Power daisy chain based dual-mode adaptive balancing method for parallel battery packs

Abstract

The application provides a parallel battery pack dual-mode adaptive equalization method based on a power daisy chain. The equalization method is applied to an equalization circuit, the equalization circuit comprises an equalization branch and N battery branches, the equalization branch is connected with the battery branches, the N battery branches are connected in parallel, and N is an integer greater than 1. The equalization method comprises the following steps: acquiring the charging and discharging direction, the total current value, the real-time current value of each battery branch and the real-time SOC value of each battery branch, and calculating the average current value and the average SOC value; determining the current difference compensation value of each battery branch according to the charging and discharging direction, the average current value and the real-time current value, determining the SOC difference compensation value of each battery branch according to the charging and discharging direction, the average SOC value and the real-time SOC value; based on the current difference compensation value and the SOC difference compensation value, the total compensation value of each battery branch is calculated; and based on the total compensation value of each battery branch, the equalization branch is controlled to work, so as to equalize the working current of the N battery branches and improve the stability of the working of each battery pack.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain. Background Technology

[0002] In energy storage products, due to cost and space constraints, inverter main units usually do not have batteries or are only equipped with small-capacity battery packs, relying on external battery packs for capacity expansion, and often using daisy-chain connections to reduce costs.

[0003] However, in a daisy-chain connection, the distances from each parallel battery pack to the inverter differ, and the DC resistances of each parallel battery pack vary, resulting in uneven charging and discharging currents. This leads to several problems. First, the charging and discharging rates of each battery pack are inconsistent, resulting in different rates of State of Charge (SOC) decline and inconsistent SOCs across multiple parallel battery packs, impacting customer experience. Second, when each battery pack discharges, the pack closest to the load discharges first, causing the discharge current of the remaining packs to continuously increase, potentially exceeding the maximum discharge current and triggering protection. Simultaneously, the high current causes severe overheating of the wiring, posing a safety hazard. Third, due to the different SOCs of each battery pack, circulating currents are generated when the load stops discharging, threatening the stable operation of the system. Summary of the Invention

[0004] This application provides a dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain, which can balance the operating current of multiple battery packs connected by the daisy chain to improve the stability of each battery pack.

[0005] This application provides a dual-modal adaptive equalization method for parallel battery packs based on a power daisy chain. The dual-modal adaptive equalization method for parallel battery packs based on a power daisy chain is applied to an equalization circuit. The equalization circuit includes an equalization branch and N battery branches. The equalization branch is connected to the battery branches. The N battery branches are connected in parallel, and N is an integer greater than 1.

[0006] The dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain includes: acquiring the charging / discharging direction, total current value, real-time current value of each battery branch, and real-time SOC value of each battery branch, and calculating the average current value and average SOC value; determining the current difference compensation value for each battery branch based on the charging / discharging direction, the average current value, and the real-time current value; determining the SOC difference compensation value for each battery branch based on the charging / discharging direction, the average SOC value, and the real-time SOC value; calculating the total compensation value for each battery branch based on the current difference compensation value and the SOC difference compensation value; and controlling the balancing branch to operate based on the total compensation value for each battery branch to balance the operating current of the N battery branches.

[0007] In some embodiments, determining the current difference compensation value for each battery branch based on the charging / discharging direction, the average current value, and the real-time current value includes: when discharging, if the real-time current value of a battery branch is less than the average current value, then determining the difference between the average current value and the real-time current value as the current difference compensation value for that battery branch; when charging, if the real-time current value of a battery branch is less than the average current value, then determining the difference between the average current value and the real-time current value as the current difference compensation value for that battery branch.

[0008] In some embodiments, determining the SOC difference compensation value for each battery branch based on the charging / discharging direction, the average SOC value, and the real-time SOC value includes: when discharging, if the real-time SOC value of a battery branch is greater than the average SOC value, then calculating the SOC difference compensation value for the battery branch based on the difference between the real-time SOC value and the average SOC value; when charging, if the real-time SOC value of a battery branch is less than the average SOC value, then calculating the SOC difference compensation value for the battery branch based on the difference between the average SOC value and the real-time SOC value.

