Vehicle battery self-heating system and method

Abstract

The application relates to the field of vehicle batteries, and discloses a vehicle battery self-heating system and method.The system comprises a vehicle battery, a first switch device group, a second switch device group, a controller, a motor, a resonant capacitor and a switch, the first switch device group comprises first and second power switches, the first source-drain electrode of the first power switch is connected to the first end of the battery, the second source-drain electrode is connected to the third source-drain electrode of the second power switch, the fourth source-drain electrode of the second power switch is connected to the second end of the battery, and the second switch device group comprises third and fourth power switches; the fifth source-drain electrode of the third power switch is connected to the first end, the sixth source-drain electrode is connected to the seventh source-drain electrode of the fourth power switch, and the eighth source-drain electrode of the fourth power switch is connected to the second end; the gate of each power switch is connected to the controller, and the first side and the second side of the motor are connected to the first and second switch device groups respectively.Compared with the related art, the application has the advantages of high battery self-heating efficiency and low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle battery, in particular to a vehicle battery self-heating system and method. BACKGROUND

[0002] Lithium ion battery is an important part of electric vehicles, but the performance of lithium ion battery is easily affected by temperature, especially in low temperature environment, the performance of lithium ion battery will be significantly degraded. In order to solve the problem of performance degradation of lithium ion battery in low temperature environment, a lithium battery heating system is configured on the electric vehicle.

[0003] In related technologies, the lithium battery heating system can be realized by PTC (Positive Temperature Coefficient, positive temperature coefficient) thermistor heating or heat pump heating, so as to improve the environmental temperature of lithium ion battery working. For the thermistor heating mode, it has the problem of low heating efficiency, and the lithium ion battery is used to supply power for the thermistor, which consumes a large amount of lithium ion battery power, seriously affecting the endurance of electric vehicles; for the heat pump heating mode, it has the problems of complex structure and high implementation cost, and the heating efficiency is low in low temperature environment. SUMMARY

[0004] Therefore, the present application can provide a vehicle battery self-heating system and method to solve the problem of low heating efficiency in related technologies.

[0005] In a first aspect, the present application provides a vehicle battery self-heating system, which comprises:

[0006] The vehicle battery has a first end and a second end;

[0007] The first switch device group comprises a first power switch and a second power switch; the first source-drain electrode of the first power switch is connected to the first end, the second source-drain electrode of the first power switch is connected to the third source-drain electrode of the second power switch, and the fourth source-drain electrode of the second power switch is connected to the second end;

[0008] The second switch device group comprises a third power switch and a fourth power switch; the fifth source-drain electrode of the third power switch is connected to the first end, the sixth source-drain electrode of the third power switch is connected to the seventh source-drain electrode of the fourth power switch, and the eighth source-drain electrode of the fourth power switch is connected to the second end;

[0009] The controller is connected to the first gate electrode of the first power switch, the second gate electrode of the second power switch, the third gate electrode of the third power switch and the fourth gate electrode of the fourth power switch, respectively;

[0010] The motor has a first side and a second side; the second source drain and the third source drain are respectively used to connect to the first side, and the sixth source drain and the seventh source drain are respectively used to connect to the second side;

[0011] The resonant capacitor has a third terminal and a fourth terminal; the third terminal is connected to the second side of the motor, and the sixth and seventh source drains are connected to the fourth terminal respectively.

[0012] Switch; the switch is connected in parallel with the resonant capacitor.

[0013] In the vehicle battery self-heating system of this invention, the motor is equivalent to an inductor. A first set of switching devices is disposed between one end of the inductor and the vehicle battery, and a second set of switching devices is disposed between the other end of the inductor and the vehicle battery. A controller controls the on / off state of the first and second power switches in the first set of switching devices, as well as the third and fourth power switches in the second set of switching devices. This generates battery discharge and charging currents between the vehicle battery and the inductor. Heat is generated as the current flows through the internal resistance of the vehicle battery, thus achieving battery self-heating. This invention utilizes an LC oscillation circuit scheme formed by connecting a resonant capacitor in series with the equivalent inductance of the motor. This scheme can generate a larger heating current through the LC oscillation circuit, resulting in lower heating loss and higher heating efficiency. This invention can employ different battery heating modes and thus different heating currents by controlling the switches to be in a closed or open state. This method not only helps to regulate the battery self-heating current but also helps to ensure battery safety. Compared to thermistor heating, this invention eliminates the need for a separate thermistor, instead heating the battery itself through heat release from its internal resistance. This results in higher energy conversion and heating efficiency. Compared to heat pump heating, the self-heating solution provided by this invention significantly reduces the impact of low-temperature environments on the battery heating process, enabling high-power heating even in low-temperature conditions. Furthermore, the overall structure is more streamlined, leading to lower implementation costs. Therefore, this invention offers advantages such as high battery self-heating efficiency, high energy utilization, and low cost.

[0014] In one optional embodiment, the motor is a three-phase four-wire motor, the first side includes phase A, phase B and phase C, and the second side is the neutral wire of the three-phase four-wire motor;

[0015] The first power switch includes a first sub-switch, a second sub-switch, and a third sub-switch arranged in parallel; the second power switch includes a fourth sub-switch, a fifth sub-switch, and a sixth sub-switch arranged in parallel.

[0016] Specifically, the second source-drain of the first sub-switch and the third source-drain of the fourth sub-switch are connected to phase A, the second source-drain of the second sub-switch and the third source-drain of the fifth sub-switch are connected to phase B, and the second source-drain of the third sub-switch and the third source-drain of the sixth sub-switch are connected to phase C.

[0017] Based on the above connection method, the present invention enables the use of the three bridge arms of the three-phase four-wire motor after parallel connection, avoiding the problem of torque generation when heating the vehicle battery. The operating condition of the equivalent inductance of the three-phase four-wire motor is more stable, thereby further improving the heating efficiency of the vehicle battery.

[0018] In one alternative implementation, the system further includes:

[0019] The coolant circulation pipeline includes a first pipeline, a second pipeline, and a third pipeline, and the coolant circulation pipeline is filled with circulating coolant; the first pipeline is located next to the motor, the second pipeline is located next to the resonant capacitor, and the third pipeline is located next to the battery.

[0020] The present invention can also recover the heat generated by the motor and resonant capacitor, and transfer the recovered heat to the vehicle battery to further heat the vehicle battery.

