Ship high-voltage battery cluster sequential flexible grid-connected method and system based on voltage balancing
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CSSC SILENT ELECTRIC SYSTEM (WUXI) TECHNOLOGY CO LTD
- Filing Date
- 2026-06-10
- Publication Date
- 2026-07-14
Smart Images
Figure CN122394058A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of parallel power supply control technology for multi-cluster battery packs, and more specifically, to a method and system for sequential flexible grid connection of marine high-voltage battery clusters based on voltage balancing. Background Technology
[0002] In large-capacity energy storage systems on ships, composed of multiple battery clusters connected in parallel, existing technologies typically employ a sequential grid connection control strategy based on a voltage difference threshold to suppress circulating currents caused by voltage imbalances between clusters. This strategy involves real-time monitoring of the voltage difference between each battery cluster and the DC bus or with other grid-connected clusters, comparing this difference to a preset fixed threshold to determine the grid connection sequence and timing of each cluster. For example, when the voltage difference is below the threshold, grid connection proceeds in a predetermined order; when the voltage difference is above the threshold, connection follows a specific voltage priority logic. This method aims to limit inrush currents by controlling the voltage difference at the moment of grid connection and is a common technical means to achieve flexible grid connection of multiple clusters and ensure system safety.
[0003] However, the discrete logic judgment method based on fixed threshold comparison mentioned above will produce frequent jumps and jitters when facing the working scenario of continuous dynamic changes in battery cluster voltage. When the real-time voltage difference between clusters fluctuates continuously around the set threshold, the discrete logic judgment output will produce frequent jumps and jitters. This threshold critical state jitter caused by measurement noise, load changes or system dynamic processes will lead to instability and uncertainty in grid connection sequence control commands. In severe cases, it may cause unexpected contactor actions or control sequence chaos. This not only directly undermines the stability and reliability of the sequential grid connection strategy itself, but may also induce unpredictable transient circulating currents, thereby endangering the safety of battery clusters and power electronic equipment. Ultimately, it makes it difficult to reliably achieve the core objective of anti-circulating current based on voltage difference management. Summary of the Invention
[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method and system for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: The sequential flexible grid connection method for ship high-voltage battery clusters based on voltage equalization includes the following steps: S1. Obtain the terminal voltage and DC bus voltage of each battery cluster to be connected to the grid; S2. Calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and determine whether the voltage difference enters the dynamic threshold range. S3. When the voltage difference enters the dynamic threshold range, monitor the crossing events of the voltage difference in multiple logic sub-intervals within the dynamic threshold range, and accumulate the residence time in each logic sub-interval. S4. Assess the grid connection permit status of the corresponding battery cluster based on the crossing event and dwell time; S5. When the grid connection permit status of multiple battery clusters reaches the preparatory conditions, a coordinated grid connection sequence is generated based on the estimated impact of grid connection operation on the bus voltage and the voltage difference of other battery clusters. S6. Perform grid connection operation for the corresponding battery cluster according to the coordinated grid connection sequence.
[0006] Furthermore, the terminal voltage and DC bus voltage of each battery cluster to be connected to the grid are obtained, including: The terminal voltage and DC bus voltage of each battery cluster to be connected to the grid are sampled in parallel and synchronously. During the sampling process, the voltage value acquired by each sampling channel is subjected to real-time verification based on a preset range; The voltage value obtained from the sampling channel will only be output as a valid terminal voltage or DC bus voltage if the verification passes.
[0007] Further, the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage is calculated, and it is determined whether the voltage difference enters the dynamic threshold range, including: Based on the effective terminal voltage and the effective DC bus voltage, the voltage difference corresponding to each battery cluster is calculated. For each voltage difference, determine whether it falls within the voltage range defined by the dynamic threshold interval; When the voltage difference first enters the voltage range, the time window is activated and timing begins. Only when the voltage difference remains within the voltage range within the time window will the voltage difference be ultimately determined to have entered the dynamic threshold range.
[0008] Furthermore, the dynamic threshold range is dynamically adjusted based on historical statistical values of the effective terminal voltage and the effective DC bus voltage, so that the voltage range can adapt to the long-term voltage change trend of the battery cluster.
[0009] Furthermore, when the voltage difference enters the dynamic threshold range, the system monitors the crossing events of the voltage difference across multiple logic sub-intervals within the dynamic threshold range and accumulates the residence time in each logic sub-interval, including: Based on the distance from the boundary of the dynamic threshold interval, the dynamic threshold interval is divided into boundary sub-intervals and stable sub-intervals; Continuously monitor the instantaneous value of the voltage difference and determine its current logical sub-interval; When the instantaneous value of the voltage difference moves from one logical sub-interval to another, a crossing event is recorded, and the current logical sub-interval is updated. From the moment the instantaneous value of the voltage difference enters the current logic sub-interval, an independent timer for the logic sub-interval is started to continuously accumulate the residence time of the voltage difference in the logic sub-interval.
[0010] Furthermore, the grid connection permit status of the corresponding battery cluster is assessed based on the crossing event and dwell time, including: Analyze the recorded crossing events to determine whether the voltage difference shows a trend of crossing from the boundary sub-interval to the stable sub-interval; Check whether the current cumulative dwell time of the voltage difference within the stable sub-interval has reached the predetermined duration; If the voltage difference shows a trend of crossing from the boundary sub-interval to the stable sub-interval, and the current cumulative residence time in the stable sub-interval reaches the predetermined duration, then the grid connection permit status of the corresponding battery cluster is assessed as allowing grid connection.
