A lithium battery pack charge and discharge management method and system

Abstract

The present invention relates to a lithium battery pack charge and discharge management method and system, belonging to the field of battery pack charge and discharge. The method is applied to an energy storage system including a container lithium battery pack, wherein the lithium battery pack comprises i parallel branches, i is a positive integer less than or equal to n, and n is the number of branches; the method comprises: when i ranges from 1 to n / 2, the branch charge and discharge rate C i Gradually decreases; when i is from n / 2 to n, the branch charge and discharge rate C i The present invention improves the thermal safety and life of the container lithium battery pack.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery pack charging and discharging, and in particular relates to a lithium battery pack charging and discharging management method and system. Background Art

[0002] With the large-scale integration of photovoltaic and wind power into the grid, energy storage systems have become an essential component of power grid operations, and containerized energy storage systems based on lithium-ion battery packs are a prime example. The integration of containerized lithium-ion battery energy storage systems into the grid allows for direct demand-side management, rapidly charging units during low load periods and rapidly discharging them during peak load periods. This reduces the load differential between peaks and valleys, as well as the diurnal peak-valley difference, effectively improving the stability of power system operations. Furthermore, traditional energy suppliers and users, such as power plants and users, can capitalize on the price differential between peaks and valleys to generate revenue and improve operational efficiency. In conjunction with distributed generation, these systems can effectively reduce energy costs, leading to widespread adoption of containerized lithium-ion battery energy storage systems.

[0003] However, containerized lithium battery energy storage systems are generally placed outdoors, and the battery packs are placed very densely. Heat accumulation is easy to form during the charging and discharging process, causing the temperature inside the container to rise significantly and causing temperature inconsistencies between batteries, thereby affecting the charging and discharging performance of the battery pack. It also brings the risk of thermal runaway of the battery pack, posing a huge thermal safety hazard. The thermal safety issue during the operation of the containerized lithium battery energy storage system is one of the problems that need to be solved.

[0004] In addition, the energy storage system includes multiple energy storage branches. Any energy storage branch includes energy storage batteries and DC / DC converters connected in series. The output ends of each energy storage branch and the output ends of the photovoltaic system are respectively connected to the DC side of the inverter, and the AC side of the inverter is connected to the AC power grid. The controller is respectively connected to each energy storage branch in the energy storage system to control the charging and discharging process of each energy storage branch.

[0005] In actual applications, the controller will obtain the total power to be distributed of the energy storage system in any control cycle, and then distribute the total power to be distributed among each energy storage branch according to the SOC value of the energy storage battery in each energy storage branch, and control the charging and discharging process of the corresponding energy storage branch according to the corresponding distributed power of each energy storage branch.

[0006] In the existing technology, the total power to be allocated is distributed among the energy storage branches in each control cycle, which may easily lead to the energy storage branches being unable to effectively respond to power allocation instructions because their own shared power is greater than the corresponding limit value, thereby causing the entire photovoltaic storage system to be unable to meet actual application requirements. In addition, when meeting the limit, the thermal risk caused by the temperature rise of the battery pack is not considered. Therefore, the power allocation of each energy storage branch to the thermal safety risk of the battery pack is also a problem that needs to be solved. Summary of the Invention

[0007] The object of the present invention is to provide a lithium battery pack charge and discharge management method and system, thereby improving the thermal safety and life of the container lithium battery pack.

[0008] A lithium battery pack charge and discharge management method is applied to an energy storage system including a container lithium battery pack, wherein the lithium battery pack includes i parallel branches, where i is a positive integer less than or equal to n, and n is the number of branches;

[0009] The method comprises:

[0010] When i is from 1 to n / 2, the branch charge and discharge rate C i gradually decrease;

[0011] When i changes from n / 2 to n, the branch charge and discharge rate C i Gradually increase.

[0012] Optionally, the output end of the energy storage system is connected to the power grid via a DC / AC inverter; it also includes a photovoltaic or wind energy system, and the output end of the photovoltaic or wind energy system is also connected to the DC side of the DC / AC inverter.

[0013] Optionally, n is divisible by 4.

[0014] A lithium battery pack charge and discharge management method is applied to an energy storage system including a controller and a container lithium battery pack, wherein the lithium battery pack includes i parallel branches, where i is a positive integer less than or equal to n, and n is the number of branches. Each branch includes M batteries connected in series and parallel, where M is a positive integer.

