Battery equalization control system and battery equalization control method

Abstract

The invention discloses a battery equalization control system and a battery equalization control method, a series compensator is arranged on each battery cluster branch, the voltage of each battery cluster is accurately compensated by using the dynamic voltage output function of the series compensator, and the voltage equalization among the battery clusters is effectively realized, so that the input condition of a battery system can be quickly met, and the battery equalization control efficiency is improved. The working efficiency of the battery system is improved, and cluster voltage mismatch caused by cluster voltage difference is avoided. Meanwhile, by adjusting the output voltage of the series compensator and inhibiting inter-cluster ring current, current injection caused by cluster voltage difference in a standing state is avoided, system loss and heat generation are reduced, and the service life of the battery is prolonged. Besides, the system power loss is reduced, the efficiency loss and the heat dissipation cost are reduced, a DC / DC converter with high power capacity and wide voltage range does not need to be designed, the system cost is reduced, and the performance, the efficiency and the economical efficiency of the battery energy storage system are integrally improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a battery balancing control system and a battery balancing control method. Background Art

[0002] Battery energy storage systems, with their advantages of high power density, fast response, and easy installation, have experienced rapid development in recent years. In traditional battery energy storage system architectures, multiple battery racks (battery clusters) are directly connected in parallel to the DC side of a DC / AC converter. Due to factors such as manufacturing processes, the capacity, internal resistance, and other internal characteristics of the individual cells within a battery cluster vary. These initial differences become more pronounced after the cells are connected in series and parallel to form racks. Differences in cell capacity and internal resistance can lead to:

[0003] 1. Unbalanced cluster voltages between racks prevent the battery system from quickly meeting commissioning requirements, impacting system efficiency. More seriously, this imbalance in cluster voltages between racks can further lead to cluster voltage mismatch. Cluster voltage mismatch refers to the inconsistency or mismatch in voltage between battery clusters. This mismatch not only exacerbates voltage variations within the battery system but also negatively impacts the overall performance and stability of the battery system.

[0004] 2. Cluster current inconsistency between different racks. If the battery system is in a static state, due to differences in battery capacity and internal resistance, the rack with a higher cluster voltage will flow current into the rack with a lower cluster voltage. Even if the rack internal resistance is small, the system loss and heat generated by the current flowing through the rack internal resistance are not conducive to the long-term operation of the battery system. The resulting inter-cluster circulation will disrupt the battery balance, resulting in shortened battery life or damage.

[0005] Currently, traditional battery balancing systems typically utilize a cluster-by-cluster parallel connection. The DC / DC converter input is connected in parallel to the corresponding rack, and all outputs are connected in parallel to the high-voltage DC bus of the DC / AC converter. By controlling the DC / DC converter's output current, the battery current in the corresponding rack is varied, thereby reducing battery differences and achieving battery balancing. However, this solution inevitably results in an additional level of power loss in the system, leading to significant efficiency losses and high heat dissipation costs. It also fails to effectively address inter-cluster current circulation issues. Furthermore, this architectural setup results in a higher power capacity, input voltage, and output voltage design range for the DC-DC converter, increasing costs.

[0006] Therefore, there is a need to improve the existing technology.

[0007] The above information is presented as background information only to assist with an understanding of the present disclosure and is not a determination or admission that any of the above may be applicable as prior art with respect to the present disclosure. Summary of the Invention

[0008] The present invention provides a battery balancing control system and a battery balancing control method to solve the problems existing in the prior art.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] In a first aspect, the present invention provides a battery balancing control system comprising at least two battery clusters and a series compensator;

[0011] The battery clusters are connected in parallel;

[0012] Each branch where the battery cluster is located is correspondingly provided with a series compensator;

[0013] The high-voltage side port of each series compensator is connected in parallel to the positive and negative terminals of the corresponding battery cluster, and the low-voltage side port is connected in series to the positive terminal of the corresponding series compensator;

[0014] The series compensator is used to dynamically compensate the voltage of the corresponding battery cluster by outputting the voltage to achieve voltage balance between the battery clusters; and is used to suppress circulating current between the battery clusters by adjusting the output voltage.

[0015] Furthermore, in the battery balancing control system, the series compensator is a bidirectional DC / DC converter.

[0016] Furthermore, the battery balancing control system further includes a relay;

[0017] Each of the battery clusters is connected in parallel with the other battery clusters via the corresponding relay.

