Multi-cluster battery direct current side switching control method, device and system

Abstract

The application relates to the technical field of battery application energy storage, and discloses a multi-cluster battery direct-current side switching control method, device and system. The method comprises the following steps: starting a plurality of target battery clusters; identifying the current operation condition of a battery system; according to the identified operation condition, configuring a merging judgment condition and / or an isolation judgment condition; the merging judgment condition is used for judging whether an offline battery cluster is allowed to access the direct-current bus; the isolation judgment condition is used for judging whether an online battery cluster triggers to be separated from the direct-current bus; and the switching of the plurality of target battery clusters is controlled according to the merging judgment condition and the isolation judgment condition. The application controls the switching of battery clusters by identifying the operation condition of a battery system and dynamically configuring the merging and isolation judgment conditions, so that flexible and safe switching of a multi-cluster parallel system under different operation conditions is realized.

Description

Technical Field

[0001] This invention relates to the field of battery application energy storage technology, specifically to a method, device, and system for DC-side switching control of multi-cluster batteries. Background Technology

[0002] With the widespread application of battery energy storage systems in industrial and commercial sectors, the topology of multiple battery clusters connected in parallel to a DC bus has become the mainstream solution. During the operation of the energy storage system, the inconsistency and bottleneck effect of the battery cells mean that the worst-performing cluster determines the available capacity and maximum charge and discharge power of the entire system, resulting in a serious waste of assets. How to safely and reliably control the switching of multiple battery clusters connected in parallel to a DC bus is a problem that needs to be studied. Summary of the Invention

[0003] This invention provides a method, apparatus, and system for controlling the DC-side switching of multiple battery clusters, in order to solve the problem of system instability caused by voltage and current surges when switching a battery cluster in a parallel multi-cluster battery system.

[0004] In a first aspect, the present invention provides a method for DC-side switching control of multiple battery clusters, the method comprising: starting several target battery clusters; identifying the current operating conditions of the battery system; configuring, according to the identified operating conditions, a connection determination condition and / or an isolation determination condition, wherein the connection determination condition is used to determine whether offline battery clusters are allowed to connect to the DC bus, and the isolation determination condition is used to determine whether online battery clusters have triggered disconnection from the DC bus; and controlling the switching of several target battery clusters according to the connection determination condition and the isolation determination condition.

[0005] Based on the above technical means, by identifying the operating conditions and configuring the incorporation and / or isolation judgment conditions accordingly, adaptive control of the switching of multi-cluster batteries is realized. It can match the corresponding judgment logic according to the operating conditions, thereby improving the accuracy of switching decisions and the reliability of system operation.

[0006] In one optional implementation, the operating conditions include charging, discharging, and idle conditions. Based on the identified operating conditions, integration determination conditions and / or isolation determination conditions are configured, including: in the charging condition, configuring the integration determination condition as a first integration condition and configuring the isolation determination threshold as a first isolation condition; in the discharging condition, configuring the integration determination threshold as a second integration condition and configuring the isolation determination threshold as a second isolation condition; in the idle condition, configuring the integration determination threshold as a third integration condition and configuring the isolation determination threshold as a third isolation condition.

[0007] Based on the above technical means, by configuring corresponding connection and isolation conditions under the three operating conditions of charging, discharging and idle, the operating condition differentiation of the judgment standard is realized. The connection and isolation conditions under each operating condition are configured independently, which can adapt to the safety requirements under different operating conditions, avoid misjudgment caused by uniform standards, and effectively improve the safety and available capacity of the system in different operating stages.

[0008] In one optional implementation, the first integration condition includes: no fault in the offline battery cluster, the offline battery cluster is not fully charged, the charging current limit value of the offline battery cluster is greater than 0, the isolation time of the offline battery cluster is greater than a first preset time, there is no overvoltage alarm in the offline battery cluster, the total voltage difference between the voltage of the offline battery cluster and the voltage of the online battery cluster is within a preset range, and the highest single-cell voltage of the offline battery cluster is less than a first voltage threshold; the isolation time is the cumulative duration since the offline battery cluster last disconnected from the DC bus; the first isolation condition includes: a battery cluster fault exists in the online battery cluster, the highest single-cell voltage of the online battery cluster is greater than a second voltage threshold, and the online battery cluster is fully charged; wherein, the second voltage threshold is greater than the first voltage threshold.

[0009] Based on the aforementioned technical means, under charging conditions, by setting a first voltage threshold as the upper limit for parallel connection and a second voltage threshold as the upper limit for isolation, with the second voltage threshold being greater than the first voltage threshold, a hysteresis range is formed to prevent frequent switching. The battery cluster voltage must exceed a higher isolation threshold before it is switched off, and it can only be reconnected when it falls back to a lower parallel connection threshold, avoiding repeated switching caused by voltage fluctuations and extending the contactor's service life.

[0010] In one optional implementation, the second inclusion condition includes: no fault in the offline battery cluster, the offline battery cluster is not fully discharged, the discharge current limit value of the offline battery cluster is greater than 0, the isolation time of the offline battery cluster is greater than a first preset time, the offline battery cluster has no undervoltage alarm, the voltage difference between the offline battery cluster and the online battery cluster is within a preset range, and the lowest single-cell voltage of the offline battery cluster is greater than a third voltage threshold; the second isolation condition includes: a battery cluster fault exists in the online battery cluster, the lowest single-cell voltage of the online battery cluster is less than a fourth voltage threshold, and the online battery cluster is fully discharged; wherein, the fourth voltage threshold is less than the third voltage threshold.

[0011] Based on the above technical means, under the discharge condition, by setting a third voltage threshold as the lower limit for connection and a fourth voltage threshold as the lower limit for isolation, and the fourth voltage threshold being lower than the third voltage threshold, a hysteresis range is also formed to prevent frequent switching. The battery cluster voltage must be lower than the lower isolation threshold before it will be switched out, and it can be reconnected only when it rises back to the higher connection threshold, thus ensuring the stability of the switching decision under the discharge condition.

[0012] In one optional implementation, the third integration condition includes: no fault in the offline battery cluster, the charging and discharging current limit values ​​of the offline battery cluster are not simultaneously 0, the isolation time of the offline battery cluster is greater than a first preset time, the voltage difference between the offline battery cluster and the online battery cluster is within a preset range, and the circulating current prediction condition is met; the circulating current prediction condition includes: if the total voltage of the offline battery cluster is lower than the current DC bus voltage, then the highest single-cell voltage of the offline battery cluster is less than a first voltage threshold, and the lowest single-cell voltage of the online battery cluster is greater than a third voltage threshold; if the total voltage of the offline battery cluster is higher than the current DC bus voltage, then the lowest single-cell voltage of the offline battery cluster is greater than a third voltage threshold, and the highest single-cell voltage of the online battery cluster is less than a first voltage threshold; the third isolation condition includes: a battery cluster fault exists in the online battery cluster, the highest single-cell voltage of the online battery cluster is greater than a fifth voltage threshold, and the lowest single-cell voltage of the online battery cluster is less than a sixth voltage threshold.

[0013] Based on the aforementioned technical means, under idle conditions, a bidirectional mutual check of the voltage relationship between the cluster to be integrated and the online cluster is performed by introducing a circulating current prediction condition, thus avoiding circulating current impacts caused by inter-cluster voltage differences. Simultaneously, the isolation conditions under idle conditions are set with a fifth and a sixth voltage threshold as overvoltage and undervoltage isolation trigger points, respectively, ensuring that the voltage of each battery cluster remains within a safe range under idle conditions.

[0014] In one optional implementation, the switching of several target battery clusters is controlled according to the integration determination condition and the isolation determination condition, including: when any candidate battery cluster meets all the integration determination conditions under the corresponding operating condition at the same time, the candidate battery cluster is controlled to be integrated into the DC bus; when any candidate battery cluster meets at least one of the isolation determination conditions under the corresponding operating condition, the candidate battery cluster is controlled to be disconnected from the DC bus.

[0015] Based on the aforementioned technical means, the rules for decision-making regarding merging are clarified: merging decisions use AND logic ("all conditions must be met simultaneously"), while isolation decisions use OR logic ("any condition must be met"). This clarifies the rules for decision-making regarding switching. Strict requirements are applied during merging to ensure security, while lenient triggering is used during isolation to promptly eliminate risks. This balances system security and availability, avoiding decision-making errors caused by logical ambiguity.

[0016] In one optional implementation, when at least one of the isolation criteria for any candidate battery cluster under the corresponding operating condition is met, the candidate battery cluster is controlled to disconnect from the DC bus, including: when at least one of the isolation criteria for any candidate battery cluster under the corresponding operating condition is met, limiting the current of the DC bus according to the number of currently operating battery clusters; detecting the real-time cluster current of the candidate battery cluster; when the real-time cluster current is less than a preset current threshold within a preset timeout period, disconnecting the electrical connection between the candidate battery cluster and the DC bus; if the real-time cluster current is always greater than or equal to the preset current threshold after the preset timeout period, forcibly disconnecting the electrical connection between the candidate battery cluster and the DC bus.

[0017] Based on the aforementioned technical methods, during isolation operations, the DC bus current is first limited according to the current number of operating clusters, then the real-time current of the cluster to be isolated is detected. Disconnection is only executed when the current drops below a preset threshold, achieving smooth control of excessive current and avoiding damage to the contactor from under-load arcing. Simultaneously, a timeout-based forced disconnection mechanism is set up to perform isolation as a fallback if the current fails to decrease, preventing fault escalation and balancing equipment protection with system safety.

