CN117318252A - Battery pack charge and discharge protection method and device - Google Patents

Battery pack charge and discharge protection method and device Download PDF

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Publication number
CN117318252A
CN117318252A CN202311612656.4A CN202311612656A CN117318252A CN 117318252 A CN117318252 A CN 117318252A CN 202311612656 A CN202311612656 A CN 202311612656A CN 117318252 A CN117318252 A CN 117318252A
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battery pack
soc
value
voltage
threshold
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CN117318252B (en
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白昊
雷健华
马辉
林成慧
胡锦
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Shenzhen Delian Minghai New Energy Co ltd
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Shenzhen Delian Minghai New Energy Co ltd
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    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

The invention discloses a battery pack charge and discharge protection method and a device, wherein the battery pack charge and discharge protection method comprises the following steps: acquiring voltage differential pressure at each moment in the charging or discharging process of a battery pack, and calculating a corresponding charging threshold or discharging threshold according to the voltage differential pressure, wherein the voltage differential pressure is the difference value between the highest voltage and the lowest voltage of all battery cores in the battery pack; monitoring that the battery pack is in a charged stateSOCWhen the value is in a first preset interval, judging whether the voltage difference is larger than the charging threshold value, and if so, performing overcharge protection on the battery pack; monitoring that the battery pack is in a discharge stateSOCAnd when the value is in a second preset interval, judging whether the voltage difference is larger than the discharge threshold value, and if so, performing over-discharge protection on the battery pack. The invention dynamically adjusts the SOC threshold value to realize overcharge/overdischarge protection in the whole life cycle of the battery pack.

Description

Battery pack charge and discharge protection method and device
Technical Field
The invention relates to the technical field of energy storage equipment, in particular to a battery pack charge and discharge protection method and device.
Background
In the energy storage system in the new energy field, a plurality of single battery cells are often combined into a battery pack, and then one battery pack or a plurality of battery packs are combined into an energy storage battery. The energy storage battery is used as a core component in the energy storage system, and plays a key role in the overall reliability, safety and service life of the energy storage system when the energy storage battery is used in a proper working condition environment as much as possible. Because the battery cells in the battery pack alternate reciprocally between the charging working condition and the discharging working condition in the actual use process, the battery cells can reach the conditions of deep overcharging or deep overdischarging. If the abnormality of the battery cell cannot be identified in advance, the overcharge may cause potential safety hazards such as combustion and explosion of the battery cell, and the overdischarge may cause the problems such as obvious attenuation of the whole capacity of the battery pack.
The foregoing background is only for the purpose of facilitating an understanding of the principles and concepts of the invention and is not necessarily in the prior art to the present application and is not intended to be used as an admission that such background is not entitled to antedate such novelty and creativity by the present application without undue evidence prior to the present application.
Disclosure of Invention
In order to solve the technical problems, the invention provides a battery pack charge-discharge protection method and device, which dynamically adjusts an SOC threshold value to realize overcharge/overdischarge protection in the whole life cycle of the battery pack.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in a first aspect, the invention discloses a battery pack charge-discharge protection method, which comprises the following steps:
s1: acquiring voltage differential pressure at each moment in the charging or discharging process of a battery pack, and calculating a corresponding charging threshold or discharging threshold according to the voltage differential pressure, wherein the voltage differential pressure is the difference value between the highest voltage and the lowest voltage of all battery cores in the battery pack;
s2: monitoring toThe battery pack is in a charged stateSOCWhen the value is in a first preset interval, judging whether the voltage difference is larger than the charging threshold value, and if so, performing overcharge protection on the battery pack; monitoring that the battery pack is in a discharge stateSOCAnd when the value is in a second preset interval, judging whether the voltage difference is larger than the discharge threshold value, and if so, performing over-discharge protection on the battery pack.
Preferably, step S1 specifically includes:
s11: acquiring voltage differences at various moments in the charging or discharging process of the battery pack;
s12: for the battery packSOCDiscretizing the values to form the battery packSOCDividing a value into a plurality ofSOCA level interval;
s13: acquiring each ofSOCAn extremum of the voltage differential of the battery pack within the class interval;
s14: according to eachSOCThe extreme value of the voltage difference of the battery pack in the level interval is calculated in the charging or discharging process of the battery packSOCAn average value of the extreme values of the voltage differences with values within a third preset interval;
s15: and (4) calculating a corresponding charge threshold or discharge threshold according to the average value calculated in the step (S14).
