Battery heating system and method for an electric vehicle

Abstract

The application provides a battery heating system and method for an electric vehicle, the battery heating system comprising a battery, a bus capacitor, a three-level driving circuit, and a midpoint current amplification module, the three-level driving circuit comprising a first vertical tube circuit, a second vertical tube circuit, and a third vertical tube circuit; the bus capacitor comprising an upper bridge capacitor and a lower bridge capacitor, the upper bridge capacitor and an upper bridge part of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit forming an upper bridge circuit, the lower bridge capacitor and a lower bridge part of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit forming a lower bridge circuit; the upper bridge capacitor and the lower bridge capacitor being connected to each other and in parallel with the battery, so that a midpoint potential between the upper bridge capacitor and the lower bridge capacitor forms a midpoint current; the midpoint current amplification module being arranged between the midpoint potential and a three-phase circuit of a motor, increasing the midpoint current, so that the current flowing through the battery is increased to heat the battery, thereby solving the energy loss problem of the midpoint current and the preheating requirement of the battery in winter.

Description

Technical Field

[0001] This invention relates to the field of electric vehicles, and more particularly to a battery heating system and method for electric vehicles. Background Technology

[0002] In a three-phase circuit system, the neutral point current is defined as the current flowing through the neutral point (or midpoint). This phenomenon mainly occurs in three-phase four-wire or three-level circuit structures, and its cause is usually related to the asymmetry of the three-phase load or neutral point grounding. Taking a transformer as an example, under normal operating conditions, the neutral point current should theoretically be zero. However, under asymmetrical load conditions, the neutral point current may rise to 25% of the rated current. The resulting low-frequency neutral point current generates heat when passing through the bus capacitor due to the presence of parasitic resistance, leading to capacitor heating and energy loss. It may also cause voltage imbalance in the bus capacitor, thereby affecting the stability and safety of the circuit.

[0003] Traditional methods for effectively controlling the neutral point current include: using redundant small-vector space vector modulation (SVM) technology to regulate the neutral point current, although this technique is only applicable to three-phase three-wire systems; or employing a modulation strategy based on neutral point current feedback (e.g., differential control in NPC inverters), which suppresses the neutral point current by adjusting the three-phase modulation waves in real time to balance the capacitor voltage difference. In summary, managing and reducing the neutral point current requires precise control (such as optimizing the modulation strategy) and appropriate equipment selection (e.g., using large-section conductors and dedicated instrument transformers) to achieve a balance between efficiency and safety.

[0004] To address the challenges of suppressing midpoint current, this invention proposes an innovative method for utilizing midpoint current. This method not only solves the energy loss problem caused by midpoint current but also takes into account the need for battery preheating in winter. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a battery heating system and method for electric vehicles, which can simultaneously solve the energy loss problem of midpoint current and the preheating requirement of battery in winter.

[0006] This invention discloses a battery heating system for an electric vehicle, comprising a battery, a bus capacitor, a three-level drive circuit, and a midpoint current amplification module.

[0007] The three-level drive circuit includes a first vertical transistor circuit, a second vertical transistor circuit, and a third vertical transistor circuit;

[0008] The bus capacitor includes an upper bridge capacitor and a lower bridge capacitor. The upper bridge capacitor, together with the upper bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, constitutes the upper bridge circuit. The lower bridge capacitor, together with the lower bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, constitutes the lower bridge circuit. The upper bridge capacitor and the lower bridge capacitor are connected to each other and connected in parallel with the battery, so that a midpoint current is formed at the midpoint potential between the upper bridge capacitor and the lower bridge capacitor.

[0009] The midpoint current amplification module is located between the midpoint potential and the three-phase circuit of the motor to increase the midpoint current, thereby increasing the current flowing through the battery to heat the battery.

[0010] Preferably, the battery includes an upper bridge battery and a lower bridge battery. The negative terminal of the upper bridge battery is connected to the midpoint potential, and the positive terminal is connected to the upper bridge circuit. The positive terminal of the lower bridge battery is connected to the midpoint potential, and the negative terminal is connected to the lower bridge circuit.

[0011] The midpoint current amplification module includes a first horizontal tube amplification phase, a second horizontal tube amplification phase, and a third horizontal tube amplification phase, wherein...