[0009] In some embodiments, calculating the total compensation value for each battery branch based on the current difference compensation value and the SOC difference compensation value includes: calculating the SOC difference value for each battery branch based on the average SOC value and the real-time SOC value; determining a first weighting coefficient and a second weighting coefficient based on the SOC difference value for each battery branch; and calculating the total compensation value by combining the current difference compensation value, the first weighting coefficient, the SOC difference compensation value, and the second weighting coefficient.

[0010] In some embodiments, calculating the total compensation value by combining the current difference compensation value, the first weighting coefficient, the SOC difference compensation value, and the second weighting coefficient includes: adding the product of the current difference compensation value and the first weighting coefficient to the product of the SOC difference compensation value and the second weighting coefficient, and the sum is the total compensation value.

[0011] In some embodiments, controlling the balancing branch to operate based on the total compensation value of each of the battery branches to balance the operating current of the N battery branches includes: sorting the total compensation values ​​of the battery branches to determine a compensation order; determining a target battery branch according to the compensation order; determining a control period for the target battery branch based on the SOC difference value of the target battery branch; and controlling the balancing branch to operate based on the control period and the total compensation value to compensate the operating current of the target battery branch.

[0012] In some embodiments, determining the control cycle of the target battery branch based on the SOC difference value of the target battery branch includes: using a first control cycle when the SOC difference value is greater than a first difference threshold; using a second control cycle when the SOC difference value is between a second difference threshold and the first difference threshold; and using a third control cycle when the SOC difference value is less than the second difference threshold; wherein the first difference threshold is greater than the second difference threshold; and in terms of time, the first control cycle is greater than the second control cycle, and the second control cycle is greater than the third control cycle.

[0013] In some embodiments, the formula for calculating the SOC difference compensation value is: ΔIs = ΔS × Q nom / T c Wherein, ΔIs is the SOC difference compensation value, in A; ΔS is the SOC difference value, in %; Q nom The nominal capacity of the battery is expressed in Ah; T c To compensate for the time variable, the unit is hours (h).

[0014] In some embodiments, the dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain further includes: when charging, the compensation time variable is less than the total remaining charging time; when discharging, the compensation time variable is less than the total remaining discharging time.

[0015] In some embodiments, both the total remaining charging time and the total remaining discharging time are determined based on the desired time and the hardware lower limit time.

[0016] Unlike existing technologies, this application provides a dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain. This application first obtains the charging / discharging direction, total current value, and real-time current and SOC values ​​of each battery branch, then calculates the average current and average SOC values. Subsequently, based on the charging / discharging conditions, it calculates the current difference compensation value and SOC difference compensation value for each battery branch, clarifying the difference between the current and capacity of each battery branch and the average value. The two types of compensation values ​​are then combined to obtain the total compensation value. Finally, the balancing branch is controlled based on the total compensation value, adjusting the current of each battery branch to make the operating current of each battery branch more consistent, thus achieving current balance. This application considers both current and SOC state, solving problems such as inconsistent charging / discharging rates and premature depletion caused by uneven current. Furthermore, the balancing branch only needs to handle the current difference between each battery branch (usually a small portion of the total current), rather than the large current of the main circuit. Therefore, the rated power of DC-DC modules and switching elements can be significantly reduced, allowing for the selection of smaller, lower-cost devices. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a flowchart illustrating the dual-modal adaptive equalization method for parallel battery packs based on a power daisy chain provided in this application embodiment;

[0019] Figure 2 This is a schematic diagram of the specific process of step S3 in the dual-modal adaptive equalization method for parallel battery packs based on a power daisy chain provided in the embodiments of this application;

[0020] Figure 3 This is a schematic diagram of the specific process of step S4 in the dual-modal adaptive equalization method for parallel battery packs based on a power daisy chain provided in the embodiments of this application;

[0021] Figure 4 This is a schematic diagram of the equalization circuit provided in the embodiment of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0023] The technical features involved in the various embodiments of this application described below do not conflict with each other and can be combined with each other.

[0024] When an element is described as "connected" to another element, it can be directly connected to the other element, or there may be one or more intervening elements between them.

[0025] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more.

