Parallel circulating current detection and current sharing strategy of lithium battery system

Abstract

The invention discloses a parallel circulating current detection and current sharing strategy of a lithium battery system, which solves the circulating current problem without adding hardware modules, and comprises a lithium battery system, an inverter and a cloud server, the strategy comprises the following steps of: suddenly adding 1c current for 10s to a lithium battery pack when the lithium battery pack is off line to obtain direct-current internal resistance pre-stored in a battery management module; the lithium battery pack updates the maximum allowable charging current to be applied, the total current applied to the inverter by the host, and the current sum of all the battery packs; if a mismatching problem is detected, the host uploads the zone bit where the circulation occurs to the inverter, and the inverter forwards the zone bit to the cloud server; the cloud server marks the corresponding request and enables the inverter to suddenly add # imgabs0 # secondary current to the lithium battery system, and the cloud server calculates the real internal resistance of each lithium battery pack according to the voltage change condition of the lithium battery pack; the cloud server issues the calculated real internal resistance to each battery management module, and updates the pre-stored DC internal resistance; and the cloud server reversely deduces a current actually matched adjustable parameter a according to the SOH and the real internal resistance of each lithium battery pack.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a parallel circulating current detection and current sharing strategy for a lithium battery system. Background Art

[0002] In order to provide greater energy output, energy storage battery systems are often implemented by connecting multiple battery packs in parallel. Due to the differences in battery consistency and the inconsistency of battery attenuation, parallel systems are prone to problems with inter-battery circulation, which further accelerates battery performance degradation.

[0003] The existing technology of parallel current sharing of battery packs requires additional hardware modules, such as DC / DC, overcurrent protection modules, etc., which increases hardware costs. Summary of the invention

[0004] The purpose of the present invention is to provide a parallel circulating current detection and current balancing strategy for a lithium battery system, so as to solve the problems existing in the prior art, efficiently solve the battery circulating current problem, and do not need to add hardware modules.

[0005] In order to achieve the above object, the solution of the present invention is: A parallel circulating current detection and current balancing strategy for a lithium battery system, comprising a lithium battery system, an inverter and a cloud server; the lithium battery system comprises a plurality of lithium battery packs connected in parallel; the lithium battery pack comprises a battery module and a battery management module, the battery management module having the functions of data acquisition, data upload, charge and discharge management and cell balancing; the battery management module of one lithium battery pack is defined as the host of the lithium battery system, and the other lithium battery packs upload data to the host through a first CAN bus, and the host aggregates the data of all battery packs and uniformly sends the maximum allowable charging current and maximum allowable discharging current of the lithium battery system to the inverter through a second CAN bus; the host communicates with the inverter and applies to the inverter for charging voltage, discharging voltage, charging current and discharging current; the cloud server interacts with the inverter by wireless communication and controls the inverter; the parallel circulating current detection and current balancing strategy is: Step 1, When a lithium battery pack is offline, a 1C current is suddenly applied to it for 10 seconds. , the DC internal resistance pre-stored in the battery management module is obtained , and its calculation formula is: ; in, Indicates The DC internal resistance of a lithium battery pack; Indicates A lithium battery pack is suddenly charged The voltage difference detected before and after; Indicates the health status of the lithium battery pack; Indicates adjustable parameters; Step 2, The lithium battery pack updates the maximum allowed charging current to ,in represents the voltage of the lithium battery system; the total current requested by the host to the inverter is ; Step 3: If the actual charging current of the updated lithium battery pack is greater than the maximum allowable charging current, there is a mismatch problem. The host uploads the flag bit of the circulating current of the lithium battery system to the inverter through the second CAN bus, and the inverter forwards it to the cloud server; Step 4: After receiving the information, the cloud server marks the corresponding lithium battery pack as requiring internal resistance correction, and sends a command to the inverter to add a sudden charge to the lithium battery system according to the operating status of the lithium battery system. The current does not exceed the maximum allowable charging current Then, the cloud server calculates the real internal resistance of each lithium battery pack according to the voltage change of each lithium battery pack. The calculation formula is: ; in, Indicates The actual internal resistance of a lithium battery pack; Indicates Lithium battery pack The sudden current The voltage difference detected before and after; Step 5, the cloud server sends the calculated real internal resistance to each battery management module to update the pre-stored DC internal resistance; Step 6: The cloud server calculates the current The actual internal resistance and the formula in step 1 can be used to reversely infer the value of the adjustable parameter a that is actually matched.

[0006] The battery management module of the lithium battery pack is configured with a power meter, which shows the correspondence between the battery cell voltage, battery cell temperature, SOC status and its maximum allowable charging current and maximum allowable discharging current. The battery management module queries the power meter according to the battery cell voltage, battery cell temperature and SOC status to obtain the maximum allowable charging current and maximum allowable discharging current of the corresponding lithium battery pack; the remaining lithium battery packs except the host upload their maximum allowable charging current and maximum allowable discharging current to the battery management module of the host through the first CAN bus, and the host summarizes them together with its own maximum allowable charging current and maximum allowable discharging current to obtain the maximum allowable charging current and maximum allowable discharging current of the lithium battery system, and uploads them to the inverter through the second CAN bus.