[0012] The first horizontal tube amplification phase includes a first diode, a second diode, a first switch, and a second switch. The first switch is connected in parallel with the first diode, and the negative terminal of the first diode is connected to the midpoint potential. One end of the second switch is connected to the first switch, and the other end is connected to the first vertical tube circuit. The positive terminal of the second diode is connected to the positive terminal of the first diode, and the negative terminal is connected to the first vertical tube circuit.

[0013] The second horizontal tube amplification phase includes a third diode, a fourth diode, a third switch, and a fourth switch. The third switch is connected in parallel with the third diode, and the negative terminal of the third diode is connected to the midpoint potential. One end of the fourth switch is connected to the third switch, and the other end is connected to the second vertical tube circuit. The positive terminal of the fourth diode is connected to the positive terminal of the third diode, and the negative terminal is connected to the second vertical tube circuit.

[0014] The third horizontal tube amplification phase includes a fifth diode, a sixth diode, a fifth switch, and a sixth switch. The fifth switch is connected in parallel with the fifth diode, and the negative terminal of the fifth diode is connected to the midpoint potential. One end of the sixth switch is connected to the fifth switch, and the other end is connected to the third vertical tube circuit. The positive terminal of the sixth diode is connected to the positive terminal of the fifth diode, and the negative terminal is connected to the third vertical tube circuit.

[0015] Preferably, the upper bridge capacitor and the lower bridge capacitor are in common mode. When the upper bridge capacitor and the lower bridge capacitor are injected in common mode, one of the first vertical transistor circuit, the second vertical transistor circuit and the third vertical transistor circuit switches to the on / off state, so that the average output voltage of the bus capacitor remains unchanged while the midpoint current is increased.

[0016] Preferably, it also includes a motor and a motor controller, with the motor connected to the motor's three-phase circuit;

[0017] The motor controller has a pre-stored constant torque curve calibration table. The motor controller selects the d-axis current Id and q-axis current Iq at the operating point with the largest midpoint current in the constant torque curve calibration table.

[0018] Preferably, a first wire inductor is also connected between the upper bridge battery and the upper bridge capacitor;

[0019] A second wire inductor is also connected between the lower bridge battery and the lower bridge capacitor, and one end of the second wire inductor is connected to the midpoint potential;

[0020] The upper bridge capacitor and the first wire inductance form a first parallel resonant circuit, and the first current of the first parallel resonant circuit heats the upper bridge battery.

[0021] The lower bridge capacitor and the second wire inductance form a second parallel resonant circuit, and the second current in the second parallel resonant circuit heats the lower bridge battery.

[0022] This invention also discloses a method for heating the battery of an electric vehicle, comprising the following steps:

[0023] The system includes a battery heating system, comprising a battery, a bus capacitor, a three-level drive circuit, and a midpoint current amplification module.

[0024] The three-level drive circuit includes a first vertical transistor circuit, a second vertical transistor circuit, and a third vertical transistor circuit;

[0025] The bus capacitor includes an upper bridge capacitor and a lower bridge capacitor. The upper bridge capacitor, together with the upper bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, constitutes the upper bridge circuit. The lower bridge capacitor, together with the lower bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, constitutes the lower bridge circuit. The upper bridge capacitor and the lower bridge capacitor are connected to each other and connected in parallel with the battery, so that a midpoint current is formed at the midpoint potential between the upper bridge capacitor and the lower bridge capacitor.

[0026] The midpoint current amplification module is located between the midpoint potential and the three-phase circuit of the motor to increase the midpoint current, thereby increasing the current flowing through the battery to heat the battery.

[0027] Preferably, the step of configuring the battery heating system includes:

[0028] The battery configuration includes an upper bridge battery and a lower bridge battery. The negative terminal of the upper bridge battery is connected to the midpoint potential, and the positive terminal is connected to the upper bridge circuit. The positive terminal of the lower bridge battery is connected to the midpoint potential, and the negative terminal is connected to the lower bridge circuit.

[0029] The midpoint current amplification module is configured with a first horizontal tube amplification phase, a second horizontal tube amplification phase, and a third horizontal tube amplification phase, wherein...

[0030] The configuration of the first horizontal tube amplification phase includes a first diode, a second diode, a first switch, and a second switch. The first switch is connected in parallel with the first diode, and the negative terminal of the first diode is connected to the midpoint potential. One end of the second switch is connected to the first switch, and the other end is connected to the first vertical tube circuit. The positive terminal of the second diode is connected to the positive terminal of the first diode, and the negative terminal is connected to the first vertical tube circuit.

