Inverter integrated device and use control method thereof

Abstract

The application relates to the technical field of power battery heating and fast charging, and discloses an inverter integrated device, which comprises a direct-current charging interface connected with a direct-current charging pile and a lithium battery pack arranged on an electric vehicle, the direct-current charging interface is connected with the lithium battery pack through a mode switching switch, the lithium battery pack is connected with the direct-current charging interface, three groups of inverter groups are connected in parallel on the lithium battery pack, each inverter group comprises two complementary switch tubes connected in series, the direct-current charging interface is connected with a motor stator winding, each phase of the motor stator winding is connected with the midpoint of one inverter group, the mode switching switch, the complementary switch tubes and the direct-current charging pile are connected with a control unit, and the control unit is connected with a detection unit. The application further discloses a use control method of the inverter integrated device. The inverter integrated device and the use control method thereof realize the function of simultaneously heating and charging the lithium battery pack in a low-temperature environment, and improve the fast charging speed of the lithium battery pack in the low-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of power battery heating and fast charging technology, specifically to an integrated inverter device and its usage control method. Background Technology

[0002] In recent years, environmental problems have become increasingly severe, leading to the rapid development of electric vehicles (EVs). Lithium-ion batteries, due to their high energy density, environmental friendliness, and lack of memory effect, have become the preferred power source for electric vehicles. However, in low-temperature environments, battery capacity decreases significantly, and internal resistance increases considerably. Furthermore, lithium plating is prone to occur during charging, eventually forming lithium dendrites, which can lead to thermal runaway and safety hazards in severe cases. For users in cold regions, such as Northeast my country, gasoline vehicles are often preferred over electric vehicles. To protect the environment and alleviate environmental and energy crises, the widespread promotion of electric vehicles and other new energy vehicles is essential. To ensure user safety and a positive user experience, and to facilitate the promotion of electric vehicles in cold regions, the current method for electric vehicles involves preheating the lithium-ion batteries before charging.

[0003] Extensive research has been conducted on low-temperature heating of lithium batteries. Existing methods for preheating lithium-ion batteries include internal and external heating. Common external heating methods include electric heating film heating, air heating, and water heating. However, these methods require contact conduction, air convection, and liquid heat transfer to heat the battery. Heating through heat conduction is inefficient, and uneven heating over time leads to severe battery life degradation. More commonly used internal heating methods include high-frequency pulse and high-frequency AC heating. These methods use soft switching and power electronics technology to design heating circuits that allow the battery pack to generate high-frequency pulses or high-frequency AC to heat itself. However, due to the limitations of their preheating rate, a relatively long preheating period must be waited for before charging can begin. This adds an extra preheating stage before charging, which is significantly longer than fast charging or refueling time in a regular gasoline car, greatly impacting charging time and user experience.

[0004] To improve the fast charging speed of lithium-ion battery packs in low-temperature environments, and to make them suitable for all electric vehicles, with both DC and AC charging stations enabling fast charging, allowing electric vehicles to be conveniently used in cold weather and regions, an integrated device was designed that allows electric vehicles to simultaneously heat and charge. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the above-mentioned technologies by providing an inverter integrated device and its usage control method, which realizes the function of simultaneous heating and charging of lithium battery packs in low-temperature environments, thereby improving the fast charging speed of lithium battery packs in low-temperature environments.

[0006] To achieve the above objectives, the inverter integrated device of the present invention includes a DC charging interface connected to a DC charging pile and a lithium battery pack mounted on an electric vehicle. The positive terminal of the DC charging interface is connected to the positive terminal of the lithium battery pack via a mode switching switch, and the negative terminal of the lithium battery pack is connected to the negative terminal of the DC charging interface. Three inverter groups are connected in parallel on the lithium battery pack, and each inverter group includes two complementary switching transistors connected in series. The positive terminal of the DC charging interface is connected to a motor stator winding, and each phase of the motor stator winding is connected to the midpoint of one of the inverter groups. The mode switching switch, the complementary switching transistors, and the DC charging pile are all connected to a control unit. The control unit is connected to a detection unit, which is connected to the lithium battery pack and the motor stator winding.