[0026] This application provides a dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain. This method is applied to a balancing circuit, which includes a balancing branch and N battery branches. The balancing branch is connected to the battery branches, and the N battery branches are connected in parallel, where N is an integer greater than 1. Figure 1 As shown, the dual-modal adaptive equalization method for parallel battery packs based on a power daisy chain includes the following steps S1 to S4:

[0027] Step S1: Obtain the charging / discharging direction, total current value, real-time current value of each battery branch, and real-time SOC value of each battery branch, and calculate the average current value and average SOC value.

[0028] In this embodiment, the charging and discharging directions include charging and discharging. Charging refers to charging the battery branch. Discharging refers to discharging the battery branch.

[0029] The total current value refers to the total current flowing through N parallel battery branches as a whole during the charging and discharging process. The total current value includes both the total charging current and the total discharging current. It should be noted that, theoretically, the total charging current and the total discharging current should not change.

[0030] The real-time current value of each battery branch refers to the actual operating current of each individual battery branch at the current moment. The real-time SOC value of each battery branch refers to the percentage of the current remaining charge of each individual battery branch relative to its rated capacity.

[0031] The average current value refers to the arithmetic mean of the real-time current values ​​of N battery branches. Specifically, the average current value is the sum of the real-time current values ​​of each battery branch divided by N.

[0032] The average SOC value refers to the arithmetic mean of the real-time SOC values ​​of N battery branches. Specifically, the average SOC value is the sum of the real-time SOC values ​​of each battery branch divided by N.

[0033] Step S2: Determine the current difference compensation value for each battery branch based on the charging / discharging direction, average current value, and real-time current value; determine the SOC difference compensation value for each battery branch based on the charging / discharging direction, average SOC value, and real-time SOC value.

[0034] In this embodiment, the current difference compensation value of each battery branch refers to the current compensation amount calculated based on the charging and discharging direction, the average current value and the real-time current value of the branch, which is used to correct the deviation between the real-time current value and the average current value of the battery branch.

[0035] The SOC difference compensation value for each battery branch refers to the SOC compensation amount calculated based on the charging / discharging direction, the average SOC value, and the real-time SOC value of that branch. It is used to correct the deviation between the real-time SOC value and the average SOC value of that battery branch.

[0036] In some embodiments, the method for determining the current difference compensation value of each battery branch based on the charging / discharging direction, average current value, and real-time current value in step S2 above may include: when discharging, if the real-time current value of a battery branch is less than the average current value, then the difference between the average current value and the real-time current value is determined as the current difference compensation value of the battery branch; when charging, if the real-time current value of a battery branch is less than the average current value, then the difference between the average current value and the real-time current value is determined as the current difference compensation value of the battery branch.

[0037] In this embodiment, when the battery branch is discharging, if the real-time current value of the battery branch is less than the average current value, a balancing branch is needed to assist in compensating for the excess current to continue discharging. When the battery branch is charging, if the real-time current value of the battery branch is less than the average current value, a balancing branch is needed to assist in compensating for the excess current to continue charging.

[0038] Specifically, the difference between the average current value and the real-time current value is determined as the current difference compensation value for the battery branch, which can be expressed as: ΔI i =I avg -I i ; where ΔI i I represents the current difference compensation value for the i-th battery pack. avg I represents the average current value. i This represents the real-time current value of the battery branch of the i-th battery pack.

[0039] In some embodiments, the method for determining the SOC difference compensation value of each battery branch based on the charging / discharging direction, average SOC value, and real-time SOC value in step S2 above may include: when discharging, if the real-time SOC value of a battery branch is greater than the average SOC value, then the SOC difference compensation value of the battery branch is calculated based on the difference between the real-time SOC value and the average SOC value; when charging, if the real-time SOC value of a battery branch is less than the average SOC value, then the SOC difference compensation value of the battery branch is calculated based on the difference between the average SOC value and the real-time SOC value.

[0040] In this embodiment, when the battery branch is discharging, if the real-time SOC value of the battery branch is greater than the average SOC value, then the balancing branch is needed to assist in compensating for the excess current to continue discharging. When the battery branch is charging, if the real-time SOC value of the battery branch is less than the average SOC value, then the balancing branch is needed to assist in compensating for the excess current to continue charging.

[0041] In some embodiments, the formula for calculating the SOC difference compensation value is: ΔIs = ΔS × Q nom / T c Where ΔIs is the SOC difference compensation value, in A; ΔS is the SOC difference value, in %; Q nom The nominal capacity of the battery is expressed in Ah; T c To compensate for the time variable, the unit is hours (h).

