CN112130077B - SOC estimation method of power battery pack under different working conditions - Google Patents

SOC estimation method of power battery pack under different working conditions Download PDF

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CN112130077B
CN112130077B CN202011073685.4A CN202011073685A CN112130077B CN 112130077 B CN112130077 B CN 112130077B CN 202011073685 A CN202011073685 A CN 202011073685A CN 112130077 B CN112130077 B CN 112130077B
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soc
battery
soc value
battery pack
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CN112130077A (en
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黄红波
刘爽
李康
周坤
孙章勇
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Dongfeng Motor Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
    • B60L58/12—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries responding to state of charge [SoC]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

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Abstract

The application relates to a method for estimating the SOC of a power battery pack under different working conditions, which comprises the following steps: under the working condition that the electric vehicle is powered on when being stopped, obtaining the SOC value of the current working condition according to the relational expression of the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage and the SOC value of the power battery at different moments; under the working condition of constant-voltage charging of the battery pack, estimating the SOC value of the current working condition by adopting an ampere-hour integration method; under the normal working condition of the battery pack, the SOC value under the current working condition is estimated by combining an ampere-hour integration method and a filtering iterative algorithm of a battery equivalent circuit model. The SOC estimation method of the power battery pack under different working conditions can be better suitable for SOC estimation under different working conditions, so that the estimation precision is higher, and the method is more reliable.

Description

SOC estimation method of power battery pack under different working conditions
Technical Field
The application relates to the technical field of new energy electric vehicles, in particular to a method for estimating the SOC of a power battery pack under different working conditions.
Background
With the popularization of new energy electric vehicles, in order to calculate the endurance mileage and control the output of battery energy more accurately, the state of charge (SOC) of a power battery needs to be estimated.
In the related art, methods for estimating the SOC of the new energy electric vehicle include an OCV open circuit voltage method, an ampere-hour integration method, a Kalman filtering method and the like. The open-circuit voltage method is only suitable for the condition that the load has no current, the ampere-hour integration method has the problem of accumulated errors, and the Kalman filtering method needs a large calculation model.
However, when estimating the SOC of the new energy electric vehicle, one of the estimation methods is usually selected to perform SOC estimation under different operating conditions, and generally, one of the estimation methods is difficult to be applied to all operating conditions, resulting in poor accuracy of SOC estimation of the power battery pack.
Disclosure of Invention
The embodiment of the application provides a method for estimating the SOC of a power battery pack under different working conditions, and aims to solve the technical problem that the SOC estimation precision of the power battery pack in the related technology is poor.
In a first aspect, a method for estimating SOC of a power battery under different operating conditions is provided, which includes the steps of:
under the working condition that the electric vehicle is powered on when being stopped, obtaining the SOC value of the current working condition according to the relational expression of the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage and the SOC value of the power battery at different moments;
under the working condition of constant-voltage charging of the battery pack, estimating the SOC value of the current working condition by adopting an ampere-hour integration method;
under the normal working condition of the battery pack, the SOC value under the current working condition is estimated by combining an ampere-hour integration method and a filtering iterative algorithm of a battery equivalent circuit model.
In some embodiments, the specific step of estimating the SOC value under the current operating condition by using the ampere-hour integration method and the filtering iterative algorithm of the battery equivalent circuit model under the normal operating condition of the battery pack includes:
estimating the SOC value of the last moment according to an ampere-hour integration method;
obtaining the SOC value of the current moment according to the SOC value of the last moment and a filtering iterative algorithm of a battery equivalent circuit model;
obtaining the open-circuit voltage at the current moment according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different moments;
according to the open circuit voltage, the bus current and the equivalent resistance R at the current moment0Internal polarization resistance R1And a polarization capacitor C1And calculating the battery pack terminal voltage U at the current moment0(m+1)；
Actually measuring battery pack terminal voltage U at current moment0′(m+1)；
According to the calculated battery pack terminal voltage U0(m +1) and the measured battery terminal voltage U0' (m +1), calculating the error epsilon of the terminal voltage of the battery pack;
and comparing the error epsilon of the terminal voltage of the battery pack with a preset error threshold, if the error epsilon of the terminal voltage of the battery pack is larger than the preset error threshold, obtaining the next moment according to a preset iteration time interval, updating the next moment to the current moment, recalculating the updated SOC value of the current moment, and calculating the error epsilon of the terminal voltage of the updated battery pack until the error epsilon of the terminal voltage of the battery pack is smaller than the preset error threshold.
