CN113009348B - Method and device for improving power battery SOC estimation precision - Google Patents
Method and device for improving power battery SOC estimation precision Download PDFInfo
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- CN113009348B CN113009348B CN202110356825.7A CN202110356825A CN113009348B CN 113009348 B CN113009348 B CN 113009348B CN 202110356825 A CN202110356825 A CN 202110356825A CN 113009348 B CN113009348 B CN 113009348B
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/378—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC] specially adapted for the type of battery or accumulator
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
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- G01R31/385—Arrangements for measuring battery or accumulator variables
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- G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
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Abstract
The invention provides a method and a device for improving the SOC estimation precision of a power battery, belongs to the technical field of power batteries, and solves the problem that the SOC estimation method of the power battery in the prior art cannot accurately estimate the SOC, and the method for improving the SOC estimation precision of the power battery comprises the following steps: establishing a power battery equivalent circuit model; respectively obtaining a highest temperature value and a lowest temperature value of the power battery, and estimating the temperature of each other single battery by adopting a linear interpolation method according to the obtained highest temperature value and the obtained lowest temperature value; respectively looking up a table according to the temperature of each single battery to obtain related parameters of an equivalent circuit model; and calculating the open circuit voltage of each single battery by using the established equivalent circuit model and the related parameters obtained by table lookup, and further obtaining the SOC estimated value of each single battery according to each open circuit voltage. The invention can improve the accuracy of estimating the SOC of the battery model.
Description
Technical Field
The invention belongs to the technical field of power batteries, and relates to a method and a device for improving the SOC estimation precision of a power battery.
Background
The State of Charge (SOC) of a battery refers to the State of Charge (SOC) available in the battery. SOC definitions are diverse. It is now internationally unified that the definition is given from the perspective of capacity, i.e. the state of charge SOC represents the remaining capacity of the battery, which is numerically equal to the ratio of the remaining capacity of the battery to the rated capacity.
The SOC of the battery is taken as an important parameter for describing the state of the battery, so that the SOC of the battery is accurately estimated, the capacity utilization rate of the battery can be improved, and the service life of the battery can be prolonged. At present, common methods for estimating the SOC in engineering application comprise a comprehensive ampere-hour integrating method and an equivalent circuit model-based SOC estimation and open-circuit voltage correction method, wherein the ampere-hour integrating method is easy to generate accumulated errors, and the open-circuit voltage correction method needs to meet certain standing conditions and cannot realize online estimation. While the SOC can be estimated in real time based on the equivalent circuit model to correct errors of ampere-hour integration, in the conventional battery pack, due to the consideration of cost, harness structure design and the like, only two temperature sensors are usually arranged in a module with 12 strings of battery cells, but not each single battery cell has a temperature sensor, so that the conventional estimation method based on the equivalent circuit model usually carries out table lookup according to the highest temperature and the lowest temperature acquired by the two temperature sensors or the average temperature calculated according to the highest temperature and the lowest temperature to obtain model related parameters, but in the practical application of the battery pack, the temperature of each single battery cell has differences, only the highest temperature, the lowest temperature or the average temperature is adopted to carry out table lookup, so that the related parameters for acquiring the equivalent circuit model are inaccurate, and the SOC estimation precision is inaccurate.
In order to solve the problem of inaccurate SOC estimation precision, conventionally, it is easy to think that a temperature sensor is respectively arranged on each single battery so as to obtain the temperature of each single battery, but such operation not only makes the vehicle-mounted wiring more complicated and can increase the number of the jacks of the controller, the application cost is high, but also when a certain temperature sensor fails, miscalculation easily occurs to influence the accuracy of the SOC, and because the wiring of the circuit is complicated, great difficulty exists in fault detection, therefore, in general, the existing estimation method cannot obtain accurate SOC estimation.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and provides a method and a device for improving the SOC estimation precision of a power battery, wherein the technical problems to be solved are as follows: how to improve the accuracy of estimating the SOC of the battery model.
The aim of the invention can be achieved by the following technical scheme: a method of improving accuracy of SOC estimation for a power battery, the power battery being composed of a plurality of unit cells, the method comprising:
establishing an equivalent circuit model of the power battery;
the temperature values of the single battery in the highest temperature area and the single battery in the lowest temperature area of the power battery are respectively obtained, so that the temperature of each other single battery is estimated by adopting a linear interpolation method according to the obtained highest temperature value and the obtained lowest temperature value;
respectively looking up a table according to the temperature of each single battery to obtain related parameters of an equivalent circuit model;
and calculating the open circuit voltage of each single battery by using the established equivalent circuit model and the related parameters obtained by table lookup, and further obtaining the SOC estimated value of each single battery according to each open circuit voltage.
