A daisy chain topology based parallel battery pack equalization circuit and equalization system

Abstract

The application provides a daisy chain topology-based parallel battery pack equalization circuit and equalization system. The equalization circuit comprises an equalization branch and N battery branches, and N is an integer greater than 1. Each battery branch in the N battery branches comprises an equivalent resistor and a battery pack, and the N battery branches are connected in parallel. The equalization branch comprises a DCDC module and N switch modules. The N switch modules correspond to the N battery branches one by one. The first end of each switch module in the N switch modules is connected to the second end of the DCDC module, the second end of each switch module in the N switch modules is connected to the middle end of the corresponding battery branch, and the first end of the DCDC module is connected to the total positive end. The N switch modules are configured to work based on a switch signal, and the DCDC module is configured to work based on a control signal to equalize the working current of the N battery branches. The equalization circuit realizes current equalization by cooperating with the multi-way switch through the shared DCDC module and reduces the cost by multiplexing the DCDC module.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of electronic circuit, in particular to a parallel battery pack equalization circuit and equalization system based on daisy chain topology. BACKGROUND

[0002] In energy storage products, due to cost and space constraints, the inverter host is usually not equipped with a battery or only equipped with a small-capacity battery pack, and relies on an external battery pack for expansion, and a daisy chain connection is usually used to reduce costs.

[0003] However, in the connection mode of the daisy chain connection, the distance from each parallel battery pack to the inverter is different, and the direct current resistance of each parallel battery pack is different, resulting in uneven charging and discharging current of each battery pack. As a result, some problems will occur. First, the charging and discharging rates of each battery pack are different, the SOC drops at different speeds, the SOCs of multiple parallel battery packs are inconsistent, and the customer experience is affected. Second, when each battery pack is discharging, the battery pack close to the load is discharged first, and the discharging current of the remaining battery pack increases continuously, which may trigger protection when the maximum discharging current is exceeded, and the large current causes the wire to heat seriously, which poses a safety hazard. Third, due to the different SOCs of each battery pack, when the load stops discharging, circulating current will be generated, which threatens the stable operation of the system. SUMMARY

[0004] The embodiment of the present application provides a parallel battery pack equalization circuit and equalization system based on daisy chain topology, which can equalize the working current of multiple battery packs connected in a daisy chain to improve the stability of the working of each battery pack, and reduce the cost by reusing the DCDC module.

[0005] In a first aspect, the embodiments of the present application provide a parallel battery pack equalization circuit based on a daisy chain topology, which comprises: N battery branches, N being an integer greater than 1; each of the N battery branches comprises an equivalent resistor and a battery pack, a first end of the equivalent resistor is a first end of the battery branch, a second end of the equivalent resistor and a first end of the battery pack are connected to a point and are a middle end of the battery branch, and a second end of the battery pack is a second end of the battery branch; wherein the N battery branches are connected in parallel, a first end of a next-level battery branch is connected to a middle end of a previous-level battery branch, a first end of an uppermost-level battery branch is a total positive end, and a second end of each of the N battery branches is connected to a total negative end; an equalization branch, which comprises a DCDC module and N switch modules; the N switch modules correspond to the N battery branches one by one, a first end of each of the N switch modules is connected to a second end of the DCDC module, a second end of each of the N switch modules is connected to the middle end of the battery branch corresponding thereto, and a first end of the DCDC module is connected to the total positive end; wherein the N switch modules are configured to work based on a switch signal, and the DCDC module is configured to work based on a control signal to equalize working currents of the N battery branches.

[0006] In some embodiments, the parallel battery pack equalization circuit based on the daisy chain topology further comprises: a current collection module connected to the total positive end, the total negative end, and the N battery branches respectively, the current collection module being configured to collect total current data between the total positive end and the total negative end and N branch current data corresponding to the N battery branches in real time; and a control module connected to the current collection module, the DCDC module, and the N switch modules respectively, the control module being configured to output the switch signal and the control signal based on the total current data and the N branch current data to control working states of the DCDC module and the N switch modules, so as to equalize the working currents of the N battery branches.