[0018] Furthermore, the battery balancing control system further includes a bypass switch;

[0019] Each branch where the battery cluster is located is correspondingly provided with a bypass switch;

[0020] The bypass switch is connected in parallel to the low-voltage side port of the corresponding series compensator.

[0021] Furthermore, the battery balancing control system further includes a circuit breaker;

[0022] The high-voltage side port of each series compensator is connected in parallel to the positive and negative terminals of the corresponding battery cluster through the corresponding circuit breaker.

[0023] In a second aspect, the present invention provides a battery balancing control method, which is applied to the battery balancing control system provided in the first aspect. The method includes:

[0024] S1, set the upper limit of the output voltage of the series compensator to U uplimit , the lower limit is U downlimit ;

[0025] S2. After all series compensators are powered on, the voltages of all online battery clusters are obtained.

[0026] S3, will have the maximum voltage U Rack_max The series compensator corresponding to the battery cluster is selected as the master, and the remaining series compensators are slaves;

[0027] S4. Set the host's output voltage reference value U master_ref is the lower limit value U downlimit Or, the host is not started, at this time the host output voltage reference value U master_ref =0V;

[0028] S5. Each slave calculates the maximum voltage U Rack_ma With the voltage U Rack_i The difference U Rack_error ; where i=1, 2, ..., n;

[0029] S6. Set the output voltage reference value U of the slave slave_ref =U Rack_error +U master_ref , and satisfy U slave_ref ≤U uplimit , to dynamically compensate the voltage of the battery cluster corresponding to each slave machine, and achieve voltage balance between the battery clusters.

[0030] Furthermore, in the battery balancing control method, before S2, the method further includes:

[0031] S1.5. Close the circuit breaker corresponding to the high-voltage side port of each series compensator to power on each series compensator.

[0032] Furthermore, in the battery balancing control method, after S6, the method further includes:

[0033] S7, set the current threshold for opening the circulating current suppression control to I ring_start , I ring_start is a positive real number; and the current threshold for closing the circulating current suppression control is set to I ring_close , I ring_close Close to 0 and I ring_close <I ring_start ;

[0034] S8, connecting all battery clusters in parallel;

[0035] S9, each series compensator determines whether the absolute value of the output current of the machine is I out_abs >I ring_start If yes, execute S10, if no, continue to execute S9;

[0036] S10, start circulation suppression control;

[0037] S11, determine whether the output current of this machine is I out >0A; if yes, execute S12, if no, execute S13;

[0038] S12, reduce the output voltage U of this machine out ;

[0039] S13, determine whether the output current of this machine is I out <0A; if yes, execute S14, if no, execute S15;

[0040] S14, increase the output voltage U of this machine out ;

[0041] S15, make the output voltage of this machine U out constant;

[0042] S16, each series compensator determines whether the absolute value of the output current of the machine is I out_abs <I ring_close If yes, execute S17; if no, return to execute S10;

[0043] S17: Turn off the circulation suppression control to achieve circulation suppression between the battery clusters.

[0044] Furthermore, in the battery balancing control method, S8 specifically includes:

[0045] Close the relay corresponding to each battery cluster to connect all battery clusters in parallel.

[0046] Furthermore, in the battery balancing control method, the method further includes:

[0047] S100, detecting whether there is a series compensator fault;

[0048] S200: Close the bypass switch corresponding to the faulty series compensator to bypass the faulty series compensator.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a battery balancing control system and battery balancing control method. By installing a series compensator in each battery cluster branch and utilizing its dynamic output voltage function, it accurately compensates the voltage of each battery cluster, effectively achieving voltage balancing between battery clusters. This helps quickly meet the commissioning requirements of the battery system, improves the operating efficiency of the battery system, and avoids cluster voltage mismatch caused by cluster voltage differences. At the same time, by adjusting the output voltage of the series compensator, inter-cluster circulating current is suppressed, avoiding current injection caused by cluster voltage differences in the static state, reducing system losses and heat generation, and extending battery life. In addition, compared with the traditional one-cluster-one-parallel DC / DC converter solution, the present invention reduces system power loss, efficiency loss, and heat dissipation costs. It also eliminates the need to design a high-power capacity, wide-voltage range DC-DC converter, reducing system costs and overall improving the performance, efficiency, and economy of the battery energy storage system.