[0021] In one alternative implementation, the system further includes:

[0022] The DC bus capacitor is connected to the first and second terminals respectively.

[0023] The present invention can also stabilize the voltage on both sides of the first switching device group and the voltage on both sides of the second switching device group through the DC bus capacitor, thereby ensuring the stability of the operation of the first switching device group and the second switching device group, and thus ensuring the reliability of the vehicle battery self-heating system.

[0024] In a second aspect, the present invention provides a vehicle battery self-heating method, applied to a controller in a vehicle battery self-heating system according to one or more embodiments of the present invention, the method comprising:

[0025] The first switching frequency is determined based on the voltage of the vehicle battery;

[0026] A first control pulse is sent to the first power switch and the fourth power switch at the first switching frequency, and a second control pulse is sent to the second power switch and the third power switch at the first switching frequency.

[0027] The difference between the phase of the first control pulse and the phase of the second control pulse is a first set value.

[0028] Based on the first and second control pulses, this invention controls the on / off states of the first and second power switches in the first switching device group, as well as the third and fourth power switches in the second switching device group. This generates battery discharge and charging currents between the vehicle battery and the inductor. Heat is generated as the current flows through the internal resistance of the vehicle battery, thus achieving battery self-heating. Compared to thermistor heating, this invention eliminates the need for a separate thermistor, instead heating the battery itself through heat release from its internal resistance, resulting in higher energy conversion and heating efficiency. Compared to heat pump heating, this self-heating solution significantly reduces the impact of low temperatures on the battery heating process, enabling high-power heating even in low-temperature environments. Furthermore, the overall structure is more streamlined, and the implementation cost is lower. Therefore, this invention offers advantages such as high battery self-heating efficiency, high energy utilization, and low cost.

[0029] In one optional embodiment, a motor and a resonant capacitor are connected in series between the first switching device group and the second switching device group, and the resonant capacitor is connected in parallel to the switch.

[0030] Before determining the first switching frequency based on the vehicle battery voltage, the process also includes:

[0031] Determine the range of the vehicle battery's state of charge.

[0032] If the state of charge of the vehicle battery is within the first preset range, the control switch is turned off, and a third control pulse is sent to the first power switch and the fourth power switch at the second switching frequency, and a fourth control pulse is sent to the second power switch and the third power switch at the second switching frequency.

[0033] Wherein, the first preset range is greater than the first preset value and less than the second preset value, and the difference between the phase of the third control pulse and the phase of the fourth control pulse is the second set value;

[0034] If the state of charge of the vehicle battery is within the second preset range, the control switch is closed, and the process returns to the step of determining the first switching frequency.

[0035] The second preset range is less than or equal to the first preset value, or greater than or equal to the second preset value.

[0036] This invention can also heat the vehicle battery via inductive heating when the battery's SOC is too high or too low. This method avoids using excessive current to heat the vehicle battery when the SOC is too high or too low, ensuring safety during the heating process while achieving the heating objective. Furthermore, this invention can provide a higher heating current via resonant heating mode when the battery SOC is moderate, enabling rapid heating of the vehicle battery. Therefore, this invention balances both the heating speed and safety of the vehicle battery.

[0037] In one alternative implementation, before determining the range of the vehicle battery's state of charge, the method further includes:

[0038] The battery management system receives self-heating commands and vehicle battery status information sent by the battery management system. The status information includes state of charge, voltage, and battery temperature. The battery management system is used to collect the vehicle battery status information.

[0039] Based on the self-heating command and / or battery temperature, determine whether to perform the step of determining the range of the vehicle battery's state of charge.

[0040] The present invention can also reliably control whether the vehicle's self-heating system activates battery self-heating operation based on self-heating commands and / or battery temperature.

[0041] In one alternative implementation, the second switching frequency is half the resonant frequency of the resonant unit formed by the equivalent inductance of the motor and the resonant capacitance.

[0042] The second switching frequency determined by the present invention in the manner described above can improve the resonance effect of the resonant unit, thereby further improving the self-heating effect of the vehicle battery.

[0043] In one alternative implementation, determining a first switching frequency based on the voltage of the vehicle battery includes:

[0044]

[0045] Where fL represents the first switching frequency, Ubat represents the vehicle battery voltage, L represents the inductance value of the motor's equivalent inductance, and Irms represents the effective value of the self-heating current to be achieved.

[0046] In one optional implementation, the second switching frequency is fLC;

[0047]

[0048] Where L represents the inductance value of the motor's equivalent inductance, and C... res This indicates the capacitance value of the resonant capacitor. Attached Figure Description

[0049] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structural composition of a vehicle battery self-heating system according to an embodiment of the present invention;

[0051] Figure 2 This is a schematic diagram of the structural composition of another vehicle battery self-heating system according to an embodiment of the present invention;

[0052] Figure 3 This is a schematic diagram of the structural composition of another vehicle battery self-heating system according to an embodiment of the present invention;

[0053] Figure 4 This is a schematic flowchart of a vehicle battery self-heating method according to an embodiment of the present invention;

[0054] Figure 5 This is a schematic flowchart of another vehicle battery self-heating method according to an embodiment of the present invention;

[0055] Figure 6 This is a schematic flowchart of another vehicle battery self-heating method according to an embodiment of the present invention;

[0056] Figure 7 The waveforms are the total current waveform IL of the three-phase winding of the motor, the current waveform Ibat flowing through the battery, and the output voltage waveform Vab of the motor in the resonant heating mode according to an embodiment of the present invention.

[0057] Figure 8 The waveform diagrams are of the total current waveform IL of the three-phase winding of the motor, the current waveform Ibat flowing through the battery, and the output voltage waveform Vab of the motor in the inductive heating mode according to an embodiment of the present invention.

