Energy storage cell voltage-sharing control circuit, control method and battery management system

Abstract

The invention discloses an energy storage cell voltage-sharing control circuit, a control method and a battery management system in the technical field of battery energy storage. The circuit comprises a battery module, an acquisition module, a control module, a voltage-sharing module and an auxiliary module, the battery module comprises a plurality of battery cells connected in series; the acquisition module is used for monitoring data of each battery cell; the control module is used for calculating a voltage value needing to be adjusted based on the data of the acquisition module according to a preset voltage-sharing target and a current battery cell state, and sending an instruction to the voltage-sharing module for execution; the voltage-sharing module is used for adjusting the voltage of the battery cell in the battery module according to the instruction of the control module; the auxiliary module is used for judging a charging mode and adjusting charging parameters of the voltage-sharing module based on a constant-voltage output model. According to the scheme, the equalization speed is higher, the equalization precision is higher, the service life of the battery pack is prolonged, and the overall performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery energy storage, and specifically relates to an energy storage cell voltage equalization control circuit, a control method and a battery management system. Background Art

[0002] In energy storage battery systems, cell balancing technology is crucial. It ensures that each battery cell can maintain a similar voltage level, thereby improving the performance and life of the entire battery pack. However, in practical applications, cell balancing technology also faces some challenges.

[0003] In the prior art, the voltage balancing control of energy storage cells mainly relies on the active or passive balancing strategy of the battery management system (BMS). Passive balancing usually releases the power of cells with higher voltage in the form of heat energy through resistor discharge, so as to gain more charging time for other cells. However, when the number of cells is large, this method will not only cause a waste of power, but also a relatively slow balancing speed, because the power is gradually reduced through heat dissipation. In addition, passive balancing will also generate heat, resulting in reduced system efficiency and may even cause thermal damage to the cells. Although active balancing can speed up the balancing speed by transferring the power of high-voltage cells to low-voltage cells, reflux is prone to occur during the balancing process, which will lead to reduced efficiency of active balancing and may even cause additional energy loss and cell damage.

[0004] Therefore, there is an urgent need for an energy storage cell voltage equalization control circuit, control method and battery management system that can improve the equalization speed and overall energy efficiency. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide an energy storage cell voltage equalization control circuit, a control method and a battery management system, which can reduce the occurrence of backflow phenomenon and achieve more efficient equalization.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The energy storage cell voltage balancing control circuit includes a battery module, a collection module, a control module, a voltage balancing module and an auxiliary module;

[0008] The battery module includes a number of battery cells connected in series;

[0009] The acquisition module is used to monitor the data of each battery cell;

[0010] The control module is used to calculate the voltage value that needs to be adjusted based on the data of the acquisition module, according to the preset voltage balancing target and the current battery cell status, and send instructions to the voltage balancing module for execution;

[0011] The voltage balancing module is used to adjust the voltage of the cells in the battery module according to the instructions of the control module;

[0012] The auxiliary module is used to set the constant voltage threshold value U 恒 And the maximum voltage value U of the collected battery mul Determine the charging method of the voltage balancing module; if U mul Less than U 恒 , then the voltage balancing module is controlled to adopt constant current charging; if U mul Greater than or equal to U 恒 , the voltage balancing module is controlled to adopt constant voltage charging, and the charging parameters of the voltage balancing module are adjusted based on the constant voltage output model; the equation of the constant voltage output model is:

[0013]

[0014] Where, η1 and η2 are the inner phase shift duty cycle and the outer phase shift duty cycle respectively, U′ (t) is the instantaneous value of the output voltage sampled at time t, U′ (t+1) is the predicted instantaneous value of the output voltage after one switching cycle, i′ (t) is the instantaneous value of the output current sampled at time t, C2 is the output side capacitor, f s is the switching frequency, L is the inductance, u i(t) is the instantaneous value of the input voltage at time t.

