Battery heating circuit, battery heating method, and electric vehicle

Abstract

The application provides a battery heating circuit, a battery heating method and an electric vehicle. The battery heating circuit comprises a first relay, a second relay and a plurality of power batteries. The plurality of power batteries form a first parallel branch and a second parallel branch, and the first parallel branch is connected in parallel with the second parallel branch. One electrical end of the first relay is electrically connected with the first parallel branch, and the other electrical end of the first relay is electrically connected with a motor. One electrical end of the second relay is electrically connected with the second parallel branch, and the other electrical end of the second relay is electrically connected with the motor. The first relay and the second relay are alternately closed. The application can heat the power batteries, and under the premise that the required heating power is constant, the required heating current is reduced, so that the heating degree of the motor and the cable is reduced, and the design requirements of the relay and the cable are reduced.

Description

Technical Field

[0001] This application relates to the field of power batteries, and more specifically, to a battery heating circuit, a battery heating method, and an electric vehicle. Background Technology

[0002] Currently, one method for heating power batteries with AC current is to divide the power battery into upper and lower parts, connecting the middle part to the neutral point of the motor, and then heating the power battery through the large current output from the motor's neutral point. However, the large current output from the motor's neutral point causes the cables and motor to overheat, thus requiring high-performance relays and cables. Summary of the Invention

[0003] The purpose of this application is to provide a battery heating circuit, a battery heating method, and an electric vehicle for heating a power battery, and to reduce the current required for heating while maintaining a certain power required for heating, thereby reducing the heat generation of the motor and cables and reducing the design requirements for relays and cables.

[0004] In a first aspect, the present invention provides a battery heating circuit, the battery heating circuit comprising: a control relay and a plurality of power batteries;

[0005] The plurality of power batteries form n parallel branches, where n is an integer greater than or equal to 2, and the number of control relays is m, where m equals n;

[0006] One electrical terminal of the control relay is electrically connected to the parallel branch, and the other electrical terminal of the control relay is electrically connected to the neutral point of the motor. Each control relay is used to control the on / off state of the circuit between a unique parallel branch and the motor.

[0007] In the first aspect of this application, since several power batteries form n parallel branches, and each of the control relays is used to control the circuit connection between a unique parallel branch and the motor, the batteries can be alternately heated by the alternating on and off of m control relays. This reduces the current required for heating the battery pack while using a fixed power, thereby reducing the heat generation of the motor and cables and lowering the design requirements for the relays and cables.

[0008] In an optional implementation, the parallel branch includes two or more of the power batteries, wherein the two or more power batteries are connected in series.

[0009] In this optional embodiment, two or more of the power batteries can be connected in series.

[0010] In an optional embodiment, one electrical terminal of the control relay is electrically connected to the neutral point of two or more of the power batteries, and the other electrical terminal of the control relay is electrically connected to the neutral point of the motor.

[0011] In this optional embodiment, one electrical terminal of the control relay can be electrically connected to the power battery through two or more neutral points of the power battery, and the other electrical terminal of the control relay can be electrically connected to the motor through the neutral point of the motor.

[0012] In a second aspect, the present invention provides a battery heating method, wherein the battery heating method is applied to a battery heating circuit as described in any of the foregoing embodiments, the method comprising:

[0013] When the power battery needs to be heated, the inverter controls the motor to generate an AC voltage at the neutral point, so that the neutral point of the motor outputs AC current to the m control relays;

[0014] Based on a preset cycle, m control relays, a control relays, and ma control relays are alternately closed, where a is an integer greater than or equal to 1 and less than or equal to m-1.

[0015] In this optional embodiment, by controlling the motor to generate AC voltage at the neutral point, the neutral point of the motor can output AC current to m control relays. Furthermore, by controlling the m control relays, a control relays, and ma control relays to alternately close based on a preset cycle, the current required for heating the power battery can be reduced by the alternating closure of a control relays and ma control relays, while keeping the power required for heating the power battery constant. This reduces the heat generation of the motor and cables and lowers the design requirements for the relays and cables.

[0016] In an optional embodiment, the frequency of the alternating current output by the motor is from 0.01 Hz to 10 kHz.

[0017] In an optional implementation, the preset period is 0.1-60 minutes.

[0018] This optional implementation, by setting the preset cycle to 0.1-60 minutes, can avoid large differences in temperature and other factors between different battery packs, and avoid frequent switching of the control relay due to setting the value too small.

