CN112158105B - New energy vehicle power battery SOH evaluation device, method and system - Google Patents

Abstract

The invention discloses a device, a method and a system for evaluating SOH of a new energy automobile power battery, belonging to the technical field of battery management, wherein the method is realized by the following steps: acquiring temperature information and voltage information of each single battery cell in the working process of the power battery; acquiring current information of a main loop in the working process of a main power battery; and obtaining characteristic values corresponding to the characteristic points of the capacity increment curve at different temperatures according to the voltage information and the current information, and evaluating the current SOH of the battery according to the Map of the characteristic points of the SOH-capacity increment curve based on the characteristic values. The method can greatly reduce the SOC range required to be spanned when estimating the SOH of the lithium ion battery, thereby improving the estimation efficiency, and is suitable for estimating the SOH of the power battery of the whole vehicle.

Description

New energy vehicle power battery SOH evaluation device, method and system

technical field

The invention belongs to the technical field of battery management, and more particularly, relates to a new energy vehicle power battery SOH evaluation device, method and system.

Background technique

At present, environmental and energy problems are becoming more and more serious, and the development of new energy vehicles has become an important strategic plan for the transformation of energy structures in various countries. The life of the power battery is an important factor affecting the stability of the service life of an electric vehicle. Due to its high energy density and long service life, lithium-ion power batteries are widely used in new energy vehicle power batteries. Through correct and rapid assessment of the state-of-health (SOH) of lithium-ion power batteries, the battery management system can timely change the control strategy according to the state of battery SOH, which can effectively improve the service life, safety and stability of lithium-ion power batteries. sex. Therefore, it is of great significance to design an accurate and efficient SOH evaluation method for the life decay characteristics of lithium-ion batteries to promote the development of new energy vehicles. There are currently two main SOH assessment methods:

(1) The capacity of the battery was directly measured by charging/discharging the battery at the rate of 1C and 1/3C on a laboratory bench. Calculate the current SOH state of the battery according to the corresponding SOH definition (SOH=Ca/Cf, where Ca is the current capacity of the battery, and Cf is the initial rated charge-discharge capacity of the new battery). However, to directly measure the battery capacity through experiments, the test process needs to span a large battery state of charge (SOC) interval (from 0% to 100%), which consumes a lot of time, and the actual use of the battery takes into account The service life of the battery, its SOC span will not be from 0% to 100%, so it is not suitable for rapid estimation on the whole vehicle.

(2) On the laboratory bench, when the battery SOC=50%, the internal resistance of the battery is measured by the three-point method under normal temperature and pressure. According to the definition of internal resistance SOH (SOH=(Reol-Ra)/(Reol) -Rf), where Reol is the internal resistance at the end of the battery life, Ra is the current internal resistance of the battery, and Rf is the initial internal resistance of the new battery) to calculate the current SOH state of the battery. However, using the three-point transmitter to measure the internal resistance of the battery requires strict test conditions, requires special charging and discharging equipment, and needs to adjust the SOC of the battery to a specified value, so it is not suitable for the actual operation of the vehicle. method.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention proposes a new energy vehicle power battery SOH evaluation device, method and system, which can greatly reduce the SOC range that needs to be spanned when evaluating the SOH of a lithium-ion battery, thereby improving the evaluation efficiency. , which is suitable for the evaluation of the SOH of the vehicle power battery.

In order to achieve the above object, according to one aspect of the present invention, a method for evaluating the SOH of a power battery for a new energy vehicle is provided, including:

Obtain the temperature information and voltage information of each single cell during the working process of the power battery; obtain the current information of the main circuit during the working process of the main power battery;

According to the voltage information and the current information, eigenvalues corresponding to the characteristic points of the capacity increment curve at different temperatures are obtained, and based on the eigenvalues, the current battery SOH is evaluated according to the map of the characteristic points of the SOH-capacity increment curve.

In some optional embodiments, the acquisition method of the characteristic point map of the SOH-capacity increment curve is:

From the charge/discharge cycle life test of the same type of lithium-ion power battery under the vehicle fast charge/slow charge power Map, the relationship between the charge capacity of each cell of the power battery and the number of cycles under different temperature conditions is calibrated, and is determined by each institute. The relationship between the charging capacity and the number of cycles can be obtained from the relationship between the actual SOH of the battery and the number of cycles;

At the corresponding temperature, the relationship between the characteristic point of the capacity increment curve and the number of cycles is established, and the relationship between the SOH and the characteristic value of the characteristic point of the capacity increment curve is established in combination with the relationship between the actual SOH of the battery and the number of cycles. The characteristic point map of the SOH-capacity curve.