[0015] Furthermore, the preset constant voltage threshold value U 恒 Determine based on the following steps: Obtain the overall temperature T of the battery module to determine the input voltage threshold value U of the high-voltage battery cell to the low-voltage battery cell 恒 , if T1≤T≤T2, then set U 恒 =U T1 , T1 is the low temperature threshold value, T2 is the high temperature threshold value, U T1 is the maximum input voltage at the set normal temperature; if T<T1, the low temperature interval where T is located is determined based on the low temperature interval division result, and the maximum input voltage in the low temperature interval where T is located is used as U 恒 If T>T2, the high temperature interval where T is located is determined based on the high temperature interval division result, and the maximum input voltage in the high temperature interval where T is located is used as U 恒 .

[0016] Furthermore, the voltage balancing module includes a voltage adjustment unit, a conversion circuit and a protection circuit; the voltage adjustment unit is used to achieve voltage balancing between the cells by adjusting the charge transfer between the cells according to the instruction of the control module;

[0017] A conversion circuit, used for switching between a constant current charging mode and a constant voltage charging mode;

[0018] Protection circuit for monitoring the voltage, current and temperature of the battery cell.

[0019] Furthermore, the voltage adjustment unit includes at least one bidirectional DC / DC converter, a plurality of energy storage elements and a plurality of switching devices; the bidirectional DC / DC converter is used to realize the power transfer and voltage adjustment between the battery cells; the switching device is used to control the energy transfer between the battery cells according to the instructions of the control module; the energy storage element is used to temporarily store and release energy.

[0020] Furthermore, the energy storage element is an inductor.

[0021] Furthermore, the control module adjusts the preset constant voltage threshold value U 恒 When the linear interpolation method is used, the corresponding U is determined according to the position of the overall temperature T of the battery module within the preset temperature range. 恒 .

[0022] Furthermore, the division of the low temperature interval and the high temperature interval is based on the thermal characteristics of the battery module, the battery cell material and the use environment, and the maximum input voltage of each interval is determined by a simulation method.

[0023] Furthermore, the battery cells in the battery module are lithium-ion batteries, nickel-metal hydride batteries or other types of rechargeable batteries.

[0024] Furthermore, a method for controlling voltage balancing of energy storage cells comprises the following steps:

[0025] Real-time monitoring of the voltage, current and temperature data of each battery cell;

[0026] Determine the preset pressure equalization target and constant pressure threshold value U 恒 , constant voltage threshold value U 恒 Adjustment based on the overall temperature T of the battery module;

[0027] Calculate the voltage value that needs to be adjusted based on the preset voltage equalization target and the current battery cell status;

[0028] Calculate the optimal charging strategy based on the constant voltage output model in the auxiliary module and the real-time collected battery cell data;

[0029] If the maximum voltage value of the battery cell is U mul Less than the constant voltage threshold U 恒 , the constant current charging mode is adopted; if the maximum voltage value of the battery cell is U mul Greater than or equal to the constant voltage threshold value U 恒 , the constant voltage charging mode is adopted, and the charging parameters are adjusted according to the constant voltage output model until the cell voltage approaches the target value;

[0030] Repeat the above steps until the voltage of all cells reaches the preset voltage equalization target.

[0031] Further, a battery management system includes the energy storage cell voltage equalization control circuit, communication module and fault diagnosis and alarm module as described above;

[0032] The communication module is used for BMS to communicate with external systems;

[0033] The fault diagnosis and alarm module is used to monitor the operating status of the battery module and the BMS itself.

[0034] The above scheme has the following beneficial effects:

[0035] 1. This solution can significantly reduce the backflow phenomenon of the battery pack during the balancing process by accurately controlling the charging current and voltage; the backflow phenomenon refers to the unnecessary transfer and loss of electricity between cells during the battery balancing process. By optimizing the control strategy, this solution reduces this unnecessary energy loss, thereby improving the energy utilization efficiency of the entire battery pack. This is of great significance for improving the range of electric vehicles and reducing the cost of use.