In some embodiments, the previous time is t (m), the current time is t (m +1), and the calculation formula for obtaining the SOC value at the current time according to the SOC value at the previous time and the filtering iterative algorithm of the battery equivalent circuit model is as follows:
Figure GDA0003145904600000021
wherein SOC (m) is the SOC value at the last time t (m), i (m) is the bus current at the last time t (m), CNFor the rated capacity of the battery, Δ t is the time interval between the current time t (m +1) and the last time t (m), and SOC (m +1) is the SOC value of the current time t (m + 1).
In some embodiments, the open-circuit voltage V at the current time t (m +1) is obtained according to the relationship between the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different timeskThe step of (m +1) includes:
carrying out charge and discharge tests on power batteries with different temperatures and different aging degrees in advance to obtain the relationship among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different moments;
monitoring the temperature and the aging degree of the battery pack in real time;
after obtaining the SOC value at the current time t (m +1), obtaining the open-circuit voltage V at the current time t (m +1) according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different timesk(m+1)。
In some embodiments, the battery pack terminal voltage U is calculated based on the battery pack terminal voltage U0(m +1) and the measured battery terminal voltage U0' (m +1), and the calculation formula of the error epsilon of the battery terminal voltage is calculated as follows:
Figure GDA0003145904600000031
in the formula of U0(m +1) isThe battery terminal voltage U at the current time t (m +1) is calculated0' (m +1) is the battery terminal voltage at the current time t (m +1) measured actually.
In some embodiments, the predetermined error threshold is 1%.
In some embodiments, the step of obtaining the SOC value of the current operating condition according to the relationship among the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage, and the SOC value at different times under the power-on operating condition of the electric vehicle during parking includes:
when the power-off time during parking is greater than a preset time threshold, obtaining the internal resistance of the battery pack at the current moment according to the relation among the aging degree, the battery temperature and the internal resistance of the battery at different moments, calculating the open-circuit voltage value at the current moment, and obtaining the SOC value at the current moment according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value, namely the SOC value at the current working condition;
when the power-off time during parking is less than a preset time threshold, obtaining the open-circuit voltage at the current moment according to the relation between the time in the OCV rebound curve and the open-circuit voltage, and obtaining the SOC value at the current moment according to the relation between the aging degree, the battery temperature, the open-circuit voltage and the SOC value, namely the SOC value under the current working condition.
In some embodiments, before obtaining the SOC value of the current operating condition according to the relationship among the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage, and the SOC value at different times, the method further includes the steps of:
testing power batteries with different temperatures and different aging degrees under the condition that the power-off time during parking is greater than a preset time threshold value in advance to obtain the aging degrees, the relationship between the battery temperature and the internal resistance of the battery and the relationship between the aging degrees, the battery temperature, the open-circuit voltage and the SOC value at different moments;
and testing the power batteries with different temperatures and different aging degrees under the condition that the power-off time is less than a preset time threshold value in advance to obtain an OCV (open circuit voltage) rebound curve and the relationship between the aging degree, the battery temperature, the open-circuit voltage and the SOC value.
In some embodiments, the equation for estimating the SOC value of the current operating condition by using the ampere-hour integration method under the constant-voltage charging operating condition of the battery pack is as follows:
Figure GDA0003145904600000041
in formula (II) is SOC'0The initial value of SOC under the constant voltage charging condition is shown, CN is the rated capacity of the battery, mu is the charging and discharging efficiency, I is the battery current, and SOC (m +1) is the SOC value at the current time t (m + 1).
In some embodiments, the initial value of the SOC under the constant-voltage charging condition is an SOC value of the battery pack in a full-charge state.
The beneficial effect that technical scheme that this application provided brought includes: the method can be better suitable for SOC estimation under different working conditions, so that the estimation precision is higher, and the method is more reliable.
The embodiment of the application provides an SOC estimation method of a power battery pack under different working conditions, on one hand, different estimation methods are adopted according to different working conditions, so that the SOC estimation method can be better suitable for SOC estimation under different working conditions, the estimation precision is higher, and the method is more reliable; on the other hand, factors such as aging degree and battery temperature are fully considered when the SOC is estimated, so that the estimated SOC value is more accurate and the accuracy is higher.