[0031] The second horizontal tube amplification phase includes a third diode, a fourth diode, a third switch, and a fourth switch. The third switch is connected in parallel with the third diode, and the negative terminal of the third diode is connected to the midpoint potential. One end of the fourth switch is connected to the third switch, and the other end is connected to the second vertical tube circuit. The positive terminal of the fourth diode is connected to the positive terminal of the third diode, and the negative terminal is connected to the second vertical tube circuit.

[0032] The third horizontal tube amplification phase includes a fifth diode, a sixth diode, a fifth switch, and a sixth switch. The fifth switch is connected in parallel with the fifth diode, and the negative terminal of the fifth diode is connected to the midpoint potential. One end of the sixth switch is connected to the fifth switch, and the other end is connected to the third vertical tube circuit. The positive terminal of the sixth diode is connected to the positive terminal of the fifth diode, and the negative terminal is connected to the third vertical tube circuit.

[0033] Preferably, the step of configuring the battery heating system includes:

[0034] The upper and lower bridge capacitors are configured to operate in common mode. When the upper and lower bridge capacitors are injected in common mode, one of the first, second, and third vertical transistor circuits switches to the on / off state, thereby increasing the midpoint current while keeping the average output voltage of the bus capacitor constant.

[0035] Preferably, the step of configuring the battery heating system further includes:

[0036] Configure the motor and motor controller, and connect the motors to each other in a three-phase circuit.

[0037] The motor controller is configured to have a pre-stored constant torque curve calibration table. The motor controller selects the d-axis current Id and q-axis current Iq at the operating point with the largest midpoint current in the constant torque curve calibration table.

[0038] Preferably, the step of configuring the battery heating system includes:

[0039] A first wire inductor is also connected between the upper bridge battery and the upper bridge capacitor;

[0040] A second wire inductor is also connected between the lower bridge battery and the lower bridge capacitor, and one end of the second wire inductor is connected to the midpoint potential;

[0041] The upper bridge capacitor and the first wire inductance are configured to form a first parallel resonant circuit, and the first current of the first parallel resonant circuit heats the upper bridge battery.

[0042] The lower bridge capacitor and the second wire inductor are configured to form a second parallel resonant circuit, and the second current of the second parallel resonant circuit heats the lower bridge battery.

[0043] Compared with existing technologies, the above technical solution has the following advantages:

[0044] In electric vehicle applications, an unexpected method of amplifying the midpoint current was used to heat the current, thus avoiding the low-temperature problem that easily occurs in winter.

[0045] Suitable for motor drive circuits of various types and topologies;

[0046] At the same average differential output voltage, a larger midpoint current is generated;

[0047] The upper and lower bridge batteries can alternately output and recover energy, and the midpoint current delivered to the battery can be maximized. Attached Figure Description

[0048] Figure 1 A circuit diagram of the battery heating system is shown in a preferred embodiment of the present invention. Detailed Implementation

[0049] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0050] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0051] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0052] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if," as used herein, can be interpreted as "when," "in response to determination," or "when," or "in the event of a determination."

[0053] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not 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.

[0054] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0055] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0056] See Figure 1The diagram shows a circuit structure schematic of a battery heating system according to a preferred embodiment of the present invention. In this embodiment, the battery heating system of an electric vehicle includes a battery, a bus capacitor, a three-level drive circuit, and a midpoint current amplification module. The battery is connected to the bus capacitor so that when there is a voltage difference on both sides of the bus capacitor (i.e., when a midpoint current is generated), the generated midpoint current will flow through the battery, thereby generating heat in the battery and preheating the battery. To achieve the above objectives and better heat the battery, the three-level drive circuit includes a first vertical transistor circuit, a second vertical transistor circuit, and a third vertical transistor circuit. The bus capacitor includes an upper bridge capacitor and a lower bridge capacitor. The upper bridge capacitor, together with the upper bridge portions of the first, second, and third vertical transistor circuits, forms the upper bridge circuit. The lower bridge capacitor, together with the lower bridge portions of the first, second, and third vertical transistor circuits, forms the lower bridge circuit. The upper and lower bridge capacitors are interconnected and connected in parallel with the battery, so that a midpoint current is formed at the midpoint potential between the upper and lower bridge capacitors. The midpoint current amplification module is located between the midpoint potential and the three-phase circuit of the motor to increase the midpoint current, thereby increasing the current flowing through the battery to heat it. When the midpoint current is formed, the current at the midpoint potential will flow along the direction of the upper bridge battery and upper bridge capacitor on the upper bridge side, and along the direction of the lower bridge battery and lower bridge capacitor on the lower bridge side (in this case, the midpoint potential is at the midpoint between the upper and lower bridge batteries). It is understandable that the current flowing through the upper bridge battery and the current flowing through the lower bridge battery can be different. With the above configuration, the midpoint current, which was originally considered to have a negative impact, will be used for a beneficial purpose. It not only solves the problem of voltage imbalance between the upper and lower bridge capacitors of the bus capacitor, but also plays a role in heating the battery.

