Stacked energy storage battery pack equalization control method and system

Abstract

The invention discloses a stack type energy storage battery pack balance control method and system, and belongs to the technical field of energy storage. For a single-cluster energy storage battery, the BMS detects the average voltage of six battery packs in real time and ranks the average voltage from large to small as V1-V6, and a target threshold value is set as a voltage imbalance threshold value; charging is started after an active equalization instruction is received, if V1-Vn is smaller than a target threshold value and V1-Vn + 1 is larger than the target threshold value, battery packs corresponding to Vn + 1-V6 need to be independently charged and equalized, and at the moment, relays corresponding to V1-Vn are closed, and batteries are connected with an inverter for calibration charging; in the later period of charging, the BMS bypasses the fully-charged battery packs, only the remaining battery packs which are not fully charged continue to be charged, and the operation is repeatedly executed till all the battery packs in the single cluster are fully charged. And voltage balance control of the battery pack in a single-cluster and multi-cluster parallel scene is realized.

Description

Technical Field

[0001] This application belongs to the field of energy storage technology and discloses a method and system for equalization control of stacked energy storage battery packs. Background Technology

[0002] Stacked battery storage systems are widely used in new energy power generation and grid energy storage due to their high energy density and long cycle life. These systems typically consist of multiple clusters of batteries connected in parallel. Each cluster contains multiple battery packs and a corresponding battery management system (BMS) for controlling the charging and discharging of the battery packs and monitoring their status.

[0003] Traditional stacked battery storage systems are prone to voltage imbalances during long-term use due to differences in manufacturing processes and charge-discharge cycle counts among the individual battery packs. In single-cluster operation, this imbalance causes some packs to charge prematurely while others remain sluggish, impacting the overall energy storage capacity and efficiency of the cluster. In multi-cluster parallel systems, the imbalance further exacerbates system performance degradation, shortens the overall battery pack lifespan, and increases maintenance costs. Current solutions to this voltage imbalance problem still require improvement in balancing accuracy and efficiency, and cannot adequately meet the requirements for long-term stable operation of stacked battery storage systems. Summary of the Invention

[0004] This application provides a method and system for equalization control of stacked energy storage battery packs, which solves the problem of voltage imbalance that occurs after long-term use of stacked energy storage battery systems. The details are as follows.

[0005] On one hand, a method for equalization control of stacked energy storage battery packs is provided, applied to a system containing a cluster of energy storage batteries, the cluster of energy storage batteries including 6 battery packs and a BMS, the method comprising: The average voltage of the six battery packs is monitored in real time. Upon receiving the active balancing command, the six battery packs are charged. In the later stages of charging, the fully charged battery packs are bypassed, and the remaining partially charged battery packs continue to be charged. Repeatedly perform the operation of bypassing the fully charged battery pack and charging the remaining battery pack until all battery packs in the cluster of energy storage batteries are fully charged.

[0006] Optionally, after real-time detection of the average voltage of the six battery packs, the method further includes: The average voltages of the six battery packs are arranged in descending order as V1, V2, V3, V4, V5, and V6, and the threshold for voltage imbalance between the packs is defined as the target threshold.

[0007] Optionally, the method for determining whether the battery pack needs separate charging equalization is: When V1-Vn < the target threshold and V1-Vn+1 > the target threshold, the battery packs corresponding to voltages Vn+1 to V6 are determined to require separate charging and equalization.

[0008] Optionally, the method for charging battery packs that require individual charging equalization is as follows: Close the relays corresponding to V1 to Vn to connect the battery to the inverter and perform calibration charging on the battery packs corresponding to Vn+1 to V6.

[0009] Optionally, in the later stage of charging, the fully charged battery pack is bypassed, and the remaining partially charged battery pack continues to be charged, including: When a battery pack is detected to be fully charged, the corresponding relay is closed to disconnect the battery pack from the charging circuit.

[0010] Optionally, the stacked energy storage battery pack equalization control method described above includes at least one cluster of energy storage batteries, each cluster of energy storage batteries includes 6 battery packs and a BMS, the BMS is used to detect the average voltage of the 6 battery packs in the corresponding cluster in real time, receive active equalization commands, and control the charging and bypass operation of the battery packs.

