, the main design concept of this invention lies in calculating the difference between the average voltage of a battery cell and its minimum voltage under the condition of a fixed current during vehicle operation. Based on the State of Charge (SOC) range, the tolerance corresponding to this difference is calculated. Then, after the tolerance or voltage difference value meets the corresponding preset standards, the SOC is dynamically corrected. During discharge, the SOC value to be corrected is continuously adjusted according to a preset SOC descent gradient, thereby correcting the SOC to be as close as possible to the actual SOC. This invention effectively avoids the situation where the vehicle breaks down prematurely due to inaccurate SOC when the power battery pack has undervoltage problems such as self-discharge.

[0032] In this invention, when directional terms are mentioned, they are relative concepts based on the embodiments. Furthermore, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have 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 represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0033] The above description of the structure, features, and effects of the present invention is based on the embodiments shown in the figures. However, the above are only preferred embodiments 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 by those skilled in the art to form a variety of equivalent solutions without departing from or changing the design concept and technical effects of the present invention. Therefore, the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method for dynamic correction of the state of charge (SOC) of a power battery, characterized in that, include: During vehicle operation, if the predetermined battery current conditions are met, the predetermined battery current conditions include: the absolute value of the battery current is less than or equal to a preset current threshold, then the voltage difference between the current average voltage of the battery cells and the minimum voltage of the battery cells is calculated. The corresponding SOC tolerance is obtained based on the pressure difference value; After the SOC tolerance or the differential pressure 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 decrease gradient during the discharge process; wherein... The pressure difference value meets the preset standard including: the pressure difference value is greater than the pressure difference critical value; the pressure difference critical value is obtained by calculating the open circuit voltage difference within the preset SOC range corresponding to the predetermined tolerance based on the preset open circuit voltage correction table, or by combining the open circuit voltage difference with a preset coefficient; The preset SOC descent gradient includes: [(SOC 原 -ΔSOC) / ΔSOC]*0.1%, where SOC 原 To characterize the original value of SOC before correction, △SOC is the SOC value that needs to be corrected.

2. The power battery SOC dynamic correction method according to claim 1, characterized in that, SOC tolerance meets preset standards, including: SOC tolerance is greater than the preset SOC threshold.

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