Power battery AC heating circuit and electric vehicle

Abstract

An embodiment of the present application provides a power battery AC heating circuit and an electric vehicle, comprising: a three-phase motor; a three-phase inverter circuit, wherein the midpoint of each phase of the three-phase inverter circuit is respectively connected to a phase of the three-phase motor; a first battery circuit and a second battery circuit, wherein the first battery circuit and the second battery circuit are respectively connected in parallel with the three-phase inverter circuit; the first battery circuit is formed by a first energy storage device and a first secondary side of a transformer connected in series; the second battery circuit comprises: a second energy storage device and a second secondary side of the transformer connected in series; the first end of the first secondary side is connected to the first energy storage device; the first end of the second secondary side is connected to the second energy storage device; the first end of the first secondary side and the first end of the second secondary side are opposite terminals; the number of turns of the first secondary side and the number of turns of the second secondary side are the same; the first energy storage device and / or the second energy storage device are battery packs. The overall external voltage of the battery pack is not affected by the AC power, thereby preventing electrical devices on the DC bus from being affected.

Description

Technical Field

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

[0002] Electric vehicle power batteries degrade in low-temperature environments, impacting their performance and requiring heating. Existing technologies typically utilize additional electric heating devices to heat the batteries, such as using thermally sensitive ceramics (PTCs) as heating elements to heat the cold-spot fluid, which then indirectly heats the battery. This indirect heating method, which utilizes heat from the cold-spot fluid, has the following drawbacks: low heat transfer efficiency, with a significant amount of heat dissipated into the environment; and uneven battery heating, with battery cells near the water inlet heating quickly and reaching higher temperatures, while cells farther from the cold-spot fluid heat more slowly and reach lower temperatures. Consequently, the electric vehicle industry has conducted extensive research on AC heating technology for power batteries. Battery AC heating involves using a specific method to pass a high-frequency AC current through the battery, utilizing heat generated by the battery's internal resistance. A common AC heating method utilizes the electric vehicle's drive motor windings as a temporary energy storage component. The motor windings repeatedly store and release electrical energy at high frequencies, causing the battery to repeatedly charge and discharge at high frequencies, thereby achieving AC heating. However, this method has drawbacks: the high-frequency current flowing through the electric vehicle's drive motor windings and three-phase inverter causes significant heating of the drive motor and inverter, limiting the heating current. During heating, high-frequency current flows through the high-voltage system bus, causing significant fluctuations in the high-voltage DC bus voltage, which can easily affect the normal operation of other high-voltage equipment. Summary of the Invention

[0003] In view of this, the purpose of the embodiments of the present application is to provide a power battery AC heating circuit and an electric vehicle, which can prevent high-frequency current from flowing through the high-voltage system bus, causing significant fluctuations in the high-voltage system DC bus voltage, and affecting the normal operation of other high-voltage equipment.

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

[0005] Three-phase motor;

[0006] A three-phase inverter circuit, wherein the midpoint of each phase of the inverter circuit is respectively connected to one phase of the three-phase motor;

[0007] a first battery circuit and a second battery circuit, wherein the first battery circuit and the second battery circuit are respectively connected in parallel with the three-phase inverter circuit;

[0008] The first battery circuit is formed by connecting a first energy storage device and a first secondary side of a transformer in series;

[0009] The second battery circuit is formed by connecting a second energy storage device and a second secondary side of the transformer in series;

[0010] The first end of the first secondary side is connected to the first energy storage device;

[0011] The first end of the second secondary side is connected to the second energy storage device;

[0012] The first end of the first secondary side and the first end of the second secondary side are opposite ends;

[0013] The number of turns of the first secondary side is the same as the number of turns of the second secondary side;

[0014] The first energy storage device and / or the second energy storage device is a battery pack.

