Battery pack parallel charging and discharging control method and device and storage medium

Abstract

The invention discloses a battery pack parallel charging and discharging control method and device and a storage medium, and the method is executed by a parallel system, and comprises the steps: determining a working mode of the parallel system, and obtaining the current state parameters of each battery pack; wherein the working modes comprise a waiting mode, a mixed operation mode and a full-load operation mode; the state parameters comprise real-time current, real-time voltage and real-time internal resistance value; determining a corresponding control index based on the working mode; wherein the control indexes comprise at least one of equivalent static voltage and hedging current; the equivalent static voltage is calculated by the state parameters; and based on the working mode and the control index, controlling whether each battery pack participates in charging and discharging. According to the invention, the parallel operation of the battery packs with different voltages can be effectively controlled, so that the high-current hedging phenomenon is avoided.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a battery pack parallel charging and discharging control method, device and computer-readable storage medium. Background Art

[0002] In multi-battery parallel applications, especially when battery packs of different voltage levels are connected in parallel, how to effectively control the parallel working state of each battery pack (i.e. whether it is involved in charging or discharging) is a very challenging problem. The voltage difference of the battery pack may cause the instantaneous flow of large current, which in turn causes the current hedging phenomenon between the battery packs. This large current hedging phenomenon will not only shorten the service life of the battery pack, but may also cause safety hazards such as overheating, damage and even fire. Therefore, how to effectively control the parallel operation of battery packs with different voltages is an urgent problem to be solved. Summary of the invention

[0003] The purpose of the embodiments of the present invention is to provide a battery pack parallel charging and discharging control method, device and computer-readable storage medium, which can effectively control battery packs with different voltages to work in parallel to avoid large current hedging.

[0004] A first aspect of the present invention provides a battery pack parallel charging and discharging control method, which is performed by a parallel system, and the method includes:

[0005] Determine the working mode of the parallel system and obtain the current state parameters of each battery pack; wherein the working mode includes: waiting mode, mixed operation mode and full load operation mode; the state parameters include: real-time current, real-time voltage, real-time internal resistance value;

[0006] Based on the working mode, a corresponding control index is determined; wherein the control index includes: at least one of an equivalent static voltage and a countercurrent; the equivalent static voltage is calculated from the state parameter;

[0007] Based on the working mode and the control index, whether each of the battery packs participates in charging and discharging is controlled.

[0008] Optionally, based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes:

[0009] When the parallel system is in the waiting mode, obtaining the equivalent static voltage of all waiting battery packs;

[0010] When the parallel system releases the waiting mode and starts discharging, the maximum value of the equivalent static voltages of all the waiting battery packs is used as a reference voltage to control the waiting battery packs within a preset voltage range to participate in the discharging;

[0011] When the parallel system is released from the waiting mode for charging, the minimum value of the equivalent static voltages of all the waiting battery packs is used as a reference voltage to control the waiting battery packs within a preset voltage range to participate in charging.

[0012] Optionally, based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes:

[0013] When the parallel system is in the mixed operation mode, obtaining equivalent static voltages of all operating battery packs and waiting battery packs, and hedging currents between all the operating battery packs;

[0014] Determining whether the hedging current exceeds a preset current threshold;

[0015] If it exceeds, when the parallel system is discharging, the passively charged battery pack is stopped from working so that the passively charged battery pack enters a waiting state, or, when the parallel system is charging, the passively discharged battery pack is stopped from working so that the passively discharged battery pack enters a waiting state, and the passively charged or passively discharged battery pack is prohibited from participating in the work within a preset time range;

[0016] If it does not exceed, the median value of the equivalent static voltage corresponding to all the running battery packs is used as the reference voltage to control the waiting battery packs within the preset voltage range to participate in charging or discharging.

[0017] Optionally, based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes:

[0018] When the parallel system is in the full-load operation mode, obtaining the hedging current between all the operating battery packs;

[0019] Determining whether the hedging current exceeds a preset current threshold;

[0020] If it exceeds, when the parallel system is discharging, the passively charged battery pack is stopped from working so that the passively charged battery pack enters a waiting state, or, when the parallel system is charging, the passively discharged battery pack is stopped from working so that the passively discharged battery pack enters a waiting state, and the passively charged or passively discharged battery pack is prohibited from participating in the work within a preset time range;

[0021] If not exceeded, all the operating battery packs continue to charge or discharge.

[0022] Optionally, the equivalent static voltage is calculated by the following formula:

[0023]

[0024] in, is the equivalent static voltage; U t is the real-time voltage; I t is the real-time current; R t is the real-time internal resistance of the battery pack; P state is a state variable. If the battery pack is in a discharging state, then P state =1; if the battery pack is in charging state, then P state =-1; if the battery pack is in waiting state, then P state =0.

[0025] Optionally, the real-time internal resistance is obtained by the following steps:

[0026] When the current battery monitoring parameters of the battery pack are obtained, the battery monitoring parameters are input into the battery pack internal resistance model to obtain the real-time internal resistance of the battery pack; wherein the battery monitoring parameters include: battery temperature and battery power;

[0027] When obtaining the current cell monitoring parameters of at least one cell in the battery pack, the cell monitoring parameters are input into the cell internal resistance model to obtain the corresponding real-time internal resistance of the cell; based on the real-time internal resistance of the cell, the corresponding real-time internal resistance of the battery pack is obtained; wherein the cell monitoring parameters include: cell temperature, cell power, real-time cell current and number of cycles.