[0057] In a preferred embodiment, see further. Figure 1The battery includes an upper bridge battery and a lower bridge battery. The negative terminal of the upper bridge battery is connected to the midpoint potential, and the positive terminal is connected to the upper bridge circuit. The positive terminal of the lower bridge battery is connected to the midpoint potential, and the negative terminal is connected to the lower bridge circuit. The midpoint current amplification module includes a first horizontal tube amplification phase, a second horizontal tube amplification phase, and a third horizontal tube amplification phase. The first horizontal tube amplification phase includes a first diode, a second diode, a first switch, and a second switch. The first switch and the first diode are connected in parallel, and the negative terminal of the first diode is connected to the midpoint potential. One end of the second switch is connected to the first switch, and the other end is connected to the first vertical tube circuit. The positive terminal of the second diode is connected to the positive terminal of the first diode, and the negative terminal is connected to the first vertical tube circuit. The second horizontal tube amplification phase includes... The circuit consists of a third diode, a fourth diode, a third switch, and a fourth switch. The third switch is connected in parallel with the third diode, and the cathode of the third diode is connected to the midpoint potential. One end of the fourth switch is connected to the third switch, and the other end is connected to the second vertical transistor circuit. The anode of the fourth diode is connected to the anode of the third diode, and the cathode is connected to the second vertical transistor circuit. The third horizontal transistor amplification phase includes a fifth diode, a sixth diode, a fifth switch, and a sixth switch. The fifth switch is connected in parallel with the fifth diode, and the cathode of the fifth diode is connected to the midpoint potential. One end of the sixth switch is connected to the fifth switch, and the other end is connected to the third vertical transistor circuit. The anode of the sixth diode is connected to the anode of the fifth diode, and the cathode is connected to the third vertical transistor circuit. By turning the first, second, and third horizontal transistor amplification phases on and off, the midpoint current can be shifted within the three phases of the three-level drive circuit, preventing heat concentration.

[0058] More preferably, the upper and lower bridge capacitors are in common-mode. When common-mode injection occurs between the upper and lower bridge capacitors, one of the first, second, and third vertical transistor circuits switches between on and off states (toggle scheme). This increases the midpoint current while keeping the average output voltage of the bus capacitor constant. For example, the amplitude of the midpoint current varies under different common-mode injection schemes. Especially when Ucm is greater than 0.25, a larger midpoint current amplitude can be obtained, achieving both amplification and heating effects. In other words, in small-scale tuning, if the consistency of the differential mode output of the current phase is to be ensured, common-mode injection has a relatively small impact on the midpoint current. When one phase toggles, the midpoint current can be increased. Especially when the average output voltage remains constant, the amplification effect of the midpoint current can also be achieved.

[0059] Preferably or optionally, the battery heating system also includes a motor and a motor controller, with the motors connected to each other via a three-phase circuit. The motor controller has a pre-stored constant torque curve calibration table, and selects the d-axis current Id and q-axis current Iq at the operating point with the largest midpoint current in the constant torque curve calibration table. Under normal control, the usual practice in the constant torque curve calibration table is to select the operating point that minimizes the midpoint current for Id and Iq. However, to heat both the battery and the motor simultaneously, it is preferable to select the operating point with the largest midpoint current.

