Active equalization control method and device of battery pack for energy storage

Abstract

The invention provides an active equalization control method and device for an energy storage battery pack, and relates to the technical field of electric power grids. By monitoring the charge and discharge state of the battery pack and the real-time voltage of each battery, calculating the average voltage and the mean value difference, and combining with the preset mean value difference threshold value, active equalization control is performed on the battery pack, so that the voltage difference between the batteries is smaller than the mean value difference threshold value when charging or discharging is completed; the influence on the whole battery pack due to early end of charging and discharging of a certain battery is avoided, the charging and discharging interval of the battery pack is expanded, and the available capacity of the battery pack is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power grids, and in particular to an active balancing control method and device for an energy storage battery pack. Background Art

[0002] With the development of science and technology, battery packs consisting of multiple cells connected in parallel or series are becoming more and more widely used, improving the voltage and capacity of battery packs to meet the usage requirements of various scenarios, such as in energy storage power stations and electric vehicles.

[0003] However, due to differences in battery cell materials and manufacturing processes, there are certain differences in the chemical and electrical properties of single batteries. The differences in the battery usage environment in actual working conditions will cause each battery to decay at different rates. The inconsistency of single battery voltage, capacity, internal resistance and self-discharge rate causes the battery pack to have a "short board effect" and affect the overall performance.

[0004] For example, during the charging process, because one battery is fully charged while other batteries are not, the charging process of the battery pack is interrupted and the capacity of the battery pack is limited; for another example, during the discharging process, because one battery discharges faster, the voltage of this battery reaches the threshold first while other batteries still have remaining power, causing the discharging process of the battery pack to be interrupted early. The usable capacity of the battery pack is reduced, affecting the overall performance of the battery pack.

[0005] During frequent charge and discharge cycles, the problem of battery pack inconsistency will be exacerbated, which will seriously affect the performance of the battery pack such as available capacity and service life. Summary of the invention

[0006] The present invention provides an active balancing control method and device for a battery pack for energy storage, which can realize active balancing during the charging and discharging process of the battery pack and increase the available capacity of the battery pack.

[0007] In a first aspect, the present invention provides an active balancing control method for a battery pack for energy storage, the method comprising: monitoring the charge and discharge state of the battery pack and the real-time voltage of each battery in the battery pack; determining whether the battery pack enters an active balancing mode based on the charge and discharge state and the real-time voltage; if the battery pack enters the active balancing mode, calculating the average voltage of multiple batteries in the battery pack; and calculating the mean difference between the real-time voltage and the average voltage of each battery; determining a balancing interval based on the average voltage and a preset mean difference threshold, the balancing interval comprising a charging interval, an intermediate interval and a discharging interval; the mean difference threshold is the maximum difference between the battery voltage and the average voltage when charging or discharging is completed; based on the real-time voltage, mean difference and balancing interval of each battery, actively balancing each battery to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack.

[0008] In one possible implementation, whether the battery pack enters the active balancing mode is determined based on the charge and discharge status and the real-time voltage of each battery, including: if the battery pack is in a charging state, and the real-time voltage of at least one battery in the battery pack is greater than the charge start threshold, then it is determined that the battery pack enters the active balancing mode; if the battery pack is in a charging state, and the real-time voltage of each battery in the battery pack is less than or equal to the charge start threshold, then it is determined that the battery pack is in a normal charging mode; if the battery pack is in a discharging state, and the real-time voltage of at least one battery in the battery pack is less than the discharge start threshold, then it is determined that the battery pack enters the active balancing mode; if the battery pack is in a discharging state, and the real-time voltage of each battery in the battery pack is greater than or equal to the discharge start threshold, then it is determined that the battery pack is in a normal discharge mode.

[0009] In one possible implementation, the balancing interval is determined based on the average voltage and a preset mean difference threshold, including: determining the middle interval with the average voltage as the center of the middle interval and the mean difference threshold as the range of the middle interval; determining the range in which the real-time voltage is greater than the upper limit of the middle interval as the discharging interval; and determining the range in which the real-time voltage is less than the lower limit of the middle interval as the charging interval.

[0010] In a possible implementation, active balancing control is performed on each battery based on the real-time voltage, mean difference and balancing interval of each battery to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack, including: if the battery pack is in a charging state, the real-time voltage of the target battery is greater than the charging start threshold, and the mean difference of the target battery is in the middle interval or the charging interval, then the target battery is kept in a charging state unchanged; the target battery is any battery in the battery pack; if the battery pack is in a charging state, the real-time voltage of the target battery is greater than the charging start threshold, and the mean difference of the target battery is in the discharging interval, then the target battery is controlled to enter a discharging state;

[0011] In one possible implementation, active balancing control is performed on each battery based on the real-time voltage, mean difference and balancing interval of each battery to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack, and also includes: if the battery pack is in a discharging state, the real-time voltage of the target battery is less than the discharge start threshold, and the mean difference of the target battery is in the middle interval or the discharging interval, then the target battery is kept in the discharging state unchanged; if the battery pack is in a discharging state, the real-time voltage of the target battery is less than the discharge start threshold, and the mean difference of the target battery is in the charging interval, then the target battery is controlled to enter the charging state.