Preferably, step S15 specifically includes:
s151: calculating the charge or discharge process of the battery pack according to the average value calculated in the step S14SOCStandard deviation of the extreme value of the voltage difference with the value within the third preset interval;
s152: and (3) calculating a corresponding charging threshold or discharging threshold according to the average value calculated in the step (S14) and the standard deviation calculated in the step (S151), wherein the charging threshold or the discharging threshold is equal to the sum of the average value and the standard deviation which is 3 times.
Preferably, eachSOCThe extreme value of the voltage difference of the battery pack in the level interval is respectivelySOCMaximum value or each of the voltage differences of the battery packs in the level intervalsSOCAnd the minimum value of the voltage difference of the battery pack in the level interval.
Preferably, the first preset interval is greater than or equal to a firstSOCA threshold value, wherein the second preset interval is smaller than or equal to a secondSOCA threshold value.
Preferably, the firstSOCThe threshold value is 85% -95%, and the secondSOCThe threshold value is 5% -15%.
In a second aspect, the present invention discloses a battery pack charge-discharge protection device, comprising:
the acquisition and calculation module is used for acquiring voltage difference at each moment in the charging or discharging process of the battery pack and calculating a corresponding charging threshold or discharging threshold according to the voltage difference, wherein the voltage difference is the difference between the highest voltage and the lowest voltage of all the battery cells in the battery pack;
the monitoring and judging module is used for monitoring that the battery pack is in a charging state andSOCwhen the value is in a first preset interval, judging whether the voltage difference is larger than the charging threshold value or not; and upon detecting that the battery pack is in a discharge state andSOCwhen the value is in a second preset interval, judging whether the voltage difference is larger than the discharge threshold value or not;
and the charge-discharge protection module is used for carrying out overcharge protection on the battery pack when the monitoring and judging module judges that the voltage differential is larger than the charge threshold value, and carrying out overdischarge protection on the battery pack when the monitoring and judging module judges that the voltage differential is larger than the discharge threshold value.
Preferably, the acquiring and calculating module is used for acquiring voltage differences at various moments in the charging or discharging process of the battery pack; for the battery packSOCDiscretizing the values to form the battery packSOCDividing a value into a plurality ofSOCA level interval; acquired at each ofSOCAn extremum of the voltage differential of the battery pack within the class interval; according to eachSOCThe extreme value of the voltage difference of the battery pack in the level interval is calculated in the charging or discharging process of the battery packSOCAn average value of the extreme values of the voltage differences with values within a third preset interval; and calculating a corresponding charging threshold or discharging threshold according to the average value.
Preferably, eachSOCThe extreme value of the voltage difference of the battery pack in the level interval is respectivelySOCMaximum value or each of the voltage differences of the battery packs in the level intervalsSOCAnd the minimum value of the voltage difference of the battery pack in the level interval.
In a third aspect, the present invention discloses a computer readable storage medium having a computer program stored therein, wherein the computer program is configured to be executed by a processor to perform the battery pack charge and discharge protection method according to the first aspect.
Compared with the prior art, the invention has the beneficial effects that: according to the battery pack charge and discharge protection method and device disclosed by the invention, the charge threshold value/discharge threshold value is dynamically adjusted according to the voltage differential pressure at each moment acquired in the charge process or the discharge process based on the real-time voltage data of the battery cell, so that the problem of misjudgment caused by using a fixed SOC threshold value in the traditional method is effectively solved, and the problem of deviation of the overcharge/overdischarge threshold value caused by SOH (solid state of charge) drop at the end of the life cycle of the battery cell in the traditional method is avoided. In addition, at different stages of the life cycle of the battery, the most practical charging/discharging threshold value is obtained by utilizing the voltage data of the battery core in the last time or the current charging/discharging process, so that the energy is maximally utilized on the premise of ensuring the safety of the battery pack. In addition, the method has the characteristics of simple implementation and small calculation amount, and is easy to realize on edge equipment.
Drawings
Fig. 1 is a flow chart illustrating a battery pack charge-discharge protection method according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram showing a specific flow of step S1 in FIG. 1;
fig. 3 is a flowchart of a battery pack charge protection method according to a first embodiment of the invention;
fig. 4 is a flowchart of a battery pack discharge protection method according to a second embodiment of the invention;
FIG. 5a is a timing diagram of the highest voltage, the lowest voltage and the voltage difference during charging of the battery pack according to an embodiment of the present invention;
FIG. 5b is a timing diagram of voltage differential across an overcharge protection zone for a battery pack according to one embodiment of the present invention;
FIG. 6a is a timing diagram of the highest voltage, the lowest voltage and the voltage difference during discharging of the battery pack according to the embodiment of the present invention;
fig. 6b is a timing chart of voltage differential between the battery pack and the over-discharge protection zone according to an embodiment of the present invention.
