Battery current balancing control method and battery current balancing control system

Abstract

The present invention discloses a battery current sharing control method and a battery current sharing control system. The method comprises: collecting the measured voltage of the battery string corresponding to each battery string; determining the target voltage of all the battery string branches; adjusting the current sharing DCDC converter based on the target voltage and the measured voltage of the battery string, so that the output voltage of the battery string branch is the target voltage, and realizing the voltage sharing control of the battery string; collecting the measured current of the battery string corresponding to each battery string; determining the target current of all the battery strings based on the measured current of the battery strings corresponding to all the battery strings; adjusting the current sharing DCDC converter based on the measured current of the battery strings corresponding to all the battery strings and the target current, so that the output current of the battery string branch is the target current, and realizing the current sharing control of the battery string. The method can realize non-impact current parallel connection, reduce the capacity loss of the battery string caused by parallel connection, and improve the battery capacity utilization rate of the battery string.

Description

Technical Field

[0001] The present invention relates to the technical field of battery production, and in particular to a battery current sharing control method and a battery current sharing control system. Background Art

[0002] When the current battery strings are connected in parallel to the busbar, due to the inconsistency of the battery string manufacturing and the use environment, there will be certain differences in their capacity, internal resistance, voltage and self-discharge rate. During the battery string charging and discharging process, some battery strings will be overcharged or overcharged, that is, the parallel battery strings are not current-balanced. With the increase in the number of battery string charge and discharge cycles and the influence of factors such as storage time and temperature, some battery strings are in an overcharged or over-discharged state for a long time, which will aggravate the inconsistency of the battery string on the one hand, and gradually cause battery degradation problems on the other hand, eventually causing the battery string to lose its ability to store electrical energy. Summary of the invention

[0003] The present invention provides a battery current sharing control method and a battery current sharing control system to solve the problems of large capacity loss and battery degradation caused by uneven current sharing of some battery strings in at least two battery strings connected in parallel.

[0004] The present invention provides a battery current sharing control method, which is applied to a battery current sharing control system, wherein the battery current sharing control system is provided with a plurality of parallel battery string branches, wherein the battery string branches are provided with a battery string and a current sharing DCDC converter connected in series with the battery string, comprising:

[0005] Collecting the measured voltage of the battery string corresponding to each of the battery strings;

[0006] determining target voltages for all of the battery string branches;

[0007] Based on the target voltage and the measured voltage of the battery string, adjusting the current sharing DCDC converter so that the output voltage of the battery string branch is the target voltage, thereby realizing voltage sharing control of the battery string;

[0008] Collecting the actual measured current of the battery string corresponding to each of the battery strings;

[0009] Determining target currents of all the battery strings based on the measured currents of the battery strings corresponding to all the battery strings;

[0010] Based on the measured current of the battery strings corresponding to all the battery strings and the target current, the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, thereby achieving current sharing control of the battery strings.

[0011] Preferably, the determining the target voltages of all the battery string branches comprises:

[0012] Based on the measured voltages of the battery strings corresponding to all the battery strings, determining the maximum voltage value among the measured voltages of the battery strings corresponding to all the battery strings as the target voltage of all the battery string branches;

[0013] Alternatively, based on the actually measured voltages of the battery strings corresponding to all the battery strings, a minimum voltage value among the actually measured voltages of the battery strings corresponding to all the battery strings is determined as the target voltage of all the battery string branches;

[0014] Alternatively, based on the measured voltages of the battery strings corresponding to all the battery strings, an average voltage value of the measured voltages of the battery strings corresponding to all the battery strings is determined as the target voltage of all the battery string branches;

[0015] Alternatively, the voltage of a bus connected to the plurality of battery string branches is determined as the target voltage of all the battery string branches.

[0016] Preferably, adjusting the current sharing DCDC converter based on the target voltage and the measured voltage of the battery string so that the output voltage of the battery string branch is the target voltage to achieve voltage sharing control of the battery string includes:

[0017] The target voltage and the measured voltage of each battery string corresponding to the battery string are calculated using the voltage correction value calculation formula corresponding to the target voltage to obtain the voltage correction value corresponding to the current sharing DCDC converter connected in series with each battery string; wherein the voltage correction value calculation formula is U obj i=U dcStd -U bat i,U obj i is the correction value of the voltage for equalizing, U dcStd is the target voltage, U bat i is the measured voltage of the battery string of the i-th battery string;

[0018] Based on the voltage balancing correction value corresponding to each current balancing DCDC converter, the duty cycle of the current balancing DCDC converter is adjusted so that the output voltage of the battery string branch is the target voltage, thereby realizing voltage balancing control of the battery string.

[0019] Preferably, before collecting the actual measured current of the battery string corresponding to each of the battery strings, the battery current sharing control method further includes:

[0020] Real-time acquisition of measured branch voltages corresponding to all battery strings;

[0021] If the measured voltages of the branches corresponding to all the battery strings are within the allowable error range of the target voltage, all the battery string branches are controlled to be connected in parallel to the busbar.

[0022] Preferably, after controlling all the battery string branches to be connected in parallel to the bus, the battery current sharing control method further comprises:

[0023] Collecting the current capacity of the battery string corresponding to all the battery string branches in real time, and determining whether the current capacity of the battery string is between the lower capacity limit of the battery string and the upper capacity limit of the battery string;

[0024] If the current capacity of the battery string corresponding to any of the battery string branches is not between the lower limit capacity of the battery string and the upper limit capacity of the battery string, the connection between the battery string branch and the bus is disconnected, and the acquisition of the measured voltage of the battery string corresponding to each of the battery strings is repeated.

[0025] Preferably, determining the target currents of all the battery strings based on the measured currents of the battery strings corresponding to all the battery strings includes:

[0026] Based on the actual measured currents of the battery strings corresponding to all the battery strings, taking the average current of the actual measured currents of the battery strings corresponding to all the battery strings as the target currents of all the battery strings;

[0027] Alternatively, the charge and discharge proportionality coefficient is calculated based on the current capacity of the battery strings corresponding to all the battery strings and the charge and discharge current limit; and the target current of all the battery strings is determined based on the actual measured current of the battery strings corresponding to all the battery strings and the charge and discharge proportionality coefficient.

[0028] Preferably, the current sharing DCDC converter is adjusted based on the measured current of the battery strings corresponding to all the battery strings and the target current so that the output current of the battery string branch is the target current to achieve current sharing control of the battery string, including:

[0029] The current-sharing voltage correction value calculation formula is used to calculate the measured current of the battery strings corresponding to all the battery strings and the target current, and obtain the current-sharing voltage correction value corresponding to the current-sharing DCDC converter connected in series with each battery string; the current-sharing voltage correction value calculation formula is DaltaU obj i=(I bat I obj i)*(K p +K i / s), DaltaU obj i is the current-sharing voltage correction value of the i-th battery string, I bat i is the measured current of the battery string of the ith battery string, I obj i is the target current of the ith battery string, K p is the preset proportionality factor, K i is the preset integral coefficient, s is the frequency domain;

[0030] Based on the current sharing voltage correction value corresponding to each current sharing DCDC converter, the duty cycle of the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, thereby realizing current sharing control of the battery string.

[0031] The present invention provides a battery current sharing control system, comprising a monitoring module and a plurality of battery string branches arranged in parallel on a bus, wherein the battery string branch comprises a battery string and a current sharing DCDC converter connected to the battery string, and the monitoring module is connected to the battery string and the current sharing DCDC converter, and is used to collect battery string status information of the battery string branch, and adjust the duty cycle of the current sharing DCDC converter based on the battery string status information to achieve current sharing control.

[0032] Preferably, the battery current sharing control system also includes a current sharing power supply; the current sharing DCDC converter is a non-isolated DCDC converter connected to the current sharing power supply; the input end of the non-isolated DCDC converter is connected to the current sharing power supply; the output end of the current sharing DCDC converter is connected to the battery string and the bus.

[0033] Preferably, the current sharing DCDC converter is an isolated DCDC converter; the input end of the isolated DCDC converter is connected to the battery string; the output end of the isolated DCDC converter is connected to the battery string and the bus.

[0034] In the above-mentioned battery current sharing control method, before the battery strings are connected in parallel, based on the measured voltage of the battery string corresponding to each battery string and the target voltage corresponding to all battery strings, the duty cycle of the current sharing DCDC converter is adjusted so that the output voltage of the battery string branch is the target voltage, and the voltage sharing control of the battery string is realized, which can achieve the purpose of non-impact current parallel connection. After the battery strings are connected in parallel, based on the measured current of the battery strings corresponding to all the battery strings and the target current, the duty cycle of the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, and the current sharing control of the battery string is realized. The current sharing control is realized, the capacity loss of the battery string caused by parallel connection is reduced, so as to improve the battery capacity utilization rate of the battery string, and the energy loss caused by the internal circulation at the end of charging and discharging can be reduced, which helps to ensure the service life of the parallel battery string and the safety of the battery string during charging and discharging.