[0018] In one optional implementation, activating a plurality of target battery clusters includes: in response to a system power-on command, selecting a battery cluster whose total voltage value is within a preset differential voltage range from fault-free battery clusters as a start-up cluster; closing the pre-charge circuit of the start-up cluster; when the ratio of the bus voltage of the start-up cluster to the corresponding total voltage value reaches a preset threshold, designating the start-up cluster as a target battery cluster, closing the corresponding main circuit and opening the pre-charge circuit, wherein the pre-charge circuit is a circuit between the battery cluster and the DC bus for charging the bus voltage, and the main circuit is a circuit between the battery cluster and the DC bus for normal charging and discharging; and when the ratio of the bus voltage of the start-up cluster to the corresponding total voltage value does not reach the preset threshold within a preset time period, shutting down the corresponding start-up cluster.

[0019] Based on the aforementioned technical methods, the DC bus is pre-charged through a pre-charge circuit. The main circuit is only closed after the ratio of the bus voltage to the total voltage of the battery cluster reaches a preset threshold, effectively avoiding damage to the equipment caused by the inrush current due to excessive voltage difference at startup. Simultaneously, a pre-charge timeout shutdown mechanism is implemented to promptly disconnect the faulty battery cluster in case of pre-charge failure, preventing it from affecting the system startup process and improving system startup safety.

[0020] In one optional implementation, identifying the current operating condition of the battery system includes: entering the operating state if the number of target battery clusters is greater than 0; remaining in the stopped state if the number of target battery clusters is 0; and identifying the current operating condition of the battery system while in the operating state.

[0021] Based on the above technical means, the system enters the running state or remains in the stopped state by the number of target battery clusters, and the operating condition identification is only performed when the system is in the running state. This ensures that the operating condition identification and subsequent switching control are only performed after the system successfully establishes the bus voltage, avoiding invalid switching operations when the system is not in the running state and simplifying the control logic.

[0022] Secondly, the present invention provides a DC-side switching control device for multiple battery clusters, the device comprising: an identification module for activating a plurality of target battery clusters; an operating condition identification module for identifying the current operating condition of the battery system; a condition configuration module for configuring, according to the identified operating condition, a connection determination condition and / or an isolation determination condition, wherein the connection determination condition is used to determine whether an offline battery cluster is allowed to connect to the DC bus, and the isolation determination condition is used to determine whether an online battery cluster has triggered disconnection from the DC bus; and a switching module for controlling the switching of the plurality of target battery clusters according to the connection determination condition and the isolation determination condition.

[0023] Thirdly, the present invention provides a DC-side switching control system for multiple battery clusters, comprising: a charging and discharging device, multiple battery clusters, and a controller; the positive terminals of each battery cluster are connected in parallel to the positive terminal of the charging and discharging device, and the negative terminals of each battery cluster are connected in parallel to the negative terminal of the charging and discharging device; a first switch is provided on a first branch connecting the positive terminal of each battery cluster to the positive terminal of the charging and discharging device, and a second switch is provided on a second branch connecting the negative terminal of each battery cluster to the negative terminal of the charging and discharging device; a pre-charge branch is connected in parallel to both ends of the first switch on each first branch, and the pre-charge branch includes a third switch and a pre-charge resistor; the controller is communicatively connected to the first switch, the second switch, and the third switch, and the controller is used to execute the method of the first aspect or any corresponding embodiment described above.

[0024] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute a multi-cluster battery DC-side switching control method according to the first aspect or any corresponding embodiment described above.

[0025] Fifthly, the present invention provides a computer program product, including computer instructions, which are used to cause a computer to execute a multi-cluster battery DC-side switching control method according to the first aspect above or any corresponding embodiment. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic flowchart of the first type of DC-side switching control method for multi-cluster batteries according to an embodiment of the present invention; Figure 2 This is a second flowchart illustrating the DC-side switching control method for multi-cluster batteries according to an embodiment of the present invention; Figure 3 This is a schematic flowchart of the clustering process of the DC-side switching control method for multi-cluster batteries according to an embodiment of the present invention; Figure 4 This is a flowchart illustrating the isolated cluster of the DC-side switching control method for multi-cluster batteries according to an embodiment of the present invention. Figure 5 This is a schematic flowchart of the start-up cluster of the multi-cluster battery DC-side switching control method according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the system structure of the DC-side switching control method for multi-cluster batteries according to an embodiment of the present invention; Figure 7 Main state machine diagram of the DC-side switching control method for multi-cluster batteries according to an embodiment of the present invention; Figure 8 This is a structural block diagram of a multi-cluster battery DC-side switching control method device according to an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It is understood that before using the technical solutions disclosed in the various embodiments of the present invention, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in the present invention and their authorization should be obtained in accordance with relevant laws and regulations through appropriate means.

[0030] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] Commercial and industrial battery storage systems in related technologies, such as simple multi-cluster direct parallel or fixed configuration operation schemes, face a series of fundamental challenges when dealing with large-scale and highly complex application scenarios.

[0032] After long-term operation, battery cells will exhibit differences in parameters such as capacity, internal resistance, and self-discharge rate. Capacity refers to the actual amount of charge a cell can store, internal resistance refers to the voltage drop coefficient inside the battery when current flows through it, and self-discharge rate refers to the rate at which the charge decays when the battery is at rest. In a fixed parallel structure, all battery clusters are continuously connected to the DC bus for forced charging and discharging. The worst-performing cell or cluster will reach the charging cutoff voltage or discharging termination voltage first. To prevent overcharging or over-discharging of this cluster, the system must stop the entire stack, resulting in the remaining usable capacity of other clusters not being fully utilized.

[0033] In a fixed parallel system, each battery cluster forms a low-impedance electrical path through a DC bus. When insulation degradation, internal short circuit, or signs of impending thermal runaway occur in one cluster, the fault current can be rapidly conducted to other normally operating clusters through the bus, causing the fault range to expand from a single cluster to the entire battery stack. Simultaneously, because all clusters are in a grid-connected state for extended periods, if an individual cluster experiences overvoltage at the end of charging or undervoltage at the end of discharging, the system cannot isolate it for protection; instead, it must shut down the entire stack. This not only interrupts normal charging and discharging scheduling but may also create a power supply gap in emergency support scenarios.

[0034] Energy storage projects involve large investments, and owners are highly concerned about battery life and system efficiency. Battery cycle life and calendar life are closely related to operating conditions; inconsistent charge / discharge depths, continuous overvoltage or undervoltage operation will accelerate cell aging. In a fixed parallel structure, all clusters are charged and discharged simultaneously, making it impossible to differentiate scheduling based on the health status and remaining life of each cluster. This leads to faster-aging clusters retiring prematurely, while slower-aging clusters still have a longer remaining life, resulting in high overall replacement or maintenance costs. Furthermore, under fixed configuration operation, all clusters remain connected to the grid under light load conditions, with converters and contactors continuously energized. This increases the system's own power consumption and reduces charge / discharge conversion efficiency, further weakening the project's overall lifecycle economics.

[0035] According to an embodiment of the present invention, a method for controlling the DC-side switching of multiple cluster batteries is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0036] This embodiment provides a DC-side switching control method for multi-cluster batteries, which can be used in the aforementioned mobile terminals, such as electronic devices. Figure 1This is a flowchart of a multi-cluster battery DC-side switching control method according to an embodiment of the present invention, such as... Figure 1 As shown, the process includes the following steps: Step S101: Activate several target battery clusters.

[0037] Step S102: Identify the current operating conditions of the battery system.

[0038] Step S103: Based on the identified operating conditions, configure the integration judgment condition and / or the isolation judgment condition. The integration judgment condition is used to determine whether the offline battery cluster is allowed to connect to the DC bus, and the isolation judgment condition is used to determine whether the online battery cluster has triggered disconnection from the DC bus.

[0039] Step S104: Control the switching of several target battery clusters according to the merging determination condition and the isolation determination condition.

[0040] Specifically, several target battery clusters are activated, and then the clusters are allowed to enter a ready-to-be-activated state.

[0041] Next, the current operating condition of the battery system is identified. The operating condition of the battery system can be a category label for the segmented working state of the system at a certain moment. This label is jointly defined by electrical parameters such as DC bus voltage amplitude, current polarity, power flow direction, and rate of change. For example, the operating condition can be divided into basic operating conditions: when the bus voltage is stable within the rated range and the current direction is positive, the system is in the discharging condition; when the bus voltage rises according to the set value and the current flows in the reverse direction, the system is in the charging condition; when the bus voltage remains unchanged and the current is close to zero, the system is in the idle condition. This can be further refined. Under charging conditions, it can distinguish between constant current charging and constant voltage charging stages. In the constant current stage, the bus voltage continuously rises while the current remains constant. In the constant voltage stage, the current gradually decreases after the voltage reaches its upper limit. Under discharging conditions, it can distinguish between shallow discharge and deep discharge. During shallow discharge, the terminal voltage remains in the plateau region, while during deep discharge, the voltage rapidly approaches the protection lower limit. Under idle conditions, it can distinguish between resting and float charging maintenance states. During resting, the battery is completely open-circuited with no energy exchange. During float charging, the system replenishes self-discharge losses with a very small current. For systems equipped with fast response functions, the operating condition can also refer to the frequency regulation preparation state or the black start standby state. For energy storage systems connected to the grid, the operating condition can refer to the peak shaving and valley filling mode. The classification method, category, and level of detail of the operating conditions are not limited here.

[0042] Based on the identified operating conditions, the controller invokes the corresponding strategy configuration parameters for the current status label. These parameters determine the specific thresholds for integration and isolation criteria. Integration criteria refer to all requirements that an offline battery cluster must meet to switch from a standby state to a DC bus connection, including, for example, the allowable differential voltage range, state-of-charge deviation limit, upper limit of temperature rise rate, and fault-free flag. Isolation criteria refer to the thresholds or events that must be triggered for an online battery cluster to switch from a DC bus connection to a disconnection state, including, for example, the lower limit of terminal voltage, current rise rate exceeding the limit, temperature exceeding the limit, and protection action signals.

