A novel reconfigurable battery topology and shunt equalization method

Abstract

The application discloses a novel reconfigurable battery topology and a shunt equalization method, which comprises: a plurality of battery modules connected in sequence; each battery module is composed of a battery Bi, a first switch S i1 , a second switch S i2 , a third switch P i1 and a fourth switch P i2 , wherein one battery module B n is additionally connected with a bypass switch; the switch S i1 is used for battery series connection, the switch S i2 is used for battery bypass, the switches P i1 and P i2 are used for battery parallel connection, and the series connection, parallel connection, bypass and hybrid connection functions of the battery module can be realized. The whole battery pack is connected in series, when discharging, two battery modules with the lowest state of charge are connected in parallel to reduce the reduction speed of the state of charge, when charging, two battery modules with the highest state of charge are connected in parallel to reduce the increase speed of the state of charge, and finally the state of charge of all battery modules is equalized. The application can improve the reliability of the battery pack, reduce the output voltage fluctuation, equalize the state of charge of the battery module and realize the maximum capacity utilization of the battery pack.

Description

Technical Field

[0001] This invention belongs to the field of battery energy storage technology, and in particular relates to a novel reconfigurable battery topology and current balancing method. Background Technology

[0002] With rapid social development and continuous modernization, the demand for electricity in cities and towns is increasing daily. Because traditional power generation relies on fossil fuels that are harmful to the environment and non-renewable, the government is vigorously promoting new energy power generation policies such as wind power and solar power. In new energy power generation systems, energy storage systems are crucial components, with battery energy storage systems occupying a key position. Battery energy storage systems can function as both a "source" and a "load," discharging when wind and solar power generation is insufficient and storing electrical energy when wind and solar power generation is excessive. They can also be used for peak shaving and valley filling, smoothing out power output and playing a vital role in maintaining the stability of the power system.

[0003] Typically, a single battery cell has a voltage of only a few volts, which is insufficient to meet the voltage and capacity requirements of an energy storage system. Therefore, tens of thousands of batteries need to be connected in series or parallel to form a battery pack. Due to internal and external factors such as internal resistance, manufacturing differences, and the external environment, the state of charge (SOC) of the individual cells in the battery pack cannot remain balanced during operation, and the difference in SOC will increase over time, creating the "barrel effect." The existence of the "barrel effect" prevents the battery pack's capacity from being maximized because of the uneven SOC among the cells. To avoid overcharging and over-discharging affecting battery life, the entire battery pack must stop charging when one cell is fully charged, and the entire battery pack must stop discharging when one cell is fully discharged. This greatly affects the efficiency of the battery pack, thus necessitating battery pack balancing.

[0004] Traditional balancing methods include passive and active balancing. Passive balancing dissipates excess energy from cells with a high state of charge (SOC) by connecting parallel resistors, while active balancing uses energy storage devices to transfer energy between cells. Dissipating excess energy reduces the energy utilization rate of the battery pack, while transferring energy between cells through energy storage devices reduces balancing efficiency. Reconfigurable battery packs are considered another solution to these problems. By changing the switching state of the cells, the operating state of the battery pack can be altered, improving performance and extending its lifespan. However, the flexibility and reliability of reconfigurable battery packs are contradictory, and the bypassing and re-entry of individual cells causes significant fluctuations in the output voltage of the battery cluster. Existing reconfigurable battery topologies struggle to simultaneously achieve high reliability, low output voltage fluctuations, and high balancing efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a novel reconfigurable battery topology and current balancing method to solve the problems existing in the prior art.

[0006] To achieve the above objectives, in one aspect, the present invention provides a novel reconfigurable battery topology, comprising:

[0007] Several battery modules connected in sequence;

[0008] Each of the battery modules consists of battery B. i First switch S i1 Second switch S i2 Third switch P i1 and the fourth switch P i2 Composition, including one battery module B n An additional bypass switch is also connected;

[0009] The first switch S i1 For battery series connection, the second switch S i2 The third switch P is used for battery bypass. i1 and the fourth switch P i2 Used for parallel connection of batteries, the entire battery pack is initially in series; when battery B i When connected in series, the first switch S i1 Close, second switch S i2 Third switch P i1 and the fourth switch P i2 Off; when the battery B i When connected in parallel, the third switch P i1 and the fourth P i2 Close, first switch S i1 Second switch S i2 Off; when the battery B i When bypassing, the second switch S i2 Close, first switch S i1 Third switch P i1 and the fourth switch P i2 Turn off.