[0051] The present invention has other features and advantages that will be apparent from or will be described in detail in the accompanying drawings and the following detailed description incorporated herein, which together serve to explain certain principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0053] Figure 1 This is a schematic structural diagram of a battery balancing control system provided by the first embodiment of the present invention;

[0054] Figure 2 This is a schematic diagram of a universal equivalent model of a two-cluster battery system mentioned in the first embodiment of the present invention;

[0055] Figure 3 This is a schematic diagram of an equivalent model of a battery balancing control system mentioned in the first embodiment of the present invention;

[0056] Figure 4 This is a flow chart of a battery balancing control method provided in the second embodiment of the present invention;

[0057] Figure 5 This is the cluster voltage balancing control logic flow chart mentioned in the second embodiment of the present invention;

[0058] Figure 6This is the circulation hysteresis control logic flow chart mentioned in the second embodiment of the present invention;

[0059] Figure 7 This is the circulating hysteresis control block diagram mentioned in the second embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to explain in detail the possible application scenarios, technical principles, specific solutions that can be implemented, and the purpose and effects of this application, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of this application and are therefore only examples and are not intended to limit the scope of protection of this application.

[0061] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0062] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0063] In the description of this application, the term "and / or" is used to describe a logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and both A and B exist. In addition, the character " / " in this document generally indicates that the objects before and after are in a logical "or" relationship.

[0064] In this application, terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, priority or sequence relationship between these entities or operations.

[0065] Without further limitations, in this application, the words "include", "comprise", "have" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those defined elements, but also other elements not explicitly listed, or elements inherent to such process, method or product.

[0066] In this application, expressions such as "greater than," "less than," and "exceed" are understood to exclude the number itself; expressions such as "above," "below," and "within" are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise specifically limited.

[0067] In the description of the embodiments of the present application, the space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, it should not be understood as a limitation on the embodiments of the present application.

[0068] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms "installed", "connected", "connected", "fixed", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For those skilled in the art of the present application, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0069] Example 1

[0070] In view of the aforementioned deficiencies in the prior art, the applicant, drawing upon years of extensive practical experience and expertise in design and manufacturing in this field, combined with the application of scientific knowledge, has actively engaged in research and innovation, hoping to create a technology that can address these deficiencies. Through continuous research and design, and through repeated trial production and refinement, the present invention has been developed, which possesses truly practical value.

[0071] Please refer to Figure 1 The embodiment of the present invention provides a battery balancing control system, including at least two battery clusters Rack (such as Figure 1 1#Rack, 2#Rack...n#Rack) and series compensator (such as Figure 1 1#DC / DC, 2#DC / DC, ... n#DC / DC as shown);

[0072] The battery clusters are connected in parallel;

[0073] Each branch where the battery cluster is located is correspondingly provided with a series compensator;

[0074] The high-voltage side port H+ / H- of each series compensator is connected in parallel to the positive and negative terminals B+ / B- of the corresponding battery cluster, and the low-voltage side port L+ / L- is connected in series to the positive terminal B+ of the corresponding series compensator;

[0075] The series compensator is used to dynamically compensate the voltage of the corresponding battery cluster by outputting the voltage to achieve voltage balance between the battery clusters; and is used to suppress circulating current between the battery clusters by adjusting the output voltage.

[0076] In this embodiment, the series compensator is a bidirectional DC / DC converter, which can meet the requirements of bidirectional flow and seamless switching of energy.

[0077] like Figure 1 As shown, the battery balancing control system further includes a relay Relay+ / -;

[0078] Each battery cluster is connected in parallel with the other battery clusters via the corresponding relay to form a high-voltage DC bus.

[0079] like Figure 1 As shown, the battery balancing control system further includes a bypass switch S bypass ;

[0080] Each branch where the battery cluster is located is correspondingly provided with a bypass switch;

[0081] The bypass switch is connected in parallel to the low-voltage side port of the corresponding series compensator. The bypass switch has a bypass function so that the corresponding series compensator does not affect the system operation after a fault occurs.

[0082] like Figure 1 As shown, the battery balancing control system further includes a circuit breaker S bat + and S bat -;

[0083] The high-voltage side port of each series compensator is connected in parallel to the positive and negative terminals of the corresponding battery cluster through the corresponding circuit breaker.

