Battery self-heating device, control method thereof, and vehicle

Abstract

The application discloses a battery self-heating device and a control method thereof and a vehicle. The battery self-heating device comprises a heating circuit connected with a battery pack, and an energy storage module connected with the heating circuit, wherein the heating circuit is arranged between the energy storage module and the battery pack. The energy storage module and the battery pack are cyclically charged and discharged through the heating circuit, and the alternating current generated by the cyclic charging and discharging makes the battery pack internal resistance generate heat. The application can greatly shorten the battery heating time in a cold environment, and the battery can recover the charging capacity in a short time.

Description

Technical Field

[0001] This application relates to the field of electric vehicle technology, and in particular to a battery self-heating device and its control method, and a vehicle having the battery self-heating device. Background Technology

[0002] Batteries, as a power source, are widely used in the energy systems of pure electric and hybrid vehicles. However, the external characteristics of power batteries are affected by low temperatures, leading to a decrease in driving range and lithium plating during DC charging, causing permanent damage to the battery and reducing its lifespan and capacity. Therefore, in low-temperature environments, batteries need to be heated before use, especially before low-temperature charging, to restore their charging capacity to normal.

[0003] In related technologies, a PTC (Positive Temperature Coefficient) heating scheme is commonly used. This involves heating the water circuit with a PTC heater, and then circulating the water through the circuit to transfer heat to the battery. This causes the battery module's temperature to rise from the outer shell to the inner core. A schematic diagram of the PTC heating scheme is shown below. Figure 1 As shown. However, indirectly heating the battery through the PTC heating water circuit described above results in a longer heating time, leading to low heat exchange efficiency. Summary of the Invention

[0004] The purpose of this application is to at least partially solve one of the aforementioned technical problems.

[0005] Therefore, the first objective of this application is to provide a battery self-heating device. This battery self-heating device can significantly shorten the battery warm-up time in cold environments, enabling the battery to recover its charging capacity in a shorter time.

[0006] The second objective of this application is to provide a control method for a battery self-heating device.

[0007] The third objective of this application is to propose a vehicle.

[0008] To achieve the above objectives, the battery self-heating device proposed in the first aspect of this application includes: a heating circuit connected to a battery pack; and an energy storage module connected to the heating circuit, wherein the heating circuit is disposed between the energy storage module and the battery pack; wherein the energy storage module and the battery pack perform cyclic charging and discharging of each other through the heating circuit, and the generated alternating current causes the internal resistance of the battery pack to generate heat.

[0009] According to the battery self-heating device of this application embodiment, a heating circuit and an energy storage module can be connected to the battery pack port. The heating circuit is set between the energy storage module and the battery pack, so that the energy storage module and the battery pack can perform cyclic charging and discharging of each other through the heating circuit. The generated alternating current causes the internal resistance of the battery pack to generate heat, thereby achieving the effect of battery self-heating. As a result, the battery temperature rises from the inside to the outside due to the heat generated by the internal resistance of the battery pack. This can greatly shorten the battery heating time in cold environments and enable the battery to restore its charging capacity in a short time.

[0010] The second aspect of this application proposes a control method for a battery self-heating device, wherein the battery self-heating device is the same as the battery self-heating device described in the first aspect of this application. The control method includes: when the temperature of the battery pack is detected to be lower than a first threshold and it is determined that the battery management system allows the battery to heat, activating a heating circuit to self-heat the battery pack.

[0011] According to the control method of the battery self-heating device in the embodiments of this application, the frequency and amplitude of the battery charging and discharging current can be adjusted by controlling the drive of the bidirectional DC-DC converter, thereby controlling the heat generation of the battery internal resistance and achieving the effect of battery self-heating. This causes the battery temperature to rise from the inside to the outside due to the heat generated by the internal resistance of the battery pack, which can greatly shorten the battery heating time in cold environments and enable the battery to restore its charging capacity in a short time.

[0012] The vehicle proposed in the third aspect of this application includes: the battery self-heating device described in the first aspect of this application.

[0013] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0014] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0015] Figure 1 This is an example diagram of heating a battery pack using PTC and water circulation in existing technology;

[0016] Figure 2 This is a structural block diagram of a battery self-heating device according to an embodiment of this application;

[0017] Figure 3 This is an example diagram of heating a battery pack using an alternating current source according to an embodiment of this application;

[0018] Figure 4This is a circuit example diagram of a battery self-heating device according to an embodiment of this application;

[0019] Figure 5 This is a circuit example diagram of a battery self-heating device according to another embodiment of this application;

[0020] Figure 6 This is a circuit example diagram of a battery self-heating device according to yet another embodiment of this application;

[0021] Figure 7 This is a circuit example diagram of a battery self-heating device according to another embodiment of the present application;

[0022] Figure 8 This is a circuit example diagram of a battery self-heating device according to another embodiment of this application;

[0023] Figure 9 This is a circuit example diagram of a battery self-heating device according to yet another embodiment of this application;

[0024] Figure 10 An example diagram illustrating the relationship between the critical alternating current frequency and the effective value for lithium plating according to an embodiment of this application;

[0025] Figure 11 This is a flowchart of the battery pack self-heating process according to an embodiment of this application;

[0026] Figure 12 This is a waveform diagram showing the duty cycle of the bidirectional DC-DC converter, the voltage of the energy storage module, and the charging and discharging current of the battery according to an embodiment of this application.

[0027] Figure 13 This is a control flowchart of a bidirectional DC-DC converter (fixed duty cycle boundary) according to an embodiment of this application;

[0028] Figure 14 This is a control flowchart of a bidirectional DC-DC converter (real-time updating duty cycle boundary) according to an embodiment of this application;

[0029] Figure 15 This is a structural block diagram of a vehicle according to an embodiment of this application. Detailed Implementation

[0030] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0031] The following description, with reference to the accompanying drawings, describes a battery self-heating device and its control method, as well as a vehicle having the battery self-heating device.