[0010] On the other hand, the present invention provides a novel reconfigurable battery topology shunt equalization method, comprising the following steps:

[0011] S1. Determine the operating status of the battery pack;

[0012] S2. Determine if there is a malfunctioning battery module; if so, bypass it.

[0013] S3. Obtain the state of charge of each battery module;

[0014] S4. Perform current balancing on the battery pack;

[0015] S5. Repeat steps S3 and S4 until each battery module reaches the equalization accuracy.

[0016] Optionally, in S1,

[0017] The battery pack operates in two states: charging and discharging.

[0018] Optionally, in S2,

[0019] The battery modules that cannot work properly are: battery modules that are fully charged when charging, battery modules whose state of charge is lower than a set threshold when discharging, and battery modules that cannot work due to short circuit or open circuit faults.

[0020] Optionally, the specific steps of S4 are as follows:

[0021] S401: Sort the state of charge of all battery modules;

[0022] S402: Identify the two battery modules with the lowest state of charge and the two battery modules with the highest state of charge;

[0023] S403: Connect two battery modules with the lowest state of charge in parallel, and connect two battery modules with the highest state of charge in parallel;

[0024] S404: Discharging until the state of charge (SOC) of the remaining battery modules is lower than the SOC of the two battery modules with the lowest SOC; charging until the SOC of the remaining battery modules is higher than the SOC of the two battery modules with the highest SOC. Optionally, in S403,

[0025] The initial state of the switch is S i1 Closed, S i2 P i1 and P i2 Off, battery B i and B i+1 When connected in parallel, switch P i1 P i2 and switch P (i+1)1 P (i+1)2 Close, switch S (i+1)1 Off; when battery B i and B j When (i, j are not equal and not connected) in parallel, switch P i1 P i2 and switch P j1 P j2 Close, switch S j2 Close, switch S j1 Off; Battery B n When connected in parallel, switch S(n+1)1 When switched off, the output voltage is always the sum of the voltages of n-1 batteries.

[0026] The technical effects of this invention are as follows:

[0027] In the reconfigurable battery topology proposed in this invention, each battery module is configured with four switches, wherein battery module B n An additional bypass switch is configured. Switch S i1 Used for battery series connection, switch S i2 Used for battery bypass, switch P i1 and P i2 This invention is used for parallel battery connection and can perform series, parallel, bypass, and mixed connection functions for battery modules. The entire battery pack operates in series. During discharge, the two battery modules with the lowest state of charge (SOC) are connected in parallel to reduce the rate of SOC decrease. During charging, the two battery modules with the highest SOC are connected in parallel to reduce the rate of SOC increase, ultimately achieving a balanced SOC across all battery modules. This invention improves battery pack reliability, reduces output voltage fluctuations, and balances the SOC of the battery modules to maximize battery pack capacity utilization.

[0028] The novel reconfigurable battery topology proposed in this invention has high flexibility and high fault tolerance, which can improve the reliability of the circuit. Simulation results show that the current balancing method based on the novel reconfigurable battery topology can provide a more stable output voltage while achieving battery balancing and improving the capacity utilization of the battery pack. Attached Figure Description

[0029] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1 This is a novel reconfigurable battery topology in an embodiment of the present invention;

[0031] Figure 2 This is a series fault-tolerant novel reconfigurable battery topology in the embodiments of the present invention;

[0032] Figure 3 Parallel fault tolerance of the novel reconfigurable battery topology in this embodiment of the invention;

[0033] Figure 4 This is a flowchart illustrating the operation of the novel reconfigurable battery topology in this embodiment of the invention.

[0034] Figure 5 This is a schematic diagram of current balancing during the discharge process in an embodiment of the present invention;

[0035] Figure 6The state-of-charge curves of each battery in the battery pack during the discharge equalization process in this embodiment of the invention are shown.

[0036] Figure 7 The state-of-charge curves of each battery in the battery pack during the charging equalization process in this embodiment of the invention are shown.

[0037] Figure 8 This is the output voltage curve of the battery pack during the discharge equalization process in an embodiment of the present invention. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0040] To address the shortcomings of existing technologies, this invention proposes a novel reconfigurable battery topology and current balancing method. The aim is to achieve equalization among battery modules while ensuring that at any given time, one battery module is always connected in parallel with the others, maintaining a fixed relationship between the battery pack output voltage and the battery module output voltage, resulting in minimal voltage fluctuations. Furthermore, compared to existing reconfigurable battery topologies, this topology uses only four switches to complete series, parallel, bypass, and current balancing strategies for a single battery module, while other existing topologies require five or even six switches. This reduces the number of switches while maintaining battery pack flexibility, resulting in higher battery pack reliability.

