Disclosure of Invention
The invention aims to provide a method for dynamically estimating the electric quantity of a storage battery, a battery management system and an electric vehicle, which can obtain relatively accurate electric quantity of the battery.
In order to solve the technical problems, the invention is realized by the following technical scheme:
a method for dynamically evaluating the electric quantity of a storage battery is applied to an electric vehicle and comprises the following steps:
s01, obtaining an initial electric quantity value Q of the current period according to the battery state of the storage battery c0 A weight value K and a charge-discharge characteristic curve; the battery state at least comprises the current voltage value of the storage battery, the charge-discharge characteristic curve is a relation characteristic curve of an open-circuit voltage value and an electric quantity value of the storage battery in the charge-discharge process, and n correction points are arranged on the charge-discharge characteristic curve;
s02, calculating the electric quantity change value of the storage battery in the current period by adopting a coulomb method, correcting the electric quantity change value according to the weight value K, and combining the corrected electric quantity change value with an initial electric quantity value Q c0 Adding or subtracting to obtain the first electric quantity value Q of the pre-correction of the storage battery c1 ;
S03, when the current voltage value of the storage battery reaches an open circuit voltage value V corresponding to an ith correction point i In the time, according to the electric quantity value Q corresponding to the correction point i For the first electric quantity value Q c1 Re-correcting to obtain a second electric quantity value Q c2 And according to the re-corrected second electric quantity value Q c2 Calculating the battery electric quantity percentage of the storage battery in the current period; wherein 0 is<i≤n。
Further, the period duration of the current period is 100ms.
Further, the battery state further includes one or a combination of a current value and a temperature value, and the method for determining the weight value K in step S01 is as follows:
and obtaining a corresponding weight value K according to the voltage value, the current value or the temperature value in a table.
Further, when the storage battery is in a charged state, the weight value K comprises a charging temperature coefficient Ka, a charging charge storage coefficient Kb and a battery aging coefficient Kc; when the storage battery is in a discharging state, the weight value K comprises a discharging temperature coefficient Kd, a discharging charge activity coefficient Ke and a battery aging coefficient Kc.
Further, the charging temperature coefficient Ka and the discharging temperature coefficient Kd are obtained through table lookup; the charging charge storage coefficient Kb= (Qmax-Qmin)/Qt, the discharging charge active coefficient Ke= (Qmax-Qmin)/Qt, qt is the rated electric quantity of the storage battery, qmax is the electric quantity value corresponding to the maximum open circuit voltage value which can be reached by the full charge of the storage battery in the last charging period, and Qmin is the electric quantity value corresponding to the minimum open circuit voltage value which can be reached by the full discharge of the storage battery in the last discharging period; the battery aging coefficient is kc=qc/Qt, and Qc is the actual electric quantity of the storage battery in the current battery state.
Further, when the storage battery is in a charged state, the first electric quantity value Q is pre-corrected
c1 The calculation formula of (2) is as follows:
,
K=Ka+Kb+Kc,I in is a charging current;
when the storage battery is in a discharging state, the first electric quantity value Q is pre-corrected
c1 The calculation formula of (2) is as follows:
,K=Kd+Ke+Kc;
I out is the discharge current.
Further, the charge-discharge characteristic curve at step S01 is obtained by the following method:
obtaining a characteristic curve relation between an open-circuit voltage value and an electric quantity value of a storage battery in a charging state through experiments to form charging characteristic curves, marking n characteristic points on each charging characteristic curve as correction points, wherein each correction point has an electric quantity value and an open-circuit voltage value corresponding to the electric quantity value;
and obtaining the characteristic curve relation between the open-circuit voltage value and the electric quantity value of the storage battery in a discharging state through experiments to form discharging characteristic curves, marking n characteristic points on each discharging characteristic curve as correction points, wherein each correction point has an electric quantity value and an open-circuit voltage value corresponding to the electric quantity value.
Further, in step S03, in a state where the battery is charged, the current power of the battery is calculatedThe voltage reaches the open circuit voltage value V corresponding to the ith correction point i In the time, according to the electric quantity value Q corresponding to the correction point i For the first electric quantity value Q c1 Re-correcting to obtain a second electric quantity value Q c2 The method specifically comprises the following steps:
if the current battery voltage reaches the open circuit voltage value V corresponding to the ith correction point i In the course of time, according to the V on the charging characteristic curve i Corresponding electric quantity value SOC i And (3) carrying out re-correction, wherein the correction formula is as follows: q (Q) c2 =Q c1 +Ki(Q i -Q c1 ) Ki is a preset electric quantity correction coefficient.
