Battery subsystem action number determination method considering target power and SOC balance

Abstract

The invention provides a battery subsystem action number determination method considering target power and SOC balance, and the method comprises the steps: S1, determining the action priority of each battery subsystem in an energy storage power station, and sorting the action priorities from high to low; s2, determining a power dynamic threshold value of the energy storage power station, determining target power, judging whether the target power is greater than or equal to the power dynamic threshold value or not, if so, enabling the energy storage power station to be in a high-power working condition, and controlling all battery subsystems with SOC smaller than an SOC threshold value in the energy storage power station to operate at rated power, and if not, enabling the energy storage power station to be in a constant-power working condition, and entering the step S3; and S3, determining the initial number of actions of the battery subsystems based on the target power, determining a correction coefficient of the number of actions of the battery subsystems based on the SOC balance degree, and taking the sum of the initial number and the correction coefficient as the final number of actions of the battery subsystems under the constant power working condition. And finding out the battery subsystem actions with the maximum priority and the final action quantity in the action priority sequence.

Description

Technical Field

[0001] The present invention relates to a method for determining the number of battery subsystem actions in an energy storage power station, and in particular to a method for determining the number of battery subsystem actions that takes into account both target power and SOC balance. Background Art

[0002] Energy storage power stations often have multiple battery subsystems that provide energy to the target load. Determining the number of active battery subsystems is crucial for ensuring the energy storage station follows the target power. It also prevents frequent switching between charge and discharge states caused by all battery subsystems being active.

[0003] In existing technology, the number of battery subsystem actions typically determined based on matching the target power of the energy storage station is often determined. This ignores the impact of the SOC balance of each battery cell within the battery subsystem on the power output capacity of the energy storage station. If the battery subsystem selected for action has poor SOC balance among the battery cells, meaning that some battery cells have a small charge / discharge margin, this can lead to overcharging and overdischarging of the battery cells, making them unable to absorb the total target power of the energy storage station. This can also accelerate the degradation of the battery cell lifespan.

[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 number of battery subsystem actions that takes into account both target power and SOC balance. The method adjusts the number of battery subsystem actions based on the SOC balance of the battery subsystem. This can effectively avoid frequent switching of charge and discharge states of battery cells in some battery subsystems while meeting the total target power consumption of the energy storage power station, shorten the SOC balance time of the battery subsystem, and ensure the service life of the battery cells.

[0006] The present invention provides a method for determining the number of battery subsystem actions that takes into account both target power and SOC balance, comprising the following steps:

[0007] S1. Determine the action priority of each battery subsystem in the energy storage power station and sort the action priorities from high to low;

[0008] S2. Determine the dynamic power threshold of the energy storage station and determine the target power. Determine whether the target power is greater than or equal to the dynamic power threshold. If so, the energy storage station is in a high-power operating condition and controls all battery subsystems in the energy storage station whose SOC is less than the SOC threshold to operate at rated power. If not, the energy storage station is in a normal power operating condition and proceeds to step S3.

[0009] S3. Determine the initial number of battery subsystem actions based on the target power, and determine the correction coefficient of the number of battery subsystem actions based on the SOC balance. The sum of the initial number and the correction coefficient is used as the final number of battery subsystem actions under constant power conditions, and find the battery subsystem action with the highest final number of actions in the action priority sequence.

[0010] Furthermore, step S1 further includes:

[0011] Assign values ​​to the sorted battery subsystems. When the value is 0, it means the battery subsystem is in standby mode. When the value is 1, it means the battery subsystem has the highest action priority. The values ​​are assigned as natural numbers and increase in sequence. The battery subsystem with the lowest action priority is assigned as n. sub .

[0012] Furthermore, determining the power dynamic threshold of the energy storage power station specifically includes:

[0013]

[0014] Where: P n Indicates the rated power of a single battery cell in the battery subsystem, SOC ij (t) represents the state of charge of the jth battery cell in the i-th battery subsystem at time t, SOC max , SOC min are the upper and lower limits of the battery cell SOC operating range respectively; n unit Indicates the number of battery cells in the battery subsystem, n o The number of battery cells with SOC exceeding the limit.