[0028] Optionally, the battery pack internal resistance model is obtained by the following steps:

[0029] S11: During the discharge or charge process of the battery pack, regulating the battery temperature, and obtaining all test internal resistances within a preset time window and whose battery power changes within a preset change range;

[0030] S12: based on a preset internal resistance range corresponding to the battery temperature, selecting qualified internal resistances from all the tested internal resistances; and calculating an average internal resistance based on all the qualified internal resistances;

[0031] S13: When the differences between all the qualified internal resistances and the average internal resistance do not exceed the preset deviation threshold, storing the average internal resistance in a data group corresponding to battery temperature-battery power-average internal resistance;

[0032] S14: Repeat steps S11 to S13 to obtain the data groups corresponding to different battery temperatures, and establish a relationship function between the battery power and the average internal resistance of the battery pack in each temperature range to obtain the battery pack internal resistance model.

[0033] Optionally, the cell internal resistance model is obtained by the following steps:

[0034] In the process of discharging or charging the battery cell using a current pulse, the real-time current of the battery cell, the temperature of the battery cell and the number of cycles are used as control variables to obtain a plurality of data pairs consisting of the battery cell power and the real-time internal resistance of the battery cell;

[0035] Based on all the data pairs, a relationship function between the battery cell power and the real-time internal resistance of the battery cell under different control variables is established to obtain the battery cell internal resistance model.

[0036] Optionally, obtaining the corresponding real-time internal resistance of the battery pack based on the real-time internal resistance of the battery cell is specifically:

[0037] The corresponding real-time internal resistance of the battery pack is obtained according to the following formula:

[0038]

[0039] Among them, R t is the real-time internal resistance of the battery pack; S is the number of cells in series in the battery pack; P is the number of cells in parallel in the battery pack; r t is the real-time internal resistance of a single battery cell, and R is the internal resistance of the connecting piece and electronic components.

[0040] A second aspect of the present invention provides a battery pack parallel charge and discharge control device, comprising:

[0041] A data acquisition module, used to determine the working mode of the parallel system and obtain the current state parameters of each battery pack; wherein the working mode includes: waiting mode, mixed operation mode and full load operation mode; the state parameters include: real-time current, real-time voltage, real-time internal resistance value;

[0042] A control index determination module, used to determine a corresponding control index based on the working mode; wherein the control index includes: at least one of an equivalent static voltage and a countercurrent; the equivalent static voltage is calculated from the state parameter;

[0043] The charge and discharge control module is used to control whether each battery pack participates in charge and discharge based on the working mode and the control index.

[0044] An embodiment of the third aspect of the present invention provides a computer-readable storage medium, which includes a stored computer program; wherein, when the computer program is running, it controls the device where the computer-readable storage medium is located to execute the battery pack parallel charging and discharging control method described in any embodiment of the first aspect above.

[0045] Compared with the prior art, the embodiments of the present invention provide a battery pack parallel charge and discharge control method, device and computer-readable storage medium, the method is executed by the parallel system, including: determining the working mode of the parallel system, and obtaining the current state parameters of each battery pack; wherein the working mode includes: waiting mode, mixed operation mode and full load operation mode; the state parameters include: real-time current, real-time voltage, real-time internal resistance; based on the working mode, determine the corresponding control index; wherein the control index includes: at least one of equivalent static voltage and hedging current; the equivalent static voltage is calculated by the state parameter; based on the working mode and the control index, control whether each battery pack participates in charging and discharging. The present invention can effectively control the parallel operation of battery packs with different voltages to avoid the phenomenon of large current hedging. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of an embodiment of the battery pack voltage recovery provided by the present invention.

[0047] Figure 2 It is a flow chart of an embodiment of a battery pack parallel charging and discharging control method provided by the present invention;

[0048] Figure 3 is a schematic diagram of an embodiment of a parallel system working mode provided by the present invention;

[0049] Figure 4 This is an example diagram of an embodiment of the change of the internal resistance of the battery cell provided by the present invention;

[0050] Figure 5 It is a structural schematic diagram of an embodiment of a battery pack parallel charge and discharge control device provided by the present invention. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this technical field without creative work are within the scope of protection of the present invention.

[0052] In order to better understand the technical solution in the embodiment of the present invention, the following describes the findings of the inventors during the experiment:

[0053] Taking the discharge process of a battery pack as an example, when the battery pack is discharging, a voltage drop will occur due to the existence of internal resistance. After the discharge stops, the voltage of the battery pack will rebound. Figure 1 When the battery pack is charging, the voltage will increase due to the existence of internal resistance, and the voltage of the battery pack will drop after charging stops.