Further, in step S03, when the battery is in a discharging state, the current voltage of the battery reaches the open circuit voltage value V corresponding to the i correction point i In the time, according to the electric quantity value Q corresponding to the correction point i For the first electric quantity value Q c1 Re-correcting to obtain a second electric quantity value Q c2 The method specifically comprises the following steps:
if the current voltage reaches the open circuit voltage value V corresponding to the ith correction point i In time, according to the V on the discharge characteristic curve i Corresponding electric quantity value Q i And (3) carrying out re-correction, wherein the correction formula is as follows: q (Q) c2 =Q c1 +Ki(Q c1 -Q i ) Ki is the electrical quantity correction coefficient.
The embodiment of the invention also provides a battery management system, which adopts the electric quantity dynamic estimation method and comprises a parameter acquisition module, a storage module and a calculation module:
the parameter acquisition module is used for acquiring an open-circuit voltage value, a current value and a temperature value of the storage battery;
the calculation module is used for calculating a first electric quantity value Q which is pre-corrected c1 And a re-corrected second electric quantity value Q c2 Calculating the battery power percentage in the current period;
the storage module is used for storing a first electric quantity value Q which is pre-corrected c1 And a re-corrected second electric quantity value Q c2 。
The embodiment of the invention also provides an electric vehicle, which comprises a storage battery and a battery management system, wherein the battery management system is the battery management system.
In summary, in the above embodiment, during the calculation of the electric quantity, the electric quantity is adjusted twice, and during the first pre-correction, the electric quantity value is adjusted by adding the weight value according to different environmental temperatures and the working states of the battery, so as to obtain the first electric quantity value; and in the second post correction, comparing the electric quantity value of the correction point selected in the charge-discharge characteristic curve with the first electric quantity value to obtain a difference value between the actual electric quantity of the battery and the first electric quantity value, and performing error correction by using a PI algorithm, so that the indication accuracy of the electric quantity is improved jointly through pre-correction and post correction.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order to facilitate understanding of the present invention, some terms related to the present invention will be described below:
(1) And the actual electric quantity is discharged from the full state of the battery, and when the voltage of the battery reaches the cut-off discharge voltage, the accumulated electric quantity represents the actual maximum electric quantity of the battery.
The real power is a variable power. Depending on the different ambient temperatures, different actual amounts of battery charge may occur. For example, a battery has a maximum discharge capacity of 15AH at zero ambient temperature, 18AH at 25 ambient temperature, and 20AH at 50 ambient temperature.
Of course, the actual power is also different in different discharge current conditions. For example, the accumulated discharge amount is 15A in the state of 1C discharge current, but 20A in the state of 0.1C discharge current. The change in the actual power is an actual parameter, which is an objective fact. The zero electric quantity of the real electric quantity is determined according to the discharge cut-off voltage of the battery, and when the voltage of the battery reaches the cut-off discharge voltage in the rated discharge current state, the real electric quantity of the battery is determined to be zero.
(2) The charging electric quantity refers to an accumulated electric quantity value when the battery reaches the maximum electric quantity in the charging process. The method is different from the actual electric quantity, the battery is in loss in the charging process, extra electric quantity loss is generated in the processes of heating in the battery charging process, separating and analyzing electrolyte, and the like, and the loss is accumulated into the charging electric quantity, but cannot be into the actual electric quantity. The ratio of the charged power to the actual power is the charging efficiency.
(3) And (3) synthesizing the discharge electric quantity, and discharging at different discharge rates at different times to obtain an electric quantity value. In the comprehensive discharging process, the real electric quantity is changed according to the real-time discharging rate, the temperature of the battery and other environmental factors. The integrated power is accumulated by different real power generated by different time phases and different discharge rates.
Referring to fig. 1, a first embodiment of the present invention provides a method for dynamically estimating the charge of a storage battery, which can be executed by a battery management system of the storage battery, and in particular, by a processor or a computing module in the battery management system, so as to implement the following steps:
s01 according toThe battery state of the storage battery obtains the initial electric quantity value Q of the current period c0 A weight value K and a charge-discharge characteristic curve; the battery state at least comprises the current voltage value of the storage battery, the charge-discharge characteristic curve is a relation characteristic curve of an open-circuit voltage value and an electric quantity value of the storage battery in the charge-discharge process, and n correction points are arranged on the charge-discharge characteristic curve.
In this embodiment, the battery may be a lead-acid battery. The battery management system can also comprise a parameter acquisition module, and the battery state of the storage battery during working can be acquired through the parameter acquisition module, for example, the current voltage value, the current value, the temperature value and the like of the storage battery can be acquired. The operating state may be a discharging state or a charging state.
In this embodiment, after the battery management system is powered on and initialized, an initial power value Q can be estimated according to the real-time no-load voltage of the battery and the rated capacity of the battery c0 Thereafter, an initial electric quantity value Q of each period c0 Are obtained according to the calculation result of the previous period. In this embodiment, the period duration of each period may be set to 100mS, and during this period, the output voltage and the current may be regarded as a stable value, and of course, the period duration may be selected according to actual needs, for example, 50mS,150mS,200mS, etc., which are all within the protection scope of the present invention.