Detailed Description
The following describes embodiments of the present invention in detail. It should be emphasized that the following description is merely exemplary in nature and is in no way intended to limit the scope of the invention or its applications.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for both the fixing action and the circuit/signal communication action.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are merely for convenience in describing embodiments of the invention and to simplify the description by referring to the figures, rather than to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless explicitly defined otherwise.
The following description will be given of the terms used in this application.
BMS: battery Management System the battery management system, commonly called battery manager, is mainly used for intelligently managing and maintaining each battery unit, preventing the battery from being overcharged and overdischarged, prolonging the service life of the battery, and monitoring the state of the battery. For an excellent BMS, the battery parameters of the battery pack can be estimated online in real time to accurately estimate the battery packSOC、SOP、SOHAnd can correct the initial in a short timeSOCErrors exceeding 10% and errors exceeding 20% of ampere-hour capacity or current measurement errors of a few percent will be quite excellent.
SOC: the state of charge reflects the remaining battery power;SOP: state capable of providing powerSOPCan maximize the efficiency of battery utilization), based on a variety of factorsSOCThe battery pack can support discharge power or charging power at different temperatures;SOH: the state of health of the battery comprises two parts: ampere-hour capacity and power.
Because the battery cell overcharge has the risks of causing fire and the like, the battery cell overdischarge can cause the problems of short service life of the battery pack and the like, so that all the battery cells in the battery pack are ensured to be in the optimal working state as much as possible, and the battery cell overdischarge protection device has great significance on the safety and reliability of an energy storage system. In the prior art, batteries are currently being used by battery management systemsSOCValue and fixedSOCComparing the threshold values; when the battery is in useSOCTriggering over-discharge protection after the value is lower than a preset discharge threshold value, and when the battery is in a battery stateSOCAnd triggering overcharge protection after the value is higher than a preset charge threshold. However, the charge and discharge states of the different battery packs are different, and the battery packs have the following characteristics in the whole life cycleSOHThe value will also decay continuously with increasing use time. The use of a fixed SOC threshold may result in erroneous decisions regarding the overcharge/overdischarge conditions. Based on the shortcomings of the prior art, the preferred embodiment of the present invention achieves overcharging/overdischarging in the full life cycle of a battery pack by dynamically adjusting the charge/discharge threshold by analyzing the battery pack operating stateAnd (5) protection.
As shown in fig. 1, the preferred embodiment of the invention discloses a battery pack charge-discharge protection method, which comprises the following steps:
s1: acquiring voltage differential pressure at each moment in the charging or discharging process of the battery pack, and calculating a corresponding charging threshold or discharging threshold according to the voltage differential pressure, wherein the voltage differential pressure refers to the difference value between the highest voltage and the lowest voltage of all battery cells in the battery pack;
the charging threshold is calculated according to the voltage difference of each moment in the charging process of the battery pack, and the discharging threshold is calculated according to the voltage difference of each moment in the discharging process of the battery pack.
Specifically, as shown in fig. 2, step S1 specifically includes:
s11: acquiring voltage differences at various moments in the charging or discharging process of the battery pack;
s12: for battery packsSOCDiscretizing the values to form a battery packSOCDividing a value into a plurality ofSOCA level interval;
s13: acquiring each ofSOCExtreme values of voltage differences of battery packs in the level intervals;
wherein each ofSOCThe extreme value of the voltage difference of the battery pack in the level interval is respectivelySOCMaximum value of voltage difference of battery pack in level interval or eachSOCMinimum value of voltage differential of battery pack in level interval.
S14: according to eachSOCExtreme value of voltage difference of battery pack in level interval, calculating battery pack charging or discharging processSOCAn average value of the extreme values of the voltage differences with values within a third preset interval;
wherein the third preset interval can be the charging process or discharging process in any acquisition time periodSOCThe range of values, for example, the third preset interval may take [10%,90 ]]Alternatively [12%,33 ]]、[45%，87%]Etc.
S15: and (4) calculating a corresponding charge threshold or discharge threshold according to the average value calculated in the step (S14).
The step S15 specifically includes:
s151: calculated according to step S14The average value is calculated in the charging or discharging process of the battery packSOCStandard deviation of the extreme value of the voltage difference with the value within the third preset interval;
s152: and (3) calculating a corresponding charging threshold or discharging threshold according to the average value calculated in the step (S14) and the standard deviation calculated in the step (S151), wherein the charging threshold or discharging threshold is equal to the sum of the average value and the standard deviation which is 3 times.
S2: monitoring that the battery pack is in a charged stateSOCWhen the value is in a first preset interval, judging whether the voltage difference is larger than a charging threshold value, and if so, performing overcharge protection on the battery pack; monitoring that the battery pack is in a discharge stateSOCAnd when the value is in the second preset interval, judging whether the voltage difference is larger than a discharge threshold value, and if so, performing over-discharge protection on the battery pack.