[0043] Based on the pre-configured integration and isolation conditions, the controller controls the switching operations of several target battery clusters. The switching operation is the process by which the controller connects or disconnects the electrical connection between the battery cluster and the DC bus based on the determination results; connection is integration, and disconnection is isolation. For offline clusters to be integrated, the integration sequence is executed when the integration conditions are met; for online clusters already connected to the bus, the isolation sequence is executed when the isolation conditions are triggered. The integration execution method depends on the hardware configuration. For example, a pre-charge circuit can be used in conjunction with the main contactor to complete voltage matching, or the soft-start function of the bidirectional converter can be used to achieve integration without pre-charge, or the main contactor can be directly closed when the voltage difference is extremely small. Specific integration and isolation methods are not limited in this embodiment.

[0044] The DC-side switching control method for multi-cluster batteries provided in this embodiment integrates startup, operating condition identification, condition configuration, and switching execution into a complete control flow. First, the target battery cluster is powered on and allowed to enter a ready-to-switch state, providing a safe and controllable prerequisite for subsequent parallel operation. In the operating condition identification stage, the current state is determined based on real-time electrical parameters collected by the system. Based on the identification result, corresponding strategy configuration parameters are called to set specific thresholds for parallel entry and isolation judgment conditions. This allows the parallel entry and isolation conditions to be dynamically adjusted according to the actual state, avoiding potential misjudgments or failures that might occur under different conditions due to fixed thresholds. The conditions for merging and isolating are configured independently and complementaryly from two directions: the access requirements for offline clusters to access the bus and the trigger conditions for online clusters to detach from the bus. This ensures that the merging operation is performed only when all requirements are met, and the isolation operation is performed promptly when the trigger condition occurs. This prevents mismatched clusters from erroneously merging and causing impacts, and also avoids the impact of abnormal clusters not being removed in time. The switching action performs connection or disconnection operations on the electrical connection between the battery cluster and the DC bus based on the judgment result. During merging, the connection is completed and the current output is adjusted according to the set process. During isolation, the disconnection is completed and the cluster status is updated according to the corresponding process. The timing parameters of each stage in the entire switching process can be configured and adjusted according to different operating conditions. Ultimately, while ensuring safe switching on the DC side, the overall reliability of the system operation is improved.

[0045] This embodiment provides a DC-side switching control method for multi-cluster batteries, which can be used in the aforementioned electronic devices, etc. Figure 2 This is a flowchart of a multi-cluster battery DC-side switching control method according to an embodiment of the present invention, such as... Figure 2 As shown, the process includes the following steps: Step S201: Initiate several target battery clusters. For details, please refer to [link to relevant documentation]. Figure 1 Step S101 of the illustrated embodiment will not be described again here.

[0046] Step S202: Identify the current operating condition of the battery system. For details, please refer to [link to relevant documentation]. Figure 1 Step S102 of the illustrated embodiment will not be described again here.

[0047] Step S203: Based on the identified operating conditions, configure the integration judgment condition and / or the isolation judgment condition. The integration judgment condition is used to determine whether the offline battery cluster is allowed to connect to the DC bus, and the isolation judgment condition is used to determine whether the online battery cluster has triggered disconnection from the DC bus.

[0048] Step S204 involves controlling the switching of several target battery clusters based on the integration and isolation determination conditions. For details, please refer to [link to relevant documentation]. Figure 1 Step S104 of the illustrated embodiment will not be described again here.

[0049] Specifically, the operating conditions include charging, discharging, and idle conditions, and step S203 includes: Step S2031: Under the charging condition, configure the integration judgment condition as the first integration condition and configure the isolation judgment condition as the first isolation condition.

[0050] Step S2032: Under the discharge condition, configure the integration judgment threshold as the second integration condition and configure the isolation judgment condition as the second isolation condition.

[0051] Step S2033: Under idle conditions, configure the merging determination threshold as the third merging condition and configure the isolation determination condition as the third isolation condition.

[0052] Specifically, the controller selects the corresponding configuration branch based on the current operating condition label. The specific content of the merging and isolation conditions varies under different branches, and they are configured independently according to the three basic operating conditions of charging, discharging, and idle.

[0053] During charging, the connection condition is configured as the first connection condition, and the isolation condition is configured as the first isolation condition. The first connection condition and the first isolation condition are a set of conditions specifically designed for the charging process. During charging, the DC bus voltage continuously increases, and the current direction is fixed to flow into the battery side. If an offline cluster wants to connect to the bus, it needs to meet several conditions. The first connection condition may include numerical parameter thresholds, such as a threshold requirement for the offline cluster terminal voltage, or the offline cluster's state of charge being lower than a set state of charge threshold to ensure that the cluster can still receive charging current after connection without prematurely charging. The first connection condition may also include status requirements, such as an offline cluster fault, normal communication between all slave control units within the cluster, and both the main positive contactor and the main negative contactor being open and not stuck together.

[0054] During discharge, the connection condition is configured as the second connection condition, and the isolation condition is configured as the second isolation condition. These two conditions are a combination of conditions designed specifically for the characteristics of the discharge process. During discharge, the bus voltage gradually decreases, and the current flows from the battery side to the load. The load continuously consumes energy. The second connection condition may include, for example, that the difference between the terminal voltage and the bus voltage does not exceed a set threshold, while simultaneously requiring that the offline cluster voltage be greater than a corresponding set threshold to ensure that the cluster can support the load without rapidly depleting after connection. The second isolation condition may be set, for example, that the cluster terminal voltage is lower than a corresponding threshold, or that the state of charge is lower than a corresponding threshold, to prevent over-discharge of the cluster or damage to the battery from abnormally high current.

[0055] In idle conditions, the connection condition is configured as the third connection condition, and the isolation condition is configured as the third isolation condition. The third connection condition and the third isolation condition are a set of conditions designed for a system without power exchange. During idle periods, the bus voltage is relatively stable and the load current is almost zero. The system is not in a hurry to replenish power or release energy. In this case, the third connection condition can be, for example, that the voltage meets the corresponding threshold, ensuring that the connection process causes almost no disturbance to the bus voltage, while allowing for an extended pre-charge time to ensure more adequate voltage matching. The third isolation condition is triggered less frequently in idle conditions. It can be set to trigger an alarm requiring immediate shutdown within the cluster, or to receive a manual maintenance isolation command; if either condition is met, the isolation action is executed.

[0056] The first, second, and third parallel entry conditions and the first, second, and third isolation conditions corresponding to the three operating conditions are independent of each other in terms of specific threshold values, status flag requirements, and logical combinations. They are each bound to different voltage matching accuracy, charge state window, temperature rise rate limit, contactor status requirements, and fault level threshold. By configuring complete judgment logic for the three types of conditions, the control strategy can adapt to the different focuses of the three scenarios of charging, discharging, and idle, so that the parallel entry and isolation operations always meet the actual needs of the current system operation.

[0057] The multi-cluster battery DC-side switching control method provided in this embodiment binds the operating condition identification results with the strategy configuration, using three basic operating conditions—charging, discharging, and idle—as three independent sets of connection and isolation judgment conditions. This enables the control logic to adapt to different operating conditions. Different access criteria are set on the connection side: under charging conditions, the focus is on preventing reverse current from impacting the charging equipment; under discharging conditions, the focus is on demand; and under idle conditions, the focus is on minimizing bus disturbance. These three criteria do not interfere with each other, avoiding the performance loss caused by compromising values ​​under different operating conditions with a single fixed configuration. It avoids missing connection opportunities during discharging due to overly strict conditions, and also avoids introducing abnormal clusters during charging due to overly lenient conditions. Different disconnection trigger conditions are also configured on the isolation side: under charging conditions, the focus is on overvoltage and overcurrent risks; under discharging conditions, the focus is on undervoltage and over-discharge risks; and under idle conditions, the focus is on internal fault maintenance needs. These three types of isolation conditions cover the main risk sources under their respective operating conditions, improving the targeting and timeliness of fault isolation. The merging and isolation judgment conditions each include both numerical parameter thresholds and status flag requirements, constraining the allowable boundaries of switching behavior from both electrical quantity and equipment status dimensions. This avoids incorrect judgments due to communication anomalies or unknown status when relying solely on parameter thresholds. Through the independent configuration and parallel effect of the three sets of conditions, the entire method ensures safe switching on the DC side while taking into account the system operation requirements under various operating conditions.

[0058] In some optional implementations, the first inclusion condition includes: no fault in the offline battery cluster, the offline battery cluster is not fully charged, the charging current limit value of the offline battery cluster is greater than 0, the isolation time of the offline battery cluster is greater than a first preset time, there is no overvoltage alarm in the offline battery cluster, the total voltage difference between the voltage of the offline battery cluster and the voltage of the online battery cluster is within a preset range, and the highest single-cell voltage of the offline battery cluster is less than a first voltage threshold; the isolation time is the cumulative duration since the offline battery cluster last disconnected from the DC bus. Specifically, the first inclusion condition configured under charging conditions is a set of admission criteria composed of multiple dimensions of judgment logic. The offline battery cluster is fault-free, for example, the cluster currently has no fault flag bits, and all status register values ​​reported by slave control units are within the normal range. An offline battery cluster not being fully charged means that the state of charge of the cluster has not yet reached the system's preset charging termination threshold, or the highest single-cell voltage within the cluster has not reached the full-charge judgment baseline. This condition is used to ensure that the cluster has continuous charge receiving capability after being connected to the bus, avoiding being disconnected again shortly after being connected due to reaching full charge, thereby reducing the wear and tear on the contactor's electrical life caused by repeated switching operations. An offline battery cluster charging current limit value greater than zero means that the upper limit of the charging current setpoint for the corresponding converter is positive. If this value is zero or negative, it indicates that the converter is currently in a charging prohibited state or the operating mode is mismatched, and the connection operation should not be triggered in this case. An offline battery cluster isolation time greater than a first preset time means that the time interval from the last disconnection operation of the cluster to the current moment exceeds the system's set safe resting window. This preset time must cover the contactor arc extinguishing delay, the residual charge discharge cycle of the bus capacitor, and the time constant required for the battery's electrochemical polarization voltage to dissipate, ensuring that both the electrical circuit and the battery itself return to a steady state. No overvoltage alarm for offline battery clusters means that the terminal voltage of all individual cells in the cluster has not triggered the system's predefined overvoltage warning flag. This condition is used to exclude clusters with cells already in a critical voltage rise state from being connected. The voltage difference between the offline and online battery clusters is within a preset range, meaning the algebraic difference between the terminal voltage of the offline cluster and the real-time voltage of the current online battery cluster falls within a system-allowed window. The upper and lower limits of this window are determined based on the current magnitude constraint under charging conditions. The highest single-cell voltage of the online battery cluster is less than a first voltage threshold, meaning the sampled value of the single cell corresponding to the maximum voltage in the cluster is lower than the system-set charging safety threshold. When all of the above conditions are met, the controller determines that the offline cluster meets the conditions for connection to the DC bus.