[0042] In this embodiment, the battery nominal capacity is used to convert the percentage difference in SOC value into actual charge (Ah).

[0043] In some embodiments, the compensation time variable can be a fixed value, such as 1 hour. The specific value can be a factory setting or can be modified as needed during actual operation.

[0044] In some embodiments, the dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain further includes: when charging, the compensation time variable is less than the total remaining charging time; when discharging, the compensation time variable is less than the total remaining discharging time.

[0045] The total remaining charging time refers to the total remaining charging time of the equalization circuit as a whole. The total remaining discharging time refers to the total remaining discharging time of the equalization circuit as a whole.

[0046] Specifically, the dual-modal adaptive balancing method for parallel battery packs based on the power daisy chain also includes determining the remaining total charging time based on the total charging current and the maximum total charging capacity.

[0047] In this embodiment, the method for determining the total remaining charging time can be expressed as follows:

[0048] T remain_charge =(SOC max -SOC avg )*Q nom / I charge ;

[0049] Among them, T remain_charge Indicates the total remaining charging time, SOC max Indicates the maximum total charging capacity, SOC avg Q represents the average SOC value. nom Indicates the nominal capacity of the battery, I charge This indicates the total charging current.

[0050] In some embodiments, the dual-modal adaptive equalization method for parallel battery packs based on the power daisy chain further includes determining the remaining total discharge time based on the total discharge current and the minimum total discharge capacity.

[0051] In this embodiment, the method for determining the total remaining discharge time can be expressed as follows:

[0052] T remain_discharge =(SOC avg -SOC min )*Q nom / I discharge ;

[0053] Among them, T remain_discharge State of Charge (SOC) indicates the total remaining discharge time. avg SOC represents the average SOC value. min Q represents the minimum total discharge capacity. nom Indicates the nominal capacity of the battery, I charge This represents the total discharge current.

[0054] In some embodiments, the dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain further includes: when charging, the compensation time variable is less than the product of the first coefficient and the total remaining charging time; when discharging, the compensation time variable is less than the product of the first coefficient and the total remaining discharging time.

[0055] The first coefficient is greater than 0 and less than 1. The first coefficient can be set according to actual needs; for example, it can be 0.8. Considering the first coefficient can reduce the probability of overestimating the predicted charge / discharge time due to measurement errors.

[0056] In some embodiments, both the total remaining charging time and the total remaining discharging time are determined based on the desired time and the hardware lower limit time.

[0057] In this embodiment, the desired time is the user's desired charge / discharge time, such as 0.3h, 0.5h, 1h, etc. The hardware lower limit time includes the lower limit charging time and the lower limit discharging time. The lower limit charging time is the remaining charging time required for the hardware circuit to charge at the maximum current it can withstand. The lower limit discharging time is the remaining discharging time required for the hardware circuit to discharge at the maximum current it can withstand.

[0058] In some embodiments, both the total remaining charging time and the total remaining discharging time are determined based on the expected time and the hardware lower limit time. This may include: when the expected time is greater than the lower limit charging time, the total remaining charging time is greater than the lower limit charging time but less than the expected time; when the expected time is less than or equal to the lower limit charging time, the total remaining charging time is determined as the lower limit charging time; when the expected time is greater than the lower limit discharging time, the total remaining discharging time is greater than the lower limit discharging time but less than the expected time; when the expected time is less than or equal to the lower limit discharging time, the total remaining discharging time is determined as the lower limit discharging time.

[0059] Step S3: Calculate the total compensation value for each battery branch based on the current difference compensation value and the SOC difference compensation value.

[0060] In this embodiment, the total compensation value of each battery branch is the final compensation amount calculated by combining the current difference compensation value and the SOC difference compensation value of the same battery branch, which is the direct basis for controlling the equalization branch.

[0061] In some embodiments, such as Figure 2 As shown, step S3, the method for calculating the total compensation value of each battery branch based on the current difference compensation value and the SOC difference compensation value, may include steps S31 to S33:

[0062] Step S31: Based on the average SOC value and the real-time SOC value, calculate the SOC difference value of each battery branch.