[0007] Preferably, the DC charging interface is connected to an on-board charger, the on-board charger is connected to the control unit, the on-board charger is connected to an AC charging interface, and the AC charging interface is connected to an AC charging pile.

[0008] A method for controlling the use of the inverter integrated device, wherein when the electric vehicle is ready to charge, the detection unit detects the real-time temperature of the lithium battery pack and transmits it to the control unit, the control unit compares the real-time battery temperature with a preset temperature threshold, and if the real-time battery temperature is higher than the preset temperature threshold, it enters the normal fast charging mode, the control unit communicates with the DC charging pile through the CAN low-voltage bus to switch the DC charging pile to the normal fast charging state, the control unit controls the mode switching switch to close and turns off the complementary switching transistors in the three sets of inverter groups;

[0009] If the real-time battery temperature is lower than the preset temperature threshold, it enters the low-temperature charging mode. The control unit interacts with the DC charging pile through low-voltage communication via the CAN bus, causing the DC charging pile to switch to constant voltage mode and control the mode switching switch to open. At the same time, it controls the switching of the complementary switching transistors in the three sets of inverters to generate high-frequency pulse current to heat and charge the lithium battery pack until the lithium battery pack is heated to the preset temperature threshold, and then enters the normal fast charging mode.

[0010] Preferably, the DC charging interface is connected to an on-board charger, the on-board charger is connected to the control unit, the on-board charger is connected to an AC charging interface, and the AC charging interface is connected to an AC charging pile. When the electric vehicle is ready to charge, the detection unit detects the real-time temperature of the lithium battery pack and transmits it to the control unit. The control unit compares the real-time battery temperature with a preset temperature threshold. If the real-time battery temperature is higher than the preset temperature threshold, it enters the normal fast charging mode. The control unit controls the on-board charger to be in constant voltage charging mode. The mode switching switch is closed, and the complementary switching transistors in the three sets of inverter groups are turned off.

[0011] If the real-time battery temperature is lower than the preset temperature threshold, the system enters a low-temperature charging mode. The control unit controls the on-board charger to be in constant-voltage charging mode and controls the mode switching switch to be turned off. At the same time, it controls the switching of the complementary switching transistors in the three inverter groups to generate a high-frequency pulse current to heat and charge the lithium battery pack until the lithium battery pack is heated to the preset temperature threshold, and then enters the normal fast charging mode.

[0012] Preferably, when entering the low-temperature charging mode, the control unit controls the mode switching switch to open, the complementary switch in the inverter group connected to the positive terminal of the DC charging interface to open, and the complementary switch connected to the negative terminal of the DC charging interface to close. Current flows from the positive terminal of the DC charging interface through the motor stator winding and the complementary switch connected to the negative terminal of the DC charging interface, returning to the negative terminal of the DC charging interface. At this time, the inductor current value of the motor stator winding gradually increases; this state is the inductor energy storage state. The detection unit continuously detects the inductor current value of the motor stator winding and transmits it to the control unit. When the inductor current value of the motor stator winding rises to the upper limit of the amplitude parameter I... LH When the control unit controls the complementary switch connected to the positive terminal of the DC charging interface in the inverter group to close, and the complementary switch connected to the negative terminal of the DC charging interface to open, the inductor current value of the motor stator winding gradually decreases. This state is the inductor energy release state. When the inductor current value of the motor stator winding decreases to the lower limit of the amplitude parameter I... LL When the control unit switches to inductive energy storage mode, it repeatedly switches to generate high-frequency pulse current to heat and charge the lithium battery pack.

[0013] Preferably, the pulse amplitude and frequency of the high-frequency pulse current are determined by the upper limit I of the amplitude parameter of the inductance current value of the motor stator winding. LH and amplitude parameter lower limit I LL Controlling the temperature can save time during low-temperature charging and reduce the risk of lithium degradation during low-temperature charging of lithium battery packs.