[0011] Furthermore, when the grid connection permit status of multiple battery clusters reaches the preparatory conditions, a coordinated grid connection sequence is generated based on the estimated impact of grid connection operation on the bus voltage and the voltage difference of other battery clusters, including: Identify all battery clusters with grid connection permit status of allowed grid connection or ready for grid connection as candidate clusters; For each candidate cluster, based on the current voltage difference between the candidate cluster's terminal voltage and the DC bus voltage, as well as the DC bus voltage itself, the possible direction of change of the DC bus voltage after the grid connection operation is executed is simulated. Based on the possible changes in the DC bus voltage obtained from the simulation, all candidate clusters are classified and sorted to generate a coordinated grid connection sequence that makes the system tend to be stable.
[0012] Furthermore, when generating the coordinated grid connection sequence, the classification and sorting rules are as follows: priority is given to selecting candidate clusters whose possible change direction of the simulated DC bus voltage is to increase the DC bus voltage, and under the same conditions, priority is given to selecting candidate clusters with smaller current voltage differences.
[0013] Furthermore, the grid connection operation of the corresponding battery cluster is performed according to the coordinated grid connection sequence, including: Select the battery clusters to be operated in sequence according to the order indicated by the coordinated grid connection sequence; Before issuing a closing command to the grid-connected switch of the currently selected battery cluster, the current voltage difference between the terminal voltage of the battery cluster and the DC bus voltage is obtained again. Only after confirming that the current voltage difference is still within the dynamic threshold range and that the grid connection permit status of the corresponding battery cluster has not been updated to prohibit switching, will the operation of issuing a closing command be executed.
[0014] On the other hand, the present invention provides a sequential flexible grid connection system for ship high-voltage battery clusters based on voltage equalization, comprising the following modules: The voltage acquisition module is used to acquire the terminal voltage of each battery cluster to be connected to the grid and the DC bus voltage; The difference judgment module is used to calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and to determine whether the voltage difference enters the dynamic threshold range. The event monitoring module is used to monitor the crossing events of the voltage difference in multiple logical sub-intervals within the dynamic threshold range when the voltage difference enters the dynamic threshold range, and to accumulate the residence time in each logical sub-interval. The status assessment module is used to assess the grid connection permit status of the corresponding battery cluster based on the crossing event and the dwell time; The sequence generation module is used to generate a coordinated grid connection sequence when the grid connection permit status of multiple battery clusters reaches the preparatory conditions, based on the estimated impact of grid connection operation on the bus voltage and the voltage difference of other battery clusters. The operation execution module is used to perform grid connection operations on the corresponding battery clusters according to the coordinated grid connection sequence.
[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. By introducing dynamic threshold intervals and logical sub-regions within these intervals, the problem of command jitter in critical states under fixed thresholds is effectively overcome. Simple threshold comparisons are transformed into continuous monitoring and analysis of the dynamic behavior of voltage differences within a set interval. By tracking the crossing events and cumulative dwell time between boundary sub-intervals and stable sub-intervals, the true trend of voltage difference stabilization and random fluctuations caused by noise or disturbances can be accurately identified. This ensures that the assessment of grid connection permit status is based on a continuous and stable voltage behavior, avoiding frequent changes in control commands caused by small fluctuations in voltage values near a single threshold point, and significantly improving the stability and reliability of sequential grid connection control decisions.
[0016] 2. By generating a coordinated grid connection sequence, a system-level control improvement was achieved, moving from independent judgment of a single cluster to coordinated optimization of multiple clusters. After determining that multiple battery clusters meet the grid connection conditions, the impact of each cluster's grid connection operation on the DC bus voltage is estimated, and the optimal grid connection sequence is planned accordingly. Battery clusters that help improve or support the DC bus voltage are prioritized for connection, thereby actively maintaining system voltage stability during the cluster-by-cluster grid connection process and creating more favorable voltage conditions for subsequent clusters to be connected to the grid. This sequential operation based on global state prediction not only suppresses circulating current but also enhances the overall voltage stability and operational smoothness of the multi-cluster parallel system during the grid connection transition phase. Attached Figure Description
[0017] Figure 1 This is a flowchart of the sequential flexible grid connection method for ship high-voltage battery clusters based on voltage equalization according to the present invention; Figure 2This is a schematic diagram of the structure of the sequential flexible grid-connected system for high-voltage battery clusters on ships based on voltage equalization, according to the present invention. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0019] Example 1: Figure 1 The present invention provides a method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization, which includes the following steps: S1. Obtain the terminal voltage and DC bus voltage of each battery cluster to be connected to the grid.
[0020] S2. Calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and determine whether the voltage difference enters the dynamic threshold range.
[0021] S3. When the voltage difference enters the dynamic threshold range, monitor the crossing events of the voltage difference in multiple logic sub-intervals within the dynamic threshold range, and accumulate the residence time in each logic sub-interval.
[0022] S4. Assess the grid connection permit status of the corresponding battery cluster based on the crossing event and dwell time.
[0023] S5. When the grid connection permit status of multiple battery clusters reaches the preparatory conditions, a coordinated grid connection sequence is generated based on the estimated impact of grid connection operation on the bus voltage and the voltage difference of other battery clusters.
[0024] S6. Perform grid connection operation for the corresponding battery cluster according to the coordinated grid connection sequence.
