Battery pack energy one-time transfer method and device

Abstract

The invention discloses a battery pack energy one-time transfer method and device, relates to the technical field of energy storage, and is used for solving the problem of unbalanced energy of each single battery in a series battery pack. The device comprises a series battery pack, a central controller, a multi-way switch A, a multi-way switch B, a current sensor, an SOC detection module, a topology main circuit and a redundant battery pack. According to the method, a capacity efficiency equation is used for correcting an energy state calculation error caused by charge and discharge rate change of a single battery, and a charge and discharge energy model and a transfer current matrix are established in combination with internal loss of the battery. According to the method, each battery can reach the charge-discharge cut-off voltage at the same time in the same charge-discharge period. When the central controller detects that the battery energy is unbalanced through the SOC detection module, the battery needing energy transfer is selected through the multi-way switch A and the multi-way switch B, and energy transfer is conducted through the main circuit and the redundant battery. According to the invention, each battery can only carry out one-time energy transfer in the charging and discharging process, and compared with a traditional battery pack active equalization method, the dynamic loss in the equalization process is reduced, and the damage of repeated charging and discharging to the service life of the battery is reduced.

Description

Technical Field

[0001] This invention belongs to the field of battery pack energy management, specifically a method and apparatus for primary energy transfer in a battery pack. Background Technology

[0002] Energy storage technology is a crucial strategic tool for driving the energy revolution, addressing climate change, and promoting economic transformation and upgrading. Vigorously developing energy storage technology is of great significance for solving the volatility and intermittency of renewable energy, promoting energy transition and emission reduction targets, and improving energy efficiency and security. However, due to differences in manufacturing and usage, energy storage batteries have long suffered from poor consistency, becoming a bottleneck in the development of energy storage technology. Battery energy management technology is a key method to overcome this bottleneck. Based on different energy dissipation methods, it can be divided into passive balancing and active balancing. The former dissipates excess energy from individual battery cells through shunt resistors, causing additional thermal management problems; the latter achieves energy transfer through energy storage elements and has been more widely used due to its economic efficiency and feasibility. Using active balancing for battery pack energy management can eliminate battery pack energy inconsistency in a very short time, but this method still has many drawbacks. First, the battery pack balancing process is repeated continuously, and battery pack energy flows repeatedly in the switching transistors, resulting in significant dynamic losses. Second, repeated charging and discharging of the battery pack within the same cycle accelerates battery aging and reduces the overall lifespan of the battery pack. This invention provides a new method and device for primary energy transfer of battery packs through redundant batteries and DC chopper circuits for energy management. Summary of the Invention

[0003] The purpose of this invention is to design a method and apparatus for primary energy transfer of a battery pack through redundant batteries and DC chopper circuits for energy management. This avoids repeated charging and discharging of individual cells by active equalization, reduces damage to battery life, and lowers dynamic losses during the energy transfer process.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method and apparatus for primary energy transfer of a battery pack, the system comprising a series battery pack (1), a central controller (2), a multiplexer A (3), a multiplexer B (4), a SOC detection module (5), a topology main circuit (6), a redundant battery (7), and a current sensor (17). The SOC detection module (5) is used to detect the state of each individual battery cell; the left side of the topology main circuit (6) is connected to the series battery pack (1) through multiplexers A (3) and B (4); the current sensor (17) is installed between the topology main circuit (6) and multiplexer A (3); the right side of the topology main circuit (6) is connected in parallel with the redundant battery (7); the topology main circuit includes an energy storage inductor (8), switching transistors M (9), Q (10), N (11), freewheeling diodes D1 (14), D2 (16), D3 (15), and filter capacitors C1 (12) and C2 (13) connected in parallel on both sides of the series battery pack (1) and the redundant battery (7).

[0006] As a specific embodiment of a method and apparatus for primary energy transfer in a battery pack, the system can accurately calculate the energy state of each individual battery cell based on the actual charge and discharge rate of the individual cells.

[0007]

[0008] Among them U n1 U n2 Let i be the starting and ending voltages of the nth individual cell. Tn T1 represents the actual current flowing through the nth individual cell during the entire charging and discharging process, and T2 represents the start and end times of operation for the individual cell. E represents the corrected capacity of a single battery cell at the current charging rate. n For the nth individual cell, SOC n1 SOC n2 The initial SOC and cutoff SOC of the nth individual cell during charging and discharging.

[0009] As a specific embodiment of a method and apparatus for primary energy transfer in a battery pack, the system is capable of establishing a primary energy transfer model for the battery pack:

[0010]

[0011] Where i n Let t be the transfer current of the nth battery. n Let be the transfer time corresponding to this transfer current. This mathematical model can be represented as a current transfer matrix:

[0012] I·T=E

[0013] The current transfer matrix has 2n variables and n degrees of freedom constraints, meaning that the matrix forms an underdetermined system of equations. One solution is taken as the current transfer scheme in energy transfer.

