A method and system for fast charging of energy storage based on ultra-capacitive coupled lithium battery

Abstract

The present invention discloses a method and system for fast charging of energy storage based on supercapacitor coupled lithium batteries, which relates to the technical field of energy storage optimization, including collecting voltage and resistance data and determining the rate of change; determining the relationship between internal resistance and current by fitting; determining the relationship between current changes over time, and constructing an objective function of minimum charging time and power loss. The method for fast charging of energy storage based on supercapacitor coupled lithium batteries provided by the present invention determines the optimal current state by constructing an objective function, optimizes charging of the variable type, reduces charging time and power loss at the same time, significantly reduces energy storage costs, decomposes current into four states, and calculates them separately, significantly improving calculation efficiency and calculation accuracy. The present invention achieves better results in terms of cost saving, calculation efficiency and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage optimization, and in particular to an energy storage fast charging method and system based on a supercapacitor coupled lithium battery. Background Art

[0002] For thermal power units, long-term frequency regulation will lead to increased coal consumption, reduced reliability, and shortened operating life. On the other hand, high-quality and efficient frequency regulation power sources are scarce. At present, coal-fired thermal power units are still the main frequency regulation power source. In addition, the large-scale demand for new energy grid connection, environmental protection pressure restricts the regulation capacity of units, and the heating units "determine electricity by heat" and other problems have further increased the demand for power frequency regulation. However, the performance of the auxiliary frequency regulation energy storage equipment of thermal power plants cannot meet the efficiency and reliability requirements of the units themselves, which affects the acquisition of grid subsidy income and has low economic benefits.

[0003] In response to these problems, there are now energy storage systems with supercapacitor coupled lithium batteries on the market. Generator sets are rotating large-capacity active and reactive sources, while energy storage systems can be regarded as static relatively small-capacity power generators. The main difference between the two lies in their different output ranges and response characteristics. The former has a large output range but slow response speed, while the latter has a relatively small capacity but fast response speed. The coordinated operation between the two can significantly improve the execution effect of thermal power units on the AGC instructions of the power grid. By utilizing the ability of the energy storage system to quickly adjust the output power, the thermal power unit is used as the basic unit to respond to the AGC instructions, and the energy storage system is used as a supplementary fast response unit. The unit output and the energy storage system output are combined and sent to the power grid as the total system output, which can achieve the purpose of improving the AGC performance of the unit. Single lithium battery energy storage or single supercapacitor energy storage cannot simultaneously meet the high power density required by the primary frequency regulation of thermal power and the high energy density required by the secondary frequency regulation. The hybrid energy storage technology combined with the two can achieve complementary advantages and improve system performance. In the control strategy of the hybrid energy storage system, the method of preferentially calling supercapacitors is adopted. For small instructions, the supercapacitor responds completely; for large instructions, the supercapacitor responds at full power, and the lithium battery is used as a supplement. In this way, the charge and discharge depth of the lithium battery can be made shallower, which is more conducive to extending the life. However, the charging time and energy loss in the charging process of the lithium battery are two conflicting goals. Shortening the charging time can reduce the response time of the energy storage system, but the charging current needs to be increased, which will also increase the energy loss. Excessive energy loss will result in reduced energy utilization efficiency and increased costs. If the charging current is reduced, the charging time will be increased. Over time, the increased response time will affect the frequency modulation benefits. In order to solve this problem, the present invention proposes a variable current charging strategy that shortens the charging time while ensuring that the energy loss is as small as possible. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: the existing auxiliary frequency regulation energy storage method has insufficient reliability and low frequency regulation efficiency, and the problem of how to improve economic benefits.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for fast charging of energy storage based on ultracapacitive coupled lithium batteries, comprising collecting voltage and resistance data and determining the rate of change. The relationship between internal resistance and current is determined by fitting. The relationship between current and time is determined, and an objective function of minimum charging time and power loss is constructed.

[0007] As a preferred solution of the energy storage fast charging method based on the ultra-capacitive coupled lithium battery of the present invention, wherein: the voltage resistance data acquisition includes collecting 100 sets of current and internal resistance data, wherein the current intensity ranges from I1 to I 100 Gradually increase, the internal resistance decreases from R1 to R 100 , collect 100 sets of data [I1 R1] [I2 R2] [I3 R3],...,[I 100 R 100 ].