[0025] S1. Obtain the terminal voltage and DC bus voltage of each battery cluster to be connected to the grid, implemented as follows: The acquisition of the terminal voltage and DC bus voltage of each battery cluster to be connected to the grid is achieved by configuring voltage sensors that are directly connected to the positive and negative output terminals of each battery cluster and the positive and negative terminals of the DC bus, or connected through a voltage divider circuit. Each voltage sensor is connected to an independent analog-to-digital converter (ADC) channel, which are integrated on one or more acquisition boards with synchronous triggering functionality. When a voltage acquisition operation is required, a central controller or dedicated timing circuit sends a global, edge-aligned sampling trigger pulse to all ADC channels participating in the sampling. The timing of this sampling trigger pulse is aligned with a stable high-frequency clock to ensure that all ADC channels simultaneously begin sampling and converting the analog signals output by their respective connected voltage sensors when the rising edge of the trigger pulse arrives. The sampling frequency is set according to the fastest possible rate of voltage change of the battery cluster. For example, considering the potential for sudden load increases or decreases during grid connection, the voltage change rate may be high, therefore the sampling frequency is set to no less than 1000 times per second. After completing a conversion, all analog-to-digital converter channels transmit the resulting raw digital code value via a parallel or high-speed serial bus.
[0026] After acquiring the raw digital code value representing the voltage value in each sampling channel, an immediate verification based on a preset range is performed on the raw digital code value. This preset range is an independently set effective voltage range for each sampling channel. For sampling channels connected to the terminal voltage of the battery cluster to be connected to the grid, the lower limit of the preset range is set to the lowest operating voltage value allowed by the battery cluster's technical specifications, and the upper limit is set to the highest operating voltage value allowed by the battery cluster's technical specifications. For example, for a battery cluster with a rated voltage of 824 volts DC, the lower limit of the preset range for its corresponding terminal voltage sampling channel can be set to 742 volts, and the upper limit can be set to 896 volts. For sampling channels connected to the DC bus voltage, the lower limit of the preset range is set to the lowest DC bus voltage value allowed for normal system operation, and the upper limit is set to the highest DC bus voltage value allowed for normal system operation. The immediate verification process involves multiplying the raw digital code value from the sampling channel by a preset scaling factor to restore it to the measured voltage value in volts. The preset proportional coefficient is calculated based on the sensor turns ratio and the resistance value of the voltage divider network. Then, the measured voltage value is compared with the lower limit and upper limit of the preset range set for that channel. The sampling verification is considered successful only if the measured voltage value is greater than or equal to the lower limit of the preset range set for that channel, and simultaneously less than or equal to the upper limit of the preset range set for that channel.
[0027] Only when a sampled value from a sampling channel passes the instantaneous verification based on a preset range will the restored measured voltage value be marked as valid data and output as a valid terminal voltage or valid DC bus voltage to subsequent calculation and judgment steps. The output valid data is accompanied by a timestamp synchronized with the global sampling trigger pulse. If a sampled value from a sampling channel fails the instantaneous verification, the sampled data will be discarded, and a hardware fault or signal anomaly warning flag may be triggered after multiple consecutive verification failures for that channel. This ensures that the voltage data input to subsequent control logic is valid data that has undergone a validity check. All valid terminal voltage and valid DC bus voltage data are stored in the memory area for use in the next step of calculating the voltage difference.
[0028] S2. Calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and determine whether the voltage difference enters the dynamic threshold range. This is implemented as follows: Based on the effective terminal voltage and the effective DC bus voltage, the voltage difference corresponding to each battery cluster is calculated. This calculation is performed by subtracting the stored effective terminal voltage value of a battery cluster from the effective DC bus voltage value at the same timestamp. Both the effective terminal voltage value and the effective DC bus voltage value are in volts, and the voltage difference obtained from the subtraction is also in volts. For each battery cluster to be connected to the grid in the system, this subtraction operation is performed independently and repeatedly, thereby generating a real-time updated voltage difference sequence for each battery cluster. The calculation process is executed at a fixed period, which is synchronized with or an integer multiple of the voltage sampling period to ensure that the effective terminal voltage and effective DC bus voltage used in each calculation are the latest sampled and verified data.
[0029] For each calculated voltage difference, it is determined whether it falls within the voltage range defined by the dynamic threshold interval. The voltage range defined by the dynamic threshold interval is a continuous range of voltage values, with its lower limit being the lower limit of the dynamic threshold interval and its upper limit being the upper limit. The specific values of the lower and upper limits of the dynamic threshold interval are not fixed but are dynamically calculated based on historical operating data. The determination process involves comparing the currently calculated voltage difference value with the values of the lower and upper limits of the dynamic threshold interval at the current moment. Only if the currently calculated voltage difference value is greater than or equal to the lower limit of the dynamic threshold interval at the current moment, and simultaneously less than or equal to the upper limit of the dynamic threshold interval at the current moment, can the voltage difference be determined to be within the voltage range defined by the dynamic threshold interval. Otherwise, the voltage difference is determined to be outside the voltage range defined by the dynamic threshold interval.
[0030] When the voltage difference of a battery cluster changes from being previously determined to be outside the voltage range defined by the dynamic threshold interval to being determined to be within the voltage range defined by the dynamic threshold interval, the voltage difference is considered to have entered the voltage range defined by the dynamic threshold interval for the first time. Once the voltage difference is detected to have entered the voltage range defined by the dynamic threshold interval for the first time, an independent time window is started for that battery cluster and timing begins. The length of the time window is a preset time parameter, for example, the length of the time window can be set to 500 milliseconds. Timing starts from zero and increments with the system clock until the length of the time window is reached.