[0019] In an optional implementation, the step of controlling m control relays, a control relays, and ma control relays to alternately close based on a preset period includes:

[0020] When it is detected that a control relays need to be disconnected, within a preset time interval before a control relays are disconnected, ma control relays are controlled to close, so that a control relays and ma control relays are simultaneously closed within the preset time interval.

[0021] The control relays mentioned above are disconnected.

[0022] This permissible implementation avoids current fluctuations or surges by simultaneously closing a and ma control relays within the preset time interval.

[0023] In this optional embodiment, the preset time interval is 0.5 seconds to 1.5 seconds.

[0024] This optional implementation, by setting the preset time interval to 0.5 seconds to 1.5 seconds, can match the time required for *a* control relays to close and open, and the time required for *ma* control relays to close and open. Furthermore, setting the preset time interval to 0.5 seconds to 1.5 seconds can meet the requirements for signal delay.

[0025] In this optional embodiment, the preset time interval is 1 second.

[0026] Thirdly, the present invention provides an electric vehicle, the electric vehicle application including a battery heating circuit and a controller as described in any of the foregoing embodiments, wherein the controller is used to execute the method of the second aspect of this application.

[0027] Since the electric vehicle of the third aspect of this application has the battery heating circuit of the first aspect of this application and can perform the method of the second aspect of this application, it has all the advantages of the first and second aspects of this application. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of a battery heating circuit disclosed in an embodiment of this application;

[0030] Figure 2 This is a schematic flowchart of a battery heating method disclosed in an embodiment of this application;

[0031] Figure 3This is a schematic diagram of the alternating switching of a first relay and a second relay as disclosed in an embodiment of this application.

[0032] Icons: K1 - First Relay; K2 - Second Relay; U1 - First Power Battery; U2 - Second Power Battery; U3 - Third Power Battery; U4 - Fourth Power Battery; Q1 - First Diode; Q2 - Second Diode; Q3 - Third Diode; Q4 - Fourth Diode; Kp - Third Relay; Kn - Fourth Relay. Detailed Implementation

[0033] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0034] Example 1

[0035] Please see Figure 1 , Figure 1 This is a schematic diagram of a battery heating circuit disclosed in an embodiment of this application. Figure 1 As shown, the battery heating circuit of this application embodiment includes: a first relay K1, a second relay K2, and a plurality of power batteries, wherein the plurality of power batteries form a first parallel branch and a second parallel branch.

[0036] In this embodiment, preferably, the battery heating circuit includes four power batteries: a first power battery U1, a second power battery U2, a third power battery U3, and a fourth power battery U4. The first power battery U1 and the second power battery U2 form a first parallel branch, while the third power battery U3 and the fourth power battery U4 form a second parallel branch. Further, in the first parallel branch, the first power battery U1 and the second power battery U2 are connected in series, while in the second parallel branch, the third power battery U3 and the fourth power battery U4 are connected in series.

[0037] In this embodiment, one electrical terminal of the first relay K1 is electrically connected to the first parallel branch, and the other electrical terminal of the first relay K1 is electrically connected to the motor, wherein, as shown... Figure 1 As shown, one electrical terminal of the first relay K1 is electrically connected to the neutral point of the first power battery U1 and the second power battery U2, while the other electrical terminal of the first relay K1 is electrically connected to the neutral point of the motor.

[0038] In this embodiment, one electrical terminal of the second relay K2 is electrically connected to the second parallel branch, and the other electrical terminal of the second relay K2 is electrically connected to the motor. Wherein, as... Figure 1 As shown, one electrical terminal of the second relay K2 is electrically connected to the neutral point of the third power battery U3 and the fourth power battery U4, while the other electrical terminal of the second relay K2 is electrically connected to the neutral point of the motor.

[0039] In this embodiment, the battery heating circuit further includes a first diode Q1, a second diode Q2, a third diode Q3, and a fourth diode Q4. These diodes constitute a three-phase inverter, which controls the motor current. Furthermore, the battery heating circuit also includes a third relay Kp and a fourth relay Kn. When both relays Kp and Kn are closed, the motor current can form a circuit with the first relay K1 and the second relay K2, thereby supplying power to the first power battery U1, the second power battery U2, the third power battery U3, and the fourth power battery U4.

