CN117538769A - Method and device for predicting peak power of battery - Google Patents

Method and device for predicting peak power of battery Download PDF

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Publication number
CN117538769A
CN117538769A CN202210923632.XA CN202210923632A CN117538769A CN 117538769 A CN117538769 A CN 117538769A CN 202210923632 A CN202210923632 A CN 202210923632A CN 117538769 A CN117538769 A CN 117538769A
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power
difference value
battery
voltage
execution step
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薛楠
曹文鹏
舒小农
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Shanghai Jusheng Technology Co Ltd
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Shanghai Jusheng Technology Co Ltd
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/385Arrangements for measuring battery or accumulator variables
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/367Software therefor, e.g. for battery testing using modelling or look-up tables

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  • General Physics & Mathematics (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

A method and apparatus for predicting peak power of a battery are disclosed. And determining the second power in the current execution step as peak power by respectively acquiring a first difference value corresponding to the first power and a second difference value corresponding to the second power according to the first power and the second power in the last execution step and responding to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold value. Therefore, the peak power can be obtained in an iterative mode, the accuracy of peak power prediction is improved, the risk of overcharge or overdischarge of the battery is reduced, and the service life of the battery is further prolonged.

Description

Method and device for predicting peak power of battery
Technical Field
The present invention relates to the field of battery technologies, and in particular, to a method and an apparatus for predicting peak power of a battery.
Background
Along with the shortage of global energy and the increasing severity of environmental pollution, the development of new energy automobiles is increasingly emphasized, and the state monitoring of the power battery serving as an energy carrier of the new energy automobiles is particularly important. And the BATTERY management system (BMS, BATTERY MANAGEMENT SYSTEM) is used for realizing charge and discharge management of the power BATTERY system to ensure safe and stable operation of the power BATTERY system by detecting the states of all the single batteries in the power BATTERY pack and performing corresponding control strategy adjustment on the power BATTERY system according to the states of the single batteries. The peak power of battery output and input directly influences the quick start, acceleration and emergency braking ability of the vehicle, and further influences the safety and reliability of the whole vehicle operation. Meanwhile, necessary information can be provided for the whole vehicle, and the battery operation condition is optimized so as to prolong the service life of the battery. Therefore, the battery peak power state is limited based on the BMS, and an important basis is provided for the whole vehicle to reasonably use the battery output power.
In the prior art, the peak power of a battery is generally obtained through the power test of an offline power battery. However, the accuracy of the peak power obtained in this manner is relatively low, which may lead to overcharging or overdischarging of the power battery, and thus to a reduction in the service life of the power battery.
Disclosure of Invention
Accordingly, an object of the embodiments of the present invention is to provide a method and an apparatus for predicting peak power of a battery, which can improve accuracy of peak power prediction, reduce risk of overcharge or overdischarge of the battery, and further improve service life of the battery.
In a first aspect, an embodiment of the present invention provides a method for predicting peak power of a battery, where the method includes:
determining a first power and a second power in the executing step, wherein the second power is larger than the first power;
respectively obtaining a first difference value corresponding to the first power and a second difference value corresponding to the second power, wherein the first difference value is a difference value between a terminal voltage charged for a preset time under the first power and a cut-off voltage of a battery, the second difference value is a difference value between the terminal voltage charged for the preset time under the second power and the cut-off voltage of the battery, and the cut-off voltage is the highest working voltage or the lowest working voltage of the battery;
Determining the second power in the executing step as the peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold;
wherein, the determining the first power and the second power in the executing step includes:
determining the second power in the last execution step as the first power in the current execution step; and
and determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step.
In some embodiments, the determining the first power and the second power in the performing step further includes:
and determining initial first power and second power as the first power and the second power in the current execution step in response to the current execution step being the first execution step, wherein the initial first power and the initial second power are preset.
In some embodiments, the determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step includes:
determining a change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step; and
And determining the second power in the current execution step according to the change rate, the second difference value in the last execution step and the second power in the last execution step.
In some embodiments, the determining the change rate according to the first power, the second power, the first difference value, and the second difference value in the last performing step is specifically:
determining the change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step through a change rate calculation formula;
the change rate calculation formula is an approximate derivative of a root equation, the root equation is used for representing that the terminal voltage of the battery after the battery is continuously charged for a preset time under constant power is the cut-off voltage of the battery, and the approximate derivative is a ratio of the difference value of the first difference value and the second difference value to the difference value of the first power and the second power.
In some embodiments, the obtaining the first difference value corresponding to the first power and the second difference value corresponding to the second power respectively includes:
selecting one of the first power and the second power to be determined as a target power;
acquiring initial parameters of the circuit through off-line identification, wherein the initial parameters comprise at least one of open-circuit voltage, initial ohmic internal resistance and polarization parameters;
Acquiring an estimated value of the ohmic internal resistance of each period according to the initial parameters;
acquiring a target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power and the initial parameter; and
and acquiring a voltage difference value according to the target terminal voltage and the cut-off voltage, wherein the voltage difference value is the first difference value or the second difference value.