[0059] The first isolation condition is a set of criteria for triggering the disconnection of an online battery cluster from the DC bus during charging. A battery cluster fault exists in the online battery cluster, meaning that any of the grid-connected battery clusters has reported a fault status flag. The highest single-cell voltage of the online battery cluster is greater than the second voltage threshold, meaning that the highest single-cell voltage sample value in any of the grid-connected battery clusters exceeds the charging protection action threshold. This second voltage threshold is numerically higher than the first voltage threshold in the first connection condition; the difference between the two forms a hysteresis range to prevent repeated switching between isolation and reconnection when the single-cell voltage fluctuates near the threshold. The cluster is fully charged, meaning that the state of charge of an online battery cluster has reached the charging termination value or its highest single-cell voltage has reached the full charge judgment line. This cluster no longer has the ability to receive charging current. If it continues to be connected to the grid, it will not only fail to contribute charging capacity but will also become a weak link in the system due to the risk of overcharging. Therefore, it needs to be actively disconnected from the bus. When any of the above conditions are met, the controller performs an electrical isolation operation between the cluster and the DC bus.

[0060] In one example, the conditions for the stack charging state (first connection condition) are: no cluster fault, cluster not fully charged, cluster charging current limit value greater than 0, cluster isolation time greater than 10s, no overvoltage alarm in the cluster, total voltage difference within the range specified in Table 1, and the highest single-cell voltage Vcmax in the cluster < 3400mV (grid-connected single-cell upper limit). The "grid-connected single-cell upper limit" refers to the upper boundary value of the highest single-cell voltage allowed when the battery cluster is connected to the DC bus, that is, the specific value of the first voltage threshold in this example. 3400mV (3.4V) is a typical grid-connected safety threshold for lithium iron phosphate batteries. Its engineering meaning is: below this voltage value, the battery is still in a safe charging window and can continue to charge, allowing the connection operation to be performed.

[0061] Table 1

[0062] Table 1 shows an embodiment of the present invention, specifying the allowable differential voltage ranges corresponding to different operating current ranges. The differential voltage refers to the difference between the voltage at the terminal of the cluster to be connected and the DC bus voltage. A negative current indicates the system is in a charging state, while a positive current indicates a discharging state. The larger the absolute value of the charging current, the greater the required difference between the voltage of the cluster to be connected and the bus voltage, to ensure that the current direction is consistent with the charging direction after connection. Similarly, the larger the absolute value of the discharging current, the greater the required difference between the voltage of the cluster to be connected and the bus voltage, to ensure effective output of the discharging current after connection. When the current is close to zero, the system is in an idle or lightly loaded state, and the allowable differential voltage range is correspondingly widened. This table is used in connection determination to verify whether the total differential voltage is within a preset range. In practical applications, those skilled in the art can adaptively adjust the values ​​in the table according to factors such as battery specifications and system capacity, all of which fall within the protection scope of the present invention.

[0063] In another example, a suitable isolation cluster is selected. The first isolation condition includes: when the battery cluster is faulty or the battery stack is charging, the highest single-cell voltage Vcmax of the cluster is >3500mV (charging high-voltage isolation point) or the cluster is fully charged. This value corresponds to the voltage inflection point at the end of the charging period of the lithium iron phosphate battery. When the single-cell voltage reaches this value, it means that the battery has completed the filling of most of its charge. This triggers protection in advance before the battery actually enters the overcharge danger zone. The grid connection limit of 3400mV is the highest single-cell voltage that allows the cluster to be connected to the bus. The charging high-voltage isolation point of 3500mV is the lowest single-cell voltage that triggers the grid-connected cluster to disconnect from the bus. The 100mV difference between the two constitutes the hysteresis interval. Using the highest single-cell voltage of 3400mV as the boundary, connection is permitted below this value and prohibited above it; using 3500mV as the boundary, isolation is not triggered below this value and is triggered above it. When the highest single-cell voltage of an offline cluster is 3380mV, it meets the grid connection limit and is allowed to connect to the bus. After connection, charging continues. When the voltage rises to 3450mV, it is above the grid connection limit but has not yet reached the isolation point, so the cluster remains connected to the grid and continues charging. When the voltage rises above 3500mV, isolation is triggered and the cluster is disconnected from the grid. After disconnection, the cluster is left to stand still, polarization fades, and the voltage drops back to 3450mV. Since this value is still above the grid connection limit of 3400mV, the cluster will not be allowed to reconnect. It can only be reconnected after its voltage drops back below 3400mV to avoid accidental isolation triggering due to small voltage fluctuations during normal charging. The 100mV difference between the two forms a hysteresis range to prevent repeated switching when the voltage fluctuates near the critical value.

[0064] The DC-side switching control method for multi-cluster batteries provided in this embodiment establishes a combination criterion of the first connection condition and the first isolation condition under the charging condition. On the connection side, a multi-dimensional access logic is constructed, which includes fault status flag, charge state boundary, converter current limiting enable signal, safe resting time window, overvoltage warning flag, terminal voltage deviation window and single cell voltage safety threshold. The criterion works synergistically from multiple levels such as equipment health status, battery remaining capacity, time safety constraints and electrical quantity matching degree to form a complete decision link for offline cluster access to the bus. On the isolation side, this method sets the disconnection trigger mechanism from three dimensions: grid cluster fault flag trigger, individual cell voltage exceeding the protection limit, and full charge state. The second voltage threshold is higher than the first voltage threshold. The hysteresis interval between the two thresholds makes the connection judgment adopt a stricter safety threshold and the isolation judgment adopt a wider protection threshold. The asymmetrical configuration suppresses the frequent operation of the switching contactor when the individual cell voltage fluctuates near the threshold, reducing mechanical losses and system disturbances. Through the existence of "isolation time greater than the first preset time" in the first connection condition, this method also ensures the minimum time interval between two switching operations, providing the necessary transition period for contactor demagnetization and bus capacitor recovery, further improving the reliability and safety of DC side switching.

[0065] In one alternative implementation, the second inclusion condition includes: The offline battery cluster is fault-free, the offline battery cluster is not fully discharged, the discharge current limit value of the offline battery cluster is greater than 0, the isolation time of the offline battery cluster is greater than the first preset time, the offline battery cluster has no undervoltage alarm, the voltage difference between the offline battery cluster and the online battery cluster is within the preset range, and the lowest single cell voltage of the offline battery cluster is greater than the third voltage threshold. The second isolation conditions include: a battery cluster fault exists in the online battery cluster, the lowest single cell voltage of the online battery cluster is less than the fourth voltage threshold, and the online battery cluster is fully discharged; wherein, the fourth voltage threshold is less than the third voltage threshold.

[0066] Specifically, the second connection conditions configured under the discharge condition include: no fault in the offline battery cluster, not fully discharged, discharge current limit value greater than zero, isolation time greater than the first preset time, no undervoltage alarm, total voltage difference within a preset range, and the lowest single-cell voltage greater than the third voltage threshold. Among these, no fault, isolation time greater than the first preset time, and total voltage difference within the preset range are consistent with the definition of the charging condition. "Not fully discharged" corresponds to "not fully charged" in the charging condition, meaning that the state of charge of the cluster has not yet reached the discharge termination threshold or the lowest single-cell voltage has not reached the full discharge determination baseline, ensuring the ability to still output power after connection. "Discharge current limit value greater than zero" corresponds to "charge current limit value greater than zero," meaning that the upper limit of the discharge current setpoint of the corresponding converter for that cluster is positive. No undervoltage alarm corresponds to no overvoltage alarm, meaning that the voltage of all individual cells in the cluster has not triggered the undervoltage warning flag. The undervoltage warning value indicates that the available charge of the cell is almost exhausted, and continued discharge will soon enter the undervoltage protection range. The lowest cell voltage is greater than the third voltage threshold, corresponding to the highest cell voltage being less than the first voltage threshold. This means that the minimum cell voltage sample value in the cluster is higher than the discharge safety threshold value set by the system. When all the above conditions are met, the controller determines that the offline cluster is eligible to be connected to the DC bus.

[0067] The second isolation conditions include the presence of a battery cluster fault online, the lowest individual cell voltage of the online battery cluster being less than the fourth voltage threshold, or the cluster being fully discharged. The presence of a battery cluster fault online is consistent with the charging condition. The lowest individual cell voltage of the online battery cluster being less than the fourth voltage threshold means that the minimum sampled value of the lowest individual cell voltage in the grid-connected cluster is lower than the discharge protection action threshold, preventing battery damage due to over-discharge. The cluster being fully discharged means that the state of charge of the cluster has reached the discharge termination value or the lowest individual cell voltage has reached the full discharge judgment line. The fourth voltage threshold is less than the third voltage threshold, forming a hysteresis interval between the two thresholds to prevent frequent switching due to jitter. When any of the above conditions are met, the controller performs electrical isolation operation between the cluster and the DC bus.

