Active balancing architecture and control method for multi-branch parallel battery system

Abstract

This invention discloses an active balancing architecture and control method for a multi-branch parallel battery system in the field of battery management technology, aiming to solve the capacity deviation problem in the prior art. It includes a battery system, a bidirectional DC / DC module, and an on-board low-voltage battery module. The battery system includes: several parallel first-level architectures, several parallel second-level architectures corresponding one-to-one with the first-level architectures, and a third-level architecture. The first-level architecture is a battery pack, the second-level architecture is a battery distribution unit (BDU), and the third-level architecture is a high-voltage box electrically connected to each BDU. The bidirectional DC / DC module is electrically connected to the high-voltage box, and the on-board low-voltage battery module is electrically connected to the bidirectional DC / DC module. This invention can charge the battery pack capacity of low-SOC branches of the battery system and discharge branches with higher SOC, achieving both active balancing of the capacity of each branch's battery pack and replenishment of the low-voltage battery.

Description

Technical Field

[0001] This invention relates to an active balancing architecture and method for a multi-branch parallel battery system, belonging to the field of battery management technology. Background Technology

[0002] With the development of the new energy industry, the application of power batteries is becoming increasingly widespread. In the fields of engineering machinery and commercial vehicles, the requirements for the charge / discharge rate and voltage / capacity of battery systems are becoming increasingly stringent, posing a challenge to the overcurrent capacity of high-voltage connectors, high-voltage wiring harnesses, and high-voltage electrical components in the system. Currently, the most effective method for solving the problem of large-capacity battery systems is the series and parallel connection of cells and battery packs. There are two main arrangement schemes: one is to connect multiple battery packs in series to form a battery system, and the other is to connect multiple battery packs in parallel to form a battery system, achieving the integration of large capacity. A battery system using multiple battery packs in series forms a high-voltage, high-capacity battery system with no redundancy design, but if one battery pack in a series fails, the entire battery system cannot function properly. A battery system using multiple battery packs in parallel provides redundancy, but there are capacity deviations and corresponding circulating current impacts between battery packs, leading to uneven charging and discharging, which is detrimental to the performance and lifespan of the battery system.

[0003] The existing technology uses external maintenance equipment to achieve capacity balancing among the battery packs in each branch: each battery pack in multiple parallel branches is individually tested and recharged. This method requires the battery system to be shut down for maintenance and requires disassembling the battery pack interface. It is difficult to operate, has a large workload, takes a long time, and is not very operable.

[0004] In existing technologies, the voltage difference generated by the capacity difference between parallel branches is used to achieve passive balancing between battery packs in each branch: the circulating current generated by the voltage difference between the terminals of each branch is used to adjust the voltage of each branch to be consistent. However, the terminal voltage of the battery pack cannot accurately represent the SOC of the battery, the magnitude of the current generated by the circulating current in the branch cannot be controlled, and for lithium iron phosphate batteries, the voltage platform is relatively stable and the voltage deviation of batteries with different capacities is small. The circulating current of the active balancing branch cannot achieve the purpose of capacity balancing. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide an active balancing architecture and control method for a multi-branch parallel battery system.

[0006] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution.

[0007] In a first aspect, the present invention provides an active balancing architecture for a multi-branch parallel battery system, comprising: a battery system, a bidirectional DC / DC module, and an on-board low-voltage battery module;

[0008] The battery system includes:

[0009] Several parallel first-level architectures, where the first-level architecture is a battery pack.

[0010] Several parallel second-level architectures, each corresponding one-to-one with the first-level architecture, are battery distribution units (BDUs).

[0011] The third-level architecture is a high-voltage box electrically connected to each of the battery distribution units (BDUs).

[0012] The bidirectional DC / DC module is electrically connected to the high-voltage box;

[0013] The vehicle-mounted low-voltage battery module is electrically connected to the bidirectional DC / DC module.

[0014] Each battery distribution unit (BDU) reports the state of charge (SOC), branch battery temperature, and branch battery pack fault information of its corresponding branch battery pack to the control unit of the high-voltage box. The control unit receives the low-voltage battery SOC_LH and low-voltage battery temperature reported by the vehicle low-voltage battery. Based on the reported information, the control unit determines whether the active balancing or low-voltage battery charging trigger conditions are met, and then controls the battery distribution unit to close the corresponding branch battery pack and enter the corresponding discharge balancing mode or charge balancing mode.

[0015] The discharge equalization mode is used to control the branch battery pack that needs to be discharged and equalized to charge the vehicle low-voltage battery through the bidirectional DC / DC module.