[0035] In the above-mentioned battery current sharing control system, a battery string branch is formed by connecting the battery string in series with the current sharing DCDC converter, and the monitoring module is used to collect the battery string status information of the battery string branch. By processing the battery string status information, the current sharing DCDC converter is controlled to adjust its duty cycle to adjust the output current of the battery string, so that the parallel battery string branches can achieve the purpose of current sharing, reduce the capacity loss of the battery string caused by parallel connection, so as to improve the battery capacity utilization rate of each battery string, and reduce the energy loss caused by the internal circulation at the end of charging and discharging, which is helpful to ensure the service life of each battery string and ensure the safety of each battery string during charging and discharging. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0037] Figure 1 is a flow chart of a battery current balancing control method according to an embodiment of the present invention;

[0038] Figure 2 is another flow chart of a battery current balancing control method according to an embodiment of the present invention;

[0039] Figure 3 is another flow chart of a battery current balancing control method according to an embodiment of the present invention;

[0040] Figure 4 is a circuit diagram of a battery current balancing control system in one embodiment of the present invention;

[0041] Figure 5 is another circuit diagram of a battery current balancing control system in one embodiment of the present invention;

[0042] Figure 6 1 is another circuit diagram of a battery current sharing control system in one embodiment of the present invention. DETAILED DESCRIPTION

[0043] 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 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 field without creative work are within the scope of protection of the present invention.

[0044] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, providing these embodiments will make the disclosure thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

[0045] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there may be no intervening elements or layers. It should be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0046] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0047] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0048] In order to fully understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0049] An embodiment of the present invention provides a battery current sharing control method, which is applied to a battery current sharing control system, wherein the battery current sharing control system is provided with a plurality of parallel battery string branches, and the battery string branches are provided with battery strings and current sharing DCDC converters connected in series with the battery strings. The current sharing DCDC converter is a bidirectional DCDC converter, that is, a DCDC converter that can realize boost control and buck control. In this example, the battery current sharing control system also includes a monitoring module connected to the battery string and the current sharing DCDC converter, the monitoring module includes a sampling circuit and a controller connected to the sampling circuit, the sampling circuit is connected to the battery string and the current sharing DCDC converter, and is used to collect battery string status information of the battery string branch where the battery string and the current sharing DCDC converter are located, and feed back the battery string status information to the controller, the battery string status information includes but is not limited to the measured voltage of the battery string, the measured current of the battery string, the current capacity of the battery string, the measured voltage of the converter, the measured current of the converter, and the bus voltage, etc. The controller is also connected to the current-sharing DCDC converter to perform comprehensive calculation and judgment processing on the battery string status information to form a PWM signal. The PWM signal can be used to control the current-sharing DCDC converter to adjust its duty cycle and adjust the output current of each battery string to achieve the purpose of current-sharing output.

[0050] In one embodiment, if Figure 1 As shown, the battery current sharing control method includes the following steps:

[0051] S11: Collecting the actual measured voltage of the battery string corresponding to each battery string.

[0052] The measured voltage of the battery string refers to the voltage across the battery string collected in real time.

[0053] In this example, before the battery strings are connected in parallel, that is, when the controller controls all the switch contactors 40 in all the battery string branches to be disconnected, the actual measured voltage of the battery strings corresponding to each battery string is collected in real time through the sampling circuit, and the actual measured voltage of the battery strings corresponding to the collected battery strings is fed back to the controller, so that the controller obtains the actual measured voltage of the battery strings before all the battery strings are connected in parallel to the bus.

[0054] S12: Determine the target voltage of all battery string branches.

[0055] The target voltage is the desired voltage that needs to be adjusted for the battery string branch formed by the battery string and the current sharing DCDC converter connected in series therewith.

[0056] As an example, determining the target voltage of all battery string branches includes: based on the measured battery string voltages corresponding to all battery strings, determining the maximum voltage value among the measured battery string voltages corresponding to all battery strings as the target voltage of all battery string branches. For example, after obtaining the measured battery string voltages of all battery strings, the controller selects the maximum voltage value from the measured battery string voltages of all battery strings to determine as the target voltage, that is, U dcStd =max[U bat i],U dcStd is the target voltage, U bat i is the measured voltage of the battery string of the ith battery string, and n is the number of battery strings. In this example, the maximum voltage value among the measured voltages of the battery strings corresponding to all battery strings and the voltage values ​​within the allowable error range thereof can be determined as the target voltages of all battery string branches.

[0057] As an example, determining the target voltage of all battery string branches includes: based on the measured battery string voltages corresponding to all battery strings, determining the minimum voltage value among the measured battery string voltages corresponding to all battery strings as the target voltage of all battery string branches. For example, after obtaining the measured battery string voltages of all battery strings, the controller selects the minimum voltage value from the measured battery string voltages of all battery strings to determine as the target voltage, that is, U dcStd =min[U bat i],U dcStd is the target voltage, U bat i is the measured voltage of the battery string of the ith battery string, and n is the number of battery strings. In this example, the minimum voltage value among the measured voltages of the battery strings corresponding to all battery strings and the voltage values ​​within the allowable error range thereof can be determined as the target voltages of all battery string branches.

[0058] As an example, determining the target voltage of all battery string branches includes: based on the measured battery string voltages corresponding to all battery strings, determining the average voltage value of the measured battery string voltages corresponding to all battery strings as the target voltage of all battery string branches. For example, after obtaining the measured battery string voltages of all battery strings, the controller selects the average voltage value from the measured battery string voltages of all battery strings to determine as the target voltage, that is, U dcStd =avg[U bat i],U dcStd is the target voltage, U bat i is the measured voltage of the battery string of the ith battery string, and n is the number of battery strings. In this example, the average voltage value of the measured voltages of the battery strings corresponding to all battery strings and the voltage values ​​within the allowable error range thereof can be determined as the target voltages of all battery string branches.

[0059] As an example, determining the target voltage of all battery string branches includes: determining the voltage of a bus connected to the multiple battery string branches as the target voltage of all battery string branches. In this example, the voltage of the bus connected to the multiple battery string branches and the voltage value within the allowable error range thereof can be determined as the target voltage of all battery string branches.

[0060] S13: Based on the target voltage and the measured voltage of the battery string, the current sharing DCDC converter is adjusted so that the output voltage of the battery string branch is the target voltage, thereby realizing voltage sharing control of the battery string.

[0061] In this example, the controller can form a PWM signal for controlling the current sharing DCDC converter connected in series with the battery string according to the target voltage and the actual measured voltage of the battery string of each battery string, and output the PWM signal to the current sharing DCDC converter, and adjust the duty cycle of the current sharing DCDC converter so that the output voltage of the battery string branch is the target voltage, so that before the battery string branches are connected in parallel to the bus, the output voltage of the battery string branch formed by the battery string and the current sharing DCDC converter connected in series therewith follows the target voltage, thereby realizing voltage sharing control before the battery string branches are connected in parallel, which helps to ensure that the purpose of parallel connection without impact current can be achieved when the battery strings are subsequently connected in parallel.

[0062] In one embodiment, step S13, i.e., adjusting the current sharing DCDC converter based on the target voltage and the measured voltage of the battery string so that the output voltage of the battery string branch is the target voltage to achieve voltage sharing control of the battery string, specifically includes the following steps:

[0063] S131: Using the voltage correction value calculation formula corresponding to the target voltage, the target voltage and the measured voltage of each battery string corresponding to each battery string are calculated to obtain the voltage correction value corresponding to the current sharing DCDC converter connected in series with each battery string; the voltage correction value calculation formula is U obj i=U dcStd -U bat i,U obj i is the correction value of the voltage for equalizing, U dcStd is the target voltage, U bat i is the measured voltage of the battery string of the ith battery string.

[0064] Among them, the voltage balancing voltage correction value is the expected voltage of each current balancing DCDC converter that needs to be adjusted before the control battery string branch is connected in parallel to the bus, so as to achieve the output voltage of the battery string branch formed by each current balancing DCDC converter and its series-connected battery string to follow the target voltage, so as to achieve the purpose of voltage balancing control.

[0065] In this example, before the battery string branches are connected in parallel to the bus, the controller uses a preset equalizing voltage correction value calculation formula to calculate the collected target voltage and the actual measured voltage of the battery strings at both ends of each battery string to obtain the equalizing voltage correction value corresponding to the current equalizing DCDC converter connected to each battery string. The equalizing voltage correction value can be understood as the expected voltage that needs to control the current equalizing DCDC converter before the battery string branches are connected in parallel to the bus.