[0058] In the picture,

[0059] 100. Vehicle battery;

[0060] 200, First switching device group; 201, First power switch; 202, Second power switch;

[0061] 300. Second switching device group; 301. Third power switch; 302. Fourth power switch;

[0062] 400. Controller;

[0063] 500. Electric motor;

[0064] 600, resonant capacitor;

[0065] 700, switch;

[0066] 801, First pipeline; 802, Second pipeline; 803, Third pipeline;

[0067] 900. DC bus capacitor. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] Lithium-ion batteries, with their advantages of high energy storage, high power density, fast charging capability, low maintenance requirements, and good charge-discharge cycle life, have become an indispensable part of electric vehicles. However, the characteristics of lithium-ion batteries are greatly affected by ambient temperature. The performance of lithium-ion batteries operating in low-temperature environments will significantly degrade. For example, prolonged charging and discharging of lithium-ion batteries at ambient temperatures below 20°C will drastically shorten their lifespan, affecting the power output and range of the electric vehicle. Therefore, some electric vehicles are equipped with lithium battery heating systems, which are generally implemented using thermistor heating or heat pump heating schemes. For thermistor heating, the lithium-ion battery powers the thermistor, and the heat generated by the thermistor heats the lithium-ion battery. The biggest drawback of this method is that only a small portion of the large amount of battery energy consumed in powering the thermistor is converted into heat energy for heating the lithium-ion battery, resulting in low energy conversion efficiency and consequently low heating efficiency. The heat pump heating solution reverses the cooling principle of air conditioning to achieve the heat pump heat release function, thereby heating the lithium-ion battery. However, during implementation, it was found that the heating efficiency of this solution is too low when the outdoor ambient temperature is low. In addition, the solution also has problems such as complex overall structure and high implementation cost.

[0070] like Figure 1 As shown, the vehicle battery self-heating system provided in this embodiment of the invention includes, but is not limited to, a vehicle battery 100, a first switching device group 200, a second switching device group 300, a controller 400, a motor 500, a resonant capacitor 600, and a switch 700.

[0071] The vehicle battery 100 has a first end and a second end. The vehicle battery 100 involved in the embodiments of the present invention may include, but is not limited to, a lithium-ion battery; any vehicle battery 100 whose performance is affected by temperature is within the protection scope of the present invention.

[0072] The vehicle battery 100 serves as the power battery for the electric vehicle, providing power for its operation. The first terminal of the vehicle battery 100 can be a positive terminal, and the second terminal can be a negative terminal.

[0073] The first switching device group 200 includes a first power switch 201 and a second power switch 202; the first source and drain of the first power switch 201 are connected to a first terminal, the second source and drain of the first power switch 201 are connected to the third source and drain of the second power switch 202, and the fourth source and drain of the second power switch 202 are connected to a second terminal.

[0074] It should be understood that the term "source-drain" in this invention refers to either the source or the drain, and for a given power switch, if one source-drain is the source, the other source-drain is the drain. For example, if the first source-drain of the first power switch 201 is the source, then the second source-drain of the first power switch 201 is the drain; or, if the first source-drain of the first power switch 201 is the drain, then the second source-drain of the first power switch 201 is the source.

[0075] In this embodiment, the first power switch 201 may include one or more switching devices connected in parallel, and the second power switch 202 may include one or more power switching devices connected in parallel.

[0076] The power switching device involved in this invention may be a MOS transistor (Metal-Oxide-Semiconductor Field-Effect Transistor).

[0077] The second switching device group 300 includes a third power switch 301 and a fourth power switch 302; the fifth source-drain of the third power switch 301 is connected to the first terminal, the sixth source-drain of the third power switch 301 is connected to the seventh source-drain of the fourth power switch 302, and the eighth source-drain of the fourth power switch 302 is connected to the second terminal.

[0078] The third power switch 301 of the present invention may include one or more power switching devices arranged in parallel, and the fourth power switch 302 may include one or more power switching devices arranged in parallel.

[0079] In this embodiment, MOSFET S41 represents the third power switch 301, and MOSFET S42 represents the fourth power switch 302.

[0080] Specifically, in this embodiment of the invention, the first gate of the first power switch 201, the second gate of the second power switch 202, the third gate of the third power switch 301, and the fourth gate of the fourth power switch 302 are respectively connected to the controller 400. In this embodiment, the controller 400 is specifically a motor controller, which has four different pins that are connected to the first gate, the second gate, the third gate, and the fourth gate in a one-to-one correspondence.

[0081] In this embodiment of the invention, the gate of each power switch is connected to the corresponding pin on the controller, and the first side and the second side of the motor 500 are respectively connected to the first switching device group 200 and the second switching device group 300.

[0082] Specifically, the motor 500 has a first side and a second side; the second source drain and the third source drain are respectively used to connect to the first side, and the sixth source drain and the seventh source drain are respectively used to connect to the second side.

[0083] In this embodiment, the first power switch 201, the second power switch 202, the third power switch 301 and the fourth power switch 302 constitute an equivalent H-bridge topology, and the motor 500 is located in the middle of this equivalent H-bridge topology.

[0084] like Figure 1 As shown, capacitor C res This indicates a resonant capacitance of 600.

[0085] The resonant capacitor 600 has a third terminal and a fourth terminal. The third terminal is connected to the second side of the motor 500, and the sixth and seventh source drains are connected to the fourth terminal, respectively.

[0086] An LC oscillation circuit is formed by using the resonant capacitor 600 and the equivalent inductance of the motor 500, thereby generating a large current in the vehicle battery 100, for example... Figure 7 The maximum current flowing through the vehicle battery 100 in the resonant heating mode shown in the figure can reach an amplitude of 200A (Amperes).

[0087] like Figure 1As shown, switch 700 is connected in parallel with resonant capacitor 600. Switch K1 represents switch 700. When the switch is open, the vehicle battery self-heating system in this embodiment can operate in resonant heating mode, using an LC oscillation circuit formed by the resonant capacitor and the equivalent inductance of the motor in series to heat the vehicle battery; when the switch is closed, the vehicle battery self-heating system in this embodiment can operate in inductive heating mode, using the equivalent inductance of the motor to heat the vehicle battery. It can be seen that the present invention can also use different battery heating modes to heat the vehicle battery by controlling the switch to be in a closed or open state, thereby using different heating currents to heat the vehicle battery. This method not only helps to adjust the battery self-heating current but also helps to ensure battery safety.

[0088] Figure 1 The illustrated vehicle battery self-heating system operates as follows: A first control pulse is sent to a first power switch and a fourth power switch at a first switching frequency, and a second control pulse is sent to a second power switch and a third power switch at the same first switching frequency. In this embodiment, the motor 500 is equivalent to an inductor, which acts as an energy storage element. During this process, the vehicle battery 100 is repeatedly and rapidly discharged and charged. The current generated during discharge and charging flows through the internal resistance of the vehicle battery 100, generating heat. This heat is used to heat the battery, thereby achieving the vehicle battery self-heating function. The phase difference between the first control pulse and the second control pulse in this embodiment is a first preset value, such as 180°.

