Battery equalization topology circuit, battery equalization method and battery management system

Abstract

The embodiment of the invention provides a battery equalization topology circuit, a battery equalization method and a battery management system. The circuit comprises at least two battery strings, a first equalization topology circuit and a second equalization topology circuit, each battery string comprises at least two batteries, the battery strings are connected through the second equalization topology circuit, and the batteries in the battery strings are connected through the first equalization topology circuit; the first equalization topology circuit is used for adjusting the first battery voltage of each battery until the first battery voltage is within a first preset voltage range; and the second equalization topology circuit is used for adjusting the second battery voltage of each battery string until the second battery voltage is within a second preset voltage range. The battery equalization topology circuit can realize rapid equalization of battery voltage between the batteries and between the battery strings.

Description

Technical Field

[0001] This application relates to the field of electrical technology, and in particular to a battery balancing topology circuit, a battery balancing method, and a battery management system. Background Technology

[0002] The purpose of battery balancing is to keep the voltage deviation of individual cells or the battery pack within the expected range, thereby ensuring that each cell remains in the same state during normal use and avoiding overcharging and over-discharging.

[0003] Existing battery balancing circuits require a large number of switches to achieve balancing between two batteries that are far apart, and are mainly suitable for balancing between short battery strings.

[0004] However, existing battery balancing circuits require a large number of switches to achieve balancing between two batteries that are far apart, resulting in excessively long energy paths, long balancing times, slow balancing speeds, and ultimately poor balancing effects. Summary of the Invention

[0005] This application provides a battery equalization topology circuit, a battery equalization method, and a battery management system to shorten the equalization time of battery voltage between batteries and between battery strings, and to improve the equalization speed.

[0006] In a first aspect, embodiments of this application provide a battery balancing topology circuit, including: at least two battery strings, a first balancing topology circuit, and a second balancing topology circuit. The battery strings include at least two batteries, each battery string is connected through the second balancing topology circuit, and each battery in the battery string is connected through the first balancing topology circuit.

[0007] The first equalization topology circuit is used to adjust the first battery voltage of each battery until the first battery voltage is within a first preset voltage range.

[0008] The second equalization topology circuit is used to adjust the second battery voltage of each battery string until the second battery voltage is within a second preset voltage range.

[0009] Secondly, embodiments of this application provide a battery balancing method, including:

[0010] Obtain the first battery voltage of each battery and the second battery voltage of each battery string.

[0011] Based on the first preset voltage range and the first battery voltage, a target battery is determined from the various batteries;

[0012] Based on the second preset voltage range and the second battery voltage, a target battery string is determined from each of the battery strings;

[0013] The target battery is charged or discharged until the battery voltage of the target battery is within the first preset voltage range;

[0014] The target battery string is charged or discharged until the battery voltage of the target battery string is within the second preset voltage range.

[0015] Thirdly, embodiments of this application provide a battery management system, including the battery balancing topology circuit described above.

[0016] The battery balancing topology circuit, battery balancing method, and battery management system provided in this application embodiment achieve balancing between individual batteries by controlling the first balancing topology circuit, and achieve balancing between individual battery strings by controlling the second balancing topology circuit, thereby solving the problem of voltage imbalance between individual cells during the operation of lithium batteries and improving the battery voltage balancing speed. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] Figure 1 This is a schematic diagram of the existing battery balancing topology;

[0019] Figure 2 A schematic diagram of the battery balancing topology circuit provided in this application;

[0020] Figure 3 This is a schematic diagram of a battery balancing topology circuit provided in another embodiment of this application;

[0021] Figure 4 This is a schematic diagram of the Cuk circuit structure provided in an embodiment of this application;

[0022] Figure 5 A circuit diagram of a transformer converter based on a phase-shifted full-bridge is provided for embodiments of this application;

[0023] Figure 6 This is a schematic diagram of power conversion provided in an embodiment of this application;

[0024] Figure 7 This is a flowchart of a battery balancing control method provided in an embodiment of this application;

[0025] Figure 8 This is a schematic diagram of the circuit control strategy execution flow provided in the embodiments of this application;

[0026] Figure 9 This is a schematic diagram of a battery balancing process provided in another embodiment of this application.