In some embodiments, the obtaining the estimated value of the ohmic internal resistance of each period according to the initial parameter includes:
in a first period, determining the initial ohmic internal resistance as an estimated value of the ohmic internal resistance; and
after the first period, estimating and obtaining the estimated value of the ohmic internal resistance of each period through a recursive least square method with forgetting factors.
In some embodiments, the obtaining the target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power and the initial parameter includes:
obtaining the terminal voltage of each period through a terminal voltage calculation formula;
and determining the terminal voltage of the last period as the target terminal voltage.
In some embodiments, the terminal voltage calculation formula is a relationship between the terminal voltage of the current period and an estimated value of ohmic internal resistance of the current period, the terminal voltage of the previous period and an initial parameter.
In a second aspect, an embodiment of the present invention provides a device for predicting peak power of a battery, where the device includes:
the power acquisition unit is used for determining first power and second power in the execution step, wherein the second power is larger than the first power;
the difference value obtaining unit is used for obtaining a first difference value corresponding to the first power and a second difference value corresponding to the second power respectively, wherein the first difference value is a difference value between a terminal voltage after being charged for a preset time period under the first power and a cut-off voltage of the battery, the second difference value is a difference value between the terminal voltage after being charged for a preset time period under the second power and the cut-off voltage of the battery, and the cut-off voltage is the highest working voltage or the lowest working voltage of the battery;
a peak power determining unit, configured to determine the second power in the executing step as the peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a predetermined threshold;
wherein the power acquisition unit includes:
a first power determining subunit, configured to determine the second power in the last execution step as the first power in the current execution step; and
And the second power determination subunit is used for determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step.
In a third aspect, an embodiment of the present invention provides an electronic device, including a memory and a processor, the memory storing one or more computer program instructions, wherein the one or more computer program instructions are executed by the processor to implement the method as described in the first aspect.
In a fourth aspect, embodiments of the present invention provide a computer readable storage medium having stored thereon computer program instructions which, when executed by a processor, implement a method according to the first aspect.
According to the technical scheme, the first power and the second power in the current execution step are determined according to the first power and the second power in the last execution step, the first difference value corresponding to the first power and the second difference value corresponding to the second power are respectively obtained, and the second power in the current execution step is determined to be the peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold. Therefore, the peak power can be obtained in an iterative mode, the accuracy of peak power prediction is improved, the risk of overcharge or overdischarge of the battery is reduced, and the service life of the battery is further prolonged.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a battery application system according to an embodiment of the present invention;
fig. 2 is an equivalent circuit diagram of a battery according to an embodiment of the present invention;
FIG. 3 is a flow chart of a method of predicting peak battery power in accordance with one embodiment of the present invention;
FIG. 4 is a flow chart of acquiring a first difference or a second difference according to an embodiment of the present invention;
FIG. 5 is a flow chart of a method of predicting peak battery power in accordance with another embodiment of the present invention;
FIG. 6 is a schematic diagram of a battery peak power prediction apparatus according to an embodiment of the present invention;
fig. 7 is a schematic diagram of an electronic device according to an embodiment of the invention.
Detailed Description
The present invention is described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in detail. The present invention will be fully understood by those skilled in the art without the details described herein. Well-known methods, procedures, flows, components and circuits have not been described in detail so as not to obscure the nature of the invention.
Moreover, those of ordinary skill in the art will appreciate that the drawings are provided herein for illustrative purposes and that the drawings are not necessarily drawn to scale.
Meanwhile, it should be understood that in the following description, "circuit" refers to a conductive loop constituted by at least one element or sub-circuit through electrical connection or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or being "connected between" two nodes, it can be directly coupled or connected to the other element or intervening elements may be present and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it means that there are no intervening elements present between the two.
Unless the context clearly requires otherwise, the words "comprise," "comprising," and the like in the description are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, it is the meaning of "including but not limited to".
In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, in the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
Fig. 1 is a schematic diagram of a battery application system according to an embodiment of the present invention. In the embodiment shown in fig. 1, the BATTERY application system includes a BATTERY 1, a BMS (BATTERY management system) 2, a powered device 3, and a charger 4. Wherein,
in the present embodiment, the battery 1 is a power battery of a vehicle for supplying power to an electrical consumer 4 in the vehicle. The electric equipment 4 can be an automobile air conditioner, a motor and other equipment.
The charger 4 is used for charging the battery 1.
The BMS realizes charge and discharge management of the power battery system to ensure safe and stable operation of the power battery system by detecting the states of all the single batteries in the power battery pack and adjusting the corresponding control strategy of the power battery system according to the states.
Specifically, fig. 2 is an equivalent circuit diagram of a battery according to an embodiment of the present invention. In the embodiment shown in FIG. 2In the description, a second-order RC (resistance, capacitance) equivalent circuit model of the battery is taken as an example, and the equivalent circuit of the battery comprises a power supply and an ohmic internal resistance R 0 Internal resistance of polarization R D1 And R is D2 Polarization capacitor C D1 And C D2 . Wherein, polarization internal resistance and polarization capacitance are used for simulating battery dynamic characteristics.
Assuming that the charging current is positive and the discharging current is negative, the terminal voltage formula is:
U k =OCV+i k *R 0 +U D1,k +U D2,k
Wherein U is k For the terminal voltage of the battery at the k moment, OCV is open circuit voltage, U D1,k For the internal resistance of polarization R D1 Polarization voltage at time k, U D2,k For the internal resistance of polarization R D2 Polarization voltage at time k, i k For the current at time k, R 0 Is ohmic in resistance.