[0063] In some embodiments, the method for calculating the SOC difference value of each battery branch based on the average SOC value and the real-time SOC value may specifically include: when discharging, if the real-time SOC value of a battery branch is greater than the average SOC value, then the difference between the real-time SOC value and the average SOC value is calculated to obtain the SOC difference value; when charging, if the real-time SOC value of a battery branch is less than the average SOC value, then the difference between the average SOC value and the real-time SOC value is calculated to obtain the SOC difference value.

[0064] Specifically, the method for calculating the difference between the real-time SOC value and the average SOC value to obtain the SOC difference value can be expressed as: ΔSOC i =SOC i -SOC avg ; where ΔSOC i This represents the SOC difference value of the i-th battery pack. i This represents the real-time SOC value of the i-th battery pack. avg This represents the average SOC value.

[0065] Specifically, the method for calculating the difference between the average SOC value and the real-time SOC value to obtain the SOC difference value can be expressed as: ΔSOC i =SOC avg -SOC i ; where ΔSOC i This represents the SOC difference value of the i-th battery pack. i This represents the real-time SOC value of the i-th battery pack. avg This represents the average SOC value.

[0066] Step S32: Determine the first weighting coefficient and the second weighting coefficient based on the SOC difference value of each battery branch.

[0067] In this embodiment, the first weighting coefficient is the adjustment coefficient for the current difference compensation value, and the second weighting coefficient is the adjustment coefficient for the SOC difference compensation value. The sum of the first weighting coefficient and the second weighting coefficient is 1.

[0068] Specifically, the method for determining the first weighting coefficient and the second weighting coefficient based on the SOC difference value of each battery branch may include: when the SOC difference value is greater than the first difference threshold, the first weighting coefficient is determined to be 0.2 and the second weighting coefficient is 0.8; when the SOC difference value is between the second difference threshold and the first difference threshold, the first weighting coefficient is determined to be 0.5 and the second weighting coefficient is 0.5; when the SOC difference value is less than the second difference threshold, the first weighting coefficient is determined to be 0.8 and the second weighting coefficient is 0.2.

[0069] The first difference threshold can be 5%. The second difference threshold can be 2%. See Table 1 below for details.

[0070] Table 1

[0071]

[0072] In Table 1, α represents the first weighting coefficient and β represents the second weighting coefficient.

[0073] Specifically, if the first weighting coefficient is greater than the second weighting coefficient, it indicates priority in current balancing. If the first weighting coefficient is less than the second weighting coefficient, it indicates priority in state-of-the-art (SOC) balancing. If the first weighting coefficient is equal to the second weighting coefficient, it indicates that SOC and current balancing are coordinated.

[0074] Step S33: Combine the current difference compensation value, the first weighting coefficient, the SOC difference compensation value, and the second weighting coefficient to calculate the total compensation value.

[0075] In some embodiments, step S33, combining the current difference compensation value, the first weighting coefficient, the SOC difference compensation value, and the second weighting coefficient, calculates the total compensation value, which includes: adding the product of the current difference compensation value and the first weighting coefficient to the product of the SOC difference compensation value and the second weighting coefficient, and the sum is the total compensation value.

[0076] In this embodiment, the total compensation value is the final compensation amount calculated by combining the current difference compensation value and the SOC difference compensation value of the same battery branch, and it is the direct basis for controlling the balanced branch.

[0077] Specifically, the total compensation value can be calculated as: ΔItotal i =α*ΔI i +β*ΔI soci ; where ΔItotal iLet α represent the total compensation value of the i-th battery pack, β represent the first weighting coefficient, and ΔI represent the second weighting coefficient. i ΔI represents the current difference compensation value for the i-th battery pack. soci This represents the SOC difference compensation value for the i-th battery pack.

[0078] Step S4: Control the operation of the equalization branch based on the total compensation value of each battery branch to equalize the operating current of N battery branches.

[0079] In this embodiment, the operating current of the N battery branches is the actual operating current of each battery branch after equalization control (i.e., the current after adjustment by the equalization branch).

[0080] The equalization circuit controls the operation of the equalization branch (such as a switch, DC / DC module, etc.) through the total compensation value, and performs current compensation on the current of each branch. The ultimate goal is to make the operating current of the N battery branches more consistent, thereby reducing the possibility of increased SOC difference or battery damage caused by uneven current.