由不同温度条件下动力电池各电芯的充电容量随循环次数的关系得到不同温度条件下电池实际SOH随循环次数的关系，其中，Q_a为动力电池当前充电容量，Q_b为动力电池初始标称充电容量。In some optional embodiments, by

From the relationship between the charging capacity of each cell of the power battery and the number of cycles under different temperature conditions, the relationship between the actual SOH of the battery and the number of cycles under different temperature conditions is obtained, where Q _a is the current charging capacity of the power battery, and Q _b is the initial standard of the power battery. called the charging capacity.

得到容量增量曲线dQ/dV-V曲线，其中，

Q_t为t时刻动力电池电量，Q_t-1为t-1时刻动力电池电量，V_t为t时刻动力电池电压，V_t-1为t-1时刻动力电池电压，I_t为t时刻动力电池电流。In some optional embodiments, by

The capacity increment curve dQ/dV-V curve is obtained, where,

Q _t is the power battery power at time t, Q _t-1 is the power battery power at time t-1, V _t is the power battery voltage at time t, V _t-1 is the power battery voltage at time t-1, and I _t is the power battery at time t battery current.

According to another aspect of the present invention, a new energy vehicle power battery SOH evaluation device is provided, comprising:

The information collection unit is used to obtain the temperature information and voltage information of each single cell during the working process of the power battery; and obtain the current information of the main circuit during the working process of the main power battery;

The evaluation unit is configured to obtain eigenvalues corresponding to the characteristic points of the capacity increment curve at different temperatures according to the voltage information and the current information, and based on the eigenvalues, according to the SOH-capacity increment curve characteristic point Map, the current battery SOH to evaluate.

In some optional embodiments, the acquisition method of the characteristic point map of the SOH-capacity increment curve is:

From the charge/discharge cycle life test of the same type of lithium-ion power battery under the vehicle fast charge/slow charge power Map, the relationship between the charge capacity of each cell of the power battery and the number of cycles under different temperature conditions is calibrated, and is determined by each institute. The relationship between the charging capacity and the number of cycles can be obtained from the relationship between the actual SOH of the battery and the number of cycles;

At the corresponding temperature, the relationship between the characteristic point of the capacity increment curve and the number of cycles is established, and the relationship between the SOH and the characteristic value of the characteristic point of the capacity increment curve is established in combination with the relationship between the actual SOH of the battery and the number of cycles. The characteristic point map of the SOH-capacity curve.

由不同温度条件下动力电池各电芯的充电容量随循环次数的关系得到不同温度条件下电池实际SOH随循环次数的关系，其中，Q_a为动力电池当前充电容量，Q_b为动力电池初始标称充电容量。In some optional embodiments, by

From the relationship between the charging capacity of each cell of the power battery and the number of cycles under different temperature conditions, the relationship between the actual SOH of the battery and the number of cycles under different temperature conditions is obtained, where Q _a is the current charging capacity of the power battery, and Q _b is the initial standard of the power battery. called the charging capacity.

得到容量增量曲线dQ/dV-V曲线，其中，

Q_t为t时刻动力电池电量，Q_t-1为t-1时刻动力电池电量，V_t为t时刻动力电池电压，V_t-1为t-1时刻动力电池电压，I_t为t时刻动力电池电流。In some optional embodiments, by

The capacity increment curve dQ/dV-V curve is obtained, where,

Q _t is the power battery power at time t, Q _t-1 is the power battery power at time t-1, V _t is the power battery voltage at time t, V _t-1 is the power battery voltage at time t-1, and I _t is the power battery at time t battery current.

According to another aspect of the present invention, there is provided a system including the SOH evaluation device for a power battery of a new energy vehicle described in any one of the above, and the system further includes: a battery management system;

The SOH evaluation device sends the battery SOH state to the battery management system, and the battery management system adjusts the battery usage according to the current SOH state.