When the method for improving the SOC estimation precision of the power battery is applied, only two temperature sensors are adopted, the two temperature sensors are respectively arranged in the highest temperature area and the lowest temperature area of the power battery, the highest temperature value and the lowest temperature value are detected through the two temperature sensors, the temperature of each single battery is estimated according to the highest temperature value and the lowest temperature value, and then the estimated temperature of each single battery is subjected to table lookup to obtain the relevant parameters corresponding to the equivalent circuit model, the relevant parameters are obtained corresponding to the temperature of each single battery, the relevant parameters are obtained more accurately, a basis is provided for accurate calculation of the SOC value of each single battery, the problem that in the prior art, the relevant parameters are obtained inaccurately only by table lookup through the highest temperature, the lowest temperature or the average temperature is solved, and meanwhile, the problems that the cost is high and the circuit is complex and the like are difficult to implement due to the fact that the temperature sensors are arranged on each single battery are avoided. When calculating the SOC of each single battery, the method can look up a table according to the temperature estimated by each single battery to obtain relevant parameters corresponding to an equivalent circuit model, and then calculate the open circuit voltage of each single battery according to the equivalent circuit model, so as to obtain a corresponding SOC estimated value according to the open circuit voltage, avoid the problem of poor accuracy of the equivalent circuit model caused by calculation by adopting a temperature average value or a temperature maximum value and a temperature minimum value, and effectively solve the problem of influencing the SOC estimated accuracy due to inaccurate parameters of the equivalent circuit model by the application of the method, thereby effectively improving the accuracy of the battery SOC estimated model.
In the method for improving the SOC estimation accuracy of the power battery, the formula of the equivalent circuit model is as follows:
OCV(k+1)＝v(k+1)+R 0 i(k+1)+v 1 (k+1)；
wherein OCV (k+1) is the open circuit voltage at the current moment; v (k+1) is the battery terminal voltage at the current time, and is turned onSampling by a sensor; r is R 0 Is the ohmic internal resistance of the battery; i (k+1) is a current value at the current moment, and is obtained through sampling by a sensor; v 1 (k+1) is the battery polarization voltage at the present time.
In the method for improving the estimation accuracy of the SOC of the power battery, the battery polarization voltage v at the current time 1 (k+1) is calculated from the following formula:
wherein v is 1 (k) The battery polarization voltage at the last moment; i (k) is the current value of the previous moment, and is obtained through sampling by a sensor; r is R 1 Is the polarization internal resistance of the battery; c (C) 1 A battery polarization capacitor; Δt is the time interval.
In the method for improving the SOC estimation accuracy of the power battery, the relevant parameters of the equivalent circuit model include the ohmic internal resistance R of the battery 0 Internal resistance R of battery polarization 1 And battery polarization capacitance C 1 . Ohmic internal resistance R of battery 0 Internal resistance R of battery polarization 1 And battery polarization capacitance C 1 The parameters of the battery are obtained by respectively looking up a table according to the temperature of each single battery, and the related parameters in the equivalent circuit model are more accurate, so that the accuracy of the equivalent circuit model on SOC estimation is also improved.
In the method for improving the estimation accuracy of the SOC of the power battery, the positions of the single battery in the highest temperature region and the single battery in the lowest temperature region of the power battery are obtained in a thermal simulation mode, so that the number of the single battery in the highest temperature region and the number of the single battery in the lowest temperature region are obtained. The thermal simulation mode can accurately determine the positions of the highest temperature region and the lowest temperature region in the power battery, and further improve the accuracy of estimating the temperatures of other single batteries in the later period.
In the above method for improving SOC estimation accuracy of a power battery, the operation of estimating the temperature of each of the remaining unit batteries by using a linear interpolation method includes:
acquiring the number of each single battery in the power battery;
carrying out difference calculation on the numbers of the single batteries corresponding to the temperature maximum value and the temperature minimum value respectively to obtain a number difference;
calculating a temperature difference value between the highest temperature value and the lowest temperature value of the power battery, and dividing the temperature difference value by the calculated serial number difference value to obtain a temperature variation;
the temperature value of each single battery is estimated and obtained according to the number of the single battery and the calculated temperature variation.
