Battery subsystem action priority determination method based on SOC and SOH

Abstract

The invention provides a battery subsystem action priority determination method based on SOC and SOH. The method comprises the following steps: acquiring SOC parameters and SOH parameters of a battery subsystem in an energy storage power station; determining SOC sorting indexes of the battery subsystems; determining SOH sorting indexes of the battery subsystems; the SOC sorting indexes and the SOH sorting indexes are subjected to normalization processing, comprehensive sorting indexes are determined based on the SOC sorting indexes and the SOH sorting indexes obtained after normalization processing, and the comprehensive sorting indexes are the action sequence of the battery subsystems from large to small; the action priority of the battery subsystem is comprehensively determined according to the SOC and SOH dimensions of the battery units in the battery subsystem, so that when the SOC of the electronic subsystem is equivalent, the battery subsystem with the high SOH can enter an action state, the action frequency of the battery subsystem with the low SOH is reduced, and the service life of the battery subsystem is prolonged. Therefore, the life decay speed of the battery units of the battery subsystem is delayed.

Description

Technical Field

[0001] The present invention relates to a method for determining battery action priority, and in particular to a method for determining battery subsystem action priority based on SOC and SOH. Background Art

[0002] In an energy storage power station, there are often multiple battery subsystems, which provide energy to the target load.

[0003] The target power of energy storage power stations fluctuates widely. Determining the action priority of battery subsystems at different control moments is key to achieving optimal battery subsystem action. In existing technologies, the action priority of battery subsystems in energy storage power stations is often based on the operating range of the SOC (State of Charge), essentially prioritizing actions based on the size of the charge and discharge margin. However, this approach ignores the impact of SOH (State of Health) on the battery, easily causing frequent action of battery subsystems composed of battery cells with different SOCs and SOHs, thereby accelerating the lifespan degradation of the battery cells.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for determining the action priority of a battery subsystem based on SOC and SOH, which comprehensively determines the action priority of the battery subsystem through the two dimensions of SOC and SOH of the battery cells in the battery subsystem, so that when the SOC of the electronic subsystem is equivalent, the battery subsystem with a high SOH can enter the action state, thereby reducing the action frequency of the battery subsystem with a low SOH, thereby delaying the life decay rate of the battery cells of the battery subsystem, and thus ensuring the operating stability and service life of the entire energy storage power station.

[0006] The present invention provides a method for determining the action priority of a battery subsystem based on SOC and SOH, comprising the following steps:

[0007] S1. Obtain the SOC and SOH parameters of the battery subsystem in the energy storage power station;

[0008] S2. Determine the SOC ranking index of the battery subsystem;

[0009] S3. Determine the SOH ranking index of the battery subsystem;

[0010] S4. Normalize the SOC ranking index and the SOH ranking index respectively, and determine a comprehensive ranking index based on the normalized SOC ranking index and SOH ranking index. The comprehensive ranking index is the operation order of the battery subsystem from large to small.

[0011] Further, step S4 specifically includes:

[0012] BPE i =f′ SOC,i +f′ SOH,i

[0013] Of which: BPE i represents the comprehensive ranking index of the i-th battery subsystem, f′ SOC,i represents the normalized SOC ranking index of the i-th battery subsystem; f′ SOH,i Represents the normalized SOH ranking index of the i-th battery subsystem.

[0014] Furthermore, the normalized SOC ranking index and the normalized SOH ranking index are determined by the following method:

[0015]

[0016] Where: f SOH,i represents the SOH ranking index of the i-th battery subsystem, f SOC,i Represents the SOC ranking index of the i-th battery subsystem.

[0017] Furthermore, the SOC ranking index f of the battery subsystem is determined by the following method: SOC,i :

[0018]

[0019] Among them: k1 and k2 are adjustment coefficients, k1 is used to adjust the SOC ranking index f SOC,i The size of k2 is used to adjust the SOC ranking index f SOC,i The growth rate of SOC is λ, which indicates the charge and discharge identifier. When λ=1, it indicates discharge, and when λ=-1, it indicates charge. μ,i Indicates the average SOC value of each battery cell in the i-th battery subsystem, SOC σ,i Indicates the SOC standard deviation of each battery cell in the i-th battery subsystem, SOC ref Indicates the set SOC reference value, SOC σ,b It represents the SOC standard deviation of the battery subsystem when the SOC of all battery cells in the i-th battery subsystem is at the upper and lower operating boundaries.

[0020] Furthermore, the SOH ranking index f of the battery subsystem is determined by the following method: SOH,i :

[0021]

[0022] R h =max(SOH σ,i )-min(SOH σ,i )

[0023] Where: k h is the adjustment coefficient, SOH μ,i represents the average SOH of each battery cell in the i-th battery subsystem, SOH σ,i Represents the SOC standard deviation of each battery cell in the i-th battery subsystem, SOH r Indicates the battery retirement SOH value.

