A multi-branch battery pack high-voltage system and control method

Abstract

This invention discloses a multi-branch battery pack high-voltage system and its control method. The multi-branch battery pack high-voltage system includes: multiple battery pack branches, a charging control module, and a discharging control module. Each battery pack branch includes a battery pack, a battery drain interrupter (BDU), and a bidirectional DC-DC converter module. The battery pack is connected to the input terminal of the BDU. The BDU has a main circuit and an equalization circuit. The main circuit controls the on / off of the main power of the battery pack branch it belongs to. The BDUs of each battery pack branch are connected to each other through the equalization circuit for active equalization between branches. The output terminal of the BDU is connected to the input terminal of the bidirectional DC-DC converter module, which controls the charging and discharging current of its respective battery pack branch. The output terminals of all bidirectional DC-DC converter modules are connected in parallel and then connected to the charging control module and the discharging control module. This invention can solve the circulating current problem between battery packs and improve the stability of the multi-branch battery pack high-voltage system.

Description

Technical Field

[0001] This invention relates to a high-voltage system and control method for a multi-branch battery pack, belonging to the field of new energy power battery technology. Background Technology

[0002] Ideally, a battery system consisting of multiple battery packs should have each branch having the same voltage level and charging / discharging with the same current during charging and discharging. However, in reality, due to manufacturing differences, variations in usage conditions, and other factors, the states of the battery packs in each branch can differ. When this difference occurs and the branches are connected, circulating current is generated.

[0003] Circulating current can lead to additional energy loss because some energy is wasted in the internal circulation instead of being used to drive the load. Uneven charging and discharging processes can put varying degrees of stress on different branches, accelerating the aging of some branches and thus shortening the lifespan of the entire battery system. In extreme cases, severe imbalances can lead to overcharging or over-discharging, increasing the risk of thermal runaway and threatening the safety of the battery system.

[0004] In systems composed of multi-branch battery packs, if an imbalance occurs among the branches and no suppression measures are added before direct connection, it will cause inrush currents in the connected circuits, resulting in relay damage or safety hazards. Furthermore, when one branch fails, the battery packs in the other branches should be able to continue operating as needed to avoid sudden shutdown.

[0005] To address the circulating current issue between different battery pack branches, the difference in total voltage between each battery pack branch is detected before applying high voltage to each branch to determine if circulating current will occur.

[0006] The detection and control strategy of this method has flaws because even if the total voltage difference is less than the specified limit, the individual cell voltages of each battery pack branch differ. Directly connecting them for charging and discharging leads to the following two situations: During charging, the battery pack with the highest individual cell voltage may have a relatively high total voltage. Connecting them for charging simultaneously will cause that battery pack to trigger overvoltage protection prematurely, resulting in lower charging energy for other battery pack branches. Charging needs to be stopped first, and the relays switched to restart charging the other battery pack branches. During discharging, the battery pack with the lowest individual cell voltage may have a relatively low total voltage. Connecting them for discharging simultaneously will cause that battery pack to trigger undervoltage protection prematurely, preventing other battery pack branches from continuing to discharge. Discharging needs to be stopped first, and the battery pack in that branch switched to high voltage to allow the other battery pack branches to continue operating at reduced power.

[0007] For example, invention patent CN119995097A discloses a method, device, equipment, and storage medium for controlling circulating current during the discharge of a multi-branch parallel battery pack. It attempts to mitigate circulating current problems by dynamically limiting the discharge current at the end of the discharge cycle. However, this solution only intervenes when the battery is low in charge and the discharge is about to end; it is a passive, reactive remedial measure. It cannot prevent the generation of circulating current during the initial discharge, charging process, or static state, and therefore cannot achieve full-cycle, proactive equalization management.

[0008] For example, invention patent CN119496264A discloses a method for balancing multiple battery packs. This method directly connects multiple battery packs in parallel using relays and relies on circulating currents between the branches for active balancing. Essentially, this active balancing depends on the circulating currents generated when voltage differences exist between the branches to achieve energy transfer. This method cannot fundamentally eliminate circulating currents; instead, it leads to additional energy loss and thermal management stress. Furthermore, in the initial balancing phase or when there are significant differences between branches, the circulating current may be excessive, posing a safety risk.

[0009] In the existing solution, since the discharge and charging current of each battery pack branch cannot be controlled, the only way to prevent overcharging or over-discharging is to switch relays. Because relays posed a safety risk by cutting off under load, they should only be switched after the current has dropped below the safe current level. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-branch battery pack high-voltage system and control method that can solve the circulating current problem between packs and improve the stability of the multi-branch battery pack high-voltage system. To achieve the above objective, this invention is implemented using the following technical solution:

[0011] In a first aspect, the present invention provides a multi-branch battery pack high-voltage system, comprising: multiple battery pack branches, a charging control module, and a discharging control module;

[0012] The battery pack branch includes a battery pack, a BDU, and a bidirectional DC-DC module;

[0013] The battery pack is connected to the input terminal of the BDU. The BDU is equipped with a main circuit and an equalization circuit. The main circuit is used to control the main power of the battery pack branch to which it is located. The BDUs of each battery pack branch are connected through the equalization circuit for active equalization between branches.