The serial numbers of the single batteries in the power battery are sequentially numbered according to the arrangement sequence of the single batteries in the power battery, the serial numbers of the single batteries in the highest temperature area and the serial numbers of the single batteries in the lowest temperature area can be determined and stored in advance, when the serial numbers are applied, the sensor arranged on the single battery in the highest temperature area detects the highest temperature value, the sensor arranged on the single battery in the lowest temperature area detects the lowest temperature value, the difference value between the highest temperature value and the lowest temperature value is calculated to obtain a temperature difference value, the serial numbers of the two single batteries are calculated to obtain a serial number difference value, the temperature variation is obtained through the temperature difference value and the serial numbers of the single batteries with the temperature required to be estimated, and therefore the temperature of each single battery in the power battery can be estimated, and each single battery can calculate the SOC value according to the actual temperature of the serial numbers, and the accuracy of SOC estimation is improved.
In the above method for improving the SOC estimation accuracy of the power battery, the operation of estimating and obtaining the temperature value of each unit battery is as follows:
firstly, determining the number of a single battery needing to be subjected to temperature estimation and determining the position of the single battery in a power battery; when the number of the single battery is smaller than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a first temperature estimation formula; and when the number of the single battery is larger than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a second temperature estimation formula. According to the different positions of the single battery in the power battery, the temperature is estimated in different modes, the temperature estimation is more accurate, and the accuracy of SOC estimation can be improved.
In the above method for improving SOC estimation accuracy of a power battery, the first temperature estimation formula is:
the temperature value of the unit cell to be estimated=the temperature minimum value+the temperature change amount (the number of the unit cell to be estimated-1).
In the above method for improving SOC estimation accuracy of a power battery, the second temperature estimation formula is:
temperature value of the unit cell to be estimated = temperature minimum value + temperature change amount (total number of unit cells-number of unit cells to be estimated).
In the above method for improving SOC estimation accuracy of a power battery, the operation of obtaining the SOC estimation value of each unit battery is as follows:
and obtaining the SOC estimation value of the single battery according to the open-circuit voltage lookup table. The SOC estimated value of each single battery is obtained according to the open-circuit voltage table lookup, the table is a corresponding relation control table established by parameters such as the open-circuit voltage, the temperature and the SOC value of the battery and established by experimental data, and the SOC estimated value of each single battery can be accurately obtained by the control table.
An apparatus for improving power battery SOC estimation accuracy, comprising:
the model building module is used for building a power battery equivalent circuit model;
the temperature acquisition module is used for acquiring the highest temperature value and the lowest temperature value of the power battery;
the temperature estimation module is used for estimating the temperature of each other single battery according to the highest temperature value and the lowest temperature value acquired by the temperature acquisition module;
the model parameter acquisition module is used for respectively carrying out table lookup according to the temperature of each single battery estimated by the temperature estimation module to acquire related parameters of the equivalent circuit model;
and the SOC value calculation module is used for calculating the open circuit voltage of each single battery according to the equivalent circuit model established by the model establishment module and the related parameters obtained by the model parameter acquisition module through table lookup, and further acquiring the SOC estimated value of each single battery according to each open circuit voltage.
The device for improving the SOC estimation precision of the power battery only acquires the highest temperature value and the lowest temperature value through the temperature acquisition module, estimates the temperature of each single battery according to the highest temperature value and the lowest temperature value, and performs table lookup on the estimated temperature of each single battery to obtain the relevant parameters corresponding to the equivalent circuit model, wherein the relevant parameters are acquired corresponding to the temperature of each single battery, the relevant parameters are more accurately acquired, a basis is provided for the accurate calculation of the SOC value of each single battery by the subsequent SOC value calculation module, the problem that the acquisition of the relevant parameters is inaccurate due to the fact that the table lookup is performed only through the highest temperature, the lowest temperature or the average temperature in the prior art is solved, and meanwhile, the problems that the acquisition is performed by arranging a temperature sensor on each single battery, the cost is high, the circuit is complex and the like are avoided. When the device calculates the SOC of each single battery, the table lookup can be carried out according to the temperature estimated by each single battery to obtain the relevant parameters corresponding to the equivalent circuit model, and then the open circuit voltage of each single battery is calculated according to the equivalent circuit model, so that the corresponding SOC estimated value is obtained according to the open circuit voltage, the problem that the accuracy of the equivalent circuit model is poor due to calculation by adopting a temperature average value or a temperature maximum value and a temperature minimum value is avoided, the problem that the accuracy of the SOC estimated value is influenced due to inaccuracy of the temperature of each parameter of the equivalent circuit model is effectively solved, and the accuracy of the battery SOC estimated model is effectively improved.