[0089] In this embodiment, the motor in the vehicle battery self-heating system is equivalent to an inductor. A first switching device group is provided between one end of the inductor and the vehicle battery, and a second switching device group is provided between the other end of the inductor and the vehicle battery. The controller controls the on / off state of the first and second power switches in the first switching device group, as well as the third and fourth power switches in the second switching device group. During this process, the vehicle battery is rapidly and repeatedly charged and discharged, forming a battery discharge current and a battery charging current between the vehicle battery and the inductor. The battery discharge current and battery charging current are specifically alternating currents. Heat is generated as the current flows through the internal resistance of the vehicle battery, thereby achieving the purpose of battery self-heating.

[0090] In an optional embodiment of the present invention, a third control pulse is sent to the first power switch and the fourth power switch at a second switching frequency, and a fourth control pulse is sent to the second power switch and the third power switch at the second switching frequency. The resonant capacitor 600, which is equivalent to the inductance of the motor 500, serves as an energy storage element. During this process, the vehicle battery 100 is repeatedly and rapidly discharged and charged. The current generated during discharge and charging flows through the internal resistance of the vehicle battery 100, generating heat, thereby achieving the self-heating function of the vehicle battery. In this embodiment, both the third and fourth control pulses have a second preset duty cycle, such as 50%.

[0091] The embodiment of the present invention uses an LC oscillation circuit scheme formed by connecting a resonant capacitor in series with the equivalent inductance of a motor. This scheme can generate a larger heating current through the LC oscillation circuit, and has the advantages of lower heating loss and higher heating efficiency.

[0092] Compared with related technologies, the embodiments of the present invention add a second switching device group, a second switching device group and a resonant capacitor to the product structure, resulting in a small increase in cost.

[0093] Compared to thermistor heating, this invention eliminates the need for a separate thermistor, instead heating the battery itself through heat release from its internal resistance. This results in higher energy conversion and heating efficiency. Compared to heat pump heating, the self-heating solution provided by this invention significantly reduces the impact of low-temperature environments on the battery heating process, enabling high-power heating even in low-temperature conditions. Furthermore, the overall structure is more streamlined, leading to lower implementation costs. Therefore, this invention offers advantages such as high battery self-heating efficiency, high energy utilization, and low cost.

[0094] In some optional implementations, the motor 500 involved in the embodiments of the present invention is a three-phase four-wire motor, the first side includes phase A, phase B and phase C, and the second side is the neutral wire of the three-phase four-wire motor.

[0095] Among them, the windings corresponding to three-phase four-wire motor A, the windings corresponding to three-phase four-wire motor B, and the windings corresponding to three-phase four-wire motor C are connected in parallel.

[0096] The first power switch 201 includes a first sub-switch, a second sub-switch, and a third sub-switch arranged in parallel, and the second power switch 202 includes a fourth sub-switch, a fifth sub-switch, and a sixth sub-switch arranged in parallel.

[0097] In this embodiment, the second source-drain of the first sub-switch and the third source-drain of the fourth sub-switch are connected to phase A, the second source-drain of the second sub-switch and the third source-drain of the fifth sub-switch are connected to phase B, and the second source-drain of the third sub-switch and the third source-drain of the sixth sub-switch are connected to phase C. Based on the above connection method, this embodiment of the invention enables the parallel connection of the three bridge arms (the winding corresponding to A, the winding corresponding to B of the three-phase four-wire motor, and the winding corresponding to C of the three-phase four-wire motor) for use, avoiding the torque problem generated when heating the vehicle battery. The operating condition of the equivalent inductance of the three-phase four-wire motor is more stable and balanced, and the specific value of the equivalent inductance hardly changes, thereby further improving the heating efficiency of the vehicle battery.

[0098] In this embodiment, the first sub-switch, second sub-switch, third sub-switch, fourth sub-switch, fifth sub-switch, and sixth sub-switch are all power switching devices, each consisting of a MOSFET. Figures 1 to 3 As shown, MOSFET S11 represents the first sub-switch, MOSFET S21 represents the second sub-switch, MOSFET S31 represents the third sub-switch, MOSFET S12 represents the fourth sub-switch, MOSFET S22 represents the fifth sub-switch, and MOSFET S32 represents the sixth sub-switch.

[0099] In this embodiment, the motor controller has eight different pins that are connected one-to-one with the first gate of the first sub-switch, the first gate of the second sub-switch, the first gate of the third sub-switch, the second gate of the fourth sub-switch, the second gate of the fifth sub-switch, the second gate of the sixth sub-switch, the third gate of the third power switch 301, and the fourth gate of the fourth power switch 302. For the resonant capacitor 600, the neutral line of the three-phase four-wire motor is connected in series with the resonant capacitor 600, and the resonant capacitor 600 is connected in parallel through the switch 700.

[0100] Therefore, this embodiment provides a power battery self-heating system based on a three-phase four-wire motor by using the equivalent inductance of the three-phase four-wire motor as an energy storage element.

[0101] Based on the above connection method, the present invention enables the use of three bridge arms connected in parallel, avoiding the problem of torque generation when heating the vehicle battery, and making the operating condition of the equivalent inductance of the three-phase four-wire motor more stable, thereby further improving the heating efficiency of the vehicle battery.

[0102] like Figure 2 As shown, in some alternative embodiments, the vehicle battery self-heating system also includes a coolant circulation line.

[0103] In this embodiment, the coolant circulation pipeline is the coolant circulation pipeline of an electric vehicle. A water pump is installed on the coolant circulation pipeline, which can be used to drive the coolant to circulate in the pipeline. The coolant can be water. In this embodiment, the coolant circulation pipeline is used to realize the heat recovery function.

[0104] The coolant circulation pipeline includes a first pipeline 801, a second pipeline 802 and a third pipeline 803, and the coolant circulation pipeline is filled with circulating coolant; the first pipeline 801 is located next to the motor 500, the second pipeline 802 is located next to the resonant capacitor 600 and the third pipeline 803 is located next to the battery.

[0105] The resonant capacitor 600 is equipped with a capacitor water-cooling plate, and the second pipe 802 is in close contact with the capacitor water-cooling plate. During the operation of the resonant capacitor 600, the heat generated is transferred through the capacitor water-cooling plate to the coolant in the second pipe 802. The circulating coolant can transfer the heat to the battery. Similarly, since a first pipe 801 is provided next to the motor 500 in this embodiment, during the operation of the motor 500, the coolant in the first pipe 801 transfers the heat generated by the motor 500 to the battery.