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In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flowchart of a method for estimating SOC of a power battery pack under different operating conditions according to an embodiment of the present disclosure;
fig. 2 is a battery equivalent circuit model provided in an embodiment of the present application;
fig. 3 is a flowchart illustrating specific steps of estimating an SOC value under a current operating condition under a normal operating condition of a battery pack according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, an embodiment of the present application provides a method for estimating SOC of a power battery pack under different operating conditions, which includes the steps of:
a1: under the working condition that the electric vehicle is powered on when being stopped, obtaining the SOC value of the current working condition according to the relational expression of the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage and the SOC value at different moments;
a2: under the working condition of constant-voltage charging of the battery pack, estimating the SOC value of the current working condition by adopting an ampere-hour integration method;
a3: under the normal working condition of the battery pack, the SOC value under the current working condition is estimated by combining an ampere-hour integration method and a filtering iterative algorithm of a battery equivalent circuit model. The normal working condition of the embodiment of the application is a battery pack discharging working condition.
According to the SOC estimation method of the power battery pack under different working conditions, on one hand, different estimation methods are adopted according to different working conditions, so that the SOC estimation method can be better suitable for SOC estimation under different working conditions, the estimation precision is higher, and the method is more reliable; on the other hand, factors such as aging degree and battery temperature are fully considered when the SOC is estimated, so that the estimated SOC value is more accurate and the accuracy is higher.
Referring to the battery equivalent circuit model, U, of the battery pack shown in FIG. 20(t) battery terminal voltage, i (t) bus current, VkFor open circuit voltage, resistor R0The resistance R1 is the polarization internal resistance, the capacitance C1To polarize the capacitance, Uc(t) is a polarization capacitanceA terminal voltage.
Further, in this embodiment of the present application, in step a3, the step of estimating the SOC value under the current operating condition by using the ampere-hour integration method and the filtering iterative algorithm of the battery equivalent circuit model under the normal operating condition of the battery pack includes:
estimating the SOC value of the last moment according to an ampere-hour integration method;
obtaining the SOC value of the current moment according to the SOC value of the last moment and a filtering iterative algorithm of a battery equivalent circuit model;
obtaining the open-circuit voltage at the current moment according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different moments;
according to the open circuit voltage, the bus current and the equivalent resistance R at the current moment0Internal polarization resistance R1And a polarization capacitor C1And calculating the battery pack terminal voltage U at the current moment0(m+1)；
Actually measuring battery pack terminal voltage U at current moment0′(m+1)；
According to the calculated battery pack terminal voltage U0(m +1) and the measured battery terminal voltage U0' (m +1), calculating the error epsilon of the terminal voltage of the battery pack;
and comparing the error epsilon of the terminal voltage of the battery pack with a preset error threshold, if the error epsilon of the terminal voltage of the battery pack is larger than the preset error threshold, obtaining the next moment according to a preset iteration time interval, updating the next moment to the current moment, recalculating the updated SOC value of the current moment, and calculating the error epsilon of the terminal voltage of the updated battery pack until the error epsilon of the terminal voltage of the battery pack is smaller than the preset error threshold.
Furthermore, in this embodiment of the present application, the previous time is t (m), the current time is t (m +1), and the calculation formula for obtaining the SOC value at the current time according to the SOC value at the previous time and the filtering iterative algorithm of the battery equivalent circuit model is as follows:
Figure GDA0003145904600000061
wherein SOC (m) is the SOC value at the last time t (m), i (m) is the bus current at the last time t (m), CNFor the rated capacity of the battery, Δ t is the time interval between the current time t (m +1) and the last time t (m), and SOC (m +1) is the SOC value of the current time t (m + 1).
Furthermore, in the embodiment of the present application, the open-circuit voltage V at the current time t (m +1) is obtained according to the relationship between the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different timeskThe step of (m +1) includes:
carrying out charge and discharge tests on power batteries with different temperatures and different aging degrees in advance to obtain the relationship among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different moments;
monitoring the temperature and the aging degree of the battery pack in real time;
after obtaining the SOC value at the current time t (m +1), obtaining the open-circuit voltage V at the current time t (m +1) according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different timesk(m+1)。
Further, in the embodiment of the present application, the battery pack terminal voltage U obtained by calculation0(m +1) and the measured battery terminal voltage U0' (m +1), and the calculation formula of the error epsilon of the battery terminal voltage is calculated as follows:
Figure GDA0003145904600000071
in the formula of U0(m +1) is the calculated battery terminal voltage at the current time t (m +1), U0' (m +1) is the battery terminal voltage at the current time t (m +1) measured actually.