[0054] When multiple battery packs are connected in parallel, there may be significant voltage differences between the battery packs, such as when initially assembled in parallel. During discharge, the parallel system will allow the high-voltage battery pack to discharge first, and the low-voltage battery pack will wait. During continuous discharge, the voltage of the high-voltage battery pack will drop due to the voltage drop caused by the internal resistance of the battery pack and the high-current discharge. The inventors found that if the real-time voltage is directly used for comparison at this time, the charge and discharge switches corresponding to the low-voltage battery pack with similar real-time voltage and in a waiting state are turned on to participate in the discharge output, then when the parallel system suddenly stops discharging, due to the lack of current, the voltage drop of the internal resistance of the battery pack is 0V, and the voltage of the battery pack will suddenly rise, which will cause the voltage difference between the high-voltage battery pack and the low-voltage battery pack to increase, and even exceed the designed safety range, and ultimately cause a large current hedging phenomenon between the two battery packs after the charge and discharge switches are turned on.

[0055] For example, when the charge and discharge switches of the two battery packs are not turned on, the #1 high-voltage battery pack is 52V@0A, and the #2 low-voltage battery pack is 50V@0A; if the parallel system needs to be discharged, the #1 battery pack is turned on first. At this time, the internal resistance of the #1 battery pack is 90mR, the output current is 30A, and the real-time voltage of the #1 battery pack is 49V@30A. If the real-time voltage comparison is used directly at this time (the preset safety voltage difference <= 1V), the #2 battery pack will be turned on for discharge output. The #2 battery pack will have a small current discharge, and the #1 battery pack will bear a large current discharge. When the system suddenly stops discharging, the output current disappears, the voltage of the #1 battery pack rises, and the voltage difference between the #1 and #2 battery packs can eventually reach 2V, which obviously exceeds the preset safety voltage difference, which will cause a large current hedging phenomenon.

[0056] If the equivalent static voltage in the present invention (the voltage of the battery pack when charging and discharging just stops) is used as a comparison, then when the #1 battery pack is discharged at 30A, the equivalent static voltage is 49+30*0.09=51.7V; since the #2 battery pack is not discharged, the equivalent static voltage is 50V. Obviously, at this time, the voltage difference between the #1 and #2 battery packs exceeds the preset safety voltage difference, so the #2 battery pack is not allowed to participate in the discharge, thereby avoiding the occurrence of large current hedging.

[0057] The technical solution provided by the embodiments of the present invention will be described in detail below.

[0058] See also Figure 2 , is a flow chart of an embodiment of a battery pack parallel charging and discharging control method provided by the present invention.

[0059] The first aspect of the present invention provides a battery pack parallel charging and discharging control method, which is performed by a parallel system. The method includes steps S1 to S3, which are specifically as follows:

[0060] Step S1: determining the working mode of the parallel system and obtaining the current state parameters of each battery pack; wherein the working mode includes: waiting mode, mixed operation mode and full load operation mode; the state parameters include: real-time current, real-time voltage and real-time internal resistance value;

[0061] Step S2: Based on the working mode, determine the corresponding control index; wherein the control index includes: at least one of an equivalent static voltage and a countercurrent; the equivalent static voltage is calculated by the state parameter;

[0062] Step S3: Based on the working mode and the control index, control whether each of the battery packs participates in charging and discharging.

[0063] It should be noted that when the parallel system is in waiting mode, all battery packs in the system are waiting battery packs (waiting for charging or waiting for discharging, and the corresponding charging and discharging switches are turned off). Figure 3 (a) As shown; in the waiting mode, the control index includes the equivalent static voltage, so that the parallel system can determine which waiting battery packs participate in charging and discharging through the comparison of the equivalent static voltage, thereby avoiding the large current hedging phenomenon.

[0064] When the parallel system is in mixed operation mode, part of all battery packs in the system are operating battery packs (charging or discharging, and the corresponding charge and discharge switches are turned on), and the rest are waiting battery packs, such as Figure 3 (b) is shown. In other words, when the parallel system is in the mixed operation mode and charging, part of the battery packs in the system are in the charging state, and the other part of the battery packs are in the waiting state; when the parallel system is in the mixed operation mode and discharging, part of the battery packs in the system are in the discharging state, and the other part of the battery packs are in the waiting state. In the mixed operation mode, the control indicators include equivalent static voltage and hedging current, so that the parallel system can determine which waiting battery packs participate in charging and discharging through the comparison of equivalent static voltage, and determine which operating battery packs exit charging and discharging through the comparison of hedging current, so as to avoid large current hedging phenomenon.

[0065] When the parallel system is in full load operation mode, all battery packs in the system are operating battery packs, such as Figure 3 (c) As shown; in the full-load operation mode, the control index includes the hedging current, so that the parallel system can determine which specific operating battery packs to exit charging and discharging through the comparison of the hedging current, thereby avoiding the large current hedging phenomenon.

[0066] In an optional embodiment, the equivalent static voltage is calculated by the following formula:

[0067]

[0068] in, is the equivalent static voltage; U t is the real-time voltage; I t is the real-time current; R t is the real-time internal resistance of the battery pack; P state is a state variable. If the battery pack is in a discharging state, then P state =1; if the battery pack is in charging state, then P state =-1; if the battery pack is in waiting state, then P state =0.

[0069] It should be noted that the equivalent static voltage is the voltage of the battery pack when charging and discharging have just stopped. During the discharge process, the internal resistance of the battery pack will produce a voltage drop, making the detected real-time voltage smaller than the equivalent static voltage. During the charging process, the internal resistance of the battery pack increases the voltage, making the detected real-time voltage larger than the equivalent static voltage. During the waiting process, since there is no real-time current flow (I t =0A), there is no need to obtain the real-time internal resistance of the battery pack, and the real-time voltage detected is the equivalent static voltage.