[0008] As a preferred solution of the energy storage fast charging method based on the ultra-capacitor coupled lithium battery of the present invention, wherein: the determination of the change rate includes calculating the change rate of each group of data, which is expressed as:

[0009] ,

[0010] in, Represents the rate of change of the i-th group of data.

[0011] There are 99 change rates K1, K2, K3, ..., K in 100 sets of data. 99 .

[0012] The rate of change of the rate of change is expressed as:

[0013] ,

[0014] There are 98 groups of change rates.

[0015] As a preferred solution of the energy storage fast charging method based on the ultra-capacitive coupled lithium battery of the present invention, wherein: the relationship between the internal resistance and the current is determined by fitting, including setting the internal resistance The current changes with time as ,make , the power loss function is expressed as:

[0016] ,

[0017] The charging time is calculated by the capacitance and is expressed as:

[0018] ,

[0019] Among them, Q represents the battery capacity and T represents the time required to fully charge.

[0020] Infinite approximation through negative fitting , expressed as:

[0021] ,

[0022] in, express The second derivative of express The derivative of , m and n represent unknown coefficients, which are random values ​​in [1,99]. m and n are given randomly first. Substitute into K1, Substitute K1` and get I1`, calculate to I 98 `And calculate the error of the data collected by the experiment:

[0023] ,

[0024] in, Represents the i-th group of errors, and then randomly assigns another group of m and n, repeats the calculation until , select middle The corresponding m and n, m and n are determined and then solved In , get the confirmed Get the relationship between internal resistance and current.

[0025] As a preferred solution of the energy storage fast charging method based on the supercapacitor coupled lithium battery described in the present invention, wherein: the determination of the relationship between the change of current and time includes decomposing the current into four parts, a constant current part, an oscillating part, a continuously increasing part and a decreasing part.

[0026] The constant current part is expressed as:

[0027] ,

[0028] in, Indicates the constant current value.

[0029] The oscillating part is expressed as:

[0030] ,

[0031] in, represents the oscillating current amplitude, represents the oscillation angular frequency.

[0032] The continuous growth part is expressed as:

[0033] ,

[0034] in, Indicates the rate of increase of current.

[0035] The reduced part is expressed as:

[0036] ,

[0037] in, Indicates the rate at which the current decreases.

[0038] As a preferred solution of the energy storage fast charging method based on the supercapacitor coupled lithium battery described in the present invention, wherein: the determination of the relationship between the change of current and time also includes determining the loss power and charging time of the constant current part, the oscillation part, the continuous increase part and the decrease part.

[0039] The power loss and charging time of the constant current part are expressed as:

[0040] ,

[0041] ,

[0042] The power loss and charging time of the oscillation part are expressed as:

[0043] ,

[0044] ,

[0045] The power loss and charging time of the continuous increase part are expressed as:

[0046] ,

[0047] ,

[0048] The reduced power loss and charging time are expressed as:

[0049] ,

[0050] .

[0051] As a preferred solution of the energy storage fast charging method based on the supercapacitor coupled lithium battery of the present invention, the objective function of constructing the minimum charging time and the power loss includes constructing a minimization objective function based on the values ​​of the power loss and the charging time, which is expressed as:

[0052] Keep giving Substitute the value into the objective function, loop 100 times, and find F s The minimum value corresponds to , the optimal energy storage state at this time is expressed as:

[0053] ,

[0054] in, , , , as well as It is the value corresponding to the minimum Fs.

[0055] Another object of the present invention is to provide an energy storage and fast charging system based on an ultra-capacitor coupled lithium battery, which can determine the optimal current state by constructing an objective function, optimize charging in a variable-power manner, and reduce charging time and power loss at the same time, thereby solving the problem that the current auxiliary frequency modulation energy storage method contains excessive power loss in order to speed up charging time.