[0014] Preferably, the method for calculating the pulse amplitude and frequency of the high-frequency pulse current includes the following steps:

[0015] A) Input pulse current amplitude boundary I under different temperatures, different SOCs, and different SOHs set and frequency f set A table of lithium plating boundary and high-frequency pulse temperature rise characteristics was obtained;

[0016] B) Obtain the upper limit I of the amplitude parameter of the inductance current value of the motor stator winding. LH Real-time battery temperature, SOC, and SOH;

[0017] C) Set the upper limit of the amplitude parameter I LH The battery's real-time temperature, SOC, and SOH are input into the lithium plating boundary table and the high-frequency pulse temperature rise characteristic table to obtain the lithium plating boundary and the corresponding frequency boundary f in the high-frequency pulse temperature rise characteristic table. LH ;

[0018] D) Calculate and obtain the frequency boundary:

[0019]

[0020] In the formula, R is the total circuit impedance, L is the inductance of the motor stator winding, and U is the voltage of the lithium battery pack;

[0021] E) If X is the precision coefficient; proceed to step F).

[0022] F) Locate the corresponding f(I) in the table of lithium plating boundary and high-frequency pulse temperature rise characteristics. LH ,I LL Amplitude boundary I set , let I LH =I set f LH =f(I LH ,I LL It enters low-temperature charging mode;

[0023] G) The detection unit continuously detects the real-time temperature of the lithium battery pack. When the temperature rise ΔT is less than t, it continues to maintain the low-temperature charging mode. Whenever the temperature rise ΔT reaches t, it returns to step B) until the real-time battery temperature is greater than or equal to the temperature threshold Y, and then enters the normal fast charging mode.

[0024] H) Locate the corresponding f(I) in the table of lithium plating boundary and high-frequency pulse temperature rise characteristics. LH ,I LL Amplitude boundary I set , let I LH =(I set +I LH ) / 2, return to step C).

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. The low-temperature fast charging method adopted is high-frequency pulse charging. Under high-frequency pulses, the battery has low internal resistance and low polarization voltage, which allows for charging with a larger current without lithium plating, thus shortening the overall charging time in low-temperature environments.

[0027] 2. The heating method is internal preheating, which utilizes the internal resistance of the lithium battery pack to generate heat. Compared with external heating methods, this improves the thermoelectric conversion efficiency and temperature rise rate, thus enabling the lithium battery pack to generate a faster temperature rise while charging.

[0028] 3. The charging method can be switched in time according to the temperature of the lithium battery pack to achieve ultra-fast charging without damaging the battery life;

[0029] 4. The magnitude and frequency of the high-frequency DC pulse current can be adjusted in real time according to the battery temperature and the battery state of charge, which can save low-temperature charging time and reduce the risk of lithium degradation during low-temperature charging of lithium battery packs.

[0030] 5. No additional hardware is required, the cost is low and it is easy to implement, and it is suitable for various charging piles, including AC charging piles, 400V DC charging piles and 800V DC charging piles. Attached Figure Description

[0031] Figure 1 This is a circuit diagram of the inverter integrated device of the present invention applicable to DC charging piles;

[0032] Figure 2 This is a circuit diagram of the inverter integrated device of the present invention applicable to AC charging piles;

[0033] Figure 3 This is a schematic diagram of the structure of the inverter integrated device of the present invention applicable to DC charging piles and AC charging piles in electric vehicles;

[0034] Figure 4 This is an energy flow diagram of an embodiment of the present invention in conventional fast charging mode;

[0035] Figure 5 This is an energy flow diagram of an embodiment of the present invention under low-temperature charging mode;

[0036] Figure 6 This is a schematic diagram of the current waveform of the present invention in low-temperature charging mode;

[0037] Figure 7 This is a flowchart illustrating the method for calculating the pulse amplitude and frequency of the high-frequency pulse current in this invention.

[0038] The components in the diagram are labeled as follows:

[0039] 1. Charging pile; 2. DC charging interface; 3. Electric vehicle; 4. Inverter group; 5. Control unit; 6. Detection unit; 7. On-board charger; 8. AC charging interface; 9. Lithium battery pack; 10. Inverter integrated device; 11. Mode switching switch; 12. Motor stator winding; 13. Complementary switching transistors (Q1, Q2, Q3, Q4, Q5, Q6). Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 and Figure 3 As shown, an inverter integrated device 10 includes a DC charging interface 2 connected to a DC charging pile and a lithium battery pack 9 mounted on an electric vehicle 3. The positive terminal of the DC charging interface 2 is connected to the positive terminal of the lithium battery pack 9 via a mode switching switch S1, and the negative terminal of the lithium battery pack 9 is connected to the negative terminal of the DC charging interface 2. Three sets of inverter groups 4 are connected in parallel on the lithium battery pack 9. Each set of inverter groups 4 includes two complementary switching transistors connected in series. Specifically, in this embodiment, complementary switching transistors Q1 and Q4 form one group, complementary switching transistors Q2 and Q5 form one group, and complementary switching transistors Q3 and Q4 form another group. The complementary switching transistors Q6 form a group. The positive terminal of the DC charging interface 2 is connected to the motor stator winding M. Each phase of the motor stator winding M is connected to the midpoint of an inverter group 4. Specifically, phase A is connected to the midpoint of complementary switching transistors Q1 and Q4, phase B is connected to the midpoint of complementary switching transistors Q2 and Q5, and phase C is connected to the midpoint of complementary switching transistors Q3 and Q6. The mode switching switch S1, the complementary switching transistors, and the DC charging pile are all connected to the control unit 5. The control unit 5 is connected to the detection unit 6, which is connected to the lithium battery pack 9 and the motor stator winding M.

[0042] In this embodiment, when the electric vehicle 3 is ready to charge, the detection unit 6 detects the real-time temperature of the lithium battery pack 9 and transmits it to the control unit 5. The control unit 5 compares the real-time battery temperature with a preset temperature threshold. If the real-time battery temperature is higher than the preset temperature threshold, it enters the normal fast charging mode. The control unit 5 communicates with the DC charging pile via the CAN low-voltage bus, causing the DC charging pile to switch to normal fast charging mode. Figure 4 As shown, the control mode switching switch S1 of the control unit 5 is closed, and the complementary switching transistors in the three sets of inverter groups 4 are turned off.

[0043] If the battery's real-time temperature is lower than the preset temperature threshold, it enters a low-temperature charging mode. Control unit 5 communicates with the DC charging pile via low-voltage CAN bus, switching the DC charging pile to constant-voltage mode. Figure 5As shown, the control mode switching switch S1 is turned off, and the complementary switching transistors in the three sets of inverter groups 4 are turned on and off to generate a high-frequency pulse current to heat and charge the lithium battery pack 9 until the lithium battery pack 9 is heated to the preset temperature threshold and enters the normal fast charging mode.

[0044] like Figure 2 As shown, in another embodiment, the DC charging interface 2 is connected to an on-board charger 7, the on-board charger 7 is connected to the control unit 5, the on-board charger 7 is connected to an AC charging interface 8, and the AC charging interface 8 is connected to an AC charging pile.

[0045] In addition, such as Figure 3 As shown, an embodiment is also provided, which includes a charging pile 1. The charging pile 1 can be an AC charging pile or a DC charging pile. When it is an AC charging pile, it is connected to it through an AC charging interface 8. When it is a DC charging pile, it is connected to it through a DC charging interface 2.

[0046] In this embodiment, when the electric vehicle 3 is ready to charge, the detection unit 6 detects the real-time temperature of the lithium battery pack 9 and transmits it to the control unit 5. The control unit compares the real-time battery temperature with the preset temperature threshold. If the real-time battery temperature is higher than the preset temperature threshold, it enters the normal fast charging mode. The control unit 5 controls the on-board charger 7 to be in constant voltage charging mode, the mode switching switch S1 is closed, and the complementary switching tubes in the three sets of inverter groups 4 are turned off.

[0047] If the real-time battery temperature is lower than the preset temperature threshold, it enters the low-temperature charging mode. The control unit 5 controls the on-board charger 7 to be in constant voltage charging mode and controls the mode switching switch S1 to be open. At the same time, it controls the switching of the complementary switching transistors in the three sets of inverter groups 4 to generate high-frequency pulse current to heat and charge the lithium battery pack 9 until the lithium battery pack 9 is heated to the preset temperature threshold and enters the normal fast charging mode.

