A dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration

Abstract

This invention belongs to the field of energy storage backup power supply technology, specifically a dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration. The method generates a voltage step access sequence based on the battery cluster reconfiguration state parameter set and the high-voltage bus pressure-bearing state parameter set. According to the voltage step access sequence, it divides the power supply into a low-voltage parallel holding cluster group and a high-voltage segmented access cluster group. The high-voltage segmented access cluster group is controlled to transition segment by segment from a low-voltage parallel topology to a high-voltage series topology, forming a high-voltage series bus. When the high-voltage series bus reaches the target voltage level, it connects to a high-voltage converter unit to enter a high-voltage backup power supply state, while the low-voltage parallel holding cluster group maintains the low-voltage backup power supply state. This method reduces high-voltage boost surges, decreases the risk of low-voltage critical load power failure, and improves the continuity and security of dual-voltage-level backup power supply.

Description

Technical Field

[0001] This invention belongs to the field of energy storage backup power supply technology, specifically a dual-voltage level backup power supply method based on battery cluster series-parallel reconfiguration. Background Technology

[0002] With increasing demands for continuous backup power from industrial loads, data centers, rail transportation, mining equipment, and critical infrastructure, energy storage backup power systems are gradually evolving from single-voltage-level output to multi-voltage-level adaptability. Traditional backup power solutions typically use low-voltage energy storage power sources connected to high-voltage loads via step-up transformers, or high-voltage energy storage power sources connected to low-voltage loads via step-down transformers. While these solutions are structurally mature, they suffer from drawbacks in scenarios with dual-voltage-level loads, including multiple energy conversion stages, large equipment footprint, limited deployment speed, and insufficient coordination between high and low voltage sides. In recent years, reconfigurable battery energy storage technology has improved the voltage adaptability and battery utilization efficiency of energy storage systems by adjusting the battery cluster connections through switch arrays, cluster-level management units, and power conversion units. However, existing reconfigurable energy storage solutions mostly focus on topology optimization, equalization control, and parallel connection safety of individual battery cells or battery clusters during charging and discharging. They rarely establish segmented boost reconfiguration control mechanisms for application scenarios where 380V low-voltage standby loads and 10kV high-voltage standby loads coexist. In particular, they lack technical solutions that incorporate the residual voltage of the high-voltage bus, insulation pressure state, filter capacitor terminal voltage, and converter input state into the battery cluster connection sequence. This leads to problems such as sudden rise in bus voltage, DC side impact of the converter, increased contactor closing stress, and short-term power loss of critical low-voltage loads when switching from low-voltage parallel topology to high-voltage series topology.

[0003] CN107171387A discloses a dynamically reconfigurable battery energy storage system and method. This scheme generates reconfiguration decisions for the energy storage battery pack based on the electrical information of individual battery cells and power exchange commands through a battery management system, and controls the on / off state of controllable switches, thereby changing the topology of the energy storage battery pack. This is a typical dynamically reconfigurable battery energy storage technology. This scheme can adjust the battery network structure according to battery status and power demand, improving the operational adaptability of the battery energy storage system. However, its focus is on the dynamic reconfiguration of the battery cell or battery pack network structure. It does not address the establishment of low-voltage parallel holding clusters and high-voltage segmented access clusters for 380V and 10kV dual-voltage level backup power supply scenarios, nor does it disclose the formation of a voltage step access sequence based on the high-voltage bus pressure state, and it does not involve the coordinated control process of connecting the high-voltage converter unit after the high-voltage series bus segments are established while simultaneously maintaining low-voltage backup power supply. Therefore, this existing technology struggles to solve the coordination problem between high-voltage bus surges and low-voltage load maintenance during dual-voltage level backup power supply switching.

[0004] CN114977381A discloses a control circuit and method for a multi-cell parallel energy storage system. This scheme collects the status information of corresponding cell clusters through a cell cluster management module, and the system management controller controls the operation of the cell clusters and DC-DC converter based on the aggregated status information. This achieves cell cluster status consistency through energy transfer within the energy storage system, reducing surge current impact between parallel cell clusters. This scheme focuses on differential voltage control and safe integration when multiple cell clusters are connected in parallel, improving the safety and reliability of the parallel energy storage system. However, its technical scope is still limited to the parallel control of multiple cell clusters and does not address the voltage boosting and reconfiguration process of cell clusters transitioning from a low-voltage parallel topology to a high-voltage series topology, nor does it disclose the segmented connection sequence of different cell clusters based on the high-voltage bus pressure status. Therefore, even if this prior art can reduce circulating current between parallel cell clusters, it cannot solve the problems of step voltage boosting, safe integration, and simultaneous maintenance of dual voltage levels when switching from 380V low-voltage backup power to 10kV high-voltage backup power.

[0005] In view of the problems existing in reconfigurable battery energy storage technologies, such as the coarse switching process between low-voltage parallel topology and high-voltage series topology, the lack of participation of high-voltage bus access status in reconfiguration decision-making, and the difficulty in coordinating the maintenance of dual-voltage-level backup loads, this invention is proposed. Therefore, the problem this invention aims to solve is how to generate a voltage step access sequence based on the battery cluster reconfiguration state parameter set and the high-voltage bus pressure state parameter set during the battery cluster series-parallel reconfiguration process, and divide the low-voltage parallel holding cluster group and the high-voltage segmented access cluster group according to the voltage step access sequence. This allows the high-voltage segmented access cluster group to gradually transition into the high-voltage series topology to form a high-voltage series bus, while maintaining the low-voltage backup power supply state when a low-voltage backup power supply request exists and the low-voltage parallel holding cluster group maintains the low-voltage backup power supply state. To address the above problems, this invention provides a dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration, belonging to the technical fields of energy storage backup power supply, battery cluster reconfiguration control, and high- and low-voltage power conversion coordinated control. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration, comprising: Based on the battery cluster reconfiguration state parameter group and the high-voltage bus pressure-bearing state parameter group, a voltage step access sequence is generated; Based on the voltage step access sequence, the battery clusters to be reconfigured are divided into low-voltage parallel holding clusters and high-voltage segmented access clusters; According to the voltage step access sequence, the series-parallel switching module is controlled to operate, so that the high-voltage segmented access cluster is gradually switched from the low-voltage parallel topology to the high-voltage series topology to form a high-voltage series bus. After the high-voltage series bus reaches the target voltage level, the high-voltage series bus is connected to the high-voltage converter unit and enters the high-voltage standby power supply state. When a low-voltage standby power supply request exists and the low-voltage parallel holding cluster maintains the low-voltage standby power supply state, the low-voltage parallel holding cluster maintains the low-voltage standby power supply state.

[0008] The beneficial effects of this invention are as follows: This method generates a voltage step access sequence based on the battery cluster reconfiguration state parameter set and the high-voltage bus pressure-bearing state parameter set. Based on this voltage step access sequence, it divides the system into a low-voltage parallel holding cluster group and a high-voltage segmented access cluster group. The high-voltage segmented access cluster group is controlled to transition segment by segment from a low-voltage parallel topology to a high-voltage series topology, forming a high-voltage series bus. When the high-voltage series bus reaches the target voltage level, it connects to a high-voltage converter unit to enter a high-voltage standby power supply state, which is maintained by the low-voltage parallel holding cluster group. This method reduces high-voltage boost surges, decreases the risk of low-voltage critical load power failure, and improves the continuity and security of dual-voltage-level standby power supply. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0010] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0011] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0012] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0013] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0014] Example 1

[0015] Reference Figure 1 This embodiment provides a dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration, including: S1. Generate a voltage step access sequence based on the battery cluster reconstructed state parameter group and the high-voltage bus pressure-bearing state parameter group. It should be noted that: S1.1 Arrange the cluster terminal voltage, state of charge, internal resistance, and temperature rise of the battery clusters to be reconfigured according to the same battery cluster number to form a battery cluster reconfiguration state parameter group. Arrange the bus residual voltage, high-voltage bus insulation resistance, filter capacitor terminal voltage, and converter DC side input current according to the high-voltage bus electrical position to form a high-voltage bus pressure-bearing state parameter group.