Specifically, in the embodiment of the present application, the preset error threshold is 1%.
Referring to fig. 3, in the embodiment of the present application, taking the previous time as t (m), the current time as t (m +1), and the next time as t (m +2) as an example, the specific steps of estimating the SOC value under the current operating condition under the normal operating condition of the battery pack include:
s1: the last moment is t (m), the SOC value (SOC) of the last moment is estimated according to an ampere-hour integration method, and the calculation formula is as follows:
Figure GDA0003145904600000072
in the formula, SOC0Is an initial value of SOC, CNThe battery rated capacity is shown, mu is the charge-discharge efficiency, I is the battery current, and SOC (m) is the SOC value at the last moment t (m);
s2: obtaining the SOC value SOC (m +1) at the current moment according to the SOC value SOC (m) at the previous moment and a filtering iterative algorithm of a battery equivalent circuit model, wherein the calculation formula is as follows;
Figure GDA0003145904600000081
wherein SOC (m) is the SOC value at the last time t (m), i (m) is the bus current at the last time t (m), CNFor the rated capacity of the battery, Δ t is the time interval between the current time t (m +1) and the last time t (m), and SOC (m +1) is the SOC value of the current time t (m + 1);
s3: obtaining the open-circuit voltage V of the current time t (m +1) according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different momentsk(m+1)；
S4: open circuit voltage V according to current time t (m +1)k(m +1), bus current i (m +1), and equivalent resistance R0Internal polarization resistance R1And a polarization capacitor C1And calculating the battery pack terminal voltage U at the current time t (m +1)0(m+1)；
S5: actually measuring battery pack terminal voltage U at current time t (m +1)0′(m+1)；
S6: according to the calculated battery pack terminal voltage U0(m +1) and the measured battery terminal voltage U0' (m +1), calculating the error epsilon of the terminal voltage of the battery pack, and the calculation formula is as follows:
Figure GDA0003145904600000082
in the formula of U0(m +1) is the calculated battery terminal voltage at the current time t (m +1), U0' (m +1) is the battery terminal voltage at the current time t (m +1) measured actually;
s7: comparing the error epsilon of the battery pack terminal voltage with a preset error threshold, specifically, judging whether the error epsilon of the battery pack terminal voltage is larger than the preset error threshold, if so, turning to the step S8, and if not, turning to the step S9;
s8: obtaining the next time t (m +2) according to a preset iteration time interval, updating the next time t (m +2) to the current time, and turning to the step S2;
s9: and exiting iteration, and taking the corrected SOC value as the SOC value under the current working condition.
Furthermore, in this embodiment of the application, the step of obtaining the SOC value of the current operating condition according to the relation among the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage, and the SOC value at different times under the power-on operating condition of the electric vehicle during parking includes:
when the power-off time during parking is greater than a preset time threshold, obtaining the internal resistance of the battery pack at the current moment according to the relation among the aging degree, the battery temperature and the internal resistance of the battery at different moments, calculating the open-circuit voltage value at the current moment, and obtaining the SOC value at the current moment according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value, namely the SOC value at the current working condition;
when the power-off time during parking is less than a preset time threshold, obtaining the open-circuit voltage at the current moment according to the relation between the time in the OCV rebound curve and the open-circuit voltage, and obtaining the SOC value at the current moment according to the relation between the aging degree, the battery temperature, the open-circuit voltage and the SOC value, namely the SOC value under the current working condition.
The preset time threshold value of the embodiment of the application is usually half an hour, when the power-off time during parking is greater than the preset time threshold value, the polarization voltage of the battery pack can be considered to be eliminated, and according to the known relationship among the aging degree, the battery temperature and the battery internal resistance at different moments, the internal resistance of the battery pack at the current moment can be obtained, so that the SOC value of the current working condition is obtained; when the power-off time during parking is smaller than a preset time threshold value, and the polarization voltage of the battery pack exists, the open-circuit voltage at the current moment is obtained according to the relation between the time and the open-circuit voltage in the OCV rebound curve, and further the SOC value under the current working condition is obtained.