[0032] Figure 2 This is a structural block diagram of a battery self-heating device according to an embodiment of this application. Figure 2 As shown, the battery self-heating device 100 may include a heating circuit 110 and an energy storage module 120. The heating circuit 110 is connected to the battery pack 11; the energy storage module 120 is connected to the heating circuit 110. The heating circuit 110 is disposed between the energy storage module 120 and the battery pack 11. In this embodiment, the energy storage module 120 and the battery pack 11 cyclically charge and discharge each other through the heating circuit 110, and the resulting alternating current causes heat to be generated within the battery pack 11.

[0033] In other words, a heating circuit 110 is added to the front end of the battery pack 11, and the positive and negative terminals of the battery pack 11 are respectively connected to the two ports of the energy storage module 120. The energy storage module 120 and the battery pack 11 cycle through the heating circuit 110 for mutual charging and discharging. The generated alternating current causes the internal resistance of the battery to generate heat, and the battery heats up rapidly. The alternating current then heats the battery pack 11. (See schematic diagram.) Figure 3 As shown.

[0034] It should be noted that in some embodiments, the heating circuit 110 may be a circuit composed of electronic devices such as switching transistors and inductors, and the energy storage module 120 may include a capacitor with energy storage function. For example, in the first embodiment, such as Figure 4 As shown, the heating circuit 110 includes a first switching transistor T1, a second switching transistor T2, and a first inductor L1. The energy storage module 120 includes a first capacitor C1. The first terminal of the first switching transistor T1 is connected to the positive terminal of the battery pack 11. The second terminal of the first switching transistor T1 is connected to one end of the first inductor L1 and the first terminal of the second switching transistor T2. The other end of the first inductor L1 is connected to one end of the first capacitor C1. The second terminal of the second switching transistor T2 and the other end of the first capacitor C1 are connected to the negative terminal of the battery pack 11. The drive signals of the first switching transistor T1 and the second switching transistor T2 are complementary, with the first switching transistor T1 being the primary drive.

[0035] In the first embodiment, the working principle of the energy storage module 120 and the battery pack 11 cyclically charging and discharging each other through the heating circuit 110 includes: when the battery pack is in discharge mode, the initial voltage on the first capacitor C1 is low, the first switch T1 is turned on, the second switch T2 is turned off, and the working circuit is BAT1→T1→L1→C1. The first inductor L1 stores energy (the current flows from the battery to the capacitor C1), and the first capacitor C1 is charged; when the first switch T1 is turned off, the second switch T2 is turned on, and the working circuit is L1→C1→T2. The first inductor L1 releases energy, and the first capacitor C1 is charged. During the discharge process, the first capacitor C1 is always in a charging state, so the voltage on the first capacitor C1 continuously increases. When the battery pack is in charging mode, the initial voltage on the first capacitor C1 is high, the first switch T1 is off, and the second switch T2 is on, with the working circuit being C1→L1→T2. The first inductor L1 stores energy (current flows from the capacitor to the battery). When the first switch T1 is on and the second switch T2 is off, the working circuit is C1→L1→T1→BAT1. During charging, the first capacitor C1 is constantly discharging, so the energy on the first capacitor C1 is transferred to the battery for charging. Thus, the energy storage module 120 and the battery pack 11 cycle through mutual charging and discharging via the heating circuit 110. The generated alternating current can cause heat to be generated in the internal resistance of the battery pack, thereby achieving self-heating of the battery pack.

[0036] It should be noted that the heating circuit 110 may include a non-isolated bidirectional DC-DC converter. That is, a heating circuit can be constructed using a non-isolated bidirectional DC-DC converter and combined with an energy storage module to achieve self-heating of the battery pack. For example, in the second embodiment, as... Figure 5 As shown, the non-isolated bidirectional DC-DC converter 111 may include: a first switch T1, a second switch T2, a first inductor L1, and a first capacitor C1. The first terminal of the first switch T1 is connected to the positive terminal of the battery pack 11. The second terminal of the first switch T1 is connected to one end of the first inductor L1 and the first terminal of the second switch T2, respectively. The other end of the first inductor L1 is connected to one end of the first capacitor C1. The second terminal of the second switch T2 and the other end of the first capacitor C1 are connected to the negative terminal of the battery pack 11, respectively. The drive signals of the first switch T1 and the second switch T2 are complementary, with the first switch T1 acting as the primary driver.

[0037] In the second embodiment, the energy storage module may include either an energy storage capacitor or a DC charging pile. For example, when the energy storage module is an energy storage capacitor, such as... Figure 5The diagram shows the circuit structure of the energy storage capacitor 121 and the non-isolated bidirectional DC-DC converter 111. The energy storage capacitor 121 is connected in parallel to the first capacitor C1 in the non-isolated bidirectional DC-DC converter 111. In other words, by adding an energy storage capacitor outside the non-isolated bidirectional DC-DC converter, this non-isolated bidirectional DC-DC converter can be a bidirectional DC / DC module in a DC charging circuit. For example, when the energy storage module is a DC charging pile, such as... Figure 6 The diagram shows the circuit structure of the DC charging pile 122 and the non-isolated bidirectional DC-DC converter 111. The DC charging pile 122 is connected in parallel to the first capacitor C1 in the non-isolated bidirectional DC-DC converter 111. It can be seen that this non-isolated bidirectional DC-DC converter is integrated with the bidirectional DC / DC module for DC charging, forming an integrated circuit for battery self-heating and DC charging.