In the above device for improving SOC estimation accuracy of a power battery, the temperature estimation module includes:
the single battery numbering module is used for obtaining the number of each single battery in the power battery;
the serial number difference calculation module is used for carrying out difference calculation on the serial number of the single battery corresponding to the highest temperature value and the serial number of the single battery corresponding to the lowest temperature value to obtain a serial number difference;
the single battery temperature estimation module is used for calculating and obtaining a temperature difference value between the highest temperature value and the lowest temperature value, dividing the temperature difference value with the number difference value calculated by the number difference value calculation module to obtain a temperature variation, and further estimating and obtaining the temperature value of each single battery according to the number and the temperature variation of the single battery.
Each single battery in the power battery is numbered sequentially through the single battery numbering module, the temperature acquisition module acquires the highest temperature value and the lowest temperature value, the number of the single battery corresponding to the highest temperature value and the number of the single battery corresponding to the lowest temperature value can be obtained in advance according to the position set by the temperature acquisition module, the number difference value can be calculated through the number difference value calculation module, the temperature value of each single battery can be estimated through the single battery temperature estimation module, the operation is convenient, the temperature of each single battery can be reliably acquired, and accordingly the estimation precision of the SOC value is improved.
In the above device for improving SOC estimation accuracy of a power battery, the unit battery temperature estimation module includes:
the first single battery temperature estimation submodule is used for estimating the temperature of the single battery according to a first temperature estimation formula when the number of the single battery is smaller than the number of the single battery corresponding to the highest temperature value;
and the second single battery temperature estimation submodule is used for estimating the temperature of the single battery according to a second temperature estimation formula when the number of the single battery is larger than the number of the single battery corresponding to the highest temperature value.
In the above device for improving SOC estimation accuracy of a power battery, the first temperature estimation formula is:
temperature value of the unit cell to be estimated = temperature minimum value + temperature variation (number of unit cell to be estimated-1);
the second temperature estimation formula is:
temperature value of the unit cell to be estimated = temperature minimum value + temperature change amount (total number of unit cells-number of unit cells to be estimated).
Compared with the prior art, the method and the device for improving the SOC estimation precision of the power battery have the following advantages:
1. according to the invention, the temperature of the single battery with the highest temperature and the temperature of the single battery with the lowest temperature in the power battery are detected, and then the temperature of other single batteries is estimated by adopting the linear interpolation method by utilizing the two maximum temperatures in the power battery, namely the temperature maximum value and the temperature minimum value, so that the relevant parameters of the equivalent circuit model under the corresponding temperature are obtained by looking up the table according to the temperature of each single battery, and the SOC estimation precision is further improved.
2. According to the invention, the current hardware layout of the vehicle is not required to be changed, the cost is reduced, meanwhile, the problem of each single battery can be effectively estimated, the problems of complex wiring and higher cost caused by adding a temperature sensor to each single battery are avoided, and the precision of the SOC is effectively improved in a mode of not increasing the cost.
Drawings
Fig. 1 is a schematic diagram of the control flow of the present invention.
Fig. 2 is a control flow diagram of a first embodiment of the present invention.
Fig. 3 is a control flow diagram of a second embodiment of the present invention.
Fig. 4 is a schematic control flow chart of a third embodiment of the present invention.
Fig. 5 is a control flow diagram of a fourth embodiment of the present invention.
Fig. 6 is a schematic structural view of the present invention.
In the figure, 1, a model building module; 2. a temperature acquisition module; 3. a temperature estimation module; 31. a single battery numbering module; 32. a numbering difference calculation module; 33. a single battery temperature estimation module; 33a, a single battery temperature estimation submodule I; 33b, a single battery temperature estimation submodule II; 4. the model parameter acquisition module; 5. and the SOC value calculating module.
Detailed Description
The following are specific embodiments of the present invention and the technical solutions of the present invention will be further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.