In some optional embodiments, the SOH evaluation device sends the weighted average of the SOH state values calculated from the data collected in several consecutive charging processes recently to the battery management system.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

The invention has strong innovation and practicability in the SOH evaluation of the lithium-ion power battery pack of the new energy vehicle, and can pass the data collected in the actual charging process of the whole vehicle (under the whole vehicle charging power Map) in a short SOC spanning range The SOH evaluation is carried out within the system to improve the evaluation efficiency. At the same time, the corresponding capacity increment curve processing method and the corresponding reference map are adjusted for different charging states (fast/slow) to improve the evaluation accuracy and consistency. At the same time, the battery management system can adjust the battery thermal management strategy, the SOC usage range and the corresponding charging power Map according to the SOH information.

Description of drawings

1 is a schematic flowchart of a method for evaluating the SOH of a power battery for a new energy vehicle provided by an embodiment of the present invention;

2 is a schematic structural diagram of a new energy vehicle power battery SOH evaluation system provided by an embodiment of the present invention;

FIG. 3 shows the variation of an IC curve with the number of cycles and the variation of the voltage value corresponding to the peak value of the IC curve and the peak point with the number of battery cycles provided by an embodiment of the present invention, wherein (a) represents the IC curve under different cycle times. Changes, (b) represents the change of the voltage corresponding to the peak point of the IC curve with the number of cycles, (c) represents the corresponding relationship between the voltage at the peak point of the IC curve and the SOH.

Detailed ways

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 with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The invention aims to provide a system that can use the monitored relevant data to evaluate the health state SOH of a lithium ion power battery during the charging process of a new energy vehicle, and feed back the evaluation state to a battery management system. Status automatically adjusts the battery usage status to improve battery life and stability. At the same time, when evaluating the SOH, the system adjusts the corresponding algorithm and calibration map for the different charging processes of fast charging and slow charging, thereby improving the evaluation accuracy of SOH.

As shown in FIG. 1 is a schematic flowchart of a method for evaluating the SOH of a power battery of a new energy vehicle provided by an embodiment of the present invention. The method shown in FIG. 1 includes the following steps:

S1: Obtain the temperature information and voltage information of each single cell during the working process of the power battery; obtain the current information of the main circuit during the working process of the main power battery;

S2: Obtain the eigenvalues corresponding to the characteristic points of the capacity increment curve at different temperatures according to the voltage information and the current information, and evaluate the current battery SOH according to the characteristic point Map of the SOH-capacity increment curve based on the eigenvalues.

The specific hardware diagram is shown in Figure 2, including: lithium-ion power battery pack 1, single cell 2, battery management system 3, SOH evaluation device 4, fast charging interface 5, slow charging interface 6, fast charging relay 7, slow charging Charging relay 8, positive relay 9, negative relay 10, pre-charging relay 11, pre-charging resistor 12, temperature sensor 13, voltage sensor 14 and current sensor 15, wherein the temperature sensor 13 and voltage sensor 14 are placed in each single cell 2 places.

Specifically, the above temperature sensor is used to collect the temperature information of each single cell during the working process of the power battery and send it to the SOH evaluation device; the voltage sensor is used to collect the voltage information of each single cell during the working process of the power battery and send it to the SOH evaluation device. Send it to the SOH evaluation device; the current sensor connected in series to the main circuit is used to collect the main circuit current information during the working process of the main power battery and send it to the SOH evaluation device.

The above-mentioned SOH evaluation device includes: an information acquisition unit and an evaluation unit, wherein the information acquisition unit is used to receive the signals of the temperature sensor, the voltage sensor and the current sensor, and the evaluation unit is used for performing the signal according to the capacity increment method ICA and the Gaussian filtering method. process, so as to evaluate the SOH state of the power battery; the SOH evaluation device sends the evaluated SOH state to the battery management system, and the battery management system makes corresponding use adjustments according to the current SOH state of the power battery, thereby improving the service life and stability of the battery. sex.

In the embodiment of the present invention, in the process of processing the capacity increment curve, other methods may also be used to replace the Gaussian filtering method, such as the five-point three-shot method and the average moving method.

Further, the battery management system makes corresponding use adjustment according to the current SOH state of the power battery, wherein the use adjustment includes: adjusting the control strategy of the battery thermal management system, the battery SOC use range and the battery charging power Map.