Further U D1,k The calculation formula of (2) is as follows:
wherein U is D1,k-1 For the internal resistance of polarization R D1 The polarization voltage at time k-1, deltaT represents the time period from time k-1 to time k, i k Is the current at time k.
Similarly, U D2,k The calculation formula of (2) is as follows:
wherein U is D2,k For the internal resistance of polarization R D2 Polarization voltage at time k, U D2,k-1 For the internal resistance of polarization R D2 The polarization voltage at time k-1, deltaT represents the time period from time k-1 to time k, i k Is the current at the present moment.
It should be noted that, the embodiment of the present invention does not limit the k time and the k-1 time, and the k time and the k-1 time may be the batteryAt any time during operation, the time k is after the time k-1, and accordingly, Δt may be any time length. However, when the terminal voltage U is calculated periodically k Polarization voltage U D1,k And U D2,k The k-time is understood as the k-th period, and the k-1 time is understood as the k-1-th period, and Δt is the period, respectively. Wherein k is a positive integer of 1 or more.
The equivalent circuit model of the battery has better applicability to the working state of the power battery, a state equation of the model can be deduced, the model parameter identification is easy to realize and convenient to analyze and apply, and the model parameter identification is widely applied to new energy automobile modeling simulation research and BMS algorithm development based on the model, so that a typical second-order RC equivalent circuit model is selected to represent the external characteristics of the power battery.
Further, based on the second-order equivalent circuit model of the battery, the embodiment of the invention provides a method for predicting the peak power of the battery, which is shown in fig. 3 specifically, and comprises the following steps:
and S110, constructing a root equation.
In this embodiment, the root equation is used to characterize the terminal voltage of the battery after the battery is continuously charged/discharged for a predetermined time at a constant power as the cut-off voltage of the battery.
Further, the voltage of the battery after being continuously discharged for delta t seconds at constant power drops to the minimum allowable operating voltage V of the battery min Then the constant power value is the peak discharge power of the battery at seconds. Thus, when the battery is discharged, the root equation is:
F D (P D )=f V (-P D )| t+Δt -V min =0
wherein f V (-P D )| t+Δt As a function of terminal voltage with respect to power, i.e. the battery is discharged from time t at power P D Terminal voltage after sustained discharge Δt time, V min At the lowest operating voltage, F D (P D ) Representing the power P of the battery D The difference between the terminal voltage and the lowest operating voltage after the sustained discharge Δt time.
Further, the voltage of the rear end of the battery which is continuously charged for delta t seconds under constant power just reaches the highest working voltage V allowed by the battery max Then the constant power value is the peak charge power of battery Δt seconds. Thus, when the battery is charged, the root equation is:
F D (P D )=f V (P D )| t+Δt -V max =0
wherein f V (P D )| t+Δt As a function of terminal voltage with respect to power, i.e. the battery is charged from time t at power P D Terminal voltage after charging for Δt time, V max At the highest operating voltage, F D (P D ) Representing the power P of the battery D The difference between the terminal voltage and the highest voltage after the charging Δt time is continued.
And step S120, determining a change rate calculation formula according to the root equation.
In this embodiment, the change rate calculation formula is an approximate derivative of a root equation, where the root equation is used to characterize that a terminal voltage of the battery after the battery is continuously charged for a predetermined time under a constant power is a cut-off voltage of the battery, and the approximate derivative is a ratio of a difference value between the first difference value and the second difference value to a difference value between the first power and the second power.
Further, determining an approximate derivative of the root equation is approximating the average rate of change as a function derivative by a chord cut to obtain the approximate derivative. The chord cut method is a linear approximation method for solving the approximation root of a nonlinear equation, and an approximation solution of the equation is solved by taking the abscissa of the intersection of a chord corresponding to a curve arc and an x-axis as an approximation value of the abscissa of the intersection of the curve arc and the x-axis. The principle is that straight substitution of curve is used, that is, chord (straight line) is used to replace curve to calculate the approximate solution of equation, that is, the corresponding intersection abscissa of chord and x-axis is used as the approximate value of intersection abscissa of curve arc and x-axis.
Specifically, the change rate calculation formula is:
wherein P is D1 For the first power, P D2 For a second power, F D (P D1 ) As a first difference, F D (P D2 ) Is the second difference value F D ′(P D ) Is the rate of change.
Step S130, determining the first power and the second power in the current execution step.
In this embodiment, the estimation of the peak power of the battery is performed iteratively, and, as described above, the change rate calculation formula needs to use the first power and the second power, and thus, in each execution step, the first power and the second power in the execution step need to be determined, where the second power is greater than the first power.
Further, in the first execution step, the initial first power and the initial second power are determined as the first power and the second power in the current execution step, wherein the initial first power and the initial second power are preset.
Specifically, the initial first power and the second power may be set according to actual situations. For example, when calculating the peak power of the battery discharge, the range of the peak power of the battery at the time of discharge in the normal case is acquired, and the first power and the second power are determined within the range of the peak power. Similarly, when calculating the peak power of battery charging, the range of the peak power of the battery during charging is obtained, and the first power and the second power are determined within the range of the peak power.