Embodiment one:
as shown in fig. 1 and 2, the method for improving the SOC estimation accuracy of the power battery includes:
the power battery equivalent circuit model is established by the following formula:
OCV(k+1)＝v(k+1)+R 0 i(k+1)+v 1 (k+1)；
wherein v is 1 (k+1) is the battery polarization voltage at the present time, which is calculated from the following formula:
wherein v is 1 (k) The battery polarization voltage at the last moment; i (k) is the current value of the previous moment, and is obtained through sampling by a sensor; r is R 1 Is the polarization internal resistance of the battery; c (C) 1 A battery polarization capacitor; Δt is the time interval. OCV (k+1) is the open circuit voltage at the current time; v (k+1) is the battery terminal voltage at the current moment and is obtained through sampling by a sensor; r is R 0 Is the ohmic internal resistance of the battery; i (k+1) is a current value at the current moment, and is obtained through sampling by a sensor; battery polarization voltage v at current time 1 (k+1)。
The temperature sensor is used for respectively detecting the temperature values of the single battery in the highest temperature area and the single battery in the lowest temperature area of the power battery to obtain the highest temperature value and the lowest temperature value, and then the temperature value of each other single battery is estimated by directly adopting a linear interpolation method according to the detected highest temperature value and the detected lowest temperature value when the power battery is used to obtain the temperature value of each single battery at the current moment. The linear interpolation method specifically comprises the following steps:
obtaining the number of each single battery in the power battery, carrying out difference calculation on the numbers of the single batteries corresponding to the highest temperature value and the lowest temperature value respectively to obtain a number difference value, then calculating the temperature difference value between the highest temperature value and the lowest temperature value of the power battery, and carrying out division calculation on the temperature difference value and the number difference value to obtain a temperature variation; acquiring the number of a single battery with the temperature to be estimated and judging the position of the single battery in the power battery; when the number of the single battery is smaller than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a first temperature estimation formula, wherein the first temperature estimation formula is as follows: temperature value of the unit cell to be estimated = temperature minimum value + temperature variation (number of unit cell to be estimated-1); when the number of the single battery is larger than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a second temperature estimation formula, wherein the second temperature estimation formula is as follows: temperature value of the unit cell to be estimated = temperature minimum value + temperature change amount (total number of unit cells-number of unit cells to be estimated).
Finally, according to the temperature of each single battery, respectively carrying out table lookup to obtain related parameters of the equivalent circuit model, wherein the related parameters comprise the ohmic internal resistance R of the battery 0 Internal resistance R of battery polarization 1 And battery polarization capacitance C 1 And substituting related parameters obtained according to different temperature lookup tables into an equivalent circuit model, and further calculating the open circuit voltage of each single battery according to the measured battery terminal voltage, the current value measured at the current moment, the current value measured at the last moment and the battery polarization voltage at the last moment, wherein the initial value of the battery polarization voltage at the last moment is assigned to be 0 when the battery polarization voltage is operated for the first time, obtaining the SOC estimated value of each single battery according to each open circuit voltage after calculating the open circuit voltage of the single battery, wherein the open circuit voltage and the SOC value are in a corresponding relation, and establishing a corresponding relation control table among the open circuit voltage, the temperature and the SOC value of the battery through experimental data. The invention effectively solves the problem of poor accuracy of calculating the SOC value of the battery model due to the large difference between the average value or the highest and lowest temperature value and the actual temperature in the prior SOC estimation methodThe method can estimate the actual temperature of each single battery, and the temperature sensor is not required to be installed on each single battery, so that the cost is reduced, the number of single batteries in the vehicle-mounted power battery is not only one or two, if the number is tens or hundreds, the temperature sensors are installed on so many single batteries to detect the actual temperature, and one sensor corresponds to 2 wire harnesses, so that the wiring of the power battery is very complex, the number of sampling connectors of a controller is increased, the cost is very high, the method only needs to set two temperature sensors to detect the highest temperature and the lowest temperature in the power battery, and the actual temperature value of the single battery can be obtained at other positions through estimation by the method, so that the problem that the parameters of an equivalent circuit model are inaccurate due to inaccurate temperature is effectively solved, the SOC estimation accuracy of the battery is influenced, and the accuracy of the SOC model is effectively improved.