[0016] Specifically, the method for forming the battery cluster reconfiguration state parameter group is as follows: At the same state confirmation time, the cluster terminal voltage, state of charge, internal resistance state, and temperature rise state are obtained for each battery cluster to be reconfigured. Using the battery cluster number as the arrangement basis, the cluster terminal voltage, state of charge, internal resistance state, and temperature rise state belonging to the same battery cluster number are placed in the same parameter row to form the battery cluster reconfiguration state parameter group. The cluster terminal voltage is the voltage between the positive and negative output terminals of the battery cluster to be reconfigured; the state of charge is the current charge ratio given by the battery management unit based on the accumulated charge and discharge capacity and the open-circuit voltage correction; the internal resistance state is the equivalent DC internal resistance level formed by the battery cluster before and after a small current disturbance, and the equivalent DC internal resistance level includes at least a normal internal resistance level, a slightly high internal resistance level, and an abnormal internal resistance level; the temperature rise state is the level of the temperature difference between the highest single-cell temperature in the battery cluster to be reconfigured and the battery compartment inlet air temperature, and the temperature rise state includes at least a normal temperature rise level, a slightly high temperature rise level, and an abnormal temperature rise level. By arranging the same battery clusters by number, the cluster terminal voltage, state of charge, internal resistance, and temperature rise status can be matched one-to-one when selecting subsequent cluster groups, avoiding the neglect of thermal status or internal resistance status when selecting the access object based solely on the cluster terminal voltage.

[0017] In the same preferred embodiment, the method for forming the high-voltage bus pressure-bearing state parameter group is as follows: According to the electrical connection sequence of the high-voltage bus positive terminal, high-voltage bus negative terminal, filter capacitor terminal, and converter DC-side input terminal, the residual voltage of the high-voltage bus, the insulation resistance of the high-voltage bus, the voltage at the filter capacitor terminal, and the DC-side input current of the converter are arranged to form the high-voltage bus pressure-bearing state parameter group. The residual voltage of the bus is the remaining voltage between the positive and negative terminals of the high-voltage series bus before the connection operation; the insulation resistance of the high-voltage bus is the smaller value of the insulation resistance between the positive and negative terminals of the high-voltage series bus and the protective ground; the voltage at the filter capacitor terminal is the voltage across the filter capacitor on the DC side of the high-voltage converter unit; and the DC-side input current of the converter is the instantaneous current at the DC input terminal of the high-voltage converter unit or the current value smoothed by a current sensor.

[0018] For example, the eight battery clusters to be reconfigured are arranged from cluster 1 to cluster 8. Cluster 1 has a cluster terminal voltage of 382V, a state of charge (SOC) of 72%, normal internal resistance, and normal temperature rise. Cluster 2 has a cluster terminal voltage of 379V, a SOC of 70%, normal internal resistance, and normal temperature rise. Cluster 3 has a cluster terminal voltage of 386V, a SOC of 75%, normal internal resistance, and normal temperature rise. Cluster 4 has a cluster terminal voltage of 388V, a SOC of 78%, and normal internal resistance, etc. The temperature rise of the 5th battery cluster is within the normal range; the terminal voltage of the 6th battery cluster is 390V, the state of charge is 82%, the internal resistance is within the normal range, and the temperature rise is within the normal range; the terminal voltage of the 7th battery cluster is 376V, the state of charge is 64%, the internal resistance is within the normal range, and the temperature rise is within the normal range; the terminal voltage of the 8th battery cluster is 381V, the state of charge is 71%, the internal resistance is within the normal range, and the temperature rise is within the normal range. In the high-voltage bus pressure-bearing parameter group, the bus residual voltage is 24V, the high-voltage bus insulation resistance is 3.5MΩ, the filter capacitor terminal voltage is 18V, and the converter DC side input current is 0.6A.

[0019] S1.2. Based on the high-voltage bus pressure-bearing state parameter group, determine the voltage rise of the high-voltage bus to meet the stable connection conditions between adjacent connection operations, and form the bus step pressure-bearing range.

[0020] Specifically, when the voltage difference between the residual voltage of the high-voltage bus and the terminal voltage of the battery cluster to be connected is less than the closing voltage difference limit of the series-parallel switching module, the voltage closing condition is determined to be met. When the insulation resistance of the high-voltage busbar is greater than the insulation resistance limit required for high-voltage backup power supply, the insulation connection condition is deemed to be met. When the voltage difference between the voltage at the end of the filter capacitor and the voltage on the DC side of the converter is less than the limit of the voltage difference at the DC side of the converter, it is determined that the filter capacitor connection condition is met. When the DC input current of the converter is less than the DC connection current limit of the converter, the converter connection condition is deemed to be met. When the voltage closure condition, insulation connection condition, filter capacitor connection condition, and converter connection condition are all met, the voltage rise between adjacent connection actions is classified into the bus step pressure range.

[0021] The method for forming the busbar step-voltage range is as follows: First, based on the high-voltage busbar voltage-bearing state parameter set, it is determined whether the high-voltage busbar is allowed to withstand the next voltage rise under the current electrical state. Then, based on the closing capability of the series-parallel switching module, the DC-side connection capability of the converter, and the voltage-bearing state of the filter capacitor, the allowable voltage rise range between adjacent connection actions is given. The lower limit of the allowable voltage rise range is jointly determined by the minimum voltage build-up requirement of the converter DC side and the charging continuity of the filter capacitor, while the upper limit of the allowable voltage rise range is jointly determined by the closing voltage difference limit of the series-parallel switching module, the insulation class of the high-voltage busbar, and the DC-side connection current limit of the converter.

[0022] Specifically, when forming the bus step-voltage bearing range, the residual voltage of the bus is first compared with the terminal voltage of the battery cluster to be connected. When the voltage difference between the two is less than the closing voltage difference limit of the series-parallel switching module, the contact voltage difference of the series-parallel switching module at the moment of closing is within the allowable range, and the voltage closing condition is met; when the insulation resistance of the high-voltage bus is greater than the insulation resistance limit required for high-voltage backup power supply, the insulation level of the high-voltage bus to ground meets the high-voltage connection requirements, and the insulation connection condition is met; when the voltage difference between the voltage at the filter capacitor terminal and the DC side voltage of the converter is less than the DC side connection voltage difference limit of the converter, there is no excessive charging impact between the filter capacitor terminal and the DC side of the converter, and the filter capacitor connection condition is met; when the DC side input current of the converter is less than the DC side connection current limit of the converter, the DC side of the high-voltage converter unit is not in an abnormal load connection state, and the converter connection condition is met. The voltage rise between adjacent connection actions is classified into the bus step pressure range only when the voltage closure condition, insulation connection condition, filter capacitor connection condition, and converter connection condition are all met simultaneously.

[0023] For example, under the conditions that the closing voltage difference limit of the series-parallel switching module is 45V, the insulation resistance limit is 1.0MΩ, the DC-side input voltage difference limit of the converter is 35V, and the DC-side input current limit of the converter is 5A, the bus residual voltage is 24V, the high-voltage bus insulation resistance is 3.5MΩ, the filter capacitor terminal voltage is 18V, and the DC-side input current of the converter is 0.6A. For the first connection operation, if the equivalent connection voltage corresponding to the cluster to be connected falls within the range of 350V to 410V, then the voltage difference, capacitor charging difference, and DC-side input current of the converter when the series-parallel switching module is closed are all within the allowable range. Therefore, 350V to 410V is determined as the bus step voltage bearing range for the first connection operation. For the second connection operation, under the conditions that the high-voltage bus voltage reaches 382V after the first connection, the voltage at the filter capacitor terminal rises to 376V, the high-voltage bus insulation resistance is 3.2MΩ, and the DC side input current of the converter is 1.1A, if the voltage increment of the next cluster falls within the range of 360V to 420V, then 360V to 420V is determined as the bus step voltage bearing range for the second connection operation.

[0024] S1.3. Based on the battery cluster reconfiguration state parameter group, determine the cluster voltage increment generated when the battery cluster to be reconfigured is connected in series, and form candidate step clusters.