[0007] In some embodiments, the parallel battery pack equalization circuit based on the daisy chain topology further comprises: an SOC collection module connected to the N battery branches respectively, the SOC collection module being configured to collect N SOC data corresponding to the N battery branches in real time; and the control module connected to the SOC collection module, the control module being further configured to output the switch signal and the control signal based on the total current data, the N branch current data, and the N SOC data to control working states of the DCDC module and the N switch modules.

[0008] In some embodiments, the DCDC module is provided with a switching element, which is configured to be turned on or off based on the control signal.

[0009] In some embodiments, the DCDC module is a bidirectional DCDC module.

[0010] In some embodiments, the current collection module comprises N branch current collection modules, which correspond to the N battery branches one by one, and the branch current collection module is connected to the battery pack of the corresponding battery branch, and the N branch current collection modules are used to collect the N branch current data.

[0011] In some embodiments, the current collection module further comprises a total current collection module connected between the total positive end and the total negative end, which is used to collect the total current data.

[0012] In some embodiments, the control module comprises a communication unit connected to the current collection module and the SOC collection module, which is used to receive the total current data, the N branch current data and the N SOC data; a control unit connected to the communication unit, the DCDC module and the N switching modules, which is used to calculate average current data based on the total current data, and average SOC data based on the N SOC data; and further used to output the switching signal and the control signal based on the average current data and the average SOC data.

[0013] In some embodiments, each of the N switching modules comprises a switching tube, the first end of which is connected to the second end of the DCDC module, the second end of which is connected to the middle end of the corresponding battery branch, and the control end of which is used as the receiving end of the control signal.

[0014] In the second aspect, the embodiments of the present application provide a parallel battery pack equalization system based on a daisy chain topology, which comprises the parallel battery pack equalization circuit based on a daisy chain topology as described above.

[0015] The embodiment of the present application provides a parallel battery pack equalization circuit and equalization system based on a daisy chain topology, and the parallel battery pack equalization circuit based on the daisy chain topology realizes current equalization by cooperating with a plurality of switches through a shared DCDC module. Specifically, N battery branches are caused to have different equivalent resistances due to the daisy chain connection mode, and then initial currents are uneven. The equalization branch works based on a switching signal and a control signal. When the current of a certain battery branch deviates from a target value (such as an average current), the DCDC module works based on the control signal, and the switching module corresponding to the battery branch works (for example, is turned on) based on the switching signal, so that the DCDC module and the middle end of the corresponding battery branch are in communication, so that the DCDC module works to control the working current of the battery branch, thereby realizing equalization of the working currents of the battery branches. The embodiment of the present application reduces the cost by multiplexing the DCDC module. The equalization branch only needs to process the current difference (usually a small part of the total current) between the battery branches, rather than the large current of the main road. Therefore, the rated power of the DCDC module and the switching element can be significantly reduced, and smaller and lower-cost devices are selected. BRIEF DESCRIPTION OF DRAWINGS

[0016] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are schematic and not intended to be limiting of the embodiments, and in which like reference numerals designate similar items in the figures, and in which: the drawings are not to scale.

[0017] Figure 1 is a structural block diagram of a parallel battery pack equalization circuit based on a daisy chain topology provided by an embodiment of the present application;

[0018] Figure 2 is a structural block diagram of a parallel battery pack equalization circuit based on a daisy chain topology provided by another embodiment of the present application;

[0019] Figure 3 is a structural block diagram of a current collection module provided by an embodiment of the present application;

[0020] Figure 4 is a structural block diagram of a control module provided by an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, not all the embodiments of the present application. It should be understood that the specific embodiments described herein are only used to explain the present application, and not used to limit the present application.

[0022] The technical features involved in the various embodiments of the present application described below can be combined with each other without conflict and can be combined with each other.

[0023] When an element is expressed as "connected to" another element, it can be directly connected to the other element, or one or more intervening elements can be present therebetween.

[0024] The terms "first", "second", and the like in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally a class, not limited to the number of objects, for example, the first object can be one or more.