[0056] As a preferred solution of the energy storage fast charging system based on the ultra-capacitor coupled lithium battery described in the present invention, it includes: a data acquisition module, a fitting module, and a charging strategy optimization module. The data acquisition module is used to collect voltage resistance data and determine the rate of change. The fitting module is used to determine the relationship between internal resistance and current by fitting. The charging strategy optimization module is used to determine the relationship between the current and time, and construct an objective function of minimum charging time and power loss.

[0057] A computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement a step of a method for fast charging of energy storage based on a supercapacitor coupled lithium battery.

[0058] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for fast charging of energy storage based on a supercapacitor coupled lithium battery.

[0059] Beneficial effects of the present invention: The energy storage fast charging method based on the supercapacitor coupled lithium battery provided by the present invention determines the optimal current state by constructing an objective function, optimizes charging in a variable-power manner, reduces charging time and power loss, significantly reduces energy storage costs, decomposes the current into four states, calculates them separately, and significantly improves calculation efficiency and calculation accuracy. The present invention achieves better results in terms of cost saving, calculation efficiency and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0061] Figure 1 An overall flow chart of a method for fast energy storage and charging based on a supercapacitor coupled lithium battery provided in the first embodiment of the present invention.

[0062] Figure 2 A schematic diagram of a module of an energy storage and fast charging system based on an ultra-capacitor coupled lithium battery provided in the third embodiment of the present invention. DETAILED DESCRIPTION

[0063] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0064] Example 1, reference Figure 1 , is an embodiment of the present invention, and provides a method for fast charging of energy storage based on a supercapacitor coupled lithium battery, comprising:

[0065] S1: Collect voltage-resistance data and determine the rate of change.

[0066] Furthermore, the voltage resistance data acquisition includes collecting 100 sets of current and internal resistance data, where the current intensity ranges from I1 to I 100 Gradually increase, the internal resistance decreases from R1 to R 100 , collect 100 sets of data [I1 R1] [I2 R2] [I3R3],...,[I 100 R 100 ].

[0067] It should be noted that determining the rate of change includes calculating the rate of change of each set of data, expressed as:

[0068] ,

[0069] in, Represents the rate of change of the i-th group of data.

[0070] There are 99 change rates K1, K2, K3, ..., K in 100 sets of data. 99 .

[0071] The rate of change of the rate of change is expressed as:

[0072] ,

[0073] There are 98 groups of change rates.

[0074] It should also be noted that if the lithium battery needs to be charged, the charging current is (The current is a function of time). The relationship between current and temperature found in existing technologies is:

[0075] ,

[0076] Among them, P R0 Represents the ohmic internal resistance power loss, R0 represents the internal resistance. There is a problem with the existing derivation formula: R0 is not actually a constant value. The size of the internal resistance is related to the temperature, and the temperature is related to the current size and time. Therefore, R0 is actually related to the current size and current duration.

[0077] S2: Determine the relationship between internal resistance and current through fitting.

[0078] Furthermore, the relationship between internal resistance and current is determined by fitting, including setting the internal resistance The current changes with time as ,make , the power loss function is expressed as:

[0079] ,

[0080] The charging time is calculated by the capacitance and is expressed as:

[0081] ,

[0082] Among them, Q represents the battery capacity, T represents the time required to fully charge. In the energy storage system, the smaller the energy storage time and power loss, the better.

[0083] Infinite approximation through negative fitting , expressed as:

[0084] ,

[0085] in, express The second derivative of express The derivative of , m and n represent unknown coefficients, which are random values ​​in [1,99]. m and n are given randomly first. Substitute into K1, Substitute K1` and get I1`, calculate to I 98 `And calculate the error of the data collected by the experiment:

[0086] ,

[0087] in, Represents the i-th group of errors, and then randomly assigns another group of m and n, repeats the calculation until , select middle The corresponding m and n, m and n are determined and then solved In , get the confirmed Get the relationship between internal resistance and current.

[0088] It should be noted that determining the relationship between the change of the current and time includes decomposing the current into four parts, a constant current part, an oscillating part, a continuously increasing part, and a decreasing part.

[0089] The constant current part is expressed as:

[0090] ,

[0091] in, Indicates the constant current value.

[0092] The oscillating part is expressed as:

[0093] ,

[0094] in, represents the oscillating current amplitude, represents the oscillation angular frequency.