In the second and subsequent execution steps, determining a change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step, and determining the second power in the current execution step according to the change rate, the second difference value in the last execution step and the second power in the last execution step.
Specifically, the second power in the last execution step is determined as the first power in the present execution step. The first power in the executing step is as follows:
P D1,n =P D2,n-1
Wherein P is D2,n-1 For the second power, P in the n-1 th execution step D1,n The first power in the nth execution step.
And determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step. The calculation formula of the second power in the executing step is as follows:
wherein P is D1,n-1 For the first power, P in the n-1 th execution step D2,n-1 For the second power in the n-1 th execution step, F D (P D1,n-1 ) For the first difference in n-1 execution steps, F D (P D2,n-1 ) For the second difference in n-1 execution steps, P D2,n The second power in the nth execution step.
Wherein,the reciprocal of the above rate of change.
It should be noted that the first power and the second power selected in each execution step are the same type of power. That is, during battery charging, both the first power and the second power are peak power of battery charging, and during battery discharging, both the first power and the second power are peak power of battery discharging.
Step S140, respectively obtaining a first difference value corresponding to the first power and a second difference value corresponding to the second power.
In this embodiment, a first difference value corresponding to the first power and a second difference value corresponding to the second power are obtained respectively. The first difference value is a difference value between a terminal voltage charged for a predetermined time under the first power and a cut-off voltage of the battery, the second difference value is a difference value between the terminal voltage charged for the predetermined time under the second power and the cut-off voltage of the battery, and the cut-off voltage is the highest working voltage or the lowest working voltage of the battery.
Further, fig. 4 is a flowchart of acquiring the first difference or the second difference according to an embodiment of the present invention. In the embodiment shown in fig. 4, the obtaining the first difference or the second difference includes the steps of:
step S141, selecting one of the first power and the second power to determine as the target power.
In the present embodiment, since it is necessary to calculate the first difference value corresponding to the first power and the second difference value corresponding to the second power, respectively, one of the first power and the second power is selected to be determined as the target power.
Further, when the first difference is calculated, the first power is selected as the target power. When the second difference is calculated, the second power is selected as the target power.
Step S142, obtaining initial parameters of the circuit through off-line identification, wherein the initial parameters comprise at least one of open circuit voltage, initial ohmic internal resistance and polarization parameters.
In the present embodiment, the initial parameters of the circuit including the open circuit voltage OCV, the initial ohmic internal resistance R are obtained by the off-line identification of the HPPC (hybrid pulse power characteristic, hybrid pulse power characteristic test) 0 And at least one of polarization parameters. Wherein the polarization parameter comprises polarization internal resistance R D1 And R is D2 Polarization capacitor C D1 And C D2
Furthermore, the HPPC uses a periodic pulse to discharge, charge and stand the battery, which is equivalent to connecting a variable load to the output end of the network, and can realize the working condition of constant current charge and discharge and record the change curve of the end voltage along with time. When the current in the circuit changes, the existence of the capacitor or the inductor is judged through the terminal voltage curve.
And step S143, acquiring estimated values of ohmic internal resistance of each period according to the initial parameters.
In this embodiment, in the first period, the initial ohmic internal resistance is determined as an estimated value of the ohmic internal resistance. After the first period, estimating and obtaining the estimated value of the ohmic internal resistance of each period through a recursive least square method with forgetting factors.
Further, according to the initial parameters, the estimated value of the ohmic internal resistance of each period is obtained through identification by a recursive least square algorithm of forgetting factors, wherein the calculation formula of the estimated value of the ohmic internal resistance is as follows:
R 0 (t)=R 0 (t-T)+K k [y(t)-I(t)R 0 (t-T)]
wherein T is the estimated period, R 0 (t) is the estimated value of the ohmic internal resistance of the current period, R 0 (T-T) is the estimated value of the ohmic internal resistance of the previous period, y (T) is the voltage of the ohmic internal resistance of the current period, I (T) is the current obtained by sampling, K k Is the algorithm gain.
Wherein the estimation period T is preset.
Further, the voltage y (t) of the ohmic internal resistance of the current period is obtained by calculation by the following formula:
y(t)=U t -OCV(t)-U D
wherein U is t To obtain the terminal voltage by sampling, OCV (t) is the open circuit voltage of the current period, U D For polarization voltage U D1 And U D2 And (3) summing.
K k The calculation formula of (2) is as follows:
wherein lambda is forgetting factor, Q k-1 The error covariance representing the ohmic internal resistance of the previous cycle, I (t), is the current obtained by sampling.
Further, the calculation formula of the error covariance is as follows:
wherein Q is k Represents the error covariance of the kth period, Q k-1 Representing the error covariance of the k-1 th period, I (t) is the current obtained by sampling, and λ is the forgetting factor.
It should be appreciated that the above-described forgetting factor λ and the error covariance value of the ohmic internal resistance of the first period may be set in advance.
Since the peak power time is the instantaneous power calculation SOC (State-of-Charge) and the temperature change is small, it can be approximately considered that the equivalent circuit model parameters do not change. That is, parameters such as the sampling current I (t) and the open circuit voltage OCV are the same in each period.