[0048] In the above embodiments, when entering the low-temperature charging mode, such as Figure 5 As shown, when the control mode switching switch S1 of the control unit 5 is open, the complementary switches Q1, Q2, and Q3 are open, and the complementary switches Q4, Q5, and Q6 are closed. Current flows from the positive terminal of the DC charging interface 2 through the motor stator winding M and the complementary switches Q1, Q2, and Q3, returning to the negative terminal of the DC charging interface 2. At this time, the inductor current value of the motor stator winding M gradually increases; this state is the inductor energy storage state. The detection unit 6 continuously detects the inductor current value of the motor stator winding M and transmits it to the control unit 5. When the inductor current value of the motor stator winding M rises to the upper limit of the amplitude parameter I... LHWhen the control unit 5 controls complementary switches Q1, Q2, and Q3 to close, and complementary switches Q4, Q5, and Q6 to open, the inductor current of the motor stator winding M gradually decreases. This state is the inductor energy release state. When the inductor current of the motor stator winding M decreases to the lower limit of the amplitude parameter I... LL At this time, control unit 5 switches to inductive energy storage state, and this switching is repeated to generate energy such as... Figure 6 The high-frequency pulsed current shown simultaneously heats and charges the lithium battery pack 9.

[0049] Among them, the pulse amplitude and frequency of the high-frequency pulse current are determined by the upper limit I of the amplitude parameter of the inductance current value of the motor stator winding M. LH and amplitude parameter lower limit I LL Control, such as Figure 6 The figure shows a schematic diagram of the current waveform in low-temperature charging mode.

[0050] like Figure 7 As shown, the calculation method for the pulse amplitude and frequency of high-frequency pulse current includes the following steps:

[0051] A) Input pulse current amplitude boundary I under different temperatures, different SOCs, and different SOHs set and frequency f set A table of lithium plating boundary and high-frequency pulse temperature rise characteristics was obtained;

[0052] B) Obtain the upper limit I of the amplitude parameter for the inductance current value of the motor stator winding M. LH Real-time battery temperature, SOC, and SOH;

[0053] C) Set the upper limit of the amplitude parameter I LH The battery's real-time temperature, SOC, and SOH are input into the lithium plating boundary table and the high-frequency pulse temperature rise characteristic table to obtain the lithium plating boundary and the corresponding frequency boundary f in the high-frequency pulse temperature rise characteristic table. LH ;

[0054] D) Calculate and obtain the frequency boundary:

[0055]

[0056] In the formula, R is the total circuit impedance, L is the inductance of the motor stator winding M, and U is the voltage of the lithium battery pack 9.

[0057] E) If If X is the precision coefficient, proceed to step F); otherwise, proceed to step H.

[0058] F) Locate the corresponding f(I) in the table of lithium plating boundary and high-frequency pulse temperature rise characteristics. LH ,I LL Amplitude boundary I set, let I LH =I set f LH =f(I LH ,I LL It enters low-temperature charging mode;

[0059] G) The detection unit continuously monitors the real-time temperature of the lithium battery pack 9. When the temperature rise ΔT is less than t, it continues to maintain the low-temperature charging mode. Whenever the temperature rise ΔT reaches t, it returns to step B) until the real-time battery temperature is greater than or equal to the temperature threshold Y, and then enters the normal fast charging mode.

[0060] H) Locate the corresponding f(I) in the table of lithium plating boundary and high-frequency pulse temperature rise characteristics. LH ,I LL Amplitude boundary I set , let I LH =(I set +I LH ) / 2, return to step C).

[0061] This invention relates to an inverter integrated device and its control method. The low-temperature fast charging method employed is high-frequency pulse charging. Under high-frequency pulses, the battery's internal resistance is low, resulting in a small polarization voltage. This allows for charging with a larger current while avoiding lithium plating, shortening the overall charging time in low-temperature environments. Furthermore, the heating method is internal preheating, utilizing the internal impedance of the lithium battery pack 9 to generate heat. Compared to external heating methods, this improves thermoelectric conversion efficiency and temperature rise rate, enabling the lithium battery pack to generate a faster temperature rise while charging. Additionally, the charging method can be switched promptly based on the temperature of the lithium battery pack 9, achieving ultra-fast charging without compromising battery life. The magnitude and frequency of the high-frequency DC pulse current can be adjusted in real-time according to battery temperature and state of charge, saving low-temperature charging time and reducing the risk of lithium plating degradation during low-temperature charging of the lithium battery pack 9. Finally, it utilizes existing hardware structures, requiring no additional hardware, resulting in low cost and ease of implementation. It is also applicable to various charging piles, including AC charging piles, 400V DC charging piles, and 800V DC charging piles.