[0015] Furthermore, determining the initial number of battery subsystem actions based on the target power specifically includes:

[0016] Where: m represents the initial number of battery subsystem actions, P n Indicates the rated power of a single battery cell in the battery subsystem, P BES (t) represents the target power of the energy storage power station at time t, Represents the ceiling operator.

[0017] Furthermore, in step S3, the correction coefficient for determining the number of battery subsystem actions based on the SOC balance degree specifically includes:

[0018]

[0019] 0≤p≤n sub -m

[0020] Where: p represents the correction coefficient, SOC balance threshold of battery subsystem, SOC σ,i Represents the SOC standard deviation of each battery cell in the i-th battery subsystem.

[0021] Beneficial effects of the present invention: Through the present invention, the number of actions of the battery subsystem is adjusted based on the SOC balance of the battery subsystem, so that under the premise of meeting the total target power consumption of the energy storage power station, the battery cells in some battery subsystems can be effectively avoided from frequently switching the charge and discharge states, the SOC balance time of the battery subsystem can be shortened, and the service life of the battery cells can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 It is a schematic diagram of the process of the present invention.

[0024] Figure 2 Schematic diagram of the topological structure of the energy storage power station of the present invention.

[0025] Figure 3 A comparison chart of battery unit output power under different battery subsystem action quantity determination schemes.

[0026] Figure 4 A comparison chart of battery cell SOC under different battery subsystem action quantity determination schemes. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below:

[0028] 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 Each battery cell is boosted by a low-voltage transformer to form a battery subsystem. A certain number of battery subsystems are then boosted by a high-voltage transformer to connect to specific application scenarios. In an energy storage power station, each battery subsystem operates relatively independently, so the power output of the energy storage station is switched on and off per battery subsystem.

[0029] The present invention provides a method for determining the number of battery subsystem actions that takes into account both target power and SOC balance, comprising the following steps:

[0030] S1. Determine the action priority of each battery subsystem in the energy storage power station and sort the action priorities from high to low;

[0031] S2. Determine the dynamic power threshold of the energy storage station and determine the target power. Determine whether the target power is greater than or equal to the dynamic power threshold. If so, the energy storage station is in a high-power operating condition and controls all battery subsystems in the energy storage station whose SOC is less than the SOC threshold to operate at rated power. If not, the energy storage station is in a normal power operating condition and proceeds to step S3.

[0032] S3. Determine the initial number of battery subsystem actions based on the target power, and determine the correction coefficient for the number of battery subsystem actions based on the SOC balance. The sum of the initial number and the correction coefficient is used as the final number of battery subsystem actions under constant power conditions, and find the battery subsystem action with the highest priority in the action priority sequence. Through the above method, the number of battery subsystem actions is adjusted based on the SOC balance of the battery subsystem. This can effectively avoid frequent switching of charge and discharge states of battery cells in some battery subsystems while meeting the total target power consumption of the energy storage power station, shorten the SOC balance time of the battery subsystem, and ensure the service life of the battery cells.

[0033] The action priority of each battery subsystem in the energy storage power station can be determined as follows:

[0034] Determine the SOC ranking index f of the battery subsystem SOC,i :

[0035]

[0036] 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 The standard deviation of the SOC of the battery subsystem i when the SOC of all battery cells is within 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.

[0037] Determine the SOH ranking index f of the battery subsystemSOH,i :

[0038]

[0039] R h =max(SOH σ,i )-min(SOH σ,i )

[0040] Where: k h is the adjustment coefficient, SOH μ,i It 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's retired 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.

[0041] Normalize the SOC ranking index and SOH ranking index separately:

[0042]

[0043] 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.

[0044] The comprehensive ranking index is determined 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. The comprehensive ranking index is specifically:

[0045] BPE i =f′ SOC,i +f′ SOH,i

[0046] 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.