Wherein the first preset interval is greater than or equal to the firstSOCThreshold, firstSOCThe threshold value can be specifically 85% -95%; the second preset interval is less than or equal to the secondSOCThreshold value, secondSOCThe threshold value can be specifically 5% -15%.
Another preferred embodiment of the present invention discloses a battery pack charge-discharge protection device, comprising:
the acquisition and calculation module is used for acquiring voltage differential pressure at each moment in the charging or discharging process of the battery pack, and calculating a corresponding charging threshold value or discharging threshold value according to the voltage differential pressure, wherein the voltage differential pressure refers to the difference value between the highest voltage and the lowest voltage of all the battery cells in the battery pack;
further, the acquisition and calculation module is used for acquiring voltage differences at various moments in the charging or discharging process of the battery pack; for battery packsSOCDiscretizing the values to form a battery packSOCDividing a value into a plurality ofSOCA level interval; acquired at each ofSOCExtreme values of voltage differences of battery packs in the level intervals; according to eachSOCExtreme value of voltage difference of battery pack in level interval, calculating battery pack charging or discharging processSOCAn average value of the extreme values of the voltage differences with values within a third preset interval; and calculating a corresponding charging threshold value or discharging threshold value according to the average value. Wherein,each of which isSOCThe extreme value of the voltage difference of the battery pack in the level interval is respectivelySOCMaximum value of voltage difference of battery pack in level interval or eachSOCMinimum value of voltage differential of battery pack in level interval.
The calculating the corresponding charge threshold or discharge threshold according to the average value specifically includes: calculating the charge or discharge process of the battery pack according to the average valueSOCStandard deviation of the extreme value of the voltage difference with the value within the third preset interval; and calculating a corresponding charging threshold or discharging threshold according to the average value and the standard deviation, wherein the charging threshold or discharging threshold is equal to the sum of the average value and the standard deviation which is 3 times. Wherein the third preset interval can be the charging process or discharging process in any acquisition time periodSOCThe range of values, for example, the third preset interval may take [10%,90 ]]Alternatively [12%,33 ]]、[45%，87%]Etc.
The monitoring and judging module is used for monitoring that the battery pack is in a charging state andSOCwhen the value is in a first preset interval, judging whether the voltage difference is larger than a charging threshold value or not; and when the battery pack is detected to be in a discharging stateSOCWhen the value is in the second preset interval, judging whether the voltage difference is larger than a discharge threshold value or not; wherein the first preset interval is greater than or equal to the firstSOCThreshold, firstSOCThe threshold value can be specifically 85% -95%; the second preset interval is less than or equal to the secondSOCThreshold value, secondSOCThe threshold value can be specifically 5% -15%.
And the charge-discharge protection module is used for performing over-charge protection on the battery pack when the voltage difference is judged to be larger than the charge threshold by the monitoring and judging module, and performing over-discharge protection on the battery pack when the voltage difference is judged to be larger than the discharge threshold by the monitoring and judging module.
Another preferred embodiment of the present invention discloses a computer readable storage medium having a computer program stored therein, wherein the computer program is configured to be run by a processor to perform the steps of the battery pack charge and discharge protection method of the preferred embodiment described above. The computer readable storage medium may be directly applied to the BMS to implement overcharge/overdischarge protection in the full life cycle of the battery pack.
Alternatively, the storage medium may include, but is not limited to: a usb disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a removable hard disk, a magnetic disk, or an optical disk, or other various media capable of storing a computer program.
The following describes the battery pack charge-discharge protection method according to the preferred embodiment of the present invention in further detail.
In the following embodiments one and two, according to conventional practice, when implementing the battery pack charge-discharge protection method, a constant current charge-discharge cycle of a complete cycle may be performed on all the cells in the battery pack, and the whole charge process is performed from the battery packSOC(t) Start charging to 0SOC(t) =100, the whole discharging process from the battery packSOC(t) Start discharge at 100SOC(t)=0。
Determining sampling period during charging or discharging of battery packTEach time instant recorded in the sampling periodtHighest voltage for charging all battery cells in battery packAnd minimum voltage->Maximum voltage of all cell discharge voltages +.>And minimum voltage->Current battery powerSOC(t). The following data recorded based on the sampling period provides a battery pack charge protection method and a battery pack discharge protection method.