[0070] In an optional embodiment, based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes:

[0071] When the parallel system is in the waiting mode, obtaining the equivalent static voltage of all waiting battery packs;

[0072] When the parallel system releases the waiting mode and starts discharging, the maximum value of the equivalent static voltages of all the waiting battery packs is used as a reference voltage to control the waiting battery packs within a preset voltage range to participate in the discharging;

[0073] When the parallel system is released from the waiting mode for charging, the minimum value of the equivalent static voltages of all the waiting battery packs is used as the reference voltage to control the waiting battery packs within the preset voltage range to participate in the charging.

[0074] It should be noted that when the parallel system is in waiting mode, all battery packs are waiting battery packs, and the charge and discharge switches are not turned on. Figure 3 (a) shows that the real-time current of the waiting battery pack is 0A, and its equivalent static voltage = the real-time voltage.

[0075] The embodiment of the present invention can directly use the equivalent static voltage (real-time voltage) of all waiting battery packs for comparison, and select the battery packs whose voltage difference is within a preset safety range to participate in charging and discharging. Specifically, when the parallel system is released from the waiting mode for discharging, the highest equivalent static voltage value is used as the reference voltage, and all battery packs whose difference with the reference voltage is within a preset safety range are allowed to participate in the discharge, and the remaining battery packs remain in the waiting state. Similarly, when the parallel system is released from the waiting mode for charging, the lowest equivalent static voltage value is used as the reference voltage, and all battery packs whose difference with the reference voltage is within a preset safety range are allowed to participate in the charging, and the remaining battery packs remain in the waiting state.

[0076] It is worth noting that when the parallel system stops working, that is, the charging and discharging functions of the system are turned off, all battery packs in the system are in a waiting state; when the parallel system is connected to a charger, the system will release the waiting mode and charge; when the parallel system is ready to provide power to the load, the system will release the waiting mode and discharge.

[0077] In an optional embodiment, based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes:

[0078] When the parallel system is in the mixed operation mode, obtaining equivalent static voltages of all operating battery packs and waiting battery packs, and hedging currents between all the operating battery packs;

[0079] Determining whether the hedging current exceeds a preset current threshold;

[0080] If it exceeds, when the parallel system is discharging, the passively charged battery pack is stopped from working so that the passively charged battery pack enters a waiting state, or, when the parallel system is charging, the passively discharged battery pack is stopped from working so that the passively discharged battery pack enters a waiting state, and the passively charged or passively discharged battery pack is prohibited from participating in the work within a preset time range;

[0081] If it does not exceed, the median value of the equivalent static voltage corresponding to all the running battery packs is used as the reference voltage to control the waiting battery packs within the preset voltage range to participate in charging or discharging.

[0082] It should be noted that when the parallel system is in mixed operation mode, some battery packs are operating battery packs and the remaining battery packs are waiting battery packs, such as Figure 3(b) is shown. First, determine whether there is a large current counter-charge between the operating battery packs that are discharging or charging; if there is a large current counter-charge, when the parallel system is discharging, the passively charged battery pack will be withdrawn from work and the passively charged battery pack will enter a waiting state, or, when the parallel system is charging, the passively discharged battery pack will be withdrawn from work and the passively discharged battery pack will enter a waiting state, and these passively charged battery packs or passively discharged battery packs are not allowed to re-participate in the work within a short time range (such as within 1 minute) to prevent them from frequently joining and being withdrawn again, reducing the instability of the system. After confirming that there is no large current counter-charge, use the median value of the equivalent static voltage corresponding to the operating battery pack as the reference voltage, that is, (highest equivalent static voltage + lowest equivalent static voltage) / 2; then, compare the equivalent static voltage of the waiting battery pack with the reference voltage, and the waiting battery pack whose voltage difference is within the preset safety range is allowed to join the charging or discharging process.

[0083] It is worth noting that in the hybrid operation mode, if only one operating battery pack is being charged and discharged, there are no other battery packs involved in the charging and discharging. Therefore, the hedging current of the operating battery pack is 0A (must be within the preset current threshold), and its equivalent static voltage will be directly used as the reference voltage.

[0084] In an optional embodiment, based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes:

[0085] When the parallel system is in the full-load operation mode, obtaining the hedging current between all the operating battery packs;

[0086] Determining whether the hedging current exceeds a preset current threshold;

[0087] If it exceeds, when the parallel system is discharging, the passively charged battery pack is stopped from working so that the passively charged battery pack enters a waiting state, or, when the parallel system is charging, the passively discharged battery pack is stopped from working so that the passively discharged battery pack enters a waiting state, and the passively charged or passively discharged battery pack is prohibited from participating in the work within a preset time range;

[0088] If not exceeded, all the operating battery packs continue to charge or discharge.