[0025] The specific method for forming candidate step-recharge clusters is as follows: From the battery cluster reconfiguration state parameter group, select battery clusters whose internal resistance state, temperature rise state, and charge state can support the backup power supply duration, and which are eligible for series connection. Then, based on the principles of similar cluster terminal voltage and similar charge state, form candidate step-recharge clusters. The cluster voltage increment is the increase in high-voltage bus voltage caused by connecting the candidate step-recharge cluster to the high-voltage series topology. When a candidate step-recharge cluster includes one battery cluster to be reconfigured, the cluster voltage increment corresponds to the cluster terminal voltage of that battery cluster. When a candidate step-recharge cluster includes multiple battery clusters to be reconfigured, the cluster voltage increment corresponds to the series voltage of the multiple battery clusters to be reconfigured.

[0026] For example, among the aforementioned eight battery clusters to be reconfigured, the internal resistance of the fifth battery cluster is at a relatively high level, but has not yet reached an abnormal level; the temperature rise of the sixth battery cluster is at a relatively high level, but has not yet reached an abnormal level. If the high-voltage backup power supply duration requirement is 20 minutes, and the state of charge of the fifth battery cluster is 61%, which still meets the minimum state of charge requirement of 55%, then battery clusters 1 through 8 can all be included in the candidate range. Based on the principle of similar cluster terminal voltages, a first candidate step-limit cluster group can be formed, comprising the first battery cluster, with a cluster voltage increment of 382V; a second candidate step-limit cluster group can be formed, comprising the second battery cluster, with a cluster voltage increment of 379V; a third candidate step-limit cluster group can be formed, comprising the third battery cluster, with a cluster voltage increment of 386V; and a fourth candidate step-limit cluster group can be formed, comprising the fourth battery cluster, with a cluster voltage increment of 388V. For a high-voltage series bus with a target voltage level of 1500V, a candidate step-limit cluster group consisting of four single-cluster step-limits can be preferentially formed, so that each voltage rise is close to 380V to 390V, reducing the bus voltage surge caused by a single high-voltage connection operation.

[0027] S1.4 Match the cluster voltage increment of the candidate step cluster group with the step pressure range of the bus, and eliminate the candidate step cluster groups whose cluster voltage increment exceeds the step pressure range of the bus to obtain the accessible step cluster groups.

[0028] The matching methods between the cluster voltage increment of candidate step clusters and the bus step voltage bearing range include: When the voltage increment of a candidate step cluster group is within the bus step pressure range, the candidate step cluster group is determined as a step cluster group that can be connected. When the voltage increment of the candidate step-jump cluster group is greater than the upper limit of the bus step-jump pressure range, the battery cluster with the highest cluster terminal voltage to be reconfigured is removed from the candidate step-jump cluster group, and the voltage increment of the candidate step-jump cluster group is redefined. When the voltage increment of the candidate step-jump cluster group is less than the lower limit of the bus step-jump pressure range, the battery cluster with the lowest cluster terminal voltage and in an unconnected state is added to the candidate step-jump cluster group, and the voltage increment of the candidate step-jump cluster group is re-determined. When the voltage increment of the candidate step cluster group after re-determining is within the bus step pressure range, the candidate step cluster group after re-determining is determined as an accessible step cluster group.

[0029] The matching method between candidate step voltage clusters and the bus step voltage bearing range is as follows: Candidate step voltage clusters are selected one by one, and the cluster voltage increment of each candidate step voltage cluster is compared with the bus step voltage bearing range corresponding to the current access action. When the cluster voltage increment is within the bus step voltage bearing range, the candidate step voltage cluster is determined as an accessible step voltage cluster. When the cluster voltage increment is greater than the upper limit of the bus step voltage bearing range, it indicates that the candidate step voltage cluster will cause an excessive voltage step in this access action. In this case, the battery cluster with the highest terminal voltage to be reconfigured is removed from the candidate step voltage cluster, and the cluster voltage increment of the candidate step voltage cluster is redefined. When the cluster voltage increment is less than the lower limit of the bus step voltage bearing range, it indicates that the voltage rise of the candidate step voltage cluster is insufficient in this access action, making it difficult to meet the high-voltage bus segmented voltage building requirements. In this case, the battery cluster with the lowest terminal voltage and currently not accessed is added to the candidate step voltage cluster, and the cluster voltage increment of the candidate step voltage cluster is redefined. The redefined candidate step clusters are compared with the bus step pressure range again. If the voltage increment of the cluster is within the bus step pressure range, the redefined candidate step cluster is determined as an accessible step cluster. If it still exceeds the bus step pressure range, the adjustment is continued in the above removal or addition method until the voltage increment of the candidate step cluster falls into the bus step pressure range, or there are no adjustable unaccessed battery clusters to be reconfigured.

[0030] For example, if the bus step voltage range for the first connection operation is 350V to 410V, and the voltage increment of the first candidate step cluster group is 382V, which falls within the 350V to 410V range, then the first candidate step cluster group is determined as the first connectable step cluster group. If a candidate step cluster group includes a first battery cluster and a second battery cluster, and the voltage increment is 761V, exceeding 410V, then the first battery cluster with the higher terminal voltage is removed. The remaining second battery cluster has a voltage increment of 379V, and the redefined voltage increment falls within the 350V to 410V range. The redefined candidate step cluster group is then determined as the connectable step cluster group. If the voltage increment of a candidate step cluster group is 300V, which is lower than 350V, then the fifth battery cluster with the lowest terminal voltage that is not connected is added. When the voltage increment of the redefined cluster group reaches 673V, which exceeds 410V, the cluster with the highest terminal voltage is removed, until a usable step cluster group that falls within the bus step pressure range is formed. If a usable step cluster group that falls within the bus step pressure range cannot be formed, then the candidate step cluster group will not participate in this round of high-voltage series topology connection.

[0031] S1.5 Arrange the accessible step clusters in order of increasing cluster voltage increment, and generate a voltage step access sequence.

[0032] The method for generating the voltage step access sequence is as follows: After obtaining multiple accessible step clusters, the voltage increment of the accessible step clusters is used as the first arrangement criterion, the temperature rise state of the battery clusters to be reconfigured in the accessible step clusters is used as the second arrangement criterion, and the state of charge of the battery clusters to be reconfigured in the accessible step clusters is used as the third arrangement criterion, thus forming the voltage step access sequence. The first arrangement criterion is to arrange the cluster voltage increments from low to high, so that the high-voltage bus first withstands a smaller voltage step and then gradually transitions to a higher voltage step. When the cluster voltage increments of two accessible step clusters are similar, the accessible step cluster with the lower temperature rise state is prioritized. When both the cluster voltage increments and temperature rise states of two accessible step clusters are similar, the accessible step cluster with the higher state of charge is prioritized. Therefore, the voltage step access sequence not only reflects the voltage rise order, but also reflects the thermal state and power supply carrying capacity of each accessible step cluster.

[0033] For example, four step-adjustable clusters were ultimately obtained: the cluster voltage increment corresponding to the second battery cluster is 379V, the cluster voltage increment corresponding to the eighth battery cluster is 381V, the cluster voltage increment corresponding to the first battery cluster is 382V, and the cluster voltage increment corresponding to the third battery cluster is 386V. Arranged from low to high according to the cluster voltage increment, the generated voltage step-adjustment sequence is the second battery cluster, the eighth battery cluster, the first battery cluster, and the third battery cluster. After high-voltage series topology access according to the voltage step-adjustment sequence, the high-voltage bus voltage rises sequentially to approximately 379V, 760V, 1142V, and 1528V, meeting the high-voltage series bus voltage build-up requirement of a target voltage level of 1500V.

[0034] Furthermore, the system can trigger sequence rearrangement when the high-voltage bus voltage or battery cluster state changes abruptly (SOC, internal resistance, temperature), recalculate the next access cluster order, and ensure that each step access is still within the pressure range; and before access, limited pre-charge control is performed on the filter capacitor to prevent excessive voltage difference; if the voltage difference is too small, delayed closing or gradual charging is allowed to reduce the inrush current.