[0068] In one example, the conditions for stack discharge state (second connection condition), no cluster fault, cluster not fully discharged, cluster discharge current limit value greater than 0, cluster isolation time greater than 10s, no undervoltage alarm, total voltage difference within the range specified in Table 1 (the preset voltage difference range corresponds to the allowable voltage difference range under the current level in the aforementioned Table 1), and the lowest single-cell voltage Vcmin of the cluster > 3000mV (grid-connected single-cell lower limit). The "grid-connected single-cell lower limit" refers to the lower boundary value of the lowest single-cell voltage allowed when the battery cluster is connected to the DC bus, that is, the specific value of the third voltage threshold in this example. 3000mV (3.0V) is a typical grid-connected safety threshold for lithium iron phosphate batteries. Its engineering meaning is: above this voltage value, the battery is still within a safe discharge window, has sufficient charge margin to output electrical energy, and allows the connection operation to be performed.

[0069] In another example, the second isolation condition includes: battery cluster failure, or battery stack discharge state, the lowest single cell voltage Vcmin of the cluster is <2900mV (discharge low voltage isolation point) or the cluster is fully discharged. The discharge low voltage isolation point 2900mV means that below this voltage value, the battery has no margin to output power, forming a 100mV difference with 3000mV. 3000mV can still be connected for discharge. When it is discharged to 2900mV, the isolation disconnection is triggered, forming a hysteresis interval to prevent repeated switching when the voltage fluctuates near the critical value.

[0070] The DC-side switching control method for multi-cluster batteries provided in this embodiment uses seven conditions—no faults, not fully discharged, valid discharge current limit, compliant isolation time, no undervoltage alarm, compliant total voltage difference, and safe minimum single-cell voltage—to form the basis for grid connection under discharge conditions. Three of these conditions share definitions with the charging conditions, while the remaining four provide directional symmetry with the charging conditions in terms of remaining discharge capacity, converter enable direction, undervoltage warning, and single-cell voltage lower limit protection. On the isolation side, three conditions serve as the disconnection trigger: online cluster fault, minimum single-cell voltage below the protection threshold, and full discharge state. The protection threshold is lower than the safety threshold during grid connection, and the hysteresis range between them prevents frequent switching triggers when single-cell voltage fluctuates near the critical value. Through the combined configuration of the above grid connection and isolation conditions, the access timing of offline clusters under discharge conditions is effectively screened, and fully discharged or abnormal clusters can be promptly disconnected. The overall switching logic matches the physical constraints of the discharge process.

[0071] In some optional implementations, the third incorporation condition includes: no fault in the offline battery cluster, the charging and discharging current limit values ​​of the offline battery cluster are not simultaneously 0, the isolation time of the offline battery cluster is greater than the first preset time, the voltage difference between the offline battery cluster and the online battery cluster is within a preset range, and the circulating current prediction condition is met. The circulating current prediction conditions include: if the total voltage of the offline battery cluster is lower than the current DC bus voltage, then the highest single-cell voltage of the offline battery cluster is less than the first voltage threshold, and the lowest single-cell voltage of the online battery cluster is greater than the third voltage threshold. If the total voltage of the offline battery cluster is higher than the current DC bus voltage, then the lowest individual voltage of the offline battery cluster is greater than the third voltage threshold, and the highest individual voltage of the online battery cluster is less than the first voltage threshold. The third isolation condition includes: a battery cluster fault exists in the online battery cluster, the highest single cell voltage of the online battery cluster is greater than the fifth voltage threshold, and the lowest single cell voltage of the online battery cluster is less than the sixth voltage threshold.

[0072] Specifically, the third connection conditions configured under idle conditions include: no faults in the offline battery cluster, the charge / discharge current limit values ​​not being simultaneously zero, the isolation time being greater than a first preset time, the total voltage difference being within a preset range, and the circulating current prediction condition being met. Among these, the three conditions of no faults, the isolation time being greater than the first preset time, and the total voltage difference being within a preset range are consistent with the definitions of charging and discharging conditions. The condition that the charge / discharge current limit values ​​are not simultaneously zero means that the charging current limit value and the discharging current limit value of the converter corresponding to the cluster cannot both be zero; at least one of them must be positive. This condition ensures that the cluster can respond to system scheduling after connection, and regardless of whether the system subsequently switches to charging or discharging mode, the cluster has power exchange capability, avoiding the connection of invalid clusters that cannot charge or discharge.

[0073] The circulating current prediction condition is the core criterion in the third connection condition. This condition sets two different individual cell voltage verification paths based on the relative relationship between the total voltage of the offline battery cluster and the current DC bus voltage. The first case is when the total voltage of the offline battery cluster is lower than the current DC bus voltage. In this case, after the offline cluster is connected to the bus, energy from the bus will flow to the cluster in the charging direction. The circulating current prediction condition requires that the highest individual cell voltage of the offline battery cluster is less than the first voltage threshold, while the lowest individual cell voltage of the currently online battery cluster is greater than the third voltage threshold. The highest individual cell voltage on the offline side being less than the first voltage threshold ensures that no individual cell in the offline cluster is near the charging safety threshold. After connection, the cluster has sufficient voltage space to receive charging current without rapidly reaching the overvoltage protection line. The lowest single-cell voltage on the online side is greater than the third voltage threshold, ensuring that the voltage of all cells in the currently grid-connected battery cluster is higher than the discharge safety threshold. The operating cluster may charge the cluster to be connected, and the operating cluster that is already connected to the grid can continue to discharge because it is higher than the discharge safety threshold. No single cell is in an undervoltage critical state. When both conditions are met, after the offline cluster is connected, no matter how energy flows, the system will not immediately trigger isolation due to the single-cell voltage of a certain cluster exceeding the limit, thereby eliminating abnormal single-cell states that may trigger protection actions before circulating current occurs.

[0074] The second scenario is when the total voltage of the offline battery cluster is higher than the current DC bus voltage. In this case, after the offline cluster is connected to the bus, its energy will flow to the bus and the online cluster, with the current direction being the discharge direction. In this scenario, the circulating current prediction condition requires that the lowest individual cell voltage of the offline battery cluster is greater than the third voltage threshold, while the highest individual cell voltage of the currently online battery cluster is less than the first voltage threshold. The lowest individual cell voltage on the offline side being greater than the third voltage threshold ensures that no cell in the offline cluster is near its discharge safety threshold, giving the cluster sufficient voltage margin to output power without rapidly dropping to the undervoltage protection line after connection. The highest individual cell voltage on the online side being less than the first voltage threshold ensures that the voltage of all cells in the currently connected battery cluster is below the charging safety threshold, with no cell in an overvoltage critical state. These two scenarios constitute the complete logic of the circulating current prediction condition. Essentially, this condition simulates the possible energy flow direction after the offline cluster is connected and simultaneously verifies the individual cell voltage margin from both sides, ensuring that no cell in a critical state exists in the system regardless of the energy flow direction, thereby avoiding protection events triggered during charge transfer due to voltage differences.

[0075] The third isolation condition includes the presence of a battery cluster fault online, the highest single-cell voltage of the online battery cluster being greater than the fifth voltage threshold, or the lowest single-cell voltage being less than the sixth voltage threshold. The presence of a battery cluster fault online is consistent with the aforementioned conditions. The highest single-cell voltage of the online battery cluster being greater than the fifth voltage threshold means that the maximum single-cell voltage sample value within the grid-connected cluster exceeds the system's set idle overvoltage protection threshold; the lowest single-cell voltage of the online battery cluster being less than the sixth voltage threshold means that the minimum single-cell voltage sample value within the grid-connected cluster is lower than the system's set idle undervoltage protection threshold. The set values ​​of the fifth and sixth voltage thresholds under idle conditions correspond to the system's requirements for maintaining the bus voltage range when not actively charging or discharging. Their relationship with the first and third voltage thresholds depends on the specific project's safety margin strategy and is not limited here. When any of the above conditions are met, the controller performs electrical isolation operation between that cluster and the DC bus.

[0076] In one example, the conditions for merging the cluster in an idle state (the third merging condition), no cluster faults, the current limit values ​​for cluster charging and discharging not being simultaneously 0, the cluster isolation time being greater than 10s, and the total voltage difference being within the range specified in Table 1 (the preset voltage difference range corresponds to the allowable voltage difference range under the current level in Table 1 above), in order to ensure that the system will not trigger high or low voltage alarms due to circulating current after the cluster to be merged, circulating current prediction is required. If the total voltage of the cluster to be merged is lower than the stack voltage, the operating cluster may charge the cluster to be merged, then the highest voltage of the individual unit of the cluster to be merged, Vcmax, is less than 3400mV (the upper limit of the grid-connected unit), and the lowest voltage of the individual unit of the operating cluster, Vcmin, is greater than 3000mV (the lower limit of the grid-connected unit); if the total voltage of the cluster to be merged is higher than the stack voltage, the operating cluster may discharge the cluster to be merged, then the lowest voltage of the individual unit of the cluster to be merged, Vcmin, is greater than 3000mV (the lower limit of the grid-connected unit), and the highest voltage of the individual unit of the operating cluster, Vcmax, is less than 3400mV (the upper limit of the grid-connected unit).

[0077] In another example, the third isolation condition includes: 1. Battery cluster failure.