[0041] This invention is achieved through the following technical solution:

[0042] This invention discloses a novel reconfigurable battery topology, the circuit topology comprising:

[0043] Each battery module is equipped with four switches, battery module B n An additional bypass switch is configured, switch S i1 Used for battery series connection, switch S i2 Used for battery bypass, switch P i1 and P i2 Used for parallel connection of batteries, the entire battery pack is initially in series. When battery module B i When connected in series, switch S i1 Close, switch S i2 P i1 and P i2 Off; when battery module Bi When connected in parallel, switch P i1 and P i2 Close, switch S i1 and S i2 Off; when battery module B i When bypassing, switch S i2 Close, switch S i1 P i1 and P i2 Turn off.

[0044] A current balancing method for a novel reconfigurable battery topology includes the following steps:

[0045] Step 1: Determine the operating status of the battery pack;

[0046] Step 2: Determine if there are any malfunctioning battery modules; if so, bypass them.

[0047] Step 3: Obtain the state of charge of each battery module;

[0048] Step 4: Equalize the battery pack;

[0049] Step 5: Repeat steps 3 and 4 until each battery module reaches the equalization accuracy.

[0050] As a further improvement of the present invention, in step 1...

[0051] The battery pack operates in two states: charging and discharging.

[0052] As a further improvement of the present invention, in step 2...

[0053] A battery module that cannot function properly refers to a battery module that is fully charged when charging, a battery module whose state of charge is below a set threshold when discharging, or a battery module that cannot function due to faults such as short circuits or open circuits.

[0054] As a further improvement of the present invention, in step 4, the charging (discharging) equalization method specifically includes:

[0055] Step 4.1: Sort the state of charge of all battery modules;

[0056] Step 4.2: Identify the two battery modules with the lowest (highest) state of charge;

[0057] Step 4.3: Connect the two battery modules with the lowest (highest) state of charge in parallel;

[0058] Step 4.4: Discharge (charge) until the two battery modules with the lowest (highest) state of charge change.

[0059] In step 4.3, the initial state of the switch is S. i1 Closed, S i2 P i1 and P i2 Battery module B is off. i and B i+1 When connected in parallel, switch P i1 P i2 and switch P (i+1)1 P (i+1)2 Close, switch S (i+1)1 Off; when battery module B i and B j When (i, j are not equal and not connected) in parallel, switch P i1 P i2 and switch P j1 P j2 Close, switch S j2 Close, switch S j1 Shutdown; Battery Module B n When connected in parallel, switch S (n+1)1 Off. The output voltage is always the sum of the voltages of n-1 battery modules.

[0060] Example 1

[0061] like Figure 1-7 As shown, this embodiment provides a novel reconfigurable battery topology and current balancing method, including:

[0062] like Figure 1 As shown, the present invention provides a novel reconfigurable battery topology, specifically including:

[0063] Each battery module is equipped with four switches, battery module B n An additional bypass switch is configured, switch S i1 Used for battery series connection, switch S i2 Used for battery bypass, switch P i1 and P i2 Used for parallel connection of batteries, the entire battery pack is initially in series.

[0064] like Figure 2 As shown, when battery module B i When connected in series, switch S i1 Close, switch S i2 P i1 and P i2 Off; when battery module B i When using series bypass, switch S i2 Close, switch S i1 P i1 and P i2 Turn off.

[0065] like Figure 3 As shown, when battery module B i When connected in parallel, switch P i1 and P i2 Close, switch S i1 and S i2 Off; when battery module B i When using parallel bypass, switch S i1 S i2 P i1 and P i2 Turn off.

[0066] like Figure 4 As shown, this invention provides a current balancing method based on a novel reconfigurable battery topology, specifically including:

[0067] Step 1: Determine the operating status of the battery pack; the operating status of the battery pack includes two states: discharging and charging.

[0068] Step 2: Determine if there are any battery modules that are not working properly. If so, bypass them. Among them, battery modules that are not working properly refer to battery modules that are fully charged during charging, battery modules whose state of charge is lower than the set threshold during discharging, and battery modules that are not working due to faults such as short circuits or open circuits.

[0069] Step 3: Obtain the state of charge of each battery module;

[0070] Step 4: Equalize the battery pack;

[0071] like Figure 5 As shown, taking the discharge equalization process as an example, it specifically includes:

[0072] Step 4.1: Sort the state of charge of all battery modules;

[0073] Step 4.2: Identify the two battery modules with the lowest state of charge; at this point, battery modules B3 and B4 have the lowest state of charge.