[0040] In this embodiment, since several power batteries form a first parallel branch and a second parallel branch, one electrical terminal of the first relay K1 can be electrically connected to the first parallel branch, and the other electrical terminal of the first relay K1 is electrically connected to the motor. Similarly, one electrical terminal of the second relay K2 can be electrically connected to the second parallel branch, and the other electrical terminal of the second relay K2 is also electrically connected to the motor. Thus, through the first relay K1 and the second relay K2, power can be alternately supplied to the first parallel branch and the second parallel branch, thereby alternately heating the power batteries in the first parallel branch and the batteries in the second parallel branch. Simultaneously, since the first parallel branches are connected in parallel, given a fixed power requirement for heating the power batteries in the first and second parallel branches, the alternating power supply to the first and second parallel branches reduces the current required for heating, thereby reducing the heat generation of the motor and cables, and lowering the design requirements for the relays and cables.

[0041] In this embodiment of the application, as an example, it is assumed that the internal resistance of the entire battery pack is R. bat (The overall resistance of the battery pack measured against the positive and negative terminals), based on the parallel circuit resistance calculation formula Rbat=(R1*R2) / (R1+R2) and R1=R2, the internal resistance of the first parallel branch and the second parallel branch can be derived as R1=R2=2*Rbat. Furthermore, since the effective value of the neutral current generated by the three-phase inverter controlling the motor is independent of the battery's internal resistance, compared to the case with only one "battery half-bridge" (i.e., multiple power batteries forming only one branch), the overall battery pack heating power calculated based on the circuit of this application embodiment is:

[0042]

[0043] Where n = 2, and the coefficient C is a constant whose value is independent of the number of battery groups n, but related to the waveform of the neutral current. On the other hand, I N,RMSIt is the effective value of the alternating current flowing through the neutral line.

[0044] Furthermore, based on Equation 1 and P where multiple power batteries form only one branch, bat,1 We can obtain:

[0045]

[0046] Furthermore, when the required heating power is constant, the ratio of the required neutral current can be easily obtained as follows:

[0047]

[0048] Furthermore, as shown in Equation 3, the motor can heat the power battery with a lower current and the same power, thereby reducing the heat generation of the motor and cables, and reducing the design requirements for relays and cables.

[0049] As can be seen from the inventive concept given above in the embodiments of this application, the battery heating circuit may include n parallel branches, where n is an integer greater than or equal to 2, and the number of control relays is m, where m equals n. For example, the battery heating circuit may include 4 parallel branches, and correspondingly, the battery heating circuit may include 4 control relays, wherein one electrical terminal of the control relay is electrically connected to the parallel branch, and the other electrical terminal of the control relay is electrically connected to the neutral point of the motor, wherein each control relay is used to control the circuit connection and disconnection between a unique parallel branch and the motor.

[0050] It should be noted that the term "control relay" is a general term for relays that perform the same function as the first and second relays.

[0051] In an optional embodiment, the parallel branch includes two or more power batteries, wherein the two or more power batteries are connected in series. In this optional embodiment, the two or more power batteries can be connected in series.

[0052] In an optional implementation, the number of power batteries can be either 4 or 6.

[0053] In an optional embodiment, one electrical terminal of the control relay is electrically connected to the neutral point of two or more power batteries, and the other electrical terminal of the control relay is electrically connected to the neutral point of the motor. Alternatively, one electrical terminal of the control relay can be electrically connected to the power batteries via the neutral points of two or more power batteries, and the other electrical terminal of the control relay can be electrically connected to the motor via the neutral point of the motor.

[0054] Example 2

[0055] Please see Figure 2 , Figure 2 This is a schematic flowchart of a battery heating method disclosed in an embodiment of this application, wherein the battery heating method is applied to a battery heating circuit as described in any of the foregoing embodiments. Figure 2 As shown, the method in this application embodiment includes the following steps:

[0056] 101. When the power battery needs to be heated, the inverter controls the motor to generate AC voltage at the neutral point, so that the neutral point of the motor outputs AC current to m control relays.

[0057] 102. Based on a preset cycle, control m control relays, a control relays and ma control relays alternately close, where a is an integer greater than or equal to 1 and less than or equal to m-1.