[0084] The high-voltage side port of each series compensator draws power by closing the corresponding circuit breaker, and the output voltage of the low-voltage side port of the series compensator is flexibly controlled according to the control set target to meet the battery balancing function, thereby reducing the impact of battery differences to a certain extent.

[0085] In the battery system, the difference in Rack capacity and internal resistance affects the size of the inter-cluster circulation. The battery capacity is related to the open circuit voltage. For the convenience of analysis, the battery internal resistance only considers the DC internal resistance R o The general equivalent model of the two-cluster battery system is as follows: Figure 2 As shown, taking Rack1 as an example, the universal equivalent model in the dotted box simplifies the battery into a controlled voltage source E bat1 And constant internal resistance R o1 Series circuit, E bat1 Equivalent to the open circuit voltage of the battery, I bat1 is the current flowing into the battery. If Rack1 and Rack2 are connected in parallel and are at rest, I bat1 +I bat2 =0; U bat1= E bat1 +I bat1 *R o1 ;U bat2 =E bat2+ I bat2 *R o2 , and U bat1 =U bat2 Assume that R o1 =R o2 , E bat1 >Eb at2 , so I bat1 <0, I bat2 > 0. That is, the current of Rack1 with high open circuit voltage will flow to Rack2 with low open circuit voltage, forming a circular current. Similarly, R o1 ≠R o2 , which will also cause circulation, which will not be analyzed here.

[0086] The series compensator in the proposed battery balancing control system flexibly controls the output voltage U out To compensate for the differences in open-circuit voltage and internal resistance, and to reduce the impact of inter-cluster circulating current.

[0087] Equivalent models such as Figure 3 As shown, we can get:

[0088] E bat1 +I bat1 *R o1 +U out1 =E bat2 +I bat2 *R o2 +U out2 , by controlling U out1 and U out2 The size of each Rack branch current I bat1 , I bat2 Balance. Since the series compensator power design is small, its loss can be ignored compared with the battery system. During the system static circulating current suppression process, the high-voltage side input current I in1 , I in2 It is approximately equal to 0, so it can be ignored in the analysis and does not affect the circulation control effect.

[0089] It should be noted that a series compensator is installed in each battery cluster Rack branch, with its high-voltage side port connected in parallel to the positive and negative terminals of the corresponding Rack, and its low-voltage side port connected in series to the positive terminal of the Rack. Although this series compensator is also a DC / DC converter, because its low-voltage side port is connected in series to the Rack power branch, its power capacity and output voltage design range requirements are reduced, greatly reducing the need for heat dissipation devices and design costs. The series compensator obtains the voltage of each Rack cluster through control sampling and communication, and sets the output voltage reference value of the series compensator based on the voltage difference between clusters. The output voltage of the series compensator can dynamically compensate for the cluster voltage of each Rack, achieving cluster voltage balance and quickly meeting the battery system's commissioning conditions. This improves the battery system's operating efficiency to a certain extent, avoids cluster voltage mismatch caused by cluster voltage differences, and greatly improves the suppression of circulating current by balancing the cluster voltages.

[0090] When the battery system is put into operation and in a static state, all Rack branches are connected in parallel. However, due to sampling control errors, inconsistent battery cell internal resistance and line impedance, cluster voltage balancing control has not yet completely suppressed the inter-cluster circulating current. At this time, this embodiment adopts a circulating current hysteresis control method to further suppress the impact of circulating current on the system. Set the current threshold I to start the circulating current suppression control. ring_start , I ring_startis a positive value; if the series compensator judges the absolute value of the output current I out_abs >I ring_start , then the circulating current suppression control is turned on. If the output current of the series compensator is in the discharging direction (>0A), it means that the voltage of the corresponding Rack branch is too high and the output voltage of the machine needs to be reduced; if the output current of the series compensator is in the charging direction (<0A), it means that the voltage of the corresponding Rack branch is too low and the output voltage of the machine needs to be raised. The series compensator needs to change the current on the Rack branch by changing its own output voltage to achieve the effect of battery balancing; set the current threshold I for turning off the circulating current suppression control ring_close , I ring_close Close to 0 and I ring_close <I ring_start If the output voltage of the series compensator changes so that the absolute value of the output current of this machine I out_abs <I ring_close , the circulating current suppression control can be turned off. At this time, the series compensator maintains the current output voltage constant voltage control, and the inter-cluster circulating current will gradually reach a balanced state, effectively suppressing the impact of the circulating current on the system.