[0016] The charging equalization mode is used to control the on-board low-voltage battery to charge the branch battery packs that need to be charged and balanced through the bidirectional DC / DC module.

[0017] Furthermore, the battery pack includes: individual battery cells or battery modules, a relay, a first fuse, and a battery detector (CSC);

[0018] The individual battery cell or battery module is electrically connected to the relay and the first fuse, respectively.

[0019] The battery detector (CSC) is used to collect voltage, current, and temperature information of individual cells or the battery module and send it to the battery distribution unit (BDU).

[0020] Furthermore, the battery power distribution unit includes: a circulating current control circuit, a second fuse, and a battery management unit (SBMU);

[0021] The circulating current control circuit is connected to the second fuse and the high-voltage box respectively, and is used to receive control commands from the SBMU to control the on / off state of the branch battery pack.

[0022] The SBMU is used to receive battery data collected by the battery detector CSC, calculate the state parameters SOX of a single branch battery pack, and report them to the control unit of the high-voltage box. The state parameters SOX include the battery's charge state (SOC), battery's state of health (SOH), battery's power state (SOP), and battery's state of energy (SOE).

[0023] Furthermore, the circulating current control loop includes: a pre-charge relay K0, a pre-charge resistor R0, a main positive relay K1, and a main negative relay K2;

[0024] The main positive relay K1 is connected to the positive terminal of the high voltage box and the positive terminal of the battery pack. The pre-charge relay K0 and the pre-charge resistor R0 are connected in series and then in parallel with the main positive relay K1. The main negative relay K2 is connected to the negative terminal of the high voltage box and the positive terminal of the battery pack. When the corresponding branch battery pack is closed by the SBMU, the pre-charge relay K0 is activated first.

[0025] Furthermore, both the battery pack and the battery power distribution unit include a maintenance switch (MSD) electrically connected to the corresponding fuse.

[0026] Furthermore, the high-voltage box includes: a discharge circuit high-voltage control module and a main battery management unit (MBMU). The MBMU is used to release control commands to the main battery management unit (SBMU) according to external needs, and at the same time, to detect and control the discharge circuit high-voltage control module. The MBMU is also used to control the battery distribution unit to close the corresponding branch battery pack and enter the corresponding discharge equalization mode or charging equalization mode after determining that the active equalization or low-voltage battery charging trigger conditions are met based on the reported information.

[0027] Furthermore, the high-voltage box also includes a charging circuit high-voltage control module, and the MBMU is also used to detect and control the charging circuit high-voltage control module.

[0028] Furthermore, the MBMU is also used to periodically wake up the SBMU and the battery control unit (BCU) of the vehicle low-voltage battery by setting the wake-up detection time of the built-in clock hand, collect fault signals of each branch battery pack, capacity status of each branch battery pack and capacity of the vehicle low-voltage battery, and determine whether each branch battery pack needs to be actively balanced or whether the vehicle low-voltage battery needs to be recharged.

[0029] In a second aspect, the present invention provides a control method for an active balancing architecture based on the multi-branch parallel battery system described in the first aspect, comprising:

[0030] When the battery system enters sleep mode, the SBMU and the BCU of the vehicle low-voltage battery are periodically woken up by the clock set in the MBMU. Based on the SOC1, SOC2, ..., SOCn uploaded by each SBMU, the average SOC and the SOC deviation values ​​ΔSOC1, ΔSOC2, ..., ΔSOCn of each branch battery pack are calculated. The branch Imax with the largest deviation and higher than the average SOC is selected and recorded as ΔSOC_Hmax; the branch Imin with the largest deviation and lower than the average SOC is selected and recorded as ΔSOC_Lmin.

[0031] The system obtains the pre-set capacity deviation threshold ΔSOC_threshold between each branch battery pack, the SOC threshold for priority charging of the vehicle low-voltage battery SOC1_threshold, the upper limit of charging of the vehicle low-voltage battery SOC threshold SOC2_threshold, the SOC threshold of the vehicle low-voltage battery that can support active balancing of the branch battery packs SOC3_threshold, and the allowable charging and discharging temperature range of each branch battery pack and the vehicle low-voltage battery.

[0032] Ensure that the temperatures of each branch battery pack in the battery system and the temperature of the vehicle's low-voltage battery are within the allowable charging and discharging temperature range;

[0033] When ΔSOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold, it is determined that the battery system has an active balancing requirement; when the on-board low-voltage battery SOC_LH is less than SOC1_threshold, there is a priority charging requirement; if neither of the judgment conditions is met, it enters sleep mode.