[0007] The cloud server communicates wirelessly with the inverter via WiFi or GPRS.

[0008] After adopting the above technical solution, the present invention has the following technical effects: (1) The present invention can timely detect the battery circulation problem that occurs when the lithium battery system is charging and discharging, and when the battery circulation problem is detected, dynamically adjust the current applied by each lithium battery pack to avoid the continued occurrence of the circulation phenomenon; (2) The present invention can realize that the battery pack with high power stops charging after reaching the full charge state, and the battery pack with low power continues charging after the battery pack with high power reaches the full charge state, and finally realizes that all battery packs are charged to 100%; (3) The present invention can implement the battery circulation protection strategy without adding any hardware modules, thereby protecting the battery and improving the utilization rate of the battery itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A connection block diagram of a specific embodiment of the present invention; Figure 2 is a flow chart of a specific embodiment of the present invention; Figure 3 A relationship diagram of battery data detection, SOC calculation, and maximum allowable charge and discharge current acquisition in a specific embodiment of the present invention; Description of Figure Numbers: 1-lithium battery system; 11-lithium battery pack; 111-battery module; 112-battery management module; 2-inverter; 3-cloud server; 4-first CAN bus; 5-second CAN bus. DETAILED DESCRIPTION

[0010] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0011] refer to Figure 1-3 As shown, the present invention discloses a parallel circulating current detection and current sharing strategy for a lithium battery system, including a lithium battery system 1, an inverter 2 and a cloud server 3; see Figure 1 The lithium battery system 1 includes a plurality of lithium battery packs 11 connected in parallel; the lithium battery pack 11 includes a battery module 111 and a battery management module 112, and the battery management module 112 has functions such as data acquisition (including battery cell voltage, battery cell temperature and charge and discharge current, etc.), data upload, charge and discharge management and battery cell balancing; the battery management module 112 of one lithium battery pack 11 is defined as the host of the lithium battery system 1, and the remaining lithium battery packs 11 are connected through the first CAN (Controller Area Network) bus 4 ( Figure 1 The host collects the data of all battery packs and transmits them uniformly through the second CAN bus 5 ( Figure 1 CAN1 of the host computer sends the maximum allowable charging current (the aggregate value of all battery packs) and the maximum allowable discharging current (the aggregate value of all battery packs) of the lithium battery system 1 to the inverter 2; the host computer communicates with the inverter 2 and requests the charging voltage, discharging voltage, charging current and discharging current from the inverter 2; the cloud server 3 interacts with the inverter 2 through wireless communication and controls the inverter 2; see Figure 2-3 , the parallel circulation detection and uniform strategy is: Step 1, When a lithium battery pack 11 is off the production line, a 1C current is suddenly applied for 10 seconds at every 5% SOC and every 10 degrees Celsius (operating temperature) interval. , the DC internal resistance pre-stored in the battery management module 112 is obtained , and its calculation formula is: ; in, Indicates The DC internal resistance of a lithium battery pack; Indicates A lithium battery pack is suddenly charged The voltage difference detected before and after; Indicates the health status value of the lithium battery pack 11; Indicates an adjustable parameter, the default value is 0.0167; Step 2, The lithium battery pack 11 updates the maximum allowable charging current applied for to ,in represents the voltage of lithium battery system 1; the total current requested by the host to inverter 2 is ; Step 3: If the updated lithium battery pack 11 detects that its actual charging current is greater than the maximum allowable charging current, there is a mismatch problem. The host uploads the flag bit of the circulating current in the lithium battery system 1 to the inverter 2 through the second CAN bus 5, and the inverter 2 forwards it to the cloud server 3; Step 4: After receiving the information, the cloud server 3 marks the corresponding lithium battery pack 11 as requiring internal resistance correction, and sends a command to the inverter 2 to add a sudden charge to the lithium battery system 1 according to the operating status of the lithium battery system 1. The current does not exceed the maximum allowable charging current Then, the cloud server 3 calculates the real internal resistance of each lithium battery pack 11 according to the voltage change of each lithium battery pack 11, and the calculation formula is: ; in, Indicates The actual internal resistance of a lithium battery pack 11; Indicates Lithium battery pack The sudden current The voltage difference detected before and after; Step 5: The cloud server 3 sends the calculated real internal resistance to each battery management module 112 to update the pre-stored DC internal resistance; Step 6: The cloud server 3 calculates the current The actual internal resistance and the formula in step 1 can be used to reversely infer the value of the adjustable parameter a that is actually matched.

