Battery heating device and vehicle

Abstract

The embodiment of the present application provides a battery heating device and a car, the heating device comprising: a battery pack, a three-phase inverter, and a motor; the battery pack is composed of a plurality of battery packs connected in series; the first bus terminal of the three-phase inverter is connected to the positive pole of the battery pack; the second bus terminal of the three-phase inverter is connected to the negative pole of the battery pack; the output terminal of the three-phase inverter is connected to the input terminal of the motor; the three-phase inverter is used to change the input current of the motor; the neutral point of the motor and the series connection point between any two battery packs in the battery pack form a branch; the branch includes a capacitor module. The heating device is suitable for operating at a high switching frequency, thereby reducing operating noise and enhancing the heating effect. The capacitor module can isolate the common mode voltage of DC or low frequency, so that the battery heating device does not need to control the balance of the battery cells in series, simplifying the battery pack control software and hardware; it can also quickly switch to the three-phase short-circuit state of the motor when a fault occurs during high-speed driving, without having to wait for the neutral relay to disconnect, thereby improving safety.

Description

Technical Field

[0001] The present application relates to the field of circuit technology, and in particular to a battery heating device and a vehicle. Background Art

[0002] The power batteries of new energy vehicles perform poorly at low temperatures. Therefore, the batteries need to be heated while the vehicle is driving or parked for charging. Prior art methods connect the neutral point of the motor to the midpoint of a series-connected battery pack, utilizing the midpoint current to heat the battery. However, this method suffers from low heating power at high switching frequencies. Due to non-ideal factors, even if the PWM duty cycles of the upper and lower arms of a three-phase inverter bridge are perfectly symmetrical, the average midline current will not be absolutely zero. This can lead to a capacity imbalance between the upper and lower battery packs over time. Therefore, supporting hardware and software are essential to control the average midline current to maintain a balanced capacity between the upper and lower battery cells. In addition to the three-phase inverter's own control of the average midline current, the vehicle's battery management system must simultaneously estimate the charge levels of the upper and lower battery packs and provide a reference midpoint average current value based on these charges. This significantly increases the hardware and software complexity of the battery management system. Summary of the Invention

[0003] The purpose of the embodiments of the present application is to provide a battery heating device and a vehicle.

[0004] In a first aspect, an embodiment of the present application provides a battery heating device, comprising:

[0005] Battery pack, three-phase inverter, motor;

[0006] The battery pack is formed by connecting multiple battery packs in series;

[0007] The first bus terminal of the three-phase inverter is connected to the positive electrode of the battery pack;

[0008] The second bus terminal of the three-phase inverter is connected to the negative electrode of the battery pack;

[0009] The output end of the three-phase inverter is connected to the input end of the motor;

[0010] The three-phase inverter is used to change the input current of the motor;

[0011] The neutral point of the motor and the series connection point between any two battery packs in the battery pack form a branch circuit;

[0012] The branch includes a capacitor module.

[0013] In the above implementation, the resonance between the capacitor module and the motor's common-mode inductance increases the system's heating current during high-frequency operation, making the entire device more suitable for operation in high-switching frequency environments. High switching frequencies avoid frequency bands sensitive to noise, thereby reducing acoustic noise. High-frequency currents can produce a significant skin effect, increasing the battery's internal resistance and thereby enhancing internal heating. The capacitor module isolates low-frequency common-mode voltage, allowing the battery heating device to unrestrictedly modulate the three-phase inverter using various three-phase PWM modulation methods while the vehicle is in motion. Because of the isolation provided by the capacitor module, the average branch current is guaranteed to be zero, eliminating the need for branch average current control software and hardware, simplifying the circuit. The accompanying vehicle's battery management system no longer needs to simultaneously detect the charge levels of the upper and lower battery packs and issue a midpoint average current reference value based on the charge levels, reducing the hardware and software complexity of the battery management system.

[0014] Furthermore, the capacitor module and the common-mode inductance of the motor form a resonant circuit;

[0015] The resonant frequency of the resonant circuit is higher than the switching frequency of the three-phase inverter.

[0016] Furthermore, the three-phase inverter includes: a first bridge arm, a second bridge arm and a third bridge arm;

[0017] The first bridge arm is connected to the U-phase line of the motor;

[0018] The second bridge arm is connected to the V-phase line of the motor;

[0019] The third bridge arm is connected to the W-phase line of the motor.

[0020] Furthermore, the first bridge arm, the second bridge arm and the third bridge arm respectively include:

[0021] a first power switch and a second power switch;

[0022] The drain of the first power switch is connected to the first bus terminal;

[0023] The source of the first power switch is connected to the drain of the second power switch;

[0024] The source of the second power switch is connected to the second bus terminal;

[0025] The source of the first power switch of the first bridge arm is connected to the U-phase line;

[0026] The source of the first power switch of the second bridge arm is connected to the V-phase line;

[0027] The source of the first power switch of the third bridge arm is connected to the W-phase line.