[0014] As a specific embodiment of a battery pack energy transfer method and device, the current sensor and the SOC detection module send the detection signal to the central controller. The SOC detection module can detect the state of each individual battery cell, and the current sensor can detect the magnitude of the transfer current.

[0015] As a specific embodiment of a battery pack energy transfer method and device, the left side of the main circuit is connected in parallel with the series battery pack through multiplexer A and multiplexer B, and the controller can select the battery connected in parallel to the main circuit through multiplexer A and multiplexer B.

[0016] As a specific embodiment of a battery pack energy transfer method and device, the current sensor sends data to the central controller to realize feedback control of the transfer current, so that the battery is charged and discharged according to the calculated current transfer scheme.

[0017] As a specific embodiment of a battery pack energy transfer method and device, depending on the direction of energy transfer, the central controller can change the state of switches M, Q, and N to make the main circuit of the topology be in two different states: Buck circuit and Boost circuit.

[0018] As a specific embodiment of a method and apparatus for primary energy transfer of a battery pack, the right side of the main circuit of the topology consists of redundant batteries of the same type connected in series.

[0019] In a specific embodiment of a battery pack energy transfer method and device, filter capacitors C1 and C2 are connected in parallel on both sides of the individual cell and the redundant cell.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention performs energy transfer only once for each individual battery cell during the energy process, avoiding the lifespan damage caused by repeated charging and discharging of the battery due to active balancing.

[0022] 2. This invention avoids energy flowing through the switching transistor multiple times during the energy process, thus reducing dynamic energy loss. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a primary energy transfer system for a battery pack according to the present invention.

[0024] Figure 2 This is a flowchart of a battery pack energy transfer system strategy in this invention.

[0025] Figure 3 The charging simulation results are for a battery pack energy transfer method and device according to the present invention.

[0026] Figure 4 The discharge simulation results of a battery pack energy transfer method and device according to the present invention are shown below.

[0027] Legend: 1. Series battery pack; 2. Central controller; 3. Multiplexer A; 4. Multiplexer B; 5. SOC detection module; 6. Main circuit topology; 7. Redundant battery; 8. Energy storage inductor; 9. Switch M; 10. Switch Q; 11. Switch N; 12. Filter capacitor C1; 13. Filter capacitor C2; 14. Freewheeling diode D1; 15. Freewheeling diode D3; 16. Freewheeling diode D2; 17. Current sensor. Detailed Implementation

[0028] The technical solutions 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.

[0029] Reference Figure 1 A battery pack energy management system and method are described. In the device, the series battery pack (1) is connected in parallel with the left side of the topology main circuit (6) through multiplexer A (3) and multiplexer B (4). The multiplexer can select the individual battery cells for energy transfer. A current sensor (17) is set between multiplexer A (3) and the topology to collect the transfer current and send it to the central controller (2) for current control. The SOC detection module (5) is connected in parallel across the series battery pack (1) to detect the status of each individual battery cell. The right side of the topology main circuit (6) is connected in parallel with the redundant battery (7). The central controller (2) can change the two states of the topology main circuit (6) by changing the switching transistors M (9), N (11), and Q (10) in the topology main circuit (6). Filter capacitors C1 (12) and C2 (13) are connected in parallel with the redundant battery (7) and the series battery pack (1), respectively. Diodes D1 (14), D2 (16), and D3 (15) serve as freewheeling diodes for the topology main circuit (6).

[0030] In summary, during use, the state of each individual battery cell is first detected using the SOC detection module. When battery imbalance reaches a certain level, refer to... Figure 2The energy state of each individual battery is accurately calculated based on its actual charge and discharge rate. A single-cycle energy transfer model for the battery pack is established, and the energy transfer matrix is ​​solved to derive the transfer current scheme. The magnitude of the transfer current is controlled by the main circuit topology. The batteries requiring energy transfer are selected using switch matrices A and B and connected in parallel with the main circuit topology. The main circuit topology has two different operating modes: when energy is transferred from redundant batteries to individual batteries, it operates in Buck mode, with switches N and Q remaining on. The central controller receives signals from the current sensor and controls the transfer current magnitude by controlling switch M, during which freewheeling diode D2 flows. When energy is transferred from individual batteries to redundant batteries, it operates in Boost mode, with switches M and Q remaining off. The central controller receives signals from the current sensor and controls the transfer current magnitude by controlling switch N, during which freewheeling diodes D1 and D3 flow. During bidirectional energy transfer, filter capacitors C1 and C2 stabilize the transfer current. Once all individual batteries in the battery pack reach their charge / discharge cutoff voltage simultaneously, multiplexers A and B are turned off, ending the energy transfer.