[0106] Based on the aforementioned coolant circulation pipeline, by transferring the heat generated by the motor and resonant capacitor to the vehicle battery, the present invention can also recover the heat generated by the motor and resonant capacitor, and transfer the recovered heat to the vehicle battery, thereby further heating the vehicle battery.

[0107] like Figure 3 As shown, in some optional embodiments, the vehicle battery self-heating system further includes a DC bus capacitor 900. Specifically, the two ends of the DC bus capacitor 900 are connected to a first end and a second end, respectively.

[0108] Combination Figure 3 As shown, capacitor C bus This indicates a DC bus capacitance of 900.

[0109] The present invention can also stabilize the voltage on both sides of the first switching device group and the voltage on both sides of the second switching device group through the DC bus capacitor, thereby ensuring the stability of the operation of the first switching device group and the second switching device group, and thus ensuring the reliability of the vehicle battery self-heating system.

[0110] According to embodiments of the present invention, a method for self-heating a vehicle battery is provided. Although the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown here. The specific structure of the vehicle battery self-heating system suitable for implementing the vehicle battery self-heating method according to the embodiments of the present invention has been described in detail in this specification and will not be repeated here.

[0111] This embodiment provides a vehicle battery self-heating method, which can be used in the controller of the aforementioned vehicle battery self-heating system. Figure 4This is a flowchart of a vehicle battery self-heating method according to an embodiment of the present invention, such as... Figure 4 As shown, the process includes the following steps:

[0112] Step S110: Determine the first switching frequency based on the voltage of the vehicle battery.

[0113] Step S120: A first control pulse is sent to the first power switch and the fourth power switch according to the first switching frequency, and a second control pulse is sent to the second power switch and the third power switch according to the first switching frequency; wherein, the difference between the phase of the first control pulse and the phase of the second control pulse is a first set value. In this embodiment, both the first control pulse and the second control pulse are pulses with a first preset duty cycle, such as 50%.

[0114] In one or more embodiments of the present invention, the first set value is 180° (degrees), which means that the phase difference between the first control pulse sent to the first power switch and the fourth power switch and the second control pulse sent to the second power switch and the third power switch is 180°.

[0115] Based on the first and second control pulses, embodiments of the present invention control the on / off states of the first and second power switches in the first switching device group, and the third and fourth power switches in the second switching device group. This generates battery discharge and charging currents between the vehicle battery and the inductor. Heat is generated as the current flows through the internal resistance of the vehicle battery, thus achieving battery self-heating. Compared to thermistor heating, this invention eliminates the need for a separate thermistor, instead heating the battery itself through heat release from its internal resistance, resulting in higher energy conversion and heating efficiency. Compared to heat pump heating, the self-heating solution provided by this invention significantly reduces the impact of low-temperature environments on the battery heating process, enabling high-power heating even in low-temperature conditions. Furthermore, the overall structure is more streamlined, and the implementation cost is lower. Therefore, this invention offers advantages such as high battery self-heating efficiency, high energy utilization, and low cost.

[0116] This embodiment provides a vehicle battery self-heating method, which can be used in the controller of the aforementioned vehicle battery self-heating system. In this embodiment, a motor and a resonant capacitor are connected in series between the first switching device group and the second switching device group, and the resonant capacitor is connected in parallel to the switch. The motor in this embodiment can be a three-phase four-wire motor, so this embodiment can provide a power battery self-heating method based on a three-phase four-wire motor. Figure 5 This is a flowchart of a vehicle battery self-heating method according to an embodiment of the present invention, such as... Figure 5 As shown, the process includes the following steps:

[0117] Step S101: Determine the range of the state of charge of the vehicle battery.

[0118] Among them, the state of charge of the vehicle battery is referred to as the vehicle battery SOC (State of Charge).

[0119] This embodiment assumes that the inductance of the equivalent inductance after the three-phase windings of the three-phase four-wire motor are connected in parallel is L, and the vehicle battery voltage is Ubat.

[0120] Step S102: Determine whether the state of charge of the vehicle battery is within a first preset range; wherein, the first preset range is greater than a first preset value and less than a second preset value, and the difference between the phase of the third control pulse and the phase of the fourth control pulse is a second preset value.

[0121] The first preset value is represented as SOC_a, and the second preset value is represented as SOC_b. The specific values ​​can be set according to the actual situation of the vehicle battery.

[0122] Step S103: If the state of charge of the vehicle battery is within the first preset range, the control switch is turned off.

[0123] If the battery SOC_a ≤ SOC ≤ SOC_b, then the control switch is turned off. In this embodiment, after the control switch is turned off, the vehicle battery self-heating method of this embodiment operates in resonant heating mode, including the following step S104.

[0124] In this embodiment, after the control switch is turned off, the vehicle battery self-heating method of the present invention operates in the resonant heating mode, i.e., the following step S104.

[0125] Combination Figures 1 to 3 As shown, after switch K1 is opened, the equivalent inductance and resonant capacitance C of the three-phase windings of the three-phase four-wire motor connected in parallel are... res An LC resonant network is constructed to serve as the load for an equivalent H-bridge, which can then enter the resonant heating mode.

[0126] The first power switch 201, the second power switch 202, the third power switch 301 and the fourth power switch 302 shown in the figure constitute an equivalent H-bridge.

[0127] Step S104 involves sending a third control pulse to the first and fourth power switches at a second switching frequency, and sending a fourth control pulse to the second and third power switches at the same second switching frequency. In this embodiment, both the third and fourth control pulses have a second preset duty cycle, such as 50%. In one or more embodiments of the present invention, the second preset value is 180°, indicating that the third control pulse sent to the first and fourth power switches and the fourth control pulse sent to the second and third power switches are 180° out of phase.

[0128] In this embodiment, it is assumed that the second switching frequency is fLC.

[0129] In some alternative implementations, the second switching frequency in this embodiment is half the resonant frequency of the resonant unit formed by the equivalent inductance of the motor and the resonant capacitance.

[0130] The second switching frequency is Where L represents the inductance value of the motor's equivalent inductance, and C... res This indicates the capacitance value of the resonant capacitor.

[0131] Where fLC represents the inductance L of the equivalent inductance of the motor windings and the capacitance C of the resonant capacitor. res The resonant frequency of the resonant unit formed after series connection is half of the fLC frequency, which can be determined by calculation or offline calibration; specifically,

[0132] This embodiment ignores wire resistance and loss, and ignores DC bus capacitance C. bus Due to the filtering effect, under ideal conditions, the total current of the motor winding in the resonant heating mode in this embodiment is iL(t).

