Energy storage system charge-discharge power hierarchical control method based on lithium ion characteristics

Abstract

The application discloses a power layering control method for charging and discharging of an energy storage system based on lithium ion characteristics, and relates to the technical field of energy storage system control, and specifically discloses the following: the power control of the energy storage system is divided into a system monitoring layer, a state evaluation layer and a power regulation layer; the monitoring layer collects the charging and discharging power of each battery pack and stores the power in a database; a judgment module evaluates the state of the battery pack by analyzing the correlation coefficient of the power curve and calculating the power deviation PI, and judges whether the state of the battery pack needs to be evaluated; if the state needs to be evaluated, the state evaluation layer uses a support vector machine algorithm to construct a state evaluation model, outputs an aging degree value, and judges the linear correlation of the aging degree value in combination with the power deviation; if the aging degree value and the power deviation are linearly correlated, the power regulation layer enters the regulation, constructs a battery aging sequence, calculates the upper limit power of charging and discharging and regulates the charging and discharging power. The application also relates to a related control system, a computer device and a storage medium, and can effectively manage the power of the energy storage system and improve the performance and stability of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power control, in particular to a power layered control method for charging and discharging of energy storage system based on lithium ion characteristics. BACKGROUND

[0002] In the field of modern energy, energy storage systems play a crucial role in ensuring the stability and reliability of power systems. However, lithium-ion batteries have some problems during charging and discharging, which can adversely affect the overall performance and lifespan of the battery pack if not effectively managed.

[0003] Existing technologies do not monitor the charging and discharging power of the battery pack in a detailed and comprehensive manner, and lack systematic hierarchical management. For example, in the assessment of battery state, there is a lack of accurate and effective models and methods. Many existing technologies only rely on a single indicator or simple empirical formula to judge the battery health, making it difficult to comprehensively and accurately reflect the true aging degree and performance changes of the battery. For example, some methods only consider the capacity decay of the battery, ignoring the impact of internal resistance changes on the battery state, resulting in a large deviation in the evaluation results.

[0004] Existing technologies lack flexibility in power regulation. When the battery pack experiences power deviation changes, they cannot accurately regulate the power according to the actual aging degree and power deviation of the battery, and cannot effectively balance the use efficiency and lifespan extension of the battery pack. For example, some regulation strategies use fixed thresholds or simple rules, which cannot adapt to the diverse needs of different battery packs at different stages of use, easily causing overcharging, over-discharging, or excessive use of batteries, further accelerating battery aging, and reducing the overall performance and reliability of the energy storage system.

[0005] Therefore, the present application provides a power layered control method for charging and discharging of energy storage system based on lithium ion characteristics. SUMMARY

[0006] The present application aims to provide a power layered control method for charging and discharging of energy storage system based on lithium ion characteristics to solve at least one of the above-mentioned problems of existing technologies.

[0007] In a first aspect, the present application provides a power layered control method for charging and discharging of energy storage system based on lithium ion characteristics, comprising:

[0008] Based on the characteristics of lithium-ion energy storage systems, the power control of the energy storage system is divided into: system monitoring layer, state evaluation layer, and power regulation layer. Based on the system monitoring layer, the charging and discharging power of each battery pack in the energy storage system is obtained, and the collected charging and discharging power data is stored in the database.

[0009] The charging and discharging power of each battery pack is obtained from the database, and a curve analysis is drawn to obtain the correlation coefficient of the curve, the correlation coefficient of the charging and discharging power curve is numerically calculated to obtain a power deviation PI, and based on the power deviation PI, it is judged whether the state of the battery pack needs to be evaluated;

[0010] If the state of the battery pack needs to be evaluated, the energy storage system is in the state evaluation layer, the historical charging power and discharging power data of each battery pack in the energy storage system, and the dynamic internal resistance of each battery pack are obtained to establish a state evaluation model, and the aging degree value of each battery pack is output, combined with the power deviation value for fitting analysis to obtain a fitting approximation ratio, based on the fitting approximation ratio, it is judged whether the aging degree value-power deviation value presents a linear growth trend;

[0011] If the aging degree value-power deviation value presents a linear growth trend, the power control of the energy storage system enters the power regulation layer, the battery aging sequence is constructed based on the aging degree value, the charging and discharging power of the battery pack of the battery aging sequence is numerically analyzed to obtain the charging upper limit power and the discharging upper limit power, and the charging and discharging power of the battery pack is regulated based on the charging upper limit power and the discharging upper limit power using the energy storage converter.