Example 1
As shown in fig. 3, the embodiment discloses a battery pack charging protection method, which includes the following steps:
A0：acquiring battery pack in sampling time periodTEach time withintHighest voltage of all cell chargesAnd minimum voltage->And the current battery levelSOC(t)。
A1: calculating the battery pack at each momenttVoltage difference between highest voltage and lowest voltage of the whole battery pack:
；
wherein,indicating the highest voltage in all cells of the battery pack during charging,representing the lowest voltage of all the cells of the battery pack during charging, < >>。
A2: for a pair ofSOC(t) Discretizing, and setting level difference：
；
Wherein,a number greater than 0 and less than 1; />，NIs after discretizationSOC(t) Is a number of levels of (a).
The value of (2) is greater than 0 and less than 100%, such as 0.2%, 0.5%, 1%,2%, 5%, 10%, etc., specifically, whenWhen the value is 1%, the drug is added with%>Correspondingly, each ofSOCThe grade interval is 0-1%, 1-2%, 2-3%, … …, 99-100%, the grade number isN100; when->When the value is 10%, the medicine is prepared from the Chinese medicinal materials including the following materials (by weight percent)>Correspondingly, each ofSOCThe grade intervals are 0-10%, 10-20%, 20-30%, … … and 90-100%, and the grade number is as followsN10.
A3: calculated at each ofSOCMaximum value of battery pack voltage difference in the level interval:
；
wherein,representing a maximum function>Is thatSOC(t) The voltage difference of the battery pack corresponding to the value in the charging process,SOC(t) The value range is->. At each of theSOCWithin the level interval, there are multiple momentstEvery moment of timetAre all corresponding to voltage differences according to each momenttFurther acquiring the voltage difference of each of the stepsSOCMaximum value of the battery pack voltage difference in the level interval.
In this embodiment, the maximum value of the voltage difference in the whole battery pack is used as a reference for calculation, that is: each during chargingSOCUnder the level interval, the condition that the voltage difference of the battery pack is maximum is concerned; therefore, in the charging process, all the battery cells in the battery pack can be charged to the level similar to the voltage, and the consistency among all the battery cells is ensured as much as possible.
A4: calculation ofAverage value of maximum voltage difference between 10% -90%:
；
wherein,is that the battery pack is in each +.>Maximum voltage difference corresponding to the value, +.>The value range is->，MRepresentation->And the grade number is between 10% and 90%.
A5: calculation ofStandard deviation of maximum voltage differential between 10% -90%:
；
wherein,is that the battery is packed in the step A3Each->The maximum voltage differential corresponding to the value,is calculated in step A4 +.>Average value of the maximum voltage difference between 10% -90%.
A6: calculating a charging threshold:
；
wherein,is the calculation of +.>An average value of the maximum voltage difference between 10% and 90%,is the calculation of +.>Standard deviation of maximum voltage difference between 10% -90%.
A7: according to the charging threshold valueThe charging state of the battery pack is judged in the following specific modes:
if it is currently locatedSOCLevel ofAnd when the voltage difference is->When the protection device is in the open state, the overcharge protection is started;
if it is currently locatedSOCLevel ofCharging is continued.
In the battery pack charge protection method disclosed in the first embodiment, step A3 calculates the maximum voltage difference of the battery pack, and step A4 and step A5 calculate the average value of the maximum voltage difference and the standard deviation of the maximum voltage difference, respectively; in other embodiments, step A3 may also calculate the minimum voltage difference of the battery pack, and in step A4 and step A5, calculate the average value of the minimum voltage difference and the standard deviation of the minimum voltage difference, respectively, so as to calculate the charging threshold according to step A6, where the charging threshold calculated by taking the average value of the maximum voltage difference and the standard deviation of the maximum voltage difference represents that the charging protection is more relaxed; the charge threshold calculated by taking the average value of the minimum voltage difference and the standard deviation of the minimum voltage difference represents that the charge protection is more strict.
Example two
As shown in fig. 4, the embodiment discloses a battery pack discharge protection method, which includes the following steps:
b0: acquiring battery pack in sampling time periodTEach time withintHighest voltage of all cell dischargesAnd minimum voltage->And corresponding current battery levelSOC(t)。
B1: calculating the battery pack at each momenttVoltage difference between highest voltage and lowest voltage of the whole battery pack:
；
wherein,indicating the highest voltage in all cells of the battery pack during discharge,representing the lowest voltage of all the cells of the battery pack during discharging +.>。
B2: for a pair ofSOC(t) Discretizing to design very bad：
；
Wherein,a number greater than 0 and less than 1; />，NIs after discretizationSOC(t) Is a number of levels of (a).
B3: calculated at each ofSOCMinimum value of battery pack voltage differential in the level interval:
；
wherein,representing taking the minimum function +_>Is thatSOC(t) The voltage difference of the battery pack corresponding to the value in the discharging process,SOC(t) The value range is->. In this embodiment, the minimum value of the voltage difference in the whole battery pack is used as the reference for calculation, namely: each during dischargeSOCUnder the level, the condition that the voltage difference in the battery pack is minimum is concerned; thereby enabling to let during the discharging processAll the electric cores in the battery pack fully release electric energy as much as possible, and the load requirement is met.