[0025] The embodiments of the present application provide a parallel battery pack equalization circuit 100 based on a daisy chain topology, as shown in Figure 1 The parallel battery pack equalization circuit 100 based on the daisy chain topology includes N battery branches, N is an integer greater than 1, and an equalization branch 20.

[0026] Specifically, each of the N battery branches includes an equivalent resistance and a battery pack. The first end of the equivalent resistance is the first end of the battery branch, the second end of the equivalent resistance and the first end of the battery pack are connected to a point and are the middle end of the battery branch, and the second end of the battery pack is the second end of the battery branch. Wherein, the N battery branches are connected in parallel, the first end of the next level battery branch is connected to the middle end of the previous level battery branch, the first end of the topmost level battery branch is the total positive end, and the second end of each of the N battery branches is connected to the total negative end. The equalization branch 20 includes a DCDC module 21 and N switch modules. Each of the N switch modules corresponds to one of the N battery branches. The first end of each of the N switch modules is connected to the second end of the DCDC module 21, and the second end of each of the N switch modules is connected to the middle end of the battery branch corresponding thereto. The first end of the DCDC module 21 is connected to the total positive end. Wherein, the N switch modules are configured to work based on a switch signal to correspondingly connect the DCDC module 21 and the battery branch; the DCDC module 21 is configured to work based on a control signal to equalize the working current of the N battery branches.

[0027] For example, Figure 1 Taking N equal to 3 as an example, the parallel battery pack equalization circuit 100 based on the daisy chain topology includes a first battery branch 11, a second battery branch 12, a third battery branch 13, and an equalization branch 20. The equalization branch 20 includes a first switch module 221, a second switch module 222, a third switch module 223, and a DCDC module 21.Figure 1 The positive electrode of the battery pack is a first end of the battery pack, and the negative electrode of the battery pack is a second end of the battery pack.

[0028] In actual application, the N battery branches have different equivalent resistances due to the daisy chain connection mode, and thus the initial currents are uneven. The balancing branch 20 works based on the switching signal and the control signal. When the current of a certain battery branch deviates from the target value (such as the average current), the DCDC module 21 works based on the control signal, and the switching module corresponding to the battery branch works (for example, is turned on) based on the switching signal, so that the DCDC module 21 is in communication with the middle end of the corresponding battery branch, thereby causing the DCDC module 21 to work to control the working current of the battery branch, so as to balance the working currents of the N battery branches. For example, when the battery branch is in a discharging state, if the discharging current of a certain battery branch is low (less than the average current), the switching module of the battery branch is controlled to work (for example, is turned on), the DCDC module 212 corresponding to the battery branch is connected, and the DCDC module 21 is controlled to work to increase the discharging current. Since the total load current is fixed, the adjustment of the current of a certain branch will cause the currents of other branches to change correspondingly, and finally through the dynamic compensation of the balancing branch, the working currents of all the battery branches tend to be consistent, achieving the balancing effect.

[0029] The parallel battery pack balancing circuit 100 based on the daisy chain topology works cooperatively with the multiple switches through the shared DCDC module to achieve current balancing, and reduces the cost through the reuse of the DCDC module. The balancing branch only needs to process the current difference between the battery branches (usually a small part of the total current), rather than the large current of the main branch. Therefore, the rated power of the DCDC module and the switching element can be significantly reduced, and smaller and lower-cost devices can be selected.

[0030] In some embodiments, as shown in FIG. 1, the parallel battery pack balancing circuit 100 based on the daisy chain topology further includes a current collection module 30 and a control module 40. Figure 2

[0031] Specifically, the current collection module 30 is connected to the total positive end, the total negative end, and the N battery branches, respectively. The current collection module 30 is configured to collect the total current data between the total positive end and the total negative end and the N branch current data corresponding to the N battery branches in real time. The control module 40 is connected to the current collection module 30, the DCDC module 21, and the N switching modules, respectively. The control module 40 is configured to output the switching signal and the control signal based on the total current data and the N branch current data, so as to control the working states of the DCDC module 21 and the N switching modules, thereby balancing the working currents of the N battery branches.