[0014] The output terminal of the BDU is connected to the input terminal of the bidirectional DC-DC module, which is used to control the charging and discharging current of the battery pack branch to which it is located.

[0015] The outputs of all bidirectional DC-DC modules are connected in parallel and then connected to the charging control module and the discharging control module.

[0016] In conjunction with the first aspect, optionally, the main circuit includes a main positive relay, a main negative relay, and a main fuse;

[0017] The main fuse and the main positive relay are connected in series between the positive terminal of the battery pack and the positive input terminal of the bidirectional DC-DC module.

[0018] The main negative relay is connected in series between the negative terminal of the battery pack and the negative input terminal of the bidirectional DC-DC module.

[0019] In conjunction with the first aspect, optionally, the equalization circuit includes a positive equalization relay, a negative equalization relay, and an equalization resistor;

[0020] The BDUs of each battery pack branch are connected through the equalization circuit, including:

[0021] One end of the equalization positive relay in the BDU of the first battery pack branch is connected between the main fuse and the main positive relay in the BDU of the first battery pack branch, and the other end of the equalization positive relay in the BDU of the first battery pack branch is connected to one end of the equalization resistor in the BDU of the first battery pack branch.

[0022] The other end of the equalizing resistor in the BDU of the first battery pack branch is connected to one end of the equalizing resistor in the BDU of the second battery pack branch. The other end of the equalizing resistor in the BDU of the second battery pack branch is connected to one end of the equalizing positive relay in the BDU of the second battery pack branch. The other end of the equalizing positive relay in the BDU of the second battery pack branch is between the main fuse and the main positive relay in the BDU of the second battery pack branch.

[0023] One end of the equalization negative relay in the BDU of the second battery pack branch is connected to the negative terminal of the second battery pack, and the other end of the equalization negative relay in the BDU of the second battery pack branch is connected to one end of the equalization negative relay in the BDU of the first battery pack branch. The other end of the equalization negative relay in the BDU of the first battery pack branch is connected to the negative terminal of the first battery pack.

[0024] In conjunction with the first aspect, optionally, the BDU may also include an SBMU;

[0025] The control signal output terminal of the SBMU is connected to the control terminals of the main positive relay and the main negative relay, and is used to output the control information of the main circuit relay; the control signal output terminal of the SBMU is connected to the control terminals of the equalization positive relay and the equalization negative relay, and is used to output the control signal of the equalization circuit relay.

[0026] In a second aspect, the present invention provides a control method for a multi-branch battery pack high-voltage system as described in the first aspect, comprising:

[0027] Real-time monitoring of the status parameters of each battery pack branch;

[0028] Based on the obtained state parameters, determine the balance status of each branch;

[0029] In response to an abnormal balance condition, the corresponding balance control strategy is executed based on the operating status of the multi-branch battery pack high-voltage system.

[0030] The equilibrium control strategy includes:

[0031] If the high-voltage system of a multi-branch battery pack is in a discharging state, the bidirectional DC-DC module is used to control the discharge current of the battery pack branch with abnormal balance.

[0032] If the high-voltage system of a multi-branch battery pack is in charging operation, the bidirectional DC-DC module is used to control the charging current of the battery pack branch with abnormal balance.

[0033] If the high-voltage system of the multi-branch battery pack is in a non-working, idle state, the BDU is used to actively balance the energy between the branches.

[0034] In conjunction with the second aspect, optionally, the state parameters of each battery pack branch include the voltage information of each battery pack branch, the temperature information of each battery pack branch, the state of charge (SOC) value of each battery pack branch, and the discharge current / charging current of each battery pack branch.

[0035] In conjunction with the second aspect, optionally, if the multi-branch battery pack high-voltage system is in a discharging state, the bidirectional DC-DC module is used to control the discharge current of the battery pack branches with abnormal balance conditions, including:

[0036] If the voltage of any battery pack branch is detected to drop to the over-discharge threshold, the discharge current of that battery pack branch is reduced using a bidirectional DC-DC module.

[0037] If a fault is detected in any battery pack branch, the discharge current of that battery pack branch is reduced to 0 using a bidirectional DC-DC module, thereby disconnecting that battery pack branch from the high-voltage system of the multi-branch battery pack.

[0038] In conjunction with the second aspect, optionally, if the multi-branch battery pack high-voltage system is in charging operation, the bidirectional DC-DC module is used to control the charging current of the battery pack branches with abnormal balance conditions, including:

[0039] If the voltage of any battery pack branch is detected to rise to the full charge threshold, the charging current of that battery pack branch is reduced to 0 using a bidirectional DC-DC module, while the charging current of other battery pack branches is increased.