[0012] In a possible implementation, the method further includes: monitoring the number of charge and discharge times of the battery pack; if the number of charge and discharge times is greater than or equal to a set number, starting a threshold update process to update a charge start threshold and a discharge start threshold.

[0013] In one possible implementation, a threshold update process is started to update a charge start threshold and a discharge start threshold, including: obtaining charge and discharge data of each battery in a battery pack, the charge and discharge data including the battery voltage at each moment in a charge process or a discharge process; calculating the battery voltage slope of each battery at each moment in a charge process or a discharge process based on the charge and discharge data of each battery; determining the terminal voltage of each battery based on the battery voltage slope and a preset slope threshold, the terminal voltage including a charge terminal voltage and a discharge terminal voltage; calculating an average value of the charge terminal voltage based on the charge terminal voltage of each battery in the battery pack; updating the charge start threshold based on the average value of the charge terminal voltage; calculating an average value of the discharge terminal voltage based on the discharge terminal voltage of each battery in the battery pack; and updating the discharge start threshold based on the average value of the discharge terminal voltage.

[0014] In one possible implementation, the method also includes: if the battery pack is in a charging state, then based on the real-time voltage of each battery and the balancing interval, the category of each battery pack is determined, and the categories include charging group, discharging group and intermediate group; if each battery in the battery pack is an intermediate group, then it is determined that active balancing of the battery pack is completed, the battery pack is controlled to exit the active balancing mode, and charging is completed; if the battery pack is in a discharging state, then based on the real-time voltage of each battery and the balancing interval, the category of each battery group is determined, and the categories include charging group, discharging group and intermediate group; if each battery in the battery pack is an intermediate group, then it is determined that active balancing of the battery pack is completed, the battery pack is controlled to exit the active balancing mode, and discharging is completed.

[0015] In a possible implementation, the method is applied to a balancing control circuit, the balancing control circuit includes a flyback transformer corresponding to each battery; the primary side of the flyback transformer is connected to the battery through a primary switch, and the secondary side of the flyback transformer is connected to the balancing bus through a secondary switch; controlling the target battery to enter a discharge state, including: step 11, controlling the primary switch to close and the secondary switch to open; step 12, monitoring the real-time current of the primary side of the flyback transformer; step 13, if the real-time current of the primary side of the flyback transformer reaches a preset peak current, then controlling the primary switch to open and the secondary switch to close; step 14, monitoring the real-time current of the secondary side of the flyback transformer; step 15, if the real-time current of the secondary side of the flyback transformer decreases, then controlling the primary switch to close and the secondary switch to close; step 16, monitoring the real-time current of the secondary side of the flyback transformer; step 17, if the real-time current of the secondary side of the flyback transformer decreases, then controlling the primary switch to close and the secondary switch to close; step 18, monitoring the real-time current of the secondary side of the flyback transformer; step 19, controlling the real-time current of the secondary side of the flyback transformer to close. If the real-time current of the secondary side of the flyback transformer decreases to zero, the secondary side switch is controlled to be disconnected and the primary side switch is controlled to be closed; step 16, repeating steps 11 to 16 to realize the target battery discharge; controlling the target battery to enter the charging state, including: step 21, controlling the secondary side switch to be closed and the primary side switch to be disconnected; step 22, monitoring the real-time current of the secondary side of the flyback transformer; step 23, if the real-time current of the secondary side of the flyback transformer reaches a preset peak current, the secondary side switch is controlled to be disconnected and the primary side switch is closed; step 24, monitoring the real-time current of the primary side of the flyback transformer; step 25, if the real-time current of the primary side of the flyback transformer decreases to zero, the primary side switch is controlled to be disconnected and the secondary side switch is closed; step 26, repeating steps 21 to 26 to realize the target battery charging.

[0016] In a second aspect, an embodiment of the present invention provides an active balancing control device for a battery pack for energy storage, the control device comprising: a communication module for monitoring the charge and discharge state of the battery pack and the real-time voltage of each battery in the battery pack; a processing module for determining whether the battery pack enters an active balancing mode based on the charge and discharge state and the real-time voltage; if the battery pack enters the active balancing mode, the average voltage of multiple batteries in the battery pack is calculated; and the mean difference between the real-time voltage and the average voltage of each battery is calculated; based on the average voltage and a preset mean difference threshold, a balancing interval is determined, the balancing interval comprising a charging interval, an intermediate interval and a discharging interval; the mean difference threshold is the maximum difference between the battery voltage and the average voltage when charging or discharging is completed; based on the real-time voltage, mean difference and balancing interval of each battery, active balancing control is performed on each battery to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack.

[0017] In a third aspect, an embodiment of the present invention provides an electronic device, comprising a memory and a processor, the memory storing a computer program, the processor being used to call and run the computer program stored in the memory to perform the steps of the method described in the first aspect and any possible implementation method of the first aspect.