[0027] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0028] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0029] Substation battery rooms typically require a large number of batteries, such as lithium-ion batteries. However, lithium-ion batteries suffer from low individual cell voltage and small capacity. Therefore, to meet the voltage and power requirements of practical scenarios, lithium-ion batteries in the battery room are usually connected in series and parallel. Ideally, each battery has the same terminal voltage. However, due to differences in battery cell parameters (such as initial capacity variation, asymmetrical degradation characteristics, and uneven temperature distribution), achieving a uniform terminal voltage across all batteries becomes very difficult. This difference can lead to potential overcharging and over-discharging problems for some batteries in the battery string. If a battery management system monitors the voltage of each battery, charging or discharging must be stopped when the terminal voltage of the battery with the lowest capacity reaches its limit. While this method can prevent underutilization of the weakest battery, it leads to low utilization of all other batteries and reduces the available energy and lifespan of the battery pack. Therefore, voltage balancing technology has been proposed to solve this mismatch problem and achieve efficient battery utilization. In related technologies, Figure 1 This is a schematic diagram of an existing battery balancing topology, such as... Figure 1As shown, because a large number of switches are required to achieve equalization between two widely spaced batteries, this battery equalization topology is suitable for equalizing short battery strings but not for equalizing long battery strings. Furthermore, the excessively long energy path leads to long equalization times, significant losses, and unnecessary charging or discharging of some batteries, causing the equalization speed and conversion efficiency to decrease with increasing energy flow length. Additionally, the battery equalization topology requires a corresponding control strategy. For example, some control strategies first achieve equalization between individual batteries and then between battery strings, completing the equalization in steps. However, this step-by-step approach prolongs the equalization time and slows down the equalization speed. Moreover, the equalization strategy cannot fully utilize the proposed equalization topology's performance; it requires timely judgment of whether the equalization between battery cells is complete before initiating equalization between battery strings, placing high demands on control and making implementation difficult.

[0030] To address the aforementioned issues, this application provides a battery string and battery-to-battery equalization topology circuit and control strategy, which includes a first equalization topology circuit and a second equalization topology circuit. By controlling the first equalization topology circuit, equalization between individual batteries is achieved, while by controlling the second equalization topology circuit, equalization between battery strings is achieved. This solves the problem of voltage imbalance between individual cells during lithium battery operation, shortens the energy path, and further improves the equalization speed.

[0031] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0032] Figure 2 A schematic diagram of the battery balancing topology circuit provided in this application is shown below. Figure 2 As shown, taking four batteries B1~B4 as an example, the first equalization topology circuit 21 in this battery equalization topology circuit can be a Cuk circuit, and the second equalization topology circuit 22 can be a transformer conversion circuit based on a phase-shift full-bridge. Specifically, the individual batteries in each battery string are connected using Cuk circuits, while the battery strings are connected using transformer conversion circuits based on a phase-shift full-bridge.

[0033] In this embodiment, the Cuk circuit consists of a switching transistor and an inductor. The switching transistor can be a metal-oxide-semiconductor field-effect transistor (MOS-FET). The Cuk circuit achieves battery balance by adjusting the battery voltage of each cell. Specifically, in the process of achieving battery balance control using a control strategy, a first preset voltage range can be set. By changing the energy flow direction between the cells, the first battery voltage of each cell is made to fall within the first preset voltage range, thereby achieving battery balance.

[0034] In this embodiment, the transformer conversion circuit based on the phase-shift full-bridge consists of a transformer, multiple inductors, and MOSFETs. It uses the second battery voltage of each battery string as a balancing strategy indicator, and combines this with the AC active power transmission principle. It employs an open-loop method with a fixed phase angle allocation, changing the phase angle to control the balancing current between battery strings, ultimately achieving balancing between the battery strings and ensuring that the second battery voltage of each battery string is within a second preset voltage range.