[0066] It can be understood that since there are multiple ways to determine the target voltage of all battery string branches in step S12, the target voltage determined by each method is different. Since the duty cycle of the current-sharing DCDC converter needs to be adjusted based on the equalizing voltage correction value determined by the target voltage and the actual measured voltage of the battery string, it is necessary to use the equalizing voltage correction value calculation formula corresponding to the target voltage acquisition method to calculate the target voltage and the actual measured voltage of the battery string corresponding to each battery string to ensure that the obtained equalizing voltage correction value is more reasonable, thereby ensuring that the subsequent duty cycle adjustment of the current-sharing DCDC converter is more convenient.

[0067] As an example, in the above step S12, the measured voltage U of the n battery strings is bat The maximum voltage value in i is determined as the target voltage U dcStd (i.e. U dcStd =max[U bat i]), the calculation formula of the voltage correction value of the voltage balancing corresponding to the target voltage is U obj i=U dcStd -U bat i, using the above formula to calculate, the voltage correction value U corresponding to the current-sharing DCDC converter connected in series with the i-th battery string can be obtained obj i. Since the target voltage U dcStd is the maximum voltage value. At this time, the voltage correction value U obj i≥0, so that the output voltage of the corresponding battery string branch needs to be boosted to the target voltage by a current sharing DCDC converter.

[0068] As an example, in the above step S12, the measured voltage U of the n battery strings is bat The minimum voltage value in i is determined as the target voltage U dcStd (i.e. U dcStd =min[U bat i]), the calculation formula of the voltage correction value of the voltage balancing corresponding to the target voltage is U obj i=U dcStd -U bat i, using the above formula to calculate, the voltage correction value U corresponding to the current-sharing DCDC converter connected in series with the i-th battery string can be obtained obj i. Since the target voltage UdcStd is the minimum voltage value. At this time, the voltage correction value U obj i≤0, so that a current sharing DCDC converter is required to step down the output voltage of the corresponding battery string branch to the target voltage.

[0069] As an example, in the above step S12, the measured voltage U of the n battery strings is bat The average voltage value in i is determined as the target voltage U dcStd (i.e. U dcStd =avg[U bat i]), the calculation formula of the voltage correction value corresponding to the target voltage is U obj i=U bat i dcStd , by using the above formula, we can obtain the voltage correction value U corresponding to the current sharing DCDC converter connected in series with the i-th battery string. obj i. That is, the voltage correction value of each battery string branch can be calculated based on the actual measured voltage U bat i and target voltage U dcStd The difference between the values ​​of U and U is determined separately, and then the output voltage of the corresponding battery string branch is stepped down or stepped up to the target voltage by using the current sharing DCDC converter. It can be understood that the step-down or step-up here depends on the voltage correction value U obj The positive or negative value of i.

[0070] As an example, in the above step S12, the voltage of the busbar connected to the multiple battery string branches is determined as the target voltage of all battery string branches, and the calculation formula of the voltage correction value corresponding to the target voltage is U obj i=U bat i dcStd , by using the above formula, we can obtain the voltage correction value U corresponding to the current sharing DCDC converter connected in series with the i-th battery string. obj i. That is, the voltage correction value of each battery string branch can be calculated based on the actual measured voltage U bat i and target voltage U dcStd The difference between the values ​​of U and U is determined separately, and then the output voltage of the corresponding battery string branch is stepped down or stepped up to the target voltage by using the current sharing DCDC converter. It can be understood that the step-down or step-up here depends on the voltage correction value U obj The positive or negative value of i.

[0071] In the following embodiments, the measured voltage U of n battery strings is used. bat The maximum voltage value in i is determined as the target voltage for illustration, and the remaining embodiments are similar to the above embodiments and are not further explained in this application.

[0072] For example, in Figure 5In the example shown, the current sharing power supply is first controlled to start, and the constant DC output voltage is U dcHigh ; Collect the measured voltage U of the battery string corresponding to the i-th battery string bat i, where 1≤i≤n, n is the number of battery strings; then, the measured voltage U of the n battery strings can be bat The maximum voltage value in i is determined as the target voltage U dcStd , that is U dcStd =max[U bat i]; Then, according to the target voltage U dcStd And the measured voltage U bat i, determine the voltage correction value U corresponding to the current-sharing DCDC converter connected in series with the i-th battery string obj i, that is U obj i=U dcStd -U bat i; Finally, control the constant voltage start of the low-voltage output side of each non-isolated DCDC converter, that is, according to the voltage correction value U obj i adjusts the duty cycle of the i-th non-isolated DCDC converter so that the total voltage of the non-isolated DCDC converters and their series-connected battery strings in all battery string branches (i.e., the output circuit of the battery string branch) is the target voltage U dcStd , and then control the closing of each switch contactor to achieve parallel connection without impact current.

[0073] For example, in Figure 6 In the example shown, before the battery strings with different initial capacities and internal resistances are connected in parallel, the monitoring module first controls the switch contactors connected in series with the ith battery string to close in sequence, and collects the measured voltage U of the battery string corresponding to the ith battery string. bat i, where 1≤i≤n, n is the number of battery strings; then, the measured voltage U of the n battery strings can be bat The maximum voltage value in i is determined as the target voltage U dcStd , that is U dcStd =max[U bat i]; Then, according to the target voltage U dcStd And the measured voltage U bat i, determine the voltage correction value U corresponding to the current-sharing DCDC converter connected in series with the i-th battery string obj i, that is U obj i=U dcStd -U bat i; Finally, the low voltage output side of each isolated DCDC converter is controlled to start at a constant voltage, that is, according to the voltage correction value U obji adjusts the duty cycle of the i-th isolated DCDC converter so that the total voltage of the isolated DCDC converters and the battery strings connected in series in all battery string branches (i.e., the output voltage of the battery string branches) is the target voltage U dcStd , and then control the closing of each switch contactor to achieve parallel connection without impact current.

[0074] In this embodiment, before the battery strings are connected in parallel to the bus, the collected actual measured voltage of each battery string and the determined target voltage can be used to determine the voltage balancing correction value based on the target voltage and the actual measured voltage of the battery string. The current balancing DCDC converter is controlled to adjust its duty cycle according to the voltage balancing correction value to achieve the purpose of current balancing of the output current of each regulated battery string, reduce the capacity loss of the battery strings due to parallel connection, and avoid energy caused by internal circulation at the end of charging and discharging.

[0075] S132: Based on the voltage balance correction value corresponding to each current balance DCDC converter, the duty cycle of the current balance DCDC converter is adjusted so that the output voltage of the battery string branch is the target voltage, thereby realizing voltage balance control of the battery string.

[0076] In this example, the controller forms a PWM signal based on the voltage balancing correction value corresponding to each current balancing DCDC converter, and outputs the PWM signal to the current balancing DCDC converter, and adjusts the duty cycle of the current balancing DCDC converter so that the output voltage of the current balancing DCDC converter reaches the desired voltage balancing correction value, so as to achieve that before the battery strings are connected in parallel, the output voltage of the battery string branch formed by the battery string and the current balancing DCDC converter connected in series therewith follows the target voltage of the battery string branch, thereby achieving voltage balancing control before the battery strings are connected in parallel, which helps to ensure that the purpose of current parallel connection without impact can be achieved when the battery strings are connected in parallel subsequently.

[0077] like Figure 6 As shown, in the first bridge rectifier circuit on the high voltage input side of the isolated DCDC converter, Q1 and Q3 are complementary turned on, Q2 and Q4 are complementary turned on, and both have a 50% duty cycle; in the second bridge rectifier circuit on the low voltage output side, Q5 and Q7 are complementary turned on, and Q6 and Q8 are complementary turned on, and both have a 50% duty cycle; the boost or buck function can be achieved by changing the angle difference between the modulation signals on the high voltage input side and the low voltage output side to achieve the output current or absorption current function. For example, if you want to set the output voltage on the low voltage output side of the isolated DCDC converter to 0V at the initial moment and gradually increase it to the equalizing voltage correction value U obj i, the initial phase difference Angle_std can be set to 180°, and then the closed-loop PI adjustment determines its angle offset Angle = (U obj i bat i)*(K p_angle +K i_angle / s)+Angle_std,K p_angle K is the preset proportional coefficient for angle offset adjustment. i is a preset integral coefficient for angle offset adjustment, s is the frequency domain, and the angle offset Angle ranges from 90° to 270°, so as to adjust the operation of each driving switch tube in the isolated DCDC converter based on the angle offset Angle. obj i adjusts the duty cycle of the i-th isolated DCDC converter so that the total voltage of the isolated DCDC converters and their series-connected battery strings in all battery string branches (i.e., the output voltage of the battery string branches) is the target voltage U dcStd To ensure that when all switch contactors are controlled to close so that the batteries can be connected in series and parallel to the busbar, there can be no impact current parallel connection.