B4: calculation ofAverage value of minimum voltage difference between 10% -90%:
；
wherein,is that the battery pack is in each +.>The minimum voltage differential corresponding to the value,the value range is->，MRepresentation->And the grade number is between 10% and 90%.
B5: calculation ofStandard deviation of minimum voltage differential between 10% -90%:
；
wherein,is that the battery pack is in each +.>The minimum voltage differential corresponding to the value,is calculated in step B4 +.>Average value of minimum voltage difference between 10% -90%.
B6: calculating a discharge threshold:
；
wherein,is the calculation of +.>An average value of the maximum voltage difference between 10% and 90%,is the calculation of +.>Standard deviation of maximum voltage difference between 10% -90%.
B7: according to the discharge threshold valueThe discharging state of the battery pack is judged in the following specific modes:
if the current SOC level isAnd when the voltage difference is->And when the over-discharge protection is started.
If the current SOC level isThe discharge is continued.
In the battery pack discharging protection method disclosed in the second embodiment, step B3 calculates the minimum voltage difference of the battery pack, and step B4 and step B5 calculate the average value of the minimum voltage difference and the standard deviation of the minimum voltage difference, respectively; in other embodiments, step B3 may also calculate the maximum voltage difference of the battery pack, and in steps B4 and B5, calculate the average value of the maximum voltage difference and the standard deviation of the maximum voltage difference, respectively, and further calculate the discharge threshold according to step B6, where the discharge threshold calculated by taking the average value of the minimum voltage difference and the standard deviation of the minimum voltage difference represents that the discharge protection is stricter; the discharge threshold calculated by taking the average value of the maximum voltage difference and the standard deviation of the maximum voltage difference represents a more relaxed discharge protection.
Example III
In the first and second embodiments described above, the data obtained when the battery pack is fully charged and discharged is based. It should be noted that the battery pack charge-discharge protection method of the present invention is also applicable to the case of not fully charged discharge. In the preferred embodiment, the charging and discharging process does not necessarily need to be fully charged (i.e., the SOC must be between 0-100%) at the time of sampling. For example, in the charging process steps A4 and A5, calculation is performedThe maximum differential pressure average value and standard deviation between 10% and 90%, the calculation range can be set as +.>Wherein->Is started by chargingSOCValue of->At the end of chargingSOCThe value only needs to be guaranteed +.>The preparation method is finished; correspondingly, in the steps A0 to A3, only the battery pack may be usedSOCValues atWithin the range. Correspondingly, in the discharging process steps B4 and B5,the calculation range can also be set asWherein->Is started by dischargeSOCValue of->Is the end of dischargeSOCValue only has to be ensuredThe preparation method is finished; correspondingly, in the steps B0 to B3, only the battery pack may be usedSOCThe value is +.>Within the range. Therefore, the protection of the overcharge/overdischarge of the battery pack under the condition of being closer to daily practical use can be realized, and the practicability of the method is further expanded; and the calculation amount of data is less, and the implementation is easier.
According to the battery pack charge protection method or the discharge protection method disclosed by the embodiment of the invention, the charge/discharge threshold value is dynamically adjusted according to the last charge/discharge process or the current charge/discharge process, so that different charge/discharge threshold values are adopted to carry out adaptive overcharge/overdischarge protection at different stages in the life cycle of the battery, and the maximum energy utilization under the premise of ensuring the safety of the battery pack is realized. In addition, on one hand, the embodiment of the invention has the characteristics of simple implementation and small calculation amount, and is easy to realize on edge equipment; on the other hand, the embodiment of the invention can provide overcharge and overdischarge protection for the battery pack in the whole life cycle based on the real-time voltage data of the battery cell; avoiding the problem of the traditional method at the end of the life cycle of the battery cell due toSOHThe overcharge/overdischarge threshold value deviation problem caused by the drop.
The following method for protecting charge and discharge of a battery pack disclosed in the embodiment of the invention dynamically adjusts overcharge/overdischarge protection for a battery pack including 16 cells.