[0018] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and wherein when the computer program is executed by a processor, the steps of the method described in the first aspect and any possible implementation method of the first aspect are implemented.

[0019] The present invention provides an active balancing control method and device for a battery pack for energy storage. The present invention monitors the charging and discharging state of the battery pack and the real-time voltage of each battery, calculates the average voltage and the mean difference, and combines a preset mean difference threshold to perform active balancing control on the battery pack, so that when charging or discharging is completed, the voltage difference between the batteries is less than the mean difference threshold, thereby avoiding the influence of the early termination of charging and discharging of a certain battery on the entire battery pack, expanding the charging and discharging range of the battery pack, and increasing the available capacity of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 is a structural schematic diagram of a balancing control circuit provided by an embodiment of the present invention;

[0022] Figure 2 is a structural schematic diagram of a flyback transformer provided by an embodiment of the present invention;

[0023] Figure 3 It is a flow chart of an active balancing control method for an energy storage battery pack provided by an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of battery group division provided by an embodiment of the present invention;

[0025] Figure 5 is a schematic diagram of a charge and discharge curve of a battery provided by an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of a typical equalization process under a charging state provided by an embodiment of the present invention;

[0027] Figure 7 It is a schematic diagram of a process of active balancing provided by an embodiment of the present invention;

[0028] Figure 8 It is a structural schematic diagram of an active balancing control device for an energy storage battery pack provided by an embodiment of the present invention;

[0029] Fig. 9 It is a structural schematic diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0031] In the description of the present invention, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, "at least one" and "plurality" refer to two or more. The words "first", "second", etc. do not limit the quantity and execution order, and the words "first", "second", etc. do not limit them to be different.

[0032] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0033] In addition, the terms "including" and "having" and any variations thereof mentioned in the description of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include other steps or modules that are not listed, or may optionally include other steps or modules that are inherent to these processes, methods, products or devices.

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following will be described through specific embodiments in conjunction with the accompanying drawings of the present invention.

[0035] Battery balancing technology is to find a way to make batteries with different capacities equal. There are two common balancing methods: energy dissipation type unidirectional balancing (passive balancing) and energy transfer type bidirectional balancing (active balancing).

[0036] Passive balancing: The principle of passive balancing is to connect a switchable discharge resistor in parallel to each string of batteries. The BMS controls the discharge resistor to discharge the cells with higher voltage, and the electric energy is dissipated in the form of heat. For example, when battery B is almost full, turn on the switch to let the resistor on battery B release heat, so that the excess electric energy of B is dissipated in the form of heat energy, and then continue to charge until A and C are also full. This method can only discharge cells with high voltage, and cannot supplement the cells with low capacity. Due to the power limit of the discharge resistor, the balancing current is generally small (less than 1A).

[0037] The advantages of passive balancing are low cost and simple circuit design; the disadvantages are that balancing is based on the lowest battery residual capacity, which cannot increase the capacity of batteries with low residual capacity, and 100% of the balanced power is wasted in the form of heat.

[0038] Active balancing: The energy of the high-voltage battery cell is transferred to the low-voltage battery cell through an algorithm with the help of energy storage components between multiple strings of batteries. The higher-voltage battery is discharged, and the released energy is used to charge the lower-voltage single cell. The energy is mainly transferred rather than dissipated. In this way, when charging, let the battery B, which reaches 100% voltage first, self-discharge to A and C, and then the three batteries are fully charged together; the same is true when discharging. When the remaining power of battery B is too low, let A and C "charge" B so that battery B will not reach the SOC threshold for stopping discharge so quickly. There are mainly the following ways of active balancing technology. Based on the inductor balancing structure, the balancing efficiency is high and the scalability is good, but it is generally limited to energy transfer between adjacent single cells. Based on the capacitor balancing structure, the structure is simple, but it is limited to voltage balancing. When the battery voltage difference is large, the balancing time is longer.

[0039] like Figure 1 As shown, an embodiment of the present invention provides a structural schematic diagram of a balancing control circuit. The balancing control circuit includes a battery pack, a flyback transformer, a controllable switch, a balancing bus and a conversion matrix.

[0040] The battery pack is composed of multiple (for example, 12) single cells (B1-B12) connected in series, each single cell is connected in parallel with a transformer (T1-T12), the primary side of the transformer is connected to the single cell through controllable switches S11, S21, ..., S121, and the secondary side of the transformer is connected to the balancing bus through controllable switches S12, S22, ..., S122. Through the switch control and the coupling effect of the transformer, the bidirectional transfer of energy between the single cell and the battery pack can be realized. The conversion matrix is ​​used to select a specific single cell during threshold correction.