[0032] ​In practical applications, the current acquisition module 30 collects the total current data between the positive and negative terminals and the current data of each of the N battery branches in real time, and transmits this data to the control module 40. The control module 40 analyzes the relationship between the total current and the current of each branch to determine whether there is a current imbalance among the battery branches (e.g., the current of a branch deviates from the average current of the total current by a proportion exceeding a threshold), and then generates corresponding switching signals and control signals. The switching signals control the on / off state of the N switching modules to select the battery branch that needs adjustment. The control signals drive the DC-DC module 21 to output a specific voltage or current, achieving balance by adjusting the operating current of that branch. Through continuous acquisition, analysis, and adjustment, the operating current of all battery branches is kept consistent, improving the overall performance and lifespan of the battery pack.

[0033] In some embodiments, such as Figure 2 As shown, the parallel battery pack balancing circuit 100 based on daisy-chain topology also includes a SOC acquisition module 50. The SOC acquisition module is connected to N battery branches respectively, and the SOC acquisition module 50 is used to acquire N SOC data corresponding to the N battery branches in real time.

[0034] Furthermore, the control module 40 is connected to the SOC acquisition module 50. The control module 40 is also used to output switching signals and control signals based on the total current data, N branch current data and N SOC data to control the working status of the DC-DC module 21 and the N switching modules.

[0035] In some embodiments, the DC-DC module 21 is provided with a switching element, which is configured to be switched on and off based on a control signal.

[0036] Specifically, the switching elements (such as MOSFETs and IGBTs) of the DC-DC module 21 are controlled to turn on and off via PWM (Pulse Width Modulation) signals. The control module 40 determines whether there is a current imbalance between battery branches based on the total current data, the current data of N branches, and the SOC data of N branches, and calculates the current that needs to be compensated for in the battery branches accordingly. Based on the compensation current, a corresponding PWM signal is generated, and the switching elements of the DC-DC module are turned on and off based on this PWM signal to make the operating current of all battery branches approach the same, thus achieving a balancing effect.

[0037] In some embodiments, DC-DC module 21 is a bidirectional DC-DC module.

[0038] Specifically, when the SOC of a certain battery branch is too high or the discharging current is too high when the battery branch is discharging, the DCDC module 21 transfers the energy of the battery to the total positive end, increasing the discharging current thereof. When the SOC of a certain battery branch is too low or the charging current is too low when the battery branch is charging, the DCDC module 21 obtains energy from the total positive end and supplements it to the battery, increasing the charging current thereof, thereby realizing balance in turn.

[0039] The bidirectional DCDC module can increase the current of the discharging loop of the battery branch when the battery branch is discharging, and can also increase the current of the charging loop of the battery branch when the battery branch is charging, thereby realizing balance in both charging and discharging.

[0040] In some embodiments, the current collection module 30 includes N branch current collection modules. The N branch current collection modules correspond one-to-one to the N battery branches, and the branch current collection module is connected to the battery pack of the corresponding battery branch. The N branch current collection modules are used to collect N branch current data.

[0041] Specifically, each branch current collection module is directly connected to the battery pack of the corresponding battery branch, and the battery pack current, i.e., the branch current data, is obtained in real time by a Hall sensor or resistance sampling.

[0042] In some embodiments, the current collection module 30 further includes a total current collection module. The total current collection module 30 is connected between the total positive end and the total negative end, and is used to collect total current data.

[0043] Specifically, the total current collection module is connected between the total positive end and the total negative end, and collects the total current of the entire battery pack (N battery branches).

[0044] For example, Figure 3 As shown, if N is 3, the current collection module 30 includes: a first branch current collection module 311 connected to the first battery pack 111, a second branch current collection module 312 connected to the second battery pack 121, a third branch current collection module 313 connected to the third battery pack 131, and a total current collection module 320 connected between the total positive end and the total negative end.