[0034] Based on the aforementioned active balancing demand or priority power replenishment demand, the following judgment is made:

[0035] When the SOC_LH of the vehicle's low-voltage battery is less than the SOC1_threshold, the battery system enters the discharge equalization mode and uses the branch Imax, which is higher than the average SOC and has the largest deviation, to replenish the vehicle's low-voltage battery.

[0036] When ΔSOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold and ΔSOC_Hmax is greater than or equal to ΔSOC_Lmin, the battery system enters the discharge equalization mode and uses the branch Imax, which is higher than the average SOC and has the largest deviation, to replenish the vehicle's low-voltage battery.

[0037] When SOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold and ΔSOC_Hmax is less than ΔSOC_Lmin, and the SOC of the vehicle's low-voltage battery is not lower than SOC3_threshold, the battery system enters the charging equalization mode, using the vehicle's low-voltage battery to charge the branch Imin with the largest deviation below the average SOC.

[0038] Furthermore, in the discharge equalization mode, the MBMU monitors the SOC and temperature of each branch battery pack in real time to determine whether discharge is allowed. By closing the positive and negative relays of the BDU in the branch Imax with the highest deviation above the average SOC, the bidirectional DC / DC module is enabled to switch from high voltage to low voltage. The bidirectional DC / DC module discharges the battery in the branch Imax with the highest deviation above the average SOC, while simultaneously replenishing the vehicle's low-voltage battery. When the vehicle's low-voltage battery SOC_LH reaches the SOC3_threshold, the battery system discharge equalization is exited.

[0039] In the charging equalization mode, the MBMU monitors the SOC and temperature of each branch battery pack in real time to determine whether charging is allowed. By closing the positive and negative relays of the BDU in the branch Imin with the largest deviation below the average SOC, the bidirectional DC / DC module is enabled to switch from low voltage to high voltage. The bidirectional DC / DC module charges the battery in the branch Imin with the largest deviation below the average SOC. When the vehicle low-voltage battery SOC_LH discharges to SOC2_threshold, the battery system exits the charging equalization mode.

[0040] The beneficial effects achieved by this invention are as follows:

[0041] This invention, through the above-mentioned equalization system and control method, takes into account whether the battery temperature and capacity are within the allowable range. Through the bidirectional DC / DC function, it charges the battery pack capacity of the low SOC branch of the battery system and discharges the battery pack of the high SOC branch. This achieves both active equalization of the battery capacity of each branch of the battery system and replenishment of low-voltage batteries. Attached Figure Description

[0042] Figure 1 A schematic diagram of a three-level architecture for a multi-branch parallel battery system provided for the implementation of this invention;

[0043] Figure 2 A schematic diagram of the active balancing principle of a multi-branch parallel battery system provided for the implementation of this invention;

[0044] Figure 3 A communication diagram illustrating the active balancing of a multi-branch parallel battery system provided for the implementation of this invention;

[0045] Figure 4 The control flowchart for active balancing of a multi-branch parallel battery system provided for the implementation of this invention. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] Example 1: This example introduces an active balancing architecture for a multi-branch parallel battery system, including:

[0050] Battery system, bidirectional DC / DC module and on-board low-voltage battery module;

[0051] The battery system includes:

[0052] Several parallel first-level architectures, where the first-level architecture is a battery pack.

[0053] Several parallel second-level architectures, each corresponding one-to-one with the first-level architecture, are battery distribution units (BDUs).

[0054] The third-level architecture is a high-voltage box electrically connected to each of the battery distribution units (BDUs).

[0055] The bidirectional DC / DC module is electrically connected to the high-voltage box;

[0056] The vehicle-mounted low-voltage battery module is electrically connected to the bidirectional DC / DC module.

[0057] Each battery distribution unit (BDU) reports the state of charge (SOC), branch battery temperature, and branch battery pack fault information of its corresponding branch battery pack to the control unit of the high-voltage box. The control unit receives the low-voltage battery SOC_LH and low-voltage battery temperature reported by the vehicle low-voltage battery. Based on the reported information, the control unit determines whether the active balancing or low-voltage battery charging trigger conditions are met, and then controls the battery distribution unit to close the corresponding branch battery pack and enter the corresponding discharge balancing mode or charge balancing mode.

[0058] The discharge equalization mode is used to control the branch battery pack that needs to be discharged and equalized to charge the vehicle low-voltage battery through the bidirectional DC / DC module.