[0035] It should be noted that before switching the battery clusters from a low-voltage parallel topology to a high-voltage series topology, the connection sequence is determined based on the state of the battery clusters to be reconfigured and the voltage-bearing state of the high-voltage bus. Step S1 addresses the technical problem that, during the switching process of dual-voltage standby power supply, directly connecting the battery clusters in series based solely on their number or voltage level can easily lead to sudden voltage spikes on the bus, contact impacts on switching branches, charging impacts on filter capacitors, and abnormal currents on the DC side of the converter. By matching the constraints between the battery cluster reconfiguration state parameter group, the high-voltage bus voltage-bearing state parameter group, the bus step voltage-bearing range, and the connectable step cluster groups, the voltage rise of each connection action is made compatible with the current voltage-bearing capacity of the high-voltage bus, reducing the voltage build-up impact on the high-voltage bus and improving the electrical stability of the series-parallel switching process.

[0036] S2. Based on the voltage step access sequence, the battery clusters to be reconfigured are divided into low-voltage parallel-maintained clusters and high-voltage segmented access clusters. It should be noted that: S2.1. Based on the voltage step access sequence, determine the battery clusters to be reconfigured in the high-voltage series topology, and use the battery clusters to be reconfigured in the high-voltage series topology as high-voltage candidate battery clusters.

[0037] The specific method for determining high-voltage candidate battery clusters is as follows: Based on the voltage step access sequence, battery clusters that have been included in the accessible step cluster group and participate in the voltage build-up at the target voltage level are extracted and designated as high-voltage candidate battery clusters. If a battery cluster to be reconfigured is in a usable state but has not been included in the voltage step access sequence, or if its internal resistance state, temperature rise state, or state of charge does not meet the requirements for high-voltage series access, then that battery cluster to be reconfigured will not be included in the high-voltage candidate battery clusters.

[0038] For example, among the aforementioned eight battery clusters to be reconfigured, the voltage step access sequence includes battery cluster 2, battery cluster 8, battery cluster 1, and battery cluster 3 in sequence. Therefore, battery cluster 2, battery cluster 8, battery cluster 1, and battery cluster 3 are identified as high-voltage candidate battery clusters. Battery cluster 4, battery cluster 5, battery cluster 6, and battery cluster 7 did not enter the voltage step access sequence, and therefore are not considered as high-voltage candidate battery clusters for this high-voltage series topology voltage establishment.

[0039] S2.2 Based on the access position of the high-voltage candidate battery cluster in the voltage step access sequence, the high-voltage candidate battery cluster is divided into several high-voltage segmented access cluster groups.

[0040] The specific method for dividing high-voltage segmented access clusters is as follows: Based on the access position of high-voltage candidate battery clusters in the voltage step access sequence, high-voltage candidate battery clusters corresponding to adjacent access positions are divided into several high-voltage segmented access clusters. Each high-voltage segmented access cluster corresponds to one series-parallel switching operation and is associated with one series-side switching branch and one parallel-side switching branch. If multiple high-voltage candidate battery clusters are allowed to access a certain bus step-pressure section, then multiple high-voltage candidate battery clusters can be assigned to the same high-voltage segmented access cluster; if only a single high-voltage candidate battery cluster is allowed to access a bus step-pressure section, then each high-voltage segmented access cluster includes only one high-voltage candidate battery cluster.

[0041] For example, if the target voltage level is 1500V, and the allowable voltage rise on the high-voltage bus is 350V to 410V each time, with the voltage step connection sequence being the 2nd battery cluster, the 8th battery cluster, the 1st battery cluster, and the 3rd battery cluster, then it can be divided into four high-voltage segmented connection clusters: the 1st high-voltage segmented connection cluster, the 2nd high-voltage segmented connection cluster, the 3rd high-voltage segmented connection cluster, and the 4th high-voltage segmented connection cluster. The 1st high-voltage segmented connection cluster includes the 2nd battery cluster, the 2nd high-voltage segmented connection cluster includes the 8th battery cluster, the 3rd high-voltage segmented connection cluster includes the 1st battery cluster, and the 4th high-voltage segmented connection cluster includes the 3rd battery cluster. Each high-voltage segmented connection cluster corresponds to one low-voltage parallel disconnection operation and one high-voltage series connection operation.

[0042] S2.3. The battery clusters that have not entered the high-voltage segmented access cluster group and are in a parallel connection state are classified into low-voltage parallel connection holding cluster groups.

[0043] The specific method for dividing low-voltage parallel-maintaining battery clusters is as follows: Among all the battery clusters to be reconfigured, high-voltage candidate battery clusters that have already entered the high-voltage segmented access clusters are excluded. The remaining battery clusters that are still connected to the low-voltage parallel bus and have not been disconnected from the parallel power supply are divided into low-voltage parallel-maintaining clusters. The low-voltage parallel-maintaining clusters do not participate in the high-voltage series bus voltage build-up. Their function is to continue to support the DC input of the low-voltage inverter unit, so that the low-voltage standby load does not lose power due to battery cluster reconfiguration during the high-voltage voltage build-up period.

[0044] For example, among the eight battery clusters to be reconfigured, if battery clusters 2, 8, 1, and 3 are assigned to the high-voltage segmented access cluster group, then battery clusters 4, 5, 6, and 7 remain in a low-voltage parallel connection state. If the terminal voltages of battery clusters 4, 5, 6, and 7 are all within the range of 370V to 390V, and the low-voltage parallel bus is in a normal power supply state, then battery clusters 4, 5, 6, and 7 are classified as a low-voltage parallel holding cluster group.

[0045] S2.4. Based on the voltage difference between the cluster terminal voltage of the low-voltage parallel holding cluster and the input voltage of the low-voltage inverter unit, determine whether the low-voltage parallel holding cluster maintains a low-voltage standby power supply state.

[0046] The specific method for determining whether a low-voltage parallel holding cluster retains its low-voltage standby power supply status is as follows: After dividing the low-voltage parallel holding cluster, first obtain the equivalent parallel terminal voltage of the low-voltage parallel holding cluster, and then calculate the difference between this voltage and the input voltage of the low-voltage inverter unit to obtain the low-voltage access voltage difference. The equivalent parallel terminal voltage can be the balanced voltage of each battery cluster to be reconfigured in the low-voltage parallel holding cluster, or the actual voltage between the positive and negative terminals of the low-voltage parallel bus. If the low-voltage access voltage difference is less than the allowable access voltage difference of the low-voltage inverter unit, it indicates that there is no excessive access voltage deviation between the low-voltage parallel holding cluster and the low-voltage inverter unit, and the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is retained. If the low-voltage access voltage difference is greater than or equal to the allowable access voltage difference of the low-voltage inverter unit, it indicates that overvoltage or undervoltage access may occur on the DC side of the low-voltage inverter unit, and the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is disconnected, and power supply to the low-voltage standby load is stopped.

[0047] For example, the low-voltage parallel holding cluster includes battery clusters 4, 5, 6, and 7. After equalization, the low-voltage parallel bus voltage is 381V, the low-voltage inverter unit input voltage is 380V, and the allowable voltage difference for the low-voltage inverter unit is 20V. Since the low-voltage input voltage difference is 1V, which is less than 20V, the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is maintained. If, under another operating condition, the low-voltage parallel bus voltage drops to 350V, the low-voltage inverter unit input voltage is 380V, and the low-voltage input voltage difference is 30V, which is greater than 20V, then the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is disconnected.

[0048] Furthermore, while maintaining low-voltage power supply, the low-voltage holding clusters simultaneously monitor SOC, internal resistance, and temperature rise; if any abnormality is detected, the discharge current is disconnected or limited according to priority; if a high-voltage connection fails, the connected clusters can be retained or partially returned to low-voltage parallel connection to support subsequent connection operations and reduce the risk of system failure.

[0049] S2.5 When the low-voltage parallel connection group maintains a low-voltage standby power supply state, the access sequence of the high-voltage segmented access group shall be determined according to the voltage step access sequence.

[0050] The methods for determining whether a low-voltage parallel holding cluster maintains a low-voltage standby power supply state include: The difference between the cluster terminal voltage of the low-voltage parallel holding cluster and the input voltage of the low-voltage inverter unit is calculated to obtain the low-voltage access voltage difference. When the low-voltage access voltage difference is less than the allowable access voltage difference of the low-voltage inverter unit, the parallel power supply connection between the low-voltage parallel maintenance cluster and the low-voltage inverter unit is maintained. When the low-voltage access voltage difference is greater than or equal to the allowable access voltage difference of the low-voltage inverter unit, the parallel power supply connection between the low-voltage parallel maintenance cluster and the low-voltage inverter unit is disconnected.