[0035] In other embodiments, the number of batteries included in the equalization topology circuit is not limited; in still other embodiments, the equalization topology circuit may also include multiple batteries. For example... Figure 3 This is a schematic diagram of a battery balancing topology circuit provided in another embodiment of this application, as shown below. Figure 3 As shown, it includes m battery strings, and each battery string includes n batteries, where B mn E represents the nth battery in the mth battery string. mn This represents the nth Cuk circuit in the mth battery string.

[0036] In this embodiment, the existing lithium battery balancing topology has multiplexing networks and transformers, which cause the balancing topology to have excessively long balancing time and prevent the batteries from being balanced simultaneously without a suitable control strategy. By using Cuk circuits between batteries and phase-shift full-bridge based transformer circuits between battery strings, the presence of multiplexing network circuits can be avoided, and the transformers in the phase-shift full-bridge based transformer circuits can be used reasonably to improve scalability.

[0037] The Cuk circuit and the transformer conversion circuit based on a phase-shift full-bridge are described in detail below through some embodiments. First, the complete battery equalization topology circuit is divided into two parts: one is the Cuk circuit, and the other is the transformer conversion circuit based on a phase-shift full-bridge. The following assumptions are made about the parameters during the equalization process: (1) The battery voltage is assumed to remain constant during the transient process of equalization. (2) It is assumed that the physical characteristics of the components at corresponding positions in the equalization topology are the same, that is, the characteristics of each switch are the same, and the inductors are the same, L1, L2, ..., Ln are equivalent. (3) All switches and inductors are ideal components. (4) The influence of transformer core saturation on the equalization topology is ignored, and the influence of heat generation on transformer parameters is not considered. The transformer is an ideal transformer.

[0038] For example, Figure 4 This is a schematic diagram of the Cuk circuit structure provided in the embodiments of this application. For ease of analysis, two batteries B1 and B2 are used as an example, and only the energy path between the two batteries is analyzed. Figure 4 As shown, the first equalization topology circuit (i.e., the Cuk circuit) includes a first switch Q1, a second switch Q2, a first inductor L1, a second inductor L2, and a first capacitor C1.

[0039] In this configuration, the source of the first switching transistor Q1 is connected to the drain of the second switching transistor, the negative terminal of the first battery, and the positive terminal of the second battery. The drain of the first switching transistor Q1 is connected to one end of the first inductor L1 and one end of the first capacitor C1. The other end of the first inductor L1 is connected to the positive terminal of the first battery B1. The other end of the first capacitor C1 is connected to the source of the second switching transistor Q2 and one end of the second inductor L2. The other end of the second inductor L2 is connected to the negative terminal of the second battery B2.

[0040] The first switch Q1 and the second switch Q2 can be MOSFETs. The second switch Q2 includes a parasitic element, namely a body diode, which is formed by the PN junction between the drain and the substrate.

[0041] In the above Figure 4 Based on this, in some embodiments, energy balance between batteries can be achieved by controlling the switching transistors in the Cuk circuit to turn them on and off. For example, controlling the first switching transistor Q1 to turn on or off, and controlling the second switching transistor Q2 to turn on or off, can adjust the battery voltage of the first battery B1 and the battery voltage of the second battery B2.

[0042] Specifically, we will use two control modes as examples to illustrate this, referring to the above. Figure 4 Assuming the first mode is that the first switch Q1 is on and the second switch Q2 is off, and the second mode is that the first switch Q1 is off and the body diode of the second switch Q2 is on, then in the first mode, the battery voltages of battery B1 and battery B2 can be calculated using the following formula:

[0043]

[0044]

[0045] In the above formula, Vb1 is the battery voltage of battery B1, Vb2 is the battery voltage of battery B2, L1 is the first inductance value, L2 is the second inductance value, t is time, and i L1 i is the current value flowing through the first inductor L1. L2 Vc1 is the current flowing through the second inductor L2, and Vc1 is the voltage across the first capacitor C1.