[0091] Although terms such as battery cluster and series compensator are frequently used in this application, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention.

[0092] The embodiments of the present invention have the following beneficial effects:

[0093] 1. Compared with the traditional parallel battery balancing control system architecture, the power capacity and output voltage design range requirements of the series compensator are reduced, greatly reducing the demand for heat dissipation devices and design costs;

[0094] 2. When the battery system is in standby mode, the series compensator can dynamically compensate the cluster voltage of each rack to achieve cluster voltage balance, flexibly meet the battery system's input conditions, improve the battery system's operating efficiency to a certain extent, and avoid cluster voltage mismatch caused by large cluster voltage differences;

[0095] 3. The cluster voltage balancing control function of the series compensator can significantly suppress the inter-cluster circulating current;

[0096] 4. When the battery system is at rest, the circulation hysteresis control can further suppress the circulation and reduce the loss caused by the system circulation.

[0097] Example 2

[0098] Please refer to Figure 4, is a flow chart of a battery balancing control method provided in Example 1 of the present invention, which is applied to the battery balancing control system provided in Example 1 above. The method specifically includes the following steps:

[0099] S1, set the upper limit of the output voltage of the series compensator to U uplimit , the lower limit is U downlimit ;

[0100] S2. After all series compensators are powered on, the voltages of all online battery clusters are obtained.

[0101] S3, will have the maximum voltage U Rack_max The series compensator corresponding to the battery cluster is selected as the master, and the remaining series compensators are slaves;

[0102] S4. Set the host's output voltage reference value U master_ref is the lower limit value U downlimit Or, the host is not started, at this time the host output voltage reference value U master_ref =0V;

[0103] S5. Each slave calculates the maximum voltage U Rack_ma With the voltage U Rack_i The difference U Rack_error ; where i=1, 2, ..., n;

[0104] S6. Set the output voltage reference value U of the slave slave_ref =U Rack_error +U master_ref , and satisfy U slave_ref ≤U uplimit , to dynamically compensate the voltage of the battery cluster corresponding to each slave machine, and achieve voltage balance between the battery clusters.

[0105] In one implementation of this embodiment, before S2, the method further includes:

[0106] S1.5. Close the circuit breaker corresponding to the high-voltage side port of each series compensator to power on each series compensator.

[0107] It should be noted that in actual applications, when the battery system is put into operation, due to factors such as manufacturing process, ambient temperature, and cycle use, there are differences in the internal characteristics of the battery cluster, such as capacity, internal resistance, and self-discharge rate. This difference will cause cluster voltage mismatch. If the voltage difference between each cluster is too large, it will exceed the voltage difference threshold U set by the BMS (Battery Monitoring and Management System) for the battery system to be put into use. error_set, then the battery system cannot be put into operation temporarily, and can only charge and discharge one or several clusters separately to make the maximum voltage difference of each cluster in the system meet the conditions for the battery system to be put into operation, which greatly reduces the working efficiency and flexibility of the battery system.

[0108] If the battery balancing control system architecture provided in the first embodiment is adopted, the cluster voltage of each rack can be dynamically compensated by controlling the output voltage of the series compensator. Figure 5 As shown, it is assumed that the upper and lower limits of the output voltage of the series compensator are U uplimit and U downlimit , each series compensator closes the circuit breaker S bat + and S bat - Power on, after all series compensators are powered on, each series compensator obtains the cluster voltage R of all online Racks through sampling and communication. ack1 、R ack2 ...R ackn , compare and get the maximum value of Rack voltage U Rack_max , select the series compensator corresponding to the Rack with the highest voltage as the master, and the rest as slaves. Set the output voltage reference value U of the master master_ref Set the lower limit value U for the series compensator output voltage downlimit ; Or the host does not start and its Sbypass is closed to bypass state, which is equivalent to U master_ref =0V. The other slaves calculate U according to the cluster voltage information. Rack_max With the USB Rack_i The difference U of (i=1, 2...n) Rack_error , the output voltage reference value U of the slave slave_ref =U Rack_error +U master_ref , then U slave_ref ≤U uplimit The series compensator can be used according to the cluster pressure difference U Rack_error The size automatically compensates for the voltage difference between clusters to make the cluster voltage reach a balanced state. At this time, the series compensator makes up for the battery difference so that the voltage difference between each cluster is less than the voltage difference threshold U set by the BMS for the battery system to be put into use. error_set , quickly meet the conditions for the battery system to be put into operation and solve the cluster voltage mismatch problem.