As shown in fig. 6, the device for improving the SOC estimation accuracy of the power battery includes a model building module 1, a temperature acquisition module 2, a temperature estimation module 3, a model parameter acquisition module 4 and an SOC value calculation module, wherein the temperature acquisition module 2 is connected with the temperature estimation module 3, the model parameter acquisition module 4 is connected with the temperature estimation module 3, and the model parameter acquisition module 4 and the model building module 1 are both connected with the SOC value calculation module. The temperature estimation module 3 includes a cell numbering module 31, a number difference calculation module 32, and a cell temperature estimation module 33, where the cell numbering module 31 is connected to the number difference calculation module 32, the number difference calculation module 32 is connected to the cell temperature estimation module 33, and the cell temperature estimation module 33 is composed of a cell temperature estimation sub-module one 33a and a cell temperature estimation sub-module two 33 b.
The temperature acquisition module 2 comprises a first temperature sensor and a second temperature sensor, and is used for installing the first temperature sensor in a single battery where the highest temperature area is located and acquiring the highest temperature value of the power battery; and the second temperature sensor is arranged on the single battery with the lowest temperature area and is used for collecting the lowest temperature value of the power battery.
The working principle of the device for improving the SOC estimation precision of the power battery is as follows: when the SOC estimation is carried out, the temperature acquisition module 2 acquires the highest temperature value and the lowest temperature value of the power battery in real time and sends the highest temperature value and the lowest temperature value to the temperature estimation module 3, the serial number of each single battery is acquired through the single battery serial number module 31 in the temperature estimation module 3, the serial number difference calculation module 32 in the temperature estimation module 3 acquires the serial number of the single battery corresponding to the highest temperature value and the serial number of the single battery corresponding to the lowest temperature value according to the single battery serial number module 31, and carries out difference calculation on the serial numbers of the two single batteries to obtain a serial number difference value, and then the serial number difference value is sent to the single battery temperature estimation module 33 in the temperature estimation module 3. The temperature estimation module 33 performs difference calculation on the highest temperature value and the lowest temperature value acquired by the temperature acquisition module 2 to obtain a temperature difference value, and performs division calculation on the temperature difference value and the number difference value transmitted by the number difference value calculation module 32 to obtain a temperature variation, so as to estimate and obtain the temperature value of each single battery according to the number and the temperature variation of the single battery. When the temperature value of each single battery is calculated, the temperature value is calculated according to the position of the serial number of the single battery, and when the serial number of the single battery is smaller than the serial number of the single battery corresponding to the highest temperature value, the single battery temperature estimation submodule 33a estimates the temperature of the single battery according to a first temperature estimation formula, wherein the first temperature estimation formula is as follows: temperature value of the unit cell to be estimated = temperature minimum value + temperature variation (number of unit cell to be estimated-1); when the number of the single battery is greater than the number of the single battery corresponding to the highest temperature value, the second single battery temperature estimation submodule 33b estimates the temperature of the single battery according to a second temperature estimation formula, wherein the second temperature estimation formula is as follows: temperature value of the unit cell to be estimated = temperature minimum value + temperature change amount (total number of unit cells-number of unit cells to be estimated).