Claims

1. An inverter integrated device, comprising a DC charging interface (2) connected to a DC charging pile and a lithium battery pack (9) mounted on an electric vehicle (3), characterized in that: The positive terminal of the DC charging interface (2) is connected to the positive terminal of the lithium battery pack (9) via a mode switching switch (S1), and the negative terminal of the lithium battery pack (9) is connected to the negative terminal of the DC charging interface (2). Three inverter groups (4) are connected in parallel on the lithium battery pack (9). Each inverter group (4) includes two complementary switching transistors connected in series. The positive terminal of the DC charging interface (2) is connected to a motor stator winding (M). Each phase of the motor stator winding (M) is connected to the midpoint of one inverter group (4). The mode switching switch (S1), the complementary switching transistors, and the DC charging pile are all connected to a control unit (5). The control unit (5) is connected to a detection unit (6), which is connected to the lithium battery pack (9) and the motor stator winding (M). The control unit (5) compares the real-time battery temperature with the preset temperature threshold. If the real-time battery temperature is higher than the preset temperature threshold, it enters the normal fast charging mode. The control unit (5) communicates with the DC charging pile through the CAN low-voltage bus to switch the DC charging pile to the normal fast charging state. If the real-time battery temperature is lower than the preset temperature threshold, it enters the low-temperature charging mode. The control unit (5) interacts with the DC charging pile through the CAN low-voltage communication to switch the DC charging pile to the constant voltage mode and controls the mode switching switch (S1) to open. At the same time, it controls the switching of the complementary switching tubes in the three sets of inverter groups (4) to generate a high-frequency pulse current to heat and charge the lithium battery pack (9) until the lithium battery pack (9) is heated to the preset temperature threshold and enters the normal fast charging mode.

2. The inverter integrated device as described in claim 1, characterized in that: The DC charging interface (2) is connected to the on-board charger (7), the on-board charger (7) is connected to the control unit (5), the on-board charger (7) is connected to the AC charging interface (8), and the AC charging interface (8) is connected to the AC charging pile.

3. A method for controlling the use of the inverter integrated device as described in claim 1, characterized in that: When the electric vehicle (3) is ready to charge, the detection unit (6) detects the real-time temperature of the lithium battery pack (9) and transmits it to the control unit (5). The control unit (5) compares the real-time temperature of the battery with the preset temperature threshold. If the real-time temperature of the battery is higher than the preset temperature threshold, it enters the normal fast charging mode. The control unit (5) communicates with the DC charging pile through the CAN low-voltage bus to switch the DC charging pile to the normal fast charging state. The control unit (5) controls the mode switching switch (S1) to close and turns off the complementary switching tubes in the three sets of inverter groups (4). If the real-time temperature of the battery is lower than the preset temperature threshold, it enters the low-temperature charging mode. The control unit (5) interacts with the DC charging pile through the CAN bus low-voltage communication, so that the DC charging pile switches to constant voltage mode and controls the mode switching switch (S1) to open. At the same time, it controls the switching of the complementary switching tubes in the three sets of inverter groups (4) to generate high-frequency pulse current to heat and charge the lithium battery pack (9) until the lithium battery pack (9) is heated to the preset temperature threshold and enters the normal fast charging mode.