(1) Overcharge protection
To battery packageAll the battery cells are subjected to constant current charge and discharge circulation in a complete period, and the whole charge process is carried outSOCCharging is started when the value is 0, and all the electric cores of the battery pack are obtained at each momenttHighest voltage and lowest voltage of (2) and the current timeSOC(t) Values. Calculating each time of battery packtThe voltage difference between the highest voltage and the lowest voltage is calculated specifically and referred to an overcharge protection method to realize the step A1; for a pair ofSOC(t) Discretizing, designing level differenceMake->Values of (2%). 100% from these voltage differences are found from 0,1% >, 2% >>Maximum differential pressure of value>Calculate->The average value and standard deviation of the maximum pressure difference with the value between 10% and 90%, and the step A4 and the step A5 are realized by specifically calculating and referring to the overcharge protection method; calculate the charge threshold +.>The step A6 is realized by referring to an overcharge protection method in a concrete calculation mode; if the value of the current SOC is 90% or more, and the voltage difference +.>When the protection device is in the open state, the overcharge protection is started; if the value of the current SOC is less than 90, charging is continued. The results are shown in FIG. 5a and FIG. 5b, FIG. 5a is a biaxial graph showing the trend of the highest voltage and the lowest voltage of all the battery cells and the trend of the voltage difference during the charging process of the battery pack, and FIG. 5b is a graph showing the charging process of the battery pack to +.>Voltage differential timing diagram of (2) and charge thresholdValue->It can be seen that at +.>After that, the voltage difference starts to rise sharply, the rising speed is far higher than that of all the previous charging processes, so when the voltage difference is larger than the charging threshold, the consistency of the cell voltage in the battery pack is very bad (for example +.>When corresponding toSOCLevel interval->The voltage difference values of the battery packs at each time instant in (a) are very different, i.e. correspond to +_ in FIG. 5b>The corresponding columns have a plurality of points), and at the moment, the stability of the voltage value of the battery core can be well controlled by starting the charging protection, so that the battery pack is protected; as can be seen from fig. 5b, the battery pack of the overcharge protection zone is +.>。
(2) Over-discharge protection
The whole discharging process is carried out bySOCDischarging is started when the value is 100%, and all the electric cores of the battery pack are obtained at each momenttHighest voltage and lowest voltage of (2) and the current timeSOC(t) Values. Calculating each time of battery packtB1 is realized by referring to an over-discharge protection method in specific calculation; for a pair ofDiscretizing, designing level differenceMake->Values of (2) are from 100%,99%,98%,. 0, found from these voltage differences +.>Minimum differential pressure of valueCalculate->The average value and standard deviation of the minimum pressure difference with the value between 10% and 90%, and the specific calculation refers to the over-discharge protection method to realize the step B4 and the step B5; calculate discharge threshold +.>B6, realizing the step by referring to the overdischarge protection method in a concrete calculation mode; if the current SOC value is less than or equal to 10%, and the voltage difference is +.>When the over-discharge protection is started; and if the current SOC value is more than 10%, continuing discharging. The results are shown in FIG. 6a and FIG. 6b, FIG. 6a is a biaxial graph showing the trend of the highest voltage and the lowest voltage of all the battery cells and the trend of the voltage difference during the discharging process of the battery pack, and FIG. 6b is a graph showing the discharging process of the battery to +.>The subsequent voltage difference time sequence diagram and the corresponding discharge threshold +.>It can be seen that at +.>Then, the voltage difference starts to rise sharply, and the rising speed is far higher than that of all the previous discharging processes, so that when the voltage difference is larger than a discharging threshold value, the consistency of the voltage of the battery core in the battery pack is very poor, and at the moment, the discharging protection is started to well control the stability of the voltage value, so that the battery pack is protected; as can be seen from fig. 6b, the battery pack of the overdischarge protection section is +.>。
Those of ordinary skill in the art will recognize that while the present invention only shows one full cycle constant current charge-discharge cycle embodiment, there is no limitation to the use scenario of the present invention. Modifications and variations may be made without departing from the scope of the method described above. Including but not limited to, changing the value range of the SOC value when calculating the average value in the overcharge/discharge protection, not using constant current for charge and discharge, and calculating the threshold value. The scope of the invention should be understood to cover such modifications as well as other insubstantial variations not listed.
The background section of the present invention may contain background information about the problem or environment of the present invention rather than the prior art described by others. Accordingly, inclusion in the background section is not an admission of prior art by the applicant.
The foregoing is a further detailed description of the invention in connection with specific/preferred embodiments, and it is not intended that the invention be limited to such description. It will be apparent to those skilled in the art that several alternatives or modifications can be made to the described embodiments without departing from the spirit of the invention, and these alternatives or modifications should be considered to be within the scope of the invention. In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope as defined by the appended claims.