[0031] Throughout the entire duration of the time window's initiation and timing, the calculated voltage difference of the battery cluster is continuously and periodically assessed to determine whether it remains within the voltage range defined by the dynamic threshold interval. This continuous assessment frequency is consistent with the voltage difference calculation frequency. Only when each periodic assessment throughout the entire time window period, from its initiation to its end, indicates that the voltage difference remains within the voltage range defined by the dynamic threshold interval, is the voltage difference ultimately determined to have entered the dynamic threshold interval. If, during any periodic assessment before the end of the time window, the voltage difference is found to be outside the voltage range defined by the dynamic threshold interval, the time window timing is immediately terminated, and the state is reset. This time, it is not considered to have entered the dynamic threshold interval. If the voltage difference subsequently enters the voltage range defined by the dynamic threshold interval again, a new time window is restarted and timing begins.
[0032] The dynamic threshold interval is dynamically adjusted based on historical statistical values of effective terminal voltage and effective DC bus voltage, ensuring that the voltage range defined by the dynamic threshold interval adapts to the long-term voltage variation trend of the battery cluster. The dynamic adjustment process is executed according to a predetermined period or trigger condition, such as every 24 hours or when the historical average value of the battery cluster's terminal voltage changes by more than 1%. Historical statistical values refer to all effective terminal voltage values and effective DC bus voltage values collected over a predetermined period. The arithmetic mean of all effective DC bus voltage values over the past period is calculated to obtain the historical average value of the DC bus voltage. For each battery cluster, the arithmetic mean of all effective terminal voltage values over the past period is calculated to obtain the historical average value of the terminal voltage for that battery cluster. For each battery cluster, the difference between its historical average terminal voltage and historical average DC bus voltage is calculated as the long-term average voltage difference for that battery cluster. Based on the long-term average voltage difference of the battery cluster, and superimposed with a fixed tolerance bandwidth, the lower and upper limits of the dynamic threshold interval corresponding to that battery cluster are calculated. The lower limit of the dynamic threshold interval is set to the long-term average voltage difference minus a fixed tolerance voltage value, such as 2 volts, and the upper limit is set to the long-term average voltage difference plus the same fixed tolerance voltage value, such as 2 volts. The fixed tolerance voltage value is selected based on the typical amplitude of the battery cluster's terminal voltage fluctuation around the long-term average value during stable operation. Through this mechanism, the center point of the voltage range defined by the dynamic threshold interval will slowly move as the relationship between the battery cluster and the DC bus changes, thereby always tracking the long-term drift of the battery cluster voltage and avoiding the failure of the fixed threshold interval due to long-term voltage deviation caused by battery aging or changes in ambient temperature. The new lower and upper limits of the dynamic threshold interval generated after each dynamic adjustment will be applied to all subsequent judgments on whether the voltage difference is within the voltage range defined by the dynamic threshold interval.
[0033] S3. When the voltage difference enters the dynamic threshold range, monitor the crossing events of the voltage difference across multiple logic sub-intervals within the dynamic threshold range, and accumulate the residence time in each logic sub-interval. This is implemented as follows: Once the voltage difference is determined to have entered the dynamic threshold range, monitoring of its dynamic behavior across multiple logical sub-intervals within this range begins. Based on the relative distance between the voltage difference and the lower and upper limits of the dynamic threshold range, the entire voltage range defined by the dynamic threshold range is divided into two or more continuous, non-overlapping voltage bands, called logical sub-intervals. Regions near the lower and upper limits of the dynamic threshold range are designated as boundary sub-intervals, while regions in the middle of the dynamic threshold range and far from these limits are designated as stable sub-intervals. The division is based on a predefined distance percentage parameter, which is between zero and fifty percent. For example, the distance percentage parameter could be set to 10%. The width of the entire dynamic threshold range is obtained by subtracting the lower limit from the upper limit. The range of the boundary sub-intervals is determined by multiplying the width of the entire dynamic threshold range by the distance percentage parameter to obtain a boundary width value. The lower boundary voltage value of the lower boundary sub-interval is equal to the lower limit of the dynamic threshold interval, and the upper boundary voltage value of the lower boundary sub-interval is equal to the lower limit of the dynamic threshold interval plus the boundary width. The lower boundary voltage value of the upper boundary sub-interval is equal to the upper limit of the dynamic threshold interval minus the boundary width, and the upper boundary voltage value of the upper boundary sub-interval is equal to the upper limit of the dynamic threshold interval. The lower boundary voltage value of the stable sub-interval is equal to the upper boundary voltage value of the lower boundary sub-interval, and the upper boundary voltage value of the stable sub-interval is equal to the lower boundary voltage value of the upper boundary sub-interval. These boundary voltage values of logical sub-intervals are recalculated and updated when the dynamic threshold interval is dynamically adjusted.
[0034] The system continuously monitors the instantaneous value of the voltage difference and determines its current logical sub-interval. The instantaneous voltage difference value refers to the latest value representing the current voltage difference of the battery cluster, obtained according to a fixed calculation cycle. The determination process involves comparing the instantaneous voltage difference value with the lower and upper boundary voltage values of each logical sub-interval. The instantaneous voltage difference value is sequentially compared to the lower boundary voltage value of each logical sub-interval for greater than or equal to the current value, and then compared to the upper boundary voltage value for less than or equal to the current value. When the instantaneous voltage difference value simultaneously satisfies the condition of being greater than or equal to the lower boundary voltage value and less than or equal to the upper boundary voltage value of a logical sub-interval, it is determined that the instantaneous voltage difference value is currently within that logical sub-interval. This determination operation is performed synchronously at the end of each voltage difference calculation cycle.