[0045] In some embodiments, as Figure 4As shown, the control module 40 includes a communication unit 41 and a control unit 42. The communication unit 41 is connected to the current collection module 30 and the SOC collection module 50, and is configured to receive the total current data, the N branch current data, and the N SOC data. The control unit 42 is connected to the communication unit 41, the DCDC module 21, and N switch modules (not shown in the figure), and is configured to calculate the average current data based on the total current data, calculate the average SOC data based on the N SOC data, and calculate the current that needs to be compensated by the battery branch based on the average current data and the average SOC data, and output the switch signal and the control signal based on the compensation current.

[0046] In actual application, after the communication unit 41 receives the total current, the branch current data, and the SOC data of the SOC collection module 50, the communication unit 41 transmits the data to the control unit 42. The control unit 42 first calculates the average current (total current / N) and the average SOC data (average of the SOC data of each branch) as a reference benchmark, and then compares the deviation (for example, set the threshold value of ±5%) of the collected current and the SOC data of each branch from the average value. When the collected SOC data of a certain branch exceeds the threshold value and the collected current is less than the average current, the corresponding switch signal is generated (for example, the switch module of the branch with the largest deviation is preferentially turned on to balance), and the output power of the DCDC module 21 is adjusted based on the collected current, the collected SOC data, the average current data, and the average SOC data (for example, the difference between the collected current data of each branch and the average current data and the difference between the collected SOC data and the average SOC data can be considered to adjust the duty cycle of the PWM to adjust the DCDC module 21 by the control signal), which can accurately control the energy conversion direction and efficiency of the DCDC module and accurately adjust the current of each branch.

[0047] In some embodiments, each of the N switch modules includes a switch tube. The first end of the switch tube is connected to the second end of the DCDC module 21, the second end of the switch tube is connected to the middle end of the battery branch corresponding to the switch tube, and the control end of the switch tube is configured as the receiving end of the control signal. The shared DCDC module is realized by the multiplexing switch module, the DCDC module and the switch module work cooperatively to realize current balancing, and the cost is reduced by multiplexing the DCDC module. In some embodiments, the switch tube can be a relay, a triode, a MOS tube, or other switch devices, which are specifically set according to actual needs.

[0048] The embodiment of the application provides a parallel battery pack equalization circuit 100 based on a daisy chain topology, which realizes current equalization by cooperating with a plurality of switches through a shared DCDC module. Specifically, N battery branches have different equivalent resistances due to the daisy chain connection mode, thereby causing initial current imbalance. The equalization branch works based on a switching signal and a control signal. When the current of a certain battery branch deviates from a target value (such as an average current), the DCDC module works based on the control signal, and the switching module corresponding to the battery branch works (for example, is turned on) based on the switching signal, so that the DCDC module is in communication with the middle end of the corresponding battery branch, thereby enabling the DCDC module to work to control the working current of the battery branch, thereby realizing equalization of the working currents of the battery branches. The application embodiment reduces the cost by multiplexing the DCDC module. The equalization branch only needs to process the current difference (usually a small part of the total current) between the battery branches, rather than the large current of the main road. Therefore, the rated power of the DCDC module and the switching element can be significantly reduced, and smaller and lower-cost devices are selected.

[0049] The embodiment of the application also provides a parallel battery pack equalization system based on a daisy chain topology, which includes the parallel battery pack equalization circuit 100 based on a daisy chain topology as described above.

[0050] Specifically, the structure and working principle of the parallel battery pack equalization circuit 100 based on a daisy chain topology can be referred to the above embodiment, which will not be described here.