In this embodiment, the weight K is mainly used to adjust the actual electric quantity value of the battery, and the weight K is obtained by analyzing the influences of different ambient temperatures and battery aging degrees on the charging characteristic curve of the battery.
Specifically, when the storage battery is in a charged state, the weight value K includes a charging temperature coefficient Ka, a charging charge storage coefficient Kb, and a battery aging coefficient Kc; when the storage battery is in a discharging state, the weight value K comprises a discharging temperature coefficient Kd, a discharging charge activity coefficient Ke and a battery aging coefficient Kc.
Wherein, the charging temperature coefficient Ka and the discharging temperature coefficient Kd are coefficients related to temperature values, and can be obtained through table lookup. The charging temperature coefficient Ka is mainly used for correcting the loss of the charging caused by the environment and the temperature of the battery. The discharge temperature coefficient Kd is mainly used to correct the environment and the loss of the battery temperature to discharge.
The charging charge storage coefficient Kb= (Qmax-Qmin)/Qt, the discharging charge active coefficient Ke= (Qmax-Qmin)/Qt, qt is the rated electric quantity of the storage battery, qmax is the electric quantity value corresponding to the maximum open circuit voltage value which can be reached by the full charge of the storage battery in the last charging period, and Qmin is the electric quantity value corresponding to the minimum open circuit voltage value which can be reached by the full discharge of the storage battery in the last discharging period; the battery aging coefficient is kc=qc/Qt.
The charging charge storage coefficient Kb is mainly used for correcting the charging current and the loss generated by the internal cause of the battery. The discharge charge activity coefficient Ke is mainly used for correcting the discharge current and the loss generated by the internal cause of the battery. The battery aging coefficient Kc is mainly used for correcting the loss caused by battery aging.
In the present embodiment, the charge-discharge characteristic curve is the basis for judging whether the battery operation performance is stable. When the accumulator is discharged, its working voltage always changes along with the time, and the working voltage value of the accumulator is used as ordinate, the discharging time, charging time, electric quantity or state of charge (SOC) or depth of discharge (DOD) is used as abscissa, and the drawn curve is called charge-discharge characteristic curve. In this embodiment, the charge-discharge characteristic curve is generated by taking the operating voltage value of the battery as the ordinate and the electric quantity of the battery as the abscissa.
In this embodiment, the charge-discharge characteristic curve is generated in advance by a charge-discharge experiment and stored in the memory. Since different temperatures and operating currents have different charge/discharge characteristics, it is necessary to generate a plurality of charge/discharge characteristics in advance.
Specifically, in some embodiments, a set of characteristics may be acquired every 5 degrees celsius between the minimum ambient temperature and the maximum ambient temperature at which the battery operates. Then, at each ambient temperature, a set of characteristic curves is acquired for each 0.1C increase of charging current in the range of 0.1C-0.5C. And collecting a set of characteristic curves when the discharge current is within the range of 0.1-1.5C and 0.2C is added, so that a series of charge-discharge characteristic curves can be generated. Of course, it should be understood that the temperature and the current of the interval may be set according to actual needs, and the present invention is not particularly limited.
In addition, the health of the battery also affects the charge-discharge characteristic, so in some embodiments, a set of charge-discharge characteristic may be collected for different battery health levels, such as 100%,75%,50%,25% of health, respectively.
In this embodiment, after the series of charge-discharge characteristic curves are generated, n calibration points are set in each charge-discharge characteristic curve, where the calibration points may be selected as characteristic points on the charge-discharge characteristic curve, and these characteristic points may reflect the battery power of the battery in this voltage and current output state. Where n is an integer greater than 1, which may be selected from 2,3,4,5, or other numbers, as desired.
In summary, in the present embodiment, the charge-discharge characteristic curve corresponding to the current battery state may be obtained by looking up a table according to the current operating state (whether to charge or discharge), the current value, the temperature value, or the health.
S02, calculating the electric quantity change value of the storage battery in the current period by adopting a coulomb method, correcting the electric quantity change value according to the weight value K, and combining the corrected electric quantity change value with an initial electric quantity value Q c0 Adding or subtracting to obtain the first electric quantity value Q of the pre-correction of the storage battery c1 。
In the present embodiment, specifically:
when the storage battery is in a charging state, a first electric quantity value Q is pre-corrected
c1 The calculation formula of (2) is as follows:
wherein,,K=Ka+Kb+Kc,I in is the charging current.
Here, it should be noted that, before charging, it is further required to determine whether the charging current or the charging voltage is greater than a preset current threshold, if so, there is an overcharge risk, and it is required to interrupt charging and issue an alarm in time.