[0081] In some embodiments, such as Figure 3 As shown, step S4 above, controlling the operation of the balancing branch based on the total compensation value of each battery branch to balance the operating current of N battery branches, can specifically include the following steps S41 to S44:

[0082] Step S41: Sort the total compensation values ​​of the battery branches to determine the compensation order.

[0083] Specifically, the total compensation values ​​of the battery branches are sorted from largest to smallest to obtain the compensation order. In this embodiment, the battery branch with the larger total compensation value is compensated first.

[0084] Step S42: Determine the target battery branch according to the compensation sequence.

[0085] In this embodiment, the first battery branch in the compensation order (i.e., the battery branch with the largest total compensation value) is determined as the target battery branch.

[0086] Step S43: Determine the control cycle of the target battery branch based on the SOC difference value of the target battery branch.

[0087] The control cycle refers to the period during which current compensation is performed within a predetermined time. The control cycle may include a first control cycle, a second control cycle, and a third control cycle.

[0088] In some embodiments, step S43, determining the control cycle of the target battery branch based on the SOC difference value of the target battery branch, may include: using a first control cycle when the SOC difference value is greater than a first difference threshold; using a second control cycle when the SOC difference value is between a second difference threshold and the first difference threshold; and using a third control cycle when the SOC difference value is less than the second difference threshold.

[0089] Among them, the first difference threshold is greater than the second difference threshold; in terms of time, the first control period is greater than the second control period, and the second control period is greater than the third control period.

[0090] Specifically, the first difference threshold can be 5%. The second difference threshold can be 2%. The first, second, and third control cycles can be set according to actual needs. For example, the first control cycle can be 30s, 40s, 60s, etc., the second control cycle can be 5s, 8s, 10s, etc., and the third control cycle can be 1s, 3s, etc. See Table 2 below for details:

[0091] Table 2

[0092] SOC difference value Execution cycle SOC difference > 5% (maximum difference) First control cycle (e.g., 30 seconds) 2% < SOC difference value ≤ 5% Second control cycle (e.g., 10s) SOC difference ≤2% Third control cycle (e.g., 1 second)

[0093] In this embodiment, if the SOC difference value is greater than the first difference threshold, a relatively slow cycle, such as the first control cycle, is adopted. This cycle prioritizes the SOC difference and performs current compensation more slowly. When using a slower cycle primarily based on the SOC difference, the compensation amount will not be overcompensated within a certain period of time. This slower cycle avoids frequent current switching.

[0094] When the SOC difference value is between the second difference threshold and the first difference threshold, a second control cycle is used as a transitional loop, which performs current compensation in conjunction with the current difference and SOC difference. The second control cycle can smoothly connect the fast and slow cycles, avoiding oscillations caused by mode switching.

[0095] When the SOC difference is less than the second difference threshold, a relatively fast cycle, such as the third control cycle, is adopted. This cycle is primarily driven by the current difference and performs current compensation more quickly. Using a faster cycle primarily driven by the current difference allows for quicker adjustments and avoids overcompensation of the current.

[0096] Step S44: Combine the control cycle and the total compensation value to control the operation of the equalization branch to compensate for the operating current of the target battery branch.

[0097] The equalization branch includes a DC-DC module and N switching modules, with each of the N switching modules corresponding to one of the N battery branches.

[0098] In some embodiments, the method of controlling the operation of the equalization branch by combining the above step S44 and the control cycle and the total compensation value may include: during the control cycle, turning on the switch module corresponding to the target battery branch and turning off the other N-1 switch modules, while controlling the DCDC module to perform current compensation on the target battery branch based on the total compensation value (current value).

[0099] In this embodiment, when the current target battery branch equalization is completed (when the total compensation value of the target battery branch is 0), the next battery branch is determined as the new target battery branch according to the compensation order.