[0058] In this optional embodiment, by controlling the motor to generate AC voltage at the neutral point through the inverter, the neutral point of the motor can output AC current to m control relays. Furthermore, by controlling the m control relays to alternately close a control relay and ma control relay based on a preset cycle, the current required for heating the power battery can be reduced by alternately closing a control relay and ma control relay, thus reducing the heat generation of the motor and cables and reducing the design requirements for the relays and cables, while keeping the power required for heating the power battery constant.

[0059] In this application embodiment, for example, when a=1 and m=2, please refer to [link / reference]. Figure 3 , Figure 3 This is a schematic diagram illustrating the alternating switching of a first relay K1 and a second relay K2, as disclosed in an embodiment of this application. Figure 3 As shown, by outputting a high level to the first relay K1, the first relay K1 can be controlled to close; at the same time, by outputting a low level to the second relay K2, the second relay K2 can be controlled to open.

[0060] In this optional implementation, a can be 3 and m can be 4, or a can be 4 and m can be 1. For example, when m is 3 and a can be 2, that is, when the battery heating circuit includes 3 control relays k1, k2 and k3, (k1, k2) can be turned on and off simultaneously. In this way, the alternating closing of a control relays and ma control relays can be achieved by using the cyclic sequence of [(K1+K2) closed, k3 open] → [(K2+K3) closed, k1 open] → [(K3+K1) closed, k2 open] → [(K1+K2) closed, k3 open].

[0061] In an optional implementation, the preset cycle is 0.1-60 minutes. In this optional implementation, setting the preset cycle to 0.1-60 minutes can avoid large differences in temperature between different battery packs, and avoid frequent switching of the first relay K1 and the second relay K2 due to the setting value being too small.

[0062] In an optional implementation, the step of controlling m control relays, a control relays, and ma control relays to alternately close based on a preset period includes:

[0063] When it is detected that a control relays need to be disconnected, within a preset time interval before a control relays are disconnected, ma control relays are controlled to close, so that a control relays and ma control relays are simultaneously closed within the preset time interval.

[0064] Control ma control relays to disconnect.

[0065] In this optional implementation, as an example, such as Figure 3 As shown, the first relay K1 and the second relay K2 are both in a high-level state at the alternating critical time points.

[0066] In this optional embodiment, when the first relay K1 needs to be disconnected, the second relay K2 is controlled to close within a preset time interval before the first relay K1 disconnects. This ensures that the first relay K1 and the second relay K2 are simultaneously closed within the preset time interval, thereby avoiding any time when the first relay K1 and the second relay K2 are simultaneously disconnected. This prevents disruptions to the normal operation of the inverter and avoids current fluctuations or surges. In other words, this optional embodiment avoids current fluctuations or surges by ensuring that *a* control relays and *ma* control relays are simultaneously closed within the preset time interval.

[0067] In this optional implementation, specifically, in some scenarios, m control relays are selectively closed while the other control relays are in an open state, alternating between closing and closing, i.e., a = 1. For example, assuming there are 5 control relays K1, K2, K3, K4, and K5, then for the sequential t1, t2, t3, t4, and t5, the state sets of the 5 control relays are as follows:

[0068] t1: [(K1), (K2, K3, K4, K5)];

[0069] t2: [(K2), (K1, K3, K4, K5)];

[0070] t3: [(K3), (K1, K2, K4, K5)];

[0071] t4: [(K4), (K1, K2, K3, K5)];

[0072] t5: [(K5), (K1, K2, K3, K4)].

[0073] In the above scenario, when switching from time t1 to time t2, control relays K1 and K2 are simultaneously closed within a preset time interval formed at the end of time t1 or the beginning of time t2. Correspondingly, when switching from time t2 to time t3, from time t3 to time t4, etc., both control relays are simultaneously closed within a preset time interval.

[0074] In this optional implementation, specifically, in some scenarios, the control relays can be switched in groups, i.e., when a = 2 or greater than 2. For example, assuming there are 4 control relays: K1, K2, K3, and K4, then the state sets of the control relays at times t1 and t2 in sequence are as follows:

[0075] t1: [(K1, K2), (K3, K4)];

[0076] t2: [(K3, K4), (K1, K2)];

[0077] To address this situation further, in a specific scenario, the control relay that needs to be closed at time t1 also needs to be closed at time t2, for example:

[0078] t1: [(K1, K2), (K3, K4)];

[0079] t2: [(K2, K3), (K1, K4)];

[0080] In the above scenario, K2 needs to be closed simultaneously at both time t1 and t2. That is, K2 remains closed throughout the period from t1 to t2. Therefore, during the transition from t1 to t2, all control relays will not be open. Thus, within the preset time interval, control relays K1 and K3 can be either both closed or not. Preferably, in this embodiment, control relays K1 and K3 are both closed. This avoids excessive current in the branch circuit corresponding to control relay K2 within the preset time interval, thereby preventing current exceeding the battery charging / discharging current limit. In an optional implementation, the preset time interval is 0.5 seconds to 1.5 seconds.