[0012] In a second aspect, the present application provides a charging and discharging power layered control system of an energy storage system based on the characteristics of lithium ions, comprising: a data acquisition module: based on the characteristics of the lithium ion energy storage system, the power control of the energy storage system is divided into a system monitoring layer, a state evaluation layer, and a power regulation layer, based on the system monitoring layer, the charging and discharging power of each battery pack in the energy storage system is obtained, and the acquired charging and discharging power data is stored in the database;

[0013] An evaluation and judgment module: the charging and discharging power of each battery pack is obtained from the database, and a curve analysis is drawn to obtain the correlation coefficient of the curve, the correlation coefficient of the charging and discharging power curve is numerically calculated to obtain a power deviation PI, and based on the power deviation PI, it is judged whether the state of the battery pack needs to be evaluated;

[0014] An evaluation and analysis module: if the state of the battery pack needs to be evaluated, the energy storage system is in the state evaluation layer, the historical charging power and discharging power data of each battery pack in the energy storage system, and the dynamic internal resistance of each battery pack are obtained to establish a state evaluation model, and the aging degree value of each battery pack is output, combined with the power deviation value for fitting analysis to obtain a fitting approximation ratio, based on the fitting approximation ratio, it is judged whether the aging degree value-power deviation value presents a linear growth trend;

[0015] The power regulation module: if the aging degree value-power deviation value presents a linear growth trend, the power control of the energy storage system enters the power regulation layer, the battery aging sequence is constructed based on the aging degree value, the charging and discharging power of the battery pack of the battery aging sequence is analyzed, the charging upper limit power and the discharging upper limit power are obtained, and the charging and discharging power of the battery pack is regulated based on the charging upper limit power and the discharging upper limit power using the energy storage converter.

[0016] The beneficial effects of the present application are:

[0017] 1. The system monitoring layer accurately collects the charging and discharging power data of each battery pack, providing a rich and accurate information base for subsequent analysis. The state evaluation layer constructs a state evaluation model based on the support vector machine algorithm, combining historical charging and discharging power data and dynamic internal resistance multi-dimensional information, and more comprehensively evaluates the aging degree value of the battery pack.

[0018] 2. Through the power regulation layer, the battery packs with power deviation exceeding the threshold value in the battery aging sequence are regulated according to the relationship between the aging degree value and the power deviation value, the charging upper limit power and the discharging upper limit power are calculated, the power upper limit of the battery pack with larger aging degree is reduced, and the overall service life of the battery pack is prolonged as much as possible. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 is a flowchart of the power acquisition and judgment method provided by the first embodiment of the present application;

[0021] Figure 2 is a flowchart of state evaluation and function regulation provided by the second embodiment of the present application;

[0022] Figure 3 is a structural schematic diagram of the computer device apparatus provided by the fourth embodiment of the present application; DETAILED DESCRIPTION

[0023] In order to make the personnel in the technical field better understand the present application scheme, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0024] Embodiment one

[0025] Figure 1 The flowchart of the charge and discharge power acquisition method provided by Embodiment one of the present application can be applied to the power hierarchical control of the energy storage system. The energy storage system power control method can be executed by a lithium-ion characteristic-based energy storage system charge and discharge power hierarchical control system, which can be realized by software or hardware and can be configured in a computer device.

[0026] Step one, based on the characteristics of the lithium-ion energy storage system, the power control of the energy storage system is divided into three levels of system monitoring layer, state evaluation layer and power regulation layer. Based on the system monitoring layer, the charge and discharge power of each battery pack in the energy storage system is acquired, and the acquired charge and discharge power data is stored in the database.

[0027] Based on the characteristics of the lithium-ion energy storage system, the power control of the energy storage system is divided into multiple levels, including: system monitoring layer, state evaluation layer, and power regulation layer.

[0028] It should be noted that during the charging and discharging process of the lithium-ion battery, if the power and the target value change greatly, the overall performance and service life of the battery pack will be affected. By dividing the system monitoring layer, the state evaluation layer and the power regulation layer into multiple levels, the power of the energy storage battery is monitored, evaluated and regulated. The system monitoring layer is used to collect the power change of the energy storage system during charging and discharging. The state evaluation layer is used to evaluate the aging degree of each battery pack in the energy storage system. The power regulation layer is used to adjust the power during charging and discharging.

[0029] Based on the system monitoring layer, the fixed interval is adopted to acquire the charge and discharge power of each battery pack in the energy storage system, and the acquired charge and discharge power data is stored in the database.

[0030] In some embodiments, a multi-channel power quality analyzer is selected as a power meter. The power meter can collect the voltage and current values of multiple battery packs during charging and discharging, and the charge and discharge power can be obtained by multiplying the voltage and current.