[0015] In the above implementation process, the first battery circuit and the second battery circuit constitute a battery pack. Since the first end of the first secondary side is connected to the first energy storage device; the first end of the second secondary side is connected to the second energy storage device; the first end of the first secondary side and the first end of the second secondary side are opposite ends; the number of turns of the first secondary side is the same as the number of turns of the second secondary side; therefore, when AC heating is performed, the voltages generated by the two secondary coils are the same in magnitude and opposite in direction, so that the overall external voltage of the battery pack will not be affected by the AC current, and it can be ensured that the AC current only flows back and forth between the two battery circuits and does not flow to the DC bus, which can avoid the electrical equipment on the DC bus being affected; when the AC heating current is not considered and the DC discharge of the battery is considered, it can be ensured that when the DC current of the same magnitude flows through the two battery pack branches, the excitation generated by the two secondary sides just cancels each other, and no choking effect is generated, thereby not affecting the dynamic characteristics of the battery's external discharge.

[0016] Furthermore, the first end of the primary side of the transformer is connected to the DC bus, the second end of the primary side of the transformer is connected to the neutral point of the motor, and the number of turns of the primary side is greater than the number of turns of the first secondary side and the number of turns of the second secondary side.

[0017] In the above implementation process, since the number of primary turns is greater than that of secondary turns, the primary current can be reduced while the secondary heating current remains constant, thereby effectively reducing the current flowing through the motor windings and inverter during heating to prevent them from overheating.

[0018] Furthermore, the primary side and the DC-isolating resonant capacitor are connected in series to form a series circuit, a first end of the series circuit is connected to the DC bus, and a second end of the series circuit is connected to the neutral point of the three-phase motor.

[0019] In this implementation, the DC-blocking resonant capacitor isolates the DC voltage to prevent transformer saturation. It also forms an LC resonant circuit with the motor's common-mode inductor. This resonance reduces the impedance of the series circuit and increases the AC voltage on the transformer's primary side. This series circuit, connected between the busbar and the neutral point of the drive motor, utilizes the AC component of the neutral-point common-mode voltage caused by the three-phase inverter switching to drive the transformer's primary side.

[0020] Furthermore, the power battery AC heating circuit includes: a capacitor circuit;

[0021] The capacitor circuit is connected in parallel to the busbar;

[0022] The capacitor circuit is formed by connecting a first capacitor and a second capacitor in series;

[0023] The second end of the primary side of the transformer is connected to the midpoint of the first capacitor and the second capacitor.

[0024] Furthermore, the first capacitor and the second capacitor have the same capacity.

[0025] In the above implementation process, on the one hand, it can ensure that the initial voltage of the DC blocking capacitor after power-on is close to the steady-state voltage of the heating condition, which can reduce the transient fluctuation of the circuit after the start of AC heating; on the other hand, the small high-frequency current flowing through the primary side can flow through the positive and negative DC bus at the same time, thereby reducing the electromagnetic interference generated to the outside to a certain extent.

[0026] Furthermore, the primary side, the DC isolation resonant capacitor and the relay are connected in series to form a series circuit, a first end of the series circuit is connected to the DC bus, and a second end of the series circuit is connected to the neutral point of the three-phase motor.

[0027] Furthermore, the first energy storage device or the second energy storage device is a capacitor.

[0028] In the above implementation process, since the heating current is a high-frequency current, a capacitor with sufficient capacity can achieve high-frequency energy storage and maintain its own voltage basically unchanged, which is similar to the effect of a battery pack.

[0029] Furthermore, the first energy storage device and the second energy storage device are battery packs, and the first energy storage device and the second energy storage device are electrically symmetrical.

[0030] In the above implementation process, the first energy storage device and the second energy storage device are both battery packs, wherein the first energy storage device is electrically charged, and the two battery packs are electrically symmetrical. When heated, the two battery packs can be heated evenly, which can extend the service life of the battery pack.

[0031] In a second aspect, an embodiment of the present application provides an electric vehicle, comprising the power battery AC heating circuit described in the first aspect.

[0032] 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.

[0033] 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

[0034] 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.

[0035] Figure 1 A schematic diagram of the structure of the power battery AC heating circuit provided in an embodiment of the present application;

[0036] Figure 2 Another structural diagram of the power battery AC heating circuit provided in an embodiment of the present application;

[0037] Figure 3 Another structural diagram of the power battery AC heating circuit provided in an embodiment of the present application;

[0038] Figure 4 Another structural schematic diagram of the power battery AC heating circuit provided in an embodiment of the present application.