[0036] 2. In this solution, with the help of the constant voltage output model in the auxiliary module and the real-time collected battery cell data, the control module can calculate the optimal charging strategy. This strategy enables each battery cell in the battery pack to quickly reach the preset voltage equalization target, thereby achieving efficient equalization. Compared with traditional equalization methods, this solution has faster equalization speed and higher equalization accuracy, which helps to extend the service life of the battery pack and improve the overall performance.

[0037] 3. Constant voltage threshold value U in this scheme 恒 It can be dynamically adjusted according to the overall temperature of the battery module. This design enables the solution to adapt to changes in battery characteristics under different ambient temperatures, ensuring the best balancing effect under various conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The system block diagram of the energy storage cell voltage equalization control circuit, control method and battery management system embodiment of the present invention.

[0039] Figure 2 The present invention is a circuit diagram of an energy storage cell voltage equalization control circuit, a control method and a battery management system embodiment. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be described clearly and completely in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The following is further described in detail through specific implementation methods:

[0042] The embodiment is basically as shown in the attached Figure 1 As shown: The energy storage cell voltage equalization control circuit mainly includes a battery module, a collection module, a control module, a voltage equalization module and an auxiliary module.

[0043] Specifically, the battery module is composed of a number of battery cells connected in series as an energy storage system.

[0044] The acquisition module is responsible for real-time monitoring of key parameters such as voltage, current and temperature of each battery cell.

[0045] The control module is used to calculate the voltage value that needs to be adjusted based on the data of the acquisition module, according to the preset voltage balancing target and the current battery cell state, and send instructions to the voltage balancing module for execution. Preferably, the control module sets a reasonable voltage balancing target based on the overall performance of the energy storage system and the characteristics of the battery cell. This includes the voltage deviation range between the battery cells, the fluctuation range of the overall voltage, etc. Based on the current battery cell state and the voltage balancing target, calculate the voltage value that needs to be adjusted for each battery cell. Generate specific voltage balancing control instructions based on the calculated voltage adjustment amount and the optimized adjustment strategy. These instructions usually include the number of the battery cell, the voltage value that needs to be adjusted, the direction of adjustment (charging or discharging), etc.

[0046] The voltage balancing module is used to adjust the voltage of the cells in the battery module according to the instructions of the control module. Specifically, the voltage balancing module includes a voltage adjustment unit, a conversion circuit and a protection circuit. The voltage adjustment unit is the core part of the voltage balancing module, which realizes the power transfer and voltage adjustment between the cells through a bidirectional DC / DC converter. The bidirectional DC / DC converter is a power electronic device that can transmit electric energy in both directions. It can flexibly adjust the voltage and current between the cells according to the instructions of the control module, thereby realizing the balance of power between the cells. Specifically, the voltage adjustment unit includes at least one bidirectional DC / DC converter, a plurality of energy storage elements and a plurality of switching devices; the bidirectional DC / DC converter is used to realize the power transfer and voltage adjustment between the cells; the switching device is used to control the energy transfer between the cells according to the instructions of the control module; the energy storage element is used to temporarily store and release energy. Specifically, the bidirectional DC / DC converter is composed of two full bridges H1 and H2, a high-frequency transformer, an input side DC capacitor C1 and an output side DC capacitor C2, and an energy storage inductor L.

[0047] Specifically, when the voltage of a cell is higher than that of other cells, the bidirectional DC / DC converter will transfer its excess power to other cells with lower voltage, and vice versa. This power transfer process is achieved by controlling the on and off of the switching devices to accurately adjust the voltage difference between the cells. The conversion circuit plays the role of switching between constant current charging mode and constant voltage charging mode in the voltage equalization module.

[0048] In constant current charging mode, the conversion circuit controls the size of the charging current to keep it at a constant level. This charging method is suitable for situations where the battery voltage is low or the battery power is seriously insufficient, and can quickly replenish the battery power.

[0049] In constant voltage charging mode, the conversion circuit controls the charging voltage to keep it at a constant level. This charging method is suitable for situations where the battery cell voltage is close to full charge or the battery is already sufficiently charged, which can avoid the risk of overcharging and battery damage.

[0050] The protection circuit is responsible for monitoring key parameters of the battery cell, such as voltage, current and temperature, to ensure that the battery cell operates within a safe range.