[0089] It should be noted that when the parallel system is in full load operation mode, all battery packs are operating battery packs (when the system is discharging, all battery packs are in the discharging state; when the system is charging, all battery packs are in the charging state). Figure 3In order to more clearly describe the technical solution provided by the embodiment of the present invention, some examples are provided below for reference:

[0090] Example 1: When the waiting battery pack is converted to the operating battery pack, it is judged based on the equivalent static voltage at that time. In the full-load operation mode, all battery packs are continuously charged and discharged, and the charge and discharge current of the battery pack is dynamically changing (that is, it may increase or decrease). For example, during continuous discharge, if the output current increases, the equivalent static voltage calculated based on the current will increase due to the error caused by the current change, which may cause the voltage difference to exceed the preset safety range, but there may be no high-current charging between the battery packs; in this case, if there is no high-current charging phenomenon, the battery pack can still maintain a synchronous discharge state.

[0091] Example 2: When the battery pack is in full load operation mode and is continuously discharged, the power level of the battery pack continues to decrease. When the battery pack is at low power, its internal resistance will increase exponentially, making the error of the calculated equivalent static voltage larger, which may cause the voltage difference to exceed the preset safety range; in this case, if there is no high current charging phenomenon, the battery pack will still maintain the synchronous discharge state.

[0092] In Example 1 and Example 2, if large current charging occurs, the passively charged battery pack will be shut down and put into a waiting state when the parallel system is discharging, or the passively discharged battery pack will be shut down and put into a waiting state when the parallel system is charging, and the passively charged battery pack or the passively discharged battery pack will be prohibited from re-engaging within a preset time range.

[0093] In an optional embodiment, the real-time internal resistance is obtained by the following steps:

[0094] When the current battery monitoring parameters of the battery pack are obtained, the battery monitoring parameters are input into the battery pack internal resistance model to obtain the real-time internal resistance of the battery pack; wherein the battery monitoring parameters include: battery temperature and battery power;

[0095] When obtaining the current cell monitoring parameters of at least one cell in the battery pack, the cell monitoring parameters are input into the cell internal resistance model to obtain the corresponding real-time internal resistance of the cell; based on the real-time internal resistance of the cell, the corresponding real-time internal resistance of the battery pack is obtained; wherein the cell monitoring parameters include: cell temperature, cell power, real-time cell current and number of cycles.

[0096] It should be noted that when calculating the equivalent static voltage, the real-time voltage and real-time current can be directly obtained through hardware, while the real-time internal resistance will change with the battery monitoring parameters or the battery cell monitoring parameters.

[0097] There are three ways to obtain real-time internal resistance. The first is that when the battery pack internal resistance model or the battery cell internal resistance model has not been established, the system can directly use the real-time estimated internal resistance or initial value; through the dynamic change calculation of voltage and current, the battery pack internal resistance is calculated in real time, that is, battery pack internal resistance = voltage change value / current change value. The second is to input the battery monitoring parameters into the battery pack internal resistance model to obtain the real-time internal resistance of the battery pack. The third is to input the battery cell monitoring parameters into the battery cell internal resistance model, first obtain the real-time internal resistance of the battery cell, and then further calculate the battery pack internal resistance based on the real-time internal resistance of the battery cell.

[0098] In a second implementation manner, the battery pack internal resistance model is obtained by the following steps:

[0099] S11: During the discharge or charge process of the battery pack, regulating the battery temperature, and obtaining all test internal resistances within a preset time window and whose battery power changes within a preset change range;

[0100] S12: based on the preset internal resistance range corresponding to the battery temperature, selecting qualified internal resistances from all the tested internal resistances; and calculating an average internal resistance based on all the qualified internal resistances;

[0101] S13: When the differences between all the qualified internal resistances and the average internal resistance do not exceed the preset deviation threshold, storing the average internal resistance in a data group corresponding to battery temperature-battery power-average internal resistance;

[0102] S14: Repeat steps S11 to S13 to obtain the data groups corresponding to different battery temperatures, and establish a relationship function between the battery power and the average internal resistance of the battery pack in each temperature range to obtain the internal resistance model of the battery pack.

[0103] It should be noted that the embodiment of the present invention mainly calculates the internal resistance of the battery pack through the voltage and current changes of the battery pack, and then obtains the internal resistance value through filtering and calibration steps, so as to further obtain multiple battery power-average internal resistance relationship functions through data fitting, thereby establishing a battery pack internal resistance model.

[0104] In specific implementation, the battery temperature is used as the control variable (in a temperature chamber), and at a fixed temperature, the real-time voltage and current of the battery pack at the previous moment and the current moment are collected, and the dynamic changes at these two moments are compared to calculate the internal resistance of the battery pack at the current moment (battery pack internal resistance = voltage change value / current change value). In actual situations, due to measurement uncertainty and transient effects, there may be certain errors, so these data need to be further processed:

[0105] First, a reasonable range table of internal resistance values ​​changing with temperature is established in advance; for the newly calculated internal resistance value (test internal resistance), the table is looked up according to the current temperature. If it exceeds the corresponding reasonable range, it is regarded as invalid data (discarded); if it is within the corresponding reasonable range, it is regarded as qualified internal resistance and put into the cache to facilitate subsequent average value calculation. Within the specified time window and the range of change of power (State of Charge, SOC), after obtaining multiple qualified internal resistance values ​​through multiple data collections, the average value of the qualified internal resistance values ​​in the cache is calculated. Then, each qualified internal resistance value in the cache is compared with the average internal resistance one by one. If the difference is within the preset deviation threshold range, it indicates that the data is stable and the average internal resistance can be used as the effective internal resistance value at that moment; if there is at least one difference that is not within the preset deviation threshold range, all cache values ​​are discarded and the collection is restarted. The number of caches can be set to 5, and the results collected in a short time will not be very different. After each average internal resistance is obtained, the cache is overwritten and updated, and the new qualified internal resistance overwrites the old cache value.