[0046] In the second mode, both the first switch Q1 and the switch Q5 can be turned off, and the body diode of the second switch Q2 is turned on. The battery voltages of batteries B1 and B2 can be expressed as follows:

[0047]

[0048]

[0049] Furthermore, based on the volt-second characteristics of L1 and L2, the following equation can be derived:

[0050]

[0051] Furthermore, the average value of the inductor current can be expressed as:

[0052]

[0053] In the above formula, D is the duty cycle and Ts is the period.

[0054] By introducing the working principle of the Cuk circuit, the battery voltage can be calculated in real time using the above formula, thereby achieving battery voltage regulation. The equalization strategy control of the Cuk circuit is described below:

[0055] First, group all batteries and determine the standard voltage range after equalization. When grouping batteries, the following rules can be used as a reference: batteries that need to discharge are in group A; batteries that need to charge are in group B; and batteries that neither charge nor discharge are in group C.

[0056] Secondly, the groups can be used to identify the batteries that need equalization. First, the voltage of multiple batteries is measured to determine the average voltage V. avg The battery voltage is at an average voltage V avg Nearby ±V diff Within the voltage tolerance range, the battery is considered to be within an acceptable voltage range (i.e., within the standard voltage range after equalization). Wherein, V diffIt can be predetermined according to the application. In addition, the equalized standard voltage range can be defined as follows:

[0057] V upper =V avg +V diff

[0058] V lower =V avg -V diff

[0059] In the above formula, V upper V is the upper limit of voltage. lower This is the lower limit of the voltage.

[0060] Furthermore, the battery voltage V can be considered. bk The batteries are grouped according to the following criteria:

[0061] V bk >V upper

[0062] V bk <V lower

[0063] After equalization, the battery voltage should be within the standard voltage range. .

[0064] Finally, after determining the standard voltage range, a pulse width modulation (PWM) signal with a fixed frequency and fixed duty cycle can be used to drive the switching transistor, controlling the Cuk circuit to switch from the first mode to the second mode, or from the second mode to the first mode, to adjust the battery voltage of the first battery (e.g., increase or decrease the battery voltage) and the battery voltage of the second battery (e.g., decrease or increase the battery voltage). Once the battery voltage is within the standard voltage range, the driving of the switching transistor is stopped, i.e., the switching transistor is turned off, completing the battery balancing.

[0065] In this embodiment, by using a Cuk circuit that does not have a multiplexing network circuit and configuring a suitable control strategy, the balancing between individual batteries can be achieved, the balancing speed between batteries can be improved, and excessively long energy paths can be avoided, thus reducing energy loss.

[0066] Figure 5 The transformer conversion circuit structure diagram based on phase-shifted full-bridge provided in this application is for ease of analysis, as shown below. Figure 5As shown, taking the first battery string B3 and the second battery string B4 as examples, the energy path between the two battery strings is analyzed. The second equalization topology circuit includes a transformer T1, a third inductor L3 and a fourth inductor L4, a third switch Q7, a fourth switch Q8, a fifth switch Q9, a sixth switch Q10, a seventh switch Q11, an eighth switch Q12, a ninth switch Q13, and a tenth switch Q14.

[0067] The positive terminal of the first battery string B3 is connected to the drain of the third switch Q7 and the drain of the fourth switch Q8, and the negative terminal of the first battery string B3 is connected to the positive terminal of the second battery string B4, the source of the fifth switch Q9, the source of the sixth switch Q10, the drain of the seventh switch Q11 and the drain of the eighth switch Q12.

[0068] The positive terminal of the second battery string B4 is connected to the source of the fifth switch Q9, the source of the sixth switch Q10, the drain of the seventh switch Q11, and the drain of the eighth switch Q12. The negative terminal of the second battery string B4 is connected to the source of the ninth switch Q13 and the source of the tenth switch Q14.