Further, the evaluation unit adopts the capacity increment method ICA and Gaussian filter method to evaluate the SOH. The specific steps are as follows:

1. In the laboratory, the same type of lithium-ion power battery is subjected to the charge/discharge cycle life test under the fast charging and slow charging power Map of the whole vehicle, and the charging capacity of each cell of the power battery under different temperature conditions is calibrated with the number of cycles. , and convert it into a linear relationship between the actual SOH of the battery and the number of cycles according to formula (1); and then establish the linear relationship between the characteristic point of the capacity increment curve (the peak voltage of the curve) and the number of cycles by the least squares method at the corresponding temperature. Among them, the capacity increment method processes the collected data according to formula (2) to obtain the capacity increment curve (dQ/dV-V curve). The capacity increment curve after processing the initial data is very noisy, so Gaussian The filtering method denoises the curve. Finally, according to the above two correspondences, a linear relationship between the SOH and the characteristic value change of the characteristic point (curve peak point) of the capacity increment curve is established by the least square method.

The characteristic point map of SOH-capacity curve at different temperatures was obtained.

Among them, Q _a is the current charging capacity of the power battery, and Q _b is the initial nominal charging capacity of the power battery.

Among them, Q _t is the electricity at time t; V _t is the voltage at time t; I _t is the current at time t.

Among them, other methods can be used to replace the least squares method to establish the eigenvalue relationship between the SOH and the capacity increment curve, and the corresponding relationship between the SOH and the capacity increment curve is not necessarily a linear fit.

2. During the use of the power battery, according to the collected voltage, current and temperature information, the eigenvalues corresponding to the characteristic points of the capacity increment curve are calculated by formula (2) and formula (3), and then according to the Map map obtained from the test, The current battery SOH is evaluated. If the collected temperature or the calculated eigenvalue points are not on the corresponding Map, the intermediate interpolation method is used for calculation and correction.

In the embodiment of the present invention, in the process of estimating the SOH, the method of looking up the table may not be used, but the boundary value may be brought into the fitting formula of the Map map for direct calculation.

3. The SOH evaluation device sends the battery SOH state to the battery management system, and the battery management system adjusts the battery usage according to the current SOH state. The above usage conditions include: battery thermal management system control strategy, battery SOC usage range, and battery charging power Map. Among them, the SOH state value sent by the SOH evaluation device to the battery management system to adjust the battery usage is the weighted average of the SOH state values calculated according to the data collected in several recent consecutive charging processes, so as to reduce the evaluation error.

4. Since the characteristic value of the capacity increment curve will change under different charging rates and there are certain differences in the data processing process, the collected temperature, voltage and current information is divided into the information of the fast charging process and the information of the slow charging process. Therefore, under the different charging conditions of fast charging and slow charging of the whole vehicle, when evaluating the SOH state, the SOH evaluation module will select the corresponding algorithm and the test map of the corresponding charging rate according to different charging processes for evaluation.

5. As shown in Figure 2, when the fast charging relay, the positive relay and the negative relay are closed, and the precharging relay and the slow charging relay are disconnected, the battery is in a fast charging state; when the slow charging relay, the positive relay and the negative relay are closed, the precharging When the relay and the fast charging relay are disconnected, the battery is in a slow charging state.

The invention establishes the relationship between the characteristic value of the capacity increment curve and the power battery SOH through the capacity increment method (Incremental capacity analysis, ICA) and the Gauss filter method according to the cell voltage, current and temperature information collected during the actual charging process of the whole vehicle, In this way, the SOC range that needs to be crossed for data collection during power battery SOH evaluation can be greatly reduced, the evaluation efficiency can be improved, and the battery SOH can be quickly evaluated during vehicle use.

At the same time, when evaluating SOH, the corresponding algorithm and calibration map are adjusted for the different charging processes of fast charging and slow charging, thereby improving the consistency of SOH evaluation under different conditions. The variation of IC curve with the number of cycles, the peak value of the IC curve and the voltage value corresponding to the peak point with the number of battery cycles are shown in (a), (b) and (c) in Figure 3. Under different charging rates There are differences in the variation law and fitting curve of the characteristic points of the IC curve shown in (a), (b) and (c) in Figure 3. Therefore, when calculating and calibrating the look-up table, it needs to be adjusted to the corresponding charging rate. The IC characteristic curve.