[0038] In the embodiments of this application, the working principle of the energy storage module 120 and the battery pack 11 performing cyclic charging and discharging through the heating circuit 110 may include: when the battery pack is in discharge mode, the initial voltage on the first capacitor C1 and the energy storage module is low, the first switch T1 is turned on, the second switch T2 is turned off, and the working circuit is BAT1→T1→L1→C1 and BAT1→T1→L1→energy storage module, the first inductor L1 stores energy (the current direction is from the battery to the capacitor C1 and the energy storage module), the first capacitor C1 is charged, and the energy storage module 120 stores energy; when the first switch T1 is turned off, the second switch T2 is turned on, and the working circuit is L1→C1→T2 and L1→energy storage module→T2, the first inductor L1 releases energy, the first capacitor C1 is charged, and the energy storage module stores energy. During the discharge process, the energy storage module is always in the energy storage state, so the voltage on the energy storage module continuously increases. When the battery pack is in charging mode, the initial voltage on the first capacitor C1 and the energy storage module is relatively high. The first switch T1 is off, and the second switch T2 is on. The working circuit is C1→L1→T2 and energy storage module→L1→T2, with the first inductor L1 storing energy (current flows from the capacitor to the battery). When the first switch T1 is on and the second switch T2 is off, the working circuit is C1→L1→T1→BAT1 and energy storage module→L1→T1→BAT1. During charging, the energy storage module is constantly releasing energy, so the electrical energy stored in the energy storage module is transferred to the battery for charging. Thus, the energy storage module and the battery pack cyclically charge and discharge each other through a non-isolated bidirectional DC-DC converter. The generated AC current can generate heat from the internal resistance of the battery pack, thereby achieving self-heating of the battery pack. It should be noted that during the self-heating process, because the circuit generates AC current, the ripple generated by the switches is larger than that of unidirectional charging or discharging. Therefore, the energy storage module can better absorb the high-frequency ripple output by the converter, making the self-heating circuit more stable.

[0039] It is worth noting that the heating circuit can be a circuit composed of electronic devices such as switching transistors, inductors, capacitors, and transformers, and the energy storage module 120 can include a capacitor with energy storage function. For example, in the third embodiment, such as Figure 7 As shown, the energy storage module 120 includes a second capacitor C2. The heating circuit 110 may include: a first bridge arm composed of a third switch T3 and a fourth switch T4 connected in series, a second bridge arm composed of a fifth switch T5 and a sixth switch T6 connected in series, a third bridge arm composed of a seventh switch T7 and an eighth switch T8 connected in series, a fourth bridge arm composed of a ninth switch T9 and a tenth switch T10 connected in series, as well as a second inductor L2, a third inductor L3, a fourth inductor L4, a third capacitor C3, a fourth capacitor C4, and a transformer T. The first bridge arm is connected to the positive and negative terminals of the battery pack 11, respectively. The midpoint of the first bridge arm is connected to one end of the third inductor L3. The other end of the third inductor L3 is connected to one end of the primary side of the transformer T. The second bridge arm is connected to the positive and negative terminals of the battery pack 11, respectively. The midpoint of the second bridge arm is connected to the other end of the primary side of the transformer T through the third capacitor C3. One end of the secondary side of the transformer T is connected to the midpoint of the third bridge arm through the fourth capacitor C4. The other end of the secondary side of the transformer T is connected to the midpoint of the fourth bridge arm through the fourth inductor L4. The two ends of the third bridge arm are connected to the two ends of the fourth bridge arm. One end of the fourth bridge arm is connected to the terminal of the second inductor L2, and the other end of the fourth bridge arm is connected to the terminal of the second capacitor C2.

[0040] In the embodiments of this application, the working principle of the energy storage module 120 and the battery pack 11 performing cyclic charging and discharging through the heating circuit 110 may include: When the battery pack is in discharge mode, the third switch T3, the fourth switch T4, the fifth switch T5, and the sixth switch T6 operate at a fixed frequency, a fixed phase shift angle, or a fixed duty cycle, while the seventh switch T7, the eighth switch T8, the ninth switch T9, and the tenth switch T10 are all turned off or operate in synchronous rectification mode. In this case, the battery charges the second capacitor C2, and the voltage on the second capacitor C2 increases, thus continuously increasing the energy of the second capacitor C2. When the battery pack is in charging mode, the seventh switch T7, the eighth switch T8, the ninth switch T9, and the tenth switch T10 operate at a fixed frequency, a fixed phase shift angle, or a fixed duty cycle, while the third switch T3, the fourth switch T4, the fifth switch T5, and the sixth switch T6 are all turned off or operate in synchronous rectification mode. This causes the second capacitor C2 to charge the battery, and the voltage on the second capacitor C2 gradually decreases. Therefore, the second capacitor C2 and the battery pack are repeatedly charged and discharged by an isolated bidirectional DC-DC converter. The resulting alternating current can generate heat in the internal resistance of the battery pack, thereby achieving self-heating of the battery pack.