[0024] Beneficial effects of the present invention: Through the present invention, the action priority of the battery subsystem is comprehensively determined by the two dimensions of SOC and SOH of the battery cells in the battery subsystem, so that when the SOC of the electronic subsystem is equivalent, the battery subsystem with a high SOH can enter the action state, thereby reducing the action frequency of the battery subsystem with a low SOH, thereby delaying the life attenuation rate of the battery cells of the battery subsystem, and thus ensuring the operating stability and service life of the entire energy storage power station. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0026] Figure 1 Flowchart of the present invention.

[0027] Figure 2 Schematic diagram of the topological structure of the energy storage power station of the present invention.

[0028] Figure 3 is the relationship between the battery subsystem fSOC,i and SOCμ,i and SOCμ,i.

[0029] Figure 4 fSOH,i curves under different Rh.

[0030] Figure 5 Comparison of battery cell output power under different priority sorting schemes.

[0031] Figure 6 Comparison of battery cell SOC under different priority sorting schemes.

[0032] Figure 7 Statistical comparison of battery subsystem priority ratios under different priority sorting schemes. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below:

[0034] like Figure 2 As shown in the figure, in an energy storage power station, an energy storage subsystem is composed of multiple battery units. Each battery unit is composed of a battery pack, a PCS (power storage converter, which is the abbreviation of the full English name Power Conversion System), and a BMS (battery management system, which is the abbreviation of the full English name Battery Management System). Each battery pack is composed of multiple battery cells connected in series and parallel. unit The battery subsystem is composed of battery cells that are boosted by a low-voltage transformer. sub Each battery subsystem is connected to a specific application scenario after secondary boosting by a high-voltage transformer. In an energy storage power station, the operation of each battery subsystem is relatively independent, so the power output of the energy storage power station is switched on and off in units of battery subsystems. At different control times t, P BES (t) is the total power instruction of the energy storage station, and the i-th battery subsystem is P i (t) Output power, the output power of the jth battery cell inside is P ij (t).

[0035] Therefore, the present invention provides a method for determining the action priority of a battery subsystem based on SOC and SOH, comprising the following steps:

[0036] S1. Obtain the SOC and SOH parameters of the battery subsystem in the energy storage power station;

[0037] S2. Determine the SOC ranking index of the battery subsystem;

[0038] S3. Determine the SOH ranking index of the battery subsystem;

[0039] S4. Normalize the SOC ranking index and the SOH ranking index respectively, and determine the comprehensive ranking index based on the normalized SOC ranking index and SOH ranking index. The comprehensive ranking index is the action order of the battery subsystem from large to small. Through the above method, the action priority of the battery subsystem is comprehensively determined by the two dimensions of SOC and SOH of the battery cells in the battery subsystem, so that when the SOC of the electronic subsystem is equivalent, the battery subsystem with a high SOH can enter the action state, thereby reducing the action frequency of the battery subsystem with a low SOH, thereby delaying the life decay rate of the battery cells of the battery subsystem, and thus ensuring the operation stability and service life of the entire energy storage power station.

[0040] In this embodiment, step S4 specifically includes:

[0041] BPE i =f′ SOC,i +f′ SOH,i

[0042] Of which: BPE i represents the comprehensive ranking index of the i-th battery subsystem, f′ SOC,i represents the normalized SOC ranking index of the i-th battery subsystem; f′ SOH,i Represents the normalized SOH ranking index of the i-th battery subsystem, that is: BPE i The larger the value, the higher the action priority of the battery subsystem.

[0043] Specifically, the normalized SOC ranking index and the normalized SOH ranking index are determined by the following method:

[0044]

[0045] Where: f SOH,i represents the SOH ranking index of the i-th battery subsystem, f SOC,i It represents the SOC ranking index of the i-th battery subsystem. Max and min refer to the maximum and minimum values ​​of SOC and SOH in all battery subsystems for normalization.