In the embodiment of the application, different estimation methods are adopted according to different working conditions, and the factors of aging degree and temperature are fully considered to estimate the SOC value, so that the estimated SOC value is more accurate and has higher precision.
Furthermore, in this embodiment of the present application, before obtaining the SOC value of the current operating condition according to the relationship among the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage, and the SOC value at different times, the method further includes the steps of:
testing power batteries with different temperatures and different aging degrees under the condition that the power-off time during parking is greater than a preset time threshold value in advance to obtain the aging degrees, the relationship between the battery temperature and the internal resistance of the battery and the relationship between the aging degrees, the battery temperature, the open-circuit voltage and the SOC value at different moments;
and testing the power batteries with different temperatures and different aging degrees under the condition that the power-off time is less than a preset time threshold value in advance to obtain an OCV (open circuit voltage) rebound curve and the relationship between the aging degree, the battery temperature, the open-circuit voltage and the SOC value.
It should be noted that, in the embodiment of the present application, a plurality of sets of tests need to be performed in advance, and the tests are performed under different working conditions respectively to obtain the relational expression between the parameters under the corresponding working conditions, and when the SOC value of the current working condition is estimated, the corresponding SOC value can be obtained directly according to the known relational expression, so that the estimation speed can be faster.
Furthermore, in this embodiment of the present application, the equation for estimating the SOC value of the current operating condition by using the ampere-hour integration method under the constant voltage charging operating condition of the battery pack is as follows:
Figure GDA0003145904600000101
in formula (II) is SOC'0Is the initial value of SOC under the constant voltage charging condition, CNIn terms of the rated capacity of the battery, μ is the charge-discharge efficiency, I is the battery current, and SOC (m +1) is the SOC value at the present time t (m + 1).
Specifically, in the embodiment of the present application, the initial value of the SOC under the constant-voltage charging condition is an SOC value of the battery pack in a full-charge state.
In the embodiment of the application, when the battery pack is under the working condition of constant-voltage charging, the equivalent circuit model is not suitable, the ampere-hour integration method is more accurate, the precision is higher, a more appropriate SOC estimation method is selected according to different working conditions, and the reliability is better.
In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. A method for estimating the SOC of a power battery pack under different working conditions is characterized by comprising the following steps:
under the working condition that the electric vehicle is powered on when being stopped, obtaining the SOC value of the current working condition according to the relational expression of the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage and the SOC value of the power battery at different moments;
under the working condition of constant-voltage charging of the battery pack, estimating the SOC value of the current working condition by adopting an ampere-hour integration method;
under the normal working condition of the battery pack, estimating the SOC value under the current working condition by combining an ampere-hour integration method and a filtering iterative algorithm of a battery equivalent circuit model;
under the normal working condition of the battery pack, the specific steps of estimating the SOC value under the current working condition by combining the ampere-hour integration method and the filtering iterative algorithm of the battery equivalent circuit model comprise:
estimating the SOC value of the last moment according to an ampere-hour integration method;
obtaining the SOC value of the current moment according to the SOC value of the last moment and a filtering iterative algorithm of a battery equivalent circuit model;
obtaining the open-circuit voltage at the current moment according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different moments;
according to the open circuit voltage, the bus current and the equivalent resistance R at the current moment0Internal polarization resistance R1And a polarization capacitor C1And calculating the battery pack terminal voltage U at the current moment0(m+1)；
Actually measuring battery pack terminal voltage U at current moment0′(m+1)；
According to the calculated battery pack terminal voltage U0(m +1) and the measured battery terminal voltage U0' (m +1), calculating the error epsilon of the terminal voltage of the battery pack;
and comparing the error epsilon of the terminal voltage of the battery pack with a preset error threshold, if the error epsilon of the terminal voltage of the battery pack is larger than the preset error threshold, obtaining the next moment according to a preset iteration time interval, updating the next moment to the current moment, recalculating the updated SOC value of the current moment, and calculating the error epsilon of the terminal voltage of the updated battery pack until the error epsilon of the terminal voltage of the battery pack is smaller than the preset error threshold.