[0051] Specifically, the protection circuit will monitor the voltage and current of the battery in real time. When the voltage or current is abnormal, it will immediately cut off the charging or discharging circuit to prevent damage to the battery or safety accidents. At the same time, the protection circuit will also monitor the temperature of the battery. When the temperature is too high, it will take cooling measures or stop the charging / discharging operation to ensure the normal operation of the battery.

[0052] The auxiliary module is used to set the constant voltage threshold value U 恒 And the maximum voltage value U of the collected battery mul Determine the charging mode of the voltage balancing module. Preferably, the preset constant voltage threshold value U 恒 Determine based on the following steps: Obtain the overall temperature T of the battery module to determine the input voltage threshold value U of the high-voltage battery cell to the low-voltage battery cell 恒 , if T1≤T≤T2, then set U 恒 =U T1 , T1 is the low temperature threshold value, T2 is the high temperature threshold value, U T1 is the maximum input voltage at normal temperature. This value is usually obtained through experiments or simulations to ensure that the battery module can work safely and efficiently under normal temperature conditions. If T<T1, the low temperature interval where T is located is determined based on the low temperature interval division result, and the maximum input voltage in the low temperature interval where T is located is used as U 恒Specifically, the low temperature interval is divided into X, and each low temperature interval sets the maximum input voltage of the two endpoint temperatures in the current interval. If T is in the Xth interval, the maximum input voltage of the two endpoints in the interval is U l1 and U l2 , according to the current temperature T between the two endpoint temperatures, use the interpolation formula to calculate the corresponding U l , that is U 恒 Equal to U l , for the high temperature interval, the same applies. If T>T2, the high temperature interval where T is located is determined based on the high temperature interval division result, and the maximum input voltage in the high temperature interval where T is located is used as U 恒 .

[0053] If U mul Less than U 恒 , then the voltage balancing module is controlled to adopt constant current charging; if U mul Greater than or equal to U 恒 , the voltage balancing module is controlled to adopt constant voltage charging, and the charging parameters (input voltage) of the voltage balancing module are adjusted based on the constant voltage output model; preferably, the instantaneous value of the output voltage after a switching cycle is predicted based on the current instantaneous value of the output voltage, and the control module will send instructions to the voltage balancing module based on the prediction result, and adjust the charge transfer between the cells through the voltage adjustment unit (such as a bidirectional DC / DC converter, energy storage element and switching device), thereby achieving voltage balance between the cells. Specifically, the equation of the constant voltage output model is:

[0054]

[0055] Where, η1 and η2 are the inner phase shift duty cycle and the outer phase shift duty cycle respectively, U′ (t) is the instantaneous value of the output voltage sampled at time t, U′ (t+1) is the predicted instantaneous value of the output voltage after one switching cycle, i′ (t) is the instantaneous value of the output current sampled at time t, C2 is the output side capacitor, f s is the switching frequency, L is the inductance, u i(t) is the instantaneous value of the input voltage at time t. The operation of the constant voltage output model in the energy storage cell voltage equalization control circuit is a closed-loop control system. It realizes the voltage balance between cells and the precise control of the charging process by real-time monitoring of the cell status, calculation of the predicted voltage value, sending adjustment instructions, and real-time monitoring and protection.

[0056] The entire voltage equalization process is a cyclic process. After each voltage equalization operation is completed, the acquisition module will re-collect the data of the battery cell and compare it with the voltage equalization target preset by the control module. If there is still a difference, the control module will generate a voltage equalization control instruction again and send it to the voltage equalization module for execution. This process will continue until the voltage of all batteries reaches the preset voltage equalization target.

[0057] This embodiment also provides a method for controlling voltage balancing of energy storage cells, comprising the following steps:

[0058] Real-time monitoring of the voltage, current and temperature data of each battery cell.