[0041] Figure 2 A schematic diagram of the structure of a flyback transformer provided in an embodiment of the present invention. Figure 2T1 is a transformer, the left side is the primary side of the transformer, which is connected to the single battery, and the right side is the secondary side of the transformer, which is connected to the balancing bus, i.e. the battery pack; Ip is the primary current, Is is the secondary current, Np is the number of turns of the primary coil, Ns is the number of turns of the secondary coil, and Np:Ns=1:1; Q 11 and Q 12 For MOS tube, V gp 、V gs It is the MOS tube driving signal of the primary and secondary sides of the transformer. For a given single battery, when discharging, V gp The primary MOS transistor is turned on, and the current Ip ramps up in the primary winding of the transformer until it reaches the preset peak current. The primary MOS transistor is then turned off, and the energy stored in the primary side of the transformer is coupled to the secondary side, causing current to flow in the secondary winding of the transformer. Enable V gs The secondary MOS tube is turned on synchronously to minimize the power loss during the battery discharge phase until the secondary current Is drops to zero.

[0042] Once the secondary current reaches zero, the secondary MOS tube is disconnected and the primary MOS tube is reconnected, thus repeating the above cycle. In this way, the charge is transferred from the single cell in discharge to the entire battery pack, realizing the transfer of energy from the single cell to the battery pack.

[0043] based on Figure 1 The balance control circuit and Figure 2 The flyback transformer, such as Figure 3 As shown, an embodiment of the present invention provides an active balancing control method for an energy storage battery pack. The control method includes steps S101-S105.

[0044] S101 , monitoring the charge and discharge status of a battery pack and the real-time voltage of each battery in the battery pack.

[0045] S102: Determine whether the battery pack enters an active balancing mode based on the charge and discharge status and the real-time voltage.

[0046] As a possible implementation manner, step S102 may be specifically implemented as steps S1021 - S1024 .

[0047] S1021: If the battery pack is in a charging state, and the real-time voltage of at least one battery in the battery pack is greater than the charging start threshold, determine that the battery pack enters an active balancing mode.

[0048] S1022: If the battery pack is in a charging state, and the real-time voltage of each battery in the battery pack is less than or equal to the charging start threshold, it is determined that the battery pack is in a normal charging mode.

[0049] S1023: If the battery pack is in a discharging state, and the real-time voltage of at least one battery in the battery pack is less than the discharge start threshold, determine that the battery pack enters an active balancing mode.

[0050] S1024: If the battery pack is in a discharging state, and the real-time voltage of each battery in the battery pack is greater than or equal to a discharge start threshold, it is determined that the battery pack is in a normal discharging mode.

[0051] S103: If the battery pack enters the active balancing mode, the average voltage of the multiple batteries in the battery pack is calculated; and the mean difference between the real-time voltage of each battery and the average voltage is calculated.

[0052] S104: Determine a balancing interval based on the average voltage and a preset mean difference threshold.

[0053] In some embodiments, the balancing interval includes a charging interval, an intermediate interval, and a discharging interval; the mean difference threshold is the maximum difference between the battery voltage and the average voltage when charging is completed or discharging is completed.

[0054] As a possible implementation manner, step S104 may be specifically implemented as steps S1041 - S1043 .

[0055] S1041 . Determine the middle interval by taking the average voltage as the center of the middle interval and the mean difference threshold as the range of the middle interval.

[0056] S1042: Determine a range in which the real-time voltage is greater than an upper limit of the middle interval as a discharge interval.

[0057] S1043: Determine a range in which the real-time voltage is less than a lower limit of the middle interval as a charging interval.

[0058] It should be noted that the mean difference threshold is a preset threshold. The present invention uses the single cell voltage as the control target parameter, performs active balancing control based on the voltage of each cell, and finally controls the voltage difference between the cells in the group to the end threshold, that is, the mean difference threshold V delta within the range.

[0059] In order to improve the balancing efficiency, the N to N mode is adopted. In each sampling period, the average voltage V is calculated according to the voltage of each battery cell. avg , combined with the end threshold V delta , all cells are divided into three groups: batteries in the charging range, i.e. charging group (cell voltage is less than V avg -1 / 2V delta ), the battery in the middle range, that is, the middle group (cell voltage is greater than or equal to V avg -1 / 2V delta And less than or equal to V avg +1 / 2V delta), the battery in the discharge range, that is, the discharge group (cell voltage is greater than V avg +1 / 2V delta ).

[0060] For example, at a certain moment, the voltage at terminals B1 to B8 is Figure 4 As shown, according to the above rules: B4 and B8 are the discharge group, B3 and B5 are the charge group, and the rest are the intermediate group.

[0061] S105 , based on the real-time voltage, mean difference and balancing interval of each battery, actively balance each battery to achieve power balance of multiple batteries during the charging and discharging process of the battery pack.

[0062] As a possible implementation manner, step S105 may be specifically implemented as steps S1051 - S1054 .

[0063] S1051. If the battery pack is in a charging state, the real-time voltage of the target battery is greater than the charging start threshold, and the mean difference of the target battery is in the middle interval or the charging interval, the target battery is kept in a charging state.

[0064] The target battery is any battery in the battery pack.

[0065] S1052: If the battery pack is in a charging state, the real-time voltage of the target battery is greater than the charging start threshold, and the mean difference of the target battery is in a discharging interval, then the target battery is controlled to enter a discharging state.