[0059] The charging equalization mode is used to control the on-board low-voltage battery to charge the branch battery packs that need to be charged and balanced through the bidirectional DC / DC module.

[0060] The battery pack includes: individual battery cells or battery modules, a relay, a first fuse, and a battery detector (CSC).

[0061] The individual battery cell or battery module is electrically connected to the relay and the first fuse, respectively.

[0062] The battery detector (CSC) is used to collect voltage, current, and temperature information of individual cells or the battery module and send it to the battery distribution unit (BDU).

[0063] The battery power distribution unit includes: a circulating current control circuit, a second fuse, and a battery management unit (SBMU);

[0064] The circulating current control circuit is connected to the second fuse and the high-voltage box respectively, and is used to receive control commands from the SBMU to control the on / off state of the branch battery pack.

[0065] The SBMU is used to receive battery data collected by the battery detector CSC, calculate the state parameters SOX of a single branch battery pack, and report them to the control unit of the high-voltage box. The state parameters SOX include the battery's charge state (SOC), battery's state of health (SOH), battery's power state (SOP), and battery's state of energy (SOE).

[0066] The circulating control circuit includes: a pre-charge relay K0, a pre-charge resistor R0, a main positive relay K1, and a main negative relay K2;

[0067] The main positive relay K1 is connected to the positive terminal of the high voltage box and the positive terminal of the battery pack. The pre-charge relay K0 and the pre-charge resistor R0 are connected in series and then in parallel with the main positive relay K1. The main negative relay K2 is connected to the negative terminal of the high voltage box and the positive terminal of the battery pack. When the corresponding branch battery pack is closed by the SBMU, the pre-charge relay K0 is activated first.

[0068] Both the battery pack and the battery power distribution unit include a maintenance switch (MSD) that is electrically connected to the corresponding fuse.

[0069] The high-voltage box includes a discharge circuit high-voltage control module and a main battery management unit (MBMU). The MBMU is used to release control commands to the main battery management unit (SBMU) according to external needs, and at the same time, it detects and controls the discharge circuit high-voltage control module. The MBMU is also used to control the battery distribution unit to close the corresponding branch battery pack and enter the corresponding discharge equalization mode or charging equalization mode after determining that the active equalization or low-voltage battery charging trigger conditions are met based on the reported information.

[0070] The high-voltage box also includes a charging circuit high-voltage control module, and the MBMU is also used to detect and control the charging circuit high-voltage control module.

[0071] The MBMU is also used to periodically wake up the SBMU and the battery control unit (BCU) of the vehicle low-voltage battery by setting the wake-up detection time of the built-in clock hand, collect fault signals of each branch battery pack, capacity status of each branch battery pack and capacity of the vehicle low-voltage battery, and determine whether each branch battery pack needs to be actively balanced or whether the vehicle low-voltage battery needs to be recharged.

[0072] Example 2, based on the same inventive concept as Example 1, introduces an active balancing control method for a multi-branch parallel battery system, including:

[0073] When the battery system enters sleep mode, the SBMU and the BCU of the vehicle low-voltage battery are periodically woken up by the clock set in the MBMU. Based on the SOC1, SOC2, ..., SOCn uploaded by each SBMU, the average SOC and the SOC deviation values ​​ΔSOC1, ΔSOC2, ..., ΔSOCn of each branch battery pack are calculated. The branch Imax with the largest deviation and higher than the average SOC is selected and recorded as ΔSOC_Hmax; the branch Imin with the largest deviation and lower than the average SOC is selected and recorded as ΔSOC_Lmin.

[0074] The system obtains the pre-set capacity deviation threshold ΔSOC_threshold between each branch battery pack, the SOC threshold for priority charging of the vehicle low-voltage battery SOC1_threshold, the upper limit of charging of the vehicle low-voltage battery SOC threshold SOC2_threshold, the SOC threshold of the vehicle low-voltage battery that can support active balancing of the branch battery packs SOC3_threshold, and the allowable charging and discharging temperature range of each branch battery pack and the vehicle low-voltage battery.

[0075] Ensure that the temperatures of each branch battery pack in the battery system and the temperature of the vehicle's low-voltage battery are within the allowable charging and discharging temperature range;

[0076] When ΔSOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold, it is determined that the battery system has an active balancing requirement; when the on-board low-voltage battery SOC_LH is less than SOC1_threshold, there is a priority charging requirement; if neither of the judgment conditions is met, it enters sleep mode.