[0046] The SOC ranking index f of the battery subsystem is determined by the following method SOC,i :

[0047]

[0048] Among them: k1 and k2 are adjustment coefficients, k1 is used to adjust the SOC ranking index f SOC,i The size of k2 is used to adjust the SOC ranking index f SOC,i The growth rate of SOC is λ, which indicates the charge and discharge identifier. When λ=1, it indicates discharge, and when λ=-1, it indicates charge. μ,i Indicates the average SOC value of each battery cell in the i-th battery subsystem, SOC σ,i Indicates the SOC standard deviation of each battery cell in the i-th battery subsystem, SOC ref Indicates the set SOC reference value, which is generally set to 0.5; SOC σ,b It represents the SOC standard deviation of the battery subsystem when the SOC of all battery cells of the i-th battery subsystem is at the upper and lower operating boundaries. The average value represents the overall SOC level of the battery subsystem, and the standard deviation represents the SOC balance of the battery subsystem, as shown in Figure 3 As shown in Figure 2, the higher the function value, the higher the SOC priority ranking.SOC,i It's about SOC μ,i , SOC σ,i The binary function of f shows a monotonic change characteristic. When the charge and discharge margin of the battery subsystem is larger and the balance degree is higher, f SOC,i The larger the value of .

[0049] In this embodiment, the SOH ranking index f of the battery subsystem is determined by the following method: SOH,i :

[0050]

[0051] R h =max(SOH σ,i )-min(SOH σ,i )

[0052] Where: k h is the adjustment coefficient, SOH μ,i represents the average SOH of each battery cell in the i-th battery subsystem, SOH σ,i Represents the SOC standard deviation of each battery cell in the i-th battery subsystem, SOH r Represents the battery retirement SOH value. The average value represents the overall SOH level of the battery subsystem, and the standard deviation represents the SOH balance of the battery subsystem. Figure 4 As shown: f SOH,i The function range is [SOH r ,SOH r +k h SOH σ,i / R h ) interval. f SOH,i It tends to +∞ at the right boundary. When the health state of the battery subsystem is close to retirement, that is, SOH μ,i Approaching SOH r When f SOH,i As the function value approaches 0, the SOH sorting priority is greatly reduced.

[0053] SOH r and k h is a known value, so f SOH,i The boundary range depends on R h and SOH σ,i .f SOH,i, Value increases with SOH μ,i Increase or SOH σ,i It increases monotonically with the decrease of , indicating that the battery subsystem with higher overall SOH and smaller difference has a higher SOH priority ranking.

[0054] When R hWhen it is larger, it means that the SOH standard deviation of each battery subsystem in the energy storage power station is quite different. SOH,i The value of SOH is mainly affected by σ,i The focus is on selecting a battery subsystem with better SOH balance. h The smaller it is, the smaller the SOH balance of each battery subsystem is. μ,i The height of f SOH,i The main influencing factors are more focused on giving priority to battery subsystems with higher overall SOH.

[0055] The following is a specific example to further illustrate:

[0056] The battery subsystem SOC balancing time, the number of battery cell charge / discharge conversions (CDC), and the battery subsystem sorting priority ratio are used as evaluation indicators for the implementation effect of the action priority sorting method.

[0057] The battery subsystem SOC balancing time is expressed as the SOC standard deviation of the battery cells in the battery subsystem from the initial value to the balancing threshold. Time required.

[0058] The battery cell CDC times are expressed as

[0059]

[0060] Where: T is the total operating cycle; CDCij represents the number of charge and discharge conversions of the #ij battery cell within the total operating cycle T; is the charge and discharge state switching identifier of the battery cell at time t. When the power sign at time t is opposite to that at time t-1, that is, the charge and discharge state of the battery has been switched, It is recorded as 1, otherwise it is recorded as 0.

[0061] The battery subsystem priority ranges from 0, 1, 2, ..., nsub. When nsub is selected, it indicates the lowest priority; 1 indicates the highest priority; and 0 indicates the battery subsystem is in standby mode.