[0106] After obtaining the effective average internal resistance corresponding to the current temperature and SOC value, store it in the data group corresponding to the battery temperature-battery power-average internal resistance. Perform multiple experimental measurements (such as changing the battery temperature to perform a discharge test from full charge to feeding, or a charging test from feeding to full charge), and you can get several data groups for use in the subsequent establishment of the battery pack internal resistance model. Divide the data groups according to different temperature intervals. In each temperature interval, according to the SOC range and the corresponding average internal resistance, the change in the internal resistance of the battery from full charge to feeding (i.e., SOC from 100% to 0%) is segmented to establish a relationship function. For example, the SOC can be divided into several intervals such as 0-20%, 20%-40%, 40%-60%, 60%-80%, 80%-100%. The change in internal resistance in each interval can be assumed to be a linear change, and a linear fit can be performed to obtain the corresponding linear function. Through the above process, the relationship function between the battery power and the average internal resistance of the battery pack in each temperature range can be obtained, and finally a comprehensive model consisting of battery temperature, battery SOC and internal resistance can be established, namely, the battery pack internal resistance model. When using the battery pack internal resistance model, the corresponding relationship function can be found by the battery temperature, and then the corresponding battery pack internal resistance value in the relationship function can be located by the battery SOC value.

[0107] It is worth noting that when performing a charging test, the embodiment of the present invention actively creates current and voltage changes at different times by controlling the charging MOS of the battery pack (when using an intelligent charger, the charging current is controlled and there is no need to shut down the charging MOS), thereby obtaining an effective internal resistance value; in the discharge test, calculating the internal resistance value requires that the current difference between the two times is large and the current remains stable in a short time to reduce errors.

[0108] In a third embodiment, the cell internal resistance model is obtained by the following steps:

[0109] In the process of discharging or charging the battery cell using a current pulse, the real-time current of the battery cell, the temperature of the battery cell and the number of cycles are used as control variables to obtain a plurality of data pairs consisting of the battery cell power and the real-time internal resistance of the battery cell;

[0110] Based on all the data pairs, a relationship function between the battery cell power and the real-time internal resistance of the battery cell under different control variables is established to obtain the battery cell internal resistance model.

[0111] It should be noted that by obtaining several pairs of data of battery cell power-battery cell real-time internal resistance under different battery cell temperatures, battery cell real-time currents and cycle numbers, and then compiling a battery cell internal resistance model; and finally obtaining the real-time internal resistance of the battery pack through different series and parallel modes of the battery cells; wherein, the change of battery cell temperature is controlled by a temperature box, and the battery cell real-time current is controlled by charging and discharging through different current pulses.

[0112] The following description will be made by taking the discharge process as an example. Of course, the following specific embodiment is also applicable to the charging process after changing the "gradual discharge from full charge state to empty charge state" to "gradual charging from empty charge state to full charge state". Taking the discharge process as an example, the details are as follows:

[0113] The first step is to obtain the cell internal resistance data through fixed current pulse discharge. The cell is discharged by fixed current pulse discharge when the cell is fully charged. The internal resistance change of the cell from full charge to feeding under the current current and temperature is obtained by the difference between the voltage when the cell is discharged and the voltage before the next discharge after being stationary. The specific operation is: discharge->stationary->discharge->stationary->discharge->stationary->discharge->stationary, and repeat until the cell is discharged. During this process, the cell temperature is controlled by the temperature box.

[0114] The second step is to obtain the internal resistance data of the battery cell under different discharge currents. At the same temperature, use different current values ​​and follow the method in the first step to obtain the change in the internal resistance of the battery cell under different discharge rates. By sorting the data, the linear region, nonlinear region and boundary of the internal resistance change are divided, such as Figure 4 As shown. The linear region can be directly converted using the formula (linear fitting), while the nonlinear region can be divided into small areas according to the situation and processed by linear and table lookup methods. Figure 4 In the figure, the horizontal axis is the sampling points of SOC from high to low, and the nonlinear area is the area corresponding to the horizontal axis 7-9. Figure 4It shows that when the battery is fully charged to completely discharged, each curve represents a different current discharge. The broken line on the right represents the boundary of the voltage drop that can be maintained when the current is continuously discharged. If this boundary is exceeded, a large change will occur. This boundary is the voltage value of the battery at this current discharge when sampling. That is, when discharging, it is not necessary to re-look up the table above this voltage value, which is used to reduce the number of table lookups and calculations. Because the curves sampled by different cells are different, Figure 4 It is only shown as an example, and the specific curve graph should be drawn by actual sampling.

[0115] The third step is to obtain the internal resistance data of the battery cell at different temperatures. Change the test temperature of the battery cell by controlling the temperature box. Select the appropriate temperature value in different temperature ranges (such as low temperature range, normal temperature range, and high temperature range) and perform the test according to the first and second steps to obtain the internal resistance change data of the battery cell at different temperatures.