[0060] On the other hand, a first inductor is connected between the upper bridge battery and the upper bridge capacitor; a second inductor is connected between the lower bridge battery and the lower bridge capacitor, with one end of the second inductor connected to the midpoint potential. The upper bridge capacitor and the first inductor form a first parallel resonant circuit, and the first current of the first parallel resonant circuit heats the upper bridge battery; the lower bridge capacitor and the second inductor form a second parallel resonant circuit, and the second current of the second parallel resonant circuit heats the lower bridge battery. In other words, the parallel resonant circuit formed by the bus capacitor and the inductor, when a suitable frequency is selected, can excite a larger battery current with a smaller capacitor current, thereby forming an oscillating circuit relying on the bus capacitor. This is completely different from the existing method of energy exchange, which generally uses motor windings, and does not involve heating the motor first and then heating the battery.

[0061] This invention also discloses a battery heating method for an electric vehicle, comprising the following steps: configuring a battery heating system, the battery heating system including a battery, a bus capacitor, a three-level drive circuit, and a midpoint current amplification module; the three-level drive circuit including a first vertical tube circuit, a second vertical tube circuit, and a third vertical tube circuit; the bus capacitor including an upper bridge capacitor and a lower bridge capacitor, the upper bridge capacitor forming an upper bridge circuit with the upper bridge portions of the first, second, and third vertical tube circuits, and the lower bridge capacitor forming a lower bridge circuit with the lower bridge portions of the first, second, and third vertical tube circuits; the upper bridge capacitor and the lower bridge capacitor being interconnected and connected in parallel with the battery, such that a midpoint current is formed at the midpoint potential between the upper bridge capacitor and the lower bridge capacitor; the midpoint current amplification module being located between the midpoint potential and the three-phase circuit of the motor, increasing the midpoint current, thereby increasing the current flowing through the battery to heat the battery.

[0062] Preferably, the step of configuring the battery heating system includes: configuring the battery to include an upper bridge battery and a lower bridge battery, wherein the negative terminal of the upper bridge battery is connected to the midpoint potential and the positive terminal is connected to the upper bridge circuit, the positive terminal of the lower bridge battery is connected to the midpoint potential and the negative terminal is connected to the lower bridge circuit; configuring the midpoint current amplification module to include a first horizontal tube amplification phase, a second horizontal tube amplification phase and a third horizontal tube amplification phase, wherein configuring the first horizontal tube amplification phase includes a first diode, a second diode, a first switch and a second switch, the first switch and the first diode are connected in parallel, and the negative terminal of the first diode is connected to the midpoint potential, one end of the second switch is connected to the first switch and the other end is connected to the first vertical tube circuit, the positive terminal of the second diode is connected to the positive terminal of the first diode, and the negative terminal is connected to the first vertical tube circuit; The second horizontal tube amplification phase includes a third diode, a fourth diode, a third switch, and a fourth switch. The third switch is connected in parallel with the third diode, and the negative terminal of the third diode is connected to the midpoint potential. One end of the fourth switch is connected to the third switch, and the other end is connected to the second vertical tube circuit. The positive terminal of the fourth diode is connected to the positive terminal of the third diode, and the negative terminal is connected to the second vertical tube circuit. The third horizontal tube amplification phase includes a fifth diode, a sixth diode, a fifth switch, and a sixth switch. The fifth switch is connected in parallel with the fifth diode, and the negative terminal of the fifth diode is connected to the midpoint potential. One end of the sixth switch is connected to the fifth switch, and the other end is connected to the third vertical tube circuit. The positive terminal of the sixth diode is connected to the positive terminal of the fifth diode, and the negative terminal is connected to the third vertical tube circuit.

[0063] Preferably, the steps of configuring the battery heating system include: configuring the upper bridge capacitor and the lower bridge capacitor to be in common mode; when the upper bridge capacitor and the lower bridge capacitor are injected in common mode, one of the first vertical transistor circuit, the second vertical transistor circuit and the third vertical transistor circuit switches to the on / off state, so that the average output voltage of the bus capacitor remains unchanged while the midpoint current is increased.

[0064] Preferably, the steps of configuring the battery heating system further include: configuring a motor and a motor controller, connecting the motors to each other in a three-phase circuit; configuring the motor controller to have a pre-stored constant torque curve calibration table, and selecting the d-axis current Id and q-axis current Iq at the operating point with the largest midpoint current in the constant torque curve calibration table.