[0069] The first input terminal of transformer T1 is connected to the source of the third switch Q7, the first output terminal of transformer T1 is connected to one end of the third inductor L3, and the other end of the third inductor L3 is connected to the source of the fourth switch Q8 and the drain of the sixth switch Q10.

[0070] The second input terminal of transformer T1 is connected to the source of the fifth switch Q9 and the drain of the ninth switch Q13. The second output terminal of transformer T1 is connected to one end of the fourth inductor L4, and the other end of the fourth inductor L4 is connected to the source of the eighth switch Q12 and the drain of the tenth switch Q14.

[0071] In this embodiment, the aforementioned switching transistor can be a MOSFET.

[0072] In this embodiment, the second topology equalization circuit (i.e. Figure 5 The transformer conversion circuit based on phase-shift full-bridge in the paper applies the principle of AC active power transmission, combines the isolation equalization topology with the full-bridge rectifier / inverter topology, and flexibly controls the energy transmission between power sources by changing the driving signal of the switching transistor in the full-bridge and changing the phase angle of the driving signal, so as to achieve energy balance between the batteries.

[0073] Because the batteries are connected in series, each battery has a different negative electrode potential. Therefore, it is necessary to consider canceling out the negative electrode potentials. For example, Figure 6 This is a schematic diagram of power conversion provided in an embodiment of this application, such as... Figure 6As shown, this transformer conversion circuit based on phase-shift full-bridge utilizes the characteristics of a transformer to cancel the negative potential of the battery. Therefore, the circuit only needs to use an inductor and does not require components such as capacitors to convert DC power into AC power.

[0074] In this embodiment, the full-bridge inverter connected to the two battery strings has the following modulation signal:

[0075]

[0076] In the above formula, W0 is the fundamental angular frequency, m is the modulation index, θ1 and θ2 are the phase angles, and d1 and d2 are the modulation signals.

[0077] After passing through the full-bridge converter, the equivalent AC power supply voltages U1 and U2 of battery strings B3 and B4 are as follows:

[0078]

[0079] In the above formula, V B1 The voltage at battery string B3 is V. B2 The voltage at battery string B4 is given. The direction and magnitude of the power flow between these two power sources can be controlled by the phase angle. The equivalent inductor current L flows through it. eq for:

[0080]

[0081] In the above formula, since The direction and magnitude of the current are related to the phase angle. Therefore, the influence of the battery voltage difference on the balancing current in the traditional balancing topology is transformed into the influence of the phase angle difference. The power of the battery string and the balancing current of the battery string are further obtained through the inductor current.

[0082]

[0083] In the above formula, P 12 For the power of the battery string, I B1 This is the balancing current for the battery string.

[0084] As can be seen from the above formula, when the basic topology parameters are determined, the direction and magnitude of energy transmission can be achieved by controlling the value of (θ1-θ2). Furthermore, by assigning a leading phase angle to the high-voltage battery and a lagging phase angle to the low-voltage battery in the balanced topology of the two battery strings, the current flow and magnitude of the battery strings can be controlled.

[0085] In some implementations, the current flow direction and / or magnitude of the first battery string can be controlled by a modulation signal, and the current flow direction and / or magnitude of the second battery string can be controlled according to the modulation signal, thereby achieving balance between the two battery strings. Specifically, the control strategy of the transformer switching circuit is as follows:

[0086] First, based on the principle analysis above, we can clearly conclude that changing the phase angle of the modulation signal alters the current in the branch containing the battery string, thus determining whether the battery string is in a charging or discharging state, thereby achieving energy exchange between battery strings. Based on this, all battery strings can be grouped, and the balancing criteria can be determined. For example, a battery string that needs discharging is assigned to group A, a battery string that needs charging is assigned to group B, or a battery string that neither charges nor discharges is assigned to group C. This allows us to determine which battery strings require balancing.

[0087] Secondly, the phase angle of the grouped battery strings requiring balancing is assigned. All battery strings are divided into three groups: A, B, and C. Group A consists of all battery strings that need to be discharged, Group B contains all battery strings that need to be charged, and the remaining battery strings belong to Group C, which does not require charging or discharging. The battery strings in Group C can be protected from interference from the voltage equalizer circuit by shutting down the full-bridge converter containing these battery strings.