[0066] S1053: If the battery pack is in a discharging state, the real-time voltage of the target battery is less than the discharge start threshold, and the mean difference of the target battery is in the middle interval or the discharging interval, the target battery is kept in a discharging state.

[0067] S1054: If the battery pack is in a discharging state, the real-time voltage of the target battery is less than the discharge start threshold, and the mean difference of the target battery is in a charging interval, the target battery is controlled to enter a charging state.

[0068] In some embodiments, the balancing control circuit includes a flyback transformer corresponding to each battery; the primary side of the flyback transformer is connected to the battery through a primary side switch, and the secondary side of the flyback transformer is connected to the balancing bus through a secondary side switch.

[0069] Accordingly, the embodiment of the present invention can control the target battery to enter a discharging state through steps 11 to 16.

[0070] Step 11, control the primary switch to be closed and the secondary switch to be opened.

[0071] Step 12, monitoring the real-time current of the primary side of the flyback transformer.

[0072] Step 13: If the real-time current of the primary side of the flyback transformer reaches a preset peak current, the primary side switch is controlled to be disconnected and the secondary side switch is controlled to be closed.

[0073] Step 14, monitoring the real-time current of the secondary side of the flyback transformer.

[0074] Step 15: If the real-time current of the secondary side of the flyback transformer decreases to zero, the secondary side switch is controlled to be opened and the primary side switch is controlled to be closed.

[0075] Step 16, repeating steps 11 to 16 to achieve target battery discharge.

[0076] Accordingly, the embodiment of the present invention can control the target battery to enter a charging state through steps 21 to 26.

[0077] Step 21, control the secondary switch to be closed and the primary switch to be opened.

[0078] Step 22, monitoring the real-time current of the secondary side of the flyback transformer.

[0079] Step 23: If the real-time current of the secondary side of the flyback transformer reaches the preset peak current, the secondary side switch is controlled to be opened and the primary side switch is controlled to be closed.

[0080] Step 24, monitoring the real-time current of the primary side of the flyback transformer.

[0081] Step 25: If the real-time current of the primary side of the flyback transformer decreases to zero, the primary side switch is controlled to be opened and the secondary side switch is controlled to be closed.

[0082] Step 26, repeating steps 21 to 26 to achieve target battery charging.

[0083] The present invention provides an active balancing control method for a battery pack for energy storage. The method monitors the charging and discharging state of the battery pack and the real-time voltage of each battery, calculates the average voltage and the mean difference, and performs active balancing control on the battery pack in combination with a preset mean difference threshold, so that when charging or discharging is completed, the voltage difference between the batteries is less than the mean difference threshold, thereby avoiding the influence of the early termination of charging and discharging of a certain battery on the entire battery pack, expanding the charging and discharging range of the battery pack, and increasing the available capacity of the battery pack.

[0084] Optionally, the active balancing control method for an energy storage battery pack provided in an embodiment of the present invention further includes steps S201 - S202 .

[0085] S201, monitoring the charge and discharge times of the battery pack.

[0086] S202: If the number of charge and discharge times is greater than or equal to the set number of times, the threshold update process is started to update the charge start threshold and the discharge start threshold.

[0087] Exemplarily, the embodiment of the present invention may update the charge start threshold and the discharge start threshold through steps S2021-S2027.

[0088] S2021. Obtain charging and discharging data of each battery in the battery pack.

[0089] In some embodiments, the charge and discharge data includes the battery voltage at each moment in the charging process or the discharging process.

[0090] S2022. Calculate the battery voltage slope of each battery at each moment during the charging process or the discharging process based on the charging and discharging data of each battery.

[0091] S2023. Determine the terminal voltage of each battery based on the battery voltage slope and a preset slope threshold.

[0092] In some embodiments, the terminal voltage includes a charging terminal voltage and a discharging terminal voltage.

[0093] S2024. Calculate an average value of the charging terminal voltage based on the charging terminal voltage of each battery in the battery pack.

[0094] S2025: Update the charging start threshold based on the average value of the charging terminal voltage.

[0095] S2026. Calculate an average value of the discharge terminal voltage based on the discharge terminal voltage of each battery in the battery pack.

[0096] S2027: Update the discharge start threshold based on the average value of the discharge terminal voltage.

[0097] like Figure 5 As shown, an embodiment of the present invention provides a schematic diagram of a battery charge and discharge curve. Since the energy transfer efficiency of any balancing process cannot reach 100%, before the battery pack reaches "almost full" / "almost fully discharged", premature balancing will affect the charge and discharge efficiency, causing energy waste, and will also increase the overall charge / discharge time. In addition, due to the existence of a charge / discharge voltage platform, the voltage does not change much during the platform period and cannot be used as an effective input parameter for a voltage-based balancing solution, so a charge start threshold V is defined. chg , discharge start threshold V dischg parameter.