[0059] Determine the preset pressure equalization target and constant pressure threshold value U 恒 , constant voltage threshold value U 恒 Adjust based on the overall temperature T of the battery module. According to the design requirements and actual application scenarios of the battery module, a reasonable voltage target value is preset, which represents the ideal state that all battery cell voltages should reach. According to the overall temperature T of the battery module, the constant voltage threshold value U is dynamically adjusted. 恒 .

[0060] Calculate the voltage value that needs to be adjusted based on the preset voltage equalization target and the current cell status. Compare the real-time voltage value of each cell with the preset voltage equalization target value to calculate the voltage deviation. Determine the direction of adjustment based on the positive or negative voltage deviation. If the voltage deviation is positive, the voltage needs to be lowered; if the voltage deviation is negative, the voltage needs to be increased.

[0061] The optimal charging strategy is calculated based on the constant voltage output model in the auxiliary module and the real-time collected battery cell data. The real-time collected battery cell data (voltage, current, temperature) and the preset voltage equalization target and constant voltage threshold are input into the constant voltage output model in the auxiliary module. The constant voltage output model calculates the optimal charging strategy based on the input data and the preset algorithm, including parameters such as charging current, charging voltage and charging time (for low-voltage batteries).

[0062] If the maximum voltage value of the battery cell is U mul Less than the constant voltage threshold U 恒 , the constant current charging mode is adopted; if the maximum voltage value of the battery cell is U mul Greater than or equal to the constant voltage threshold value U 恒 , the constant voltage charging mode is adopted, and the charging parameters are adjusted according to the constant voltage output model until the cell voltage approaches the target value.

[0063] Repeat the above steps until the voltage of all cells reaches the preset voltage equalization target. When the voltage values ​​of all cells are within the preset voltage equalization target range, it is considered that the voltage equalization state has been reached and the charging process (i.e., voltage equalization process) is stopped.

[0064] This embodiment also provides a battery management system, including the energy storage cell voltage equalization control circuit, the communication module and the fault diagnosis and alarm module as described above.

[0065] The communication module is used for BMS to communicate with external systems; specifically, the communication module transmits battery status information (such as cell voltage, current, temperature, SOC, etc.) to the external system in real time. It receives control instructions from the external system, such as charging instructions, discharging instructions, etc., and transmits them to the energy storage cell voltage equalization control circuit for execution.

[0066] The fault diagnosis and alarm module is used to monitor the operating status of the battery module and the BMS itself. Specifically, the fault diagnosis and alarm module monitors the operating status of the battery module and the BMS itself in real time. Once a fault or abnormal situation (such as overvoltage, overcurrent, overtemperature, etc.) is found, the fault diagnosis is immediately performed and an alarm signal is issued. According to the type and severity of the fault, appropriate protection measures are taken, such as cutting off the circuit, reducing the charging power, etc., to ensure the safe operation of the system.

[0067] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and / or characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. Energy storage cell voltage equalization control circuit, characterized by: It includes a battery module, a collection module, a control module, a pressure equalization module and an auxiliary module; The battery module includes a number of battery cells connected in series; The acquisition module is used to monitor the data of each battery cell; The control module is used to calculate the voltage value that needs to be adjusted based on the data of the acquisition module, according to the preset voltage balancing target and the current battery cell status, and send instructions to the voltage balancing module for execution; The voltage balancing module is used to adjust the voltage of the cells in the battery module according to the instructions of the control module; The auxiliary module is used to set the constant voltage threshold value U 恒 And the maximum voltage value U of the collected battery max Determine the charging method of the voltage balancing module; if U max Less than U 恒 , then the voltage balancing module is controlled to adopt constant current charging; if U max Greater than or equal to U 恒 , the voltage balancing module is controlled to adopt constant voltage charging, and the charging current is adjusted based on the constant voltage output model; the equation of the constant voltage output model is: Where, η1 and η2 are the inner phase shift duty cycle and the outer phase shift duty cycle respectively, U′ (t) is the instantaneous value of the output voltage sampled at time t, U′ (t+1) is the predicted instantaneous value of the output voltage after one switching cycle, i′ (t) is the instantaneous value of the output current sampled at time t, C2 is the output side capacitor, f s is the switching frequency, L is the inductance, u i(t) is the instantaneous value of the input voltage at time t.