[0047] Of course, the action priority of the battery subsystem may also be determined using other existing methods, which will not be elaborated here.

[0048] In this embodiment, step S1 further includes:

[0049] Assign values ​​to the sorted battery subsystems. When the value is 0, it means the battery subsystem is in standby mode. When the value is 1, it means the battery subsystem has the highest action priority. The values ​​are assigned as natural numbers and increase in sequence. The battery subsystem with the lowest action priority is assigned as n. sub .

[0050] Determining the dynamic power threshold of the energy storage power station specifically includes:

[0051]

[0052] Where: P n Indicates the rated power of a single battery cell in the battery subsystem, SOC ij (t) represents the state of charge of the jth battery cell in the i-th battery subsystem at time t, SOC max , SOC min are the upper and lower limits of the battery cell SOC operating range respectively; n unit Indicates the number of battery cells in the battery subsystem, n o The number of battery cells with SOC exceeding the limit.

[0053] At time t, the target power of the energy storage station P BES The value of (t) is related to P lim (t) to determine its target power scale. The judgment method is

[0054]

[0055] Determining the initial number of battery subsystem actions based on the target power specifically includes:

[0056] Where: m represents the initial number of battery subsystem actions, P n Indicates the rated power of a single battery cell in the battery subsystem, P BES (t) represents the target power of the energy storage power station at time t, Represents the ceiling operator.

[0057] During the operation of an energy storage power station, the SOC of each battery cell in some battery subsystems varies greatly. To avoid the battery cell SOC approaching the limit range when facing continuous, high-amplitude, and same-direction power commands, which aggravates battery aging, the balance of the internal battery cell SOC should also be considered when determining the number of active battery subsystems.

[0058] Therefore, in step S3, the correction coefficient for determining the number of battery subsystem actions based on the SOC balance degree specifically includes:

[0059]

[0060] 0≤p≤n sub -m

[0061] Where: p represents the correction coefficient, SOC balance threshold of battery subsystem, SOC σ,i Represents the SOC standard deviation of each battery cell in the i-th battery subsystem. The standard deviation is used to reflect the balance of SOC.

[0062] The corrected number of battery subsystem actions m′ is

[0063] m′=m+p;

[0064] Therefore, under normal power conditions, the top m′ battery subsystems with the highest priority are selected to participate in the target system, such as wind power fluctuation smoothing.

[0065] The following further illustrates with examples:

[0066] The battery subsystem SOC balancing time and the number of battery cell charge / discharge conversions (CDC) are set as evaluation indicators for the implementation effect of the battery subsystem action quantity determination method.

[0067] 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.

[0068] The battery cell CDC times are expressed as

[0069]

[0070] Where: T is the total operating cycle; CDCij represents the number of charge and discharge conversions of the jth battery cell of the first battery subsystem 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.

[0071] Figure 3 、 Figure 4Tables 1 and 2 show comparisons of battery cell output power, battery cell SOC, and battery subsystem CDC times under different battery subsystem action number determination schemes. Scheme 1 determines the number of battery subsystem actions based solely on the multiple of the energy storage station's target power and the battery subsystem's rated power, without making any corrections or adjustments to the number of actions. Scheme 2, the present invention's method for determining the number of battery subsystem actions, balances target power scale with SOC.

[0072] In this embodiment Figure 3 This figure compares the output power of battery cells under different scenarios for determining the number of battery subsystem activations. Compared to Scheme 1, Scheme 2 of the present invention shows more frequent power output from battery subsystems #2 and #3, while the operation of battery subsystem #1 is not significantly affected by the adjustment of the number of battery subsystem activations. This is because, under the modified adjustment method of the present invention, battery subsystems #2 and #3 often serve as additional battery subsystems to assist #1 in achieving target power.