[0078] S14: Collect the actual measured current of the battery string corresponding to each battery string.

[0079] The actual measured current of the battery string is the current collected in real time from the branch of the battery string.

[0080] When the battery string branches are connected in parallel to the bus, if each current-sharing DCDC converter still uses the target voltage for current-sharing control, it is impossible to ensure the current-sharing output of each battery string branch. The reason is that the total voltage of each battery string branch is exactly the same, but the internal resistance of different battery string branches is different. According to I=U / R, the output current of each battery string branch is inversely proportional to its internal resistance during charging or discharging. Therefore, when all battery string branches are connected in parallel to the bus, current-sharing control is also required to correct the output voltage of each current-sharing DCDC converter, so as to ensure that each battery string branch can achieve current-sharing output during charging or discharging. Therefore, the controller needs to adjust the current-sharing DCDC converter based on the target voltage and the measured voltage of the battery string, so that the output voltage of the battery string branch is the target voltage, and the voltage-sharing control of the battery string is realized, so as to control the battery string to achieve the current-free parallel connection, and the measured current of the battery string corresponding to the battery string collected in real time, so as to use the measured current of the battery string to realize the current-sharing control after the battery string is connected in parallel.

[0081] S15: Determine the target currents of all the battery strings based on the measured currents of the battery strings corresponding to all the battery strings.

[0082] Among them, the target current refers to the expected current that needs to be adjusted by the battery string branch formed by the battery string and the current sharing DCDC converter connected in series therewith. Since the battery string branch includes the battery string and the current sharing DCDC converter connected in series, the target battery can be understood as the expected current of the battery string or the current sharing DCDC converter.

[0083] As an example, step S15, i.e., determining the target current of all battery strings based on the measured current of the battery strings corresponding to all battery strings, includes: based on the measured current of the battery strings corresponding to all battery strings, taking the average current of the measured current of the battery strings corresponding to all battery strings as the target current of all battery strings. For example, the controller may calculate the measured current I of n battery strings bat The average current of i determines the target current I of the i-th battery string obj i, that is

[0084] As an example, step S15, i.e., determining the target current of all battery strings based on the actual measured current of the battery strings corresponding to all battery strings, includes: calculating the charge and discharge proportional coefficient based on the current capacity of the battery strings corresponding to all battery strings and the charge and discharge current limit; determining the target current of all battery strings based on the actual measured current of the battery strings corresponding to all battery strings and the charge and discharge proportional coefficient.

[0085] As an example, during the discharge process of the battery string, the current capacity SOC_i of the battery corresponding to the i-th battery string and the discharge current limit I Discharge Lim_i, calculate the discharge proportional coefficient I Discharge Rate_i, that is Among them, I Discharge Rate_i is the discharge ratio coefficient of the ith battery string, SOC_i is the current capacity of the battery in the ith battery string, I Discharge Lim_i is the discharge current limit of the i-th battery string; then, based on the measured current I of n battery strings bat i and discharge proportional coefficient I Discharge Rate_i, determines the target current I of the i-th battery string obj i, that is

[0086] As an example, during the battery string charging process, the current capacity SOC_i of the battery corresponding to the i-th battery string and the charging current limit I charge Lim_i, calculate the charging ratio coefficient I charge Rate_i, that is Among them, I charge Rate_i is the charging ratio coefficient of the ith battery string, SOC_i is the current capacity of the battery in the ith battery string, I charge Lim_i is the charging current limit of the i-th battery string. Then, based on the measured current I of n battery strings bat i and charging ratio coefficient I charge Rate_i, determines the target current I of the i-th battery string obj i, that is

[0087] S16: Based on the measured currents and target currents of the battery strings corresponding to all the battery strings, the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, thereby achieving current sharing control of the battery string.

[0088] In this example, the controller can form a PWM signal for controlling the current sharing DCDC converter connected in series with the battery string according to the target current and the actual measured current of the battery string corresponding to each battery device, and output the PWM signal to the current sharing DCDC converter, and adjust the duty cycle of the current sharing DCDC converter so that the output current of the battery string branch is the target current, so that after the battery string branch is connected in parallel to the bus, the output current of the battery string branch formed by the battery string and the current sharing DCDC converter connected in series with it follows the target current, that is, the current sharing control is realized after the battery string branches are connected in parallel, which helps to reduce the capacity loss of the battery string caused by parallel connection and avoid energy caused by internal circulation at the end of charging and discharging.

[0089] In one embodiment, based on the measured current and target current of the battery strings corresponding to all the battery strings, the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, thereby realizing the current sharing control of the battery string, including:

[0090] S161: Using the current-sharing voltage correction value calculation formula, calculate the measured current and target current of the battery strings corresponding to all battery strings, and obtain the current-sharing voltage correction value corresponding to the current-sharing DCDC converter connected in series with each battery string; the current-sharing voltage correction value calculation formula is DaltaU obj i=(I bat I obj i)*(K p +K i / s), DaltaU obj i is the current-sharing voltage correction value of the i-th battery string, I bat i is the measured current of the battery string of the ith battery string, I obj i is the target current of the ith battery string, K p is the preset proportionality factor, K i is the preset integral coefficient, and s is the frequency domain.

[0091] The current-sharing voltage correction value is the desired voltage of each current-sharing DCDC converter that needs to be adjusted after the battery strings are connected in parallel, so as to achieve the output current-sharing control purpose of the battery string branch formed by each current-sharing DCDC converter and its series-connected battery string.

[0092] In this example, after obtaining the measured current and target current of the battery strings corresponding to all the battery strings, the controller can call the conversion logic pre-stored for calculating the current sharing voltage correction value based on the measured current and target current of the battery strings, and use the conversion logic to process the measured current and target current of the battery strings to determine the current sharing voltage correction value corresponding to the current sharing DCDC converter connected in series with the battery string, and dynamically adjust the output voltage of the current sharing DCDC converter based on the current sharing voltage correction value to change the total voltage of the entire battery string branch to achieve the purpose of current sharing output of the battery string branch.

[0093] S162: Based on the current sharing voltage correction value corresponding to each current sharing DCDC converter, the duty cycle of the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, thereby achieving current sharing control of the battery string.

[0094] In this example, after obtaining the current-sharing voltage correction value, the controller forms a corresponding PWM signal based on the current-sharing voltage correction value, and adjusts the duty cycle of the current-sharing DCDC converter through the PWM signal to achieve the purpose of controlling the output current of the battery string branch formed by the battery string and the current-sharing DCDC converters connected in series. For example, during the discharge process, the current-sharing DCDC converter on the battery string branch with a larger measured current of the battery string reduces its output voltage, and the current-sharing DCDC converter on the battery string branch with a smaller measured current of the battery string increases its output voltage, so that the output current of the battery string branch is the target current; during the charging process, the current-sharing DCDC converter on the battery string branch with a larger measured current of the battery string increases its output voltage, and the current-sharing DCDC converter on the battery string branch with a smaller measured current of the battery string reduces its output voltage, so that the output current of the battery string branch is the target current.

[0095] As an example, after obtaining the current-sharing voltage correction value corresponding to each current-sharing DCDC converter, the controller needs to adjust the duty cycle of the current-sharing DCDC converter based on the current-sharing voltage correction value and the voltage-sharing correction value corresponding to the current-sharing DCDC converter, so that the output current of the battery string branch is the target current, and the current-sharing control of the battery string is realized. That is, the difference between the current-sharing voltage correction value and the voltage-sharing correction value corresponding to the current-sharing DCDC converter is determined as the current-sharing voltage change value, and then the duty cycle of the current-sharing DCDC converter is adjusted according to the current-sharing voltage change value, so that the output current of the battery string branch is the target current, and the current-sharing control of the battery string is realized.