[0051] The specific method for determining the access sequence of high-voltage segmented access clusters is as follows: When the low-voltage parallel maintenance cluster can continue to supply power to the low-voltage inverter unit, the first access action, the second access action, the third access action, and subsequent access actions are determined sequentially according to the arrangement position of each high-voltage segmented access cluster in the voltage step access sequence. If the low-voltage parallel maintenance cluster cannot maintain the low-voltage standby power supply state, the issuance of the access sequence for the high-voltage segmented access cluster is suspended, and the low-voltage standby power supply state is first disconnected or bypassed to avoid the simultaneous occurrence of high-voltage voltage build-up and low-voltage abnormal parallel power supply.

[0052] For example, the low-voltage parallel connection maintains a low-voltage access voltage difference of 1V, which is less than 20V, so the low-voltage parallel connection maintains a low-voltage standby power supply state. At this time, according to the voltage step access sequence, the first high-voltage segment access cluster corresponding to the second battery cluster is determined as the first access target, the second high-voltage segment access cluster corresponding to the eighth battery cluster is determined as the second access target, the third high-voltage segment access cluster corresponding to the first battery cluster is determined as the third access target, and the fourth high-voltage segment access cluster corresponding to the third battery cluster is determined as the fourth access target.

[0053] It should be noted that the same batch of battery clusters to be reconfigured are clearly grouped according to high-voltage power-up tasks and low-voltage backup power supply tasks. This allows some battery clusters to undertake segmented power-up of the high-voltage series bus, while others continue to supply power to the low-voltage inverter unit. Step S2 addresses the technical problem that during the dual-voltage level backup power supply switching process, if all battery clusters simultaneously exit the low-voltage parallel bus, it will cause a short-term power outage of the low-voltage backup load; if all battery clusters remain in the low-voltage parallel topology, a high-voltage series bus cannot be established. By dividing the high-voltage segmented access clusters and maintaining the low-voltage parallel clusters, the high-voltage backup power supply power-up process and the low-voltage backup power supply process can coexist, reducing the risk of power interruption during the dual-voltage level backup power supply switching.

[0054] S3. Following the voltage step access sequence, control the series-parallel switching module to operate, gradually switching the high-voltage segmented access cluster from a low-voltage parallel topology to a high-voltage series topology, forming a high-voltage series bus. This step requires explanation: S3.1. According to the voltage step access sequence, determine the high-voltage segmented access cluster group that is currently connected, and disconnect the parallel connection between the high-voltage segmented access cluster group and the low-voltage parallel bus.

[0055] The specific method for determining the currently accessed high-voltage segmented access clusters and disconnecting their parallel connections is as follows: Starting from the first position of the voltage step access sequence, obtain the high-voltage segmented access cluster corresponding to the current access position, and verify that the high-voltage segmented access cluster is still in the low-voltage parallel bus connection state. After verification, first send a disconnection control signal to the parallel-side switching branch corresponding to the high-voltage segmented access cluster to disconnect the high-voltage segmented access cluster from the low-voltage parallel bus; then check the contact status of the parallel-side switching branch, and after confirming that the parallel-side switching branch is in the disconnected state, the high-voltage segmented access cluster enters the waiting-for-series access state.

[0056] For example, the first position in the voltage step access sequence corresponds to the first high-voltage segment access cluster group corresponding to the second battery cluster. Before access, the first high-voltage segment access cluster group is connected to the low-voltage parallel bus, which has a voltage of 381V. The control unit first disconnects the parallel-side switching branch corresponding to the second battery cluster. After the auxiliary contact feedback indicates an open state and the parallel-side current drops below 0.2A, it determines that the first high-voltage segment access cluster group has disconnected from the low-voltage parallel bus.

[0057] S3.2 After the high-voltage segmented access cluster is disconnected from the low-voltage parallel bus, close the series-side switching branch corresponding to the high-voltage segmented access cluster so that the high-voltage segmented access cluster is connected to the high-voltage series topology.

[0058] The specific method for closing the series-side switching branch is as follows: After the high-voltage segmented access cluster is disconnected from the low-voltage parallel bus, the polarity relationship between the two ends of the high-voltage segmented access cluster and the access end of the high-voltage series topology is first detected; when the polarity relationship is consistent with the series direction of the high-voltage series topology, the series-side switching branch corresponding to the high-voltage segmented access cluster is then closed. After the series-side switching branch is closed, the positive and negative terminals of the high-voltage segmented access cluster are respectively connected to adjacent series nodes in the high-voltage series topology, making the high-voltage segmented access cluster a voltage step segment in the high-voltage series bus.

[0059] For example, after the second battery cluster disconnects from the low-voltage parallel bus, its cluster terminal voltage is 379V. The control unit detects that the positive terminal of the second battery cluster corresponds to the positive node of the high-voltage series topology, and the negative terminal of the second battery cluster corresponds to the negative node of the high-voltage series topology, indicating correct polarity. Subsequently, the series-side switching branch corresponding to the second battery cluster is closed, and the high-voltage bus voltage rises from 24V to approximately 379V.

[0060] S3.3. Based on the change in high-voltage bus voltage after the high-voltage segmented access cluster is connected, determine whether the high-voltage segmented access cluster has completed this voltage step connection.

[0061] The specific method for determining whether the high-voltage segmented access cluster has completed the current voltage step access is as follows: Before the series-side switching branch is closed, record the voltage of the high-voltage bus before access; after the series-side switching branch is closed, record the voltage of the high-voltage bus after access, and obtain the change in high-voltage bus current and the amplitude of high-voltage bus voltage oscillation. If the actual voltage step corresponding to the voltage difference of the high-voltage bus before and after the high-voltage segmented access cluster is within the range of the cluster voltage increment corresponding to the high-voltage segmented access cluster, then the step voltage condition is satisfied. The range of cluster voltage increment can be determined based on the cluster terminal voltage and voltage sampling allowable error of the high-voltage segmented access cluster, for example, using 5V above and below the cluster terminal voltage of the high-voltage segmented access cluster as the allowable range. If the change in high-voltage bus current is less than the access current change limit of the series-side switching branch, then the step current condition is satisfied. If the amplitude of high-voltage bus voltage oscillation is less than the high-voltage bus voltage oscillation limit, then the step stability condition is satisfied. Only when the step voltage condition, step current condition, and step stability condition are all met simultaneously can it be determined that the high-voltage segmented access cluster has completed this voltage step access.

[0062] For example, the voltage increment of the first high-voltage segment access cluster is 379V, with an allowable range of 374V to 384V. Before the first high-voltage segment access cluster is connected, the high-voltage bus voltage is 24V; after connection, the high-voltage bus voltage is 402V. Therefore, the actual voltage step is 378V, which falls within the range of 374V to 384V, satisfying the step voltage condition. If the high-voltage bus current change is 3.2A, and the connection current change limit of the series-side switching branch is 8A, then the step current condition is satisfied. If the high-voltage bus voltage oscillation amplitude is 6V, and the high-voltage bus voltage oscillation limit is 15V, then the step stability condition is satisfied. Since the step voltage condition, step current condition, and step stability condition are all met, it is determined that the first high-voltage segment access cluster has completed this voltage step connection.

[0063] S3.4 When the high-voltage segmented access cluster completes this voltage step access, determine the next high-voltage segmented access cluster according to the voltage step access sequence, and repeat the steps of disconnecting the parallel connection and closing the series-side switching branch.

[0064] The specific method for determining and repeating the access of the next high-voltage segment access cluster is as follows: After the current high-voltage segment access cluster completes its voltage step access, the next high-voltage segment access cluster is obtained according to the next access position in the voltage step access sequence. The following steps are repeated for the next high-voltage segment access cluster: parallel-side switching branch disconnection, series-side switching branch closure, step voltage condition determination, step current condition determination, and step stability condition determination. If any condition is not met, the access action of subsequent high-voltage segment access clusters is stopped, and the already accessed high-voltage segment access clusters remain in their current safe series state, awaiting manual review or protection logic processing.