[0015] The method comprises:

[0016] The controller obtains the total charge and discharge power of the lithium battery pack in the current control cycle and the operating power of the lithium battery pack of each branch in the previous control cycle;

[0017] The total charge and discharge power is the set power of the lithium battery pack in the current control cycle; the operating power of the lithium battery pack in the previous control cycle is the sum of the charge and discharge power of each branch in the previous control cycle;

[0018] The adjusted power is the set power minus the operating power;

[0019] Allocating the adjusted power to each of the branches to obtain the charge and discharge power of each of the branches in the current control cycle;

[0020] The controller controls the charging and discharging of the corresponding branch based on the charging and discharging power of the current control cycle of each branch.

[0021] Optionally, allocating the adjusted power to each branch is specifically:

[0022] When i is from 1 to n / 2, the branch charge and discharge rate C i gradually decrease;

[0023] When i changes from n / 2 to n, the branch charge and discharge rate C i gradually increase;

[0024] The adjusted power P allocated to each branch i =C i * , where a is an integer between 1 and M, V ia is the terminal voltage of the ath battery in the ith branch, Vol ia is the remaining capacity of the ath battery in the i-th branch;

[0025] The adjusted power = .

[0026] Optionally, the output end of the energy storage system is connected to the grid via a DC / AC inverter, and the output end of the photovoltaic and / or wind energy system is also connected to the DC side of the DC / AC inverter.

[0027] Optionally, allocating the adjusted power to each branch is specifically:

[0028] Set the high charge and discharge rate A1, the nominal charge and discharge rate A2, and the low charge and discharge rate A3;

[0029] A1 is in the range of 1.2C-5C, A2 is in the range of 0.8C-1.2C, A1 is in the range of 0.1C-0.8C, and C is the current that can fully charge or discharge the battery in 1 hour;

[0030] When x belongs to the interval [1,i], the branch charge and discharge rate C x For high charge and discharge rate A1, the high discharge rate branch is allocated to the adjusted power HP x =C x * ;

[0031] When x belongs to the interval [i,j], the branch charge and discharge rate C x For low charge and discharge rate A3, the low discharge rate branch is allocated a divided adjustment power LP x =C x * ;

[0032] When x belongs to the interval [j,n], the branch charge and discharge rate C x The nominal charge and discharge rate A2, the nominal discharge rate branch distribution of the adjusted power NP x =C x * ;

[0033] Among them, 1 < i < j < n, x and j are integers, and V xa is the terminal voltage of the a-th battery in the x-th branch, in Vol xa is the remaining capacity of the a-th battery in the x-th branch;

[0034] The adjusted power = + .

[0035] Optionally, A1 > A2 > A3.

[0036] Optionally, 2(i - 1) < (j - i).

[0037] Optionally, 1.6(i - 1) < (n - j).

[0038] Beneficial technical effects:

[0039] In the first aspect, the branches with high charging rates of the container lithium battery pack are concentrated on one side, avoiding heat accumulation in the entire lithium battery pack. Therefore, the thermal safety of the container lithium battery pack is improved, and overheating, damage or power limitation of the lithium battery pack due to concentrated temperature rise are avoided.

[0040] In the second aspect, since the charging rate at the end of the lithium battery pack is high, it is convenient for the maintenance or replacement of the batteries at the end.

[0041] In the third aspect, due to the controlled differences in the charging rates of adjacent multiple branches, the charging currents of each branch are controlled, avoiding the charging current imbalance between branches caused by excessive charging current in some branches and too small charging current in some branches.

[0042] In the fourth aspect, through the division of high charge-discharge rate branches, nominal charge-discharge rate branches and low charge-discharge rate branches, the number of high charge-discharge rate branches is reduced, avoiding too many branches charging and discharging at a high rate simultaneously, and improving the overall life of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0044] Figure 1 is a schematic diagram of the lithium battery pack accessing the network in an embodiment of the present invention.

[0045] Figure 2 is a front view of the lithium battery pack in an embodiment of the present invention.

[0046] Figure 3Schematic diagram of the charging rate distribution of a lithium battery pack according to an embodiment of the present invention.

