WO2021253693A1

WO2021253693A1 - Method and system for estimating soc of hybrid power in-vehicle battery

Info

Publication number: WO2021253693A1
Application number: PCT/CN2020/121184
Authority: WO
Inventors: 樊海梅; 张巍; 李春; 熊金峰; 徐毛五; 朱恒; 张建利
Original assignee: 金龙联合汽车工业（苏州）有限公司
Priority date: 2020-06-17
Filing date: 2020-10-15
Publication date: 2021-12-23
Also published as: CN111781508A; CN111781508B

Abstract

A method for estimating the SOC of a hybrid power in-vehicle battery, comprising: determining an SOC use interval of an entire vehicle use interval; in the SOC use interval, using an ampere-hour integral method to calculate a battery SOC; calibrating a battery OCV-SOC curve, selecting a calibration interval on the basis of the gradient of the battery OCV-SOC curve; when the charging/discharging throughput of a battery reaches a set threshold, controlling the SOC use interval of the entire vehicle use interval to be open, selecting a calibration point in the calibration interval, and determining the calibration interval of the SOC; calibrating the SOC via an SOC-OCV, and changing an SOC open interval into an SOC use interval when the SOC is calibrated. The method, by employing a combined scheme of ampere-hour integration and voltage high/low-end calibration, increases the precision in estimating the SOC of a power battery.

Description

A method and system for estimating hybrid power vehicle battery SOC

Technical field

The invention belongs to the field of electric vehicle power battery management, and in particular relates to a method and system for estimating the SOC of a hybrid vehicle battery.

Background technique

An electric vehicle is a vehicle that uses an electric motor as a power device and a battery as an energy storage device. The development of electric vehicles is an emerging strategic industry that countries have vigorously developed after the energy crisis and financial crisis. Therefore, battery management is extremely important. The remaining power of the battery pack (SOC) is an important parameter of the battery management system, the most important reference basis for battery usage route planning, and the basis for power management in battery management.

SOC estimation is one of the most important parameters during battery use. High-precision SOC estimation can not only provide a good basis for the estimation of other parameters of the battery, but also enable equipment users to have a more accurate reference to the battery power.

For power batteries, there are various algorithms for estimating SOC in BMS battery management systems on the market, which can achieve a SOC accuracy of about 5% for pure electric vehicles for new energy vehicles, and an accuracy of 15% for hybrid power-type SOCs. For hybrid vehicles, in order to extend the life of their on-board batteries, the middle area of SOC is usually selected as the whole vehicle during use. This range is considered to be mainly distributed in the battery voltage platform area, and the battery usage conditions are relatively mild. But for batteries, especially lithium iron phosphate batteries, the range of use here is mainly distributed in their voltage plateau area, which makes it difficult to estimate the SOC.

Summary of the invention

In view of the above-mentioned technical problems, the purpose of the present invention is to provide a hybrid vehicle battery SOC estimation method and system, which can improve the estimation accuracy of power battery SOC by combining ampere-hour integration and voltage high and low end calibration.

The technical scheme of the present invention is:

A method for estimating the SOC of a hybrid vehicle battery includes the following steps:

S01: Determine the SOC usage interval of the entire vehicle usage range;

S02: Use the ampere-hour integral method to calculate the battery SOC in the SOC usage range;

S03: Calibrate the battery OCV-SOC curve, and select the calibration interval according to the slope of the battery OCV-SOC curve;

S04: When the battery charge and discharge throughput reaches the set threshold, the SOC usage interval that controls the usage range of the entire vehicle is opened, and the calibration point is selected in the calibration interval to determine the SOC calibration range;

S05: Calibrate the SOC through the SOC-OCV curve. When the SOC is calibrated, the SOC open interval is changed to the SOC use interval.

In a preferred technical solution, the calibration interval in step S03 includes a first calibration interval and a second calibration interval.

In a preferred technical solution, the SOC usage interval is [40, 70].

In a preferred technical solution, the threshold value set in the step S04 is 10C-15C.