[0077] Based on the aforementioned active balancing demand or priority power replenishment demand, the following judgment is made:

[0078] When the SOC_LH of the vehicle's low-voltage battery is less than the SOC1_threshold, the battery system enters the discharge equalization mode and uses the branch Imax, which is higher than the average SOC and has the largest deviation, to replenish the vehicle's low-voltage battery.

[0079] When ΔSOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold and ΔSOC_Hmax is greater than or equal to ΔSOC_Lmin, the battery system enters the discharge equalization mode and uses the branch Imax, which is higher than the average SOC and has the largest deviation, to replenish the vehicle's low-voltage battery.

[0080] When SOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold and ΔSOC_Hmax is less than ΔSOC_Lmin, and the SOC of the vehicle's low-voltage battery is not lower than SOC3_threshold, the battery system enters the charging equalization mode, using the vehicle's low-voltage battery to charge the branch Imin with the largest deviation below the average SOC.

[0081] In the discharge equalization mode, the MBMU monitors the SOC and temperature of each branch battery pack in real time to determine whether discharge is allowed. By closing the positive and negative relays of the BDU in the branch Imax with the highest deviation above the average SOC, the bidirectional DC / DC module is enabled to switch from high voltage to low voltage. The bidirectional DC / DC module discharges the battery in the branch Imax with the highest deviation above the average SOC, while simultaneously replenishing the vehicle's low-voltage battery. When the vehicle's low-voltage battery SOC_LH reaches the SOC3_threshold, the battery system discharge equalization is exited.

[0082] In the charging equalization mode, the MBMU monitors the SOC and temperature of each branch battery pack in real time to determine whether charging is allowed. By closing the positive and negative relays of the BDU in the branch Imin with the largest deviation below the average SOC, the bidirectional DC / DC module is enabled to switch from low voltage to high voltage. The bidirectional DC / DC module charges the battery in the branch Imin with the largest deviation below the average SOC. When the vehicle low-voltage battery SOC_LH discharges to SOC2_threshold, the battery system exits the charging equalization mode.

[0083] Example 3, based on the same inventive concept as Example 1, introduces an active balancing architecture for a multi-branch parallel battery system. This architecture achieves active balancing between the branches of the multi-branch parallel battery system and employs methods such as... Figure 1The three-level battery system shown.

[0084] The first level of architecture is the battery pack, which includes individual battery cells or battery modules, relays, fuses, maintenance switches (MSD), and battery detectors (CSC). The CSC is responsible for sampling and monitoring the battery modules.

[0085] The second-level architecture is the battery BDU, which consists of a circulating current control loop, fuses, maintenance switch MSD, voltage sensor CVS, and sub-battery management unit SBMU. The SBMU is responsible for the calculation, control, and protection of the state parameter SOX of a single branch battery, while the CVS is used for voltage monitoring.

[0086] The third-level architecture is the high-voltage box, which mainly includes high-voltage control for the discharge circuit, high-voltage control for the charging circuit, and the main battery management unit (MBMU). The MBMU is responsible for releasing control commands to the SBMU according to external needs, and at the same time, it detects and controls the charging and discharging circuits within the high-voltage box. In range-extended battery systems, there is no need for a charging circuit in the high-voltage box.

[0087] To achieve active balancing among the branches of a multi-branch parallel battery system, this invention, based on a three-level battery system architecture, adjusts the vehicle's unidirectional DC / DC converter to a bidirectional DC / DC converter, and then connects it to the vehicle's on-board low-voltage battery that supplies power to low-voltage components. The on-board low-voltage battery uses a lithium battery module with a controller (BCU), such as... Figure 2 As shown. Wherein:

[0088] In the BDU, the circulating current control circuit mainly consists of a pre-charge relay K0, a pre-charge resistor R0, a main positive relay K1, and a main negative relay K2. When closing each branch battery, the pre-charge circuit is first engaged to alleviate the current surge caused by the voltage inconsistency between branches. It is controlled by each branch SBMU.

[0089] In the high-voltage box, the high-voltage control of the discharge circuit mainly includes the pre-charge circuit of the main drive controller, the bidirectional DC / DC control relay and other high-voltage component control relays. The MBMU collects the high-voltage insulation status and the current of each branch. At the same time, in sleep mode, the MBMU wakes up the SBMU and BCU at regular intervals by setting the wake-up detection time of the built-in clock, collects the fault signals of each branch battery pack, the capacity status of each branch battery and the capacity of the vehicle low-voltage battery, and determines whether each branch battery needs to be actively balanced or whether the vehicle low-voltage battery needs to be recharged.