[0031] For example, the power meter collects the charging power of battery pack 1 every 5 minutes. For example, the charging power at 8:00 is 101.13W, the charging power at 8:05 is 105.36W,..., the charging power at 8:45 is 0.81W, until the required power for fully charging the battery is reached, and the measurement of the charging power is stopped.

[0032] Step two, obtain the charging and discharging power of each battery pack from the database, draw the curve for analysis, get the correlation coefficient of the curve, calculate the correlation coefficient of the charging and discharging power curve, get the power deviation PI, based on the power deviation PI, judge whether the state of the battery pack needs to be evaluated;

[0033] In some embodiments, using a power meter, the charging and discharging power of the energy storage system is collected at fixed interval time, the charging power collected by the power meter is input into the MatLab software, and the time-charging power change curve and the time-discharging power change curve are drawn;

[0034] Using the correlation coefficient function of MatLab, the coincidence degree analysis of the time-charging power change curve and the charging target curve is carried out, and the correlation coefficient of the curve is obtained;

[0035] It should be noted that the correlation coefficient function of MatLab is used to judge the coincidence degree of the time-charging power change curve and the charging target curve, and the correlation coefficient function will return a correlation coefficient matrix, in which the elements on the diagonal line are the correlation coefficients of the two curves. The closer the correlation coefficient is to 1, the higher the coincidence degree is; the closer it is to 0, the lower the coincidence degree is;

[0036] The time-charging power change curve and the charging target curve have the same other interference factors, i.e. the same environmental temperature and grid input voltage, and the charging target curve is obtained by the professional technical personnel in the art according to the historical charging data of the energy storage device;

[0037] Divide the time-charging power change curve into multiple sub-sections, and obtain the correlation coefficient of each sub-section;

[0038] Compare the correlation coefficient with the correlation coefficient threshold value, if the correlation coefficient is higher than the correlation coefficient threshold value, mark the sub-section as a close section;

[0039] If the correlation coefficient in the sub-section in the time-charging power change curve is lower than the correlation coefficient threshold value, do not process;

[0040] Obtain the number of all close sections and the number of sub-sections, and process the number of close sections and the number of sub-sections by ratio, to obtain the close section ratio of the charging curve, and mark the close section ratio as Jq;

[0041] Process the correlation coefficient in the close section and the correlation coefficient threshold value by difference to obtain the correlation coefficient difference;

[0042] Process the correlation coefficient difference and the correlation coefficient threshold value by ratio to obtain the correlation close ratio;

[0043] Obtain all the access section related access ratios, sum all the access section related access ratios and take the average to obtain the average correlation ratio, mark the average correlation ratio as Xg;

[0044] Based on the access section ratio Jq and the average correlation ratio Xg, calculate the curve matching degree Pd of the time-discharge power change curve;

[0045] Obtain the curve matching degree Pd of the time-discharge power change curve through the formula: Pd=a*Jq+b*Xg, where a=0.213 and b=0.787;

[0046] Based on the curve matching degree calculation method of the time-charge power change curve, obtain the curve matching degree Pd of the time-discharge power change curve, and mark the curve matching degree of the time-discharge power change curve as Fd;

[0047] Based on the curve matching degree Pd of the time-discharge power change curve and the curve matching degree Fd of the time-discharge power change curve, calculate the power deviation value PI;

[0048] Through the formula: Obtain the power deviation value PI, where c=0.483 and d=0.517;

[0049] Compare the power deviation value PI with the power deviation threshold value to determine whether the state of the battery pack needs to be evaluated;

[0050] If the power deviation value PI is greater than or equal to the power deviation threshold value, it indicates that the time-charge power change curve and the time-discharge power change curve of the battery pack deviate greatly from the corresponding target curve, and the state of the battery pack needs to be evaluated;

[0051] If the power deviation value PI is less than the power deviation threshold value, it indicates that the time-charge power change curve and the time-discharge power change curve of the battery pack deviate within the expected range from the corresponding target curve, and the state of the battery pack does not need to be evaluated, but the change of the power deviation value PI still needs to be continuously monitored;

[0052] For example, the lithium ion energy storage system includes three battery packs, respectively marked as battery pack 1, battery pack 2 and battery pack 3. Taking the charging power of the battery pack 1 as an example, the charging power is collected every 5 minutes from 9:00 to 9:30, and the charging power data [100.51, 103.36, 105.72, 108.48, 110.23, 113.15, 116.09] is obtained, with the unit of watt (W). The input power curve is drawn by using the MatLab software, the close section ratio Jq is 0.50, the average correlation ratio Xg is 0.213, the curve matching degree Pd of the charging power is 0.269, the curve matching degree Fd of the discharging power is 0.201, the power deviation PI is 0.945, the power deviation threshold is 0.8, and the power deviation PI of the battery pack 1 is higher than the power deviation threshold, so the state of the battery pack 1 needs to be evaluated.