[0040] In conjunction with the second aspect, optionally, if the multi-branch battery pack high-voltage system is in a non-operating, static state, the active energy balancing between branches using the BDU includes:

[0041] If a difference in the state parameters of each battery pack branch is detected and the difference exceeds the equalization threshold, the battery pack branch with the highest state parameter and the battery pack branch with the lowest state parameter are identified. The BDU of the two branches is used to actively equalize the energy between the branches, so that the energy is transferred from the battery pack branch with the highest state parameter to the battery pack branch with the lowest state parameter.

[0042] When performing active energy balancing between branches, the voltage of individual cells in the battery pack branch with the highest state parameter and the voltage of individual cells in the battery pack branch with the lowest state parameter are monitored, and the passive balancing circuit in the battery pack is activated to balance the cells.

[0043] In conjunction with the second aspect, optionally, if the multi-branch battery pack high-voltage system is in a non-operating, static state, the method of using a BDU for active energy balancing between branches further includes:

[0044] When the duration of the high-voltage system of multiple battery packs remaining in a non-working, static state exceeds the preset maintenance threshold, different battery pack branches are selected in sequence for combination, and the energy between branches is actively balanced using BDU until the consistency of the state parameters of each battery pack branch reaches the preset optimal range.

[0045] Compared with the prior art, the beneficial effects achieved by the multi-branch battery pack high-voltage system and control method provided in this embodiment of the invention include:

[0046] This invention provides a multi-branch battery pack high-voltage system. The battery pack is connected to the input terminal of the BDU. The BDU has a main circuit and an equalization circuit. The main circuit is used to control the main power on / off of the battery pack branch it belongs to. The BDUs of each battery pack branch are connected through the equalization circuit for active equalization between branches. The main circuit integrated inside the BDU of this invention can control the main power on / off of the battery pack branch it belongs to, which not only ensures the connection reliability during normal system operation, but also enables rapid disconnection under fault or system command, effectively improving the operational safety and circuit protection capability of the high-voltage system. The equalization circuit integrated inside the BDU of this invention can be connected across multiple battery pack branches to realize the transfer of energy from high-voltage branches to low-voltage branches. The equalization circuit can also complete the energy distribution between battery packs without relying on the DC-DC module, which is especially suitable for fine equalization maintenance in the system's static state, and can significantly improve the voltage and SOC consistency between multiple battery packs.

[0047] This invention provides a multi-branch battery pack high-voltage system. The output terminal of the BDU is connected to the input terminal of a bidirectional DC-DC module, which is used to control the charging and discharging current of its respective battery pack branch. The output terminals of all bidirectional DC-DC modules are connected in parallel and then connected to the charging control module and the discharging control module. By introducing a bidirectional DC-DC module into each battery pack branch, this invention achieves voltage isolation for each battery pack branch, ensuring that its output voltage is not affected by the voltage fluctuations of the battery pack itself. This fundamentally cuts off the path of circulating current generation and avoids energy loss caused by unnecessary circulation between battery packs, thereby significantly improving the overall energy efficiency of the system.

[0048] The control method provided by this invention, in response to the existence of an imbalance condition, executes a corresponding balance control strategy based on the working state of the multi-branch battery pack high-voltage system; this invention adopts corresponding balance control strategies under different working states such as discharging, charging, and resting, effectively preventing abnormal situations such as overcharging and over-discharging, and improving the reliability and safety of the entire battery system.

[0049] The control method provided by this invention, when the multi-branch battery pack high-voltage system is in a discharging state, uses a bidirectional DC-DC module to control the discharge current of battery pack branches with abnormal balance; when the multi-branch battery pack high-voltage system is in a charging state, it uses a bidirectional DC-DC module to control the charging current of battery pack branches with abnormal balance. Each DC-DC module of this invention can independently control the charging / discharging current of its branch; during charging, it can differentiate the charging current to avoid a branch being fully charged too early; during discharging, it can prioritize limiting the discharge current of branches with lower voltage or SOC to prevent over-discharge, achieving precise management and protection of each battery pack branch, greatly improving the stability and reliability of the system.

[0050] The control method provided by this invention allows for active energy balancing between branches when the high-voltage system of a multi-branch battery pack is in a non-working, static state. This invention can actively identify and eliminate deviations caused by the different self-discharge rates of each branch during the static period of the battery pack, ensuring that each branch is in a consistent state when the system is put back into operation, thereby improving the efficiency and capacity utilization of the next charge and discharge.

[0051] This invention controls the current through a DC-DC module during charging / discharging, and also utilizes an equalization loop between BDUs for active energy transfer in the static state, achieving optimal equalization, improving battery pack consistency, solving the circulating current problem between packs, and enhancing the stability of multi-branch battery pack high-voltage systems. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of a multi-branch battery pack high-voltage system according to Embodiment 1 of the present invention;

[0053] Figure 2 This is a control flowchart of the discharge working state in a control method for a multi-branch battery pack high-voltage system according to Embodiment 2 of the present invention;

[0054] Figure 3 This is a control flowchart of the charging operation state in a control method for a multi-branch battery pack high-voltage system according to Embodiment 2 of the present invention.