[0090] To achieve active equalization control of a multi-branch parallel battery system, the main communication information flow between the controllers in the three-level architecture described in this invention is as follows: Figure 3 As shown, where:

[0091] The SBMU reports the state of charge (SOC), temperature, and fault information of each branch battery to the MBMU. The MBMU receives the SOC_LH and temperature of the vehicle low-voltage battery reported by the BCU. Based on the collected information, the MBMU determines whether the active balancing or vehicle low-voltage battery charging trigger conditions are met, and then controls the SBMU to close the corresponding branch to achieve bidirectional DC / DC and enter the corresponding discharge balancing or charge balancing mode.

[0092] This invention provides a control method for actively balancing a multi-branch parallel battery system. The specific control flow is as follows: Figure 4 As shown, the specific control method is as follows:

[0093] SOC Calculation: When the battery system enters sleep mode, the SBMU and BCU are periodically woken up by the clock set in the MBMU. Based on the SOC1, SOC2, ..., SOCn uploaded by each SBMU, the average SOC and the SOC deviation values ​​ΔSOC1, ΔSOC2, ..., ΔSOCn of each branch battery pack are calculated. The branch Imax with the highest deviation above the average SOC is selected and recorded as ΔSOC_Hmax. Similarly, the branch Imin with the highest deviation below the average SOC is selected and recorded as ΔSOC_Lmin.

[0094] Threshold setting: Thresholds can be adjusted according to requirements. Assume that the capacity deviation ΔSOC value between each branch battery pack is set to be greater than 3% (based on battery life calibration); if the vehicle low-voltage battery SOC_LH is less than a certain threshold (30%), priority charging is given, and charging ends when the upper limit SOC threshold (90%) is reached; if the vehicle low-voltage battery SOC_LH is greater than or equal to a certain threshold (30%), active balancing of the battery system can be supported;

[0095] Triggering conditions: The temperatures of all branches of the battery system and the on-board low-voltage battery are within the allowable charging and discharging temperature range.

[0096] When ΔSOC_Hmax or ΔSOC_Lmin is greater than 3%, it is determined that the battery system has an active balancing requirement. When the SOC_LH of the vehicle low-voltage battery is less than 30%, it has a priority charging requirement. If neither of the two conditions is met, the system has no balancing or charging requirement and enters sleep mode.

[0097] When the SOC_LH of the vehicle's low-voltage battery is less than 30%, the battery system enters the discharge equalization mode to replenish the vehicle's low-voltage battery.

[0098] When ΔSOC_Hmax or ΔSOC_Lmin is greater than 3% of the capacity deviation and ΔSOC_Hmax is greater than ΔSOC_Lmin, the battery system enters the discharge equalization mode to replenish the vehicle's low-voltage battery.

[0099] When SOC_Hmax or ΔSOC_Lmin is greater than 3% of the capacity deviation and ΔSOC_Hmax is less than ΔSOC_Lmin, the battery system enters the charging equalization mode.

[0100] Battery system discharge balancing mode: In discharge balancing mode, the MBMU monitors the cell SOC and temperature in real time to determine if discharge is allowed. By closing the positive and negative relays of the Imax branch BDU, the bidirectional DC / DC converter is enabled to switch from high voltage to low voltage. The DC / DC converter discharges the battery in the Imax branch of the battery system, while simultaneously replenishing the vehicle's low-voltage battery. When the vehicle's low-voltage battery SOC_LH reaches 90%, the battery system discharge balancing mode is exited.

[0101] Battery system charging equalization mode: In charging equalization mode, MBMU monitors the cell SOC and temperature in real time to determine whether charging is allowed. By closing the positive and negative relays of the Imin branch BDU, the bidirectional DC / DC converter is enabled to switch from low voltage to high voltage. The DC / DC converter charges the battery in the Imin branch of the battery system. When the on-board low-voltage battery SOC_LH discharges to 30%, the battery system exits charging equalization.

[0102] This invention primarily addresses the capacity deviation problem in multi-branch parallel battery systems used in construction machinery and commercial vehicles. It designs a three-level architecture for multi-branch parallel operation and employs an active balancing scheme. Based on a bidirectional high- and low-voltage DC / DC module between the battery system and the low-voltage battery, and through an automatic wake-up mode after the battery management system enters a dormant state, the system performs discharge balancing on battery packs with higher capacity while simultaneously replenishing the low-voltage battery. Conversely, it performs charging balancing on battery packs with lower capacity, maintaining capacity consistency across all branches.