[0096] For example, in Figure 5 In the example shown, the current-sharing power supply is mainly used to provide or absorb insufficient current or excess current in the battery string branch where each battery string is located, so as to achieve the purpose of current balancing. iAfter closing, that is, after the battery strings are connected in parallel, the measured current I of the battery string corresponding to the i-th battery string is collected bat i, where 1≤i≤n, n is the number of battery strings, which in this example is the number of battery strings connected in parallel to the busbar. Then, calculate the measured current I of n battery strings bat The average current of i determines the target current I of the i-th battery string obj i, that is Alternatively, the corresponding charge and discharge ratio coefficient of the ith battery string is calculated by the current capacity of the battery string and the charge and discharge current limit, and then the target current I of all battery strings is determined based on the measured battery string current and the charge and discharge ratio coefficient corresponding to all battery strings. obj i. Then, according to the actual measured current I bat i and target current I obj i, according to DaltaU obj i=(I bat I obj i)*(K p +K i / s) to determine the current sharing voltage correction value DaltaU of the i-th current sharing DCDC converter obj i. Afterwards, according to the current-sharing voltage correction value DaltaU obj i and equalizing voltage correction value U obj i, determine the current sharing voltage change value U obj i', where, U obj i'=U obj i-DaltaU obj i; Finally, according to the current-sharing voltage change value U obj i' determines the corresponding adjustment drive signal, and controls the current sharing DCDC converter to adjust the duty cycle based on the adjustment drive signal to achieve current sharing control. That is, during the discharge process, the current sharing DCDC converter on the battery string branch with a larger measured current of the battery string reduces its output voltage, and the current sharing DCDC converter on the battery string branch with a smaller measured current of the battery string increases its output voltage so that the output current of the battery string branch is the target current, thereby achieving current sharing control of the battery string; during the charging process, the current sharing DCDC converter on the battery string branch with a larger measured current of the battery string increases its output voltage, and the current sharing DCDC converter on the battery string branch with a smaller measured current of the battery string reduces its output voltage so that the output current of the battery string branch is the target current, thereby achieving current sharing control of the battery string. In this example, the insufficient current in each battery string branch during the discharge process is provided by the current sharing power supply; during the charging process, the excess current in any battery string branch is injected into the current sharing power supply, which requires that the internal resistance of each battery string branch is different and changes dynamically, but by adjusting the duty cycle of each current sharing DCDC converter, each battery string branch can be dynamically adjusted to achieve current sharing control. Figure 6The implementation of the example shown is similar to Figure 5 The implementation process of the examples shown is the same and will not be described in detail here to avoid redundancy.

[0097] In the battery current sharing control method provided in this embodiment, before the battery strings are connected in parallel, based on the measured voltage of the battery string corresponding to each battery string and the target voltage corresponding to all battery strings, the duty cycle of the current sharing DCDC converter is adjusted so that the output voltage of the battery string branch is the target voltage, and the voltage sharing control of the battery string is realized, which can achieve the purpose of non-impact current parallel connection. After the battery strings are connected in parallel, based on the measured current of the battery string corresponding to all battery strings and the target current, the duty cycle of the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, and the current sharing control of the battery string is realized, and the capacity loss of the battery string caused by parallel connection is reduced to improve the battery capacity utilization rate of the battery string, and the energy loss caused by the internal circulation at the end of charging and discharging can be reduced, which helps to ensure the service life of the parallel battery string and the safety of the battery string during charging and discharging.

[0098] In one embodiment, if Figure 2 As shown, that is, before step S14, before collecting the measured current of the battery string corresponding to each battery string, the battery current sharing control method further includes:

[0099] S21: Collect the measured branch voltages corresponding to all battery strings in real time.

[0100] The branch measured voltage corresponding to the battery string branch can be understood as the sum of the battery string measured voltage of the battery string in the battery string branch and the converter measured voltage of the current sharing DCDC converter.

[0101] S22: If the measured voltages of the branches corresponding to all the battery strings are within the allowable error range of the target voltage, all the battery string branches are controlled to be connected in parallel to the busbar.

[0102] In this example, after obtaining the branch measured voltage corresponding to the battery string branch, the controller first determines whether the branch measured voltage corresponding to all battery string branches is within the allowable error range of the target voltage. If the branch measured voltage corresponding to all battery string branches is within the allowable error range of the target voltage, then when all battery string branches are connected in parallel to the bus, the purpose of parallel connection without impact current can be achieved. At this time, the branch measured voltage corresponding to all battery strings within the allowable error range of the target voltage can be understood as a condition for controlling the parallel connection of all battery string branches to the bus, which can ensure that there is no impact of impact current during the parallel connection process.

[0103] In one embodiment, if Figure 3 As shown, after step S22, that is, after controlling all battery string branches to be connected in parallel to the busbar, the battery current sharing control method further includes:

[0104] S31: collecting the current capacity of the battery string corresponding to all the battery string branches in real time, and determining whether the current capacity of the battery string is between the lower capacity limit of the battery string and the upper capacity limit of the battery string.

[0105] The current capacity of the battery string is the battery capacity of the battery string collected in real time. The upper capacity limit of the battery string refers to the maximum capacity of the battery string that can be normally charged or discharged. The lower capacity limit of the battery string refers to the minimum capacity of the battery string that can be normally discharged or discharged.

[0106] S32: If the current capacity of the battery string corresponding to any battery string branch is not between the lower limit capacity of the battery string and the upper limit capacity of the battery string, disconnect the battery string branch from the bus bar, and repeatedly collect the measured voltage of the battery string corresponding to each battery string.

[0107] In this example, after collecting the current capacity of the battery string corresponding to all battery string branches, the controller first determines whether the current capacity of each battery string is between the lower capacity of the battery string and the upper capacity of the battery string. If the current capacity of the battery string is between the lower capacity of the battery string and the upper capacity of the battery string, at this time, it is determined that the battery string branch can be charged or discharged normally without further adjustment. If the current capacity of the battery string is not between the lower capacity of the battery string and the upper capacity of the battery string, at this time, it is determined that the battery string branch cannot be charged or discharged normally. Therefore, it is necessary to disconnect the battery string branch from the bus, that is, control the switch contactor in the battery string branch to disconnect, so that its current sharing DCDC converter is shut down, so as to avoid the battery string branch whose current capacity is not between the lower capacity of the battery string and the upper capacity of the battery string being connected to the bus, affecting the accuracy and reliability of the current sharing adjustment. In this example, after disconnecting the battery string branch from the bus, it is necessary to repeatedly collect the measured voltage of the battery string corresponding to each battery string, that is, repeat step S11.

[0108] The embodiment of the present invention provides a battery current balancing control system. Figure 4 As shown, the battery current sharing control system includes a monitoring module 10 and a plurality of battery string branches arranged in parallel on a busbar, the battery string branch includes a battery string 20 and a current sharing DCDC converter 30 connected to the battery string 20, the monitoring module 10 is connected to the battery string 20 and the current sharing DCDC converter 30, and is used to collect battery string status information of the battery string branch, and adjust the duty cycle of the current sharing DCDC converter 30 based on the battery string status information to achieve current sharing control.

[0109] The battery string branch is a branch connected in parallel on the busbar, and each battery string branch includes a battery string 20 and a current sharing DCDC converter 30 connected in series.

[0110] Among them, the battery string 20 can be a single energy storage battery, or it can be formed by connecting multiple energy storage battery strings 20. The energy storage battery can be a battery that can be repeatedly charged and discharged, such as a lithium iron phosphate battery and a ternary lithium battery. At least two battery strings 20 are arranged in parallel on the bus to form a battery module. In this example, the battery current sharing control system can realize current sharing adjustment of the output current of at least two battery strings 20 in the battery module to avoid some battery strings 20 being in an overcharged state or an over-discharged state for a long time, resulting in inconsistency of at least two battery strings 20 in the battery module, and effectively avoiding the problem of battery degradation.

[0111] Among them, the current balancing DCDC converter 30 is a DCDC converter used to achieve current balancing of the output currents of each battery string 20. It can be understood that the current balancing DCDC converter 30 is a bidirectional DCDC converter, which can both increase the output current of the battery string 20 and reduce the output current of the battery string 20.

[0112] In this example, the current-sharing DCDC converter 30 and the battery string 20 are connected in series to form a battery string branch. If the number of battery strings 20 in the battery module is n, n current-sharing DCDC converters 30 are required to be connected in series with the n battery strings 20 respectively to form n battery string branches. Then, each current-sharing DCDC converter 30 adjusts its own output voltage to ensure the purpose of current-sharing output of the battery strings 20 in each battery string branch during the charging and discharging process.

[0113] Furthermore, each battery string branch also includes a switch contactor 40 for controlling whether the battery string branch is connected to the bus. The switch contactor 40 is a switch connected to the battery string 20 for controlling whether the battery string 20 is connected to the bus. In this example, each current-sharing DCDC converter 30 is connected in series with a battery string 20 and a switch contactor 40 to form a battery string branch, and the switch contactor 40 is arranged on the battery string branch to control whether the battery string branch is connected to the bus.

[0114] Among them, the monitoring module 10 is a module used to implement the monitoring and processing function in the battery current sharing control system. As an example, the monitoring module 10 pre-stores a current sharing control program for implementing the monitoring and processing function. The monitoring module 10 executes the current sharing control program for processing, and controls the current sharing DCDC converter 30 connected in series with the battery string 20 to adjust the duty cycle, so as to adjust the output current of each battery string 20, thereby achieving the purpose of current sharing output.