[0012] Through the above scheme, the present invention can timely detect the battery circulation problem that occurs when the lithium battery system 1 is charging and discharging, and when the battery circulation problem is detected, dynamically adjust the current applied by each lithium battery pack 11 to avoid the continued occurrence of the circulation phenomenon; the present invention can realize that the high-power battery pack exits charging after reaching the full charge state, and the low-power battery pack continues to charge after the high-power battery pack reaches the full charge state, and finally realizes that all battery packs are charged to 100%; the present invention can implement the battery circulation protection strategy without adding any hardware modules, thereby protecting the battery and improving the utilization rate of the battery itself.

[0013] Specific embodiments of the present invention are shown below.

[0014] The battery management module 112 of the above-mentioned lithium battery pack 11 is configured with a power meter, which shows the correspondence between the battery cell data such as the battery cell voltage, battery cell temperature, SOC status and its maximum allowable charging current and maximum allowable discharging current. The battery management module 112 queries the power meter according to the battery cell voltage, battery cell temperature and SOC status to obtain the maximum allowable charging current and maximum allowable discharging current of the corresponding lithium battery pack 11; the remaining lithium battery packs 11 except the host upload their maximum allowable charging current and maximum allowable discharging current to the battery management module 112 of the host through the first CAN bus 4, and the host summarizes them together with its own maximum allowable charging current and maximum allowable discharging current to obtain the maximum allowable charging current and maximum allowable discharging current of the lithium battery system 1, and uploads them to the inverter 2 through the second CAN bus 5.

[0015] The cloud server 3 communicates wirelessly with the inverter 2 via WiFi or GPRS.

[0016] The above embodiments do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A parallel circulation current detection and current sharing strategy for a lithium battery system, characterized in that: The invention comprises a lithium battery system, an inverter and a cloud server; the lithium battery system comprises a plurality of lithium battery packs connected in parallel; the lithium battery pack comprises a battery module and a battery management module, and the battery management module has the functions of data collection, data upload, charge and discharge management and cell balancing; the battery management module of one lithium battery pack is defined as the host of the lithium battery system, and the other lithium battery packs upload data to the host through a first CAN bus, and the host aggregates the data of all battery packs and uniformly sends the maximum allowable charging current and maximum allowable discharging current of the lithium battery system to the inverter through a second CAN bus; the host communicates with the inverter and applies for charging voltage, discharging voltage, charging current and discharging current from the inverter; the cloud server interacts with the inverter by wireless communication and controls the inverter; the parallel circulating current detection and uniform strategy are as follows: Step 1, When a lithium battery pack is offline, a 1C current is suddenly applied to it for 10 seconds. , the DC internal resistance pre-stored in the battery management module is obtained , and its calculation formula is: ； in, Indicates The DC internal resistance of a lithium battery pack; Indicates A lithium battery pack is suddenly charged The voltage difference detected before and after; Indicates the health status of the lithium battery pack; Indicates adjustable parameters; Step 2, The lithium battery pack updates the maximum allowed charging current to ,in represents the voltage of the lithium battery system; the total current requested by the host to the inverter is ; Step 3: If the actual charging current of the updated lithium battery pack is greater than the maximum allowable charging current, there is a mismatch problem. The host uploads the flag bit of the circulating current of the lithium battery system to the inverter through the second CAN bus, and the inverter forwards it to the cloud server; Step 4: After receiving the information, the cloud server marks the corresponding lithium battery pack as requiring internal resistance correction, and sends a command to the inverter to add a sudden charge to the lithium battery system according to the operating status of the lithium battery system. The current does not exceed the maximum allowable charging current Then, the cloud server calculates the real internal resistance of each lithium battery pack according to the voltage change of each lithium battery pack. The calculation formula is: ； in, Indicates The actual internal resistance of a lithium battery pack; Indicates Lithium battery pack The sudden current The voltage difference detected before and after; Step 5, the cloud server sends the calculated real internal resistance to each battery management module to update the pre-stored DC internal resistance; Step 6: The cloud server calculates the current The actual internal resistance and the formula in step 1 can be used to reversely infer the value of the adjustable parameter a that is actually matched.

2. The parallel circulating current detection and current sharing strategy of the lithium battery system according to claim 1, characterized in that: The battery management module of the lithium battery pack is configured with a power meter, which shows the correspondence between the battery cell voltage, battery cell temperature, SOC status and its maximum allowable charging current and maximum allowable discharging current. The battery management module queries the power meter according to the battery cell voltage, battery cell temperature and SOC status to obtain the maximum allowable charging current and maximum allowable discharging current of the corresponding lithium battery pack; the remaining lithium battery packs except the host upload their maximum allowable charging current and maximum allowable discharging current to the battery management module of the host through the first CAN bus, and the host summarizes them together with its own maximum allowable charging current and maximum allowable discharging current to obtain the maximum allowable charging current and maximum allowable discharging current of the lithium battery system, and uploads them to the inverter through the second CAN bus.

3. The parallel circulating current detection and current sharing strategy of the lithium battery system according to claim 1, characterized in that: The cloud server communicates wirelessly with the inverter via WiFi or GPRS.

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