[0053] The technical scheme of the embodiment is as follows: based on the characteristics of the lithium ion energy storage system, the power control of the energy storage system is divided into a system monitoring layer, a state evaluation layer and a power regulation layer, the charging and discharging power of each battery pack in the energy storage system is obtained, the collected charging and discharging power data is stored in a database, the charging and discharging power of each battery pack is obtained from the database, a curve analysis is performed, the correlation coefficient of the curve is obtained, the correlation coefficient of the charging and discharging power curve is numerically calculated, the power deviation PI is obtained, and based on the power deviation PI, it is determined whether the state of the battery pack needs to be evaluated.

[0054] Embodiment two

[0055] Based on the embodiment one, the energy storage system charging and discharging power hierarchical control method based on the characteristics of the lithium ion is further provided with the following steps.

[0056] Step three, if the state of the battery pack needs to be evaluated, the energy storage system is in the state evaluation layer, the historical charging and discharging power data of each battery pack in the energy storage system and the dynamic internal resistance of each battery pack are obtained, a state evaluation model is established, and the aging degree value of each battery pack is output. The fitting analysis is performed in combination with the power deviation, the fitting close ratio is obtained, and it is determined whether the aging degree value-power deviation presents a linear growth trend based on the fitting close ratio.

[0057] The energy storage system is in the state evaluation layer, the historical charging and discharging power data of each battery pack in the energy storage system and the dynamic internal resistance of each battery pack are obtained.

[0058] The specific internal resistance acquisition method of the battery pack is as follows:

[0059] Based on the voltage value and the current value collected by the power meter, the Ohm's law is used to calculate the internal resistance of the battery pack. Obtain the dynamic internal resistance R of each battery pack, U is the collected voltage value of the battery pack, and I is the collected current value of the battery pack;

[0060] It should be noted that since the voltage and voltage value of the battery pack are collected at fixed intervals, the internal resistance calculated by the Ohm's law formula also has multiple data values, and therefore the internal resistance of each battery pack is dynamic;

[0061] Based on the historical charging power and discharging power data of each battery pack in the energy storage system, the dynamic internal resistance of each battery pack, and using a support vector machine algorithm, a state evaluation model of the battery pack in the energy storage system is constructed, and based on the state evaluation model, the aging degree value of each battery pack is output;

[0062] The specific construction method of the state evaluation model is:

[0063] S1, the historical charging power and discharging power data of each battery pack, and the dynamic internal resistance of each battery pack are used as a data set, and the data set is preprocessed, including: removing outliers in the data set, and filling missing values;

[0064] It should be noted that the data in the data set is divided into 3 columns of data according to the historical charging power, discharging power data, and dynamic internal resistance of each battery pack, the mean and standard deviation of each column of data are calculated, and the data deviating from the mean of each column of data by ±3 times the standard deviation is regarded as an outlier and the corresponding data is removed; the missing data in each column is filled according to the mean;

[0065] S2, divide the data set into a training set and a test set according to a ratio of 8:2, use the training set to train using a linear support vector machine algorithm, and use the test set to verify the training result of the model;

[0066] It should be noted that the training set data is used to train the support vector machine model, and the historical charging power, discharging power and dynamic internal resistance data in the training set are used as input features, and the corresponding battery pack aging degree value is used as an output label. During the training process, the support vector machine algorithm will find an optimal hyperplane according to the input features and output labels, so that battery pack data of different aging degrees can be classified;

[0067] S3, the state evaluation model outputs the aging degree value of each battery pack in the energy storage system;

[0068] Based on the aging degree value of the battery pack output by the state model and the power deviation value PI of each battery pack, a scatter plot of the aging degree value-power deviation value of the battery pack is drawn in a two-dimensional rectangular coordinate system with the aging degree value as the horizontal axis and the power deviation value as the vertical axis.