Claims (10)

1. The battery pack charge and discharge protection method is characterized by comprising the following steps of:
s1: acquiring voltage differential pressure at each moment in the charging or discharging process of a battery pack, and calculating a corresponding charging threshold or discharging threshold according to the voltage differential pressure, wherein the voltage differential pressure is the difference value between the highest voltage and the lowest voltage of all battery cores in the battery pack;
s2: monitoring that the battery pack is in a charged stateSOCWhen the value is in a first preset interval, judging whether the voltage difference is larger than the charging threshold value, and if so, performing overcharge protection on the battery pack; monitoring that the battery pack is in a discharge stateSOCAnd when the value is in a second preset interval, judging whether the voltage difference is larger than the discharge threshold value, and if so, performing over-discharge protection on the battery pack.
2. The battery pack charge-discharge protection method according to claim 1, wherein step S1 specifically comprises:
s11: acquiring voltage differences at various moments in the charging or discharging process of the battery pack;
s12: for the battery packSOCDiscretizing the values to form the battery packSOCDividing a value into a plurality ofSOCA level interval;
s13: acquiring each ofSOCAn extremum of the voltage differential of the battery pack within the class interval;
s14: according to eachSOCThe extreme value of the voltage difference of the battery pack in the level interval is calculated in the charging or discharging process of the battery packSOCAn average value of the extreme values of the voltage differences with values within a third preset interval;
s15: and (4) calculating a corresponding charge threshold or discharge threshold according to the average value calculated in the step (S14).
3. The battery pack charge-discharge protection method according to claim 2, wherein step S15 specifically includes:
s151: calculating the charge or discharge process of the battery pack according to the average value calculated in the step S14SOCStandard deviation of the extreme value of the voltage difference with the value within the third preset interval;
s152: and (3) calculating a corresponding charging threshold or discharging threshold according to the average value calculated in the step (S14) and the standard deviation calculated in the step (S151), wherein the charging threshold or the discharging threshold is equal to the sum of the average value and the standard deviation which is 3 times.
4. The battery pack charge-discharge protection method according to claim 2, wherein each ofSOCThe extreme value of the voltage difference of the battery pack in the level interval is respectivelySOCMaximum value or each of the voltage differences of the battery packs in the level intervalsSOCAnd the minimum value of the voltage difference of the battery pack in the level interval.
5. The battery pack charge-discharge protection method according to claim 1, wherein the first preset interval is greater than or equal to a first intervalSOCA threshold value, wherein the second preset interval is smaller than or equal to a secondSOCA threshold value.
6. The battery pack charge-discharge protection method according to claim 5, wherein the firstSOCThe threshold value is 85% -95%, and the secondSOCThe threshold value is 5% -15%.
7. A battery pack charge-discharge protection device, comprising:
the acquisition and calculation module is used for acquiring voltage difference at each moment in the charging or discharging process of the battery pack and calculating a corresponding charging threshold or discharging threshold according to the voltage difference, wherein the voltage difference is the difference between the highest voltage and the lowest voltage of all the battery cells in the battery pack;
the monitoring and judging module is used for monitoring that the battery pack is in a charging state andSOCwhen the value is in a first preset interval, judging whether the voltage difference is larger than the charging threshold value or not; and upon detecting that the battery pack is in a discharge state andSOCwhen the value is in a second preset interval, judging whether the voltage difference is larger than the discharge threshold value or not;
and the charge-discharge protection module is used for carrying out overcharge protection on the battery pack when the monitoring and judging module judges that the voltage differential is larger than the charge threshold value, and carrying out overdischarge protection on the battery pack when the monitoring and judging module judges that the voltage differential is larger than the discharge threshold value.
8. The battery pack charge-discharge protection device according to claim 7, wherein the acquisition and calculation module is configured to acquire a voltage differential at each moment in a charging or discharging process of the battery pack; for the battery packSOCDiscretizing the values to form the battery packSOCDividing a value into a plurality ofSOCA level interval; acquired at each ofSOCAn extremum of the voltage differential of the battery pack within the class interval; according to eachSOCThe extreme value of the voltage difference of the battery pack in the level interval is calculated in the charging or discharging process of the battery packSOCAn average value of the extreme values of the voltage differences with values within a third preset interval; and calculating a corresponding charging threshold or discharging threshold according to the average value.
9. The battery pack charge-discharge protection device according to claim 8, wherein each ofSOCThe extreme value of the voltage difference of the battery pack in the level interval is respectivelySOCMaximum value or each of the voltage differences of the battery packs in the level intervalsSOCAnd the minimum value of the voltage difference of the battery pack in the level interval.
10. A computer readable storage medium, wherein a computer program is stored in the computer readable storage medium, wherein the computer program is configured to be run by a processor to perform the battery pack charge-discharge protection method of any one of claims 1 to 6.
CN202311612656.4A 2023-11-29 2023-11-29 Battery pack charge and discharge protection method and device Active CN117318252B (en)

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