It should be pointed out that, according to the needs of implementation, the various steps/components described in this application may be split into more steps/components, or two or more steps/components or partial operations of steps/components may be combined into new steps/components to achieve the purpose of the present invention.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (4)

1. A new energy automobile power battery SOH assessment method is characterized by comprising the following steps:

acquiring temperature information and voltage information of each single battery cell in the working process of the power battery; acquiring current information of a main loop in the working process of a main power battery;

obtaining characteristic values corresponding to capacity increment curve characteristic points at different temperatures according to the voltage information and the current information, evaluating the current battery SOH according to a Map of SOH-capacity increment curve characteristic points based on the characteristic values, if the collected temperature or the calculated characteristic value point is not on the corresponding Map, calculating and correcting by adopting an intermediate interpolation method, and when the SOH is evaluated, aiming at different charging processes of fast charging and slow charging, adjusting the SOH to an IC characteristic curve at a corresponding charging rate when calculating and calibrating table lookup;

the SOH-capacity increment curve characteristic point Map is obtained in the following mode:

the method comprises the steps that a charging/discharging cycle life test of lithium ion power batteries with the same type under the rapid charging/slow charging power Map of the whole vehicle is carried out, the relation of the charging capacity of each battery cell of the power batteries along with the cycle frequency under different temperature conditions is calibrated, and the relation of the actual SOH of the batteries along with the cycle frequency is obtained according to the relation of the charging capacity along with the cycle frequency;

establishing a relation between characteristic points of a capacity increment curve and changes of the circulation times at corresponding temperatures, and establishing a relation between the SOH and the characteristic value changes of the characteristic points of the capacity increment curve by combining the relation between the actual SOH of the battery and the circulation times to obtain an SOH-capacity curve characteristic point Map at different temperatures;

by

Obtaining the relation of the actual SOH of the battery under different temperature conditions along with the cycle number according to the relation of the charge capacity of each battery cell of the power battery along with the cycle number under different temperature conditions, wherein Q _a For the current charging capacity, Q, of the power battery _b The initial nominal charging capacity of the power battery is obtained;

by

A capacity increase curve, dQ/dV-V, is obtained, wherein,

Q _t is the electric quantity of the power battery at the time t, Q _t-1 The electric quantity of the power battery at the moment t-1, V _t Is the power battery voltage at time t, V _t-1 Power battery voltage at time t-1, I _t Is the power battery current at time t.

2. A new energy automobile power battery SOH evaluation device, characterized by includes:

the information acquisition unit is used for acquiring temperature information and voltage information of each single battery cell in the working process of the power battery; acquiring current information of a main loop in the working process of a main power battery;

the evaluation unit is used for obtaining characteristic values corresponding to capacity increment curve characteristic points at different temperatures according to the voltage information and the current information, evaluating the current SOH of the battery according to a Map of SOH-capacity increment curve characteristic points on the basis of the characteristic values, and adjusting the current SOH to an IC characteristic curve at a corresponding charging rate when calculating and calibrating a lookup table aiming at different charging processes of fast charging and slow charging when evaluating the SOH;

the acquisition mode of the Map of the characteristic point of the SOH-capacity increment curve is as follows:

the method comprises the steps that a charging/discharging cycle life test of lithium ion power batteries with the same type under the rapid charging/slow charging power Map of the whole vehicle is carried out, the relation of the charging capacity of each battery cell of the power batteries along with the cycle frequency under different temperature conditions is calibrated, and the relation of the actual SOH of the batteries along with the cycle frequency is obtained according to the relation of the charging capacity along with the cycle frequency;

establishing a relation of a capacity increment curve characteristic point along with the change of the cycle times at corresponding temperature, and establishing a relation of SOH and the change of the characteristic value of the capacity increment curve characteristic point by combining the relation of the actual SOH of the battery along with the change of the cycle times to obtain an SOH-capacity curve characteristic point Map at different temperatures;

by

Obtaining the relation of the actual SOH of the battery with the cycle times under different temperature conditions according to the relation of the charging capacity of each battery cell of the power battery with the cycle times under different temperature conditions, wherein Q _a For the current charging capacity, Q, of the power battery _b An initial nominal charging capacity for the power battery;

by

A capacity increase curve, dQ/dV-V, is obtained, wherein,

Q _t is the electric quantity of the power battery at the time t, Q _t-1 The electric quantity of the power battery at the time t-1, V _t Power cell voltage, V, at time t _t-1 The power cell voltage at time t-1,I _t is the power battery current at time t.

3. A system including the new energy vehicle power cell SOH evaluation device of claim 2, characterized in that the system further includes: a battery management system;

the SOH evaluation device sends the SOH state of the battery to the battery management system, and the battery management system adjusts the service condition of the battery according to the current SOH state.

4. The system of claim 3, wherein the SOH estimation device sends a weighted average of SOH state values calculated from data collected over a number of most recent consecutive charging processes to the battery management system.

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