[0055] Figure 4 This is a control flowchart of the non-working static state in the control method of a multi-branch battery pack high-voltage system in Embodiment 2 of the present invention. Detailed Implementation

[0056] 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.

[0057] Example 1:

[0058] like Figure 1 As shown, this embodiment provides a multi-branch battery pack high-voltage system, including: multiple battery pack branches, a charging control module, and a discharging control module.

[0059] like Figure 1As shown, the battery pack branch includes the battery pack, a BDU (Battery Disconnection Unit), and a bidirectional DC-DC converter module. The battery pack is connected to the input of the BDU, and the output of the BDU is connected to the input of the bidirectional DC-DC converter module. The outputs of all bidirectional DC-DC converter modules are connected in parallel and then connected to the charging control module and the discharging control module.

[0060] like Figure 1 As shown, the BDU includes a main circuit, an equalization circuit, and an SBMU. The main circuit controls the on / off of the main power of its respective battery pack branch. The BDUs of each battery pack branch are connected through the equalization circuit for active equalization between branches. The bidirectional DC-DC module is used to control the charging and discharging current of its respective battery pack branch.

[0061] The main circuit includes a main positive relay, a main negative relay, and a main fuse. The main fuse and the main positive relay are connected in series between the positive terminal of the battery pack and the positive input terminal of the bidirectional DC-DC module. The main negative relay is connected in series between the negative terminal of the battery pack and the negative input terminal of the bidirectional DC-DC module.

[0062] like Figure 1 As shown, the main circuit of battery pack branch 1 includes a main positive relay K11, a main negative relay K12, and a main fuse F11. The main fuse F11 and the main positive relay K11 are connected in series between the positive terminal of the battery pack and the positive input terminal of the bidirectional DC-DC module. The main negative relay K12 is connected in series between the negative terminal of the battery pack and the negative input terminal of the bidirectional DC-DC module.

[0063] like Figure 1 As shown, the main circuit of battery pack branch 2 includes a main positive relay K21, a main negative relay K22, and a main fuse F21. The main circuit of battery pack branch n includes a main positive relay Kn1, a main negative relay Kn2, and a main fuse Fn1. The connection method is the same as that of the main circuit of battery pack branch 1.

[0064] In this embodiment, the main circuit integrated inside the BDU can control the on / off of the main power of the branch of the battery pack, which not only ensures the connection reliability during normal system operation, but also enables rapid disconnection under fault or system command, effectively improving the operational safety and circuit protection capability of the high-voltage system.

[0065] The equalization circuit includes a positive equalization relay, a negative equalization relay, and an equalization resistor.

[0066] The BDUs of each battery pack branch are connected through the equalization circuit, including:

[0067] One end of the equalization positive relay in the BDU of the first battery pack branch is connected between the main fuse and the main positive relay in the BDU of the first battery pack branch, and the other end of the equalization positive relay in the BDU of the first battery pack branch is connected to one end of the equalization resistor in the BDU of the first battery pack branch.

[0068] The other end of the equalizing resistor in the BDU of the first battery pack branch is connected to one end of the equalizing resistor in the BDU of the second battery pack branch. The other end of the equalizing resistor in the BDU of the second battery pack branch is connected to one end of the equalizing positive relay in the BDU of the second battery pack branch. The other end of the equalizing positive relay in the BDU of the second battery pack branch is between the main fuse and the main positive relay in the BDU of the second battery pack branch.

[0069] One end of the equalization negative relay in the BDU of the second battery pack branch is connected to the negative terminal of the second battery pack, and the other end of the equalization negative relay in the BDU of the second battery pack branch is connected to one end of the equalization negative relay in the BDU of the first battery pack branch. The other end of the equalization negative relay in the BDU of the first battery pack branch is connected to the negative terminal of the first battery pack.

[0070] like Figure 1 As shown, in this embodiment, the end of the equalizing positive relay furthest from the equalizing resistor is connected between the main fuse and the main positive relay in the main circuit of this BDU.

[0071] like Figure 1 As shown, the balancing circuit of battery pack branch 1 includes a positive balancing relay K13, a negative balancing relay K14, and a balancing resistor R11. The balancing circuit of battery pack branch 2 includes a positive balancing relay K23, a negative balancing relay K24, and a balancing resistor R21. The balancing circuit of battery pack branch n includes a positive balancing relay Kn3, a negative balancing relay Kn4, and a balancing resistor Rn1.

[0072] This embodiment uses the active balancing path connecting battery pack branch 1 and battery pack branch 2 as an example to illustrate the active balancing path. Figure 1 As shown, the positive output of the battery in battery pack branch 1 is connected to battery pack branch 2 via main fuse F11, equalization positive relay K13 and equalization resistor R11 in sequence. It is then connected to the positive battery terminal of battery pack branch 2 via equalization resistor R21, equalization positive relay K23 and main fuse F21 in sequence. The negative battery terminal of battery pack branch 2 is connected to battery pack branch 1 via equalization negative relay K24 and then to the negative battery terminal of battery pack branch 1 via equalization negative relay K14, thus forming an active equalization path.