[0039] Figure markings: 1-motor; 2-three-phase inverter circuit; U1-first energy storage device; U2-second energy storage device; Ls1-first secondary side; Ls2-second secondary side; Lp-primary side; Cr-DC isolation resonant capacitor; Cr1-first capacitor; Cr2-second capacitor; Cdc-filter capacitor; Q1-first switch module; Q2-second switch module: Q3-third switch module; Q4-fourth switch module; Q5-fifth switch module; Q6-sixth switch module; K-relay. DETAILED DESCRIPTION

[0040] 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.

[0041] 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.

[0042] Example 1

[0043] See also Figure 1 , an embodiment of the present application provides a power battery AC heating circuit, comprising:

[0044] Three-phase motor 1;

[0045] A three-phase inverter circuit 2, wherein the midpoint of each phase of the inverter circuit of the three-phase inverter circuit 2 is respectively connected to one phase of the three-phase motor 1;

[0046] The three-phase inverter circuit 2 is connected in parallel to the busbar. Each phase of the inverter circuit is composed of an upper switch module and a lower switch module connected in series, with each switch module also connected in parallel with a diode. The first phase circuit includes a first switch module Q1 and a second switch module Q2; the second phase circuit includes a third switch module Q3 and a fourth switch module Q4; and the third phase circuit includes a fifth switch module Q5 and a sixth switch module Q6. The upper and lower switch modules can be power devices such as insulated gate bipolar transistors (IGBTs).

[0047] a first battery circuit and a second battery circuit, wherein the first battery circuit and the second battery circuit are respectively connected in parallel with the three-phase inverter circuit 2;

[0048] The first battery circuit is formed by connecting the first energy storage device U1 and the first secondary side Ls1 of the transformer in series;

[0049] The second battery circuit is formed by connecting the second energy storage device U2 and the second secondary side Ls2 of the transformer in series;

[0050] The first end of the first secondary side Ls1 is connected to the first energy storage device U1;

[0051] A first end of the second secondary side Ls2 is connected to the second energy storage device U2;

[0052] The first end of the first secondary side Ls1 and the first end of the second secondary side Ls2 are opposite ends;

[0053] The number of winding turns of the first secondary side Ls1 is the same as the number of winding turns of the second secondary side Ls2;

[0054] The first energy storage device U1 and / or the second energy storage device U2 is a battery pack.

[0055] It can be understood that the first bus terminal of the three-phase inverter circuit 2 is connected to the positive pole (negative pole) of the busbar, and the second bus terminal of the three-phase inverter circuit 2 is connected to the negative pole (positive pole) of the busbar.

[0056] In the above implementation process, since the first end of the first secondary side Ls1 is connected to the first energy storage device U1; the first end of the second secondary side Ls2 is connected to the second energy storage device U2; the first end of the first secondary side Ls1 and the first end of the second secondary side Ls2 are opposite-name terminals; the number of turns of the first secondary side Ls1 and the number of turns of the second secondary side Ls2 are the same; therefore, when AC heating is performed, the voltages generated by the two secondary coils are the same in magnitude and opposite in direction, so that the overall external voltage of the battery pack will not be affected by the AC current, and it can be ensured that the AC current only flows back and forth between the two battery packs and does not flow to the DC bus, which can avoid the electrical equipment on the DC bus being affected; when the AC heating current is not considered and the DC discharge of the battery is considered, it can be ensured that when the DC current of the same magnitude flows through the two battery pack branches, the excitation generated by the two secondary sides just cancels each other, and no choking effect is generated, thereby not affecting the dynamic characteristics of the battery's external discharge.

[0057] Figure 1 The circuit in is equivalent to Figure 2 The circuit in the battery pack, namely the first battery circuit and the second battery circuit and Figure 1 The scheme in is similar, and the primary side Lp of the transformer is driven by an abstract AC voltage source, which is provided by the AC component of the motor common mode voltage of the store drive system in the display operation.

[0058] See also Figure 2 In one possible embodiment, a first end of the primary side Lp of the transformer is connected to the DC bus, a second end of the primary side Lp of the transformer is connected to the neutral point of the motor, and the number of turns of the primary side Lp is greater than the number of turns of the first secondary side Ls1 and the number of turns of the second secondary side Ls2.