[0069] Using the polyfit function in the matplotlib library of Python to fit a trend line of the scatter plot of the aging degree value-power deviation value;

[0070] Specifically, the equation of the trend line is y=k*x+b, where k is the slope and b is the intercept;

[0071] If k>0, it indicates that the aging degree value-power deviation value presents a linear growth trend;

[0072] If k<0, it indicates that the aging degree value-power deviation value presents a linear decline trend;

[0073] Calculate the goodness of fit R of the trend line 2 to judge the fitting effect of the fitted trend line equation;

[0074] Specifically, the way to judge the fitting effect of the fitted trend line equation is as follows:

[0075] SS1, calculate the total sum of squares Where n is the number of data points, y i is the power deviation value of the i-th battery pack, i=1, 2, 3, n;

[0076] SS2, calculate the regression sum of squares By calculating the fitted power deviation value

[0077] SS3, calculate the residual sum of squares

[0078] SS4, by the formula: get the goodness of fit R of the trend line 2 ;

[0079] difference processing the goodness of fit R of the trend line 2 and the upper limit value of the goodness of fit to obtain the goodness of fit difference;

[0080] ratio processing the goodness of fit difference and the upper limit value of the goodness of fit to obtain the fitting proximity ratio;

[0081] Compare the fitting proximity ratio with the fitting proximity ratio threshold;

[0082] If the fitting proximity ratio is higher than the fitting proximity ratio threshold, it indicates that the fitting degree of the trend line is good, that is, the aging degree value-power deviation value presents a linear correlation trend, and if the k of the fitted trend line is greater than 0, it indicates that the aging degree value-power deviation value presents a linear growth correlation trend, that is, the higher the aging degree of the battery pack, the greater the power deviation value;

[0083] If the fitting closeness ratio is lower than the fitting closeness ratio threshold, it indicates that the trend line fit is poor, that is, the aging degree value - the power deviation value does not show a linear correlation trend;

[0084] For example, if there are three battery packs in the energy storage system, n=3, and the power deviation values ​​y1, y2, and y3 of battery packs 1, 2, and 3 are 0.25, 0.18, and 0.32 respectively, then the calculated SST is 0.0098, and the trend line equation is y=0.4*x+0.01. When the aging deviation values ​​x1, x2, and x3 of battery packs 1, 2, and 3 are 0.6, 0.4, and 0.8 respectively, the trend line formula is calculated to be The values ​​are 0.25, 0.17, and 0.33 respectively, and the SSE is calculated as 0.002 by the formula. Finally, the goodness of fit R is calculated. 2 is 0.98, the upper limit of goodness of fit is 1, and the threshold of fitting closeness is 0.80, then the energy storage system

[0085] Step 4: If the aging degree value minus the power deviation value shows a linear growth trend, the energy storage system's power control enters the power regulation layer. A battery aging sequence is constructed based on the aging degree value. The charge and discharge power of the battery pack in the battery aging sequence is numerically analyzed to obtain the upper limit charge power and the upper limit discharge power. The charge and discharge power of the battery pack are regulated based on the upper limit charge power and the upper limit discharge power.

[0086] If the fitting approximation ratio determines that the aging degree value minus the power deviation value shows a linear growth trend, the aging degree value of each battery pack is obtained, and a battery aging sequence is constructed in descending order of the aging degree values.

[0087] If the power deviation value PI of the battery group is greater than or equal to the power deviation threshold in the battery aging sequence, the battery group is marked as a power control group;

[0088] Regulating the battery groups in the power control group in sequence according to the battery aging sequence;

[0089] The specific battery pack control method of the power control group is:

[0090] Obtain a power deviation value PI of a battery group in the power control group, perform difference processing on the power deviation value PI and a power deviation threshold to obtain a power deviation difference;

[0091] The power deviation difference is compared with the power deviation threshold to obtain the power control ratio;

[0092] Obtain the maximum charging and discharging power of the battery group in the power control group, and multiply the maximum charging and discharging power of the battery group by the power control ratio to obtain the upper limit charging power and the upper limit discharging power;

[0093] Based on the charging upper limit power, the discharging upper limit power, the charging power and the discharging power of each battery pack are regulated using the energy storage converter;

[0094] It should be noted that the energy storage converter is a device for connecting the battery energy storage system to the power grid in the energy storage system, and the core components of the energy storage converter include a DC / DC converter, a DC / AC inverter, an AC / DC rectifier and a control unit thereof. The core components of the energy storage converter cooperate together. When each battery pack of the energy storage system reaches the charging upper limit power and the discharging upper limit power, the energy storage converter will control the power of the battery pack according to the charging upper limit power and the discharging upper limit power;

[0095] Embodiment three

[0096] The energy storage system charging and discharging power hierarchical control system based on the characteristics of lithium ion includes:

[0097] The data acquisition module: based on the characteristics of the lithium ion energy storage system, the power control of the energy storage system is divided into a system monitoring layer, a state evaluation layer and a power regulation layer. Based on the system monitoring layer, the charging and discharging power of each battery pack in the energy storage system is obtained, and the acquired charging and discharging power data is stored in a database;

[0098] The evaluation and judgment module: the charging and discharging power of each battery pack is obtained from the database, and a curve analysis is drawn to obtain the correlation coefficient of the curve. The correlation coefficient of the charging and discharging power curve is numerically calculated to obtain a power deviation PI. Based on the power deviation PI, it is judged whether the state of the battery pack needs to be evaluated;

[0099] The evaluation and analysis module: if the state of the battery pack needs to be evaluated, the energy storage system is in the state evaluation layer, the historical charging and discharging power data of each battery pack in the energy storage system and the dynamic internal resistance of each battery pack are obtained to establish a state evaluation model, and the aging degree value of each battery pack is output. Combined with the power deviation, a fitting analysis is performed to obtain a fitting approximation ratio. Based on the fitting approximation ratio, it is judged whether the aging degree value-power deviation presents a linear growth trend;

[0100] The power regulation module: if the aging degree value-power deviation presents a linear growth trend, the power control of the energy storage system enters the power regulation layer. Based on the aging degree value, a battery aging sequence is constructed, the charging and discharging power of the battery pack of the battery aging sequence is numerically analyzed to obtain the charging upper limit power and the discharging upper limit power, and based on the charging upper limit power and the discharging upper limit power, the charging and discharging power of the battery pack is regulated using the energy storage converter;

[0101] Embodiment four

[0102] Reference Figure 3The embodiment of the present application further provides a computer device 3, comprising a memory 302, a processor 301 and a computer program 303 stored in the memory 302, and when the computer program 303 is executed on the processor 301, the computer program 303 implements the energy storage system charge-discharge power hierarchical control method based on lithium ion characteristics according to any one of the above methods.

[0103] The computer device 3 can be a desktop computer, a notebook computer, a palm computer, a cloud server and the like. The computer device 3 can comprise, but is not limited to, the processor 301 and the memory 302. Those skilled in the art can understand that the computer device 3 can include more or less components, or combine some components, or different components, for example, the computer device 3 can further comprise an input / output device, a network access device and the like.

[0104] Figure 3 The computer device 3 is only an example and does not constitute a limitation on the computer device 3, and the computer device 3 can include more or less components, or combine some components, or different components, for example, the computer device 3 can further comprise an input / output device, a network access device and the like.

[0105] The processor 301 can be a central processing unit (CPU), and the processor 301 can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0106] The memory 302 can be an internal storage unit of the computer device 3 in some embodiments, for example, a hard disk or a memory of the computer device 3. The memory 302 can also be an external storage device of the computer device 3 in other embodiments, for example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card and the like equipped on the computer device 3. Further, the memory 302 can include both the internal storage unit and the external storage device of the computer device 3. The memory 302 is used to store an operating system, application programs, a boot loader, data and other programs, for example, program codes of the computer program and the like. The memory 302 can also be used to temporarily store data that has been output or will be output.

[0107] Embodiment five

[0108] The embodiment of the present application also provides a computer readable storage medium, which stores a computer program, and the computer program is run by a processor to implement the energy storage system charge-discharge power hierarchical control method based on lithium ion characteristics according to any one of the above methods.

[0109] In the embodiment, the integrated unit, if in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the present application can implement all or part of the processes of the above-mentioned embodiment methods by a computer program to instruct related hardware, and the computer program can be stored in a computer readable storage medium. The computer program can implement the steps of the above-mentioned method embodiments when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable file or some intermediate form. The computer readable medium at least includes any entity or device capable of carrying the computer program code to the photographing device / terminal equipment, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium. For example, U disk, mobile hard disk, magnetic disk or optical disk, etc. In some jurisdictions, according to legislation and patent practice, the computer readable medium can not be an electrical carrier signal and a telecommunication signal.

[0110] In the above embodiments, the description of each embodiment has its own focus, and the parts not described or recorded in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0111] Those skilled in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0112] In the embodiments disclosed in the present application, it should be understood that the disclosed apparatus / terminal device and method can be implemented in other manners. For example, the embodiments of the apparatus / terminal device described above are merely schematic; for example, the division of the modules or units is merely logical function division; an actual mapping of the modules or units can be different, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between the units can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or in other forms.

[0113] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments of the present application.

[0114] The above formulas are dimensionless values calculated, and the formulas are obtained by software simulation of a large amount of data to obtain a formula of the most recent real situation. The preset parameters in the formula are set by a person skilled in the art according to the actual situation.