[0073] It should be noted that the battery pack branch participates in active balancing by closing the positive and negative balancing relays of the battery pack branch.

[0074] The balancing circuit integrated within the BDU in this embodiment can bridge multiple battery pack branches, enabling the transfer of energy from high-voltage branches to low-voltage branches. The balancing circuit can also perform energy distribution between battery packs without relying on the DC-DC module, making it particularly suitable for fine-grained balancing maintenance in a static system state, and can significantly improve the voltage and SOC consistency between multiple battery packs.

[0075] In this embodiment, the control signal output terminal of the SBMU is connected to the control terminals of the main positive relay and the main negative relay, and is used to output control information for the main circuit relay. The control signal output terminal of the SBMU is also connected to the control terminals of the equalization positive relay and the equalization negative relay, and is used to output control signals for the equalization circuit relay.

[0076] As a further improvement, such as Figure 1 As shown, a current sensor is installed between the negative terminal of the battery in the battery pack branch and the main negative relay and the equalization negative relay to collect current information.

[0077] This embodiment introduces a bidirectional DC-DC module into each battery pack branch, achieving voltage isolation for each battery pack branch. This ensures that the output voltage is not affected by the voltage fluctuations of the battery pack itself, fundamentally cutting off the path of circulating current generation and avoiding energy loss caused by unnecessary circulation between battery packs, thereby significantly improving the overall energy efficiency of the system.

[0078] In this embodiment, the equalization circuit of the battery pack branch is used for active equalization, and the bidirectional DC-DC converter is used to achieve passive equalization of the total voltage of the battery pack. Furthermore, each battery pack achieves passive equalization of individual cells through the sampling board circuit inside the pack. Working together, they achieve the best equalization effect, improve the consistency of the battery pack, solve the circulating current problem between packs, and improve the stability of the high voltage system of multi-branch battery packs.

[0079] Example 2:

[0080] This embodiment provides a control method for the multi-branch battery pack high-voltage system described in Embodiment 1, characterized in that it includes:

[0081] Real-time monitoring of the status parameters of each battery pack branch;

[0082] Based on the obtained state parameters, determine the balance status of each branch;

[0083] In response to an imbalance condition, the corresponding balancing control strategy is executed based on the operating status of the multi-branch battery pack high-voltage system.

[0084] The equilibrium control strategy includes:

[0085] If the high-voltage system of a multi-branch battery pack is in a discharging state, the bidirectional DC-DC module is used to control the discharge current of the battery pack branch with abnormal balance.

[0086] If the high-voltage system of a multi-branch battery pack is in charging operation, the bidirectional DC-DC module is used to control the charging current of the battery pack branch with abnormal balance.

[0087] If the high-voltage system of the multi-branch battery pack is in a non-working, idle state, the BDU is used to actively balance the energy between the branches.

[0088] The status parameters of each battery pack branch include the voltage information, temperature information, state of charge (SOC) value, and discharge / charging current of each battery pack branch.

[0089] This embodiment adopts corresponding equalization control strategies under different operating states such as discharging, charging, and resting, which effectively prevents abnormal situations such as overcharging and over-discharging, and improves the reliability and safety of the entire battery system.

[0090] like Figure 2 As shown, if the high-voltage system of a multi-branch battery pack is in discharge operation, the bidirectional DC-DC module is used to control the discharge current of the battery pack branches with abnormal balance conditions, including:

[0091] If the voltage of any battery pack branch is detected to drop to the over-discharge threshold, the discharge current of that battery pack branch is reduced using a bidirectional DC-DC module.

[0092] If a fault is detected in any battery pack branch, the discharge current of that battery pack branch is reduced to 0 using a bidirectional DC-DC module, thereby disconnecting that battery pack branch from the high-voltage system of the multi-branch battery pack.

[0093] The specific steps of the discharge operation include:

[0094] Step 1: The sampling controller of each battery pack branch performs a self-test.

[0095] Step 2: In response to the self-test passing, high voltage is applied to the BDU of each battery pack branch.

[0096] When the main positive relay Kn1 and main negative relay Kn2 in the BDU are closed, the bidirectional DC-DC module completes pre-charging.

[0097] Step 3: The bidirectional DC-DC module of each battery pack branch outputs constant voltage, and the output current is I1.

[0098] It should be noted that the output current I1 of each bidirectional DC-DC module is the same. The value of the output current I1 is adjusted according to the load requirements.

[0099] Step 4: Monitor the status parameters of each battery pack branch in real time and detect the balance status of each battery pack.

[0100] Step 5: Determine whether the battery pack branch needs to reduce the discharge power.

[0101] In this embodiment, the discharge power needs to be reduced if any of the following conditions are met:

[0102] Total voltage difference > preset threshold V1, minimum voltage of individual cell ≤ preset threshold V2, maximum temperature of individual cell ≥ preset temperature T1, SOC difference > preset threshold D1.