[0065] For example, after the first high-voltage segment access cluster completes its voltage step access, the control unit acquires the second high-voltage segment access cluster, namely the eighth battery cluster. Before the eighth battery cluster is connected, the high-voltage bus voltage is 402V; after the eighth battery cluster is connected, the high-voltage bus voltage rises to 781V. If the voltage increment range of the cluster corresponding to the eighth battery cluster is 376V to 386V, the actual voltage step is 379V, and the high-voltage bus current change is 3.6A, with a high-voltage bus voltage oscillation amplitude of 7V, then it is determined that the second high-voltage segment access cluster has completed its voltage step access and continues to the third high-voltage segment access cluster.

[0066] S3.5 When all high-voltage segmented access clusters in the voltage step access sequence are connected to the high-voltage series topology, the connected high-voltage segmented access clusters are connected in series to form a high-voltage series bus.

[0067] The methods for determining whether a high-voltage segmented access cluster has completed this voltage step access include: The voltage difference between the high-voltage bus and the high-voltage segmented access cluster is calculated to obtain the actual voltage step. When the actual voltage step is within the range of the voltage increment of the high-voltage segmented access cluster, it is determined that the step voltage condition is met. When the change in high-voltage bus current is less than the limit of the change in the access current of the series-side switching branch, the step current condition is deemed to be met. When the voltage oscillation amplitude of the high-voltage bus is less than the voltage oscillation limit of the high-voltage bus, the step stability condition is deemed to be met. When the step voltage condition, step current condition, and step stability condition are all met, it is determined that the high-voltage segmented access cluster has completed this voltage step access.

[0068] The specific method for forming the high-voltage series bus is as follows: After all high-voltage segmented access clusters in the voltage step access sequence have completed voltage step access, the status of each closed series-side switching branch and each open parallel-side switching branch are confirmed. Once it is confirmed that each high-voltage segmented access cluster has disconnected from the low-voltage parallel bus and has been connected to the high-voltage series topology, the connected high-voltage segmented access clusters are connected in series according to the arrangement order of the voltage step access sequence to form the high-voltage series bus. After the high-voltage series bus is formed, the bus voltage, high-voltage bus insulation resistance, and high-voltage bus voltage oscillation amplitude of the high-voltage series bus are detected to provide a basis for subsequent connection of high-voltage converter units.

[0069] For example, after the first, second, third, and fourth high-voltage segment access clusters are connected sequentially, the high-voltage bus voltages reach 402V, 781V, 1163V, and 1549V respectively. Considering the initial residual bus voltage is 24V, the effective voltage build-up of the high-voltage series bus corresponds to the cluster voltage increments of the four high-voltage segment access clusters. At this point, all parallel-side switching branches are open, and all series-side switching branches are closed, thus forming the high-voltage series bus.

[0070] Furthermore, the series-parallel switching module can be equipped with contactors / IGBTs with dead time, circulating current suppression and redundant logic, and fuses or instantaneous overcurrent protection can be installed on the bus to ground and series-parallel sides.

[0071] It should be noted that the high-voltage segmented access clusters are switched segment by segment according to the voltage step access sequence, so that the battery clusters to be reconfigured can be orderly transferred from the low-voltage parallel topology to the high-voltage series topology. The technical problem solved by step S3 is that if multiple battery clusters are simultaneously disconnected from the low-voltage parallel bus and connected to the high-voltage bus in series at once, it is easy to cause contactor contact impact, bus current sudden change, high-voltage bus voltage oscillation and short-term topology uncertainty. By first disconnecting the parallel connection, then closing the series-side switching branch, and then confirming the segmentation according to the step voltage condition, step current condition and step stability condition, the access action of each high-voltage segmented access cluster group has an independent electrical closed-loop judgment, reducing the inrush current and bus oscillation during the series-parallel topology switching, and improving the reliability of the high-voltage series bus formation process.

[0072] S4. After the high-voltage series bus reaches the target voltage level, the high-voltage series bus is connected to the high-voltage converter unit and enters the high-voltage standby power supply state. When a low-voltage standby power supply request exists and the low-voltage parallel holding group maintains the low-voltage standby power supply state, the low-voltage parallel holding group maintains the low-voltage standby power supply state. It should be noted that: S4.1. Based on the bus voltage and target voltage level of the high-voltage series bus, determine whether the high-voltage series bus meets the connection conditions of the high-voltage converter unit.

[0073] The specific method for determining whether a high-voltage series bus meets the connection conditions for a high-voltage converter unit is as follows: After the high-voltage series bus is formed, the bus voltage of the high-voltage series bus is obtained and compared with the target voltage level. When the bus voltage of the high-voltage series bus is within the allowable DC input range of the target voltage level, and the insulation resistance of the high-voltage bus is still greater than the insulation resistance limit, and the oscillation amplitude of the high-voltage bus voltage is less than the oscillation limit of the high-voltage bus voltage, the high-voltage series bus is determined to meet the connection conditions for a high-voltage converter unit. The allowable DC input range of the target voltage level can be determined based on the DC input range of the high-voltage converter unit. For example, when the target voltage level is 1500V, the allowable DC input range can be set to 1450V to 1600V.

[0074] For example, the bus voltage after the high-voltage series busbar is formed is 1549V, the target voltage level is 1500V, and the allowable DC input range is 1450V to 1600V; the high-voltage busbar insulation resistance is 3.1MΩ, which is greater than 1.0MΩ; and the high-voltage busbar voltage oscillation amplitude is 8V, which is less than 15V. If all the above conditions are met simultaneously, the high-voltage series busbar is deemed to meet the connection conditions for the high-voltage converter unit.

[0075] S4.2 When the high-voltage series bus meets the connection conditions of the high-voltage converter unit, close the DC side connection branch between the high-voltage series bus and the high-voltage converter unit.

[0076] The specific method for closing the DC-side access branch is as follows: When the high-voltage series bus meets the access conditions of the high-voltage converter unit, the DC-side control state of the high-voltage converter unit is first set to the waiting-to-access state, so that the high-voltage converter unit does not output power to the AC side; then, the DC-side access branch between the high-voltage series bus and the high-voltage converter unit is closed, so that the high-voltage series bus is connected to the DC input terminal of the high-voltage converter unit. After closing the DC-side access branch, the DC-side input current of the converter and the voltage at the end of the filter capacitor are detected; when the DC-side input current of the converter is less than the DC-side access current limit and the voltage at the end of the filter capacitor is close to the bus voltage of the high-voltage series bus, the AC-side output adjustment stage of the high-voltage converter unit is entered.

[0077] For example, the bus voltage of the high-voltage series bus is 1549V, and the allowable input range of the DC side of the high-voltage converter unit is 1450V to 1600V. Before closing the DC side connection branch, the high-voltage converter unit is in a ready-to-connect state. After closing the DC side connection branch, the DC side input current of the converter is 2.8A, which is less than 5A; the voltage at the filter capacitor terminal rises from 1510V to 1542V, and the difference between the voltage at the filter capacitor and the bus voltage of the high-voltage series bus is 7V, which is less than 35V, thus entering the AC side output adjustment stage.

[0078] S4.3. Based on the AC side voltage, AC side frequency and harmonic content of the high-voltage converter unit, determine whether the high-voltage converter unit meets the high-voltage backup power supply access conditions.

[0079] The specific method for determining whether a high-voltage converter unit meets the high-voltage standby power supply access conditions is as follows: After the high-voltage converter unit is connected to the high-voltage series bus, the high-voltage converter unit first establishes an AC side no-load output, and then obtains the AC side voltage, AC side frequency, and harmonic content of the high-voltage converter unit. The AC side voltage is compared with the rated voltage of the high-voltage standby load. If the AC side voltage is within the allowable fluctuation range of the rated voltage of the high-voltage standby load, the high-voltage voltage access condition is met. The AC side frequency is compared with the rated frequency of the high-voltage standby load. If the AC side frequency is within the allowable fluctuation range of the rated frequency of the high-voltage standby load, the high-voltage frequency access condition is met. The harmonic content is compared with the harmonic limit required for high-voltage standby load access. If the harmonic content is not greater than the harmonic limit, the high-voltage harmonic access condition is met. Only when the high-voltage voltage access condition, high-voltage frequency access condition, and high-voltage harmonic access condition are all met simultaneously is the high-voltage converter unit determined to meet the high-voltage standby power supply access conditions.