Therefore, considering the influence of battery aging on peak power estimation, the accuracy of the peak power estimation of the battery can be improved by updating the internal resistance of the battery in real time by using a recursive least square method with forgetting factors.
And step S144, obtaining a target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power and the initial parameter.
In this embodiment, the terminal voltage of each period is obtained according to the estimated value of the ohmic internal resistance, the target power and the initial parameter by using a terminal voltage calculation formula, and the terminal voltage of the last period is taken as the target terminal voltage.
As described above, the end voltage calculation formula of the equivalent circuit in fig. 2 is:
U k =OCV+i k *R 0 +U D1,k +U D2,k
wherein U is k For the terminal voltage of the battery at the k moment, OCV is open circuit voltage, U D1,k For the internal resistance of polarization R D1 Polarization voltage at time k, U D2,k For the internal resistance of polarization R D2 Polarization voltage at time k, i k For the current at time k, R 0 Is ohmic in resistance.
In the first period, the terminal voltage of the first period is the battery terminal voltage acquired in real time at the current moment, and can be according to the aboveThe real-time polarization voltage U at the current moment is calculated by the polarization voltage formula D1 (t) and U D2 (t) as a polarization voltage of the first period.
Meanwhile, according to the above formula, the calculation formula of the terminal voltage can be further expressed as:
wherein P represents a target power, f V,k (P) represents the terminal voltage of the kth period at the target power P, f V,k-1 (P) represents the terminal voltage of the (k-1) th period at the target power P, OCV (t) represents the open-circuit voltage, R 0 (t) represents an estimated value of ohmic internal resistance, R D1 And R is D2 Representing polarization resistance, C D1 And C D2 Representing the polarization capacitance, T being the period, U D1,k-1 Polarization capacitor C representing the k-1 th period D1 Voltage of U D2,k-1 Polarization capacitor C representing the k-1 th period D2 Is set in the above-described voltage range.
The terminal voltage calculation formula is the relation between the terminal voltage of the current period and the estimated value of the ohmic internal resistance of the current period, the terminal voltage of the previous period and the initial parameter.
The open circuit voltage is obtained by looking up a table according to the current time SOC.
And calculating the terminal voltage of each period through the formula in the second period and the periods after the second period, and taking the terminal voltage of the last period as the target terminal voltage.
Step S145, obtaining a voltage difference according to the target terminal voltage and the cut-off voltage, where the voltage difference is the first difference or the second difference.
In this embodiment, in combination with the step S101, when the battery is discharged, the calculation formula of the first difference is:
F D (P D1 )=f V (-P D1 )| t+Δt -V min
wherein f V (-P D1 )| t+Δt For terminal voltage, i.e. the battery is discharged from time t, at power P D1 Terminal voltage after sustained discharge Δt time, V min At the lowest operating voltage, F D (P D1 ) Representing a first difference.
When the battery is charged, the calculation formula of the first difference value is as follows:
F D (P D1 )=f V (P D1 )| t+Δt -V max
wherein f V (P D1 )| t+Δt For terminal voltage, i.e. the battery is discharged from time t, at power P D1 Terminal voltage after charging for Δt time, V max At the highest operating voltage, F D (P D1 ) Representing a first difference.
Similarly, when the battery is discharged, the calculation formula of the second difference is as follows:
F D (P D2 )=f V (-P D2 )| t+Δt -V min
wherein f V (-P D2 )| t+Δt For terminal voltage, i.e. the battery is discharged from time t, at power P D2 Terminal voltage after sustained discharge Δt time, V min At the lowest operating voltage, F D (P D2 ) Representing a second difference.
When the battery is charged, the calculation formula of the second difference value is as follows:
F D (P D2 )=f V (P D2 )| t+Δt -V max
wherein f V (P D2 )| t+Δt For terminal voltage, i.e. battery charging from time t, at power P D2 Terminal voltage after charging for Δt time, V max At the highest operating voltage, F D (P D2 ) Representing a second difference.
Thus, by setting the target power to the first power, a first difference can be obtained, and setting the target power to the second power, a second difference can be obtained.
It should be noted that, the minimum operating voltage and the maximum operating voltage are used for calculating the first difference and the second difference in the charging and discharging processes, and the minimum operating voltage and the maximum operating voltage in the charging and discharging processes may be the same or different.
Step S150, judging whether the absolute value of the second difference value is smaller than a preset threshold value.
In this embodiment, a predetermined threshold epsilon is preset, and after the second difference is obtained, it is determined whether the absolute value of the second difference is smaller than the predetermined threshold epsilon. That is, judgment:
|F D (P D2 )|<ε
in response to the second difference value being smaller than the predetermined threshold value, step S160 is entered.
In response to the second difference being greater than or equal to the predetermined threshold, returning to step S130, proceeding to the next execution step.
And step S160, determining the second power in the current execution step as the peak power.
In this embodiment, the second power in the current execution step is determined as the peak power in response to the second difference being less than a predetermined threshold.
Thus, the peak power can be obtained.