[0103] Step 6: If a certain battery pack branch needs to reduce its discharge power, the bidirectional DC-DC module of that battery pack branch will output a constant voltage with an output current of I2.

[0104] It should be noted that I2 < I1, and in some cases, I2 = 0.

[0105] If the battery pack branch does not need to reduce the discharge power, the bidirectional DC-DC module of the battery pack branch will output a constant voltage with an output current of I1.

[0106] In this embodiment, when the consistency of each battery pack branch is good, the bidirectional DC-DC module controls the discharge current of each battery pack branch to be consistent, ensuring that the state of each battery pack branch remains consistent and stable. If a fault is detected in any battery pack branch, the risk of over-discharge cannot be mitigated without control. By limiting the discharge current of that battery pack branch, the state of that branch becomes consistent with that of the other battery pack branches. When a battery pack branch is no longer allowed to discharge, its discharge current is reduced to zero, and then the bidirectional DC-DC module stops outputting, effectively removing that branch from the system.

[0107] In this embodiment, when a battery pack in a certain branch fails, its discharge current is reduced to zero through the DC-DC module, which can achieve flexible disconnection without impact or arcing, avoiding the safety risks of relay-driven disconnection and ensuring continuous system operation.

[0108] like Figure 3 As shown, if the multi-branch battery pack high-voltage system is in charging operation, the bidirectional DC-DC module is used to control the charging current of the battery pack branches with abnormal balance conditions, including:

[0109] If the voltage of any battery pack branch is detected to rise to the full charge threshold, the charging current of that battery pack branch is reduced to 0 using a bidirectional DC-DC module, while the charging current of other battery pack branches is increased.

[0110] The specific steps for charging include:

[0111] Step 1: Monitor the status parameters of each battery pack branch in real time. The sampling controller of each battery pack branch determines the SOC of the battery pack and the maximum voltage of each individual cell, calculates the charging current requirement, and sends it to the main control unit.

[0112] Step 2: If the full charge condition is met, the bidirectional DC-DC module of each battery pack branch controls the output current to 0, and the battery pack ends the charging process.

[0113] If the condition for filling is not met, return to step 1.

[0114] Step 3: The main control unit calculates the total current value required for charging and sends it to the charging pile.

[0115] As a further improvement, based on the differences in the state parameters of each battery pack branch, different charging currents are applied to each bidirectional DC-DC module to ensure that the state of charge (SOC) values ​​of each battery pack branch are consistent.

[0116] In this embodiment, during the battery system charging process, the charging current of each battery pack branch is controlled by the bidirectional DC-DC module. When the consistency among the battery pack branches is good, the charging current of each battery pack branch is consistent. When the consistency among the battery pack branches is inconsistent, each battery pack branch needs to determine its maximum allowable charging current based on conditions such as SOC, temperature, and individual cell voltage, and limit the charging current through the bidirectional DC-DC module to avoid overcharging. When a battery pack branch meets the full charge condition, the bidirectional DC-DC module controls the charging current of that battery pack branch to 0, and the total charging current demand value is calculated by the main control unit, allowing other branches to continue charging until all battery pack branches are fully charged.

[0117] In addition, during the charging process, the charging current of each branch is controlled by the bidirectional DC-DC module, so that the SOC and voltage of each battery pack branch gradually become consistent.

[0118] In this embodiment, each DC-DC module can independently control the charging / discharging current of its branch; during charging, it can differentiate the charging current to prevent a branch from being fully charged too early; during discharging, it can prioritize limiting the discharge current of branches with lower voltage or SOC to prevent over-discharge, thereby achieving precise management and protection of each battery pack branch and greatly improving the stability and reliability of the system.

[0119] Furthermore, in this embodiment, when a branch battery pack fails, its discharge current is reduced to zero through the DCDC module, which can achieve flexible disconnection without impact or arcing, avoiding the safety risks of relay-driven disconnection and ensuring continuous system operation.

[0120] like Figure 4As shown, if the multi-branch battery pack high-voltage system is in a non-operating, idle state, active energy balancing between branches is performed using the BDU, including:

[0121] If a difference in the state parameters of each battery pack branch is detected and the difference exceeds the equalization threshold, the battery pack branch with the highest state parameter and the battery pack branch with the lowest state parameter are identified. The BDU of the two branches is used to actively equalize the energy between the branches, so that the energy is transferred from the battery pack branch with the highest state parameter to the battery pack branch with the lowest state parameter.

[0122] When performing active energy balancing between branches, the voltage of individual cells in the battery pack branch with the highest state parameter and the voltage of individual cells in the battery pack branch with the lowest state parameter are monitored, and the passive balancing circuit in the battery pack is activated to balance the cells.

[0123] When the duration of the high-voltage system of multiple battery packs remaining in a non-working, static state exceeds the preset maintenance threshold, different battery pack branches are selected in sequence for combination, and the energy between branches is actively balanced using BDU until the consistency of the state parameters of each battery pack branch reaches the preset optimal range.