[0080] For example, the rated voltage of the high-voltage standby load is 690V, with an allowable fluctuation range of 655.5V to 724.5V; the rated frequency of the high-voltage standby load is 50Hz, with an allowable fluctuation range of 49.5Hz to 50.5Hz; and the harmonic limit is 5%. After the high-voltage converter unit is unloaded, the AC side voltage is 688V, the AC side frequency is 50.02Hz, and the harmonic content is 2.7%. Since 688V is within the range of 655.5V to 724.5V, and 50.02Hz is within the range of 49.5Hz to 50.5Hz, and 2.7% is not greater than 5%, the high-voltage converter unit is deemed to meet the high-voltage standby power supply access conditions. If the harmonic content is 6.3% under another operating condition, even if the AC side voltage and AC side frequency meet the requirements, the high-voltage converter unit is not deemed to meet the high-voltage standby power supply access conditions.

[0081] S4.4 When the high-voltage converter unit meets the high-voltage standby power supply access conditions, the high-voltage output branch between the high-voltage converter unit and the high-voltage standby load is closed, allowing the high-voltage series bus to enter the high-voltage standby power supply state. The specific method for closing the high-voltage output branch is as follows: After the high-voltage converter unit meets the high-voltage standby power supply access conditions, the switch status on the high-voltage standby load side and the voltage difference across the high-voltage output branch are first detected. If the high-voltage standby load side is in a standby state, and the voltage difference across the high-voltage output branch is less than the allowable closing voltage difference of the high-voltage output branch, then the high-voltage output branch between the high-voltage converter unit and the high-voltage standby load is closed. After closing the high-voltage output branch, the receiving voltage, receiving frequency, and load current of the high-voltage standby load are detected; when the receiving voltage, receiving frequency, and load current are within the allowable range of the high-voltage standby load, the high-voltage series bus enters the high-voltage standby power supply state.

[0082] For example, the AC side voltage of the high-voltage converter unit is 688V, the voltage of the high-voltage standby load side is 0V, the allowable closing voltage difference of the high-voltage output branch is 700V, and the high-voltage standby load side is in a standby power-on state. After closing the high-voltage output branch, the voltage received by the high-voltage standby load is 686V, the power-on frequency is 50.01Hz, and the load current is 43A, all of which are within the allowable range of the high-voltage standby load. Thus, the high-voltage series bus enters the high-voltage standby power supply state.

[0083] S4.5 When a low-voltage standby power supply request exists and the low-voltage parallel holding cluster is in a low-voltage standby power supply state, the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is maintained, and the low-voltage inverter unit supplies power to the low-voltage standby load.

[0084] The methods for determining whether a high-voltage converter unit meets the conditions for high-voltage backup power supply access include: The AC side voltage of the high-voltage converter unit is compared with the rated voltage of the high-voltage standby load. When the AC side voltage is within the allowable fluctuation range of the rated voltage of the high-voltage standby load, it is determined that the high-voltage access conditions are met. The AC side frequency of the high-voltage converter unit is compared with the rated frequency of the high-voltage standby load. When the AC side frequency is within the allowable fluctuation range of the rated frequency of the high-voltage standby load, it is determined that the high-voltage frequency access conditions are met. The harmonic content of the high-voltage converter unit is compared with the harmonic limit required for high-voltage standby load access. If the harmonic content is not greater than the harmonic limit, it is determined that the high-voltage harmonic access conditions are met. When the high voltage access condition, high voltage frequency access condition, and high voltage harmonic access condition are all met, the high voltage converter unit is determined to meet the high voltage backup power supply access condition.

[0085] The method for maintaining the low-voltage standby power supply status is as follows: Simultaneously with the high-voltage series bus entering the high-voltage standby power supply status, a low-voltage standby power supply request is detected, and the low-voltage parallel holding cluster is re-verified to ensure it still meets the low-voltage standby power supply status determination conditions. When a low-voltage standby power supply request exists, and the low-voltage access voltage difference of the low-voltage parallel holding cluster is still less than the allowable access voltage difference of the low-voltage inverter unit, the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is maintained, and the low-voltage inverter unit supplies power to the low-voltage standby load. When a low-voltage standby power supply request does not exist, the low-voltage inverter unit does not output power to the low-voltage standby load; when a low-voltage standby power supply request exists but the low-voltage parallel holding cluster does not meet the low-voltage standby power supply status determination conditions, the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is disconnected.

[0086] For example, the low-voltage standby load consists of a communication control cabinet and a lighting circuit, with a rated AC voltage of 220V. The DC input voltage of the low-voltage inverter unit is 380V. The low-voltage parallel holding cluster consists of battery clusters 4, 5, 6, and 7, with a low-voltage parallel bus voltage of 381V. The low-voltage inverter unit is allowed a voltage difference of 20V. At this time, a low-voltage standby power supply request exists, and the low-voltage input voltage difference is 1V. Therefore, the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is maintained, and the low-voltage inverter unit outputs 220V AC power to the low-voltage standby load. Simultaneously, the high-voltage series bus supplies power to the 690V high-voltage standby load via the high-voltage converter unit, thus forming a dual-voltage-level standby power supply mode where high-voltage and low-voltage standby power supply states coexist.

[0087] Furthermore, after the high-voltage series busbar is connected to the high-voltage converter unit, the system continuously monitors the busbar voltage, frequency, and harmonics, and triggers overvoltage, undervoltage, overfrequency, and underfrequency protection or load current limiting control according to preset limits. In scenarios where high-voltage 1500V and low-voltage 380V coexist, electrical isolation switches and physical protection isolation zones are set up, and false blocking logic and high-voltage live indication are added to ensure safe and reliable operation and maintenance.

[0088] It should be noted that after the high-voltage series bus reaches the target voltage level, it is converted into a power supply side capable of supplying power to the high-voltage standby load in the order of DC side access, AC side output determination, and high-voltage load access. Simultaneously, the low-voltage parallel maintenance cluster retains its low-voltage power supply capability when a low-voltage standby power supply request exists. The technical problem addressed in step S4 is that the completion of high-voltage series bus voltage establishment does not equate to the high-voltage standby load being directly energized. If the high-voltage output branch is directly closed without determining DC side access conditions, AC side voltage, AC side frequency, and harmonic content, the high-voltage standby load may be subjected to abnormal voltage, abnormal frequency, or harmonic impacts. Through graded determination of high-voltage converter unit access conditions and high-voltage standby power supply access conditions, the DC side state and AC side output state before the high-voltage standby load access are both within acceptable ranges. Simultaneously, the low-voltage parallel maintenance cluster continues to supply power to the low-voltage inverter unit, ensuring that the high-voltage standby load and low-voltage standby load are carried by different topology branches, reducing mutual interference during dual-voltage level standby power supply switching, and improving the continuity and access security of standby power supply.

[0089] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration, characterized in that, include: Based on the battery cluster reconfiguration state parameter group and the high-voltage bus pressure-bearing state parameter group, a voltage step access sequence is generated; Based on the voltage step access sequence, the battery clusters to be reconfigured are divided into low-voltage parallel holding clusters and high-voltage segmented access clusters; According to the voltage step access sequence, the series-parallel switching module is controlled to operate, so that the high-voltage segmented access cluster is gradually switched from the low-voltage parallel topology to the high-voltage series topology to form a high-voltage series bus. After the high-voltage series bus reaches the target voltage level, the high-voltage series bus is connected to the high-voltage converter unit and enters the high-voltage standby power supply state. When a low-voltage standby power supply request exists and the low-voltage parallel holding cluster maintains the low-voltage standby power supply state, the low-voltage parallel holding cluster maintains the low-voltage standby power supply state.

2. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 1, characterized in that, The method for generating the voltage step access sequence includes: The cluster terminal voltage, state of charge, internal resistance, and temperature rise of the battery cluster to be reconfigured are arranged according to the same battery cluster number to form a battery cluster reconfiguration state parameter group. The bus residual voltage, high-voltage bus insulation resistance, filter capacitor terminal voltage, and converter DC side input current are arranged according to the electrical position of the high-voltage bus to form a high-voltage bus pressure-bearing state parameter group. Based on the high-voltage bus pressure-bearing state parameter set, the voltage rise of the high-voltage bus that satisfies the stable connection condition between adjacent connection operations is determined, and the bus step pressure-bearing range is formed. Based on the battery cluster reconfiguration state parameter group, determine the cluster voltage increment generated when the battery cluster to be reconfigured is connected in series, and form a candidate step cluster. The voltage increment of the candidate step cluster group is matched with the step pressure range of the bus, and the candidate step cluster groups whose voltage increment exceeds the step pressure range of the bus are eliminated to obtain the accessible step cluster groups. The accessible step clusters are arranged in ascending order of cluster voltage increment, and a voltage step access sequence is generated.

3. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 2, characterized in that, The stable access conditions include: When the voltage difference between the residual voltage of the high-voltage bus and the terminal voltage of the battery cluster to be connected is less than the closing voltage difference limit of the series-parallel switching module, the voltage closing condition is determined to be met. When the insulation resistance of the high-voltage busbar is greater than the insulation resistance limit required for high-voltage backup power supply, the insulation connection condition is deemed to be met. When the voltage difference between the voltage at the end of the filter capacitor and the voltage on the DC side of the converter is less than the limit of the voltage difference at the DC side of the converter, it is determined that the filter capacitor connection condition is met. When the DC-side input current of the converter is less than the DC-side connection current limit of the converter, it is determined that the converter connection condition is met. When the voltage closing condition, the insulation connection condition, the filter capacitor connection condition, and the converter connection condition are all met, the voltage rise between adjacent connection actions is classified into the bus step pressure range.

4. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 3, characterized in that, The matching method between the cluster voltage increment of the candidate step cluster group and the bus step pressure range includes: When the voltage increment of the candidate step cluster group is within the step pressure range of the bus, the candidate step cluster group is determined as a step cluster group that can be connected. When the cluster voltage increment of the candidate step cluster group is greater than the upper limit of the bus step pressure range, the battery cluster with the highest cluster terminal voltage to be reconfigured is removed from the candidate step cluster group, and the cluster voltage increment of the candidate step cluster group is re-determined. When the cluster voltage increment of the candidate step cluster group is less than the lower limit of the bus step pressure range, a battery cluster with the lowest cluster terminal voltage and in an unconnected state is added to the candidate step cluster group, and the cluster voltage increment of the candidate step cluster group is re-determined. When the voltage increment of the candidate step cluster group after re-determining is within the step pressure range of the bus, the candidate step cluster group after re-determining is determined as an accessible step cluster group.

5. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 4, characterized in that, The method for dividing the low-voltage parallel-maintaining cluster group and the high-voltage segmented access cluster group includes: Based on the voltage step access sequence, the battery clusters to be reconfigured that participate in the high-voltage series topology are determined, and the battery clusters to be reconfigured that participate in the high-voltage series topology are taken as high-voltage candidate battery clusters. Based on the access position of the high-voltage candidate battery cluster in the voltage step access sequence, the high-voltage candidate battery cluster is divided into several high-voltage segmented access cluster groups; The battery clusters to be reconfigured that have not entered the high-voltage segmented access cluster group and are in a parallel connection state are classified into low-voltage parallel connection holding cluster groups. Based on the voltage difference between the cluster terminal voltage of the low-voltage parallel holding cluster and the input voltage of the low-voltage inverter unit, it is determined whether the low-voltage parallel holding cluster maintains a low-voltage standby power supply state. When the low-voltage parallel maintenance cluster group is kept in a low-voltage standby power supply state, the access order of the high-voltage segmented access cluster group is determined according to the voltage step access sequence.

6. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 5, characterized in that, The method for determining whether the low-voltage parallel holding cluster maintains a low-voltage standby power supply state includes: The difference between the cluster terminal voltage of the low-voltage parallel holding cluster and the input voltage of the low-voltage inverter unit is calculated to obtain the low-voltage access voltage difference. When the low-voltage access voltage difference is less than the allowable access voltage difference of the low-voltage inverter unit, the parallel power supply connection between the low-voltage parallel maintenance cluster and the low-voltage inverter unit is maintained. When the low-voltage access voltage difference is greater than or equal to the allowable access voltage difference of the low-voltage inverter unit, the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is disconnected.

7. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 6, characterized in that, The method for forming the high-voltage series busbar includes: According to the voltage step access sequence, determine the high-voltage segmented access cluster group that is currently accessed, and disconnect the parallel connection between the high-voltage segmented access cluster group and the low-voltage parallel bus. After the high-voltage segmented access cluster is disconnected from the low-voltage parallel bus, the series-side switching branch corresponding to the high-voltage segmented access cluster is closed, so that the high-voltage segmented access cluster is connected to the high-voltage series topology. Based on the change in high-voltage bus voltage after the high-voltage segmented access cluster is connected, it is determined whether the high-voltage segmented access cluster has completed this voltage step connection. When the high-voltage segmented access cluster group completes this voltage step access, the next high-voltage segmented access cluster group is determined according to the voltage step access sequence, and the steps of disconnecting the parallel connection and closing the series-side switching branch are repeated. When all the high-voltage segmented access clusters in the voltage step access sequence are connected to the high-voltage series topology, the connected high-voltage segmented access clusters are connected in series to form a high-voltage series bus.

8. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 7, characterized in that, The method for determining whether the high-voltage segmented access cluster has completed this voltage step access includes: The voltage difference of the high-voltage bus before and after the high-voltage segmented access cluster is calculated to obtain the actual voltage step. When the actual voltage step is within the range of the voltage increment of the high-voltage segmented access cluster, it is determined that the step voltage condition is met. When the change in the high-voltage bus current is less than the limit of the change in the access current of the series-side switching branch, it is determined that the step current condition is met. When the voltage oscillation amplitude of the high-voltage bus is less than the voltage oscillation limit of the high-voltage bus, it is determined that the step stability condition is met. When the step voltage condition, the step current condition, and the step stability condition are all met, it is determined that the high-voltage segmented access cluster has completed this voltage step access.

9. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 8, characterized in that, The methods for maintaining the high-voltage backup power supply state and the low-voltage backup power supply state include: Based on the bus voltage and target voltage level of the high-voltage series bus, determine whether the high-voltage series bus meets the access conditions for the high-voltage converter unit; When the high-voltage series bus meets the access conditions of the high-voltage converter unit, the DC side access branch between the high-voltage series bus and the high-voltage converter unit is closed. Based on the AC side voltage, AC side frequency, and harmonic content of the high-voltage converter unit, determine whether the high-voltage converter unit meets the high-voltage backup power supply access conditions; When the high-voltage converter unit meets the high-voltage backup power supply access conditions, the high-voltage output branch between the high-voltage converter unit and the high-voltage backup load is closed, so that the high-voltage series bus enters the high-voltage backup power supply state. When a low-voltage standby power supply request exists and the low-voltage parallel holding cluster is in a low-voltage standby power supply state, the parallel power supply connection between the low-voltage parallel holding cluster and the low-voltage inverter unit is maintained, and the low-voltage inverter unit supplies power to the low-voltage standby load.

10. The dual-voltage-level backup power supply method based on battery cluster series-parallel reconfiguration according to claim 9, characterized in that, The methods for determining whether the high-voltage converter unit meets the conditions for high-voltage backup power supply access include: The AC side voltage of the high-voltage converter unit is compared with the rated voltage of the high-voltage standby load. When the AC side voltage is within the allowable fluctuation range of the rated voltage of the high-voltage standby load, it is determined that the high-voltage access condition is met. The AC side frequency of the high-voltage converter unit is compared with the rated frequency of the high-voltage standby load. When the AC side frequency is within the allowable fluctuation range of the rated frequency of the high-voltage standby load, it is determined that the high-voltage frequency access condition is met. The harmonic content of the high-voltage converter unit is compared with the harmonic limit required for high-voltage standby load access. If the harmonic content is not greater than the harmonic limit, it is determined that the high-voltage harmonic access condition is met. When the high voltage access condition, the high voltage frequency access condition, and the high voltage harmonic access condition are all met, it is determined that the high voltage converter unit meets the high voltage backup power supply access condition.

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