The invention also discloses a system for estimating the SOC of a hybrid vehicle battery, which includes:

SOC use interval determination module: determine the SOC use interval of the vehicle's use range;

SOC calculation module: Use the ampere-hour integral method to calculate battery SOC within the SOC usage range;

Calibration interval acquisition module: calibrate the battery OCV-SOC curve, and select the calibration interval according to the slope of the battery OCV-SOC curve;

Open control module: When the battery charge and discharge throughput reaches the set threshold, the SOC use interval that controls the use range of the entire vehicle is opened, and the calibration point is selected in the calibration interval to determine the SOC calibration range;

Calibration module: Calibrate the SOC through the SOC-OCV curve. When the SOC is calibrated, the SOC open interval will be changed to the SOC use interval.

In a preferred technical solution, the calibration interval in the calibration interval acquisition module includes a first calibration interval and a second calibration interval.

In a preferred technical solution, the SOC usage interval is [40, 70].

In a preferred technical solution, the threshold value set in the open control module is 10C-15C.

Compared with the prior art, the beneficial effects of the present invention are:

The method of the present invention utilizes a combination of ampere-hour integration and voltage high and low-end calibration to calculate the battery SOC using the ampere-hour integration within the range of the entire vehicle's use of SOC. When the entire vehicle is used for a period of time, the SOC use range Open to the calibration area. When the calibration area is reached, the SOC is calibrated. After the calibration, the SOC use interval is adjusted to the original range, which can realize the calibration very easily and quickly, and improve the accuracy of the hybrid vehicle battery SOC. In turn, the service life of the battery and the power and safety performance of electric vehicles can be improved to a certain extent.

Description of the drawings

The present invention will be further described below in conjunction with the drawings and embodiments:

Fig. 1 is a flowchart of a method for estimating the SOC of a hybrid vehicle battery according to the present invention;

Figure 2 is a schematic diagram of the OCV-SOC curve of a lithium iron phosphate cathode material cell;

Figure 3 is a schematic diagram of the vehicle SOC usage interval and the calibration SOC interval.

detailed description

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary, and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concept of the present invention.

As shown in Figure 1, a method for estimating the SOC of a hybrid vehicle battery includes the following steps:

S01: Determine the SOC usage range of the vehicle usage range; for the battery OCV-SOC curve, it generally includes the interval with a large slope at both ends of the curve, and the platform area in the middle where the slope is basically unchanged, and the SOC of the vehicle usage range The use area is the platform area.

S02: In the SOC usage range, use the ampere-hour integral method C=∫Idt to calculate the battery SOC;

S03: Calibrate the battery OCV-SOC curve, select the calibration interval according to the slope of the battery OCV-SOC curve; determine the interval with the larger slope of the curve, generally located at both ends of the curve, the calibration interval includes the first calibration interval (low end area) and the second calibration Interval (high-end area); Of course, the calibration interval can also be determined by the rate of change of the slope.

S04: When the battery charge and discharge throughput reaches the set threshold, the set threshold is generally 10C-15C. The SOC use interval that controls the use range of the entire vehicle is open. Select the calibration point in the calibration interval to determine the SOC calibration range; calibrated The range is as wide as possible, for example, [0, 100] is best.

S05: Calibrate the SOC through the SOC-OCV curve. When the SOC is calibrated, the SOC open interval is changed to the SOC use interval. When the next throughput limit is reached, open calibration is performed.

The following is an example of a lithium iron phosphate battery. Of course, it is not limited to this material battery, and it is suitable for all power-type hybrid vehicle batteries.

Example 1:

An algorithm for estimating the SOC of a hybrid power battery disclosed in this embodiment includes the following steps:

Step 1. SOC whole vehicle use range is a range, this range is set as the common use range of the whole vehicle, denoted as [40, 70];

Step 2. For the battery OCV-SOC curve, as shown in Figure 2, the platform area is relatively flat, and it is generally difficult to calibrate through the platform. Therefore, the area with a large slope at both ends of the curve is selected, the high-end area [95, 100 ], the low-end zone [0, 30], the calibration zone setting should be included in the range of the high-end zone and the low-end zone;

Step 3. The use interval of hybrid vehicles is generally distributed in the platform area, especially the lithium iron phosphate battery is more obvious, so in the range of the whole vehicle use SOC interval [40, 70], use the ampere hour integral C=∫Idt to calculate the battery SOC ；

Step 4. Through calibration, when the battery charge and discharge throughput reaches 10C, control the battery to open the SOC interval of the whole vehicle, and the degree of openness reaches the range that can be calibrated [40, 100];

Step 5. When SOC=100, the battery SOC is calibrated. After calibration, the SOC open interval [40, 100] is changed to the original vehicle usage interval [40, 70], as shown in Figure 3. When the next throughput 10C is reached, open calibration is performed.