[0098] Due to different types of lithium batteries, the voltage range is also different (ternary lithium voltage range is 2.8~4.2V, lithium iron phosphate voltage range is 2.5~3.65V), and the discharge platform will also change in the later stage of the life cycle. In order to adapt to various specifications of batteries and different usage scenarios, referring to the characteristics of typical battery discharge curves, a self-learning algorithm is used to find the two endpoint voltages V of all battery platform voltages. ph , Vpl (Where V ph is the platform high voltage, V pl is the platform low voltage), calculate the average value of all terminal voltages V phavg , V plavg , and then reduce the voltage range by 3% to get V chg =0.97V phavg ,V dischg =1.03V plavg This self-learning process is performed multiple times throughout the life cycle of the battery pack to complete accurate threshold correction.

[0099] In this way, the embodiment of the present invention can continuously update the charging start threshold and the discharging start threshold, ensure that the active balancing cut-in time is in the optimal period, reduce energy waste, and improve the energy utilization rate of the energy storage battery.

[0100] Optionally, the active balancing control method for an energy storage battery pack provided in an embodiment of the present invention further includes steps S301 - S302 .

[0101] S301: If the battery pack is in a charging state, determine the category of each battery pack based on the real-time voltage of each battery and the balancing interval.

[0102] In some embodiments, the categories include a charging group, a discharging group, and an intermediate group.

[0103] S302: If each battery in the battery pack is an intermediate group, it is determined that active balancing of the battery pack is completed, and the battery pack is controlled to exit the active balancing mode, and charging is completed.

[0104] S303: If the battery pack is in a discharging state, determine the category of each battery pack based on the real-time voltage of each battery and the balancing interval.

[0105] In some embodiments, the categories include a charging group, a discharging group, and an intermediate group;

[0106] S304: If each battery in the battery pack is an intermediate group, it is determined that active balancing of the battery pack is completed, and the battery pack is controlled to exit the active balancing mode, and the discharge is completed.

[0107] In this way, the embodiment of the present invention can monitor the charging and discharging process of each battery until active balancing is completed, and limit the voltage difference between the batteries to within the mean difference threshold range until balancing is completed.

[0108] For example, Figure 6 As shown, taking the charging process as an example, the typical balancing process provided by the embodiment of the present invention, the present invention performs sampling at time t0 to t9, cell avgis a virtual mean cell unit, cello is other cells below the mean, at each sampling moment, the target cell is selected for balancing according to the above strategy: at t1, cell1 is greater than the start threshold V chg , and the difference from the mean is greater than 1 / 2V delta , discharge cell1; from t2 to t3, the voltage rise rate of cell1 slows down, but the voltage is still greater than the start threshold V chg , and the difference from the mean is greater than 1 / 2V delta , so cell1 discharges; at t4, cell2 meets the conditions, cell2 discharges, and cell1 recovers; at t5, cell1 meets the conditions, cell1 discharges, and cell2 recovers; at t6, the battery pack is charged, and the cell is still discharging, and the cell2 voltage remains almost unchanged; at t7, cell1 meets the conditions, and cell1 discharges; at t8, cell2 meets the conditions, cell2 discharges, and cell1 recovers; at t9, no cell has a difference greater than 1 / 2V from the mean delta , cell2 recovers, the active balancing process ends, and the voltage of all cells is within (-1 / 2V of the mean voltage delta , 1 / 2V delta ) interval, the voltage difference between each cell does not exceed V delta Note that after charging ends at t6, this strategy still balances the voltage difference between cell1 and cell2 to other cells.

[0109] like Figure 7 As shown, an embodiment of the present invention provides a schematic diagram of an active balancing process. Active balancing start condition: During the charging process, at least one cell voltage in the discharge group is higher than the charging threshold V chg Or during the discharge process, at least one cell voltage in the charging group is lower than the discharge threshold V dischg ; Note: The charging process does not require the existence of a charging group. If there is no charging group, the discharge group discharges the entire battery group; the discharge process does not require the existence of a discharge group. If there is no discharge group, the entire battery group charges the charging group. Active balancing end condition: There is no discharge group during the charging process or there is no charging group during the discharge process. The specific control process is: after reaching a certain number of charge and discharge times (for example, 100 times), a charge and discharge threshold correction is started. At this time, the control conversion matrix performs a complete charge and discharge on each battery cell in turn, and the battery terminal voltage is collected according to a fixed collection period during this process. Use the above self-learning algorithm to recalculate a charge start threshold V chg , discharge start threshold V dischg parameter.

[0110] In addition, during the normal charging and discharging process, the voltage of each cell in each battery string is collected according to a fixed collection period, and the average voltage V is calculated. avg , and then calculate the difference between the voltage of each battery cell and the voltage mean, and group the batteries into charging group, discharging group and intermediate group accordingly. Then judge whether the start / end conditions are met: if there is no discharging group during the charging process, the balancing will not be started; if there is a discharging group and the rest are intermediate groups, the balancing will be started, and the discharging group will discharge the entire battery group through the balancing circuit; if there are a discharging group and a charging group, the discharging group will charge the charging group through the balancing circuit; if the discharging group enters the intermediate group range through the discharge voltage difference (that is, there is no discharging group), the balancing will end. If there is no charging group during the discharging process, the balancing will not be started; if there is a charging group and the rest are intermediate groups, the balancing will be started, and the entire battery group will charge the charging group through the balancing circuit; if there are a discharging group and a charging group, the discharging group will charge the charging group through the balancing circuit; if the charging group voltage difference enters the intermediate group range after charging (that is, there is no charging group), the balancing will end.