[0116] Step 4: Obtain the cell internal resistance data at different cycle times. Under multiple charge and discharge cycles (to measure the internal resistance change data of the cell at different aging levels), obtain the internal resistance change data according to steps 1 to 3, and finally obtain several cell power-cell real-time internal resistance data pairs corresponding to different cycle times, cell temperatures, and cell real-time currents.

[0117] The fifth step is comprehensive data analysis and establishment of the battery cell internal resistance model. According to the data pairs of battery cell power-battery cell real-time internal resistance under the above different control variables, piecewise linear fitting is performed to obtain the corresponding battery cell power-battery cell real-time internal resistance relationship function. Finally, a comprehensive model consisting of the number of cycles, battery cell temperature, battery cell real-time current, battery cell SOC and battery cell internal resistance is established, namely the battery cell internal resistance model. When using the battery cell internal resistance model, you can first find the corresponding table / relationship function through the number of cycles, battery cell temperature and battery cell real-time current, and then locate the corresponding battery cell internal resistance value in the table / relationship function through the battery cell SOC value.

[0118] Furthermore, the real-time internal resistance of the corresponding battery pack is obtained based on the real-time internal resistance of the battery cell, specifically:

[0119] The corresponding real-time internal resistance of the battery pack is obtained according to the following formula:

[0120]

[0121] Among them, R t is the real-time internal resistance of the battery pack; S is the number of cells in series in the battery pack; P is the number of cells in parallel in the battery pack; r t is the real-time internal resistance of a single battery cell, and R is the internal resistance of the connecting piece and electronic components.

[0122] Specifically, the embodiment of the present invention determines the overall internal resistance of the battery pack through the real-time internal resistance of a single battery cell, that is, the internal resistance of the battery pack = the internal resistance of the battery cell series and parallel + the internal resistance of the connecting piece + the internal resistance of the electronic device. In the above formula, the internal resistance of the connecting piece and the electronic device is recorded as R, which is less affected by temperature and can be regarded as a constant.

[0123] See also Figure 5 , is a structural schematic diagram of an embodiment of a battery pack parallel charge and discharge control device provided by the present invention.

[0124] The second aspect of the present invention provides a battery pack parallel charge and discharge control device, which is used to implement the battery pack parallel charge and discharge control method described in any embodiment of the first aspect, and the device includes:

[0125] The data acquisition module 11 is used to determine the working mode of the parallel system and obtain the current state parameters of each battery pack; wherein the working mode includes: waiting mode, mixed operation mode and full load operation mode; the state parameters include: real-time current, real-time voltage, real-time internal resistance value;

[0126] A control index determination module 12 is used to determine a corresponding control index based on the working mode; wherein the control index includes: at least one of an equivalent static voltage and a countercurrent; the equivalent static voltage is calculated by the state parameter;

[0127] The charge and discharge control module 13 is used to control whether each of the battery packs participates in charge and discharge based on the working mode and the control index.

[0128] It should be noted that the battery pack parallel charge and discharge control device provided in the second aspect of the present invention can implement all the processes of the battery pack parallel charge and discharge control method described in the first aspect of the present invention. The functions of each module in the device and the technical effects achieved are respectively the same as the functions and technical effects achieved by the battery pack parallel charge and discharge control method described in the first aspect of the present invention, and will not be repeated here.

[0129] An embodiment of the third aspect of the present invention provides a computer-readable storage medium, which includes a stored computer program; wherein, when the computer program is running, it controls the device where the computer-readable storage medium is located to execute the battery pack parallel charging and discharging control method described in any embodiment of the first aspect above.

[0130] In summary, the embodiments of the present invention provide a battery pack parallel charging and discharging control method, device and computer-readable storage medium. The method can effectively control the parallel operation of battery packs with different voltages (whether to participate in charging and discharging) without increasing any cost, so as to avoid the occurrence of large current hedging, especially when using relays as discharge (charging) switches.

[0131] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A battery pack parallel charging and discharging control method, characterized in that: Executed by a parallel system, the method comprises: Determine the working mode of the parallel system and obtain the current state parameters of each battery pack; wherein the working mode includes: waiting mode, mixed operation mode and full load operation mode; the state parameters include: real-time current, real-time voltage, real-time internal resistance value; Based on the working mode, a corresponding control index is determined; wherein the control index includes: at least one of an equivalent static voltage and a countercurrent; the equivalent static voltage is calculated by the state parameter; Based on the working mode and the control index, whether each of the battery packs participates in charging and discharging is controlled.

2. The battery pack parallel charging and discharging control method according to claim 1, characterized in that: Based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes: When the parallel system is in the waiting mode, obtaining the equivalent static voltage of all waiting battery packs; When the parallel system releases the waiting mode and starts discharging, the maximum value of the equivalent static voltages of all the waiting battery packs is used as a reference voltage to control the waiting battery packs within a preset voltage range to participate in the discharging; When the parallel system is released from the waiting mode for charging, the minimum value of the equivalent static voltages of all the waiting battery packs is used as a reference voltage to control the waiting battery packs within a preset voltage range to participate in charging.