[0100] This application provides a dual-modal adaptive balancing method for parallel battery packs based on a power daisy chain. First, the charging / discharging direction, total current value, and real-time current and SOC values ​​of each battery branch are obtained. The average current and average SOC values ​​are then calculated. Subsequently, based on the charging / discharging conditions, current difference compensation values ​​and SOC difference compensation values ​​for each battery branch are calculated, clarifying the difference between the current and capacity of each battery branch and the average value. The two types of compensation values ​​are then combined to obtain the total compensation value. Finally, the balancing branch is controlled based on the total compensation value to adjust the current of each battery branch, making the operating current of each battery branch tend to be consistent, thus achieving current balance. This application considers both current and SOC state, solving problems such as inconsistent charging / discharging rates and premature depletion caused by uneven current. Furthermore, the balancing branch only needs to handle the current difference between each battery branch (usually a small portion of the total current), rather than the large current of the main circuit. Therefore, the rated power of DC-DC modules and switching elements can be significantly reduced, allowing for the selection of smaller, lower-cost devices.

[0101] Secondly, embodiments of this application provide an equalization circuit 100, such as... Figure 4 As shown, the equalization circuit 100 includes: N battery branches, where N is an integer greater than 1, and equalization branch 20.

[0102] Specifically, each of the N battery branches includes an equivalent resistor and a battery pack. The first end of the equivalent resistor is the first end of the battery branch, and the second end of the equivalent resistor is connected to the first end of the battery pack at a point and is the middle end of the battery branch. The second end of the battery pack is the second end of the battery branch. The N battery branches are connected in parallel, and the first end of the next-level battery branch is connected to the middle end of the previous-level battery branch. The first end of the top-level battery branch is the overall positive terminal, and the second end of each of the N battery branches is connected to the overall negative terminal.

[0103] The balancing branch 20 includes a DC-DC module 21 and N switching modules; the N switching modules correspond one-to-one with the N battery branches, the first end of each of the N switching modules is connected to the second end of the DC-DC module 21, the second end of each of the N switching modules is connected to the middle end of its corresponding battery branch, and the first end of the DC-DC module 21 is connected to the overall positive terminal; wherein, the N switching modules are configured to operate based on switching signals, and the DC-DC module 21 is configured to operate based on control signals, so as to balance the operating current of the N battery branches.

[0104] For example, Figure 4 Taking N=3 as an example, the equalization circuit 100 includes: battery branch 11, battery branch 12, battery branch 13 and equalization branch 20. The equalization branch 20 includes switch module 221, switch module 222, switch module 223 and DC-DC module 21. Figure 4 The positive terminal of the battery pack is the first terminal of the battery pack, and the negative terminal of the battery pack is the second terminal of the battery pack.

[0105] In practical applications, the daisy-chain connection of N battery branches leads to differences in equivalent resistance, resulting in uneven initial current. The balancing branches operate based on switching and control signals. When the current in a battery branch deviates from a target value (e.g., average current), the DC-DC converter module operates based on the control signal, and the corresponding switching module operates based on the switching signal (e.g., turning on), connecting the DC-DC converter module to the middle terminal of the corresponding battery branch. This allows the DC-DC converter module to control the operating current of that battery branch, thereby balancing the operating current of all battery branches. For example, when a battery branch is discharging, if the discharge current of a certain battery branch is low (less than the average current), the switching module of that battery branch is controlled to operate (e.g., turning on), and the DC-DC converter module is also controlled to increase its discharge current. Since the total load current is fixed, adjusting the current in one branch will cause corresponding changes in the currents of other branches. Ultimately, through dynamic compensation by the N balancing branches, the operating currents of all battery branches are brought closer together, achieving a balancing effect.

[0106] This equalization circuit 100 achieves current equalization by working in conjunction with a multiplexer using a shared DC-DC module, thereby reducing costs through the reuse of the DC-DC module. The equalization branch only needs to handle the current differences between the individual battery branches (typically a small portion of the total current), rather than the large current in the main circuit. Therefore, the rated power of the DC-DC module and switching elements can be significantly reduced, allowing for the selection of smaller, lower-cost devices.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of different aspects of this application as described above. For the sake of brevity, they are not provided in detail; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A power daisy chain based dual-mode adaptive balancing method for parallel battery packs, characterized in that, The power daisy chain-based parallel battery pack dual-mode adaptive equalization method is applied to an equalization circuit, the equalization circuit comprising an equalization branch and N battery branches, the equalization branch being connected with the battery branches, and the N battery branches being in parallel, N being an integer greater than 1; The power daisy chain-based parallel battery pack dual-mode adaptive equalization method comprises: The charging and discharging direction, the total current value, the real-time current value of each battery branch, and the real-time SOC value of each battery branch are obtained, and the average current value and the average SOC value are calculated; The current difference compensation value of each battery branch is determined according to the charging and discharging direction, the average current value, and the real-time current value, and the SOC difference compensation value of each battery branch is determined according to the charging and discharging direction, the average SOC value, and the real-time SOC value; Based on the current difference compensation value and the SOC difference compensation value, the total compensation value of each battery branch is calculated, including: Based on the average SOC value and the real-time SOC value, the SOC difference value of each battery branch is calculated; the first weight coefficient and the second weight coefficient are determined based on the SOC difference value of each battery branch; and the total compensation value is calculated by combining the current difference compensation value, the first weight coefficient, the SOC difference compensation value, and the second weight coefficient. Based on the total compensation value of each battery branch, the equalization branch is controlled to work to equalize the working current of the N battery branches.