[0035] A crossing event is recorded when, within two consecutive judgment cycles, the instantaneous value of the voltage difference moves from the logical sub-interval of the previous judgment cycle to a different logical sub-interval in the current judgment cycle. The crossing event records the time of the crossing and the direction information from the previous logical sub-interval to the current logical sub-interval. Simultaneously, the recorded current logical sub-interval information is updated to reflect the latest position of the instantaneous voltage difference value. To detect crossings, the identifier of the instantaneous voltage difference value within the logical sub-interval at the end of the previous judgment cycle needs to be stored. After the current judgment cycle completes the judgment of a new logical sub-interval, the identifier of the logical sub-interval obtained in this judgment is compared with the stored identifier of the logical sub-interval from the previous cycle. If they are different, it indicates that a crossing has occurred from one logical sub-interval to another. Each crossing event is recorded in an event log associated with that battery cluster.
[0036] From the moment the instantaneous value of the voltage difference enters the current logical sub-interval, an independent timer dedicated to that logical sub-interval is started, continuously accumulating the residence time of the voltage difference within that sub-interval. Each logical sub-interval maintains an independent accumulated residence time variable. When the instantaneous value of the voltage difference enters a new logical sub-interval, it first checks whether the corresponding accumulated residence time variable is in an active accumulation state. If not, it is activated, and a value equal to the length of the time interval is added to the accumulated residence time variable at fixed time intervals. The fixed time interval is equal to the calculation cycle of the voltage difference. If the instantaneous value of the voltage difference remains within the same logical sub-interval, the accumulated residence time variable of that logical sub-interval will continue to accumulate. When the instantaneous value of the voltage difference crosses to another logical sub-interval, the accumulated residence time variable of the original logical sub-interval will pause accumulation and maintain its current accumulated value, while the newly entered logical sub-interval will activate its own accumulated residence time variable and begin accumulation. In this way, the system independently and continuously accumulates the total residence time for each battery cluster within each of its logical sub-intervals.
[0037] S4. Assess the grid connection permit status of the corresponding battery cluster based on the crossing event and dwell time, implemented as follows: Based on recorded cross-travel events and cumulative dwell time, the grid connection permit status of the corresponding battery cluster is evaluated. The recorded cross-travel events are analyzed by retrieving all cross-travel events recorded within the most recent period from the event log associated with that battery cluster. The time range length of all cross-travel events recorded within the most recent period is a configurable parameter; for example, the time range length can be set to the most recent 60 seconds. The directional information sequence contained in all cross-travel events recorded within the most recent period is examined to identify whether a specific cross-travel event sequence pattern exists. This specific cross-travel event sequence pattern is used to determine whether the voltage difference shows a trend of crossing from the boundary sub-interval to the stable sub-interval. The method for identifying a specific cross-travel event sequence pattern is to search in the directional information sequence for at least one cross-travel event with a direction from the boundary sub-interval to the stable sub-interval, and in the directional information sequence after this cross-travel event, up to the current analysis time, no cross-travel event with a direction from the stable sub-interval back to the boundary sub-interval appears. The timestamp of each cross-travel event recorded in the event log is used to verify that the occurrence order and time interval of the cross-travel events conform to the continuity of the dynamic process.
[0038] Check whether the current cumulative residence time of the voltage difference within the stable sub-interval has reached the predetermined duration. The predetermined duration represents the shortest time the voltage difference of the battery cluster needs to remain within the stable sub-interval. The predetermined duration is set based on the time required for the system to recover from a typical voltage disturbance and reach steady state; for example, the predetermined duration can be set to 2 seconds. The checking process involves reading the current value of the cumulative residence time variable maintained for the stable sub-interval of this battery cluster. The current value of the cumulative residence time variable is compared with the predetermined duration. If the current value of the cumulative residence time variable is greater than or equal to the predetermined duration, it is determined that the current cumulative residence time of the voltage difference within the stable sub-interval has reached the predetermined duration.
[0039] If the voltage difference shows a trend of crossing from the boundary sub-interval to the stable sub-interval, and the current cumulative residence time in the stable sub-interval reaches the predetermined duration, then the grid connection permission status of the corresponding battery cluster is assessed as "grid connection permitted." The "grid connection permitted" status indicates that the battery cluster has the voltage conditions for safe connection to the DC bus. If the voltage difference shows a trend of crossing from the boundary sub-interval to the stable sub-interval, but the current cumulative residence time of the voltage difference in the stable sub-interval has not yet reached the predetermined duration, then the grid connection permission status of the corresponding battery cluster is assessed as "prepared for grid connection." The "prepared for grid connection" status indicates that the voltage of the battery cluster is stabilizing, but the stabilization duration is insufficient. If the voltage difference does not show a trend of crossing from the boundary sub-interval to the stable sub-interval, then the grid connection permission status of the corresponding battery cluster is assessed as "transfer prohibited." Situations where no trend of crossing from the boundary sub-interval to the stable sub-interval is observed include: in all crossing events recorded in the recent period, no crossing event from the boundary sub-interval to the stable sub-interval occurred, or after a crossing event from the boundary sub-interval to the stable sub-interval occurred, a crossing event from the stable sub-interval back to the boundary sub-interval occurred. A "Switching Prohibited" state indicates that the current voltage dynamics of the battery cluster do not meet safe grid connection conditions. The entire evaluation process is executed periodically or triggered upon detecting a new cross-pass event or an update to the cumulative dwell time variable. The evaluation result—whether the grid connection is permitted, ready for grid connection, or switching is prohibited—is stored and associated with a unique identifier for the battery cluster.