[0111] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0112] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0113] Figure 8 The structure diagram of an active balancing control device for an energy storage battery pack provided by an embodiment of the present invention is shown. The control device 400 includes a communication module 401 and a processing module 402 .

[0114] The communication module 401 is used to monitor the charge and discharge status of the battery pack and the real-time voltage of each battery in the battery pack.

[0115] The processing module 402 is used to determine whether the battery pack enters the active balancing mode based on the charge and discharge status and the real-time voltage; if the battery pack enters the active balancing mode, the average voltage of multiple batteries in the battery pack is calculated; and the mean difference between the real-time voltage and the average voltage of each battery is calculated; based on the average voltage and a preset mean difference threshold, the balancing interval is determined, and the balancing interval includes a charging interval, an intermediate interval and a discharging interval; the mean difference threshold is the maximum difference between the battery voltage and the average voltage when charging or discharging is completed; based on the real-time voltage, mean difference and balancing interval of each battery, each battery is actively balanced and controlled to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack.

[0116] Fig. 9Schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. Fig. 9 As shown, the electronic device 500 includes: a processor 501, a memory 502, and a computer program 503 stored in the memory 502 and executable on the processor 501. When the processor 501 executes the computer program 503, the steps in the above-mentioned method embodiments are implemented, for example Figure 3 Alternatively, when the processor 501 executes the computer program 503, the functions of each module / unit in the above-mentioned device embodiments are realized, for example, Figure 8 The functions of the communication module 401 and the processing module 402 are shown.

[0117] Exemplarily, the computer program 503 may be divided into one or more modules / units, which are stored in the memory 502 and executed by the processor 501 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments that can implement specific functions, and the instruction segments are used to describe the execution process of the computer program 503 in the electronic device 500. For example, the computer program 503 may be divided into Figure 8 A communication module 401 and a processing module 402 are shown.

[0118] The processor 501 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0119] The memory 502 may be an internal storage unit of the electronic device 500, such as a hard disk or memory of the electronic device 500. The memory 502 may also be an external storage device of the electronic device 500, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the electronic device 500. Further, the memory 502 may also include both an internal storage unit of the electronic device 500 and an external storage device. The memory 502 is used to store the computer program and other programs and data required by the terminal. The memory 502 may also be used to temporarily store data that has been output or is to be output.

[0120] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. An active balancing control method for a battery pack for energy storage, characterized in that: include: Monitoring the charge and discharge status of the battery pack and the real-time voltage of each battery in the battery pack; Based on the charge and discharge state and the real-time voltage, determining whether the battery pack enters an active balancing mode; If the battery pack enters the active balancing mode, the average voltage of the multiple batteries in the battery pack is calculated; and the mean difference between the real-time voltage of each battery and the average voltage is calculated; Based on the average voltage and a preset mean difference threshold, determining a balancing interval, wherein the balancing interval includes a charging interval, an intermediate interval, and a discharging interval; The mean difference threshold is the maximum difference between the battery voltage and the average voltage when charging or discharging is completed; Based on the real-time voltage, mean difference and balancing interval of each battery, active balancing control is performed on each battery to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack.

2. The active balancing control method for an energy storage battery pack according to claim 1, characterized in that: The determining whether the battery pack enters an active balancing mode based on the charge and discharge state and the real-time voltage of each battery includes: If the battery pack is in a charging state, and the real-time voltage of at least one battery in the battery pack is greater than a charging start threshold, determining that the battery pack enters an active balancing mode; If the battery pack is in a charging state and the real-time voltage of each battery in the battery pack is less than or equal to a charging start threshold, it is determined that the battery pack is in a normal charging mode; If the battery pack is in a discharging state, and the real-time voltage of at least one battery in the battery pack is less than a discharge start threshold, determining that the battery pack enters an active balancing mode; If the battery pack is in a discharging state, and the real-time voltage of each battery in the battery pack is greater than or equal to a discharge start threshold, it is determined that the battery pack is in a normal discharging mode.

3. The active balancing control method for an energy storage battery pack according to claim 1, characterized in that: The determining of the balancing interval based on the average voltage and a preset mean difference threshold includes: The middle interval is determined by taking the average voltage as the center of the middle interval and the mean difference threshold as the range of the middle interval; The range in which the real-time voltage is greater than the upper limit of the middle interval is determined as the discharge interval; The range in which the real-time voltage is less than the lower limit of the middle interval is determined as the charging interval.