2. The energy storage cell voltage equalization control circuit according to claim 1, characterized in that: The preset constant voltage threshold U 恒 is determined based on the following steps: Obtain the overall temperature T of the battery module and determine the input voltage threshold U from the high-voltage battery cells to the low-voltage battery cells 恒 , if T1 ≤ T ≤ T2, then set U 恒 = U T1 , where T1 is the low-temperature threshold, T2 is the high-temperature threshold, and U T1 is the maximum input voltage at the set normal temperature; if T < T1, then determine the low-temperature interval where T is located based on the low-temperature interval division result, and use the maximum input voltage in the low-temperature interval where T is located as U 恒 ; if T > T2, then determine the high-temperature interval where T is located based on the high-temperature interval division result, and use the maximum input voltage in the high-temperature interval where T is located as U 恒 .

3. The energy storage cell voltage equalization control circuit according to claim 2, characterized in that: The voltage balancing module includes a voltage adjustment unit, a conversion circuit and a protection circuit; the voltage adjustment unit is used to achieve voltage balancing between the cells by adjusting the charge transfer between the cells according to the instructions of the control module; A conversion circuit, used for switching between a constant current charging mode and a constant voltage charging mode; Protection circuit for monitoring the voltage, current and temperature of the battery cell.

4. The energy storage cell voltage equalization control circuit according to claim 3, characterized in that: The voltage adjustment unit includes at least one bidirectional DC / DC converter, a plurality of energy storage elements and a plurality of switching devices; the bidirectional DC / DC converter is used to realize the power transfer and voltage adjustment between the battery cells; the switching device is used to control the energy transfer between the battery cells according to the instructions of the control module; the energy storage element is used to temporarily store and release energy.

5. The energy storage cell voltage equalization control circuit according to claim 4, characterized in that: The energy storage element is an inductor.

6. The energy storage cell voltage equalization control circuit according to claim 5, characterized in that: The control module adjusts the preset constant voltage threshold value U 恒 When the linear interpolation method is used, the corresponding U is determined according to the position of the overall temperature T of the battery module within the preset temperature range. 恒 .

7. The energy storage cell voltage equalization control circuit according to claim 6, characterized in that: The division of the low temperature interval and the high temperature interval is based on the thermal characteristics of the battery module, the battery cell material and the use environment, and the maximum input voltage of each interval is determined by a simulation method.

8. The energy storage cell voltage equalization control circuit according to claim 7, characterized in that: The battery cells in the battery module are lithium-ion batteries, nickel-metal hydride batteries or other types of rechargeable batteries.

9. A method for controlling the voltage balancing of an energy storage cell, based on the voltage balancing control circuit of the energy storage cell according to claims 1-8, characterized in that: The following steps are involved: Real-time monitoring of the voltage, current and temperature data of each battery cell; Determine the preset pressure equalization target and constant pressure threshold value U 恒 , constant voltage threshold value U 恒 Adjustment based on the overall temperature T of the battery module; Calculate the voltage value that needs to be adjusted based on the preset voltage equalization target and the current battery cell status; Calculate the optimal charging strategy based on the constant voltage output model in the auxiliary module and the real-time collected battery cell data; If the maximum voltage value of the battery cell is U max Less than the constant voltage threshold U 恒 , the constant current charging mode is adopted; if the maximum voltage value of the battery cell is U max Greater than or equal to the constant voltage threshold value U 恒 , the constant voltage charging mode is adopted, and the charging parameters are adjusted according to the constant voltage output model until the cell voltage approaches the target value; Repeat the above steps until the voltage of all cells reaches the preset voltage equalization target.

10. A battery management system, based on the energy storage cell voltage equalization control circuit according to claims 1-8, characterized in that: It includes energy storage cell voltage equalization control circuit, communication module and fault diagnosis and alarm module; The communication module is used for BMS to communicate with external systems; The fault diagnosis and alarm module is used to monitor the operating status of the battery module and the BMS itself.

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