[0040] S5. When the grid connection permit status of multiple battery clusters meets the preparatory conditions, a coordinated grid connection sequence is generated based on the estimated impact of the grid connection operation on the bus voltage and the voltage difference of other battery clusters, and implemented as follows: When multiple battery clusters meet the preparatory conditions for grid connection permission (i.e., the battery clusters are in a permitted grid connection state or a preparatory grid connection state), a coordinated grid connection sequence is generated based on the estimated impact of grid connection operation on the DC bus voltage and the voltage difference of other battery clusters. All battery clusters in the permitted or preparatory grid connection state are identified as candidate clusters. The identification process involves traversing all battery clusters to be connected to the grid in the system and reading the latest evaluated grid connection permission state associated with the unique identifier of each battery cluster. If a battery cluster is in the permitted or preparatory grid connection state, it is added to a temporary list called the candidate cluster set. The candidate cluster set contains all battery clusters currently eligible for consideration in grid connection sequencing.
[0041] For each candidate cluster in the candidate cluster set, based on the current voltage difference between the candidate cluster's terminal voltage and the DC bus voltage, and the DC bus voltage itself, the simulation simulates the possible direction of change in the DC bus voltage after grid connection. The required input parameters include the latest valid terminal voltage value of the candidate cluster, the latest valid DC bus voltage value, and the current voltage difference value of the candidate cluster. The simulation is based on a simplified electrical system model that treats the DC bus as a node and the candidate cluster as an equivalent voltage source with a specific electromotive force and internal resistance. The core of the simulation is to determine the relative values of the candidate cluster's terminal voltage and the current DC bus voltage. The candidate cluster's terminal voltage value is calculated by adding the current voltage difference value to the current DC bus voltage value. If the candidate cluster's terminal voltage value is higher than the current DC bus voltage value, the simulation determines that the possible direction of change in the DC bus voltage after grid connection is to increase the DC bus voltage. If the terminal voltage of a candidate cluster is lower than the current DC bus voltage, the simulation determines that the DC bus voltage will likely decrease after the grid connection operation. If the terminal voltage of a candidate cluster is equal to the current DC bus voltage, the simulation determines that the DC bus voltage will remain essentially unchanged after the grid connection operation. This simulation provides a descriptive result for each candidate cluster in the set, indicating the possible direction of change in the DC bus voltage.
[0042] Based on the possible directions of change of the simulated DC bus voltage, all candidate clusters are classified and ranked to generate a coordinated grid-connected sequence that stabilizes the system. Classification involves dividing the candidate clusters into different groups according to the possible directions of change of their DC bus voltage. For example, all candidate clusters whose possible direction of change is increasing the DC bus voltage are assigned to the first priority group, all candidate clusters whose possible direction of change is basically unchanged are assigned to the second priority group, and all candidate clusters whose possible direction of change is decreasing the DC bus voltage are assigned to the third priority group. Ranking involves arranging the candidate clusters within each group according to specific rules. When generating the coordinated grid-connected sequence, the classification and ranking rules prioritize candidate clusters whose possible direction of change of the simulated DC bus voltage is increasing the DC bus voltage, and under the same conditions, prioritize candidate clusters with smaller current voltage differences. "Same conditions" means that the possible directions of change of the DC bus voltage of the candidate clusters are the same. The specific process for generating the coordinated grid connection sequence is as follows: First, select all candidate clusters whose DC bus voltage change direction is increasing. Then, sort these candidate clusters in ascending order of their current voltage difference. Next, select all candidate clusters whose DC bus voltage change direction is essentially unchanged. Again, sort these candidate clusters in ascending order of their current voltage difference. Finally, select all candidate clusters whose DC bus voltage change direction is decreasing. Again, sort these candidate clusters in ascending order of their current voltage difference. These three sorted lists are then concatenated according to their priority groups: first priority group, second priority group, and third priority group, forming a complete and ordered list of battery cluster identifiers, i.e., the coordinated grid connection sequence. The coordinated grid connection sequence records the unique identifier of each battery cluster and its order. The generated coordinated grid connection sequence is stored for use in subsequent grid connection operations.
[0043] S6. Perform grid connection operation for the corresponding battery cluster according to the coordinated grid connection sequence, as follows: The grid connection operation of the corresponding battery cluster is performed according to the coordinated grid connection sequence. The unique identifier and its order of the battery clusters are read from the stored coordinated grid connection sequence; according to the order indicated by the coordinated grid connection sequence, starting from the first battery cluster in the sequence, one battery cluster is selected as the current battery cluster to be operated; the selection operation refers to loading the unique identifier of the battery cluster to be operated into a current operation register; after each battery cluster is selected, it will undergo a subsequent check process.