[0078] 2. In the idle state of the battery stack, the highest single-cell voltage Vcmax of the cluster is >3600mV (idle high-voltage isolation point). In the idle state of the battery stack, the lowest single-cell voltage Vcmin of the cluster is <2800mV (idle low-voltage isolation point). The system is in an idle state with no active charging or discharging power output. The cell voltage is only affected by temperature, weak inter-cluster circulating current, and slow drift due to self-discharge, without a continuous unidirectional voltage increase / decrease trend. Compared with the charging and discharging conditions under power, the protection boundary can be relaxed. The charging dynamic isolation point of 3500mV and the discharging dynamic isolation point of 2900mV are narrow margin protection values ​​under load conditions. On this basis, each is widened by 100mV to obtain the 3600mV high-voltage and 2800mV low-voltage static isolation thresholds. When the lithium iron phosphate cells are not continuously charged or discharged, they will not suffer irreversible damage such as lithium plating or copper deposition when placed in the 3500~3600mV and 2800~2900mV ranges for a short time. A wider hysteresis range is formed to avoid frequent switching of the contactor caused by temperature and pressure difference disturbances. These two sets of values ​​are used as static limit fallback protection to prevent long-term static overvoltage and power deterioration of individual cells. At the same time, a hierarchical voltage control logic is formed with the grid access thresholds of 3400mV and 3000mV to balance operational stability and cell safety.

[0079] The multi-cluster battery DC-side switching control method provided in this embodiment sets a third connection condition, including a circulating current prediction condition, under idle conditions. This condition verifies the individual cell voltage margin simultaneously from both the offline and online sides based on the relative levels of the offline cluster total voltage and the bus voltage. This extends the assessment of circulating current risk from a single device to all grid-connected clusters in the entire parallel system, achieving state linkage judgment between offline and online clusters. By cross-verifying the highest or lowest individual cell voltage on the offline side with the lowest or highest individual cell voltage on the online side, this method preemptively eliminates the possibility of any critical voltage cell on either side before connection is executed, thereby minimizing the risk of protection actions caused by circulating current before physical connection is established. The condition that the charging and discharging current limit values ​​are not simultaneously zero ensures that clusters connected to the idle bus have bidirectional power response capabilities, avoiding the inability to participate in subsequent operating condition switching due to a zero current limit value after connection. The isolation side sets a fifth and sixth voltage threshold as overvoltage and undervoltage protection thresholds under idle conditions, which, together with the aforementioned isolation conditions under charging and discharging conditions, constitute a grid disconnection protection system covering all operating conditions. By implementing the above combination of connection and isolation conditions under idle conditions, the system maintains continuous monitoring of the voltage boundaries of all grid-connected clusters in the absence of power exchange, and establishes a strict circulating current prediction mechanism for the access of offline clusters.

[0080] In some optional implementations, step S204 above includes: Step a1: When all the connection determination conditions of any candidate battery cluster under the corresponding operating conditions are met simultaneously, control the candidate battery cluster to be connected to the DC bus.

[0081] Step a2: When at least one of the isolation judgment conditions of any candidate battery cluster under the corresponding operating condition is met, control the candidate battery cluster to disconnect from the DC bus.

[0082] Specifically, the controller will only allow the battery cluster to connect to the DC bus after all the current operating conditions are met at once; if any condition is not met, it cannot be connected to the grid, thus avoiding grid connection risks such as differential voltage, faults, voltage exceeding limits, and insufficient resting time from the source.

[0083] Once a battery cluster is connected to the grid, the controller will immediately disconnect the contactor to disconnect it from the bus as soon as any isolation condition is triggered. This can quickly disconnect faulty, over-voltage / under-voltage, and fully charged / discharged battery clusters without waiting for multiple faults to accumulate, thus preventing the escalation of system hazards.

[0084] In one example, such as Figure 3As shown, a suitable cluster is selected for integration. Only one cluster is integrated at a time. All non-running clusters are checked one by one. If a cluster that meets the criteria is detected, the process stops checking and proceeds to the next step to perform the integration operation. The positive and negative contactors of the cluster to be integrated are closed, and the dynamic integration is completed. The dynamic integration process ends when the positive and negative contactors of the cluster to be integrated are closed. If no battery cluster meets the criteria, the process ends directly.

[0085] In another example, dynamic isolation refers to the process of cutting off the output of some or all battery clusters from a state where the entire stack is already running and at least one cluster of cells is outputting data. The specific steps are as follows: Select a suitable isolation cluster. For all operating clusters, if any one condition is met, disconnect the isolation cluster contactor. The isolation process ends when both the positive and negative contactors of all isolation clusters are disconnected. If no battery cluster meets the conditions, the isolation process ends directly.

[0086] The multi-cluster battery DC-side switching control method provided in this embodiment employs a judgment logic on the input side that allows operation only when all conditions are met simultaneously. The contactor is closed to connect to the bus only after all input conditions are met, thus mitigating various grid connection risks such as differential voltage, faults, and voltage exceeding limits from the source. On the isolation side, a judgment logic that triggers disconnection upon meeting any condition immediately disconnects the contactor from the bus, eliminating the need to wait for confirmation of multiple faults. This allows for rapid disconnection of abnormal branches in the event of overvoltage, undervoltage, full charge, full discharge, or equipment failure. The input process sequentially checks candidate clusters one by one. Once the first cluster that meets all conditions is detected, the current round of detection is stopped and input is executed immediately, avoiding bus surges caused by parallel input of multiple clusters. The isolation process performs batch checks on all operating clusters, disconnecting all clusters that meet the conditions simultaneously to ensure that all abnormal clusters are disconnected. Through differentiated processing of input-side condition aggregation and isolation-side condition discreteness, the judgment mechanisms for safe access and fault isolation complement each other.

[0087] In one optional implementation, step a2 above includes: Step a21: When any candidate battery cluster meets at least one of the isolation judgment conditions under the corresponding operating condition, the current of the DC bus is limited according to the number of battery clusters currently in operation.

[0088] Step a22: Detect the real-time cluster current of the candidate battery clusters.

[0089] Step a23: Within a preset timeout period, when the real-time cluster current is less than a preset current threshold, disconnect the electrical connection between the candidate battery cluster and the DC bus.

[0090] Step a24: if the real-time cluster current is always greater than or equal to a preset current threshold after a preset timeout, forcibly cut off the electrical connection between the candidate battery cluster and the DC bus.

[0091] Specifically, when any candidate battery cluster triggers an isolation determination condition, the controller does not directly cut off the cluster, but first limits the total current of the DC bus according to the number of battery clusters currently connected to the grid. The purpose of this operation is to pre-reduce the total power output on the bus side before the isolation action is executed, avoiding voltage drop on the load side or output instability of the converter caused by sudden drop of bus current after a cluster suddenly comes out of operation, and creating current conditions for subsequent smooth脱出.

[0092] After completing the current limitation, the controller continuously detects the real-time cluster current value of the cluster to be isolated, and obtains the current magnitude actually flowing through the main contactor of the cluster currently, which is used as a basis for judging whether the electrical disconnection can be safely performed.

[0093] The controller continuously monitors the real-time cluster current of the cluster to be isolated within the preset timeout. When the value is less than the preset current threshold, the positive contactor and negative contactor of the cluster are cut off immediately, so that the cluster is completely disconnected from the DC bus. The purpose of this operation is to ensure that the current flowing through the contact at the moment the contactor is disconnected is at a low level, effectively suppressing the arc phenomenon under load, prolonging the electrical service life of the contactor, and avoiding the impact of reverse electromotive force generated when cutting off large current on bus capacitors and power devices.

[0094] If after the preset timeout, the real-time current of the cluster still does not drop below the preset current threshold, the controller will no longer wait for the current to meet the standard, and forcibly cut off the electrical connection between the cluster and the DC bus. This operation serves as a bottom-up protection path to ensure that the faulty cluster will not be hung on the bus indefinitely because the current cannot drop, and achieves a balance between protecting equipment safety and ensuring timely removal of faults.

[0095] In an example, as Figure 4 shown, a suitable isolation cluster is selected according to the above rules. Calculate the current limiting value: Iclim= Noperation*Itarget, Idlim= Noperation*Itarget.

[0096] Noperation: the number of battery clusters currently in operation; Iclim: cluster charging current limiting value; Idlim: cluster discharging current limiting value; Itarget: isolation voltage reduction target value (30A).

[0097] Cut off the contactors of the isolation clusters, detect the cluster current of each isolation cluster, and start timing. When the cluster current Iisolation cluster of the isolation cluster < Itarget*1.2, immediately cut off the positive and negative contactors of the cluster. If after 10s, the cluster current still does not meet the condition, the positive and negative contactors of the cluster are also cut off.

[0098] The dynamic isolation process ends. The isolation process ends when both the positive and negative contactors of all isolation clusters are disconnected.

[0099] The multi-cluster battery DC-side switching control method provided in this embodiment incorporates a step-by-step processing mechanism in the isolation execution process: current limiting, detection, cut-off upon reaching the threshold, and forced cut-off after timeout. Upon triggering the isolation condition, the total DC bus current is first limited based on the current number of operating clusters, pre-reducing the bus power before the isolation action. This prevents a sudden drop in bus current after a cluster disconnects, which could lead to a voltage drop on the load side or converter output instability, creating current conditions for smooth subsequent disconnection. Based on current limiting, the real-time current of the cluster to be isolated is continuously monitored. The contactor is only disconnected when the current drops below the threshold, ensuring that the current flowing through the contacts is at a low level at the moment of contactor disconnection, preventing the back electromotive force generated during high-current disconnection from impacting the bus capacitor and power devices. For a few non-ideal operating conditions where the current fails to drop below the threshold for an extended period due to converter response lag, uneven output, or sudden load changes, a forced cut-off after a preset timeout is provided as a fallback protection path, ensuring that the faulty cluster does not remain on the bus indefinitely. This achieves a balance between contactor protection and timely fault clearing.

[0100] In an optional implementation, step S201 includes: Step b1: In response to the system power-on command, select a battery cluster whose total voltage value is within a preset differential voltage range from the fault-free battery clusters as the start-up cluster.