[0041] It should be noted that the heating circuit 110 may include an isolated bidirectional DC-DC converter. That is, the heating circuit can be constructed using an isolated bidirectional DC-DC converter and combined with an energy storage module to achieve self-heating of the battery pack. For example, in the fourth embodiment, as... Figure 8 As shown, the isolated bidirectional DC-DC converter 112 may include: a first bridge arm composed of a third switch T3 and a fourth switch T4 connected in series; a second bridge arm composed of a fifth switch T5 and a sixth switch T6 connected in series; a third bridge arm composed of a seventh switch T7 and an eighth switch T8 connected in series; a fourth bridge arm composed of a ninth switch T9 and a tenth switch T10 connected in series; a filter topology composed of a second inductor L2 and a second capacitor C2 connected in series; and a transformer T consisting of a third inductor L3, a fourth inductor L4, a third capacitor C3, a fourth capacitor C4, and a fourth capacitor C4. The energy storage module 120 includes an energy storage capacitor C. The first bridge arm is connected to the positive and negative terminals of the battery pack 11, respectively. The midpoint of the first bridge arm is connected to one end of the third inductor L3. The other end of the third inductor L3 is connected to one end of the primary side of the transformer T. The second bridge arm is connected to the positive and negative terminals of the battery pack 11, respectively. The midpoint of the second bridge arm is connected to the other end of the primary side of the transformer T through the third capacitor C3. One end of the secondary side of the transformer T is connected to the midpoint of the third bridge arm through the fourth capacitor C4. The other end of the secondary side of the transformer T is connected to the midpoint of the fourth bridge arm through the fourth inductor L4. The two ends of the third bridge arm are connected to the two ends of the fourth bridge arm. One end of the fourth bridge arm is connected to the second inductor L2 of the filter topology, and the other end of the fourth bridge arm is connected to the second capacitor C2 of the filter topology.

[0042] In the fourth embodiment, the energy storage module may include either an energy storage capacitor or a DC charging pile. For example, when the energy storage module is an energy storage capacitor, such as... Figure 8 The diagram shows the circuit structure of the energy storage capacitor 121 and the isolated bidirectional DC / DC converter 112. Specifically, the energy storage capacitor 121 is connected in parallel to the second capacitor C2 in the isolated bidirectional DC / DC converter 112. In other words, by adding an energy storage capacitor outside the isolated bidirectional DC / DC converter, this isolated bidirectional DC / DC converter can be a bidirectional DC / DC module in a DC charging circuit. For example, when the energy storage module is a DC charging pile, such as... Figure 9 The diagram shows the circuit structure of the DC charging pile 122 and the isolated bidirectional DC-DC converter 112. The DC charging pile 122 is connected in parallel to the second capacitor C2 in the isolated bidirectional DC-DC converter 112. It can be seen that this isolated bidirectional DC-DC converter is integrated with the bidirectional DC / DC module for DC charging, forming an integrated circuit for battery self-heating and DC charging.

[0043] In the embodiments of this application, the working principle of the energy storage module 120 and the battery pack 11 performing cyclic charging and discharging through the heating circuit 110 may include: when the battery pack is in discharge mode, the third switch T3, the fourth switch T4, the fifth switch T5 and the sixth switch T6 operate at a fixed frequency, a fixed phase shift angle or a fixed duty cycle, and the seventh switch T7, the eighth switch T8, the ninth switch T9 and the tenth switch T10 are all turned off or operate in synchronous rectification mode, then the battery charges the energy storage module, the electrical energy on the energy storage module gradually increases, and the voltage on the energy storage module rises. When the battery pack is in charging mode, switches T7, T8, T9, and T10 operate at a fixed frequency, fixed phase shift angle, or fixed duty cycle. Switches T3, T4, T5, and T6 are all off or operating in synchronous rectification mode. The energy storage module releases energy, meaning the electrical energy on the energy storage module is transferred to the battery pack side to charge the battery, causing a voltage drop on the energy storage module. Thus, the energy storage module and the battery pack cyclically charge and discharge each other through an isolated bidirectional DC-DC converter. The resulting AC current generates heat within the battery pack's internal resistance, achieving self-heating of the battery pack.

[0044] In order to enable the energy storage module and the battery pack to repeatedly charge and discharge each other to generate the AC current required for battery pack self-heating, in some embodiments of this application, the controller 130 can control the driving of the heating circuit to regulate the frequency and amplitude of the battery pack charging and discharging current, thereby enabling the energy storage module and the battery pack to repeatedly charge and discharge each other to generate the AC current required for battery pack self-heating, thereby controlling the heat generation of the battery's internal resistance and achieving the purpose of battery self-heating.

[0045] Figure 10 This is an example diagram illustrating the relationship between the frequency of the alternating current and the effective value of the alternating current at the lithium plating critical point according to an embodiment of this application. Figure 10 As shown, the AC parameters are determined with non-lithium deposition as the boundary. Taking a lithium battery as an example, in... Figure 10 The horizontal axis represents the AC current frequency during battery pack charging and discharging, and the vertical axis represents the maximum effective value of the AC current during battery pack charging and discharging. It can be understood that, to ensure battery safety and durability, when controlling the heating circuit's drive via a controller to regulate the AC current frequency and effective value during battery charging and discharging, the following should be followed: Figure 10 The AC current frequency and RMS value are shown within the safe zone. In other words, it can be seen from... Figure 10 Within the safe zone of the battery, the frequency and effective value of the AC current during battery charging and discharging are obtained. The controller then controls the heating circuit to ensure that the frequency and effective value of the AC current during the charging and discharging process of the battery pack fall within a certain range. Figure 10Within the safe zone. The frequency of alternating current and the alternating current itself.

[0046] To ensure circuit safety and effectively control the heating of the battery pack by the heating circuit, in one embodiment of this application, such as... Figure 2 As shown, the current self-heating device 100 may further include a switch module 140. The switch module 140 is connected to both the battery pack 11 and the heating circuit 110. In an embodiment of this application, the controller 130 may close the switch module 140 and activate the heating circuit 110 to self-heat the battery pack 11 when it detects that the temperature of the battery pack 11 is below a first threshold and determines that the battery management system allows battery heating; when it detects that the temperature of the battery pack 11 is above a second threshold and / or determines that the battery management system prohibits battery heating, it may stop the heating circuit and disconnect the switch module 140; wherein the first threshold is less than the second threshold.