[0047] Figure 4 Schematic diagram of battery charge and discharge time and temperature rise according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0050] Example 1

[0051] like Figure 1 As shown, a lithium battery pack charge and discharge management method according to an embodiment of the present invention is applied to an energy storage system including a container lithium battery pack, and the output end of the energy storage system is connected to the power grid via a DC / AC inverter. Optionally, a photovoltaic or wind energy system is also included, and the output end of the photovoltaic or wind energy system is also connected to the DC side of the DC / AC inverter. Optionally, the lithium battery pack charge and discharge management method provided by an embodiment of the present invention is applied to an energy storage system that can obtain relevant parameters of power conversion equipment such as lithium battery packs and inverters, and also includes a controller that runs a preset control program and controls the operating status of the lithium battery pack. It can also be applied to other controllers in a power supply system composed of an energy storage system, a photovoltaic system, and an inverter. Of course, in some cases, it can also be applied to servers on the network side.

[0052] Optionally, the lithium battery pack includes i parallel branches, where i is a positive integer less than or equal to n, and n is the number of branches and is divisible by 4.

[0053] Optionally, each branch includes multiple batteries and DC / DC converters connected in series, and each branch is connected to the DC side of the DC / AC inverter through a DC / DC converter. In actual applications, the charging and discharging power thresholds corresponding to different states of the lithium battery pack are different, and the DC / DC converter also corresponds to its own power threshold. Therefore, during the charging and discharging process of the lithium battery pack, the actual charging and discharging power used cannot be greater than the above two thresholds.

[0054] like Figure 2-Figure 4 As shown, the i parallel branches of the container lithium battery pack are arranged from left to right or from right to left. The lithium battery packs are highly densely arranged, which easily leads to heat accumulation during the charging and discharging process, causing the temperature inside the container to rise significantly. The method of this embodiment includes:

[0055] When i is from 1 to n / 2, the branch charge and discharge rate C i gradually decrease;

[0056] When i changes from n / 2 to n, the branch charge and discharge rate C i Gradually increase.

[0057] exist Figure 3 The charge and discharge rates of branches 1-4 are: C1>C2>C3>C4, and the charge and discharge rates of branches 5-8 are: C5 <C6<C7<C8。

[0058] Through the above method and steps, the charge and discharge rates of the branches at both ends of the container lithium battery pack are higher than the charge and discharge rates of the middle branch. Since the air circulation at both ends is good, heat dissipation is facilitated and heat accumulation is not easily formed, thereby improving the thermal safety of the container lithium battery pack.

[0059] Example 2

[0060] This embodiment is an improvement on the first embodiment.

[0061] A lithium battery pack charge and discharge management method is applied to an energy storage system including a controller and a container lithium battery pack. The output end of the energy storage system is connected to the power grid via a DC / AC inverter. The output end of the photovoltaic and / or wind energy system is also connected to the DC side of the DC / AC inverter. The lithium battery pack includes i parallel branches, where i is a positive integer less than or equal to n, and n is the number of branches. Each branch includes M batteries connected in series and parallel, where M is a positive integer.

[0062] Optionally, n is divisible by 4.

[0063] Optionally, n is greater than 10.

[0064] Optionally, M is greater than or equal to 12.

[0065] The method comprises:

[0066] The controller obtains the total charge and discharge power of the lithium battery pack in the current control cycle and the operating power of the lithium battery pack of each branch in the previous control cycle;

[0067] The total charge and discharge power is the set power of the lithium battery pack in the current control cycle; the operating power of the lithium battery pack in the previous control cycle is the sum of the charge and discharge power of each branch in the previous control cycle;

[0068] The adjusted power is the set power minus the operating power;

[0069] Allocating the adjusted power to each of the branches. It can be understood that each of the branches is superimposed with the adjusted power allocated between the branches on the basis of the charge and discharge power of the previous control cycle to obtain the charge and discharge power of each branch in the current control cycle;

[0070] The controller controls the charging and discharging of the corresponding branch based on the charging and discharging power of the current control cycle of each branch;

[0071] The specific steps of allocating the adjusted power to each branch are as follows:

[0072] When i is from 1 to n / 2, the branch charge and discharge rate C i gradually decrease;

[0073] When i changes from n / 2 to n, the branch charge and discharge rate C i gradually increase;

[0074] The adjusted power P allocated to each branch i =C i * , where a is an integer between 1 and M, V ia is the terminal voltage of the ath battery in the ith branch, Vol ia is the remaining capacity of the ath battery in the i-th branch;

[0075] The adjusted power = .