[0044] Before issuing a closing command to the grid-connected switch of the currently selected battery cluster, the current voltage difference between the terminal voltage and the DC bus voltage of the battery cluster is acquired again. This acquisition is a dedicated, real-time voltage acquisition and calculation operation. This triggers a real-time parallel synchronous sampling of the terminal voltage and DC bus voltage of the currently selected battery cluster. The triggering method for real-time sampling is the same as for periodic sampling, with a central controller or a dedicated timing circuit sending a global sampling trigger pulse to the relevant analog-to-digital converter channel. After sampling, the original digital code value acquired by the sampling channel is subjected to real-time verification based on a preset range. Only when the verification passes is the restored measured voltage value used as the real-time valid terminal voltage or the real-time valid DC bus voltage. Then, based on the real-time valid terminal voltage and the real-time valid DC bus voltage, the current voltage difference of the battery cluster is calculated. The calculation method is to subtract the real-time valid DC bus voltage from the real-time valid terminal voltage value to obtain the current voltage difference value in volts.
[0045] The closing command is issued only after confirming that the current voltage difference is still within the dynamic threshold range and that the grid connection permit status of the corresponding battery cluster has not been updated to prohibit switching. The process of confirming that the current voltage difference is still within the dynamic threshold range involves comparing the recalculated current voltage difference value with the current lower limit and upper limit of the dynamic threshold range. Only if the current voltage difference is greater than or equal to the current lower limit and simultaneously less than or equal to the current upper limit is the current voltage difference considered to be within the dynamic threshold range. The process of confirming that the grid connection permit status of the corresponding battery cluster has not been updated to prohibit switching involves reading the latest evaluated grid connection permit status associated with the unique identifier of the battery cluster. If the read grid connection permit status is prohibit switching, it indicates that the grid connection permit status of the battery cluster has been updated to prohibit switching; if the read grid connection permit status is allowed grid connection or ready for grid connection, it indicates that the grid connection permit status of the battery cluster has not been updated to prohibit switching. The operation of issuing a closing command will only be executed when both of the above confirmation conditions are met simultaneously: that is, the current voltage difference is still within the dynamic threshold range and the grid connection permit status of the corresponding battery cluster has not been updated to prohibit switching.
[0046] The operation of issuing a closing command involves generating an electrical signal conforming to the grid-connected switch drive logic through a digital output channel. This signal is transmitted to the control coil of the grid-connected switch corresponding to the currently selected battery cluster. Upon receiving the closing command, the grid-connected switch performs a closing action. If any condition is not met during the confirmation process, the operation of issuing the closing command is not executed, and a grid-connection failure event is recorded. According to a preset strategy, the current grid-connection attempt for this battery cluster can be abandoned, and the next battery cluster in the coordinated grid-connection sequence can be selected to perform the same process. After successfully executing the operation of issuing the closing command, the system waits for a preset switch action stabilization time, such as 100 milliseconds, before it can begin processing the next battery cluster in the coordinated grid-connection sequence.
[0047] The method provided in this embodiment fully considers the special application requirements of high reliability and high safety of large-capacity energy storage systems on ships in its control strategy and step design. It is especially suitable for the frequent and flexible grid-connected and off-grid operation scenarios of multiple high-voltage battery packs in ship power systems under different operating conditions. Through the above-mentioned refined voltage behavior monitoring and coordinated sequence control, it can effectively adapt to the operating characteristics of ship power grid loads that are variable and complex, and significantly improve the management intelligence level of ship integrated power systems while ensuring system safety.
[0048] Example 2: Figure 2 A schematic diagram of the sequential flexible grid connection system for ship high-voltage battery clusters based on voltage equalization according to the present invention is provided. The sequential flexible grid connection system for ship high-voltage battery clusters based on voltage equalization includes the following modules: The voltage acquisition module is used to acquire the terminal voltage of each battery cluster to be connected to the grid and the DC bus voltage; The difference judgment module is used to calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and to determine whether the voltage difference enters the dynamic threshold range. The event monitoring module is used to monitor the crossing events of the voltage difference in multiple logical sub-intervals within the dynamic threshold range when the voltage difference enters the dynamic threshold range, and to accumulate the residence time in each logical sub-interval. The status assessment module is used to assess the grid connection permit status of the corresponding battery cluster based on the crossing event and the dwell time; The sequence generation module is used to generate a coordinated grid connection sequence when the grid connection permit status of multiple battery clusters reaches the preparatory conditions, based on the estimated impact of grid connection operation on the bus voltage and the voltage difference of other battery clusters. The operation execution module is used to perform grid connection operations on the corresponding battery clusters according to the coordinated grid connection sequence.
[0049] All calculations involved in the embodiments are dimensionless numerical calculations, and the preset parameters and thresholds in the calculations are set by those skilled in the art according to the actual situation.
[0050] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.
[0051] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.
[0052] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.
[0053] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.
[0054] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
[0055] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for sequential flexible grid connection of shipboard high-voltage battery clusters based on voltage equalization, characterized in that, Includes the following steps: S1. Obtain the terminal voltage and DC bus voltage of each battery cluster to be connected to the grid; S2. Calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and determine whether the voltage difference enters the dynamic threshold range. S3. When the voltage difference enters the dynamic threshold range, monitor the crossing events of the voltage difference in multiple logic sub-intervals within the dynamic threshold range, and accumulate the residence time in each logic sub-interval. S4. Assess the grid connection permit status of the corresponding battery cluster based on the crossing event and dwell time; S5. When the grid connection permit status of multiple battery clusters reaches the preparatory conditions, a coordinated grid connection sequence is generated based on the estimated impact of grid connection operation on the bus voltage and the voltage difference of other battery clusters. S6. Perform grid connection operation for the corresponding battery cluster according to the coordinated grid connection sequence.