For example, assuming that the current time is t, during charging or discharging, the peak power from the current time t to Δt time needs to be determined. Firstly, acquiring parameters I (t) and polarization resistance R by sampling or off-line identification D1 And R is D2 Polarization capacitor C D1 And C D2 Parameters such as initial ohmic internal resistance. Next, the Δt time period may be divided into M periods according to a preset period T. In each execution step, initial first power and second power are set, estimated values of ohmic internal resistance of each period pass in an iterative manner according to M periods divided in advance, terminal voltages of each period are calculated until the terminal voltage of the Mth period is acquired, the terminal voltage of the Mth period is determined as the terminal voltage in the execution step, and a first difference value and a second difference value are calculated according to the terminal voltages in the execution step. If the absolute value of the second difference is smaller than The second power in the performing step is determined as the peak power by a predetermined threshold. If the absolute value of the second difference is not less than the predetermined threshold, the first power and the second power in the next execution step are determined based on the first power and the second power in the execution step, and then the next execution step is executed until the absolute value of the second difference is less than the predetermined threshold.
It should be noted that, in the embodiment of the present invention, the "executing step" and the "period" are not the same concept, where the "period" is used to calculate the terminal voltage in each executing step, that is, the terminal voltage needs to be calculated by the period in each executing step. The basic idea is to approximate the objective function by using the first derivative (gradient) at the iteration point through the taylor formula, then take the minimum point of the quadratic model as the new iteration point, and repeat the process until the approximate minimum value meeting the precision is obtained. In the root-finding iteration process, the iteration direction of each step of the derivative algorithm is along the gradient descending direction of the current point function value, so that the convergence speed of the Newton method is high, and the optimal value can be highly approximated.
The embodiment of the invention determines the first power and the second power in the current execution step according to the first power and the second power in the last execution step, respectively obtains a first difference value corresponding to the first power and a second difference value corresponding to the second power, and determines the second power in the current execution step as peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold. Therefore, the peak power can be obtained in an iterative mode, the accuracy of peak power prediction is improved, the risk of overcharge or overdischarge of the battery is reduced, and the service life of the battery is further prolonged.
Fig. 5 is a flowchart of a method of predicting peak battery power according to another embodiment of the present invention. In the embodiment shown in fig. 5, the method for predicting the peak power of the battery includes the steps of:
step S210, determining a first power and a second power in the executing step, wherein the second power is larger than the first power.
Step S220, respectively obtaining a first difference value corresponding to the first power and a second difference value corresponding to the second power, where the first difference value is a difference value between a terminal voltage after charging for a predetermined period of time under the first power and a cut-off voltage of the battery, and the second difference value is a difference value between a terminal voltage after charging for a predetermined period of time under the second power and a cut-off voltage of the battery, and the cut-off voltage is a highest working voltage or a lowest working voltage of the battery.
And step S230, determining the second power in the executing step as the peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold.
Wherein, the determining the first power and the second power in the executing step includes:
determining the second power in the last execution step as the first power in the current execution step; and
and determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step.
In some embodiments, the determining the first power and the second power in the performing step further includes:
and determining initial first power and second power as the first power and the second power in the current execution step in response to the current execution step being the first execution step, wherein the initial first power and the initial second power are preset.
In some embodiments, determining the second power in the current execution step based on the first power, the second power, the first difference, and the second difference in the last execution step comprises:
determining a change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step; and
And determining the second power in the current execution step according to the change rate, the second difference value in the last execution step and the second power in the last execution step.
In some embodiments, the determining the change rate according to the first power, the second power, the first difference value, and the second difference value in the last performing step is specifically:
determining the change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step through a change rate calculation formula;
the change rate calculation formula is an approximate derivative of a root equation, the root equation is used for representing that the terminal voltage of the battery after the battery is continuously charged for a preset time under constant power is the cut-off voltage of the battery, and the approximate derivative is a ratio of the difference value of the first difference value and the second difference value to the difference value of the first power and the second power.
In some embodiments, the obtaining the first difference value corresponding to the first power and the second difference value corresponding to the second power respectively includes:
selecting one of the first power and the second power to be determined as a target power;
acquiring initial parameters of the circuit through off-line identification, wherein the initial parameters comprise at least one of open-circuit voltage, initial ohmic internal resistance and polarization parameters;
Acquiring an estimated value of the ohmic internal resistance of each period according to the initial parameters;
acquiring a target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power and the initial parameter; and
and acquiring a voltage difference value according to the target terminal voltage and the cut-off voltage, wherein the voltage difference value is the first difference value or the second difference value.
In some embodiments, the obtaining the estimated value of the ohmic internal resistance of each period according to the initial parameter includes:
in a first period, determining the initial ohmic internal resistance as an estimated value of the ohmic internal resistance; and
after the first period, estimating and obtaining the estimated value of the ohmic internal resistance of each period through a recursive least square method with forgetting factors.
In some embodiments, the obtaining the target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power and the initial parameter includes:
obtaining the terminal voltage of each period through a terminal voltage calculation formula;
and determining the terminal voltage of the last period as the target terminal voltage.
In some embodiments, the terminal voltage calculation formula is a relationship between the terminal voltage of the current period and an estimated value of ohmic internal resistance of the current period, the terminal voltage of the previous period and an initial parameter.