[0031] The SOC curves of each battery during the charging energy transfer process are as follows: Figure 3 As shown, the final charging time was 459.99 seconds, and the SOC values ​​of each battery reached 100% almost simultaneously at the end of charging. If no energy transfer measures were taken during charging, the SOC values ​​of each individual battery should have been 98.2%, 98.7%, 99.4%, 99.7%, and 100% when charging stopped. The results show that because energy transfer was performed on the battery pack during charging, the charging cutoff time was extended, and obviously the entire battery pack was charged with more energy.

[0032] The SOC curves of each battery during the discharge energy transfer process are as follows: Figure 4 As shown, the final discharge time was 496.88 seconds, and the SOC values ​​of each battery reached 20% almost simultaneously at the end of the discharge. If no energy transfer measures were taken during the discharge process, the SOC values ​​of each individual battery at the end of the discharge would be: 21.5%, 21.3%, 20.7%, 20.2%, and 20%. The results show that because energy transfer was performed on the battery pack during the discharge process, the discharge cutoff time was extended, and the entire battery pack obviously has a stronger discharge capacity.

[0033] The above description is only a preferred embodiment of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made in accordance with the technical solution and inventive concept of the present invention should be included within the scope of protection of the present invention.

Claims

1. A specific embodiment of a battery energy one-time transfer method and device, which can accurately calculate the energy state of each single battery according to the actual charge and discharge rate of the single battery. wherein U n1 , U n2 is the working start and end voltage of the nth single battery, i Tn is the actual current flowing through the nth single battery during the entire charging and discharging process, T1 and T2 are the working start and end time of the single battery, is the capacity of the single battery after correction at the current charging rate, E n is the state of energy of the nth single battery, SOC n1 , SOC n2 is the initial SOC and end SOC of the nth single battery during charging and discharging. A specific embodiment of a battery energy one-time transfer method and device, which can establish a battery one-time energy transfer model according to the energy state of each single battery obtained in the foregoing. where i n is the transfer current of the nth battery, t n is the transfer time corresponding to the transfer current. The mathematical model can be represented as a current transfer matrix: I·T=E The number of variables in the current transfer matrix is 2n, and the degree of freedom constraint is n, that is, the matrix forms an underdetermined equation group, and one of the solutions is taken as the current transfer scheme in energy transfer.

2. A battery pack energy management system and method characterized by, The system comprises a series battery (1), a central controller (2), a multi-path switch A (3), a multi-path switch B (4), an SOC detection module (5), a topology main circuit (6), a redundant battery (7), and a current sensor (17). The SOC detection module (5) is used to detect the state of each single battery; the topology main circuit (6) is connected to the series battery (1) through the multi-path switch A (3) and the multi-path switch B (4) on the left side; the current sensor (17) is installed between the topology main circuit (6) and the multi-path switch A (3); the topology main circuit (6) is connected in parallel with the redundant battery (7) on the right side; the topology main circuit comprises an energy storage inductor (8), switch tubes M (9), Q (10), N, (11), freewheeling diodes D1 (14), D2 (17), D3 (15), filter capacitors C1 (12), C2 (13) connected in parallel on both sides of the series battery (1) and the redundant battery (7).

3. The battery pack energy management system and method of claim 2, wherein: The current sensor and the SOC detection module send detection signals to the central controller, the SOC detection module can detect the state of each single battery, and the current sensor can detect the size of the transferred current.

4. The battery pack energy management system and method of claim 2, wherein: The main circuit is connected in parallel with the series battery through the multi-path switch A and the multi-path switch B on the left side, and the controller can select the battery connected in parallel with the topology main circuit through the multi-path switch A and the multi-path switch B.

5. The battery pack energy management system and method of claim 2, wherein: The current sensor sends data to the central controller to realize feedback control of the transferred current, so that the battery charges and discharges according to the current transfer scheme calculated in the foregoing.

6. The battery pack energy management system and method of claim 2, wherein: According to the direction of energy transfer, the central controller can change the state of the switches M, Q, and N to make the topology main circuit in two different states of Buck circuit and Boost circuit.

7. The battery pack energy management system and method of claim 2, wherein: The right side of the topology main circuit is composed of the same type of batteries in series to form a redundant battery.

8. The battery pack energy management system and method of claim 2, wherein: The filter capacitors C1 and C2 are connected in parallel on both sides of the single battery and the redundant battery.

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