[0101] Step b2: Close the precharge circuit of the startup cluster.

[0102] Step b3: When the ratio of the bus voltage of the starting cluster to the total voltage of the corresponding cluster reaches a preset threshold, the starting cluster is taken as the target battery cluster, the corresponding main circuit is closed and the pre-charge circuit is disconnected. The pre-charge circuit is the circuit between the battery cluster and the DC bus for charging the bus voltage, and the main circuit is the circuit between the battery cluster and the DC bus for normal charging and discharging.

[0103] Step b4: When the ratio of the bus voltage of the start cluster to the total voltage of the corresponding cluster does not reach the preset threshold within a preset time period, the corresponding start cluster is shut down.

[0104] Specifically, after the system power-on command is issued, the main control unit of the battery management system initiates the initialization and self-test process. This command is usually triggered manually by the operator or automatically issued by the upper-level energy management system according to the scheduling plan. After receiving the power-on command, the main control unit performs a status scan on all offline battery clusters and filters out fault-free battery clusters. Among the fault-free clusters, the difference between the total voltage value of each cluster and the real-time voltage of the DC bus is further compared. Battery clusters with a total voltage difference within a preset voltage difference range are selected as the start-up clusters, and the cluster with the smallest total voltage difference is selected for priority start-up.

[0105] When the pre-charge circuit of the starting cluster is closed, the main controller sends a closing command to the pre-charge contactor of that cluster. After the pre-charge contactor is turned on, the pre-charge resistor connected in series in the circuit is connected to the electrical path. The resistance value of the pre-charge resistor is usually in the tens of ohms range, used to limit the magnitude of the inrush current during the initial charging phase of the bus capacitor. The bus capacitor is distributed on the DC bus side. In the initial state, the voltage across the capacitor is zero or close to zero. If the main contactor is closed directly, the huge voltage difference between the battery cluster voltage and the zero voltage of the bus capacitor will generate an instantaneous current with an extremely high amplitude. The peak current can reach thousands of amperes, which is enough to weld the contactor contacts or break down the bus capacitor. After the pre-charge circuit is closed, the current flows to the bus capacitor through the pre-charge resistor. The capacitor voltage gradually rises from zero, and the current amplitude is limited by the resistance and remains within a safe range.

[0106] The main controller continuously monitors the DC bus voltage sampling value and calculates the ratio of the bus voltage to the total voltage of the starting cluster. When this ratio reaches a preset threshold, such as 95%, it indicates that the bus capacitor has been charged to near the starting cluster terminal voltage, and the voltage difference between the two has narrowed to a safe range. At this time, the main controller uses the starting cluster as the target battery cluster, closes the corresponding main positive contactor and main negative contactor, and forms a low-impedance power transmission path after the main circuit is connected. Subsequently, the pre-charge contactor is disconnected to remove the pre-charge resistor from the path. The pre-charge resistor only plays a role during the power-on process and does not participate in current conduction under normal operating conditions to avoid additional losses. After the main circuit is connected, the target battery cluster completes the startup process. The target battery clusters that have completed startup form a battery stack, i.e., stack startup. Subsequent battery stacks enter the standby state, waiting for subsequent parallel connection commands or directly participating in power dispatch.

[0107] If the ratio of the bus voltage to the total voltage of the starting cluster fails to reach the preset threshold within a preset time period (e.g., a timeout of three seconds with the ratio only rising to 80% and then stalling), the main controller shuts down the corresponding starting cluster, disconnects its pre-charge contactor, and marks the cluster as a startup failure. This timeout protection logic is based on the integrity of the pre-charge circuit. A slow or stalled rise in bus voltage usually indicates an open circuit in the pre-charge resistor causing a current path interruption, a short circuit on the bus side preventing capacitor voltage establishment, or contactor sticking inside the battery cluster causing the pre-charge circuit to not actually conduct. If the system continues to apply voltage after the timeout without actively shutting down, the pre-charge resistor will heat up due to continuous current flow, potentially burning out the resistor or igniting surrounding components. After shutting down the starting cluster, the system decides whether to attempt to start other candidate clusters based on the fault type. If no other available clusters are found, a startup failure alarm is reported, awaiting manual intervention.

[0108] In one example, such as Figure 5As shown, a suitable starting cluster is selected. Among the fault-free battery clusters, the maximum total voltage Vmax of each cluster is calculated, and the battery cluster whose total voltage VB satisfies Vmax – Vdiff ≤ VB ≤ Vmax is selected, where Vdiff refers to the safe starting voltage difference.

[0109] Initiate pre-charge. Close the negative terminals and pre-charge contactors of all starter clusters. Calculate the pre-charge depth of each starter cluster in real time.

[0110] Precharge depth D = VP / VB * 100%, used for precharge result determination. When the precharge depth D is greater than 95% (precharge depth threshold), precharge is considered successful, the positive contactor of that cluster is closed, and the precharge contactor of that cluster is opened after 0.1s. If the precharge depth cannot be reached after 10s, precharge is considered failed, and the precharge and negative contactors are opened.

[0111] Startup complete. Once all boot clusters have finished pre-charging, the heap startup process ends.

[0112] Stack startup refers to the process from the state where all contactors of the entire battery cluster are open and there is no DC output to the state where the contactors of each cluster are closed and there is DC output. The pre-charge process is as follows: Figure 6 As shown, the battery cells are connected in series to form battery clusters. Each cluster has three contactors: K1 (positive contactor), K2 (negative contactor), and K3 (pre-charge contactor). The DC buses of each battery cluster are directly connected in parallel, forming a pile, which is connected to the DC side bus of the charging and discharging equipment. VB is the total voltage of each battery pack. After the contactors are closed, the total voltage of each cluster will be consistent and no longer distinguished; this is also called the stack voltage. R is the pre-charge resistor. VP is the external voltage, used for DC soft starting, i.e., the determination of pre-charge.

[0113] The DC-side switching control method for multi-cluster batteries provided in this embodiment includes a complete timing control process: selecting starting clusters from fault-free clusters with a total differential voltage within a preset range; closing the pre-charge circuit; monitoring the pre-charge depth and switching to the main circuit after reaching the target and cutting off pre-charge; and actively shutting down if the target is not reached within the time limit. This ensures that the electrical establishment process between the battery cluster and the bus is completed in an orderly manner under current-limiting conditions. By limiting the initial charging current of the bus capacitor through the pre-charge resistor in the circuit, the instantaneous inrush current of thousands of amperes generated when the zero-voltage bus capacitor is directly connected in parallel with the high-voltage battery cluster is avoided, effectively protecting the contactor contacts and bus capacitor from welding or breakdown damage. The judgment logic that the main contactor is closed only after the pre-charge depth reaches the target ensures that the differential voltage on both sides of the main circuit has been reduced to a safe range at the moment the contactor closes, avoiding mechanical shock and electrical arcing caused by hard closing. For non-ideal operating conditions such as open circuit in the pre-charge circuit, short circuit on the bus side, or contactor sticking, a fallback protection mechanism is set up to actively shut down the starting cluster after a preset timeout period. This prevents the pre-charge resistor from burning out due to heat generated by continuous power supply. At the same time, the failed starting cluster is marked and reported, providing status information for subsequent fault diagnosis and retry decisions. The entire starting process, through a three-stage design of pre-charge current limiting, depth determination, and timeout forced shutdown, provides a quantifiable safety boundary for the transition of the battery cluster from being completely offline to being ready for switching.

[0114] In an optional implementation, step S202 includes: Step c1: If the number of target battery clusters is greater than 0, then enter the running state.

[0115] Step c2: If the number of target battery clusters is 0, then remain in the stopped state.

[0116] Step c3: In the running state, identify the current operating condition of the battery system.

[0117] Specifically, such as Figure 7 As shown, after the system powers on, it enters a stop state and executes the stack startup process. If the number of running clusters is greater than 0, it enters the running state; if the number of running clusters is 0, it remains in the stop state. In the running state, the dynamic merging process and the dynamic isolation process are executed. If the number of running clusters is greater than 0, it remains in the running state; if the number of running clusters is 0, it enters the stop state.

[0118] Only when the battery system is in operation can its current operating condition be identified, allowing for subsequent switching steps to proceed.

[0119] The multi-cluster battery DC-side switching control method provided in this embodiment divides the system into a stopped state and a running state at the system state management level. After the startup process is completed, the state transition direction is determined based on the number of battery clusters successfully started. When the number of running clusters is greater than zero, the system enters the running state, enabling it to meet the basic conditions for participating in power scheduling. When the number of running clusters is zero, the system remains in the stopped state to prevent erroneous entry into the running state when there are no available battery clusters, which could lead to the inability to execute scheduling commands and cause system anomalies. In the running state, the dynamic integration and dynamic isolation processes are continuously executed, and the changes in the number of running clusters are monitored in real time. When the last cluster is isolated or removed, the system automatically reverts to the stopped state, realizing closed-loop state management from startup, operation to shutdown. This avoids the control idling and resource waste caused by the system maintaining the running state when there are no battery clusters online, and provides accurate system availability status feedback to the upper-level energy management system. Through the explicit switching conditions between the stopped and running states, the system's startup process, dynamic switching process, and shutdown process logically form a complete closed-loop control chain.

[0120] This embodiment also provides a device for DC-side switching control of multi-cluster batteries, which is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0121] This embodiment provides a method and apparatus for DC-side switching control of multi-cluster batteries, such as... Figure 8 As shown, it includes: Identification module 801 is used to activate several target battery clusters; Operating condition identification module 802 is used to identify the current operating condition of the battery system; The condition configuration module 803 is used to configure the integration judgment condition and / or the isolation judgment condition according to the identified operating conditions. The integration judgment condition is used to determine whether the offline battery cluster is allowed to connect to the DC bus, and the isolation judgment condition is used to determine whether the online battery cluster has triggered the disconnection from the DC bus. The switching module 804 is used to control the switching of several target battery clusters according to the integration determination conditions and the isolation determination conditions.