The embodiment of the invention determines the first power and the second power in the current execution step according to the first power and the second power in the last execution step, respectively obtains a first difference value corresponding to the first power and a second difference value corresponding to the second power, and determines the second power in the current execution step as peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold. Therefore, the peak power can be obtained in an iterative mode, the accuracy of peak power prediction is improved, the risk of overcharge or overdischarge of the battery is reduced, and the service life of the battery is further prolonged.
Fig. 6 is a schematic diagram of a device for predicting peak power of a battery according to an embodiment of the present invention. In the embodiment shown in fig. 6, the prediction apparatus of the battery peak power includes a power acquisition unit 61, a difference acquisition unit 62, and a peak power determination unit 63. The power obtaining unit 61 is configured to determine a first power and a second power in the executing step, where the second power is greater than the first power. The difference obtaining unit 62 is configured to obtain a first difference value corresponding to the first power and a second difference value corresponding to the second power, where the first difference value is a difference value between a terminal voltage after being charged for a predetermined period of time at the first power and a cutoff voltage of the battery, and the second difference value is a difference value between a terminal voltage after being charged for a predetermined period of time at the second power and a cutoff voltage of the battery, and the cutoff voltage is a highest operating voltage or a lowest operating voltage of the battery. The peak power determining unit 63 is configured to determine the second power in the executing step as the peak power in response to the absolute value of the second difference corresponding to the second power being smaller than a predetermined threshold.
Wherein the power acquisition unit includes:
a first power determining subunit, configured to determine the second power in the last execution step as the first power in the current execution step; and
and the second power determination subunit is used for determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step.
In some embodiments, the power harvesting unit comprises:
and the initial power determining subunit is used for determining initial first power and second power as the first power and the second power in the current execution step in response to the current execution step as the first execution step, wherein the initial first power and the initial second power are preset.
In some embodiments, the second power determination subunit comprises:
the change rate determining module is used for determining the change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step; and
and the second power determining module is used for determining the second power in the current execution step according to the change rate, the second difference value in the last execution step and the second power in the last execution step.
In some embodiments, the rate of change determination module is specifically configured to:
determining the change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step through a change rate calculation formula;
the change rate calculation formula is an approximate derivative of a root equation, the root equation is used for representing that the terminal voltage of the battery after the battery is continuously charged for a preset time under constant power is the cut-off voltage of the battery, and the approximate derivative is a ratio of the difference value of the first difference value and the second difference value to the difference value of the first power and the second power.
In some embodiments, the difference acquisition unit includes:
a target power determining subunit, configured to select one of the first power and the second power to determine as a target power;
an initial parameter obtaining subunit, configured to obtain an initial parameter of the circuit through offline identification, where the initial parameter includes at least one of an open circuit voltage, an initial ohmic internal resistance, and a polarization parameter;
an ohmic internal resistance estimation subunit, configured to obtain an estimated value of the ohmic internal resistance of each period according to the initial parameter;
a target terminal voltage obtaining subunit, configured to obtain a target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power and the initial parameter; and
The difference value obtaining subunit is configured to obtain a voltage difference value according to the target terminal voltage and the cut-off voltage, where the voltage difference value is the first difference value or the second difference value.
In some embodiments, the ohmic internal resistance estimation subunit comprises:
a first estimation module, configured to determine, in a first period, the initial ohmic internal resistance as an estimated value of the ohmic internal resistance; and
and the second estimation module is used for obtaining the estimated value of the ohmic internal resistance of each period through recursive least square estimation with forgetting factors after the first period.
In some embodiments, the target terminal voltage acquisition subunit comprises:
the terminal voltage calculation module is used for obtaining the terminal voltage of each period through a terminal voltage calculation formula;
and the target terminal voltage determining module is used for determining the terminal voltage of the last period as the target terminal voltage.
In some embodiments, the terminal voltage calculation formula is a relationship between the terminal voltage of the current period and an estimated value of ohmic internal resistance of the current period, the terminal voltage of the previous period and an initial parameter.
The embodiment of the invention determines the first power and the second power in the current execution step according to the first power and the second power in the last execution step, respectively obtains a first difference value corresponding to the first power and a second difference value corresponding to the second power, and determines the second power in the current execution step as peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold. Therefore, the peak power can be obtained in an iterative mode, the accuracy of peak power prediction is improved, the risk of overcharge or overdischarge of the battery is reduced, and the service life of the battery is further prolonged.
Fig. 7 is a schematic diagram of an electronic device according to an embodiment of the invention. The electronic device shown in fig. 7 is a general-purpose data processing apparatus comprising a general-purpose computer hardware structure including at least a processor 71 and a memory 72. The processor 71 and the memory 72 are connected by a bus 73. The memory 72 is adapted to store instructions or programs executable by the processor 71. The processor 71 may be a separate microprocessor or a collection of one or more microprocessors. Thus, the processor 71 performs the process flow of the embodiment of the present invention described above to realize the processing of data and the control of other devices by executing the instructions stored in the memory 72. Bus 73 connects the above components together, as well as to display controller 74 and display devices and input/output (I/O) devices 75. Input/output (I/O) devices 75 may be a mouse, keyboard, modem, network interface, touch input device, somatosensory input device, printer, and other devices known in the art. Typically, an input/output device 75 is connected to the system through an input/output (I/O) controller 76.