[0051] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, but not to limit them; under the idea of the application, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes of different aspects of the application as described above. In order to be brief, they are not provided in details; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A parallel battery pack balancing circuit based on daisy-chain topology, characterized in that, The parallel battery pack balancing circuit based on daisy-chain topology includes: There are N battery branches, where N is an integer greater than 1; each of the N battery branches includes an equivalent resistor and a battery pack, the first end of the equivalent resistor is the first end of the battery branch, the second end of the equivalent resistor is connected to the first end of the battery pack at a point and is the middle end of the battery branch, and the second end of the battery pack is the second end of the battery branch; wherein, the N battery branches are connected in parallel, the first end of the next-level battery branch is connected to the middle end of the previous-level battery branch, the first end of the top-level battery branch is the overall positive terminal, and the second end of each of the N battery branches is connected to the overall negative terminal; A balancing branch includes a DC-DC converter module and N switching modules. Each of the N switching modules corresponds one-to-one with one of the N battery branches. The first terminal of each of the N switching modules is connected to the second terminal of the DC-DC converter module. The second terminal of each of the N switching modules is connected to the middle terminal of its corresponding battery branch. The first terminal of the DC-DC converter module is connected to the overall positive terminal. The N switching modules are configured to operate based on switching signals, and the DC-DC converter module is configured to operate based on control signals to balance the operating current of the N battery branches. The DC-DC module is a bidirectional DC-DC module; When a battery branch is discharging, if the discharge current of a certain battery branch is too high, the DC-DC module transfers the energy of that battery to the positive terminal of the main circuit, increasing its discharge current. When a battery branch is charging, if the charging current of a certain battery branch is too low, the DC-DC module obtains energy from the positive terminal of the main circuit and replenishes the battery, increasing its charging current, and so on to achieve equalization.

2. The parallel battery pack balancing circuit based on daisy-chain topology according to claim 1, characterized in that, The parallel battery pack balancing circuit based on daisy-chain topology also includes: A current acquisition module is connected to the total positive terminal, the total negative terminal, and the N battery branches respectively. The current acquisition module is used to acquire the total current data between the total positive terminal and the total negative terminal and the current data of the N branches corresponding to the N battery branches in real time. A control module is connected to the current acquisition module, the DC-DC module, and the N switch modules. The control module is used to output the switch signal and the control signal based on the total current data and the current data of the N branches to control the working state of the DC-DC module and the N switch modules, thereby balancing the working current of the N battery branches.

3. The parallel battery pack balancing circuit based on daisy-chain topology according to claim 2, characterized in that, The parallel battery pack balancing circuit based on daisy-chain topology also includes: The SOC acquisition module is connected to the N battery branches respectively, and the SOC acquisition module is used to collect N SOC data corresponding to the N battery branches in real time. The control module is connected to the SOC acquisition module. The control module is also used to output the switching signal and the control signal based on the total current data, the N branch current data and the N SOC data, so as to control the working state of the DC-DC module and the N switching modules.

4. The parallel battery pack balancing circuit based on daisy-chain topology according to claim 1, characterized in that, The DC-DC module is equipped with a switching element, which is configured to be switched on and off based on the control signal.

5. The parallel battery pack balancing circuit based on daisy-chain topology according to claim 2, characterized in that, The current acquisition module includes: There are N branch current acquisition modules, each corresponding to one of the N battery branches. Each branch current acquisition module is connected to the battery pack of its corresponding battery branch. The N branch current acquisition modules are used to acquire the current data of the N branches.

6. The parallel battery pack balancing circuit based on daisy-chain topology according to claim 5, characterized in that, The current acquisition module also includes: A total current acquisition module is connected between the total positive terminal and the total negative terminal, and the total current acquisition module is used to acquire the total current data.

7. The parallel battery pack balancing circuit based on daisy-chain topology according to claim 3, characterized in that, The control module includes: A communication unit is provided, which connects the current acquisition module and the SOC acquisition module; the communication unit is used to receive the total current data, the N branch current data, and the N SOC data. The control unit is connected to the communication unit, the DC-DC module, and the N switch modules respectively. The control unit is used to calculate the average current data based on the total current data and to calculate the average SOC data based on the N SOC data. It is also used to output the switch signal and the control signal based on the average current data and the average SOC data.

8. The parallel battery pack balancing circuit based on daisy-chain topology according to claim 1, characterized in that, Each of the N switching modules includes: A switching transistor, the first end of which is connected to the second end of the DC-DC module, the second end of which is connected to the middle end of the corresponding battery branch, and the control end of which is used as the receiving end of the control signal.

9. A parallel battery pack balancing system based on daisy-chain topology, characterized in that, The equalization system includes a parallel battery pack equalization circuit based on a daisy-chain topology as described in any one of claims 1 to 8.

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