[0095] The continuous growth part is expressed as:

[0096] ,

[0097] in, Indicates the rate of increase of current.

[0098] The reduced part is expressed as:

[0099] ,

[0100] in, Indicates the rate at which the current decreases.

[0101] S3: Determine the relationship between current and time, and construct the objective function of minimum charging time and power loss.

[0102] Furthermore, determining the relationship between the change of current and time also includes determining the loss power and charging time of the constant current part, the oscillation part, the continuous increase part and the decrease part.

[0103] The power loss and charging time of the constant current part are expressed as:

[0104] ,

[0105] ,

[0106] The power loss and charging time of the oscillation part are expressed as:

[0107] ,

[0108] ,

[0109] The power loss and charging time of the continuous increase part are expressed as:

[0110] ,

[0111] ,

[0112] The reduced power loss and charging time are expressed as:

[0113] ,

[0114] .

[0115] It should be noted that constructing the objective function of minimum charging time and power loss includes constructing a minimization objective function based on the values ​​of power loss and charging time, which is expressed as:

[0116] Keep giving Substitute the value into the objective function, loop 100 times, and find F s The minimum value corresponds to , the optimal energy storage state at this time is expressed as:

[0117] ,

[0118] in, , , , as well as It is the value corresponding to the minimum Fs.

[0119] Example 2, an embodiment of the present invention, provides a method for fast charging of energy storage based on supercapacitor coupled lithium batteries. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0120] First, the main purpose of the experiment is to compare the performance differences between the variable current charging strategy of the present invention and the prior art (constant current charging strategy), especially in terms of charging time and energy loss.

[0121] The supercapacitor and lithium battery pack were connected in parallel to a variable current power supply and a constant current power supply, and two groups of experiments were conducted. The first group used a constant current charging strategy, and the second group used a variable current charging strategy.

[0122] During the experiment, the charging current, voltage, charging time and temperature changes were recorded in real time. Each group of experiments was performed 20 times.

[0123] Constant current charging strategy: Set the constant current power supply output current to 1A, start charging the supercapacitor and lithium battery pack, and record the data during the charging process until the battery pack reaches the rated voltage.

[0124] Table 1 Experimental data comparison table

[0125] ,

[0126] Referring to Table 1, we can see that the average charging time of the variable current charging strategy is about 90 minutes, while the average charging time of the constant current charging strategy is about 125 minutes. The variable current charging strategy shortens the charging time by about 28%, significantly improving the response speed and efficiency of the system.

[0127] The average energy loss of the variable current charging strategy is 3.6Wh, while the average energy loss of the constant current charging strategy is 4.4Wh. The variable current charging strategy reduces energy loss by about 18% and improves energy utilization efficiency.

[0128] Since energy loss is mainly manifested in the form of heat, from a temperature perspective, by optimizing the charging current, the variable current charging strategy effectively reduces the temperature rise during the charging process, which is beneficial to extending the service life of the lithium battery.

[0129] The maximum current of the variable current charging strategy is 2.0A, while the constant current charging strategy is 1.0A. The variable current charging strategy can provide higher current in a short time, improve charging efficiency, and reduce energy loss and temperature rise by reducing current in the later stage.

[0130] Example 3, reference Figure 2 , which is an embodiment of the present invention, provides an energy storage fast charging system based on super-capacitor coupled lithium batteries, including a data acquisition module, a fitting module, and a charging strategy optimization module.

[0131] The data acquisition module is used to collect voltage and resistance data and determine the rate of change. The fitting module is used to determine the relationship between internal resistance and current through fitting. The charging strategy optimization module is used to determine the relationship between current and time and construct the objective function of minimum charging time and power loss.