[0028] Furthermore, the branch circuit further includes a relay, and the relay and the capacitor module are connected in series.

[0029] Furthermore, the first bridge arm, the second bridge arm and the third bridge arm further include: a first diode and a second diode respectively;

[0030] an anode of the first diode and a drain of the first power switch;

[0031] a cathode of the first diode and a source of the first power switch;

[0032] an anode of the second diode and a drain of the second power switch;

[0033] A cathode of the second diode and a source of the second power switch.

[0034] Furthermore, the battery pack is formed by connecting a plurality of batteries in parallel.

[0035] Furthermore, when the device is working, the three-phase inverter is driven by a modulation wave selected from SPWM, SVPWM, and DPWM.

[0036] Furthermore, the battery pack is formed by two battery groups connected in series.

[0037] In a second aspect, an embodiment of the present application provides a car, comprising the battery heating device described in the first aspect.

[0038] Other features and advantages disclosed in the present application will be described in the following description, or some features and advantages can be inferred or determined without doubt from the description, or can be learned by implementing the above-mentioned technology disclosed in the present application.

[0039] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A schematic structural diagram of a battery heating device provided in an embodiment of the present application;

[0042] Figure 2 Another structural schematic diagram of the battery heating device provided in an embodiment of the present application;

[0043] Figure 3 Schematic diagram of the relationship between switching frequency and branch resonant current.

[0044] Label: 1-battery pack; 2-three-phase inverter; 21-first bridge arm; 22-second bridge arm; 23-third bridge arm; 211-first power switch; 212-second power switch; 3-motor; 4-capacitor module; 5-relay. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0046] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0047] Example 1

[0048] See also Figure 1 , an embodiment of the present application provides a battery heating device, comprising:

[0049] Battery pack 1, three-phase inverter 2, motor 3;

[0050] The battery pack 1 is composed of multiple battery packs connected in series;

[0051] The first bus terminal of the three-phase inverter 2 is connected to the positive electrode of the battery pack 1;

[0052] The second bus terminal of the three-phase inverter 2 is connected to the negative electrode of the battery pack 1;

[0053] The output end of the three-phase inverter 2 is connected to the input end of the motor 3;

[0054] The three-phase inverter 2 is used to change the input current of the motor 3;

[0055] The motor 3 is star-connected;

[0056] The neutral point of the motor 3 and the series connection point between any two battery packs in the battery pack form a branch circuit;

[0057] The branch includes a capacitor module 4 .

[0058] It can be understood that the three-phase inverter 2 is connected to a control circuit (not shown in the figure).

[0059] In the above implementation process, the resonance between the capacitor module 4 and the common-mode inductance of the motor 3 can increase the heating current of the system when working at high frequency, making the entire device more suitable for working in a high switching frequency environment. The high switching frequency can avoid the frequency band where the human ear is sensitive to noise, thereby reducing acoustic noise. High-frequency current will produce a significant skin effect, increase the internal resistance of the battery, and thus enhance the internal resistance heating of the battery. The capacitor module 4 can isolate the low-frequency common-mode voltage, so that the battery heating device can use various types of three-phase PWM modulation to modulate the three-phase inverter 2 without restriction in the driving state. Because of the isolation effect of the capacitor module 4, the average value of the branch current is definitely zero, so there is no need to set the branch average current control software and hardware, which simplifies the circuit. The battery management system of the supporting car does not need to detect the power of the upper and lower battery packs at the same time, and give the midpoint average current reference value instruction based on the power, reducing the hardware complexity and software complexity of the battery management system.

[0060] Furthermore, the capacitor module 4 and the common mode inductance of the motor 3 form a resonant circuit;

[0061] The resonant frequency of the resonant circuit is higher than the switching frequency of the three-phase inverter 2 .

[0062] Furthermore, the three-phase inverter includes: a first bridge arm 21, a second bridge arm 22 and a third bridge arm 23;

[0063] The first bridge arm 21 is connected to the U-phase line of the motor 3;

[0064] The second bridge arm 22 is connected to the V-phase line of the motor 3;

[0065] The third bridge arm 23 is connected to the W-phase line of the motor 3 .

[0066] In the above implementation process, by adjusting the current through the first bridge arm 21 , the second bridge arm 22 and the third bridge arm 23 , the magnitude of the current flowing into the motor 3 can be changed, thereby changing the output torque of the motor 3 .