[0103] An active balancing control method using a multi-branch parallel battery system is adopted to periodically monitor and replenish the low-voltage battery, preventing the vehicle from failing to start due to low-voltage power failure during prolonged periods of vehicle dormancy.

[0104] To address the capacity deviation issue arising from multi-branch parallel battery systems, no external maintenance equipment is required. Instead, an active balancing architecture and control method using high- and low-voltage bidirectional DC / DC modules are employed. This approach actively balances the capacity deviation of each branch, ensuring consistency in the State of Charge (SOC) of each branch, thereby better maximizing the performance of the battery system and extending its lifespan.

[0105] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0106] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0107] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0108] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0109] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An active balancing architecture for a multi-branch parallel battery system, characterized in that, include: Battery system System, bidirectional DC / DC module and vehicle low-voltage battery module; The battery system includes: Several parallel first-level architectures, where the first-level architecture is a battery pack. Several parallel second-level architectures, each corresponding one-to-one with the first-level architecture, are battery distribution units (BDUs). The third-level architecture is a high-voltage box electrically connected to each of the battery distribution units (BDUs). The bidirectional DC / DC module is electrically connected to the high-voltage box; The vehicle-mounted low-voltage battery module is electrically connected to the bidirectional DC / DC module. Each battery distribution unit (BDU) reports the state of charge (SOC), branch battery temperature, and branch battery pack fault information of its corresponding branch battery pack to the control unit of the high-voltage box. The control unit receives the low-voltage battery SOC_LH and low-voltage battery temperature reported by the vehicle low-voltage battery. Based on the reported information, the control unit determines whether the active balancing or low-voltage battery charging trigger conditions are met, and then controls the battery distribution unit to close the corresponding branch battery pack and enter the corresponding discharge balancing mode or charge balancing mode. The discharge equalization mode is used to control the branch battery pack that needs to be discharged and equalized to charge the vehicle low-voltage battery through the bidirectional DC / DC module. The charging equalization mode is used to control the on-board low-voltage battery to charge the branch battery packs that need to be charged and balanced through the bidirectional DC / DC module.

2. The active balancing architecture of the multi-branch parallel battery system according to claim 1, characterized in that, The battery pack includes: individual battery cells or battery modules, a relay, a first fuse, and a battery detector (CSC). The individual battery cell or battery module is electrically connected to the relay and the first fuse, respectively. The battery detector (CSC) is used to collect voltage, current, and temperature information of individual cells or the battery module and send it to the battery distribution unit (BDU).

3. The active balancing architecture of the multi-branch parallel battery system according to claim 2, characterized in that, The battery power distribution unit includes: a circulating current control circuit, a second fuse, and a battery management unit (SBMU); The circulating current control circuit is connected to the second fuse and the high-voltage box respectively, and is used to receive control commands from the SBMU to control the on / off state of the branch battery pack. The SBMU is used to receive battery data collected by the battery detector CSC, calculate the state parameters SOX of a single branch battery pack, and report them to the control unit of the high-voltage box. The state parameters SOX include the battery's charge state (SOC), battery's state of health (SOH), battery's power state (SOP), and battery's state of energy (SOE).

4. The active balancing architecture of the multi-branch parallel battery system according to claim 3, characterized in that, The circulating control circuit includes: a pre-charge relay K0, a pre-charge resistor R0, a main positive relay K1, and a main negative relay K2; The main positive relay K1 is connected to the positive terminal of the high voltage box and the positive terminal of the battery pack. The pre-charge relay K0 and the pre-charge resistor R0 are connected in series and then in parallel with the main positive relay K1. The main negative relay K2 is connected to the negative terminal of the high voltage box and the positive terminal of the battery pack. When the corresponding branch battery pack is closed by the SBMU, the pre-charge relay K0 is activated first.

5. The active balancing architecture of the multi-branch parallel battery system according to claim 1, characterized in that, Both the battery pack and the battery power distribution unit include a maintenance switch (MSD) that is electrically connected to the corresponding fuse.

6. The active balancing architecture of the multi-branch parallel battery system according to claim 1, characterized in that, The high-voltage box includes a discharge circuit high-voltage control module and a main battery management unit (MBMU). The MBMU is used to release control commands to the main battery management unit (SBMU) according to external needs, and at the same time, it detects and controls the discharge circuit high-voltage control module. The MBMU is also used to control the battery distribution unit to close the corresponding branch battery pack and enter the corresponding discharge equalization mode or charging equalization mode after determining that the active equalization or low-voltage battery charging trigger conditions are met based on the reported information.