[0115] As an example, the monitoring module 10 includes a sampling circuit and a controller connected to the sampling circuit. The sampling circuit is connected to the battery string 20 and the current-sharing DCDC converter 30, and is used to collect the battery string status information of the battery string branch where the battery string 20 and the current-sharing DCDC converter 30 are located, and feed the battery string status information back to the controller, and the battery string status information includes but is not limited to the measured voltage of the battery string, the measured current of the battery string, the current capacity of the battery string, the measured voltage of the converter, the measured current of the converter and the bus voltage, etc. The controller is also connected to the current-sharing DCDC converter 30, and is used to perform comprehensive calculation and judgment processing on the battery string status information to form a PWM signal, which can be used to control the current-sharing DCDC converter 30 to adjust its duty cycle and adjust the output current of each battery string 20, so as to achieve the purpose of current-sharing output. In this example, the controller is specifically a digital signal processor, i.e., a DSP.

[0116] by Figure 4Taking the battery module formed by three battery strings 20 connected in parallel as an example, under different factors such as manufacturing process and operating conditions, the internal resistance and capacity of the three battery strings 20 will deviate after a period of time. At this time, if the three battery strings 20 are directly connected in parallel for charging and discharging; due to the different resistances, the output current will be significantly different during the charging and discharging process, and they cannot be fully charged or discharged at the same time, which will cause a large capacity loss; moreover, in the later stage of charging and discharging, due to the rapid increase in internal resistance, but the increase rate of each battery string 20 is different, the charging and discharging current of some battery strings 20 will increase sharply or even exceed the allowable range of the battery, resulting in a shortened service life of the battery string 20, and even safety accidents such as fire. In order to overcome the above-mentioned problems existing in directly connecting at least two battery strings 20 in parallel to the busbar, a current sharing DCDC converter 30 is connected in series to each battery string 20 to form a battery string branch. The monitoring module 10 is connected to the battery string 20 and the current sharing DCDC converter 30. The battery string status information of the battery string branch can be collected, and then the battery string status information is comprehensively calculated and judged to form a PWM signal. The current sharing DCDC converter 30 is controlled to adjust its duty cycle according to the PWM signal to achieve the purpose of regulating the output current of the battery string 20 to achieve current sharing, avoid the problem caused by inconsistent output current of at least two battery strings 20 during the charging and discharging process, improve the battery capacity utilization rate, help to ensure the service life of each battery string 20 in the battery module, and ensure the safety of each battery string 20 during the charging and discharging process. Since each battery string branch is also provided with a switch contactor 40, the switch contactor 40 is connected to the controller and is controlled by the controller, that is, the controller can control the switch contactor 40 on the battery string branch to close or open according to actual conditions, so as to connect the battery string branch where the battery string 20 is located to the bus, and then execute the corresponding current sharing control program, which helps to ensure the service life of each battery string 20 in the battery module and ensure the safety of each battery string 20 during the charging and discharging process.

[0117] In the battery current sharing control system provided in the present embodiment, a battery string branch is formed by connecting the battery string 20 in series with the current sharing DCDC converter 30, and the monitoring module 10 is used to collect the battery string status information of the battery string branch. By processing the battery string status information, the current sharing DCDC converter 30 is controlled to adjust its duty cycle to adjust the output current of the battery string 20, so that the parallel battery string branches can achieve the purpose of current sharing, reduce the capacity loss of the battery string 20 caused by parallel connection, so as to improve the battery capacity utilization rate of each battery string 20, and reduce the energy loss caused by the internal circulation at the end of charging and discharging, which is helpful to ensure the service life of each battery string 20 and ensure the safety of each battery string 20 during the charging and discharging process.

[0118] In one embodiment, in the prior art, current balancing is achieved by setting a non-isolated DCDC converter 31 between the battery string 20 and the bus, that is, multiple battery strings 20 are connected in parallel on one side of the non-isolated DCDC converter 31, and the other side is connected to the bus, and a constant current is output through the non-isolated DCDC converter 31, so that the current of multiple battery strings 20 is balanced. However, this method has the following shortcomings: both sides of the non-isolated DCDC converter 31 are hundreds of volts high voltage, resulting in a high voltage withstand level of the devices on both sides of the DCDC converter, which makes the cost high and easy to damage.

[0119] In order to overcome the shortcomings of the prior art in which the non-isolated DCDC converter 31 is directly connected to the busbar and the battery string 20, as shown in FIG. Figure 5 As shown, the battery current sharing control system also includes a current sharing power supply 50; the current sharing DCDC converter 30 is a non-isolated DCDC converter 31 connected to the current sharing power supply 50; the input end of the non-isolated DCDC converter 31 is connected to the current sharing power supply 50; the output end of the current sharing DCDC converter 30 is connected to the battery string 20 and the bus.

[0120] The first input end of the current-sharing DCDC converter 30 is connected to the current-sharing power supply 50, and the second input end is connected to the current-sharing power supply 50; the first output end of the current-sharing DCDC converter 30 is connected to the battery string 20, and the second output end is connected to the bus; or, the first output end of the current-sharing DCDC converter 30 is connected to the bus, and the second output end is connected to the battery string 20.

[0121] The non-isolated DCDC converter 31 refers to a DCDC converter whose output GND is related to the output GND. The non-isolated DCDC converter 31 can be a boost or buck converter.

[0122] Among them, the current-sharing power supply 50 is a power supply for achieving current balancing. In this example, the current-sharing power supply 50 is connected to the AC power supply through an AC contactor, which is used to receive the AC power input from the AC power grid and convert the AC power into DC power to provide it to the non-isolated DCDC converter 31 and the battery string 20, so that the battery string 20 completes the charging and discharging operation. As an example, the current-sharing power supply 50 can adopt an uncontrolled rectifier source or a bidirectional DC source (ie, ACDC). In this example, the AC side of the current-sharing power supply 50 is connected to the AC power grid, and the DC side is connected to the battery string 20 through a non-isolated DCDC converter 31.

[0123] Specifically, the first input end of the current-sharing DCDC converter 30 is connected to the current-sharing power supply 50, and the second input end is connected to the current-sharing power supply 50; the first output end of the current-sharing DCDC converter 30 is connected to the battery string 20, and the second output end is connected to the bus; or the first output end of the current-sharing DCDC converter 30 is connected to the bus, and the second output end is connected to the battery string 20. Figure 5 As shown, the first input terminal (i.e., the positive input terminal) and the second input terminal (i.e., the negative input terminal) of each non-isolated DCDC converter 31 are connected to the current sharing power supply 50; the first output terminal (i.e., the positive output terminal) is connected to the battery string 20, and the second output terminal (i.e., the negative output terminal) is connected to the busbar, or the first output terminal (i.e., the positive output terminal) is connected to the busbar, and the second output terminal (i.e., the negative output terminal) is connected to the battery string 20. At this time, the two input terminals of the non-isolated DCDC converter 31 are connected to the current sharing power supply 50, which is the high-voltage input side; the two output terminals of the non-isolated DCDC converter 31 are respectively connected to the battery string 20 and the busbar, which is the low-voltage output side. It can be understood that the high-voltage input side of all non-isolated DCDC converters 31 is connected to the current-sharing power supply 50, and the low-voltage output side is connected to the battery string 20. This method can avoid the shortcomings of the non-isolated DCDC converter 31 being connected to the bus and the battery string 20 respectively, and can effectively reduce the voltage at the input and output ends of the non-isolated DCDC converter 31. There is no need to use devices with a higher withstand voltage level, which helps to reduce circuit costs and ensure the service life of the circuit. In this example, a current-sharing power supply 50 is connected to at least two non-isolated DCDC converters 31 to provide the energy required for the current-sharing process, so as to control the non-isolated DCDC converter 31 to achieve current-sharing control; since the input end of the non-isolated DCDC converter 31 is connected to the current-sharing power supply 50 to obtain the energy required for current-sharing, the non-isolated DCDC converter 31 can use devices with a lower withstand voltage level, which is reliable and not easy to damage.

[0124] In one embodiment, if Figure 5 As shown, the non-isolated DCDC converter 31 includes a first resonant inductor L11, a first driving power tube Q11, a second driving power tube Q12, a first reverse diode D11, a second reverse diode D12, a first energy storage capacitor C11 and a second energy storage capacitor 12; the first resonant inductor L11 and the first driving power tube Q11 are arranged in series between the first input end and the first output end; one end of the first energy storage capacitor C11 is connected to the first resonant inductor L11 and the first driving power tube Q11, and the other end is connected to the second input end and the second output end; one end of the second driving power tube Q12 is connected to the first driving power tube Q11 and the first output end, and the other end is connected to the second input end and the second output end; one end of the second energy storage capacitor 12 is connected to the first driving power tube Q11 and the first output end, and the other end is connected to the second input end and the second output end; the first reverse diode D11 is connected in reverse parallel to the first driving power tube Q11; the second reverse diode D12 is connected in reverse parallel to the second driving power tube Q12.