[0076] Through the above method steps, on the one hand, the charge and discharge rate of the branch at the end of the container lithium battery pack is higher than the charge and discharge rate of the middle branch. Since the air circulation at both ends is good, heat dissipation is convenient and heat accumulation is not easy to form, thereby improving the thermal safety of the container lithium battery pack and avoiding overheating or damage or power limitation of the lithium battery pack due to concentrated temperature rise; on the other hand, since the charge rate at the end of the lithium battery pack is large, it is convenient to maintain or replace the battery at the end; on the third hand, since there is a controlled difference in the charge rate of adjacent branches, the charging current of each branch is controlled, thereby avoiding the charging current imbalance between branches caused by excessive charging current of some branches and excessive charging current of some branches.

[0077] Example 3

[0078] This embodiment is an improvement on the first or second embodiment.

[0079] A lithium battery pack charge and discharge management method is applied to an energy storage system including a controller and a container lithium battery pack. The output end of the energy storage system is connected to the DC side of a DC / AC inverter, the AC side of the DC / AC inverter is connected to the power grid, and the output end of a photovoltaic and / or wind energy system is connected to the DC side of the DC / AC inverter. The lithium battery pack includes i parallel branches, where i is a positive integer less than or equal to n, and n is the number of branches. Each branch includes M batteries connected in series and parallel, where M is a positive integer.

[0080] Optionally, the controller is arranged in a centralized control cabinet inside the container, or the controller is arranged in a control room.

[0081] Optionally, n is greater than 20.

[0082] Optionally, M is greater than or equal to 8.

[0083] The method comprises:

[0084] The controller obtains the total charge and discharge power of the lithium battery pack in the current control cycle and the operating power of the lithium battery pack of each branch in the previous control cycle;

[0085] The total charge and discharge power is the set power of the lithium battery pack in the current control cycle; the operating power of the lithium battery pack in the previous control cycle is the sum of the charge and discharge power of each branch in the previous control cycle;

[0086] The adjusted power is the set power minus the operating power;

[0087] Allocating the adjusted power to each of the branches. It can be understood that each of the branches is superimposed with the adjusted power allocated between the branches on the basis of the charge and discharge power of the previous control cycle to obtain the charge and discharge power of each branch in the current control cycle;

[0088] The controller controls the charging and discharging of the corresponding branch based on the charging and discharging power of the current control cycle of each branch;

[0089] The specific steps of allocating the adjusted power to each branch are as follows:

[0090] Set the high charge and discharge rate A1, the nominal charge and discharge rate A2, and the low charge and discharge rate A3;

[0091] Optionally, A1>A2>A3;

[0092] Optionally, A1 is in the range of 1.2C - 5C, A2 is in the range of 0.8C - 1.2C, A3 is in the range of 0.1C - 0.8C, and C is the current that can fully charge or discharge the battery in 1 hour;

[0093] When x belongs to the interval [1, i], the charge - discharge rate of the branch is C x For the high charge - discharge rate A1, the sub - adjustment power HP allocated to the high - discharge - rate branch x = C x * ;

[0094] When x belongs to the interval [i, j], the charge - discharge rate of the branch is C x For the low charge - discharge rate A3, the sub - adjustment power LP allocated to the low - discharge - rate branch x = C x * ;

[0095] When x belongs to the interval [j, n], the charge - discharge rate of the branch is C x For the nominal charge - discharge rate A2, the sub - adjustment power NP allocated to the nominal - discharge - rate branch x = C x * ;

[0096] Where 1 < i < j < n, x and j are integers, V xa is the terminal voltage of the a - th battery in the x - th branch, Vol xa is the remaining capacity of the a - th battery in the x - th branch;

[0097] The adjustment power = + .

[0098] Optionally, 2(i - 1) < (j - i).

[0099] Optionally, 3(i - 1) < (j - i).

[0100] Optionally, 4(i - 1) < (j - i).

[0101] Optionally, 1.2(i - 1) < (n - j).

[0102] Optionally, 1.4(i - 1) < (n - j).

[0103] Optionally, 1.6(i - 1) < (n - j).

[0104] Optionally, 1.8(i - 1) < (n - j).