[0133]

[0134] Where ω represents the resonant frequency of the resonant unit, and t represents time.

[0135] The second switching frequency determined by the present invention in the above manner can improve the resonance effect of the resonant unit, thereby further improving the self-heating effect of the vehicle battery.

[0136] Combining the above methods, the self-heating current can reach the expected maximum effective value Ih of the self-heating current. max This method can use a large heating current to self-heat the vehicle battery, and is suitable for rapid heating of the battery when the battery SOC is moderate.

[0137] Additionally, if the maximum effective value of the self-heating current Ih to be achieved is known during the design phase... maxThen the capacitance value of the resonant capacitor in the circuit can be calculated.

[0138] like Figure 7 As shown, the figure illustrates the waveforms of the total three-phase winding current IL, the battery current Ibat, and the motor output voltage Vab in resonant heating mode. In the figure, the horizontal axis represents time (t), in seconds (s), and the vertical axis includes IL, Ibat, and Vab. As shown, the motor output voltage waveform Vab in this embodiment represents the output voltage waveforms of the parallel bridge arms S11, S21, S31, S12, S22, S32, and S41 & S42. Figure 7 As can be seen from this, when operating in this resonant heating mode, the present invention can self-heat the vehicle battery with a large self-heating current.

[0139] Step S105: If the state of charge of the vehicle battery is within the second preset range, the control switch is closed, and the process returns to the step of determining the first switching frequency; wherein, the second preset range is less than or equal to the first preset value, or greater than or equal to the second preset value.

[0140] The first preset value is represented as SOC_a, and the second preset value is represented as SOC_b. The specific values ​​can be set according to the actual situation of the vehicle battery.

[0141] If the battery SOC ≤ SOC_a or the battery SOC ≥ SOC_b, the control switch is closed. In this embodiment, after the control switch is closed, the vehicle battery self-heating method of this embodiment operates in inductive heating mode, including the following steps S110 and S120.

[0142] Step S110: Determine the first switching frequency based on the voltage of the vehicle battery.

[0143] In this embodiment of the invention, fL represents the first switching frequency, which is specifically determined by the voltage of the vehicle battery, the inductance value of the equivalent inductance of the motor, and the effective value of the self-heating current to be achieved.

[0144]

[0145] Where Ubat represents the vehicle battery voltage, L represents the inductance value of the motor's equivalent inductance, and Irms represents the effective value of the self-heating current to be achieved.

[0146] Combination Figures 1 to 3 As shown, after switch K1 is closed, only the three-phase windings of the three-phase four-wire motor serve as the load of the equivalent H-bridge. Unlike the resonant heating mode, this embodiment can then enter the inductive heating mode.

[0147] The first power switch 201, the second power switch 202, the third power switch 301 and the fourth power switch 302 shown in the figure constitute an equivalent H-bridge.

[0148] Step S120: A first control pulse is sent to the first power switch and the fourth power switch according to the first switching frequency, and a second control pulse is sent to the second power switch and the third power switch according to the first switching frequency; wherein, the difference between the phase of the first control pulse and the phase of the second control pulse is a first set value. In this embodiment, both the first control pulse and the second control pulse are pulses with a first preset duty cycle, such as 50%.

[0149] In one or more embodiments of the present invention, the first set value is 180°, which means that the phase difference between the first control pulse sent to the first power switch and the fourth power switch and the second control pulse sent to the second power switch and the third power switch is 180°.

[0150] This embodiment ignores wire resistance and loss, and ignores DC bus capacitance C. bus Due to the filtering effect, under ideal conditions, the total current of the motor winding in the inductive heating mode in this embodiment is iLL(t).

[0151]

[0152] Where t0 represents the start time of the current cycle, and fL represents the first switching frequency.

[0153] In inductive heating mode, the equivalent inductance is represented as the resonant inductance LL, and the current amplitude on the resonant inductance in this embodiment is represented as ILL.

[0154]

[0155] Where L represents the inductance of the resonant inductor LL, and Irms represents the effective value of the self-heating current.

[0156] When the battery SOC is too high or too low, it is not advisable to use a large current for AC self-heating of the battery. As can be seen from the above formula, in this embodiment, the effective value of the self-heating current Irms can be adjusted by adjusting fL, and the effective value of the self-heating current can be reduced by increasing the switching frequency, so as to ensure the safety of the vehicle battery self-heating.

[0157] Furthermore, if the effective value of the self-heating current Irms required in inductive heating mode is known during the design phase, the switching frequency can be calculated. The effective value of the self-heating current, Irms, can be determined based on the battery's SOC through offline calibration, ensuring that the vehicle battery is not overcharged or over-discharged.

[0158] likeFigure 8 As shown, the figure illustrates the waveforms of the total three-phase winding current IL, the battery current Ibat, and the motor output voltage Vab in inductive heating mode. In the figure, the horizontal axis represents time (t), in seconds (s), and the vertical axis includes IL, Ibat, and Vab. As shown, the motor output voltage waveform Vab in this embodiment represents the output voltage waveforms of the parallel bridge arms S11, S21, S31, S12, S22, S32, and S41 & S42. Figure 8 As can be seen from the diagram, when operating in inductive heating mode, this invention can obtain a suitable or even a small battery self-heating current by adjusting the switching frequency.

[0159] Regardless of whether resonant heating mode or inductive heating mode is used, the vehicle battery self-heating method provided by this invention further includes the following steps: monitoring the real-time temperature of the vehicle battery; if the real-time temperature of the vehicle battery reaches the expected temperature Tc, then stopping self-heating; and / or, receiving a heating stop command from the upper-level controller, then stopping self-heating, wherein the heating stop command from the upper-level controller can be generated based on a driver's command to stop heating. In this embodiment, the process of the vehicle controller stopping self-heating includes: controlling the first power switch, the second power switch, and the third power switch to open, specifically including controlling MOSFETs S11, S21, S31, S12, S22, and S32 to turn off; and closing switch K1, at which time the motor performs its own functions in a three-wire four-wire configuration to meet the needs of the electric vehicle entering normal driving mode. In this way, this invention can also stop the self-heating of the vehicle battery according to the actual battery temperature or the user's needs.