[0067] It can be understood that the first bridge arm 21, the second bridge arm 22 and the third bridge arm 23 are also connected to the control circuit, which forms a motor controller for adjusting the current passing through the motor.

[0068] Furthermore, the first bridge arm 21, the second bridge arm 22 and the third bridge arm 23 further include: a first diode and a second diode;

[0069] an anode of the first diode and a drain of the first power switch 211;

[0070] a cathode of the first diode and a source of the first power switch 211;

[0071] an anode of the second diode and a drain of the second power switch 212;

[0072] The cathode of the second diode and the source of the second power switch 212 .

[0073] In the above implementation process, the first diode and the second diode are used to protect the circuit, which can prevent high voltage from breaking down the power switch.

[0074] Furthermore, the battery pack is formed by connecting a plurality of batteries in parallel.

[0075] It is understandable that the battery pack 1 includes a plurality of battery groups connected in series, and each battery group includes a plurality of batteries connected in parallel.

[0076] As a preferred embodiment, the number of battery packs between the connection point between the branch and the battery pack 1 and the first end of the battery pack 1 is equal to the number of battery packs between the connection point between the battery pack 1 and the second end of the battery pack 1. Based on this, uniform heating can be ensured.

[0077] It should be noted that the embodiments of the present application do not limit one end of the branch circuit to being connected to the midpoint of the battery pack 1. That is, the number of battery packs between the connection point between the branch circuit and the battery pack 1 and the first end of the battery pack 1 and the number of battery packs between the connection point between the battery pack 1 and the second end of the battery pack 1 may not be equal.

[0078] During operation, the three-phase inverter is driven by one of the modulation waveforms: SPWM, SVPWM, or DPWM. This results in improved motor drive performance. For example, in SVPWM modulation mode, the three-phase inverter 2 can output a higher AC voltage to the motor, thereby enabling motor 3 to output greater power. SVPWM also results in smaller motor current ripple, thereby improving the switching acoustic noise of motor 3. DPWM means that the three-phase inverter 2 can reduce switching losses, thereby lowering its own heat, or output a higher current to motor 3 to increase motor torque and power.

[0079] Furthermore, the branch circuit further includes a relay 5, and the relay 5 and the capacitor module are connected in series.

[0080] In the above implementation process, the battery heating function can be turned on and off by opening and closing the relay 5.

[0081] In the prior art, vehicles are generally suitable for permanent magnet synchronous motors. For a car equipped with a permanent magnet synchronous motor, if a fault occurs in the three-phase inverter 2, the motor itself, or other related components at high speed, it is necessary to control the three-phase inverter 2 to allow the motor 3 to enter a three-phase short-circuit state. Therefore, if heating is performed while driving, once a fault occurs and the motor 3 needs to enter a three-phase short-circuit state, the relay 5 must be disconnected first. Only after confirming that the relay 5 is disconnected can the motor 3 enter a three-phase short-circuit state. Otherwise, the voltage at the battery series connection point directly acts on both ends of the common-mode inductor, and the motor 3 will instantly generate a huge common-mode current that will burn the motor 3. In this embodiment, due to the action of the capacitor module 4, the battery voltage is blocked by the capacitor module 4, so the motor 3 can directly enter a three-phase short-circuit state without having to wait for the relay 5 to disconnect, which significantly increases the safety of the vehicle.

[0082] In a possible implementation, the capacitor module 4 includes a first capacitor connected to the relay 5 .

[0083] Based on the above-mentioned embodiments, the working principle of the circuit is described in the embodiments of the present application to further illustrate the beneficial effects of the battery heating device.

[0084] Based on the resonance of the common-mode inductance of the motor 3 and the capacitor module 4, the natural resonant frequency of the device can be obtained by the following formula:

[0085]

[0086] Among them, L N is the common mode inductance of the motor 3 (which may include the common mode inductance generated by the winding of the motor 3, the stray inductance of the wire or the inductance added additionally at the neutral point of the motor 3, which is not shown in the schematic diagram), C N is the capacitance value of the capacitor module 4.

[0087] The expression of the heating current in the device is:

[0088]

[0089] Among them, U B is the voltage of the entire battery pack 1; f s is the switching frequency of the power switch in the three-phase inverter 2; for example, the capacitance value L of the inductor is taken N =15uH, the capacitance value of capacitor module 4 CN = 7.5uF, at this time the natural resonant frequency of the device f N is 15kHz.