4. The method for controlling the use of the inverter integrated device as described in claim 3, characterized in that: The DC charging interface (2) is connected to the on-board charger (7), the on-board charger (7) is connected to the control unit (5), the on-board charger (7) is connected to the AC charging interface (8), the AC charging interface (8) is connected to the AC charging pile, when the electric vehicle (3) is ready to charge, the detection unit (6) detects the real-time battery temperature of the lithium battery pack (9) and transmits it to the control unit (5), the control unit compares the real-time battery temperature with the preset temperature threshold, if the real-time battery temperature is higher than the preset temperature threshold, it enters the normal fast charging mode, the control unit (5) controls the on-board charger (7) to be in constant voltage charging mode, the mode switching switch (S1) is closed, and the complementary switching tubes in the three sets of inverter groups (4) are turned off; If the real-time temperature of the battery is lower than the preset temperature threshold, it enters the low-temperature charging mode. The control unit (5) controls the on-board charger (7) to be in constant voltage charging mode and controls the mode switching switch (S1) to be disconnected. At the same time, it controls the switching of the complementary switching tubes in the three inverter groups (4) to generate high-frequency pulse current to heat and charge the lithium battery pack (9) until the lithium battery pack (9) is heated to the preset temperature threshold and enters the normal fast charging mode.

5. The method for controlling the use of the inverter integrated device as described in claim 3 or 4, characterized in that: When entering the low-temperature charging mode, the control unit (5) controls the mode switching switch (S1) to open, the complementary switch tube connected to the positive terminal of the DC charging interface (2) in the inverter group (4) is disconnected, and the complementary switch tube connected to the negative terminal of the DC charging interface (2) is closed. The current flows from the positive terminal of the DC charging interface (2) through the motor stator winding (M) and the complementary switch tube connected to the negative terminal of the DC charging interface (2), and returns to the negative terminal of the DC charging interface (2). At this time, the inductor current value of the motor stator winding (M) gradually increases. This state is the inductor energy storage state. The detection unit (6) continuously detects the inductor current value of the motor stator winding (M) and transmits it to the control unit (5). When the inductor current value of the motor stator winding (M) rises to the upper limit of the amplitude parameter, I LH When the control unit (5) controls the complementary switch connected to the positive terminal of the DC charging interface (2) in the inverter group (4) to close, and the complementary switch connected to the negative terminal of the DC charging interface (2) to open, at this time the inductor current value of the motor stator winding (M) gradually decreases. This state is the inductor energy release state. When the inductor current value of the motor stator winding (M) decreases to the lower limit of the amplitude parameter... I LL When the control unit (5) switches to inductive energy storage mode, it repeatedly switches to generate high-frequency pulse current to heat and charge the lithium battery pack (9).

6. The method for controlling the use of the inverter integrated device as described in claim 5, characterized in that: The pulse amplitude and frequency of the high-frequency pulse current are determined by the upper limit of the amplitude parameter of the inductance current value of the motor stator winding (M). I LH and amplitude parameter lower limit I LL control.

7. The method for controlling the use of the inverter integrated device as described in claim 6, characterized in that: The calculation method for the pulse amplitude and frequency of high-frequency pulse current includes the following steps: A) Input pulse current amplitude boundaries under different temperatures, different SOCs, and different SOHs I set and frequency f set A table of lithium plating boundary and high-frequency pulse temperature rise characteristics was obtained; B) Obtain the upper limit of the amplitude parameter of the inductance current value of the motor stator winding (M). I LH Real-time battery temperature, SOC, and SOH; C) Set the upper limit of the amplitude parameter I LH The battery's real-time temperature, SOC, and SOH are input into the lithium plating boundary table and the high-frequency pulse temperature rise characteristic table to obtain the lithium plating boundary and the corresponding frequency boundary in the high-frequency pulse temperature rise characteristic table. f LH ; D) Calculate and obtain the frequency boundary: In the formula, L is the total impedance of the circuit, L is the inductance of the motor stator winding (M), and U is the voltage of the lithium battery pack (9). E) If If X is the precision coefficient, proceed to step F; otherwise, proceed to step H. F) Locate the corresponding lithium plating boundary and high-frequency pulse temperature rise characteristics in the table. amplitude boundary I set ,make I LH = I set , f LH = Enter low-temperature charging mode; G) The detection unit continuously detects the real-time temperature of the lithium battery pack (9). When the temperature rise ΔT is less than t, it continues to maintain the low-temperature charging mode. Whenever the temperature rise ΔT reaches t, it returns to step B) until the real-time battery temperature is greater than or equal to the temperature threshold Y, and then enters the normal fast charging mode. H) Locate the corresponding lithium plating boundary and high-frequency pulse temperature rise characteristics in the table. amplitude boundary I set ,make (Return to step C).

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