4. The active balancing control method for an energy storage battery pack according to claim 1, characterized in that: The method of actively balancing each battery based on the real-time voltage, mean difference and balancing interval of each battery to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack includes: If the battery pack is in a charging state, the real-time voltage of the target battery is greater than the charging start threshold, and the mean difference of the target battery is in the middle interval or the charging interval, the target battery is kept in a charging state unchanged; the target battery is any battery in the battery pack; If the battery pack is in a charging state, the real-time voltage of the target battery is greater than the charging start threshold, and the mean difference of the target battery is in a discharging interval, the target battery is controlled to enter a discharging state.

5. The active balancing control method for an energy storage battery pack according to claim 4, characterized in that: The method of actively balancing each battery based on the real-time voltage, the mean difference and the balancing interval of each battery to achieve power balancing of multiple batteries during the charging and discharging process of the battery pack also includes: If the battery pack is in a discharging state, the real-time voltage of the target battery is less than the discharge start threshold, and the mean difference of the target battery is in the middle interval or the discharging interval, the target battery is kept in the discharging state; If the battery pack is in a discharging state, the real-time voltage of the target battery is less than the discharge start threshold, and the mean difference of the target battery is in a charging interval, the target battery is controlled to enter a charging state.

6. The active balancing control method for an energy storage battery pack according to claim 1, characterized in that: The method further comprises: Monitoring the number of charge and discharge times of the battery pack; If the number of charge and discharge times is greater than or equal to the set number of times, the threshold update process is started to update the charge start threshold and the discharge start threshold.

7. The active balancing control method for an energy storage battery pack according to claim 6, characterized in that: The start threshold update process updates the charge start threshold and the discharge start threshold, including: Acquiring charging and discharging data of each battery in the battery pack, wherein the charging and discharging data includes the battery voltage at each moment during the charging process or the discharging process; Based on the charge and discharge data of each battery, calculating the battery voltage slope of each battery at each moment during the charging process or the discharging process; Based on the battery voltage slope and a preset slope threshold, determining the terminal voltage of each battery, wherein the terminal voltage includes a charging terminal voltage and a discharging terminal voltage; Calculating an average value of the charging terminal voltage based on the charging terminal voltage of each battery in the battery pack; Based on the average value of the charging terminal voltage, updating the charging start threshold; Calculating an average value of the discharge terminal voltage based on the discharge terminal voltage of each battery in the battery pack; Based on the average value of the discharge terminal voltage, a discharge start threshold is updated.

8. The active balancing control method for an energy storage battery pack according to claim 1, characterized in that: The method further comprises: If the battery group is in a charging state, then based on the real-time voltage of each battery and the balancing interval, determine the category of each battery group, the category including a charging group, a discharging group and an intermediate group; If each battery in the battery pack is an intermediate group, determining that active balancing of the battery pack is completed, controlling the battery pack to exit the active balancing mode, and charging is completed; If the battery pack is in a discharging state, determining the category of each battery pack based on the real-time voltage of each battery and the balancing interval, the category including a charging group, a discharging group and an intermediate group; If each battery in the battery group is an intermediate group, it is determined that active balancing of the battery group is completed, and the battery group is controlled to exit the active balancing mode, and the discharge is completed.

9. The active balancing control method for an energy storage battery pack according to any one of claims 1 to 8, characterized in that: The method is applied to a balancing control circuit, wherein the balancing control circuit includes a flyback transformer corresponding to each battery; the primary side of the flyback transformer is connected to the battery through a primary side switch, and the secondary side of the flyback transformer is connected to a balancing bus through a secondary side switch; The controlling the target battery to enter a discharge state includes: Step 11, control the primary switch to be closed and the secondary switch to be opened; Step 12, monitoring the real-time current of the primary side of the flyback transformer; Step 13, if the real-time current of the primary side of the flyback transformer reaches a preset peak current, the primary side switch is controlled to be disconnected and the secondary side switch is controlled to be closed; Step 14, monitoring the real-time current of the secondary side of the flyback transformer; Step 15, if the real-time current of the secondary side of the flyback transformer decreases to zero, control the secondary side switch to be disconnected and the primary side switch to be closed; Step 16, repeating steps 11 to 16 to achieve target battery discharge; The controlling the target battery to enter a charging state comprises: Step 21, control the secondary switch to close and the primary switch to open; Step 22, monitoring the real-time current of the secondary side of the flyback transformer; Step 23, if the real-time current of the secondary side of the flyback transformer reaches a preset peak current, the secondary side switch is controlled to be disconnected and the primary side switch is controlled to be closed; Step 24, monitoring the real-time current of the primary side of the flyback transformer; Step 25, if the real-time current of the primary side of the flyback transformer decreases to zero, the primary side switch is controlled to be disconnected and the secondary side switch is controlled to be closed; Step 26, repeating steps 21 to 26 to achieve target battery charging.

10. An electronic device, characterized in that: The electronic device comprises a memory and a processor, the memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to execute the steps of the method as claimed in any one of claims 1 to 9.

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