2. The method for estimating the SOC of the power battery pack under different operating conditions according to claim 1, wherein the previous time is t (m), the current time is t (m +1), and the calculation formula for obtaining the SOC value at the current time according to the SOC value at the previous time and the filtering iterative algorithm of the battery equivalent circuit model is as follows:
Figure FDA0003145904590000021
wherein SOC (m) is the SOC value at the last time t (m), i (m) is the bus current at the last time t (m), CNFor the rated capacity of the battery, Δ t is the time interval between the current time t (m +1) and the last time t (m), and SOC (m +1) is the SOC value of the current time t (m + 1).
3. The variable operating condition of claim 1The SOC estimation method of the lower power battery pack is characterized in that the open-circuit voltage V at the current time t (m +1) is obtained according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different timeskThe step of (m +1) includes:
carrying out charge and discharge tests on power batteries with different temperatures and different aging degrees in advance to obtain the relationship among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different moments;
monitoring the temperature and the aging degree of the battery pack in real time;
after obtaining the SOC value at the current time t (m +1), obtaining the open-circuit voltage V at the current time t (m +1) according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value at different timesk(m+1)。
4. The method for estimating the SOC of a power battery pack under different working conditions as claimed in claim 1, wherein the battery pack terminal voltage U is obtained according to the calculation0(m +1) and the measured battery terminal voltage U0' (m +1), and the calculation formula of the error epsilon of the battery terminal voltage is calculated as follows:
Figure FDA0003145904590000022
in the formula of U0(m +1) is the calculated battery terminal voltage at the current time t (m +1), U0' (m +1) is the battery terminal voltage at the current time t (m +1) measured actually.
5. The method for estimating the SOC of the power battery pack under different working conditions as claimed in claim 4, wherein the predetermined error threshold is 1%.
6. The method for estimating the SOC of the power battery pack under different operating conditions according to claim 1, wherein the step of obtaining the SOC value under the current operating condition according to the relationship among the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage and the SOC value at different times under the power-on operating condition when the electric vehicle is stopped comprises:
when the power-off time during parking is greater than a preset time threshold, obtaining the internal resistance of the battery pack at the current moment according to the relation among the aging degree, the battery temperature and the internal resistance of the battery at different moments, calculating the open-circuit voltage value at the current moment, and obtaining the SOC value at the current moment according to the relation among the aging degree, the battery temperature, the open-circuit voltage and the SOC value, namely the SOC value at the current working condition;
when the power-off time during parking is less than a preset time threshold, obtaining the open-circuit voltage at the current moment according to the relation between the time in the OCV rebound curve and the open-circuit voltage, and obtaining the SOC value at the current moment according to the relation between the aging degree, the battery temperature, the open-circuit voltage and the SOC value, namely the SOC value under the current working condition.
7. The method for estimating the SOC of the power battery pack under different operating conditions according to claim 6, wherein before obtaining the SOC value under the current operating condition according to the relational expressions of the aging degree, the battery temperature, the battery internal resistance, the open-circuit voltage and the SOC value at different times, the method further comprises the steps of:
testing power batteries with different temperatures and different aging degrees under the condition that the power-off time during parking is greater than a preset time threshold value in advance to obtain the aging degrees, the relationship between the battery temperature and the internal resistance of the battery and the relationship between the aging degrees, the battery temperature, the open-circuit voltage and the SOC value at different moments;
and testing the power batteries with different temperatures and different aging degrees under the condition that the power-off time is less than a preset time threshold value in advance to obtain an OCV (open circuit voltage) rebound curve and the relationship between the aging degree, the battery temperature, the open-circuit voltage and the SOC value.
8. The method for estimating the SOC of the power battery pack under different working conditions as claimed in claim 1, wherein the calculation formula for estimating the SOC value under the current working condition by using an ampere-hour integration method under the working condition of constant voltage charging of the battery pack is as follows:
Figure FDA0003145904590000031
in formula (II) is SOC'0Is the initial value of SOC under the constant voltage charging condition, CNIn terms of the rated capacity of the battery, μ is the charge-discharge efficiency, I is the battery current, and SOC (m +1) is the SOC value at the present time t (m + 1).
9. The method for estimating the SOC of the power battery pack under different operating conditions according to claim 8, wherein the initial value of the SOC under the constant voltage charging operating condition is the SOC value of the battery pack under a full state.
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