[0062] In this embodiment Figure 5 、 Figure 6 , Table 1 and Figure 7 The comparison of battery cell output power, battery cell SOC, battery subsystem CDC times and battery subsystem priority ratio under different priority sorting schemes are shown. Among them, scheme 1 is based on the SOC sorting function f SOC,i As the basis for the priority sorting of the battery subsystem, Scheme 2 is the present invention based on BPE i (Also considering f SOC,i and f SOH,i) as the basis for battery subsystem priority sorting. Combined Figure 5 It can be seen that under different priority sorting schemes, the power output curve of battery subsystem #2, which is in the middle of the health state, has little difference, and the power curves of battery subsystems #1 and #3 show significant differences. Under sorting scheme 2 of the present invention that comprehensively considers the battery SOC and SOH operating status, the #1 battery subsystem is in a higher SOH action priority for a long time, making its power output more frequent. The #3 battery subsystem is often in standby mode due to its low SOH status. The SOH status of the #2 battery subsystem is in the middle of the three, so its power output curve does not show obvious changes. Combined with Figure 6 It can be seen that under Scheme 2 of the present invention, the balancing time of the #1 and #2 battery subsystems is reduced compared to Scheme 1, and the balancing time of the #3 battery subsystem is significantly extended. This is the result of the protection of the #3 battery subsystem with low SOH by the sorting method of Scheme 2. By making the #3 battery subsystem in standby state for a longer time, its action frequency is reduced to avoid aggravated aging. Combined with Table 1, it can be seen that the CDC times of the #1 and #2 battery subsystems in Scheme 1 are similar, and #3 is the highest. This is because Scheme 1 only uses the SOC of the battery subsystem as the sorting basis, resulting in frequent action of the #3 battery subsystem with better SOC but worse SOH, aggravating the SOH imbalance between the battery subsystems, which is not conducive to the long-term operation of the energy storage power station. In contrast, the CDC times of the #1 battery subsystem in Scheme 2 of the present invention is the highest among the three battery subsystems, while the CDC times of the #3 battery subsystem are the lowest. This shows that the battery subsystem action priority sorting principle designed by the present invention can fully consider the differences in SOC and SOH operating states between subsystems, and tends to make the #1 battery subsystem with good SOH state take on more frequent power output tasks, while reducing the frequency of use of the #3 battery subsystem with low SOH, thereby avoiding its aging. Figure 7 It can be seen that the action priority ratios of each battery subsystem under the two sorting schemes show a large difference. Since the #2 battery subsystem is in an intermediate state among the three groups of battery subsystems in terms of both SOC and SOH status, the action time under the two schemes is basically the same. However, there is a significant difference between the #1 and #3 battery subsystems. Under Scheme 2, the sorting method takes into account the SOC and SOH of the battery subsystems at the same time. Since the overall state of the #1 battery subsystem is better than that of the #3 battery subsystem, its action time ratio increases to 84.2%. Correspondingly, the standby time of the #3 battery subsystem increases from 22.4% under Scheme 1 to 79.7%. This shows that the proposed sorting scheme can protect battery subsystems with a poor SOH status and avoid their frequent actions.

[0063] Table 1: Comparison of battery subsystem CDC times under different priority sorting schemes

[0064]

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. 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 purpose 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 determining battery subsystem action priority based on SOC and SOH, characterized by: The following steps are involved: S1. Obtain the SOC and SOH parameters of the battery subsystem in the energy storage power station; S2. Determine the SOC ranking index of the battery subsystem; S3. Determine the SOH ranking index of the battery subsystem; S4. Normalize the SOC ranking index and the SOH ranking index respectively, and determine a comprehensive ranking index based on the normalized SOC ranking index and SOH ranking index. The comprehensive ranking index is the operation order of the battery subsystem from large to small.

2. The method for determining battery subsystem action priority based on SOC and SOH according to claim 1, characterized in that: Step S4 specifically includes: BPE i =f′ SOC,i +f′ SOH,i Of which: BPE i represents the comprehensive ranking index of the i-th battery subsystem, f′ SOC,i represents the normalized SOC ranking index of the i-th battery subsystem; f′ SOH,i Represents the normalized SOH ranking index of the i-th battery subsystem.

3. The method for determining battery subsystem action priority based on SOC and SOH according to claim 2, characterized in that: The normalized SOC ranking index and the normalized SOH ranking index are determined by the following method: Where: f SOH,i represents the SOH ranking index of the i-th battery subsystem, f SOC,i Represents the SOC ranking index of the i-th battery subsystem.

4. The method for determining battery subsystem action priority based on SOC and SOH according to claim 3, characterized in that: The SOC ranking index f of the battery subsystem is determined by the following method SOC,i : Among them: k1 and k2 are adjustment coefficients, k1 is used to adjust the SOC ranking index f SOC,i The size of k2 is used to adjust the SOC ranking index f SOC,i The growth rate of SOC is λ, which indicates the charge and discharge identifier. When λ=1, it indicates discharge, and when λ=-1, it indicates charge. μ,i Indicates the average SOC value of each battery cell in the i-th battery subsystem, SOC σ,i Indicates the SOC standard deviation of each battery cell in the i-th battery subsystem, SOC ref Indicates the set SOC reference value, SOC σ,b It represents the SOC standard deviation of the battery subsystem when the SOC of all battery cells of the i-th battery subsystem is at the upper and lower operating boundaries.

5. The method for determining battery subsystem action priority based on SOC and SOH according to claim 3, characterized in that: The SOH ranking index f of the battery subsystem is determined by the following method SOH,i : R h =max(SOH σ,i )-min(SOH σ,i ) Where: k h is the adjustment coefficient, SOH μ,i represents the average SOH of each battery cell in the i-th battery subsystem, SOH σ,i Represents the SOC standard deviation of each battery cell in the i-th battery subsystem, SOH r Indicates the battery retirement SOH value.

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