[0011] Optionally, the system includes multiple clusters of energy storage batteries connected in parallel. The BMS is also used to receive instructions to control one cluster of energy storage batteries to operate normally while the other clusters are in standby mode, and to perform equalization control on the normally operating cluster of energy storage batteries.

[0012] Optionally, the BMS is also used to set a threshold for voltage imbalance between packs as a target threshold, and to determine whether the battery pack needs to be individually charged and balanced based on the threshold.

[0013] Optionally, when the BMS determines that the battery packs corresponding to Vn+1 to V6 need to be charged and balanced individually, it controls the closing of the relays corresponding to V1 to Vn and controls the connection between the battery and the inverter to perform calibration charging on the battery packs corresponding to Vn+1 to V6.

[0014] The BMS is also used to detect the charging status of the battery pack during the charging process. When the battery pack is detected to be fully charged, it controls the corresponding relay of the battery pack to close and bypass it.

[0015] This invention uses a BMS to monitor the average voltage of the six battery packs within a single cluster in real time. Combined with an imbalance threshold based on a target threshold, it accurately identifies the battery packs requiring balancing. Then, through relay control, inverter connection for calibration charging, and a bypass charging process to fully charge the battery packs in the later stages of charging, all battery packs within a single cluster can be fully charged, resolving the voltage imbalance problem within a single cluster. For multi-cluster parallel systems, the invention further addresses inter-cluster imbalance by controlling the operation of a single cluster while the remaining clusters are in standby mode, and balancing the operating cluster. This ensures the energy storage capacity of the stacked energy storage battery system, improves efficiency, extends the overall lifespan of the battery packs, and reduces maintenance costs. Attached Figure Description

[0016] Figure 1 This is a flowchart of the relay power-on self-test process for the stacked energy storage battery pack equalization control method of the present invention. Figure 2 This is a schematic diagram of the bypass function of the stacked energy storage battery pack equalization control method of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0018] In this article, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0019] The stacked energy storage battery pack equalization control method and system described in this application solves the voltage imbalance problem of battery packs in single-cluster and multi-cluster parallel systems by using a BMS for real-time detection, equalization judgment, and charge / discharge control of the battery pack voltage. The implementation process of the technical solution is described in detail below through specific embodiments.

[0020] Example 1 Figure 1 This is a flowchart illustrating the relay power-on self-test process for the equalization control method of stacked energy storage battery packs. Before the equalization control is initiated, it verifies whether the bypass relays corresponding to each battery pack are functioning correctly. The process logic is as follows.

[0021] After the BMS is powered on, it first acquires the total system voltage and the number of battery packs, then initiates a relay self-test. It then sequentially closes the bypass relays of each battery pack to determine if the total voltage decreases by approximately the voltage of a single battery pack (verifying the effectiveness of the relay closure). If the expected decrease is not achieved, it proceeds to anomaly troubleshooting. After disconnecting the relays, it further checks if the total voltage recovers and confirms that it is the last battery pack. If an anomaly is detected, the fault is recorded. The self-test ends after all tests are completed. This process allows for early detection of relay faults, providing hardware reliability assurance for the accurate execution of subsequent equalization control.

[0022] Figure 2 This is a flowchart illustrating the bypass function of the equalization control method for stacked energy storage battery packs, showing the bypass operation and multi-scenario adaptation logic in the equalization control. The flowchart logic is as follows.

[0023] After activating the bypass function, the system first checks for bypass relay malfunctions. If the system contains multiple battery pack clusters, it switches sequentially according to the principle of "one cluster working normally while the others are in standby mode." The system then performs charging calibration and equalization on the battery pack of the currently working cluster, monitoring the battery status in real time (SOC > 99%, cell voltage > 3.4V, or current < 0.2A). Simultaneously, it sorts the cell voltages, calculates the average voltage, and determines whether it is necessary to bypass the fully charged battery packs corresponding to V1~Vn. This process is repeated until the last battery pack cluster is equalized. This workflow achieves precise bypass and equalization charging in single / multi-cluster scenarios, effectively solving the problem of battery pack voltage imbalance.

[0024] Furthermore, the equalization control steps in this embodiment are as follows.