The cell temperature estimation module 33 transmits the temperature values of the respective cells to the model parameter acquisition module 4 after estimating the obtained temperatures of the cells,the model parameter acquisition module 4 respectively performs table lookup according to the temperature of each single battery to acquire related parameters of an equivalent circuit model, including the ohmic internal resistance R of the battery 0 Internal resistance R of battery polarization 1 And battery polarization capacitance C 1 The method comprises the steps of carrying out a first treatment on the surface of the The model parameter acquisition module 4 transmits the relevant parameters obtained by the table lookup to the SOC calculation module 5. When the SOC value calculation module calculates, substituting related parameters obtained according to different temperature lookup tables into an equivalent circuit model, and further calculating the open circuit voltage of each single battery according to the actually measured battery terminal voltage, the actually measured current value at the current moment, the actually measured current value at the last moment and the battery polarization voltage at the last moment, wherein the formula of the equivalent circuit model is as follows:
OCV(k+1)＝v(k+1)+R 0 i(k+1)+v 1 (k+1)；
wherein v is 1 (k+1) is the battery polarization voltage at the present time, which is calculated from the following formula:
wherein v is 1 (k) The battery polarization voltage at the last moment; i (k) is the current value of the previous moment, and is obtained through sampling by a sensor; r is R 1 Is the polarization internal resistance of the battery; c (C) 1 A battery polarization capacitor; Δt is the time interval. OCV (k+1) is the open circuit voltage at the current time; v (k+1) is the battery terminal voltage at the current moment and is obtained through sampling by a sensor; r is R 0 Is the ohmic internal resistance of the battery; i (k+1) is a current value at the current moment, and is obtained through sampling by a sensor; battery polarization voltage v at current time 1 (k+1). The initial value of the battery polarization voltage at the previous moment is assigned to 0 in the first running, after the open-circuit voltage of the single battery is obtained by calculation, the SOC estimated value of each single battery is obtained according to each open-circuit voltage, the open-circuit voltage and the SOC value are in a corresponding relation, and a corresponding relation control table among the open-circuit voltage, the temperature and the SOC value of the battery can be established through experimental data, so that after the open-circuit voltage of one single battery is obtained, the prestored information about the temperature and the open-circuit voltage can be inquiredThe control table of the road voltage value and the SOC value is used for obtaining the SOC estimated value of the corresponding single battery. Through the application of the device, the temperature of each single battery can be estimated only through the temperature acquisition module 2 to the highest temperature value and the lowest temperature value, then the temperature of each single battery is estimated according to the highest temperature value and the lowest temperature value, and then the estimated temperature of each single battery is subjected to table lookup to obtain the relevant parameters corresponding to the equivalent circuit model, the relevant parameters are obtained corresponding to the temperature of each single battery, the relevant parameters are obtained more accurately, a basis is provided for the accurate calculation of the SOC value of each single battery by the subsequent SOC value calculation module, the problem that the acquisition of the relevant parameters is inaccurate due to the fact that the table lookup is carried out only through the highest temperature, the lowest temperature or the average temperature in the prior art is solved, and meanwhile the problems that the acquisition is carried out due to the fact that a temperature sensor is arranged on each single battery, the cost is high, the circuit is complex and the like are avoided.
Embodiment two:
as shown in fig. 3, the technical solution in this embodiment is basically the same as that in the first embodiment, except that before the highest temperature value and the lowest temperature value are obtained, the positions of the unit cell in the highest temperature region and the unit cell in the lowest temperature region of the power cell are also confirmed in advance by a thermal simulation mode.
Embodiment III:
as shown in fig. 4, the technical scheme in this embodiment is basically the same as that in the first embodiment, except that, when the temperature estimation is performed for each unit cell, each single battery in the power battery is numbered in turn and stored in advance, and the number sequence is 1, 2 and 3.
Embodiment four:
as shown in fig. 5, the technical scheme in this embodiment is basically the same as that in the second embodiment, except that, when the temperature estimation is performed for each unit cell, each single battery in the power battery is numbered in turn and stored in advance, and the number sequence is 1, 2 and 3.
The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions thereof without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.
Claims (6)
1. A method for improving the accuracy of SOC estimation of a power battery composed of a plurality of unit cells, comprising:
establishing an equivalent circuit model of the power battery;
the method comprises the following steps of respectively obtaining the temperature values of the single battery in the highest temperature area and the single battery in the lowest temperature area of the power battery, estimating the temperature of each other single battery according to the obtained highest temperature value and the obtained lowest temperature value by adopting a linear interpolation method, wherein the operation comprises the following steps:
acquiring the number of each single battery in the power battery;
carrying out difference calculation on the numbers of the single batteries corresponding to the temperature maximum value and the temperature minimum value respectively to obtain a number difference;
calculating a temperature difference value between the highest temperature value and the lowest temperature value of the power battery, and dividing the temperature difference value by the calculated serial number difference value to obtain a temperature variation;
estimating and obtaining a temperature value of each single battery according to the serial numbers of the single batteries and the calculated and obtained temperature variation, wherein the operation is as follows:
firstly, determining the number of a single battery needing to be subjected to temperature estimation and determining the position of the single battery in a power battery; when the number of the single battery is smaller than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a first temperature estimation formula; when the number of the single battery is larger than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a second temperature estimation formula;
the first temperature estimation formula is:
temperature value of the unit cell to be estimated = temperature minimum value + temperature variation (number of unit cell to be estimated-1);
the second temperature estimation formula is:
temperature value of the unit cell to be estimated = temperature minimum value + temperature variation (total number of unit cells-number of unit cells to be estimated);
respectively looking up a table according to the temperature of each single battery to obtain related parameters of an equivalent circuit model;
and calculating the open circuit voltage of each single battery by using the established equivalent circuit model and the related parameters obtained by table lookup, and further obtaining the SOC estimated value of each single battery according to each open circuit voltage.