3. The battery pack parallel charging and discharging control method according to claim 1, characterized in that: Based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes: When the parallel system is in the mixed operation mode, obtaining equivalent static voltages of all operating battery packs and waiting battery packs, and hedging currents between all the operating battery packs; Determining whether the hedging current exceeds a preset current threshold; If it exceeds, when the parallel system is discharging, the passively charged battery pack is stopped from working so that the passively charged battery pack enters a waiting state, or, when the parallel system is charging, the passively discharged battery pack is stopped from working so that the passively discharged battery pack enters a waiting state, and the passively charged or passively discharged battery pack is prohibited from participating in the work within a preset time range; If it does not exceed, the median value of the equivalent static voltage corresponding to all the running battery packs is used as the reference voltage to control the waiting battery packs within the preset voltage range to participate in charging or discharging.

4. The battery pack parallel charging and discharging control method according to claim 1, characterized in that: Based on the working mode and the control index, controlling whether each of the battery packs participates in charging and discharging includes: When the parallel system is in the full-load operation mode, obtaining the hedging current between all the operating battery packs; Determining whether the hedging current exceeds a preset current threshold; If it exceeds, when the parallel system is discharging, the passively charged battery pack is stopped from working so that the passively charged battery pack enters a waiting state, or, when the parallel system is charging, the passively discharged battery pack is stopped from working so that the passively discharged battery pack enters a waiting state, and the passively charged or passively discharged battery pack is prohibited from participating in the work within a preset time range; If not exceeded, all the operating battery packs continue to charge or discharge.

5. The battery pack parallel charging and discharging control method according to claim 1, characterized in that: The equivalent static voltage is calculated by the following formula: in, is the equivalent static voltage; U t is the real-time voltage; I t is the real-time current; R t is the real-time internal resistance of the battery pack; P state is a state variable. If the battery pack is in a discharging state, then P state =1; if the battery pack is in charging state, then P state =-1; if the battery pack is in waiting state, then P state =0.

6. The battery pack parallel charging and discharging control method according to claim 1, characterized in that: The real-time internal resistance is obtained by the following steps: When the current battery monitoring parameters of the battery pack are obtained, the battery monitoring parameters are input into the battery pack internal resistance model to obtain the real-time internal resistance of the battery pack; wherein the battery monitoring parameters include: battery temperature and battery power; When obtaining the current cell monitoring parameters of at least one cell in the battery pack, the cell monitoring parameters are input into the cell internal resistance model to obtain the corresponding real-time internal resistance of the cell; based on the real-time internal resistance of the cell, the corresponding real-time internal resistance of the battery pack is obtained; wherein the cell monitoring parameters include: cell temperature, cell power, real-time cell current and number of cycles.

7. The battery pack parallel charging and discharging control method according to claim 6, characterized in that: The battery pack internal resistance model is obtained by the following steps: S11: During the discharge or charge process of the battery pack, regulating the battery temperature, and obtaining all test internal resistances within a preset time window and whose battery power changes within a preset change range; S12: Screening out qualified internal resistances from all the tested internal resistances based on a preset internal resistance range corresponding to the battery temperature; And based on all the qualified internal resistances, an average internal resistance is calculated; S13: When the differences between all the qualified internal resistances and the average internal resistance do not exceed the preset deviation threshold, storing the average internal resistance in a data group corresponding to battery temperature-battery power-average internal resistance; S14: Repeat steps S11 to S13 to obtain the data groups corresponding to different battery temperatures, and establish a relationship function between the battery power and the average internal resistance of the battery pack in each temperature range to obtain the battery pack internal resistance model.

8. The battery pack parallel charging and discharging control method according to claim 6, characterized in that: The cell internal resistance model is obtained by the following steps: In the process of discharging or charging the battery cell using a current pulse, the real-time current of the battery cell, the temperature of the battery cell and the number of cycles are used as control variables to obtain a plurality of data pairs consisting of the battery cell power and the real-time internal resistance of the battery cell; Based on all the data pairs, a relationship function between the battery cell power and the real-time internal resistance of the battery cell under different control variables is established to obtain the battery cell internal resistance model.

9. The battery pack parallel charging and discharging control method according to claim 6, characterized in that: The real-time internal resistance of the battery pack is obtained based on the real-time internal resistance of the battery cell, specifically: The corresponding real-time internal resistance of the battery pack is obtained according to the following formula: Among them, R t is the real-time internal resistance of the battery pack; S is the number of cells in series in the battery pack; P is the number of cells in parallel in the battery pack; r t is the real-time internal resistance of a single battery cell, and R is the internal resistance of the connecting piece and electronic components.

10. A battery pack parallel charge and discharge control device, characterized in that: include: A data acquisition module, used to determine the working mode of the parallel system and obtain the current state parameters of each battery pack; wherein the working mode includes: waiting mode, mixed operation mode and full load operation mode; the state parameters include: real-time current, real-time voltage, real-time internal resistance value; A control index determination module, used to determine a corresponding control index based on the working mode; wherein the control index includes: at least one of an equivalent static voltage and a countercurrent; the equivalent static voltage is calculated from the state parameter; The charge and discharge control module is used to control whether each battery pack participates in charge and discharge based on the working mode and the control index.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program; wherein, when the computer program is run, it controls the device where the computer-readable storage medium is located to execute the battery pack parallel charging and discharging control method according to any one of claims 1 to 9.

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