It will be apparent to those skilled in the art that embodiments of the present invention may be provided as a method, apparatus (device) or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may employ a computer program product embodied on one or more computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations of methods, apparatus (devices) and computer program products according to embodiments of the application. It will be understood that each of the flows in the flowchart may be implemented by computer program instructions.
These computer program instructions may be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows.
These computer program instructions may also be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, and various modifications and variations may 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.

Claims (11)

1. A method for predicting peak power of a battery, the method comprising:
determining a first power and a second power in the executing step, wherein the second power is larger than the first power;
respectively obtaining a first difference value corresponding to the first power and a second difference value corresponding to the second power, wherein the first difference value is a difference value between a terminal voltage charged for a preset time under the first power and a cut-off voltage of a battery, the second difference value is a difference value between the terminal voltage charged for the preset time under the second power and the cut-off voltage of the battery, and the cut-off voltage is the highest working voltage or the lowest working voltage of the battery;
determining the second power in the executing step as the peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a preset threshold;
wherein, the determining the first power and the second power in the executing step includes:
determining the second power in the last execution step as the first power in the current execution step; and
and determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step.
2. The method of claim 1, wherein determining the first power and the second power in the performing step further comprises:
and determining initial first power and second power as the first power and the second power in the current execution step in response to the current execution step being the first execution step, wherein the initial first power and the initial second power are preset.
3. The method of claim 1, wherein determining the second power in the current execution step based on the first power, the second power, the first difference, and the second difference in the last execution step comprises:
determining a change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step; and
and determining the second power in the current execution step according to the change rate, the second difference value in the last execution step and the second power in the last execution step.
4. A method according to claim 3, wherein the determining the rate of change from the first power, the second power, the first difference and the second difference in the last performing step is specifically:
determining the change rate according to the first power, the second power, the first difference value and the second difference value in the last execution step through a change rate calculation formula;
The change rate calculation formula is an approximate derivative of a root equation, the root equation is used for representing that the terminal voltage of the battery after the battery is continuously charged for a preset time under constant power is the cut-off voltage of the battery, and the approximate derivative is a ratio of the difference value of the first difference value and the second difference value to the difference value of the first power and the second power.
5. The method of claim 1, wherein the obtaining the first difference corresponding to the first power and the second difference corresponding to the second power, respectively, comprises:
selecting one of the first power and the second power to be determined as a target power;
acquiring initial parameters of the circuit through off-line identification, wherein the initial parameters comprise at least one of open-circuit voltage, initial ohmic internal resistance and polarization parameters;
acquiring an estimated value of the ohmic internal resistance of each period according to the initial parameters;
acquiring a target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power and the initial parameter; and
and acquiring a voltage difference value according to the target terminal voltage and the cut-off voltage, wherein the voltage difference value is the first difference value or the second difference value.
6. The method of claim 5, wherein the obtaining an estimate of the ohmic internal resistance for each cycle based on the initial parameter comprises:
In a first period, determining the initial ohmic internal resistance as an estimated value of the ohmic internal resistance; and
after the first period, estimating and obtaining the estimated value of the ohmic internal resistance of each period through a recursive least square method with forgetting factors.
7. The method of claim 5, wherein the obtaining the target terminal voltage corresponding to the target power according to the estimated value of the ohmic internal resistance, the target power, and the initial parameter comprises:
obtaining the terminal voltage of each period through a terminal voltage calculation formula;
and determining the terminal voltage of the last period as the target terminal voltage.
8. The method of claim 7, wherein the terminal voltage calculation formula is a relationship between the terminal voltage of the current period and an estimated value of the ohmic internal resistance of the current period, the terminal voltage of the previous period, and an initial parameter.
9. A battery peak power prediction apparatus, the apparatus comprising:
the power acquisition unit is used for determining first power and second power in the execution step, wherein the second power is larger than the first power;
the difference value obtaining unit is used for obtaining a first difference value corresponding to the first power and a second difference value corresponding to the second power respectively, wherein the first difference value is a difference value between a terminal voltage after being charged for a preset time period under the first power and a cut-off voltage of the battery, the second difference value is a difference value between the terminal voltage after being charged for a preset time period under the second power and the cut-off voltage of the battery, and the cut-off voltage is the highest working voltage or the lowest working voltage of the battery;
A peak power determining unit, configured to determine the second power in the executing step as the peak power in response to the absolute value of the second difference value corresponding to the second power being smaller than a predetermined threshold;
wherein the power acquisition unit includes:
a first power determining subunit, configured to determine the second power in the last execution step as the first power in the current execution step; and
and the second power determination subunit is used for determining the second power in the current execution step according to the first power, the second power, the first difference value and the second difference value in the last execution step.
10. An electronic device comprising a memory and a processor, wherein the memory is configured to store one or more computer program instructions, wherein the one or more computer program instructions are executed by the processor to implement the method of any of claims 1-8.
11. A computer readable storage medium, on which computer program instructions are stored, which computer program instructions, when executed by a processor, implement the method of any of claims 1-8.
CN202210923632.XA 2022-08-02 2022-08-02 Method and device for predicting peak power of battery Pending CN117538769A (en)

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