2. The method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization according to claim 1, characterized in that, Obtain the terminal voltage and DC bus voltage of each battery cluster to be connected to the grid, including: The terminal voltage and DC bus voltage of each battery cluster to be connected to the grid are sampled in parallel and synchronously. During the sampling process, the voltage value acquired by each sampling channel is subjected to real-time verification based on a preset range; The voltage value obtained from the sampling channel will only be output as a valid terminal voltage or DC bus voltage if the verification passes.
3. The method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization according to claim 1, characterized in that, Calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and determine whether the voltage difference enters the dynamic threshold range, including: Based on the effective terminal voltage and the effective DC bus voltage, the voltage difference corresponding to each battery cluster is calculated. For each voltage difference, determine whether it falls within the voltage range defined by the dynamic threshold interval; When the voltage difference first enters the voltage range, the time window is activated and timing begins. Only when the voltage difference remains within the voltage range within the time window will the voltage difference be ultimately determined to have entered the dynamic threshold range.
4. The sequential flexible grid connection method for ship high-voltage battery clusters based on voltage equalization according to claim 3, characterized in that, The dynamic threshold range is dynamically adjusted based on historical statistical values of the effective terminal voltage and the effective DC bus voltage, so that the voltage range can adapt to the long-term voltage change trend of the battery cluster.
5. The method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization according to claim 1, characterized in that, When the voltage difference enters the dynamic threshold range, the system monitors the crossing events of the voltage difference across multiple logic sub-intervals within the dynamic threshold range and accumulates the residence time in each logic sub-interval, including: Based on the distance from the boundary of the dynamic threshold interval, the dynamic threshold interval is divided into boundary sub-intervals and stable sub-intervals; Continuously monitor the instantaneous value of the voltage difference and determine its current logical sub-interval; When the instantaneous value of the voltage difference moves from one logical sub-interval to another, a crossing event is recorded, and the current logical sub-interval is updated. From the moment the instantaneous value of the voltage difference enters the current logic sub-interval, an independent timer for the logic sub-interval is started to continuously accumulate the residence time of the voltage difference in the logic sub-interval.
6. The method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization according to claim 1, characterized in that, The grid connection permit status of the corresponding battery cluster is assessed based on the crossing event and dwell time, including: Analyze the recorded crossing events to determine whether the voltage difference shows a trend of crossing from the boundary sub-interval to the stable sub-interval; Check whether the current cumulative dwell time of the voltage difference within the stable sub-interval has reached the predetermined duration; If the voltage difference shows a trend of crossing from the boundary sub-interval to the stable sub-interval, and the current cumulative residence time in the stable sub-interval reaches the predetermined duration, then the grid connection permit status of the corresponding battery cluster is assessed as allowing grid connection.
7. The method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization according to claim 1, characterized in that, When the grid connection permit status of multiple battery clusters meets the preparatory conditions, a coordinated grid connection sequence is generated based on the estimated impact of the grid connection operation on the bus voltage and the voltage difference of other battery clusters, including: Identify all battery clusters with grid connection permit status of allowed grid connection or ready for grid connection as candidate clusters; For each candidate cluster, based on the current voltage difference between the candidate cluster's terminal voltage and the DC bus voltage, as well as the DC bus voltage itself, the possible direction of change of the DC bus voltage after the grid connection operation is executed is simulated. Based on the possible changes in the DC bus voltage obtained from the simulation, all candidate clusters are classified and sorted to generate a coordinated grid connection sequence that makes the system tend to be stable.
8. The method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization according to claim 7, characterized in that, When generating a coordinated grid connection sequence, the classification and sorting rules are as follows: priority is given to candidate clusters whose possible change direction of the simulated DC bus voltage is to increase the DC bus voltage, and under the same conditions, priority is given to candidate clusters with smaller current voltage differences.
9. The method for sequential flexible grid connection of ship high-voltage battery clusters based on voltage equalization according to claim 1, characterized in that, Execute grid connection operations for the corresponding battery clusters according to the coordinated grid connection sequence, including: Select the battery clusters to be operated in sequence according to the order indicated by the coordinated grid connection sequence; Before issuing a closing command to the grid-connected switch of the currently selected battery cluster, the current voltage difference between the terminal voltage of the battery cluster and the DC bus voltage is obtained again. Only after confirming that the current voltage difference is still within the dynamic threshold range and that the grid connection permit status of the corresponding battery cluster has not been updated to prohibit switching, will the operation of issuing a closing command be executed.
10. A sequential flexible grid connection system for ship high-voltage battery clusters based on voltage equalization, used to implement the sequential flexible grid connection method for ship high-voltage battery clusters based on voltage equalization as described in any one of claims 1-9, characterized in that, Includes the following modules: The voltage acquisition module is used to acquire the terminal voltage of each battery cluster to be connected to the grid and the DC bus voltage; The difference judgment module is used to calculate the voltage difference between the terminal voltage of each battery cluster and the DC bus voltage, and to determine whether the voltage difference enters the dynamic threshold range. The event monitoring module is used to monitor the crossing events of the voltage difference in multiple logical sub-intervals within the dynamic threshold range when the voltage difference enters the dynamic threshold range, and to accumulate the residence time in each logical sub-interval. The status assessment module is used to assess the grid connection permit status of the corresponding battery cluster based on the crossing event and the dwell time; The sequence generation module is used to generate a coordinated grid connection sequence when the grid connection permit status of multiple battery clusters reaches the preparatory conditions, based on the estimated impact of grid connection operation on the bus voltage and the voltage difference of other battery clusters. The operation execution module is used to perform grid connection operations on the corresponding battery clusters according to the coordinated grid connection sequence.