[0122] The multi-cluster battery DC-side switching control method and apparatus provided in this embodiment of the invention can execute the multi-cluster battery DC-side switching control method provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects for executing the method. Further functional descriptions of the above modules and units are the same as in the corresponding embodiments described above, and will not be repeated here.

[0123] Figure 6 This is a schematic diagram of a DC-side switching control system for multi-cluster batteries provided in an embodiment of the present invention.

[0124] The positive terminals of each battery cluster (multiple clusters 1 in the diagram) are connected in parallel and then connected to the positive terminal of the charging and discharging equipment. The negative terminals of each battery cluster are connected in parallel and then connected to the negative terminal of the charging and discharging equipment. Each battery cluster and the charging and discharging equipment are equipped with an independent electrical switch group. A first switch K1 is installed on the first branch connecting the positive terminal of the battery cluster to the positive terminal of the charging and discharging equipment, and a second switch K2 is installed on the second branch connecting the negative terminal of the battery cluster to the negative terminal of the charging and discharging equipment. When the first and second switches are closed simultaneously, a complete power transmission path is formed between the corresponding battery cluster and the DC bus. When either switch is open, electrical isolation is achieved between the cluster and the bus. In addition, in each first branch, a pre-charge branch is connected in parallel to both ends of the first switch. The pre-charge branch includes a third switch K3 and a pre-charge resistor R connected in series. When the third switch is closed, the current flows through the pre-charge resistor to the bus capacitor, and the current limiting effect of the resistor is used to suppress the inrush current.

[0125] Controller ( Figure 6 (Not shown) establishes communication connections with the first switch, second switch, and third switch respectively to control the closing and opening of each switch. During system operation, the controller executes the multi-cluster battery DC-side switching control method described in any of the foregoing embodiments, including starting the target battery cluster, identifying the operating condition, configuring the integration judgment condition and isolation judgment condition, and controlling the switching action of the corresponding battery cluster according to the judgment result. The specific execution process has been described in detail in the foregoing method embodiments and will not be repeated here.

[0126] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code. When the software or computer code is accessed and executed by the computer, processor, or hardware, it implements the multi-cluster battery DC-side switching control method shown in the above embodiments.

[0127] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0128] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for DC-side switching control of multi-cluster batteries, characterized in that, The multiple battery clusters are connected in parallel to the DC bus, and the method includes: Initiate several target battery clusters; Identify the current operating condition of the battery system; Based on the identified operating conditions, configure an integration determination condition and / or an isolation determination condition. The integration determination condition is used to determine whether the offline battery cluster is allowed to connect to the DC bus, and the isolation determination condition is used to determine whether the online battery cluster triggers disconnection from the DC bus. The switching of the plurality of target battery clusters is controlled according to the incorporation determination condition and the isolation determination condition.

2. The method according to claim 1, characterized in that, The operating conditions include charging, discharging, and idle conditions. The configuration of inclusion and / or isolation judgment conditions based on the identified operating conditions includes: Under the charging condition, the parallel entry determination condition is configured as the first parallel entry condition, and the isolation determination condition is configured as the first isolation condition; Under the discharge condition, the connection determination condition is configured as the second connection condition, and the isolation determination condition is configured as the second isolation condition; In the idle operating condition, the merging determination condition is configured as the third merging condition, and the isolation determination condition is configured as the third isolation condition.

3. The method according to claim 2, characterized in that, The first integration conditions include: the offline battery cluster is fault-free, the offline battery cluster is not fully charged, the charging current limit value of the offline battery cluster is greater than 0, the isolation time of the offline battery cluster is greater than a first preset time, the offline battery cluster has no overvoltage alarm, the total voltage difference between the voltage of the offline battery cluster and the voltage of the online battery cluster is within a preset range, and the highest single-cell voltage of the offline battery cluster is less than a first voltage threshold; the isolation time is the cumulative duration since the offline battery cluster last disconnected from the DC bus; The first isolation conditions include: the online battery cluster has a battery cluster fault, the highest single cell voltage of the online battery cluster is greater than a second voltage threshold, and the online battery cluster is fully charged; wherein, the second voltage threshold is greater than the first voltage threshold.

4. The method according to claim 3, characterized in that, The second inclusion condition includes: The offline battery cluster is fault-free, the offline battery cluster is not fully discharged, the discharge current limit value of the offline battery cluster is greater than 0, the isolation time of the offline battery cluster is greater than the first preset time, the offline battery cluster has no undervoltage alarm, the voltage difference between the offline battery cluster and the online battery cluster is within the preset range, and the lowest single cell voltage of the offline battery cluster is greater than the third voltage threshold. The second isolation conditions include: the online battery cluster has a battery cluster fault, the lowest single cell voltage of the online battery cluster is less than a fourth voltage threshold, and the online battery cluster is fully discharged; wherein, the fourth voltage threshold is less than the third voltage threshold.

5. The method according to claim 4, characterized in that, The third incorporation condition includes: the offline battery cluster is fault-free, the charging and discharging current limit values ​​of the offline battery cluster are not simultaneously 0, the isolation time of the offline battery cluster is greater than the first preset time, the voltage difference between the offline battery cluster and the online battery cluster is within the preset range, and the circulating current prediction condition is met. The circulating current prediction conditions include: if the total voltage of the offline battery cluster is lower than the current DC bus voltage, then the highest single-cell voltage of the offline battery cluster is less than the first voltage threshold, and the lowest single-cell voltage of the online battery cluster is greater than the third voltage threshold. If the total voltage of the offline battery cluster is higher than the current DC bus voltage, then the lowest individual voltage of the offline battery cluster is greater than the third voltage threshold, and the highest individual voltage of the online battery cluster is less than the first voltage threshold. The third isolation condition includes: the online battery cluster has a battery cluster fault, the highest single cell voltage of the online battery cluster is greater than the fifth voltage threshold, and the lowest single cell voltage of the online battery cluster is less than the sixth voltage threshold.

6. The method according to claim 1, characterized in that, The step of controlling the switching of the plurality of target battery clusters according to the incorporation determination condition and the isolation determination condition includes: When any candidate battery cluster simultaneously meets all the connection determination conditions under the corresponding operating conditions, the candidate battery cluster is controlled to be connected to the DC bus. When any candidate battery cluster meets at least one of the isolation determination conditions under the corresponding operating condition, the candidate battery cluster is controlled to disconnect from the DC bus.

7. The method according to claim 6, characterized in that, The step of controlling the candidate battery cluster to disconnect from the DC bus when at least one of the isolation determination conditions under the corresponding operating condition is met includes: When any candidate battery cluster meets at least one of the isolation determination conditions under the corresponding operating condition, the current of the DC bus is limited according to the number of battery clusters currently in operation. Detect the real-time cluster current of the candidate battery clusters; Within a preset timeout period, when the real-time cluster current is less than a preset current threshold, the electrical connection between the candidate battery cluster and the DC bus is cut off. If the real-time cluster current remains greater than or equal to the preset current threshold after the preset timeout period, the electrical connection between the candidate battery cluster and the DC bus will be forcibly disconnected.

8. The method according to claim 1, characterized in that, The activation of several target battery clusters includes: In response to the system power-on command, select the battery cluster whose total voltage value is within the preset differential voltage range from the fault-free battery clusters as the start-up cluster; Close the pre-charge circuit of the startup cluster; When the ratio of the bus voltage of the starting cluster to the total voltage of the corresponding cluster reaches a preset threshold, the starting cluster is used as the target battery cluster, the corresponding main circuit is closed and the pre-charge circuit is disconnected. The pre-charge circuit is a circuit between the battery cluster and the DC bus for charging the bus voltage, and the main circuit is a circuit between the battery cluster and the DC bus for normal charging and discharging. When the ratio of the bus voltage of the startup cluster to the total voltage of the corresponding cluster does not reach the preset threshold within a preset time period, the corresponding startup cluster is shut down.

9. The method according to claim 1, characterized in that, The identification of the current operating status of the battery system includes: If the number of the target battery clusters is greater than 0, then the system enters the running state; If the number of the target battery clusters is 0, then the stop state is maintained; In the operating state, the current operating condition of the battery system is identified.

10. A DC-side switching control device for multi-cluster batteries, characterized in that, The device includes: The identification module is used to activate several target battery clusters; The operating condition identification module is used to identify the current operating condition of the battery system; The condition configuration module is used to configure an integration judgment condition and / or an isolation judgment condition according to the identified operating conditions. The integration judgment condition is used to determine whether the offline battery cluster is allowed to connect to the DC bus, and the isolation judgment condition is used to determine whether the online battery cluster has triggered disconnection from the DC bus. The switching module is used to control the switching of the plurality of target battery clusters according to the incorporation determination condition and the isolation determination condition.

11. A DC-side switching control system for multi-cluster batteries, characterized in that, include: A charging and discharging device, multiple battery clusters, and a controller; the positive terminals of each battery cluster are connected in parallel to the positive terminal of the charging and discharging device, and the negative terminals of each battery cluster are connected in parallel to the negative terminal of the charging and discharging device; a first switch is provided on a first branch connecting the positive terminals of each battery cluster to the positive terminal of the charging and discharging device, and a second switch is provided on a second branch connecting the negative terminals of each battery cluster to the negative terminal of the charging and discharging device; a pre-charge branch is connected in parallel to both ends of the first switch on each first branch, and the pre-charge branch includes a third switch and a pre-charge resistor; the controller is communicatively connected to the first switch, the second switch, and the third switch, and the controller is used to execute the method provided in any one of claims 1-9.

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