[0125] The first resonant inductor L11 is an inductor disposed in the non-isolated DCDC converter 31 , which can play a resonant role and help improve the efficiency of DCDC conversion.

[0126] Among them, the first driving power tube Q11 and the second driving power tube Q12 are power tubes arranged on the non-isolated DCDC converter 31, and specifically MOSFET and IGBT can be used. In this example, the first driving power tube Q11 and the second driving power tube Q12 are both connected to the monitoring module 10, and are used for complementary conduction under the control of the monitoring module 10; that is, when the first driving power tube Q11 is turned on, the second driving power tube Q12 is turned off, and when the first driving power tube Q11 is turned off, the second driving power tube Q12 is turned on.

[0127] Among them, the first reverse diode D11 and the first driving power tube Q11 are connected in reverse parallel, which means that the first reverse diode D11 is connected in parallel with the first driving power tube Q11, and the current flowing through the first driving power tube Q11 is opposite to the current flowing through the first reverse diode D11, so that when the first driving power tube Q11 is turned off, the first reverse diode D11 can play a freewheeling role. The second reverse diode D12 and the second driving power tube Q12 are connected in reverse parallel, which means that the second reverse diode D12 and the second driving power tube Q12 are connected in parallel, and the current flowing through the second driving power tube Q12 is opposite to the current flowing through the second reverse diode D12, so that when the second driving power tube Q12 is turned off, the second reverse diode D12 can play a freewheeling role.

[0128] The first energy storage capacitor C11 and the second energy storage capacitor 12 are capacitors arranged in the non-isolated DCDC converter 31 and used for storing and releasing electric energy during the charging and discharging process.

[0129] In this example, after the monitoring module 10 collects the battery string status information, it performs comprehensive calculation and judgment processing on the battery string status information to form a current sharing drive signal, and controls the first driving power tube Q11 and the second driving power tube Q12 connected thereto to be turned on or off based on the current sharing drive signal, and adjusts the PWM duty cycle through PI to control the non-isolated DCDC converter 31 to adjust the output current of the corresponding battery string 20 to achieve the purpose of current sharing, avoid the problems caused by the current inconsistency of each battery string 20 during the charging and discharging process, thereby improving the battery capacity utilization rate, helping to ensure the service life of each battery string 20 in the battery module, and ensuring the safety of each battery string 20 during the charging and discharging process. In this example, a current sharing power supply 50 is connected to the non-isolated DCDC converter 31 to provide the energy required for the current sharing process to control the non-isolated DCDC converter 31 to achieve current sharing; since the non-isolated DCDC converter 31 does not need to be connected to the bus to obtain the energy required for current sharing, the non-isolated DCDC converter 31 can use devices with a lower withstand voltage level, that is, devices such as inductors, capacitors and power switch tubes, which helps to reduce device costs and has the advantages of strong reliability and not easy to damage.

[0130] In one embodiment, if Figure 6 As shown, the current sharing DCDC converter 30 is an isolated DCDC converter 32; the input end of the isolated DCDC converter 32 is connected to the battery string 20; and the output end of the isolated DCDC converter 32 is connected to the battery string 20 and the bus.

[0131] The isolated DCDC converter 32 refers to a DCDC converter whose output GND has nothing to do with the input GND. In this example, the first input terminal and the second input terminal of the isolated DCDC converter 32 are both connected to the battery string 20, and the first output terminal and the second output terminal of the isolated DCDC converter 32 are respectively connected to the battery string 20 and the bus bar, so that the battery string 20 is used as the current sharing power supply 50 of the isolated DCDC converter 32, without the need to add an additional current sharing power supply 50, and the isolated DCDC converter 32 is controlled by the monitoring module 10 to adjust the output battery of the battery string 20, so as to achieve the purpose of controlling the current sharing of at least two battery strings 20.

[0132] In this example, the isolated DCDC converter 32 connected to each battery string 20 is connected to the monitoring module 10, and can adjust the output current of each battery string 20 under the control of the current sharing drive signal of the monitoring module 10, so as to achieve the purpose of current sharing of at least two battery strings 20 arranged in parallel, and reduce the capacity loss caused by parallel connection and the energy loss caused by the internal circulation at the end of charging and discharging. Since the two input ends of each isolated DCDC converter 32 are connected to the battery string 20, the energy required for current sharing is provided by the battery string 20, so that the voltage at its input end is small, so that the internal components of the isolated DCDC converter 32 can use devices with lower withstand voltage levels, and there is no need to add an additional current sharing power supply 50, which can significantly reduce costs. Since the battery string 20 is used as the current sharing power supply 50 required for the isolated DCDC converter 32, when any of the input and output ends of the isolated DCDC converter 32 is in an extreme condition of short circuit, it will not cause the other end to operate, thus avoiding the spread of faults and having high reliability.

[0133] In one embodiment, the first input terminal of the isolated DCDC converter 32 is connected to the battery string 20, and the second input terminal is connected to the battery string 20; the first output terminal of the isolated DCDC converter 32 is connected to the battery string 20, and the second output terminal is connected to the bus; or the first output terminal of the isolated DCDC converter 32 is connected to the bus, and the second output terminal is connected to the battery string 20. Figure 6As shown, the isolated DCDC converter 32 includes a high-frequency transformer T21, a second resonant inductor L21, a first bridge rectifier circuit, a second bridge rectifier circuit and a filter capacitor C21; the first bridge rectifier circuit is arranged on the primary side of the high-frequency transformer T21, and is connected to the first input terminal and the second input terminal; the second bridge rectifier circuit is arranged on the secondary side of the high-frequency transformer T21, and is connected to the first output terminal and the second output terminal; the second resonant inductor L21 is arranged between the primary side of the high-frequency transformer T21 and the first bridge rectifier circuit; the filter capacitor C21 is arranged between the first output terminal and the second output terminal, and is connected in parallel with the second bridge rectifier circuit.

[0134] The first bridge rectifier circuit and the second bridge rectifier circuit are bridge rectifier circuits respectively arranged on the primary side and the secondary side of the high-frequency transformer T21. They are bridge structures formed by connecting four diodes, which can convert AC into unidirectional pulsating DC for rectification. The second resonant inductor L21 is an inductor arranged in the isolated DCDC converter 32, which can play a resonant role and help improve the efficiency of DCDC conversion. The filter capacitor C21 is a capacitor arranged in the isolated DCDC converter 32 and can play a filtering role, which is mainly used to filter out the AC component in the unidirectional pulsating DC.

[0135] In this example, the first bridge rectifier circuit and the second bridge rectifier circuit are both connected to the monitoring module 10, and are used to process according to the current sharing drive signal output by the monitoring module 10 to control the closing or disconnection of the first bridge rectifier circuit and each diode in the first bridge rectifier circuit, so as to adjust the duty cycle of the first bridge rectifier circuit and the second bridge rectifier circuit to achieve the boost and buck effects, so as to achieve the purpose of adjusting the output current sharing of each battery string 20. The first bridge rectifier circuit is connected to the high-frequency transformer T21 through the first resonant inductor L11, and the other end is connected to the battery string 20, which is used to rectify the current input to the battery string 20. The second bridge rectifier circuit is connected to the battery string 20 and the bus, and the rectified current can be input to the battery string 20 to adjust the output current of the battery string 20.