[0115] The above describes one embodiment of the present application in detail, but the content described is only a preferred embodiment of the present application, and cannot be considered as limiting the scope of the present application. Any equivalent changes and improvements made according to the scope of the present application should still belong to the patent coverage of the present application.

Claims

1. A power layering control method for charging and discharging of an energy storage system based on lithium-ion characteristics, characterized in that, The method comprises the following steps: Based on the characteristics of lithium ion energy storage system, the power control of the energy storage system is divided into three levels: system monitoring layer, state evaluation layer and power regulation layer. Based on the system monitoring layer, the charging and discharging power of each battery pack in the energy storage system is obtained, and the collected charging and discharging power data is stored in the database; The charging and discharging power of each battery pack is obtained from the database, and the curve analysis is drawn to obtain the correlation coefficient of the curve. The correlation coefficient of the charging and discharging power curve is numerically calculated to obtain the power deviation value. Based on the power deviation value, it is judged whether the state of the battery pack needs to be evaluated; If the state of the battery pack needs to be evaluated, the energy storage system is in the state evaluation layer. The historical charging and discharging power data of each battery pack in the energy storage system and the dynamic internal resistance of each battery pack are obtained to establish a state evaluation model, and the aging degree value of each battery pack is output. Combined with the power deviation value, fitting analysis is performed to obtain the fitting approximation ratio. Based on the fitting approximation ratio, it is judged whether the aging degree value-power deviation value presents a linear growth trend. If the aging degree value-power deviation value presents a linear growth trend, the power control of the energy storage system enters the power regulation layer. Based on the aging degree value, a battery aging sequence is constructed, and the charging and discharging power of the battery pack in the battery aging sequence is numerically analyzed to obtain the charging upper limit power and the discharging upper limit power. The charging and discharging power of the battery pack is regulated by using the energy storage converter.

2. The energy storage system charging and discharging power hierarchical control method based on the characteristics of lithium ion according to claim 1, characterized in that: The power deviation value is obtained in the following way: Based on the curve matching degree Pd of the time-charging power change curve and the curve matching degree Fd of the time-discharging power change curve, the power deviation value is calculated. The power deviation value PI is obtained by the formula: where c = 0.483 and d = 0.

517. The method for determining whether the state of the battery pack needs to be evaluated is as follows: If the power deviation value is greater than or equal to the power deviation threshold value, the state of the battery pack needs to be evaluated.

3. The energy storage system charging and discharging power hierarchical control method based on the characteristics of lithium ion according to claim 2, characterized in that: The curve matching degree Pd of the time-charging power change curve is obtained in the following way: Based on the approximation section ratio Jq and the correlation ratio average Xg, the curve matching degree Pd of the time-charging power change curve is calculated. The curve matching degree Pd of the time-charge power variation curve is obtained by the formula: where a = 0.213, b = 0.

787. The curve matching degree Fd of the time-discharging power change curve is obtained in the following way: The curve matching degree Fd of the time-discharging power change curve is calculated based on the curve matching degree calculation method of the time-charging power change curve.

4. The energy storage system charging and discharging power hierarchical control method based on the characteristics of lithium ion according to claim 3, characterized in that: The approximation section ratio Jq and the correlation ratio average Xg are obtained in the following way: The power meter is used to collect the charging and discharging power of the energy storage system at fixed interval time. The charging power collected by the power meter is input into the MatLab software to draw the time-charging power change curve and the time-discharging power change curve. The correlation coefficient function of MatLab is used to analyze the coincidence degree of the time-charging power change curve and the charging target curve, and the correlation coefficient of the curve is obtained. The time-charging power change curve is divided into multiple sub-sections, and the correlation coefficient of each sub-section is obtained. The correlation coefficient is compared with the correlation coefficient threshold value, and if the correlation coefficient is higher than the correlation coefficient threshold value, the sub-section is marked as an approaching section. The number of all approaching sections and the number of all sub-sections are obtained, and the number of approaching sections is processed by ratio with the number of sub-sections to obtain an approaching section ratio, which is marked as Jq. The correlation coefficient in the approaching section is processed by difference with the correlation coefficient threshold value to obtain a correlation coefficient difference. The correlation coefficient difference is processed by ratio with the correlation coefficient threshold value to obtain a correlation approaching ratio. The correlation approaching ratios of all approaching sections are obtained, and the sum of the correlation approaching ratios of all approaching sections is processed by mean value to obtain a correlation ratio mean value, which is marked as Xg.