[0109] In one implementation of this embodiment, after S6, the method further includes:

[0110] S7, set the current threshold for opening the circulating current suppression control to I ring_start , I ring_start is a positive real number; and the current threshold for closing the circulating current suppression control is set to Iring_close , I ring_close Close to 0 and I ring_close <I ring_start ;

[0111] S8, connecting all battery clusters in parallel;

[0112] S9, each series compensator determines whether the absolute value of the output current of the machine is I out_abs >I ring_start If yes, execute S10, if no, continue to execute S9;

[0113] S10, start circulation suppression control;

[0114] S11, determine whether the output current of this machine is I out >0A; if yes, execute S12, if no, execute S13;

[0115] S12, reduce the output voltage U of this machine out ;

[0116] S13, determine whether the output current of this machine is I out <0A; if yes, execute S14, if no, execute S15;

[0117] S14, increase the output voltage U of this machine out ;

[0118] S15, make the output voltage of this machine U out constant;

[0119] S16, each series compensator determines whether the absolute value of the output current of the machine is I out_abs <I ring_close If yes, execute S17; if no, return to execute S10;

[0120] S17: Turn off the circulation suppression control to achieve circulation suppression between the battery clusters.

[0121] In one implementation of this embodiment, the S8 is specifically:

[0122] Close the relay corresponding to each battery cluster to connect all battery clusters in parallel.

[0123] It should be noted that if Figure 6 As shown in the circulating hysteresis control logic flow chart, when the battery system meets the conditions for being put into operation, the relays Relay+ / Relay- on each Rack branch are closed. At this time, the DC / AC is not turned on and the battery system is in a static state. When the Rack is set to discharge, the output current I out>0; When Rack is charging, the output current I out <0. As analyzed above, without a series compensator, cluster voltage mismatch caused by battery differences, cluster voltage imbalance, and inconsistent battery internal resistance can cause circulating currents in each rack branch. The magnitude of this circulating current is related to the inter-cluster voltage difference; the greater the cluster pressure difference, the greater the circulating current. The circulating current flows from the higher-voltage rack to the lower-voltage rack.

[0124] By controlling the output voltage of the series compensator, the circulating current can be effectively suppressed. After the series compensator automatically compensates the cluster voltage of each Rack, the relay Relay+ / Relay- is closed, and the Rack branches are connected in parallel, and the system is in a static state. out The cluster pressure difference U has been compensated Rack_error , the circulating current has been reduced to a great extent, but due to sampling control errors, battery cell internal resistance DCR and inconsistent line impedance, circulating current will still occur when the system is stationary.

[0125] At this time, a circulating current hysteresis control method is adopted to further suppress the influence of circulating current on the system, and the current threshold I of the circulating current suppression control is set. ring_start , I ring_start is a positive real number, we can set I ring_start =1A; if the system is judged to have the output current absolute value of the series compensator I out_abs >I ring_start , then the circulating current suppression control is turned on. If the output current of the series compensator is in the discharging direction, it means that the voltage of the corresponding Rack branch is too high and the output voltage of the machine needs to be reduced. If the output current of the series compensator is in the charging direction, it means that the voltage of the corresponding Rack branch is too low and the output voltage of the machine needs to be raised. Set the current threshold I ring_close , I ring_close Close to 0 and I ring_close <I ring_start If the output voltage of the series compensator changes so that the absolute value of the output current of this machine I out_abs <I ring_close , the circulating current suppression control can be turned off. At this time, the series compensator maintains the current output voltage constant voltage control, and the inter-cluster circulating current will gradually reach a balanced state, effectively suppressing the impact of the circulating current on the system.

[0126] According to the above setting idea, a circulating hysteresis control link is added, and its control block diagram is as follows: Figure 7 As shown. The ideal control target of the series compensator is set to the current of each Rack branch is 0A, that is, the output current of the series compensator is 0A, so the circulating current control reference value I is set ring_ref =0A; the output current I obtained by the hardware sampling circuit of this machineout ;I ring_ref with I out The difference between them is used to obtain the output change △U through the PI controller out , and then added to the initial output voltage U out_0 , using PI controller to dynamically adjust the output voltage U out , making I out Tracking to I without static error ring_ref At this time, the series compensator controls the output current to be around 0A, quickly and effectively suppressing the inter-cluster circulating current.