[0088] Then, after a period of equalization, the battery string voltage needs to be reassessed. In group A, after a period of charging, the battery string voltage rises, and it is reassessed whether the battery string voltage meets the equalization requirements (i.e., whether it is within the standard voltage range after equalization). If not, the MOSFET needs to be driven to continue charging according to the previous drive signal. If it meets the requirements, the group and phase angle need to be reallocated. In group B, after a period of discharging, the battery voltage drops, and it is reassessed whether the battery string voltage meets the requirements (i.e., whether it is within the standard voltage range after equalization). If not, the MOSFET needs to be driven to continue charging as before. If it meets the requirements, the group and phase angle need to be reallocated. When the battery string meets the requirements, the MOSFET of the full-bridge converter containing the battery cell is turned off.

[0089] In the embodiments of this application, since there is no multiplexing network circuit in the second equalization topology circuit, and the topology's extensibility and scalability are enhanced by the reasonable use of transformers, the battery equalization time can be reduced and the equalization speed can be improved by combining appropriate control strategies.

[0090] The entire battery equalization control process is described in detail below through some examples. Figure 7 This is a flowchart of the battery balancing control method provided in the embodiments of this application, such as... Figure 7 As shown, it includes the following steps:

[0091] Step S710: Obtain the first battery voltage of each battery and the second battery voltage of each battery string.

[0092] Step S720: Determine the target battery from each battery according to the first preset voltage range and the first battery voltage.

[0093] Step S730: Determine the target battery string from each battery string according to the second preset voltage range and the second battery voltage.

[0094] Step S740: Charge or discharge the target battery until the battery voltage of the target battery is within the first preset voltage range.

[0095] Step S750: Charge or discharge the target battery string until the battery voltage of the target battery string is within the second preset voltage range.

[0096] In some implementations, if the first battery voltage is less than the lower limit of the first preset voltage range, the battery is determined to be the target battery to be charged; if the first battery voltage is greater than the upper limit of the first preset voltage range, the battery is determined to be the target battery to be discharged.

[0097] In some implementations, if the second battery voltage is less than the lower limit of the second preset voltage range, the battery string is determined to be the target battery string to be charged; if the second battery voltage is greater than the upper limit of the second preset voltage range, the battery string is determined to be the target battery string to be discharged.

[0098] Figure 8 This is a schematic diagram of the circuit control strategy execution flow provided in the embodiments of this application, such as... Figure 8 As shown, it includes battery equalization control steps S801 to S806, and battery string equalization control steps S808 to S815, as detailed below:

[0099] Step S801: Read the battery voltage;

[0100] Step S802: Grouping batteries and battery strings, and assigning phase angles;

[0101] Step S803: Calculate the first average voltage value Vavg and the first standard voltage range. Wherein, the first standard voltage range is: V upper V is the upper limit of voltage. lower V is the lower limit of voltage. diff It can be predetermined according to the application.

[0102] Step S804: Is the battery voltage within the first standard voltage range?

[0103] Step S805: If the voltage is within the first standard voltage range, turn off the switch of the first equalization topology circuit to stop the equalization between batteries.

[0104] Step S806: If the voltage is not within the first standard voltage range, a period of equalization is required.

[0105] Step S807: Determine whether all balancing has been completed, specifically including whether balancing between batteries and between battery strings has been completed.

[0106] Step S808: Calculate the phase angle, the second average voltage value, and the second standard voltage range. Where θ1 and θ2 are the phase angles, Vavg' is the second average voltage value, and V... upper 'V' represents the upper limit of the voltage range within the second standard voltage range. lower 'This is the lower limit of the voltage in the second standard voltage range.

[0107] Step S809: Is the battery voltage of the battery string greater than the upper limit of the second standard voltage range?