When the storage battery is in a discharging state, the first electric quantity value Q is pre-corrected
c1 The calculation formula of (2) is as follows:
wherein,,K=Kd+Ke+Kc;I out is the discharge current.
S03, when the current voltage value of the storage battery reaches an open circuit voltage value V corresponding to an ith correction point i In the time, according to the electric quantity value Q corresponding to the correction point i For the first electric quantity value Q c1 Re-correcting to obtain a second electric quantity value Q c2 And according to the re-corrected second electric quantity value Q c2 Calculating the battery electric quantity percentage of the storage battery in the current period; wherein 0 is<i≤n。
In this embodiment, in order to obtain more accurate electric quantity, it is also necessary to perform secondary correction on the electric quantity in the working process.
Specifically, if the current battery voltage reaches the open circuit voltage value V corresponding to the ith correction point while the battery is in the charged state i In the course of time, according to the V on the charging characteristic curve i Corresponding electric quantity value SOC i For a first electric quantity value Q c1 Re-correcting to obtain a second electric quantity value Q c2 The correction formula is:
Q c2 =Q c1 +Ki(Q i -Q c1 ),
wherein Ki is a preset electric quantity correction coefficient.
In the discharging state of the accumulator, if the current voltage reaches the open-circuit voltage value V corresponding to the ith correction point i In time, according to the V on the discharge characteristic curve i Corresponding electric quantity value Q i And (3) carrying out re-correction, wherein the correction formula is as follows:
Q c2 =Q c1 +Ki(Q c1 -Q i )
wherein Ki is a preset electric quantity correction coefficient.
In the working process of the storage battery, the current voltage value of the storage battery is continuously changed along with the charging or discharging process, and the storage battery is characterized in that the voltage is gradually increased during charging, so that the voltage values corresponding to a plurality of correction points can be achieved. The voltage may gradually decrease during discharging, and may reach the voltage values corresponding to the plurality of correction points.
When the accumulator reaches the open-circuit voltage value V corresponding to the ith correction point i And comparing the electric quantity value of the correction point selected from the charge-discharge characteristic curve with the current first electric quantity value to obtain a difference value between the actual electric quantity of the battery and the first electric quantity value, and performing error correction by using a PI algorithm.
In the present embodiment, after the second electric quantity value Q after the secondary correction is obtained c2 Then dividing the current period by the real electric quantity Qa to obtain the battery electric quantity percentage of the storage battery in the current period.
In summary, in this embodiment, during the process of calculating the electric quantity, the electric quantity is adjusted twice, and during the first pre-correction, the weight value is added to adjust the electric quantity value according to different ambient temperatures and the working states of the battery, so as to obtain the first electric quantity value; and in the second post correction, comparing the electric quantity value of the correction point selected in the charge-discharge characteristic curve with the first electric quantity value to obtain a difference value between the actual electric quantity of the battery and the first electric quantity value, and performing error correction by using a PI algorithm, so that the indication accuracy of the electric quantity is improved jointly through pre-correction and post correction.
Referring to fig. 2, the second embodiment of the present invention further provides a battery management system, which adopts the above-mentioned method for dynamically estimating electric quantity, and includes a parameter acquisition module 210, a storage module 220 and a calculation module 230:
the parameter collection module 210 is configured to collect an open-circuit voltage value, a current value and a temperature value of the battery;
the calculation module 230 is used for calculating a first electric quantity value Q c1 And a re-corrected second electric quantity value Q c2 Calculating the battery power percentage in the current period;
the memory module 220 for storing a pre-corrected first electric quantity value Q c1 And a re-corrected second electric quantity value Q c2 。
The third embodiment of the invention also provides an electric vehicle, which comprises a storage battery and a battery management system, wherein the battery management system is the battery management system of any embodiment.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus and method may be implemented in other manners. The apparatus and method embodiments described above are merely illustrative, for example, flow diagrams and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition, functional modules in the embodiments of the present invention may be integrated together to form a single part, or each module may exist alone, or two or more modules may be integrated to form a single part.
The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, an electronic device, or a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes. It should be noted that, in this document, 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 one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be understood that the term "and/or" as used herein is merely one relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.
Depending on the context, the word "if" as used herein may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to detection". Similarly, the phrase "if determined" or "if detected (stated condition or event)" may be interpreted as "when determined" or "in response to determination" or "when detected (stated condition or event)" or "in response to detection (stated condition or event), depending on the context.
References to "first\second" in the embodiments are merely to distinguish similar objects and do not represent a particular ordering for the objects, it being understood that "first\second" may interchange a particular order or precedence where allowed. It is to be understood that the "first\second" distinguishing aspects may be interchanged where appropriate, such that the embodiments described herein may be implemented in sequences other than those illustrated or described herein.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.