[0127] In one implementation of this embodiment, the method further includes:

[0128] S100, detecting whether there is a series compensator fault;

[0129] S200: Close the bypass switch corresponding to the faulty series compensator to bypass the faulty series compensator.

[0130] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concepts of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A battery balancing control system, characterized in that: comprising at least two battery clusters and a series compensator; The battery clusters are connected in parallel; Each branch where the battery cluster is located is correspondingly provided with a series compensator; The high-voltage side port of each series compensator is connected in parallel to the positive and negative terminals of the corresponding battery cluster, and the low-voltage side port is connected in series to the positive terminal of the corresponding series compensator; The series compensator is used to dynamically compensate the voltage of the corresponding battery cluster by outputting the voltage to achieve voltage balance between the battery clusters; and is used to suppress circulating current between the battery clusters by adjusting the output voltage.

2. The battery balancing control system according to claim 1, characterized in that: The series compensator is a bidirectional DC / DC converter.

3. The battery balancing control system according to claim 1, characterized in that: Also includes relays; Each of the battery clusters is connected in parallel with the other battery clusters via the corresponding relay.

4. The battery balancing control system according to claim 1, characterized in that: Also includes a bypass switch; Each branch where the battery cluster is located is correspondingly provided with a bypass switch; The bypass switch is connected in parallel to the low-voltage side port of the corresponding series compensator.

5. The battery balancing control system according to claim 1, characterized in that: Also includes circuit breakers; The high-voltage side port of each series compensator is connected in parallel to the positive and negative terminals of the corresponding battery cluster through the corresponding circuit breaker.

6. A battery balancing control method, applied to the battery balancing control system according to any one of claims 1 to 5, characterized in that: The method comprises: S1, set the upper limit of the output voltage of the series compensator to U uplimit , the lower limit is U downlimit ; S2. After all series compensators are powered on, the voltages of all online battery clusters are obtained. S3, will have the maximum voltage U Rack_max The series compensator corresponding to the battery cluster is selected as the master, and the remaining series compensators are slaves; S4. Set the host's output voltage reference value U master_ref is the lower limit value U downlimit Or, the host is not started, at this time the host output voltage reference value U master_ref =0V; S5. Each slave calculates the maximum voltage U Rack_ma With the voltage U Rack_i The difference U Rack_error ; where i=1, 2, ..., n; S6. Set the output voltage reference value U of the slave slave_ref =U Rack_error +U master_ref , and satisfy U slave_ref ≤U uplimit , to dynamically compensate the voltage of the battery cluster corresponding to each slave machine, and achieve voltage balance between the battery clusters.

7. The battery balancing control method according to claim 6, wherein: Before S2, the method further includes: S1.

5. Close the circuit breaker corresponding to the high-voltage side port of each series compensator to power on each series compensator.

8. The battery balancing control method according to claim 6, wherein: After S6, the method further includes: S7, set the current threshold for opening the circulating current suppression control to I ring_start , I ring_start is a positive real number; and the current threshold for closing the circulating current suppression control is set to I ring_close , I ring_close Close to 0 and I ring_close <I ring_start ; S8, connecting all battery clusters in parallel; S9, each series compensator determines whether the absolute value of the output current of the machine is I out_abs >I ring_start If yes, execute S10, if no, continue to execute S9; S10, start circulation suppression control; S11, determine whether the output current of this machine is I out >0A; if yes, execute S12, if no, execute S13; S12, reduce the output voltage U of this machine out ; S13, determine whether the output current of this machine is I out <0A; if yes, execute S14, if no, execute S15; S14, increase the output voltage U of this machine out ; S15, make the output voltage of this machine U out constant; S16, each series compensator determines whether the absolute value of the output current of the machine is I out_abs <I ring_close If yes, execute S17, if no, return to execute S10; S17: Turn off the circulation suppression control to achieve circulation suppression between the battery clusters.

9. The battery balancing control method according to claim 8, wherein: The S8 is specifically: Close the relay corresponding to each battery cluster to connect all battery clusters in parallel.

10. The battery balancing control method according to claim 6, wherein: The method further comprises: S100, detecting whether there is a series compensator fault; S200: Close the bypass switch corresponding to the faulty series compensator to bypass the faulty series compensator.

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