[0059] The primary side Lp can be connected to the positive pole of the busbar or the negative pole of the busbar.

[0060] In the above implementation process, since the number of turns of the primary side Lp is greater than the number of turns of the secondary side, the primary side Lp current can be reduced when the secondary side heating current is constant, thereby effectively reducing the current flowing through the motor winding and inverter during heating to prevent them from overheating.

[0061] See also Figure 3 In one possible implementation, the primary side Lp and the DC isolation resonant capacitor Cr are connected in series to form a series circuit, a first end of the series circuit is connected to the DC bus, and a second end of the series circuit is connected to the neutral point of the three-phase motor 1.

[0062] In the above implementation, the DC-blocking resonant capacitor Cr isolates the DC voltage to prevent transformer saturation. It also forms an LC resonant circuit with the motor's common-mode inductance, reducing the impedance of the series circuit and increasing the AC voltage on the transformer's primary side, Lp. This series circuit, connected between the busbar and the neutral point of the drive motor, utilizes the AC component of the neutral-point common-mode voltage caused by the three-phase inverter switching to drive the transformer's primary side, Lp.

[0063] See also Figure 4 ,In a possible implementation, the power battery AC heating circuit includes: a capacitor circuit;

[0064] The capacitor circuit is connected in parallel with the busbar;

[0065] The capacitor circuit is composed of a first capacitor Cr1 and a second capacitor Cr2 connected in series;

[0066] The second end of the primary side Lp of the transformer is connected to the midpoint between the first capacitor Cr1 and the second capacitor Cr2 .

[0067] Furthermore, the first capacitor Cr1 and the second capacitor Cr2 have the same capacity.

[0068] In the above implementation process, on the one hand, it can ensure that the initial voltage of the DC blocking capacitor after power-on is close to the steady-state voltage of the heating condition, because the transient fluctuation of the circuit after the start of AC heating can be reduced; on the other hand, the small high-frequency current flowing through the primary side Lp can flow through the positive and negative DC bus bars at the same time, thereby reducing the electromagnetic interference generated to the outside to a certain extent.

[0069] See also Figure 1 、 Figure 3 、 Figure 4 In one possible implementation, the primary side Lp and the DC isolation resonant capacitor Cr relay K are connected in series to form a series circuit, a first end of the series circuit is connected to the DC bus, and a second end of the series circuit is connected to the neutral point of the three-phase motor 1.

[0070] In the above implementation, no battery heating is required. At this point, relay K is disconnected, and the entire high-voltage power system operates like a conventional power system, including normal charging and driving. When heating is required, relay K is closed, and the electric drive system still controls the motor according to conventional control methods (such as space vector modulation (SVPWM)). At this time, a common-mode voltage is generated at the center point of the motor. The spectrum of the common-mode voltage contains a large AC harmonic component at the inverter switching frequency. This voltage component acts on the primary Lp circuit of the transformer and generates an alternating voltage on the secondary side, thereby generating a high-frequency alternating current between the two battery packs, heating the batteries. Since the motor common-mode voltage can be generated as long as the inverter is operating, whether the vehicle is stationary or moving, the above circuit can provide AC heating for the battery regardless of whether the vehicle is stationary or moving.

[0071] See also Figure 3 In a possible implementation, the first energy storage device U1 or the second energy storage device U2 is a capacitor.

[0072] In the above implementation process, since the heating current is a high-frequency current, a capacitor with sufficient capacity can achieve high-frequency energy storage and maintain its own voltage basically unchanged, which is similar to the effect of a battery pack.

[0073] See also Figure 4 In a possible implementation, the first energy storage device U1 and the second energy storage device U2 are battery packs, and the first energy storage device U1 and the second energy storage device U2 are electrically symmetrical.

[0074] In the above implementation process, the first energy storage device U1 and the second energy storage device U2 are both battery packs, wherein the first energy storage device U1 is electrically charged, and the two battery packs are electrically symmetrical. When heated, the two battery packs can be heated evenly, which can extend the service life of the battery pack.

[0075] In a possible implementation manner, the three-phase inverter circuit further includes a filter capacitor Cdc, and the filter capacitor Cdc is connected in parallel to the bus.