[0160] This invention can also heat the vehicle battery based on whether the battery SOC control switch is in a closed or open state. When the switch is closed, this invention heats the vehicle battery using an inductive heating mode; when the switch is open, this invention heats the vehicle battery using a resonant heating mode. The heating current differs between these two different heating modes, for example... Figure 7 The maximum current flowing through the vehicle battery in the resonant heating mode shown in the figure can reach 200A, for example. Figure 8 The maximum current flowing through the vehicle battery in the inductive heating mode shown in the figure can reach 40A. Therefore, the embodiments of the present invention can also achieve the purpose of adjusting the battery self-heating current according to the battery SOC, thereby effectively ensuring the safety of the battery.

[0161] In summary, the present invention can also flexibly adjust the battery self-heating current according to the vehicle battery SOC and demand. When the vehicle battery SOC is safe, a higher heating rate can be achieved with a larger heating current. When the vehicle battery SOC is too high or too low, a controllable heating current can be used to achieve safer heating of the vehicle battery.

[0162] This embodiment provides a vehicle battery self-heating method, which can be used in the controller of the aforementioned vehicle battery self-heating system. Figure 6 This is a flowchart of a vehicle battery self-heating method according to an embodiment of the present invention, such as... Figure 6 As shown, the process includes the following steps:

[0163] Step S100: Receive self-heating command and vehicle battery status information sent by the battery management system. The status information includes state of charge, voltage, and battery temperature. The battery management system is used to collect the vehicle battery status information.

[0164] The battery management system involved in this invention specifically refers to a BMS (Battery Management System). In this embodiment, the BMS reads the vehicle battery temperature (Tb) and battery SOC, determines whether there is a self-heating requirement from the driver by receiving current instructions from the upper-level controller, and generates a self-heating command based on the current instructions. The upper-level controller can be, for example, a VCU (Vehicle Control Unit), which directly receives control commands from the driver. In this embodiment, the BMS sends the self-heating command, the current vehicle battery temperature (Tb), the collected vehicle battery voltage (Ubat), and the battery SOC to the motor controller, which selects the battery heating mode based on the battery SOC.

[0165] The self-heating command includes a heating start command and a heating stop command.

[0166] The embodiments of the present invention can operate when the electric vehicle is parked, enabling the vehicle battery to self-heat.

[0167] Step S200: Based on the self-heating command and / or battery temperature, determine whether to perform the step of determining the range of the vehicle battery's state of charge.

[0168] If the self-heating command is a heating start command and / or the battery temperature is less than or equal to the first preset temperature (Tb≤Tmin), then step S101 is executed to start the battery self-heating system. If the self-heating command is a heating stop command and / or the battery temperature is greater than the first preset temperature (Tb>Tmin), then the process returns to step S100.

[0169] After the battery self-heating system is activated, this embodiment can heat the vehicle battery to the expected temperature Tc. The present invention can modify the expected temperature Tc and / or the first preset temperature Tmin through instructions from the upper controller.

[0170] The first preset temperature is set according to the actual situation, for example, Tmin = -5℃ (degrees Celsius), and the expected temperature can also be set according to the actual situation, for example, Tc = 5℃.

[0171] The embodiments of the present invention can also reliably control whether the vehicle's self-heating system activates battery self-heating based on the self-heating command and / or battery temperature.

[0172] Step S101: Determine the range of the vehicle battery's state of charge. The specific implementation process of step S101 has been described in detail in this specification and will not be repeated here.

[0173] Step S102: Determine whether the state of charge of the vehicle battery is within the first preset range.

[0174] In this embodiment, if the state of charge of the vehicle battery is within the first preset range, the motor controller selects the resonant heating mode based on the battery SOC, including the following steps S103 and S104; if the state of charge of the vehicle battery is not within the first preset range, the motor controller selects the inductive heating mode based on the battery SOC, including the following steps S105, S110 and S120.

[0175] In step S103, if the state of charge of the vehicle battery is within the first preset range, the control switch is turned off. The specific implementation process of step S103 has been described in detail in this specification and will not be repeated here.

[0176] Step S104 involves sending a third control pulse to the first power switch and the fourth power switch at the second switching frequency, and sending a fourth control pulse to the second power switch and the third power switch at the second switching frequency; wherein, the first preset range is greater than a first preset value and less than a second preset value, and the difference between the phase of the third control pulse and the phase of the fourth control pulse is a second set value. The specific implementation process of step S104 has been described in detail in this specification and will not be repeated here.

[0177] Step S105: If the state of charge of the vehicle battery is within the second preset range, the control switch is closed, and the process returns to the step of determining the first switching frequency; wherein, the second preset range is less than or equal to the first preset value, or greater than or equal to the second preset value. The specific implementation process of step S105 has been described in detail in this specification and will not be repeated here.

[0178] Step S110: Determine the first switching frequency based on the vehicle battery voltage. The specific implementation process of step S110 has been described in detail in this specification and will not be repeated here.

[0179] Step S120: A first control pulse is sent to the first power switch and the fourth power switch according to the first switching frequency, and a second control pulse is sent to the second power switch and the third power switch according to the first switching frequency; wherein, the difference between the phase of the first control pulse and the phase of the second control pulse is a first set value. The specific implementation process of step S120 has been described in detail in this specification and will not be repeated here.

[0180] In the description of this specification, the references to terms such as "this embodiment," "an 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 the present invention. 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.