[0025] Voltage detection and sorting: After the BMS starts, it collects the voltage of each of battery packs 1 to 6 in real time and calculates the average voltage of each battery pack (if a battery pack consists of multiple cells, the average voltage is the arithmetic mean of the voltages of all cells in the battery pack). After the collection is completed, the BMS arranges the average voltages of the 6 battery packs in descending order, resulting in V1, V2, V3, V4, V5, and V6 (for example, after the collection, the calculated average voltages of battery pack 1 are 3.45V, battery pack 2 is 3.445V, battery pack 3 is 3.43V, battery pack 4 is 3.42V, battery pack 5 is 3.40V, and battery pack 6 is 3.39V, then V1=3.45V, V2=3.445V, V3=3.43V, V4=3.42V, V5=3.40V, and V6=3.39V).

[0026] Upon receiving the balancing command and initiating charging, the BMS controls the inverter to enter the working state after receiving the active balancing command sent from the outside, and starts the charging process for battery packs 1 to 6. At this time, all battery packs are connected to the charging circuit through the corresponding relays.

[0027] In the equalization demand judgment, the BMS calculates and judges the average voltage after sorting according to the preset target threshold voltage imbalance threshold, and calculates the difference between V1 and Vn (n is an integer from 1 to 5). When "V1-Vn<target threshold" and "V1-Vn+1>target threshold" are satisfied, it is determined that the battery packs corresponding to Vn+1 to V6 need to be charged and balanced separately.

[0028] In one example, taking a target threshold of 10mV as an example (of course, it can also be a certain range, which is not limited), and combined with the voltage data of this embodiment, V1-V2=3.45V-3.445V=0.005V<10mV, V1-V3=3.45V-3.43V=0.02V>10mV, so n=2, Vn+1~V6 correspond to V3~V6, that is, battery pack 3~battery pack 6 need to be charged and balanced separately.

[0029] For individual calibration charging, the BMS controls the closing of the relays corresponding to V1~Vn (i.e., relay 1 and relay 2) to keep the battery packs (battery pack 1 and battery pack 2) corresponding to V1~Vn connected. At the same time, it controls the inverter to establish a connection with the battery packs (battery pack 3~battery pack 6) corresponding to Vn+1~V6 and performs calibration charging on battery packs 3~6.

[0030] During the later stages of charging, bypassing and repeated equalization are performed. After entering the later stages of charging, the BMS monitors the charging status of each battery pack in real time (judged by whether the voltage reaches the full charge threshold, which is set according to the battery pack specifications). When it is detected that battery pack 1 and battery pack 2 have reached the full charge state, the BMS controls the closing of relays 1 and 2, causing battery pack 1 and battery pack 2 to disconnect from the charging circuit (i.e. bypass), while only battery packs 3 to 6 continue to charge.

[0031] Continue testing. When battery pack 3 reaches full charge, the BMS controls the closing of relay 3 to bypass battery pack 3, while keeping battery packs 4 through 6 charging.

[0032] Repeat the above operation until battery pack 6 is detected to be fully charged. At this time, all battery packs in a single cluster are fully charged, and the BMS controls the inverter to stop working, thus ending this single-cluster equalization control.

[0033] Example 2 This embodiment is for a "two-cluster parallel energy storage battery system". The hardware of the system includes two independent single-cluster energy storage batteries (denoted as cluster 1 and cluster 2, the composition of each cluster is the same as in embodiment 1, i.e., cluster 1 includes battery packs 11-16 and BMS1, and cluster 2 includes battery packs 21-26 and BMS2), a system master control module (used to send cluster working / standby commands), and all clusters are connected to the same load or power grid in parallel.

[0034] The specific steps of the equalization control in this embodiment are as follows.

[0035] Cluster operation status control: The system master control module sends instructions to BMS1 and BMS2, specifying that cluster 1 enters normal operation status (connected to load / power grid) and cluster 2 enters standby status (disconnected from load / power grid, enters standby strategy, such as the strategy provided in this application, which is to disconnect the main contactor, stop all operations under the premise of ensuring safety, and only retain the communication function to receive control instructions).

[0036] In the equalization control of cluster 1, BMS1 performs equalization control according to the steps of embodiment 1, and detects the average voltage of battery packs 11 to 16 in real time, and sorts them from largest to smallest to obtain V11, V12, V13, V14, V15, and V16; after receiving the active equalization command, it starts charging, and determines which battery packs need to be equalized individually according to the target threshold (for example, taking the target threshold as 10mV as an example, V11-V13=0.008V<10mV, V11-V14=0.012V>10mV, then n=3, and battery packs 14 to 16 need to be equalized individually).