[0047] As an example, controller 130 communicates with the battery management system (BMS) to obtain information such as the temperature, SOC, and voltage of the battery pack 11, and determines whether the battery is allowed to charge and discharge. For instance, if controller 130 obtains the current temperature of the battery pack 11 through the BMS and detects that the current temperature of the battery pack 11 is lower than a first threshold, and if the BMS allows the battery to heat up at this time, then switch module 140 can be closed and heating circuit 110 can be started to self-heat the battery pack 11. For example, when the controller 130 obtains the current temperature of the battery pack 11 through the battery management system and detects that the current temperature of the battery pack 11 is greater than the second threshold, it needs to control the heating circuit 110 to stop working and disconnect the switch module 140; or, when the controller 130 determines that the battery management system prohibits battery heating, it controls the heating circuit 110 to stop working and disconnects the switch module 140; or, when the controller 130 detects that the current temperature of the battery pack 11 is greater than the second threshold and determines that the battery management system prohibits battery heating, it controls the heating circuit 110 to stop working and disconnects the switch module 140.

[0048] In other words, such as Figure 11As shown, the controller 130 can obtain the current temperature of the battery pack 11 through the battery management system and detect whether the current temperature of the battery pack 11 is lower than a first threshold. If not, it exits the self-heating process. If the current temperature of the battery pack 11 is detected to be lower than the first threshold, it needs to determine whether the current battery allows charging and discharging heating. If not, the heating circuit remains in a stopped state. If it is determined that the current battery allows charging and discharging heating, the switch module 140 is closed, and the heating circuit 110 is started to self-heat the battery pack 11. During the self-heating process of the battery pack 11 using the heating circuit 110, the controller 130 can detect whether the current temperature of the battery pack 11 is higher than a second threshold. If not, it continues to return to the above step of determining whether the current battery allows charging and discharging heating. If the current temperature of the battery pack 11 is detected to be higher than the second threshold, the heating circuit 110 is controlled to stop working, and the switch module 140 is disconnected, exiting the self-heating process of the battery self-heating device.

[0049] In one embodiment of this application, the heating circuit 110 may include a bidirectional DC-DC converter. As an example, the bidirectional DC-DC converter can serve as a medium for energy exchange between the energy storage module 120 and the battery pack 11. The controller 130 controls the energy flow direction of the bidirectional DC-DC converter to generate an alternating current of a certain frequency and amplitude on the battery pack 11 side. This alternating current flowing through the battery pack 11 can be used to heat the battery pack 11. In this embodiment, the controller 130 can control the energy flow direction of the bidirectional DC-DC converter to generate an alternating current on the battery pack 11 side based on the duty cycle of the bidirectional DC-DC converter, so that the alternating current flowing through the battery pack is used to heat the battery pack.

[0050] In the embodiments of this application, the controller can adjust the duty cycle of the bidirectional DC-DC converter by controlling the switch in the bidirectional DC-DC converter, and then control the energy flow direction of the bidirectional DC-DC converter to generate alternating current on the battery pack side based on the duty cycle of the bidirectional DC-DC converter, so that the alternating current flowing through the battery pack is used to heat the battery pack.

[0051] According to the battery self-heating device of this application embodiment, a heating circuit and an energy storage module can be connected to the battery pack port. The heating circuit is set between the energy storage module and the battery pack, so that the energy storage module and the battery pack can perform cyclic charging and discharging of each other through the heating circuit. The generated alternating current causes the internal resistance of the battery pack to generate heat, thereby achieving the effect of battery self-heating. As a result, the battery temperature rises from the inside to the outside due to the heat generated by the internal resistance of the battery pack. This can greatly shorten the battery heating time in cold environments and enable the battery to restore its charging capacity in a short time.

[0052] To achieve the above embodiments, this application also proposes a control method for a battery self-heating device. It should be noted that the structural and functional descriptions of the battery self-heating device in this application's embodiments can be found in the descriptions of the foregoing embodiments, and will not be repeated here. Specifically, in the embodiments of this application, the control method for the battery self-heating device may include: when the temperature of the battery pack is detected to be below a first threshold and it is determined that the battery management system allows battery heating, activating a heating circuit to self-heat the battery pack; when the temperature of the battery pack is detected to be above a second threshold, and / or it is determined that the battery management system prohibits battery heating, stopping the heating circuit; wherein the second threshold is greater than the first threshold.

[0053] In one embodiment of this application, the heating circuit includes a bidirectional DC-DC converter, which can be a non-isolated bidirectional DC-DC converter or an isolated bidirectional DC-DC converter. Specifically, in this embodiment, the process of the heating circuit activating the self-heating of the battery pack can be as follows: Based on the duty cycle of the bidirectional DC-DC converter, the energy flow direction of the bidirectional DC-DC converter is controlled to generate an alternating current on the battery pack side, so that the alternating current flowing through the battery pack is used to heat the battery pack. As an example, the duty cycle of the bidirectional DC-DC converter can be adjusted by controlling the switch in the bidirectional DC-DC converter, and then, based on the duty cycle of the bidirectional DC-DC converter, the energy flow direction of the bidirectional DC-DC converter is controlled to generate an alternating current on the battery pack side, so that the alternating current flowing through the battery pack is used to heat the battery pack.

[0054] For example, taking a non-isolated bidirectional DC-DC converter as an example, the battery voltage U matched to the bidirectional DC-DC converter can be used as a reference. bat (For example, the rated value can be calculated based on a single-cell voltage of 3.2V, or the current battery voltage value can be read by communicating with the BMS, or the battery voltage value can be sampled by an external power sensor.) See reference. Figure 10 Obtain the effective value I of the alternating current within the safe area. bat Given the frequency f, the maximum duty cycle D of the bidirectional DC-DC converter can be theoretically calculated. max and minimum value D min This enables the control of the bidirectional DC-DC converter. A waveform diagram illustrating the duty cycle of the bidirectional DC-DC converter in relation to the energy storage module voltage and the battery charging / discharging current is shown below. Figure 12 As shown.