[0073] In this embodiment Figure 4 The SOC of battery cells is compared under different schemes for determining the number of battery subsystem actions. Compared with Scheme 1, the SOC balancing time of the three battery subsystems is significantly reduced under Scheme 2 of the present invention. In the early stage of system operation, the internal SOC balance of all battery subsystems is poor. Under the effect of the battery subsystem action number correction coefficient p, it is basically necessary to add an action battery subsystem, so the balancing time required for each battery subsystem becomes shorter. As the SOC balance degree increases, the regulatory effect of adding the number of battery subsystem actions gradually weakens. This reflects the dynamic adjustment characteristics of the proposed battery subsystem action number based on the SOC balance degree.

[0074] Table 1 in this embodiment compares the number of CDCs performed by the battery subsystem under different battery subsystem action quantity determination schemes. Compared to Scheme 1, Scheme 2 of the present invention increases the number of CDCs performed by battery subsystems #1 and #3, while the number of CDCs performed by #2 decreases. Based on the relationship between the SOC balance of the battery subsystem and the quantity adjustment method, when the SOC of the battery subsystem is at a low balance, the battery subsystem action quantity correction adjustment method increases the SOC balancing speed by adding an auxiliary battery subsystem. When the subsystem SOC balance reaches a threshold, the increase in the number of actions is automatically stopped. Therefore, the SOC balance of the battery subsystem and the correction adjustment method for the number of actions are mutually beneficial.

[0075]

[0076] Table 1 Comparison of battery subsystem CDC times under different battery subsystem action number determination schemes

[0077] 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 the number of battery subsystem actions that takes into account both target power and SOC balance, characterized by: The following steps are involved: S1. Determine the action priority of each battery subsystem in the energy storage power station and sort the action priorities from high to low; S2. Determine the dynamic power threshold of the energy storage station and determine the target power. Determine whether the target power is greater than or equal to the dynamic power threshold. If so, the energy storage station is in a high-power operating condition and controls all battery subsystems in the energy storage station whose SOC is less than the SOC threshold to operate at rated power. If not, the energy storage station is in a normal power operating condition and proceeds to step S3. S3. Determine the initial number of battery subsystem actions based on the target power, and determine the correction coefficient of the number of battery subsystem actions based on the SOC balance. The sum of the initial number and the correction coefficient is used as the final number of battery subsystem actions under constant power conditions, and find the battery subsystem action with the highest final number of actions in the action priority sequence.

2. The method for determining the number of battery subsystem actions that takes into account both target power and SOC balance according to claim 1, characterized in that: Step S1 also includes: Assign values ​​to the sorted battery subsystems. When the value is 0, it means the battery subsystem is in standby mode. When the value is 1, it means the battery subsystem has the highest action priority. The values ​​are assigned as natural numbers and increase in sequence. The battery subsystem with the lowest action priority is assigned as n. sub .

3. The method for determining the number of battery subsystem actions that takes into account both target power and SOC balance according to claim 2, characterized in that: Determining the dynamic power threshold of the energy storage power station specifically includes: Where: P n Indicates the rated power of a single battery cell in the battery subsystem, SOC ij (t) represents the state of charge of the jth battery cell in the i-th battery subsystem at time t, SOC max , SOC min are the upper and lower limits of the battery cell SOC operating range respectively; n unit Indicates the number of battery cells in the battery subsystem, n o The number of battery cells with SOC exceeding the limit.

4. The method for determining the number of battery subsystem actions that takes into account both target power and SOC balance according to claim 1, characterized in that: Determining the initial number of battery subsystem actions based on the target power specifically includes: Where: m represents the initial number of battery subsystem actions, P n Indicates the rated power of a single battery cell in the battery subsystem, P BES (t) represents the target power of the energy storage power station at time t, Represents the ceiling operator.

5. The method for determining the number of battery subsystem actions that takes into account both target power and SOC balance according to claim 4, characterized in that: In step S3, the correction coefficient for determining the number of battery subsystem actions based on the SOC balance degree specifically includes: 0≤p≤n sub -m Where: p represents the correction coefficient, SOC balance threshold of battery subsystem, SOC σ,i Represents the SOC standard deviation of each battery cell in the i-th battery subsystem.

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