[0124] This embodiment describes the specific steps of active energy balancing between four battery pack branches in a non-working, idle state using a BDU:

[0125] Step 1: When the sampling controller of each battery pack branch receives a request for high voltage reduction or when the duration of inactivity exceeds the preset maintenance threshold, it detects the total voltage of the battery pack.

[0126] Step 2: In this embodiment, taking the detection that the total voltage of battery pack branch 1 is the highest and the total voltage of battery pack branch 3 is the lowest as an example, we check whether the total voltage difference is greater than the threshold V1.

[0127] Step 3: If the total pressure difference is greater than the threshold V1, proceed with the following steps. If the total pressure difference is not greater than the threshold V1, the equalization positive relay K13 and equalization negative relay K14 in the BDU of battery pack branch 1 are disconnected, and the equalization positive relay K33 and equalization negative relay K34 in the BDU of battery pack branch 3 are disconnected.

[0128] Step 3.1: The BDU of battery pack branch 2 and the BDU of battery pack branch 4 are subjected to high voltage, and the bidirectional DC-DC modules of battery pack branch 2 and battery pack branch 4 stop outputting.

[0129] Step 3.2: The main positive relay K11 and the main negative relay K12 in the BDU of battery pack branch 1 are disconnected, and the main positive relay K31 and the main negative relay K32 in the BDU of battery pack branch 3 are disconnected.

[0130] Step 3.3: In the BDU of battery pack branch 1, the positive equalization relay K13 and the negative equalization relay K14 are closed, and in the BDU of battery pack branch 3, the positive equalization relay K33 and the negative equalization relay K34 are closed.

[0131] Step 3.4: Battery pack branch 1 and battery pack branch 3 enter active balancing.

[0132] Step 3.5: Active balancing completed. Determine whether battery pack branch 1 and battery pack branch 3 require intra-pack balancing.

[0133] Step 3.6.1: If intra-pack equalization is not required, check whether the total voltage difference between battery pack branch 1 and battery pack branch 3 meets the threshold V1. If not, the equalization positive relay K13 and equalization negative relay K14 in the BDU of battery pack branch 1 are disconnected, and the equalization positive relay K33 and equalization negative relay K34 in the BDU of battery pack branch 3 are disconnected. If the conditions are met, repeat steps 3.1-3.5.

[0134] Step 3.6.2: If intra-pack balancing is required, passive cell balancing is performed on the cell with the highest voltage using the sampling board in battery pack 1, and passive cell balancing is performed on the cell with the lowest voltage using the sampling board in battery pack 3.

[0135] In this embodiment, if the high-voltage system of the multi-branch battery pack is in a non-operating, idle state, the voltage, SOC, and other states of the corresponding battery packs are first detected to determine which battery pack branches require active balancing. The balancing circuit between the battery pack with the highest total voltage and the battery pack with the lowest total voltage is controlled to enable active balancing between the two battery packs.

[0136] During active balancing, to avoid over-discharge of individual cells, the battery pack containing the cells with the highest and lowest voltages is detected and identified to determine whether intra-pack balancing is necessary. By sending balancing enable commands to the sampling boards within the battery pack, passive balancing is performed on individual cells, resulting in better battery pack consistency.

[0137] Additionally, when the battery system has been idle for an extended period and requires balancing maintenance, the balancing loop between BDUs (Battery Units) controls active balancing between two battery pack branches. Through multiple combined control steps, the consistency of each battery pack branch is maintained to an optimal state.

[0138] This embodiment can actively identify and eliminate deviations caused by different self-discharge rates of each branch during the battery pack's resting period, ensuring that each branch is in a consistent state when the system is put back into operation, thereby improving the efficiency and capacity utilization of the next charge and discharge cycle.

[0139] In summary, this embodiment uses the DC-DC module for current control during charging / discharging and actively transfers energy through the balancing loop between BDUs in the static state, achieving optimal balancing effect, improving battery pack consistency, solving the circulating current problem between packs, and enhancing the stability of the high-voltage system of multi-branch battery packs.