[0055] It should be noted that the duty cycle boundary of the bidirectional DC-DC converter (i.e., the boundary formed by the maximum and minimum duty cycles) can be fixed or updated in real time. For example, if the battery voltage is not acquired, the duty cycle boundary of the bidirectional DC-DC converter can be determined to be a fixed duty cycle boundary; if the battery voltage is acquired, the duty cycle boundary of the bidirectional DC-DC converter can be determined to be a real-time updated duty cycle boundary. Based on this characteristic, the above-described step of controlling the energy flow direction of the bidirectional DC-DC converter based on its duty cycle can be implemented in two ways. Figure 13 The control flow shown is the control flow diagram of the bidirectional DC-DC converter when the battery voltage is not acquired; Figure 14 The control flow shown is the control flow diagram of the bidirectional DC-DC converter when acquiring the battery voltage.

[0056] As an example of a possible implementation, such as Figure 13 As shown, the specific implementation process of controlling the energy flow direction of the bidirectional DC-DC converter based on its duty cycle can include:

[0057] Step 1301: Control the bidirectional DC-DC converter to operate in discharge mode so that the battery pack charges the energy storage module.

[0058] Step 1302: Determine the voltage duty cycle D of the bidirectional DC-DC converter. uty During this process, the bidirectional DC-DC converter operates in discharge mode, and its duty cycle increases linearly to enable the battery pack to charge the energy storage module.

[0059] Step 1303: Detect the duty cycle D of the bidirectional DC-DC converter. uty Is it greater than or equal to the maximum duty cycle D? max In other words, during the linear increase of the duty cycle of the bidirectional DC-DC converter, it is necessary to detect whether the duty cycle of the bidirectional DC-DC converter is greater than or equal to the maximum duty cycle. If the detected duty cycle of the bidirectional DC-DC converter is less than the maximum duty cycle, the linear increase of the duty cycle of the bidirectional DC-DC converter can continue.

[0060] Step 1304, after detecting the duty cycle D of the bidirectional DC-DC converter uty Greater than or equal to the maximum duty cycle D max At this time, the bidirectional DC-DC converter is controlled to operate in charging mode so that the energy storage module can charge the battery pack.

[0061] Step 1305: Determine the duty cycle D of the bidirectional DC-DC converter. uty During this process, the bidirectional DC-DC converter operates in charging mode, and its duty cycle decreases linearly to enable the energy storage module to charge the battery pack.

[0062] Step 1306: Detect the duty cycle D of the bidirectional DC-DC converter. uty Is it less than or equal to the minimum duty cycle D? min In other words, during the linear decrease of the duty cycle of the bidirectional DC-DC converter, it is necessary to detect whether the duty cycle of the bidirectional DC-DC converter is less than or equal to the minimum duty cycle. If the duty cycle of the bidirectional DC-DC converter is detected to be greater than the minimum duty cycle, then the linear decrease of the duty cycle of the bidirectional DC-DC converter continues.

[0063] In the embodiments of this application, when the duty cycle D of the bidirectional DC-DC converter is detected... uty Less than or equal to the minimum duty cycle D min If the time is right, return to the step of controlling the bidirectional DC-DC converter to operate in discharge mode so that the battery pack charges the energy storage module, that is, return to step 1301.

[0064] Therefore, the direction of energy flow in the bidirectional DC-DC converter is controlled by linearly increasing or decreasing the duty cycle of the converter.

[0065] As an example of another possible implementation, such as Figure 14 As shown, the specific implementation process of controlling the energy flow direction of the bidirectional DC-DC converter based on its duty cycle can include:

[0066] Step 1410: Obtain the battery pack voltage. That is, the battery pack voltage U can be acquired. bat .

[0067] Step 1420: Calculate the maximum duty cycle D of the bidirectional DC-DC converter based on the battery pack voltage and the maximum voltage of the energy storage capacitor. max Based on the battery pack voltage and the minimum voltage of the energy storage capacitor, the minimum duty cycle D of the bidirectional DC-DC converter is calculated. min .

[0068] For example, taking a non-isolated bidirectional DC-DC converter as an example, the battery voltage U matched to the bidirectional DC-DC converter can be used as a reference. bat (For example, the rated value can be calculated based on a single-cell voltage of 3.2V, or the current battery voltage value can be read by communicating with the BMS, or the battery voltage value can be sampled by an external power sensor.) Reference Figure 10 Obtain the effective value I of the alternating current within the safe area. bat Given the frequency f, the maximum duty cycle D of the bidirectional DC-DC converter can be theoretically calculated. max and minimum value D minThis enables the control of the bidirectional DC-DC converter. A waveform diagram illustrating the duty cycle of the bidirectional DC-DC converter in relation to the energy storage module voltage and the battery charging / discharging current is shown below. Figure 12 As shown.

[0069] Assuming the energy storage module is a capacitor with a capacitance of C0, the theoretical calculation process is as follows:

[0070] The battery pack's self-heating power is:

[0071] P bat =U bat *I bat

[0072] Among them, P bat This refers to the battery pack's self-heating power; U bat Battery pack voltage; I bat To obtain the effective value of the alternating current within the safe area.

[0073] The power of the energy storage capacitor is:

[0074] P c =fC o (U max 2 -U min 2 )

[0075] Among them, P c is the power of the energy storage capacitor; f is the frequency of the alternating current (i.e., the number of times the energy storage capacitor is charged and discharged within 1 second).