2. The method for improving the SOC estimation accuracy of a power battery according to claim 1, wherein the positions of the single battery in the highest temperature region and the single battery in the lowest temperature region of the power battery are obtained through a thermal simulation mode, and further the number of the single battery in the highest temperature region and the number of the single battery in the lowest temperature region are obtained.
3. The method for improving SOC estimation accuracy of a power battery of claim 1, wherein the equation of the equivalent circuit model is:
OCV(k+1)＝v(k+1)+R 0 i(k+1)+v 1 (k+1)；
wherein OCV (k+1) is the open circuit voltage at the current moment; v (k+1) is the battery terminal voltage at the current moment and is obtained through sampling by a sensor; r is R 0 Is the ohmic internal resistance of the battery; i (k+1) is a current value at the current moment, and is obtained through sampling by a sensor; v 1 (k+1) is the battery polarization voltage at the present time.
4. A method for improving accuracy of power cell SOC estimation as claimed in claim 3, wherein the battery polarization voltage v at the present time 1 (k+1) is calculated from the following formula:
wherein v is 1 (k) The battery polarization voltage at the last moment; i (k) is the current value of the previous moment, and is obtained through sampling by a sensor; r is R 1 Is the polarization internal resistance of the battery; c (C) 1 A battery polarization capacitor; Δt is the time interval.
5. An apparatus for improving SOC estimation accuracy of a power battery, comprising:
the model building module (1) is used for building a power battery equivalent circuit model;
the temperature acquisition module (2) is used for acquiring the highest temperature value and the lowest temperature value of the power battery;
the temperature estimation module (3) is used for estimating the temperature of each of the rest single batteries according to the highest temperature value and the lowest temperature value acquired by the temperature acquisition module (2); the temperature estimation module (3) comprises:
the single battery numbering module (31) is used for obtaining the number of each single battery in the power battery;
the serial number difference value calculation module (32) is used for carrying out difference value calculation on the serial number of the single battery corresponding to the highest temperature value and the serial number of the single battery corresponding to the lowest temperature value to obtain a serial number difference value;
the single battery temperature estimation module (33) is configured to calculate a temperature difference between a highest temperature value and a lowest temperature value, divide the temperature difference by a number difference calculated by the number difference calculation module (32) to obtain a temperature variation, and further estimate and obtain a temperature value of each single battery according to the number and the temperature variation of the single battery, where the operations are as follows:
firstly, determining the number of a single battery needing to be subjected to temperature estimation and determining the position of the single battery in a power battery; when the number of the single battery is smaller than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a first temperature estimation formula; when the number of the single battery is larger than the number of the single battery corresponding to the highest temperature value, estimating the temperature of the single battery according to a second temperature estimation formula;
the first temperature estimation formula is:
temperature value of the unit cell to be estimated = temperature minimum value + temperature variation (number of unit cell to be estimated-1);
the second temperature estimation formula is:
temperature value of the unit cell to be estimated = temperature minimum value + temperature variation (total number of unit cells-number of unit cells to be estimated);
the model parameter acquisition module (4) is used for respectively carrying out table lookup according to the temperature of each single battery estimated by the temperature estimation module (3) to acquire related parameters of the equivalent circuit model;
and the SOC value calculation module (5) is used for calculating the open circuit voltage of each single battery according to the equivalent circuit model established by the model establishment module (1) and the related parameters obtained by the model parameter acquisition module (4) through table lookup, and further acquiring the SOC estimated value of each single battery according to each open circuit voltage.
6. The apparatus for improving SOC estimation accuracy of a power battery according to claim 5, wherein the cell temperature estimation module (33) includes:
a first single battery temperature estimation submodule (33 a) for estimating the temperature of the single battery according to a first temperature estimation formula when the number of the single battery is smaller than the number of the single battery corresponding to the highest temperature value;
and a second single battery temperature estimation sub-module (33 b) for estimating the temperature of the single battery according to a second temperature estimation formula when the number of the single battery is greater than the number of the single battery corresponding to the highest temperature value.
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