Example 2:

An algorithm for estimating the SOC of a hybrid battery disclosed in this embodiment includes the following steps:

Step 2. For the battery OCV-SOC curve, the platform area is relatively flat, and it is generally difficult to calibrate through the platform. Therefore, the area with a large slope at both ends of the curve is selected, the high-end area [95, 100], and the low-end area. [0, 30], the calibration area setting should be included in the high-end area and the low-end area;

Step 4. Through calibration, when the battery charge and discharge throughput reaches 15C, control the battery to open the SOC interval of the whole vehicle, and the degree of openness reaches the range that can be calibrated [0, 70];

Step 5. When the SOC=15, the battery SOC is calibrated, and the SOC open interval [0, 70] is changed to the original vehicle usage interval [40, 70] after the calibration is obtained. When the next throughput of 15C is reached, open calibration is performed.

Example 3:

Step 4. Through calibration, when the battery charge and discharge throughput reaches 15C, control the battery to open the SOC interval of the whole vehicle, and the degree of openness reaches the range that can be calibrated [0, 100];

Step 5. When the SOC=15 or 100, the battery SOC is calibrated, and the SOC open interval [0, 100] is changed to the original vehicle usage interval [40, 70] after the calibration is obtained. When the next throughput of 15C is reached, open calibration is performed.

It should be understood that the foregoing specific embodiments of the present invention are only used to exemplarily illustrate or explain the principle of the present invention, and do not constitute a limitation to the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundary of the appended claims, or equivalent forms of such scope and boundary.

Claims

A method for estimating the SOC of a hybrid vehicle battery, which is characterized in that it includes the following steps:

S01: Determine the SOC usage interval of the entire vehicle usage range;

S02: Use the ampere-hour integral method to calculate the battery SOC in the SOC usage range;

S03: Calibrate the battery OCV-SOC curve, and select the calibration interval according to the slope of the battery OCV-SOC curve;

S04: When the battery charge and discharge throughput reaches the set threshold, the SOC usage interval that controls the usage range of the entire vehicle is opened, and the calibration point is selected in the calibration interval to determine the SOC calibration range;

S05: Calibrate the SOC through the SOC-OCV curve. When the SOC is calibrated, the SOC open interval is changed to the SOC use interval.
The method for estimating the SOC of a hybrid vehicle battery according to claim 1, wherein the calibration interval in step S03 includes a first calibration interval and a second calibration interval.
The method for estimating the SOC of a hybrid vehicle battery according to claim 1, wherein the SOC usage interval is [40, 70].
The method for estimating the SOC of a hybrid vehicle battery according to claim 1, wherein the threshold value is set at 10C-15C in the step S04.
A system for estimating the SOC of a hybrid vehicle battery, which is characterized in that it includes:

SOC use interval determination module: determine the SOC use interval of the vehicle's use range;

SOC calculation module: Use the ampere-hour integral method to calculate battery SOC within the SOC usage range;

Calibration interval acquisition module: calibrate the battery OCV-SOC curve, and select the calibration interval according to the slope of the battery OCV-SOC curve;

Open control module: When the battery charge and discharge throughput reaches the set threshold, the SOC use interval that controls the use range of the entire vehicle is opened, and the calibration point is selected in the calibration interval to determine the SOC calibration range;

Calibration module: Calibrate the SOC through the SOC-OCV curve. When the SOC is calibrated, the SOC open interval will be changed to the SOC use interval.
The system for estimating the SOC of a hybrid vehicle battery according to claim 5, wherein the calibration interval in the calibration interval acquisition module includes a first calibration interval and a second calibration interval.
The system for estimating the SOC of a hybrid vehicle battery according to claim 5, wherein the SOC usage interval is [40, 70].
The system for estimating the SOC of a hybrid vehicle battery according to claim 5, wherein the threshold value set in the open control module is 10C-15C.