[0105] Optionally, 2(i - 1) < (n - j).

[0106] Optionally, 3(i-1)<(nj).

[0107] Optional, i<0.05n.

[0108] Optional, i<0.1n.

[0109] Optional, i<0.12n.

[0110] Optional, i<0.14n.

[0111] Optional, i<0.16n.

[0112] Optional, i<0.17n.

[0113] Optional, i<0.18n.

[0114] Optional, i<0.19n.

[0115] Optional, i<0.2n.

[0116] Optional, i<0.25n.

[0117] Optional, i<0.3n.

[0118] Optional, i<0.4n.

[0119] Through the above method steps, on the one hand, the branches of the container lithium battery pack with high charging rate are concentrated on one side, avoiding heat accumulation of the entire lithium battery pack, thereby improving the thermal safety of the container lithium battery pack and avoiding overheating or damage or power limitation of the lithium battery pack due to concentrated temperature rise; on the second hand, since the charging rate at the end of the lithium battery pack is large, it is convenient to maintain or replace the battery at the end; on the third hand, since there are controlled differences in the charging rates of multiple adjacent branches, the charging current of each branch is controlled, avoiding the imbalance of charging current between branches caused by excessive charging current of some branches and excessive charging current of some branches; on the fourth hand, by dividing the high charge and discharge rate branch, the nominal charge and discharge rate branch and the low charge and discharge rate branch, the number of high charge and discharge rate branches is reduced, avoiding too many branches charging and discharging at a high rate at the same time, and improving the overall life of the battery pack.

[0120] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the composition and steps of each example according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0121] It should be noted that the serial numbers of the embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0122] The above are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, and the various embodiments or schemes can be arbitrarily combined, are also included in the patent protection scope of the present invention.

Claims

1. A lithium battery pack charge and discharge management method, applied to an energy storage system including a controller and a container lithium battery pack, wherein the lithium battery pack comprises n parallel branches, where n is a positive integer, and each branch comprises M batteries connected in series and parallel, where M is a positive integer; characterized in that: The method includes: the controller obtaining the total charge and discharge power of the lithium battery pack in the current control cycle and the operating power of the lithium battery pack of each branch in the previous control cycle; The total charge and discharge power is the set power of the lithium battery pack in the current control cycle; the operating power of the lithium battery pack in the previous control cycle is the sum of the charge and discharge power of each branch in the previous control cycle; The adjusted power is the set power minus the operating power; Allocating the adjusted power to each of the branches to obtain the charge and discharge power of each of the branches in the current control cycle; The controller controls the charging and discharging of the corresponding branch based on the charging and discharging power of the current control cycle of each branch; The specific steps of allocating the adjusted power to each branch are as follows: Set the high charge and discharge rate A1, the nominal charge and discharge rate A2, and the low charge and discharge rate A3; A1 is in the range of 1.2C-5C, A2 is in the range of 0.8C-1.2C, A3 is in the range of 0.1C-0.8C, and C is the current that can fully charge or discharge the battery in 1 hour; When branch x is between [1,i], the branch charge and discharge rate C x For high charge and discharge rate A1, the high discharge rate branch is allocated to the adjusted power HP x =C x * ; When branch x is between [i, j], the branch charge and discharge rate C x For low charge and discharge rate A3, the low discharge rate branch is allocated a divided adjustment power LP x =C x * ; When branch x is between [j,n], the branch charge and discharge rate C x The nominal charge and discharge rate A2, the nominal discharge rate branch distribution of the adjusted power NP x =C x * ; where 1 < i < j < n, x and j are integers, V xa is the terminal voltage of the a-th battery in the x-th branch, Vol xa is the remaining capacity of the a-th battery in the x-th branch; The adjusted power = + .

2. The lithium battery pack charge and discharge management method according to claim 1, wherein: The output end of the energy storage system is connected to the grid via a DC / AC inverter, and the output end of the photovoltaic and / or wind energy system is also connected to the DC side of the DC / AC inverter.

3. The lithium battery pack charge and discharge management method according to claim 1, wherein: A1>A2>A3.

4. The lithium battery pack charge and discharge management method according to claim 1, wherein: 2(i-1)<(ji).

5. The lithium battery pack charge and discharge management method according to claim 1, wherein: 1.6(i-1)<(nj).

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