[0140] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A high-voltage system for a multi-branch battery pack, characterized in that, include: Multiple battery pack branches, charging control module, and discharging control module; The battery pack branch includes a battery pack, a BDU, and a bidirectional DC-DC module; The battery pack is connected to the input terminal of the BDU. The BDU is equipped with a main circuit and an equalization circuit. The main circuit is used to control the main power of the battery pack branch to which it is located. The BDUs of each battery pack branch are connected through the equalization circuit for active equalization between branches. The main circuit includes a main positive relay, a main negative relay, and a main fuse; The main fuse and the main positive relay are connected in series between the positive terminal of the battery pack and the positive input terminal of the bidirectional DC-DC module. The main negative relay is connected in series between the negative terminal of the battery pack and the negative input terminal of the bidirectional DC-DC module; The equalization circuit includes a positive equalization relay, a negative equalization relay, and an equalization resistor. The BDUs of each battery pack branch are connected through the equalization circuit, including: One end of the equalization positive relay in the BDU of the first battery pack branch is connected between the main fuse and the main positive relay in the BDU of the first battery pack branch, and the other end of the equalization positive relay in the BDU of the first battery pack branch is connected to one end of the equalization resistor in the BDU of the first battery pack branch. The other end of the equalizing resistor in the BDU of the first battery pack branch is connected to one end of the equalizing resistor in the BDU of the second battery pack branch. The other end of the equalizing resistor in the BDU of the second battery pack branch is connected to one end of the equalizing positive relay in the BDU of the second battery pack branch. The other end of the equalizing positive relay in the BDU of the second battery pack branch is between the main fuse and the main positive relay in the BDU of the second battery pack branch. One end of the equalization negative relay in the BDU of the second battery pack branch is connected to the negative terminal of the second battery pack, and the other end of the equalization negative relay in the BDU of the second battery pack branch is connected to one end of the equalization negative relay in the BDU of the first battery pack branch, and the other end of the equalization negative relay in the BDU of the first battery pack branch is connected to the negative terminal of the first battery pack. The output terminal of the BDU is connected to the input terminal of the bidirectional DC-DC module, which is used to control the charging and discharging current of the battery pack branch to which it is located. The outputs of all bidirectional DC-DC modules are connected in parallel and then connected to the charging control module and the discharging control module.

2. The multi-branch battery pack high-voltage system according to claim 1, characterized in that, The BDU also includes the SBMU; The control signal output terminal of the SBMU is connected to the control terminals of the main positive relay and the main negative relay, and is used to output the control information of the main circuit relay; the control signal output terminal of the SBMU is connected to the control terminals of the equalization positive relay and the equalization negative relay, and is used to output the control signal of the equalization circuit relay.

3. A control method for a multi-branch battery pack high-voltage system as described in any one of claims 1-2, characterized in that, include: Real-time monitoring of the status parameters of each battery pack branch; Based on the obtained state parameters, determine the balance status of each branch; In response to an abnormal balance condition, the corresponding balance control strategy is executed based on the operating status of the multi-branch battery pack high-voltage system. The equilibrium control strategy includes: If the high-voltage system of a multi-branch battery pack is in a discharging state, the bidirectional DC-DC module is used to control the discharge current of the battery pack branch with abnormal balance. If the high-voltage system of a multi-branch battery pack is in charging operation, the bidirectional DC-DC module is used to control the charging current of the battery pack branch with abnormal balance. If the high-voltage system of the multi-branch battery pack is in a non-working, idle state, the BDU is used to actively balance the energy between the branches.

4. The control method according to claim 3, characterized in that, The state parameters of each battery pack branch include the voltage information, temperature information, state of charge (SOC) value, and discharge / charging current of each battery pack branch.

5. The control method according to claim 3, characterized in that, If the multi-branch battery pack high-voltage system is in a discharging state, the bidirectional DC-DC module is used to control the discharge current of the battery pack branches with abnormal balance conditions, including: If the voltage of any battery pack branch is detected to drop to the over-discharge threshold, the discharge current of that battery pack branch is reduced using a bidirectional DC-DC module. If a fault is detected in any battery pack branch, the discharge current of that battery pack branch is reduced to 0 using a bidirectional DC-DC module, thereby disconnecting that battery pack branch from the high-voltage system of the multi-branch battery pack.

6. The control method according to claim 3, characterized in that, If the multi-branch battery pack high-voltage system is in charging operation, the bidirectional DC-DC module is used to control the charging current of battery pack branches with abnormal balance conditions, including: If the voltage of any battery pack branch is detected to rise to the full charge threshold, the charging current of that battery pack branch is reduced to 0 using a bidirectional DC-DC module, while the charging current of other battery pack branches is increased.

7. The control method according to claim 3, characterized in that, If the multi-branch battery pack high-voltage system is in a non-operating, idle state, active energy balancing between branches is performed using a BDU, including: If a difference in the state parameters of each battery pack branch is detected and the difference exceeds the equalization threshold, the battery pack branch with the highest state parameter and the battery pack branch with the lowest state parameter are identified. The BDU of the two branches is used to actively equalize the energy between the branches, so that the energy is transferred from the battery pack branch with the highest state parameter to the battery pack branch with the lowest state parameter. When performing active energy balancing between branches, the voltage of individual cells in the battery pack branch with the highest state parameter and the voltage of individual cells in the battery pack branch with the lowest state parameter are monitored, and the passive balancing circuit in the battery pack is activated to balance the cells.

8. The control method according to claim 7, characterized in that, If the multi-branch battery pack high-voltage system is in a non-operating, idle state, the active energy balancing between branches using the BDU also includes: When the duration of the high-voltage system of multiple battery packs remaining in a non-working, static state exceeds the preset maintenance threshold, different battery pack branches are selected in sequence for combination, and the energy between branches is actively balanced using BDU until the consistency of the state parameters of each battery pack branch reaches the preset optimal range.

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