[0132] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0133] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0134] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk case (magnetic devices), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0135] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logical function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc. It should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limited. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

[0136] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for fast charging of energy storage based on supercapacitor coupled lithium battery, characterized in that: include: Conduct voltage-resistance data collection and determine the rate of change; Determine the relationship between internal resistance and current by fitting; Determine the relationship between current and time, and construct the objective function of minimum charging time and power loss; Determining the change rate includes calculating the change rate of each set of data, expressed as: Among them, K i represents the rate of change of the i-th group of data; There are 99 change rates K1, K2, K3, ..., K in 100 sets of data. 99 ; The rate of change of the rate of change is expressed as: K i 、 =K i+1 -K i There are 98 groups of change rates; The objective function of constructing the minimum charging time and power loss includes constructing a minimization objective function based on the values ​​of power loss and charging time, which is expressed as: Keep assigning values ​​of [b,A,w,C,D] to the objective function, loop 100 times, and find F s The minimum value of [b, A, w, C, D] corresponds to the optimal energy storage state: Among them, b min , A min 、w min , C min and D min F s The value corresponding to the minimum; The relationship between the internal resistance and the current determined by fitting includes setting the internal resistance R0 and the current to change with time as f(t)=I, setting R0=f2(f(t)), and the power loss function is expressed as: P R0 =f 2 (t)(f2(f(t))) The charging time is calculated by the capacitance and is expressed as: Among them, Q represents the battery capacity, and T represents the time required to fully charge; Through the negative fitting method, f2 is infinitely approximated, which is expressed as: f2(I) (2) -If2(I) (1) +me -nI =0 Among them, f2(I) (2) represents the second derivative of f2(I), f2(I) (1) represents the derivative of f2(I), m and n represent the unknown coefficients, which are random values ​​in [1,99]. m and n are given randomly first, f2(I) (1) Substitute K1, f2(I) (2) Substitute K1` and get I1`, calculate to I 98 `And calculate the error between the calculated and experimentally collected data: Among them, Δ1 represents the error of the i-th group, and then another group of m and n is randomly given, and the calculation is repeated until Δ 100 , select Δ1, Δ2, Δ ,3 , ..., Δ 100 Medium Δ min The corresponding m and n, after m and n are determined, solve f2(I) (2) -If2(I) (1) +me -nI = f2(I) in 0, get the determined f2 to get the relationship between internal resistance and current; Determining the relationship between the current and time includes decomposing the current into four parts, a constant current part, an oscillating part, a continuously increasing part, and a decreasing part; The constant current part is expressed as: f(t) 恒流 =b Wherein, b represents the constant current value; The oscillating part is expressed as: f(t) 振荡 =Asin(wt) Where A represents the oscillation current amplitude, and w represents the oscillation angular frequency; The continuous growth part is expressed as: f(t) 增大 =Ct(C>0) Where, C represents the current increase rate; The reduced part is expressed as: f(t) 减小 =e -Dt (D>0) Where D represents the current reduction rate; Determining the relationship between the current and time also includes determining the loss power and charging time of the constant current part, the oscillation part, the continuous increase part and the decrease part; The power loss and charging time of the constant current part are expressed as: P R0恒流 =b 2 (f2(b)) The power loss and charging time of the oscillation part are expressed as: P R0振荡 =A 2 are 2 (wt)(f2(Salt(wt))) The power loss and charging time of the continuous increase part are expressed as: P R0增大 =C 2 t 2 (f2(Ct)) The reduced power loss and charging time are expressed as: P R0增大 =e -2Dt (f2(e -Dt )) 2. The energy storage fast charging method based on the supercapacitor coupled lithium battery according to claim 1, characterized in that: The voltage resistance data acquisition includes collecting 100 sets of current and internal resistance data, where the current intensity ranges from I1 to I 100 Gradually increase, the internal resistance decreases from R1 to R 100 , collect 100 sets of data [I1 R1][I2 R2][I3 R3],...,[I 100 R 100 ].

3. A system using the energy storage fast charging method based on the supercapacitor coupled lithium battery as described in any one of claims 1 to 2, characterized in that: Including data acquisition module, fitting module, and charging strategy optimization module; The data acquisition module is used to collect voltage and resistance data and determine the rate of change; The fitting module is used to determine the relationship between internal resistance and current through fitting; The charging strategy optimization module is used to determine the relationship between the current and time, and to construct an objective function of minimum charging time and power loss.

4. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the energy storage and fast charging method based on the super-capacitor coupled lithium battery described in any one of claims 1 to 2 are implemented.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the energy storage fast charging method based on the super-capacitor coupled lithium battery described in any one of claims 1 to 2 are implemented.

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