[0076] Assuming the efficiency of the bidirectional DC-DC converter is η, based on the power conservation of the bidirectional DC-DC converter, energy storage capacitor, and battery pack, we obtain:

[0077]

[0078] Where f is the frequency of the alternating current (i.e., the number of times the energy storage capacitor is charged and discharged within 1 second), C0 is the capacitance of the energy storage capacitor, and U max U is the maximum voltage of the energy storage capacitor. min U is the minimum voltage of the energy storage capacitor. bat η is the battery pack voltage, and η is the efficiency of the bidirectional DC-DC converter.

[0079] In theory, U min The minimum value is 0, U max The maximum value is U bat To avoid damage to the capacitor due to reverse voltage, a certain margin can be left, such as U. min =k*U bat k = 0 to 0.5.

[0080] Taking k = 0.5, the maximum voltage U of the energy storage capacitor can be calculated using the above formula. max and minimum value U min , if U max <U bat If U max ≥U bat If k = 0.4, then continue the calculation until the design requirements are met.

[0081] The input and output voltages of the bidirectional DC-DC converter in continuous mode satisfy the following relationship:

[0082]

[0083]

[0084] The maximum duty cycle D of a bidirectional DC-DC converter can be calculated using the above formula. max and minimum duty cycle D min .

[0085] The duty cycle curve of a suitable bidirectional DC-DC converter is obtained through calculation.

[0086] Step 1430: Control the bidirectional DC-DC converter to operate in discharge mode so that the battery pack charges the energy storage module.

[0087] Step 1440: Determine the duty cycle D of the bidirectional DC-DC converter. uty During this process, the bidirectional DC-DC converter operates in discharge mode, and its duty cycle increases linearly to enable the battery pack to charge the energy storage module.

[0088] Step 1450: Detect the duty cycle D of the bidirectional DC-DC converter. uty Is it greater than or equal to the maximum duty cycle D? max In other words, during the linear increase of the duty cycle of the bidirectional DC-DC converter, it is necessary to detect whether the duty cycle of the bidirectional DC-DC converter is greater than or equal to the maximum duty cycle. If the detected duty cycle of the bidirectional DC-DC converter is less than the maximum duty cycle, the linear increase of the duty cycle of the bidirectional DC-DC converter can continue.

[0089] Step 1460, after detecting the duty cycle D of the bidirectional DC-DC converter uty Greater than or equal to the maximum duty cycle D of the bidirectional DC-DC converter max At this time, the bidirectional DC-DC converter is controlled to operate in charging mode so that the energy storage module can charge the battery pack.

[0090] Step 1470: Determine the duty cycle D of the bidirectional DC-DC converter. utyDuring this process, the bidirectional DC-DC converter operates in charging mode, and its duty cycle decreases linearly to enable the energy storage module to charge the battery pack.

[0091] Step 1480: Detect the duty cycle D of the bidirectional DC-DC converter. uty Is it less than or equal to the minimum duty cycle D? min In other words, during the linear decrease of the duty cycle of the bidirectional DC-DC converter, it is necessary to detect whether the duty cycle of the bidirectional DC-DC converter is less than or equal to the minimum duty cycle. If the duty cycle of the bidirectional DC-DC converter is detected to be greater than the minimum duty cycle, then the linear decrease of the duty cycle of the bidirectional DC-DC converter continues.

[0092] In the embodiments of this application, when the duty cycle D of the bidirectional DC-DC converter is detected... uty Less than or equal to the minimum duty cycle D of a bidirectional DC-DC converter min If the voltage of the battery pack is obtained, return to step 1410.

[0093] Therefore, the direction of energy flow in the bidirectional DC-DC converter is controlled by linearly increasing or decreasing the duty cycle of the converter.

[0094] According to the control method of the battery self-heating device in the embodiments of this application, the frequency and amplitude of the battery charging and discharging current can be adjusted by controlling the drive of the bidirectional DC-DC converter, thereby controlling the heat generation of the battery internal resistance and achieving the effect of battery self-heating. This causes the battery temperature to rise from the inside to the outside due to the heat generated by the internal resistance of the battery pack, which can greatly shorten the battery heating time in cold environments and enable the battery to restore its charging capacity in a short time.

[0095] To implement the above embodiments, this application also proposes a vehicle.

[0096] Figure 15 This is a structural block diagram of a vehicle according to one embodiment of this application. Figure 15 As shown, the vehicle 1500 may include a battery self-heating device 100. It is understood that the structural and functional descriptions of the battery self-heating device in this application embodiment can be found in the structural and functional descriptions of the battery self-heating device in the foregoing embodiments, and will not be repeated here.

[0097] In the description of this application, it should be understood that the terms "first," "second," "third," "fourth," "fifth," "sixth," "seventh," "eighth," "ninth," and "tenth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," "third," "fourth," "fifth," "sixth," "seventh," "eighth," "ninth," and "tenth" may explicitly or implicitly include at least one of those features.