2. The power based daisy chain based parallel battery pack dual modal adaptive balancing method of claim 1, wherein, The current difference compensation value of each battery branch is determined according to the charging and discharging direction, the average current value, and the real-time current value, including: When discharging, if the real-time current value of a battery branch is less than the average current value, the difference between the average current value and the real-time current value is determined as the current difference compensation value of the battery branch; When charging, if the real-time current value of a battery branch is less than the average current value, the difference between the average current value and the real-time current value is determined as the current difference compensation value of the battery branch.

3. The power based daisy chain based parallel battery pack dual modal adaptive balancing method of claim 1, wherein, The SOC difference compensation value of each battery branch is determined according to the charging and discharging direction, the average SOC value, and the real-time SOC value, including: When discharging, if the real-time SOC value of a battery branch is greater than the average SOC value, the SOC difference compensation value of the battery branch is calculated based on the difference between the real-time SOC value and the average SOC value; When charging, if the real-time SOC value of a battery branch is less than the average SOC value, the SOC difference compensation value of the battery branch is calculated based on the difference between the average SOC value and the real-time SOC value.

4. The power based daisy chain based parallel battery pack dual modal adaptive equalization method of claim 1, wherein, The total compensation value is calculated by combining the current difference compensation value, the first weight coefficient, the SOC difference compensation value, and the second weight coefficient, including: The product of the current difference compensation value and the first weight coefficient is added to the product of the SOC difference compensation value and the second weight coefficient, and the sum is the total compensation value.

5. The power based daisy chain based parallel battery pack dual modal adaptive balancing method of claim 4, wherein, The total compensation value of each battery branch is used to control the operation of the equalization branch to balance the operating current of the N battery branches, including: The total compensation values of the battery branches are sorted to determine the compensation order; The target battery branch is determined according to the compensation order; The control period of the target battery branch is determined based on the SOC difference value of the target battery branch; The equalization branch is controlled to operate based on the control period and the total compensation value to compensate the operating current of the target battery branch.

6. The power based daisy chain based parallel battery pack dual modal adaptive balancing method of claim 5, wherein, The control period of the target battery branch is determined based on the SOC difference value of the target battery branch, including: When the SOC difference value is greater than the first difference threshold, the first control period is used; When the SOC difference value is between the second difference threshold and the first difference threshold, the second control period is used; When the SOC difference value is less than the second difference threshold, the third control period is used; Wherein, the first difference threshold is greater than the second difference threshold; in time, the first control period is greater than the second control period, and the second control period is greater than the third control period.

7. The power based daisy chain based parallel battery pack dual modal adaptive balancing method of claim 1, wherein, The formula for calculating the SOC difference compensation value is: ΔIs = ΔS x Q nom / T c ; Wherein, ΔIs is the SOC difference compensation value, unit is A; ΔS is the SOC difference value, unit is %; Q nom is the battery nominal capacity, unit is Ah; T c is the compensation time variable, unit is h.

8. The power based daisy chain based parallel battery pack dual modal adaptive balancing method of claim 7, wherein, The power daisy chain based parallel battery pack dual-mode adaptive equalization method further includes: When charging, the compensation time variable is less than the total charging remaining time; When discharging, the compensation time variable is less than the total discharging remaining time.

9. The power based daisy chain based parallel battery pack dual modal adaptive balancing method of claim 8, wherein, The total charging remaining time and the total discharging remaining time are determined according to the expected time and the hardware lower limit time.

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