[0136] In one embodiment, if Figure 6As shown, the first bridge rectifier circuit includes a first drive switch tube Q21 and a second drive switch tube Q22 connected to the first input end, and a third drive switch tube Q23 and a fourth drive switch tube Q24 connected to the second input end; the first drive switch tube Q21 is connected to the third drive switch tube Q23, and the monitoring module 10 is connected to the first drive switch tube Q21 and the third drive switch tube Q23, and is used to control the first drive switch tube Q21 and the third drive switch tube Q23 to be complementary and turned on; the second drive switch tube Q22 is connected to the fourth drive switch tube Q24, The monitoring module 10 is connected to the second drive switch tube Q22 and the fourth drive switch tube Q24, and is used to control the second drive switch tube Q22 and the fourth drive switch tube Q24 to be complementary and turned on; one end of the primary side of the high-frequency transformer T21 is connected to the first drive switch tube Q21 and the third drive switch tube Q23 through the second resonant inductor L21, and the other end is connected to the second drive switch tube Q22 and the fourth drive switch tube Q24; the second bridge rectifier circuit includes a fifth drive switch tube Q25 and a sixth drive switch tube Q26 connected to the first output end, and a fifth drive switch tube Q25 and a sixth drive switch tube Q26 connected to the second output end. The monitoring module 10 is connected to the fifth drive switch tube Q25 and the seventh drive switch tube Q27, and is used to control the fifth drive switch tube Q25 and the seventh drive switch tube Q27 to be complementary turned on; the sixth drive switch tube Q26 and the eighth drive switch tube Q28 are connected, and the monitoring module 10 is connected to the sixth drive switch tube Q26 and the eighth drive switch tube Q28, and is used to control the sixth drive switch tube Q26 and the eighth drive switch tube Q28 to be complementary turned on. The switch tubes Q28 are complementary turned on; one end of the secondary side of the high-frequency transformer T21 is connected to the fifth drive switch tube Q25 and the seventh drive switch tube Q27, and the other end is connected to the sixth drive switch tube Q26 and the eighth drive switch tube Q28; the first drive switch tube Q21, the second drive switch tube Q22, the third drive switch tube Q23, the fourth drive switch tube Q24, the fifth drive switch tube Q25, the sixth drive switch tube Q26, the seventh drive switch tube Q27 and the eighth drive switch tube Q28 are each connected in parallel with a reverse freewheeling diode and a filter capacitor C21.

[0137] In this example, Q21, Q22, Q23 and Q24 form a first bridge rectifier circuit, which is arranged on the primary side of the high-frequency transformer T21, and is the high-voltage input side of the isolated DCDC converter 32; the monitoring module 10 and Q21, Q22, Q23 and Q24 can control Q21 and Q23 to be complementary and conduction, and control Q22 and Q24 to be complementary and conduction, so that the duty cycle of each driving switch tube on the high-voltage input side of the isolated DCDC converter 32 is 50%. Q25, Q26, Q27 and Q28 form a second bridge rectifier circuit, which is arranged on the secondary side of the high-frequency transformer T21, and is the low-voltage output side of the isolated DCDC converter 32. The monitoring module 10 is connected to Q25, Q26, Q27 and Q28, and is used to control Q25 and Q27 to be complementary and conduction, and control Q26 and Q28 to be complementary and conduction, so that the duty cycle of each driving switch tube on the low-voltage output side of the isolated DCDC converter 32 is 50%. It can be understood that the modulation signals of the driving switch tube on the high-voltage input side and the driving switch tube on the low-voltage output side of the isolated DCDC converter 32 are the same. The boost or buck function can be achieved by adjusting the angle difference between the driving switch tube on the high-voltage input side and the driving switch tube on the low-voltage output side to adjust the output current of the battery string 20 and achieve the purpose of current sharing.

[0138] 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. A battery current sharing control method, applied to a battery current sharing control system, wherein the battery current sharing control system is provided with a plurality of parallel battery string branches, wherein the battery string branches are provided with a battery string and a current sharing DCDC converter connected in series with the battery string, characterized in that: include: Collecting the measured voltage of the battery string corresponding to each of the battery strings; determining the target voltage of all the battery string branches; Based on the target voltage and the measured voltage of the battery string, adjusting the current sharing DCDC converter so that the output voltage of the battery string branch is the target voltage, thereby realizing voltage sharing control of the battery string; After realizing the voltage balancing control of the battery string, the measured current of the battery string corresponding to each of the battery strings is collected; based on the measured current of the battery strings corresponding to all the battery strings, the target current of all the battery strings is determined; based on the measured current of the battery strings corresponding to all the battery strings and the target current, the current balancing DCDC converter is adjusted so that the output current of the battery string branch is the target current, and the current balancing control of the battery string is realized, including: using a current balancing voltage correction value calculation formula to calculate the measured current of the battery strings corresponding to all the battery strings and the target current, and obtain a current balancing voltage correction value corresponding to the current balancing DCDC converter connected in series with each of the battery strings; the current balancing voltage correction value calculation formula is , For the The current-sharing voltage correction value of each battery string, For the The measured current of the battery string of each battery string, For the The target current of each battery string is is the preset scaling factor, is the preset integral coefficient, In the frequency domain; based on the current sharing voltage correction value corresponding to each of the current sharing DCDC converters, the duty cycle of the current sharing DCDC converter is adjusted so that the output current of the battery string branch is the target current, thereby realizing the current sharing control of the battery string.

2. The battery current balancing control method according to claim 1, characterized in that: The determining of the target voltages of all the battery string branches comprises: Based on the measured voltages of the battery strings corresponding to all the battery strings, determining the maximum voltage value among the measured voltages of the battery strings corresponding to all the battery strings as the target voltage of all the battery string branches; Alternatively, based on the actually measured voltages of the battery strings corresponding to all the battery strings, a minimum voltage value among the actually measured voltages of the battery strings corresponding to all the battery strings is determined as the target voltage of all the battery string branches; Alternatively, based on the measured voltages of the battery strings corresponding to all the battery strings, an average voltage value of the measured voltages of the battery strings corresponding to all the battery strings is determined as the target voltage of all the battery string branches; Alternatively, the voltage of a bus connected to the plurality of battery string branches is determined as the target voltage of all the battery string branches.

3. The battery current balancing control method according to claim 1, characterized in that: The adjusting the current sharing DCDC converter based on the target voltage and the measured voltage of the battery string so that the output voltage of the battery string branch is the target voltage to achieve voltage sharing control of the battery string includes: The target voltage and the measured voltage of each battery string corresponding to the battery string are calculated using the voltage-sharing correction value calculation formula corresponding to the target voltage, and the voltage-sharing correction value corresponding to the current-sharing DCDC converter connected in series with each battery string is obtained; wherein the voltage-sharing correction value calculation formula is: , is the correction value of the voltage for equalizing the voltage, is the target voltage, For the The measured voltage of the battery string of each battery string; Based on the voltage balancing correction value corresponding to each current balancing DCDC converter, the duty cycle of the current balancing DCDC converter is adjusted so that the output voltage of the battery string branch is the target voltage, thereby realizing voltage balancing control of the battery string.

4. The battery current balancing control method according to claim 1, characterized in that: Before collecting the actual measured current of the battery string corresponding to each of the battery strings, the battery current sharing control method further includes: Real-time acquisition of measured branch voltages corresponding to all battery strings; If the measured voltages of the branches corresponding to all the battery strings are within the allowable error range of the target voltage, all the battery string branches are controlled to be connected in parallel to the busbar.

5. The battery current balancing control method according to claim 4, characterized in that: After controlling all the battery string branches to be connected in parallel to the bus, the battery current sharing control method further includes: Collecting the current capacity of the battery string corresponding to all the battery string branches in real time, and determining whether the current capacity of the battery string is between the lower capacity limit of the battery string and the upper capacity limit of the battery string; If the current capacity of the battery string corresponding to any of the battery string branches is not between the lower limit capacity of the battery string and the upper limit capacity of the battery string, the connection between the battery string branch and the bus is disconnected, and the acquisition of the measured voltage of the battery string corresponding to each of the battery strings is repeated.

6. The battery current balancing control method according to claim 1, characterized in that: The determining the target currents of all the battery strings based on the measured currents of the battery strings corresponding to all the battery strings comprises: Based on the actual measured currents of the battery strings corresponding to all the battery strings, taking the average current of the actual measured currents of the battery strings corresponding to all the battery strings as the target currents of all the battery strings; Alternatively, the charge and discharge proportionality coefficient is calculated based on the current capacity of the battery strings corresponding to all the battery strings and the charge and discharge current limit; and the target current of all the battery strings is determined based on the actual measured current of the battery strings corresponding to all the battery strings and the charge and discharge proportionality coefficient.

7. A battery current sharing control system, characterized in that: The invention comprises a monitoring module and a plurality of battery string branches arranged in parallel on a bus, wherein the battery string branch comprises a battery string and a current sharing DCDC converter connected to the battery string, and the monitoring module is connected to the battery string and the current sharing DCDC converter, and is used to collect battery string status information of the battery string branch, and execute the battery current sharing control method according to any one of claims 1 to 6 based on the battery string status information.

8. The battery current balancing control system according to claim 7, characterized in that: The battery current sharing control system also includes a current sharing power supply; the current sharing DCDC converter is a non-isolated DCDC converter connected to the current sharing power supply; the input end of the non-isolated DCDC converter is connected to the current sharing power supply; the output end of the current sharing DCDC converter is connected to the battery string and the bus.

9. The battery current balancing control system according to claim 7, characterized in that: The current sharing DCDC converter is an isolated DCDC converter; the input end of the isolated DCDC converter is connected to the battery string; the output end of the isolated DCDC converter is connected to the battery string and the bus.

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