[0037] Close relays 11-13 to connect the inverter and calibrate and charge battery packs 14-16.

[0038] During the later stages of charging, the fully charged battery pack is gradually bypassed until all battery packs in cluster 1 are fully charged, at which point BMS1 controls cluster 1 to resume normal operation.

[0039] In the equalization control of cluster 2, after the equalization of cluster 1 is completed, the system master control module sends instructions to BMS1 and BMS2 to switch cluster 2 into normal working state and cluster 1 into standby state; BMS2 performs equalization control on cluster 2 according to the steps of embodiment 1 until all battery packs in cluster 2 are fully charged.

[0040] Multi-cluster cyclic balancing: If the system contains more clusters (such as 3 or 4 clusters), the system master control module switches sequentially according to the principle of "one cluster working and the rest in standby". The BMS of each cluster performs balancing control according to the steps of Example 1 until the battery packs in all clusters are fully charged, and this multi-cluster balancing control ends.

[0041] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for balancing control of stacked energy storage battery packs, characterized in that, The method, applied to a system comprising a cluster of energy storage batteries, said cluster including six battery packs and a BMS, includes: The average voltage of the six battery packs is monitored in real time. Upon receiving the active balancing command, the six battery packs are charged. In the later stages of charging, the fully charged battery packs are bypassed, and the remaining partially charged battery packs continue to be charged. Repeatedly perform the operation of bypassing the fully charged battery pack and charging the remaining battery pack until all battery packs in the cluster of energy storage batteries are fully charged.

2. The method for equalization control of stacked energy storage battery packs according to claim 1, characterized in that, After real-time detection of the average voltage of the six battery packs, the method further includes: The average voltages of the six battery packs are arranged in descending order as V1, V2, V3, V4, V5, and V6, and the threshold for voltage imbalance between the packs is defined as the target threshold.

3. The method for equalization control of stacked energy storage battery packs according to claim 2, characterized in that, The method for determining whether the battery pack needs separate charging equalization is as follows: When V1-Vn < the target threshold and V1-Vn+1 > the target threshold, the battery packs corresponding to voltages Vn+1 to V6 are determined to require separate charging and equalization.

4. The method for equalization control of stacked energy storage battery packs according to claim 3, characterized in that, The method for charging battery packs that require individual charging equalization is as follows: Close the relays corresponding to V1 to Vn to connect the battery to the inverter and perform calibration charging on the battery packs corresponding to Vn+1 to V6.

5. The method for equalization control of stacked energy storage battery packs according to claim 1, characterized in that, In the later stage of charging, the fully charged battery packs are bypassed, and the remaining partially charged battery packs continue to be charged, including: When a battery pack is detected to be fully charged, the corresponding relay is closed to disconnect the battery pack from the charging circuit.

6. A stacked energy storage battery pack equalization control system, characterized in that, The stacked energy storage battery pack equalization control method according to any one of claims 1 to 5 above, the system includes at least one cluster of energy storage batteries, each cluster of energy storage batteries includes 6 battery packs and a BMS, the BMS is used to detect the average voltage of the 6 battery packs in the corresponding cluster in real time, receive active equalization commands, and control the charging and bypass operation of the battery packs.

7. The stacked energy storage battery pack equalization control system according to claim 6, characterized in that, The system includes multiple clusters of energy storage batteries connected in parallel. The BMS is also used to receive instructions to control one cluster of energy storage batteries to work normally while the other clusters are in standby mode, and to perform equalization control on the cluster of energy storage batteries that are working normally.

8. The stacked energy storage battery pack equalization control system according to claim 6, characterized in that, The BMS is also used to set the threshold for voltage imbalance between packs as the target threshold, and to determine whether the battery pack needs to be individually charged and balanced based on the threshold.

9. The stacked energy storage battery pack equalization control system according to claim 8, characterized in that, When the BMS determines that the battery packs corresponding to Vn+1 to V6 need to be charged and balanced individually, it controls the closing of the relays corresponding to V1 to Vn and controls the connection between the battery and the inverter to perform calibration charging on the battery packs corresponding to Vn+1 to V6. The stacked energy storage battery pack equalization control system according to claim 6 is characterized in that, The BMS is also used to detect the charging status of the battery pack during the charging process. When the battery pack is detected to be fully charged, it controls the corresponding relay of the battery pack to close and bypass it.

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