[0181] Furthermore, the terms "first" and "second" 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0182] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0183] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," 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 explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0184] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and all such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A vehicle battery self-heating system, characterized in that, The system includes: The vehicle battery (100) has a first end and a second end; The first switching device group (200) includes a first power switch (201) and a second power switch (202); the first source and drain of the first power switch (201) are connected to the first terminal, the second source and drain of the first power switch (201) are connected to the third source and drain of the second power switch (202), and the fourth source and drain of the second power switch (202) are connected to the second terminal. The second switching device group (300) includes a third power switch (301) and a fourth power switch (302); the fifth source-drain terminal of the third power switch (301) is connected to the first terminal, the sixth source-drain terminal of the third power switch (301) is connected to the seventh source-drain terminal of the fourth power switch (302), and the eighth source-drain terminal of the fourth power switch (302) is connected to the second terminal. Controller (400); the first gate of the first power switch (201), the second gate of the second power switch (202), the third gate of the third power switch (301) and the fourth gate of the fourth power switch (302) are respectively connected to the controller (400); The motor (500) has a first side and a second side; the second source drain and the third source drain are respectively used to connect to the first side, and the sixth source drain and the seventh source drain are respectively used to connect to the second side; The resonant capacitor (600) has a third terminal and a fourth terminal; wherein the third terminal is connected to the second side of the motor (500), and the sixth source drain and the seventh source drain are respectively connected to the fourth terminal; the motor (500) and the resonant capacitor (600) are connected in series between the first switching device group (200) and the second switching device group (300). A switch (700) is connected in parallel with the resonant capacitor (600); The controller is used to determine the range of the state of charge (SOC) of the vehicle battery. If the SOC of the vehicle battery is within a first preset range, the controller controls the switch to open and sends a third control pulse to the first power switch and the fourth power switch at a second switching frequency, and sends a fourth control pulse to the second power switch and the third power switch at the second switching frequency. The first preset range is greater than a first preset value and less than a second preset value. The difference between the phase of the third control pulse and the phase of the fourth control pulse is a second preset value. If the SOC of the vehicle battery is within a second preset range, the controller controls the switch to close, determines a first switching frequency based on the voltage of the vehicle battery, sends a first control pulse to the first power switch and the fourth power switch at the first switching frequency, and sends a second control pulse to the second power switch and the third power switch at the first switching frequency. The difference between the phase of the first control pulse and the phase of the second control pulse is a first preset value, and the second preset range is less than or equal to the first preset value, or greater than or equal to the second preset value.

2. The vehicle battery self-heating system according to claim 1, characterized in that, The motor (500) is a three-phase four-wire motor, the first side includes phase A, phase B and phase C, and the second side is the neutral line of the three-phase four-wire motor; The first power switch (201) includes a first sub-switch, a second sub-switch and a third sub-switch arranged in parallel; the second power switch (202) includes a fourth sub-switch, a fifth sub-switch and a sixth sub-switch arranged in parallel. The second source-drain of the first sub-switch and the third source-drain of the fourth sub-switch are respectively connected to phase A, the second source-drain of the second sub-switch and the third source-drain of the fifth sub-switch are respectively connected to phase B, and the second source-drain of the third sub-switch and the third source-drain of the sixth sub-switch are respectively connected to phase C.

3. The vehicle battery self-heating system according to claim 1 or 2, characterized in that, The system also includes: The coolant circulation pipeline includes a first pipeline (801), a second pipeline (802) and a third pipeline (803), wherein the coolant circulation pipeline is filled with circulating coolant; The first conduit (801) is located beside the motor (500), the second conduit (802) is located beside the resonant capacitor (600), and the third conduit (803) is located beside the vehicle battery (100).

4. The vehicle battery self-heating system according to claim 1 or 2, characterized in that, The system also includes: The DC bus capacitor (900) is connected to the first terminal and the second terminal respectively.

5. A method for self-heating a vehicle battery, characterized in that, A controller applied to a vehicle battery self-heating system, the method comprising: Determine the range of the vehicle battery's state of charge. If the state of charge of the vehicle battery is within a first preset range, the control switch is opened, and a third control pulse is sent to the first power switch and the fourth power switch at a second switching frequency, and a fourth control pulse is sent to the second power switch and the third power switch at the second switching frequency; the first preset range is greater than a first preset value and less than a second preset value, and the difference between the phase of the third control pulse and the phase of the fourth control pulse is a second set value; if the state of charge of the vehicle battery is within a second preset range, the control switch is closed, and a first switching frequency is determined based on the voltage of the vehicle battery; a first control pulse is sent to the first power switch and the fourth power switch at the first switching frequency, and a second control pulse is sent to the second power switch and the third power switch at the first switching frequency; wherein, the difference between the phase of the first control pulse and the phase of the second control pulse is a first set value, and the second preset range is less than or equal to the first preset value, or greater than or equal to the second preset value; The vehicle battery self-heating system includes: The vehicle battery (100) has a first end and a second end; The first switching device group (200) includes a first power switch (201) and a second power switch (202); the first source and drain of the first power switch (201) are connected to the first terminal, the second source and drain of the first power switch (201) are connected to the third source and drain of the second power switch (202), and the fourth source and drain of the second power switch (202) are connected to the second terminal. The second switching device group (300) includes a third power switch (301) and a fourth power switch (302); the fifth source-drain terminal of the third power switch (301) is connected to the first terminal, the sixth source-drain terminal of the third power switch (301) is connected to the seventh source-drain terminal of the fourth power switch (302), and the eighth source-drain terminal of the fourth power switch (302) is connected to the second terminal. Controller (400); the first gate of the first power switch (201), the second gate of the second power switch (202), the third gate of the third power switch (301) and the fourth gate of the fourth power switch (302) are respectively connected to the controller (400); The motor (500) has a first side and a second side; the second source drain and the third source drain are respectively used to connect to the first side, and the sixth source drain and the seventh source drain are respectively used to connect to the second side; A resonant capacitor (600) has a third terminal and a fourth terminal; wherein the third terminal is connected to the second side of the motor (500), and the sixth source drain and the seventh source drain are respectively connected to the fourth terminal; the motor and the resonant capacitor are connected in series between the first switching device group and the second switching device group; A switch (700); the switch is connected in parallel with the resonant capacitor (600).

6. The vehicle battery self-heating method according to claim 5, characterized in that, Before determining the range of the state of charge of the vehicle battery, the method further includes: The battery management system receives a self-heating command and the status information of the vehicle battery sent by the battery management system. The status information includes the state of charge, the voltage, and the battery temperature. The battery management system is used to collect the status information of the vehicle battery. Based on the self-heating command and / or the battery temperature, determine whether to execute the step of determining the range of the state of charge of the vehicle battery.

7. The vehicle battery self-heating method according to claim 5 or 6, characterized in that, The second switching frequency is half the resonant frequency of the resonant unit formed by the equivalent inductance of the motor and the resonant capacitor.

8. The vehicle battery self-heating method according to claim 5, characterized in that, Determining the first switching frequency based on the voltage of the vehicle battery includes: in, Indicates the first switching frequency. Indicates the voltage of the vehicle battery. The inductance value represents the equivalent inductance of the motor. This indicates the effective value of the self-heating current that needs to be achieved.

9. The vehicle battery self-heating method according to claim 5, characterized in that, The second switching frequency is fLC ; fLC =1 / (4π ) in, The inductance value represents the equivalent inductance of the motor. This indicates the capacitance value of the resonant capacitor.

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