[0098] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0099] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0100] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A battery self-heating device, characterized by, include: A heating circuit, which is connected to the battery pack; An energy storage module is connected to the heating circuit, wherein the heating circuit is disposed between the energy storage module and the battery pack; The energy storage module and the battery pack are repeatedly charged and discharged by each other through the heating circuit, and the resulting alternating current causes the internal resistance of the battery pack to generate heat. A controller, connected to the heating circuit, is used to control the driving of the heating circuit so that the energy storage module and the battery pack can perform cyclic charging and discharging to generate the AC current required for the battery pack to self-heat. A switching module, which is connected to both the battery pack and the heating circuit; The controller is specifically configured to: close the switch module and start the heating circuit to self-heat the battery pack when the temperature of the battery pack is detected to be lower than a first threshold and it is determined that the battery management system allows battery heating; and stop the heating circuit and disconnect the switch module when the temperature of the battery pack is detected to be higher than a second threshold and / or it is determined that the battery management system prohibits battery heating; wherein the first threshold is less than the second threshold. The heating circuit includes a bidirectional DC-DC converter. When the temperature of the battery pack is detected to be lower than a first threshold and it is determined that the battery management system allows the battery to heat up, the bidirectional DC-DC converter is controlled to generate an alternating current on the battery pack side based on the duty cycle of the bidirectional DC-DC converter, so that the alternating current is used to heat the battery pack when it flows through the battery pack. Based on the duty cycle of the bidirectional DC-DC converter, controlling the energy flow direction of the bidirectional DC-DC converter includes: The bidirectional DC-DC converter is controlled to operate in discharge mode so that the battery pack charges the energy storage module. Determine the duty cycle of the bidirectional DC-DC converter; When the duty cycle of the bidirectional DC-DC converter is detected to be greater than or equal to the maximum duty cycle, the bidirectional DC-DC converter is controlled to operate in charging mode so that the energy storage module charges the battery pack. When the duty cycle of the bidirectional DC-DC converter is detected to be less than or equal to the minimum duty cycle, the process returns to the step of controlling the bidirectional DC-DC converter to operate in discharge mode so that the battery pack charges the energy storage module. The heating circuit includes: an isolated bidirectional DC-DC converter; wherein the isolated bidirectional DC-DC converter includes: a first bridge arm composed of a third switch T3 and a fourth switch T4 connected in series; a second bridge arm composed of a fifth switch T5 and a sixth switch T6 connected in series; a third bridge arm composed of a seventh switch T7 and an eighth switch T8 connected in series; a fourth bridge arm composed of a ninth switch T9 and a tenth switch T10 connected in series; a filter topology composed of a second inductor L2 and a second capacitor C2 connected in series; and a transformer T consisting of a third inductor L3, a fourth inductor L4, a third capacitor C3, a fourth capacitor C4, and a third capacitor C4. The first bridge arm has its two ends connected to the positive and negative ends of the battery pack, respectively. The midpoint of the half-bridge of the first bridge arm is connected to one end of the third inductor L3. The other end of the third inductor L3 is connected to one end of the primary side of the transformer T. The second bridge arm has its two ends connected to the positive and negative ends of the battery pack, respectively. The midpoint of the half-bridge of the second bridge arm is connected to the other end of the primary side of the transformer T through the third capacitor C3. One end of the secondary side of the transformer T is connected to the midpoint of the half-bridge of the third bridge arm through the fourth capacitor C4. The other end of the secondary side of the transformer T is connected to the midpoint of the half-bridge of the fourth bridge arm through the fourth inductor L4. The two ends of the third bridge arm are connected to the two ends of the fourth bridge arm. One end of the fourth bridge arm is connected to the inductor L2 of the filter topology, and the other end of the fourth bridge arm is connected to the capacitor C2 of the filter topology. The energy storage module is connected in parallel with the second capacitor C2. The energy storage module includes either an energy storage capacitor or a DC charging pile; the isolated bidirectional DC-DC converter is a bidirectional DC / DC module in the DC charging circuit.

2. A control method of the battery self-heating device according to claim 1, characterized by, Includes the following steps: When the temperature of the battery pack is detected to be below a first threshold and it is determined that the battery management system allows the battery to heat up, the heating circuit is activated to self-heat the battery pack.

3. The control method of the battery self-heating device according to claim 2, characterized by, The method further includes: When the temperature of the battery pack is detected to be greater than a second threshold, and / or when it is determined that the battery management system prohibits battery heating, the heating circuit is stopped; wherein the second threshold is greater than the first threshold.

4. The control method of the battery self-heating device according to claim 2, characterized by, The heating circuit includes a bidirectional DC-DC converter; wherein, the start-up heating circuit self-heats the battery pack, including: Based on the duty cycle of the bidirectional DC-DC converter, the energy flow direction of the bidirectional DC-DC converter is controlled to generate an alternating current on the battery pack side, so that the alternating current is used to heat the battery pack when it flows through the battery pack.

5. The control method of the battery self-heating device according to claim 4, characterized by, Based on the duty cycle of the bidirectional DC-DC converter, controlling the energy flow direction of the bidirectional DC-DC converter includes: The bidirectional DC-DC converter is controlled to operate in discharge mode so that the battery pack charges the energy storage module. Determine the duty cycle of the bidirectional DC-DC converter; When the duty cycle of the bidirectional DC-DC converter is detected to be greater than or equal to the maximum duty cycle, the bidirectional DC-DC converter is controlled to operate in charging mode so that the energy storage module charges the battery pack. When the duty cycle of the bidirectional DC-DC converter is detected to be less than or equal to the minimum duty cycle, the process returns to the step of controlling the bidirectional DC-DC converter to operate in discharge mode so that the battery pack charges the energy storage module.

6. The control method for the battery self-heating device according to claim 4, characterized in that, Based on the duty cycle of the bidirectional DC-DC converter, controlling the energy flow direction of the bidirectional DC-DC converter includes: Obtain the voltage of the battery pack; The maximum duty cycle of the bidirectional DC-DC converter is calculated based on the voltage of the battery pack and the maximum voltage of the energy storage capacitor. The minimum duty cycle of the bidirectional DC-DC converter is calculated based on the voltage of the battery pack and the minimum voltage of the energy storage capacitor. When the duty cycle of the bidirectional DC-DC converter is detected to be greater than or equal to the maximum duty cycle of the bidirectional DC-DC converter, the bidirectional DC-DC converter is controlled to operate in charging mode so that the energy storage module charges the battery pack. If the duty cycle of the bidirectional DC-DC converter is detected to be less than or equal to the minimum duty cycle of the bidirectional DC-DC converter, the process returns to the step of obtaining the voltage of the battery pack.

7. A vehicle, characterized in that, include: The battery self-heating device as described in claim 1.

Images