[0076] Example 2

[0077] An embodiment of the present application provides an electric vehicle, comprising the power battery AC heating circuit described in Example 1.

[0078] The above are merely examples of the present application and are not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application. It should be noted that similar numbers 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.

[0079] The above are only specific embodiments of the present application, but the scope of protection of this 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 this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

[0080] 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 any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such 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 power battery AC heating circuit, characterized in that: include: Three-phase motor; A three-phase inverter circuit, wherein the midpoint of each phase of the inverter circuit is respectively connected to one phase of the three-phase motor; a first battery circuit and a second battery circuit, wherein the first battery circuit and the second battery circuit are respectively connected in parallel with the three-phase inverter circuit; The first battery circuit is formed by connecting a first energy storage device and a first secondary side of a transformer in series; The second battery circuit is formed by connecting a second energy storage device and a second secondary side of the transformer in series; The first end of the first secondary side is connected to the first energy storage device; The first end of the second secondary side is connected to the second energy storage device; The first end of the first secondary side and the first end of the second secondary side are opposite ends; The number of turns of the first secondary side is the same as the number of turns of the second secondary side; The first energy storage device and / or the second energy storage device is a battery pack; A first end of the primary side of the transformer is connected to a DC bus, a second end of the primary side of the transformer is connected to a neutral point of the motor, and the number of turns of the primary side is greater than the number of turns of the first secondary side and the number of turns of the second secondary side; The three-phase inverter circuit is connected in parallel to the busbar. The inverter circuit of each phase in the three-phase inverter circuit includes an upper switch module and a lower switch module connected in series, wherein each switch module is connected in parallel with a diode.

2. The power battery AC heating circuit according to claim 1, characterized in that: The primary side and the DC-isolating resonant capacitor are connected in series to form a series circuit, a first end of the series circuit is connected to the DC bus, and a second end of the series circuit is connected to the neutral point of the three-phase motor.

3. A power battery AC heating circuit, characterized in that: include: Three-phase motor; A three-phase inverter circuit, wherein the midpoint of each phase of the inverter circuit is respectively connected to one phase of the three-phase motor; a first battery circuit and a second battery circuit, wherein the first battery circuit and the second battery circuit are respectively connected in parallel with the three-phase inverter circuit; The first battery circuit is formed by connecting a first energy storage device and a first secondary side of a transformer in series; The second battery circuit is formed by connecting a second energy storage device and a second secondary side of the transformer in series; The first end of the first secondary side is connected to the first energy storage device; The first end of the second secondary side is connected to the second energy storage device; The first end of the first secondary side and the first end of the second secondary side are opposite ends; The number of turns of the first secondary side is the same as the number of turns of the second secondary side; The first energy storage device and / or the second energy storage device is a battery pack; The power battery AC heating circuit includes: a capacitor circuit; The capacitor circuit is connected in parallel to the busbar; The capacitor circuit is formed by connecting a first capacitor and a second capacitor in series; The second end of the primary side of the transformer is connected to the midpoint of the first capacitor and the second capacitor; The three-phase inverter circuit is connected in parallel to the busbar. The inverter circuit of each phase in the three-phase inverter circuit includes an upper switch module and a lower switch module connected in series, wherein each switch module is connected in parallel with a diode.

4. The power battery AC heating circuit according to claim 3, characterized in that: The first capacitor and the second capacitor have the same capacitance.

5. The power battery AC heating circuit according to claim 1, characterized in that: The primary side, the DC-isolating resonant capacitor, and the relay are connected in series to form a series circuit. A first end of the series circuit is connected to the DC bus, and a second end of the series circuit is connected to the neutral point of the three-phase motor.

6. The power battery AC heating circuit according to claim 5, characterized in that: The first energy storage device or the second energy storage device is a capacitor.

7. The power battery AC heating circuit according to claim 6, characterized in that: The first energy storage device and the second energy storage device are battery packs, and the first energy storage device and the second energy storage device are electrically symmetrical.

8. The power battery AC heating circuit according to any one of claims 1 to 7, characterized in that: The three-phase inverter circuit further includes a filter capacitor connected in parallel to the busbar.

9. An electric vehicle, characterized in that: The invention comprises the power battery AC heating circuit according to any one of claims 1 to 8.

Images