[0065] Preferably, the steps of configuring the battery heating system include: configuring a first wire inductor to connect the upper bridge battery and the upper bridge capacitor; configuring a second wire inductor to connect the lower bridge battery and the lower bridge capacitor, with one end of the second wire inductor connected to the midpoint potential; configuring the upper bridge capacitor and the first wire inductor to form a first parallel resonant circuit, with the first current of the first parallel resonant circuit heating the upper bridge battery; configuring the lower bridge capacitor and the second wire inductor to form a second parallel resonant circuit, with the second current of the second parallel resonant circuit heating the lower bridge battery.

[0066] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A battery heating system for an electric vehicle, characterized in that, This includes the battery, bus capacitor, three-level drive circuit, and midpoint current amplification module. The three-level driving circuit includes a first vertical tube circuit, a second vertical tube circuit, and a third vertical tube circuit; The bus capacitor includes an upper bridge capacitor and a lower bridge capacitor. The upper bridge capacitor, together with the upper bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, forms an upper bridge circuit. The lower bridge capacitor, together with the lower bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, forms a lower bridge circuit. The upper bridge capacitor and the lower bridge capacitor are interconnected and connected in parallel with the battery, such that a midpoint current is formed at the midpoint potential between the upper bridge capacitor and the lower bridge capacitor. The midpoint current amplification module is located between the midpoint potential and the three-phase circuit of the motor to increase the midpoint current, thereby increasing the current flowing through the battery to heat the battery. The midpoint current amplification module includes a first horizontal tube amplification phase, a second horizontal tube amplification phase, and a third horizontal tube amplification phase, wherein... The first horizontal tube amplification phase includes a first diode, a second diode, a first switch, and a second switch. The first switch is connected in parallel with the first diode, and the negative terminal of the first diode is connected to the midpoint potential. One end of the second switch is connected to the first switch, and the other end is connected to the first vertical tube circuit. The positive terminal of the second diode is connected to the positive terminal of the first diode, and the negative terminal is connected to the first vertical tube circuit. The second horizontal tube amplification phase includes a third diode, a fourth diode, a third switch, and a fourth switch. The third switch is connected in parallel with the third diode, and the negative terminal of the third diode is connected to the midpoint potential. One end of the fourth switch is connected to the third switch, and the other end is connected to the second vertical tube circuit. The positive terminal of the fourth diode is connected to the positive terminal of the third diode, and the negative terminal is connected to the second vertical tube circuit. The third horizontal tube amplification phase includes a fifth diode, a sixth diode, a fifth switch, and a sixth switch. The fifth switch is connected in parallel with the fifth diode, and the negative terminal of the fifth diode is connected to the midpoint potential. One end of the sixth switch is connected to the fifth switch, and the other end is connected to the third vertical tube circuit. The positive terminal of the sixth diode is connected to the positive terminal of the fifth diode, and the negative terminal is connected to the third vertical tube circuit.

2. The battery heating system as described in claim 1, characterized in that, The battery includes an upper bridge battery and a lower bridge battery. The negative terminal of the upper bridge battery is connected to the midpoint potential, and the positive terminal is connected to the upper bridge circuit. The positive terminal of the lower bridge battery is connected to the midpoint potential, and the negative terminal is connected to the lower bridge circuit.

3. The battery heating system as described in claim 2, characterized in that, The upper bridge capacitor and the lower bridge capacitor are in common mode. When the upper bridge capacitor and the lower bridge capacitor are injected in common mode, one of the first vertical transistor circuit, the second vertical transistor circuit and the third vertical transistor circuit switches to the on / off state, so that the average output voltage of the bus capacitor remains unchanged while the midpoint current is increased.

4. The battery heating system as described in claim 1, characterized in that, It also includes a motor and a motor controller, wherein the motor is connected to the motor three-phase circuit; The motor controller has a pre-stored constant torque curve calibration table. The motor controller selects the d-axis current Id and q-axis current Iq at the operating point with the largest midpoint current in the constant torque curve calibration table.

5. The battery heating system as described in claim 2, characterized in that, A first wire inductor is also connected between the upper bridge battery and the upper bridge capacitor. A second wire inductor is also connected between the lower bridge battery and the lower bridge capacitor, and one end of the second wire inductor is connected to the midpoint potential; The upper bridge capacitor and the first wire inductance form a first parallel resonant circuit, and the first current of the first parallel resonant circuit heats the upper bridge battery. The lower bridge capacitor and the second conductor inductance form a second parallel resonant circuit, and the second current of the second parallel resonant circuit heats the lower bridge battery.