[0090] The relationship between switching frequency and branch resonant current is as follows: Figure 3As shown. Under normal circumstances, when the three-phase inverter 2 drives the motor and is not heating the battery, its switching frequency is around 10kHz. This frequency may vary depending on the operating conditions (generally, the switching frequency is lowered to reduce losses). When heating is required, the switching frequency is increased to a resonant frequency close to 15kHz. For example, adjusting the switching frequency to 13kHz increases the effective value of the branch current to 400A. Such a large current can quickly heat the battery. By adjusting the switching frequency, the effective value of the branch current can be controlled, thereby adjusting the battery heating frequency. If heating is not required at all, the branch relay is disconnected.

[0091] Furthermore, the capacitance of capacitor module 4 allows the resonance point of the resonant circuit to be at several thousand hertz, even exceeding 10kHz, far exceeding the electrical frequency of the current in motor 3 (for example, a four-pole motor at 15,000 rpm has an electrical frequency fac = 1kHz). At low frequencies, the resonant network behaves as a capacitor, presenting a large impedance. At this time, the low-frequency common-mode voltage can only generate a small low-frequency common-mode current, which does not affect the operation of motor 3, allowing the above circuit to operate normally while the vehicle is in motion.

[0092] Ignoring the internal resistance of the battery, under SVPWM modulation, the fundamental amplitude of the low-frequency common-mode current generated by the low-frequency common-mode voltage is:

[0093]

[0094] For example, L N =15uH, C N =7.5uF, f N At this time, it is 15kHz, and at the highest speed of 15000rpm (f ac =1kHz, voltage utilization factor m=1), the low-frequency common-mode current amplitude is 5.4A, which is completely negligible. At other speeds, the low-frequency common-mode current is even lower. Therefore, after adding capacitor module 4, whether SPWM, SVPWM, or various DPWM modes are used in the vehicle operation state, the low-frequency common-mode voltage can be isolated, allowing the free selection of three-phase PWM modulation mode during driving, and taking full advantage of various three-phase PWM modulation modes.

[0095] Example 2

[0096] An embodiment of the present application provides a car, comprising the battery heating device of embodiment 1.

[0097] The foregoing is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures.

[0098] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0099] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

Claims

1. A battery heating device, characterized in that: include: Battery pack, three-phase inverter, motor; The battery pack is formed by connecting multiple battery packs in series; The first bus terminal of the three-phase inverter is connected to the positive electrode of the battery pack; The second bus terminal of the three-phase inverter is connected to the negative electrode of the battery pack; The output end of the three-phase inverter is connected to the input end of the motor; The three-phase inverter is used to change the input current of the motor; The neutral point of the motor and the series connection point between any two battery packs in the battery pack form a branch circuit; The branch includes a capacitor module, and the number of battery packs between the connection point between the branch and the battery pack and the first end of the battery pack is equal to the number of battery packs between the connection point and the second end of the battery pack.

2. The battery heating device according to claim 1, characterized in that: The capacitor module and the common mode inductance of the motor form a resonant circuit; The resonant frequency of the resonant circuit is higher than the switching frequency of the three-phase inverter.

3. The battery heating device according to claim 1, characterized in that: The three-phase inverter includes: a first bridge arm, a second bridge arm and a third bridge arm; The first bridge arm is connected to the U-phase line of the motor; The second bridge arm is connected to the V-phase line of the motor; The third bridge arm is connected to the W-phase line of the motor.

4. The battery heating device according to claim 3, characterized in that: The first bridge arm, the second bridge arm and the third bridge arm respectively include: a first power switch and a second power switch; The drain of the first power switch is connected to the first bus terminal; The source of the first power switch is connected to the drain of the second power switch; The source of the second power switch is connected to the second bus terminal; The source of the first power switch of the first bridge arm is connected to the U-phase line; The source of the first power switch of the second bridge arm is connected to the V-phase line; The source of the first power switch of the third bridge arm is connected to the W-phase line.

5. The battery heating device according to claim 1, characterized in that: The branch further includes a relay, and the relay and the capacitor module are connected in series.

6. The battery heating device according to claim 4, characterized in that: The first bridge arm, the second bridge arm and the third bridge arm further include: a first diode and a second diode respectively; an anode of the first diode and a drain of the first power switch; a cathode of the first diode and a source of the first power switch; an anode of the second diode and a drain of the second power switch; A cathode of the second diode and a source of the second power switch.

7. The battery heating device according to claim 1, characterized in that: The battery pack is formed by connecting a plurality of batteries in parallel.

8. The battery heating device according to any one of claims 1 to 7, characterized in that: When the device is working, the three-phase inverter is driven by a modulation wave selected from SPWM, SVPWM, and DPWM.

9. The battery heating device according to any one of claims 1 to 7, characterized in that: include: The battery pack is formed by two battery groups connected in series.

10. An automobile, characterized in that: The battery heating device comprises the battery heating device according to any one of claims 1 to 9.

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