[0108] If the battery voltage in step S810 is greater than the upper limit of the second standard voltage range, then a period of equalization is required.

[0109] Step S811: Is the battery voltage of the battery string less than or equal to the lower limit of the second standard voltage range?

[0110] Step S812: Check whether the battery voltage of the battery string is less than the lower limit of the second standard voltage range.

[0111] If the battery voltage in the battery string is less than the lower limit of the second standard voltage range in step S813, then a period of equalization is required.

[0112] Step S814: Is the battery voltage of the battery string greater than or equal to the upper limit of the second standard voltage range?

[0113] Step S815: Shut down the full bridge to stop balancing between battery strings.

[0114] Furthermore, Figure 9 This is a schematic diagram of a battery balancing process provided in another embodiment of this application, such as... Figure 9 As shown, it includes the following steps:

[0115] Step S901: Group the batteries in each battery string and the individual battery strings separately, and determine the range of the equalized battery voltage based on the measured voltage.

[0116] Step S902: Perform phase angle allocation on the battery strings that need to be balanced and drive the full bridge;

[0117] Step S903: After a period of equalization, the battery voltage is reassessed, and the batteries are regrouped and their phase angles are reassigned.

[0118] Step S904: After the battery string balancing is completed, turn off all the MOSFETs of the full bridge.

[0119] Step S905: Directly drive the MOSFET containing the battery that needs to be balanced;

[0120] Step S906: After a period of equalization, determine whether the battery voltage meets the requirements;

[0121] Step S907: Battery balancing is completed within the battery string; turn off the MOSFET.

[0122] Step S908: Confirm that equalization is complete and prohibit the generation of drive signals.

[0123] In this embodiment, firstly, after measuring the voltage of all batteries, each battery string is grouped, and the batteries within each individual battery string are also grouped, determining the range of battery voltages after equalization. Then, different circuits are controlled separately. For the Cuk circuit, the MOSFET of the battery requiring equalization is directly driven. After a period of time, it is determined whether the battery voltage meets the requirements. If it does, the MOSFET of the Cuk circuit is directly turned off. For the full-bridge circuit, the battery strings requiring equalization are phase-angled, and the MOSFETs are driven. After a period of equalization, the battery voltage is reassessed, and the strings are regrouped and phase-angled. If, after a period of equalization, the voltage of the battery string is within the determined range, the requirements are met, and the MOSFET is turned off. When all the MOSFETs in the full-bridge circuit are turned off, the equalization between battery strings is complete. Finally, the battery voltage is checked to ensure that all MOSFETs are turned off and equalization is complete.

[0124] The method provided in the above embodiments can be applied to battery balancing topology circuits. In this embodiment, the battery balancing topology circuit is controlled by the above method, increasing the battery balancing methods and improving the topology's scalability while mitigating the long balancing time. Furthermore, existing lithium battery balancing topologies contain multiplexing networks, transformers, and other circuits. This leads to long balancing times for lithium batteries if a suitable control strategy is not implemented, and individual batteries cannot be balanced simultaneously. Moreover, the scalability of the balancing topology circuit is very low, failing to achieve multi-cell string balancing. The balancing topology circuit provided in this embodiment does not contain multiplexing network circuits and makes reasonable use of transformers, resulting in strong scalability.

[0125] This application also provides a battery management system, including the battery balancing topology circuit described above.

[0126] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0127] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A battery balancing topology circuit, characterized in that, include: At least two battery strings, a first equalization topology circuit and a second equalization topology circuit, wherein each battery string includes at least two batteries, each battery string is connected through the second equalization topology circuit, and each battery in the battery string is connected through the first equalization topology circuit. The first equalization topology circuit is used to adjust the first battery voltage of each battery until the first battery voltage is within a first preset voltage range. The second equalization topology circuit is used to adjust the second battery voltage of each battery string until the second battery voltage is within a second preset voltage range.