7. The active balancing architecture of the multi-branch parallel battery system according to claim 6, characterized in that, The high-voltage box also includes a charging circuit high-voltage control module, and the MBMU is also used to detect and control the charging circuit high-voltage control module.

8. The active balancing architecture of the multi-branch parallel battery system according to claim 6, characterized in that, The MBMU is also used to periodically wake up the SBMU and the battery control unit (BCU) of the vehicle low-voltage battery by setting the wake-up detection time of the built-in clock hand, collect fault signals of each branch battery pack, capacity status of each branch battery pack and capacity of the vehicle low-voltage battery, and determine whether each branch battery pack needs to be actively balanced or whether the vehicle low-voltage battery needs to be recharged.

9. A control method for an active balancing architecture of a multi-branch parallel battery system according to any one of claims 1-8, comprising: When the battery system enters sleep mode, the SBMU and the BCU of the vehicle low-voltage battery are periodically woken up by the clock set in the MBMU. Based on the SOC1, SOC2, ..., SOCn uploaded by each SBMU, the average SOC and the SOC deviation values ​​ΔSOC1, ΔSOC2, ..., ΔSOCn of each branch battery pack are calculated. The branch Imax with the largest deviation and higher than the average SOC is selected and recorded as ΔSOC_Hmax; the branch Imin with the largest deviation and lower than the average SOC is selected and recorded as ΔSOC_Lmin. The system obtains the pre-set capacity deviation threshold ΔSOC_threshold between each branch battery pack, the SOC threshold for priority charging of the vehicle low-voltage battery SOC1_threshold, the upper limit of charging of the vehicle low-voltage battery SOC threshold SOC2_threshold, the SOC threshold of the vehicle low-voltage battery that can support active balancing of the branch battery packs SOC3_threshold, and the allowable charging and discharging temperature range of each branch battery pack and the vehicle low-voltage battery. Ensure that the temperatures of each branch battery pack in the battery system and the temperature of the vehicle's low-voltage battery are within the allowable charging and discharging temperature range; When ΔSOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold, it is determined that the battery system has an active balancing requirement; when the on-board low-voltage battery SOC_LH is less than SOC1_threshold, there is a priority charging requirement; if neither of the judgment conditions is met, it enters sleep mode. Based on the aforementioned active balancing demand or priority power replenishment demand, the following judgment is made: When the SOC_LH of the vehicle's low-voltage battery is less than the SOC1_threshold, the battery system enters the discharge equalization mode and uses the branch Imax, which is higher than the average SOC and has the largest deviation, to replenish the vehicle's low-voltage battery. When ΔSOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold and ΔSOC_Hmax is greater than or equal to ΔSOC_Lmin, the battery system enters the discharge equalization mode and uses the branch Imax, which is higher than the average SOC and has the largest deviation, to replenish the vehicle's low-voltage battery. When SOC_Hmax or ΔSOC_Lmin is greater than ΔSOC_threshold and ΔSOC_Hmax is less than ΔSOC_Lmin, and the SOC of the vehicle's low-voltage battery is not lower than SOC3_threshold, the battery system enters the charging equalization mode, using the vehicle's low-voltage battery to charge the branch Imin with the largest deviation below the average SOC.

10. The control method according to claim 9, characterized in that, In the discharge equalization mode, the MBMU monitors the SOC and temperature of each branch battery pack in real time to determine whether discharge is allowed. By closing the positive and negative relays of the BDU in the branch Imax with the highest deviation above the average SOC, the bidirectional DC / DC module is enabled to switch from high voltage to low voltage. The bidirectional DC / DC module discharges the battery in the branch Imax with the highest deviation above the average SOC, while simultaneously replenishing the vehicle's low-voltage battery. When the vehicle's low-voltage battery SOC_LH reaches the SOC3_threshold, the battery system discharge equalization is exited. In the charging equalization mode, the MBMU monitors the SOC and temperature of each branch battery pack in real time to determine whether charging is allowed. By closing the positive and negative relays of the BDU in the branch Imin with the largest deviation below the average SOC, the bidirectional DC / DC module is enabled to switch from low voltage to high voltage. The bidirectional DC / DC module charges the battery in the branch Imin with the largest deviation below the average SOC. When the vehicle low-voltage battery SOC_LH discharges to SOC2_threshold, the battery system exits the charging equalization mode.

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