[0074] Step 4.3: Connect the two battery modules with the lowest state of charge in parallel; control switch P 31 P 32 and switch P 41 P 42 Close, switch S 41 Turn off the switch while keeping the other switches in the same state, so that the two battery modules B3 and B4 with the lowest state of charge are connected in parallel for shunt discharge.

[0075] Step 4.4: Discharge until the two battery modules with the lowest state of charge change, that is, discharge until the state of charge of the remaining battery modules is lower than that of the two battery modules with the lowest state of charge; after discharging for a period of time, the two battery modules with the lowest state of charge become B2 and B4.

[0076] Step 5: Repeat steps 3 and 4 until each battery module reaches the equalization accuracy.

[0077] Based on MATLAB / Simulink, this paper simulates the current balancing process of a reconfigurable battery pack consisting of four cells. Figure 6 , Figure 7 and Figure 8 This invention demonstrates that the novel reconfigurable battery topology and current balancing method improved by this invention can maximize the battery pack capacity utilization and provide a stable output voltage.

[0078] In the reconfigurable battery topology proposed in this invention, each battery module is configured with four switches, wherein battery module B n An additional bypass switch is configured. Switch S i1 Used for battery series connection, switch S i2 Used for battery bypass, switch P i1 and P i2 This invention is used for parallel battery connection and can perform series, parallel, bypass, and mixed connection functions for battery modules. The entire battery pack operates in series. During discharge, the two battery modules with the lowest state of charge (SOC) are connected in parallel to reduce the rate of SOC decrease. During charging, the two battery modules with the highest SOC are connected in parallel to reduce the rate of SOC increase, ultimately achieving a balanced SOC across all battery modules. This invention improves battery pack reliability, reduces output voltage fluctuations, and balances the SOC of the battery modules to maximize battery pack capacity utilization.

[0079] The novel reconfigurable battery topology proposed in this invention has high flexibility and high fault tolerance, which can improve the reliability of the circuit. Simulation results show that the current balancing method based on the novel reconfigurable battery topology can provide a more stable output voltage while achieving battery balancing and improving the capacity utilization of the battery pack.

[0080] The above description is merely a preferred 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.

Claims

1. A novel reconfigurable battery topology current balancing method, characterized in that, include: The novel reconfigurable battery topology includes: Several battery modules connected in sequence; Each of the battery modules is composed of a battery. Bi First switch Second switch Third switch and the fourth switch Composition, including one battery module Bn An additional bypass switch is also connected; The first switch For battery series connection, the second switch The third switch is used for battery bypass. and the fourth switch Used for parallel connection of batteries, the entire battery pack is initially in series; when the batteries Bi When connected in series, the first switch Close, second switch Third switch and the fourth switch Off; when the battery Bi When connected in parallel, the third switch and the fourth Close, first switch Second switch Off; when the battery Bi When bypassing, the second switch Close, first switch Third switch and the fourth switch Turn off; The novel reconfigurable battery topology is configured to perform state-of-charge balancing according to the following shunting balancing method, which includes the following steps: S1. Determine the operating status of the battery pack; S2. Determine if there is a malfunctioning battery module; if so, bypass it. S3. Obtain the state of charge of each battery module; S4. Perform current balancing on the battery pack; S5. Repeat S3 and S4 until each battery module reaches the equalization accuracy; The specific steps of S4 are as follows: S401: Sort the state of charge of all battery modules; S402: Identify the two battery modules with the lowest state of charge and the two battery modules with the highest state of charge; S403: Connect two battery modules with the lowest state of charge in parallel, and connect two battery modules with the highest state of charge in parallel; S404: Discharge until the state of charge of the remaining battery modules is lower than the state of charge of the two battery modules with the lowest state of charge, and charge until the state of charge of the remaining battery modules is higher than the state of charge of the two battery modules with the highest state of charge.

2. The novel reconfigurable battery topology shunt equalization method according to claim 1, characterized in that, In S1, The battery pack operates in two states: charging and discharging.

3. The novel reconfigurable battery topology shunt equalization method according to claim 1, characterized in that, In S2, The battery modules that cannot work properly are: battery modules that are fully charged when charging, battery modules whose state of charge is lower than a set threshold when discharging, and battery modules that cannot work due to short circuit or open circuit faults.

4. The novel reconfigurable battery topology shunt equalization method according to claim 1, characterized in that, In S403, The initial state of the switch is closure, , and Off, battery and When connected in parallel, the switch , and switch , Close, switch Off; when the battery and When connected in parallel, the switch , and switch , Close, switch Close, switch Off; battery When connected in parallel, the switch When switched off, the output voltage is always the sum of the voltages of n-1 batteries.

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