2. The circuit according to claim 1, characterized in that, The first equalization topology circuit includes: a first switching transistor, a second switching transistor, a first inductor, a second inductor, and a first capacitor; The source of the first switching transistor is connected to the drain of the second switching transistor, the negative terminal of the first battery, and the positive terminal of the second battery. The drain of the first switching transistor is connected to one end of the first inductor and one end of the first capacitor. The other end of the first inductor is connected to the positive terminal of the first battery. The other end of the first capacitor is connected to the source of the second switching transistor and one end of the second inductor. The other end of the second inductor is connected to the negative terminal of the second battery.

3. The circuit according to claim 2, characterized in that, The first equalization topology circuit is specifically used for: Controlling the first switch to turn on or off, and controlling the second switch to turn on or off, to adjust the battery voltage of the first battery and the battery voltage of the second battery.

4. The circuit according to claim 3, characterized in that, When the first equalization topology circuit switches from the first mode to the second mode, the battery voltage of the first battery increases and the battery voltage of the second battery decreases. When the first equalization topology circuit switches from the second mode to the first mode, the battery voltage of the first battery decreases and the battery voltage of the second battery increases. In the first mode, the first switch is turned on and the second switch is turned off; in the second mode, the first switch is turned off and the body diode of the second switch is turned on.

5. The circuit according to claim 1, characterized in that, The second equalization topology circuit includes: a transformer, a third inductor, a fourth inductor, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch, and a tenth switch; The positive terminal of the first battery string is connected to the drain of the third switch and the drain of the fourth switch, and the negative terminal of the first battery string is connected to the positive terminal of the second battery string, the source of the fifth switch, the source of the sixth switch, the drain of the seventh switch and the drain of the eighth switch. The positive terminal of the second battery string is connected to the source of the fifth switch, the source of the sixth switch, the drain of the seventh switch and the drain of the eighth switch, and the negative terminal of the second battery string is connected to the source of the ninth switch and the source of the tenth switch. The first input terminal of the transformer is connected to the source of the third switching transistor, the first output terminal of the transformer is connected to one end of the third inductor, and the other end of the third inductor is connected to the source of the fourth switching transistor and the drain of the sixth switching transistor. The second input terminal of the transformer is connected to the source of the fifth switching transistor and the drain of the ninth switching transistor. The second output terminal of the transformer is connected to one end of the fourth inductor, and the other end of the fourth inductor is connected to the source of the eighth switching transistor and the drain of the tenth switching transistor.

6. The circuit according to claim 5, characterized in that, The second equalization topology circuit is specifically used to receive the modulation signal and control the current direction and / or current magnitude of the first battery string according to the modulation signal, and to control the current direction and / or current magnitude of the second battery string according to the modulation signal.

7. A battery balancing method, characterized in that, The method, applied to the battery balancing topology circuit according to any one of claims 1-6, comprises: Obtain the first battery voltage of each battery and the second battery voltage of each battery string; Based on the first preset voltage range and the first battery voltage, a target battery is determined from the various batteries; Based on the second preset voltage range and the second battery voltage, a target battery string is determined from each of the battery strings; The target battery is charged or discharged until the battery voltage of the target battery is within the first preset voltage range; The target battery string is charged or discharged until the battery voltage of the target battery string is within the second preset voltage range.

8. The method according to claim 7, characterized in that, The step of determining the target battery from the various batteries based on the first preset voltage range and the first battery voltage includes: If the voltage of the first battery is less than the lower limit of the first preset voltage range, the battery is determined to be the target battery to be charged. If the voltage of the first battery is greater than the upper limit of the first preset voltage range, the battery is determined to be the target battery to be discharged.

9. The method according to claim 7, characterized in that, The step of determining the target battery string from the various battery strings based on the second preset voltage range and the second battery voltage includes: If the voltage of the second battery is less than the lower limit of the second preset voltage range, the battery string is determined to be the target battery string to be charged. If the voltage of the second battery is greater than the upper limit of the second preset voltage range, the battery string is determined to be the target battery string to be discharged.

10. A battery management system, characterized in that, The battery balancing topology circuit includes any one of claims 1-6.

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