6. A method for heating the battery of an electric vehicle, characterized in that, Includes the following steps: A battery heating system is configured, which includes a battery, a bus capacitor, a three-level drive circuit, and a midpoint current amplification module. The three-level driving circuit includes a first vertical tube circuit, a second vertical tube circuit, and a third vertical tube circuit; The bus capacitor includes an upper bridge capacitor and a lower bridge capacitor. The upper bridge capacitor, together with the upper bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, forms an upper bridge circuit. The lower bridge capacitor, together with the lower bridge portions of the first vertical tube circuit, the second vertical tube circuit, and the third vertical tube circuit, forms a lower bridge circuit. The upper bridge capacitor and the lower bridge capacitor are interconnected and connected in parallel with the battery, such that a midpoint current is formed at the midpoint potential between the upper bridge capacitor and the lower bridge capacitor. The midpoint current amplification module is located between the midpoint potential and the three-phase circuit of the motor to increase the midpoint current, thereby increasing the current flowing through the battery to heat the battery. The midpoint current amplification module is configured to include a first horizontal tube amplification phase, a second horizontal tube amplification phase, and a third horizontal tube amplification phase, wherein... The configuration of the first horizontal tube amplification phase includes a first diode, a second diode, a first switch, and a second switch. The first switch is connected in parallel with the first diode, and the negative terminal of the first diode is connected to the midpoint potential. One end of the second switch is connected to the first switch, and the other end is connected to the first vertical tube circuit. The positive terminal of the second diode is connected to the positive terminal of the first diode, and the negative terminal is connected to the first vertical tube circuit. The second horizontal tube amplification phase is configured with a third diode, a fourth diode, a third switch, and a fourth switch. The third switch is connected in parallel with the third diode, and the negative terminal of the third diode is connected to the midpoint potential. One end of the fourth switch is connected to the third switch, and the other end is connected to the second vertical tube circuit. The positive terminal of the fourth diode is connected to the positive terminal of the third diode, and the negative terminal is connected to the second vertical tube circuit. The third horizontal tube amplification phase is configured to include a fifth diode, a sixth diode, a fifth switch, and a sixth switch. The fifth switch is connected in parallel with the fifth diode, and the negative terminal of the fifth diode is connected to the midpoint potential. One end of the sixth switch is connected to the fifth switch, and the other end is connected to the third vertical tube circuit. The positive terminal of the sixth diode is connected to the positive terminal of the fifth diode, and the negative terminal is connected to the third vertical tube circuit.

7. The battery heating method as described in claim 6, characterized in that, The steps for configuring a battery heating system include: The battery configuration includes an upper bridge battery and a lower bridge battery. The negative terminal of the upper bridge battery is connected to the midpoint potential, and the positive terminal is connected to the upper bridge circuit. The positive terminal of the lower bridge battery is connected to the midpoint potential, and the negative terminal is connected to the lower bridge circuit.

8. The battery heating method as described in claim 7, characterized in that, The steps for configuring a battery heating system include: The upper bridge capacitor and the lower bridge capacitor are configured to be in common mode. When the upper bridge capacitor and the lower bridge capacitor are injected in common mode, one of the first vertical transistor circuit, the second vertical transistor circuit and the third vertical transistor circuit switches to the on / off state, so that the average output voltage of the bus capacitor remains unchanged while the midpoint current is increased.

9. The battery heating method as described in claim 6, characterized in that, The steps for configuring a battery heating system also include: Configure a motor and a motor controller, wherein the motor is connected to the motor three-phase circuit; The motor controller is configured to have a pre-stored constant torque curve calibration table. The motor controller selects the d-axis current Id and q-axis current Iq at the operating point with the largest midpoint current in the constant torque curve calibration table.

10. The battery heating method as described in claim 7, characterized in that, The steps for configuring a battery heating system include: A first wire inductor is also connected between the upper bridge battery and the upper bridge capacitor; A second wire inductor is also connected between the lower bridge battery and the lower bridge capacitor, and one end of the second wire inductor is connected to the midpoint potential; The upper bridge capacitor and the first wire inductance are configured to form a first parallel resonant circuit, and the first current of the first parallel resonant circuit heats the upper bridge battery. The lower bridge capacitor and the second conductor inductor are configured to form a second parallel resonant circuit, and the second current of the second parallel resonant circuit heats the lower bridge battery.

Images