5. The energy storage system charge and discharge power hierarchical control method based on lithium ion characteristics according to claim 1, characterized in that, the state evaluation model is constructed in the following manner: The energy storage system is in the state evaluation layer, and the historical charging power and discharging power data of each battery pack in the energy storage system, and the dynamic internal resistance of each battery pack are obtained. Based on the historical charging power and discharging power data of each battery pack in the energy storage system, and the dynamic internal resistance of each battery pack, a support vector machine algorithm is used to construct a state evaluation model of the battery packs in the energy storage system, and based on the state evaluation model, an aging degree value of each battery pack is output. The state evaluation model is constructed in the following manner: S1, the historical charging power and discharging power data of each battery pack, and the dynamic internal resistance of each battery pack are taken as a data set, and the data set is preprocessed, including removing outliers in the data set and filling missing values; S2, the data set is divided into a training set and a test set according to a ratio of 8:2, the training set is used to train the state evaluation model, and the test set is used to verify the training result of the model; S3, the state evaluation model outputs the aging degree value of each battery pack in the energy storage system.

6. The energy storage system charge and discharge power hierarchical control method based on lithium ion characteristics according to claim 1, characterized in that, the manner of judging whether the aging degree value-power deviation value presents a linear growth trend is as follows: The fitting approaching ratio is compared with the fitting approaching ratio threshold value; If the fitting approaching ratio is higher than the fitting approaching ratio threshold value, and k>0 of the fitting trend line, it indicates that the aging degree value-power deviation value presents a linear growth trend.

7. The energy storage system charge and discharge power hierarchical control method based on lithium ion characteristics according to claim 6, characterized in that, The fitting approximation ratio is obtained by: taking the difference between the upper limit value of the goodness of fit of the trend line and the goodness of fit of the trend line 2 The goodness of fit difference is obtained by taking the difference between the upper limit value of the goodness of fit and the goodness of fit of the trend line. the goodness of fit difference is processed by ratio with the upper limit value of the goodness of fit to obtain the fitting approaching ratio.

8. The energy storage system charge and discharge power hierarchical control method based on lithium ion characteristics according to claim 7, characterized in that, The goodness of fit R 2 The acquisition mode is: Based on the state model output of the aging degree value of the battery pack, the power deviation value PI of each battery pack, in a two-dimensional rectangular coordinate system, the aging degree value is taken as the horizontal axis, and the power deviation value is taken as the vertical axis, the scatter plot of the aging degree value-power deviation value of the battery pack is drawn; Using the polyfit function in the matplotlib library of Python, a trend line is fitted to the scatter plot of the aging level value - power deviation value, and the equation of the trend line is where k is the slope and b is the intercept. If k>0, it indicates that the aging degree value-power deviation value presents a linear growth trend; If k<0, it indicates that the aging degree value-power deviation value presents a linear decline trend; R of the fitting goodness of the trend line 2 , judging the fitting effect of the trend line equation The fitting effect of the fitting trend line equation is judged as follows: SS1, compute total sum of squares where n is the number of data points, y i is the power deviation value for the i-th battery; SS2, calculating regression sum of squares , by , calculating the fitted power deviation value corresponding to the aging degree value x ; SS3, compute residual sum of squares ; SS4, by the formula: R of the goodness of fit of the trend line is obtained 2 .

9. The energy storage system charge-discharge power hierarchical control method based on lithium ion characteristics according to claim 1, characterized in that, The charging and discharging power of the battery pack is regulated as follows: Obtain the power deviation value PI of the battery pack in the power control group, and perform difference processing on the power deviation value PI and the power deviation threshold to obtain the power deviation difference; Perform ratio processing on the power deviation difference and the power deviation threshold to obtain the power regulation ratio; Obtain the maximum charging and discharging power of the battery pack in the power control group, and perform product processing on the maximum charging and discharging power of the battery pack and the power regulation ratio respectively to obtain the upper limit charging power and the upper limit discharging power; Based on the upper limit charging power and the upper limit discharging power, the charging power and the discharging power of each battery pack are regulated using the energy storage converter.

10. The energy storage system charge-discharge power hierarchical control method based on lithium ion characteristics according to claim 9, characterized in that, The power control group is obtained as follows: If the fitting approximation ratio indicates that the aging degree value-power deviation value presents a linear growth trend, obtain the aging degree value of each battery pack, and construct a battery aging sequence in the order of the aging degree value from large to small; If the power deviation value PI of the battery pack in the battery aging sequence is greater than or equal to the power deviation threshold, mark the battery pack as a power control group, and regulate the battery packs in the power control group in the order of the battery aging sequence.

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