[0081] In this optional embodiment, by setting the preset time interval to 0.5 seconds to 1.5 seconds, the time required for the first relay K1 to close and open, and the time required for the second relay K2 to close and open, can be matched. Furthermore, setting the preset time interval to 0.5 seconds to 1.5 seconds can meet the signal delay requirements. That is, this optional embodiment, by setting the preset time interval to 0.5 seconds to 1.5 seconds, can match the time required for *a* control relays to close and open, and the time required for *ma* control relays to close and open. Furthermore, setting the preset time interval to 0.5 seconds to 1.5 seconds can meet the signal delay requirements.

[0082] In an optional implementation, the preset time interval is 1 second.

[0083] Thirdly, the present invention provides an electric vehicle, wherein the electric vehicle application includes a battery heating circuit and a control relay as described in any of the foregoing embodiments, wherein the control relay is used to execute the method of the second aspect of this application.

[0084] Since the electric vehicle of the third aspect of this application has the battery heating circuit of the first aspect of this application and can perform the method of the second aspect of this application, it has all the advantages of the first and second aspects of this application.

[0085] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and there may be other division methods in actual implementation. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the coupling or direct coupling or communication connection shown or discussed may be through some communication interface; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0086] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0087] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0088] It should be noted that if a function is implemented as a software module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0089] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0090] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A battery heating circuit, characterized in that, The battery heating circuit includes: a control relay and several power batteries; The plurality of power batteries form n parallel branches, where n is an integer greater than or equal to 2, and the number of control relays is m, where m equals n; One electrical terminal of the control relay is electrically connected to the parallel branch, and the other electrical terminal of the control relay is electrically connected to the neutral point of the motor. Each control relay is used to control the on / off circuit between a unique parallel branch and the motor. The power batteries in several parallel branches are alternately heated, and the heating power of the power batteries is constant. One electrical terminal of the control relay is uniquely connected to one of the parallel branches, and the other electrical terminal of the control relay is electrically connected to the neutral point of the motor. The heating power of the power battery is constant within a preset period.

2. The battery heating circuit as described in claim 1, characterized in that, The parallel branch includes two or more of the power batteries, wherein the two or more power batteries are connected in series.

3. The battery heating circuit as described in claim 2, characterized in that, One electrical terminal of the control relay is electrically connected to the neutral point of two or more of the power batteries, and the other electrical terminal of the control relay is electrically connected to the neutral point of the motor.

4. A battery heating method, characterized in that, The battery heating method is applied to the battery heating circuit as described in any one of claims 1-3, and the method includes: When the power battery needs to be heated, the inverter controls the motor to generate an AC voltage at the neutral point, so that the neutral point of the motor outputs AC current to the m control relays; Based on a preset cycle, a and ma of the m control relays are alternately closed, where a is an integer greater than or equal to 1 and less than or equal to m-1.

5. The battery heating method as described in claim 4, characterized in that, The frequency of the AC current output by the motor is from 0.01Hz to 10kHz.

6. The battery heating method as described in claim 4, characterized in that, The preset cycle is 0.1-60 minutes.

7. The battery heating method as described in claim 4, characterized in that, The method of controlling a and ma of the m control relays to alternately close based on a preset period includes: When it is detected that a control relays need to be disconnected, within a preset time interval before a control relays are disconnected, ma control relays are controlled to close, so that a control relays and ma control relays are simultaneously closed within the preset time interval. The control relays mentioned above are disconnected.

8. The battery heating method as described in claim 7, characterized in that, The preset time interval is 0.5 seconds to 1.5 seconds.

9. The battery heating method as described in claim 8, characterized in that, The preset time interval is 1 second.

10. An electric vehicle, characterized in that, The electric vehicle includes a controller and a battery heating circuit as described in any one of claims 1-3, wherein the controller is configured to perform the method as described in any one of claims 4-9.

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