Power battery heating circuit and electric vehicle

Abstract

Disclosed is an electric vehicle having a power battery. The power battery includes a heating circuit and a first cell group and a second cell group connected in series, and the heating circuit of the power battery includes an inverter, an AC motor, and a first controller, the neutral point of the AC motor is connected to a first connection point, which is a connection point between the first cell group and the second cell group, and the first controller inputs a drive signal to the inverter to control the inverter to alternately establish electrical conduction between the first cell group and the AC motor and between the second cell group and the AC motor, so that the first cell group and the second cell group alternately charge each other.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on January 29, 2022, bearing application number 202210112694.2 and title "Heating Circuit for Power Battery and Electric Vehicle," the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to vehicle technology, and more particularly, to a heating circuit for a power battery and an electric vehicle. [Background technology]

[0003] With the development of vehicle technology, vehicles using power batteries as a power source are becoming more and more popular. The characteristics of power batteries are greatly affected by the environmental temperature, especially in low temperature environments, the energy and power characteristics of lithium-ion power batteries are seriously attenuated, so it is necessary to heat the battery at low temperatures. In the heating method that uses excitation current to realize self-heating of the cell, how to improve the heating performance is an important issue. Summary of the Invention

[0004] The embodiments of the present disclosure provide a heating circuit for a power battery that can improve heating performance.

[0005] According to a first aspect of the present disclosure, there is provided a heating circuit for a power battery, the power battery including a first cell group and a second cell group connected in series, the heating circuit for the power battery including an inverter, an AC motor, and a first controller, a neutral point of the AC motor is connected to a first connection point, the first connection point is a connection point between the first cell group and the second cell group, and the first controller inputs a drive signal to the inverter to control the inverter to alternately establish conduction between the first cell group and the AC motor and between the second cell group and the AC motor, so that the first cell group and the second cell group alternately charge each other.

[0006] In one embodiment, a switch is connected in series between a neutral point of the AC motor and the first connection point, and the heating circuit further includes a second controller, which controls the on / off state of the switch.

[0007] In one embodiment, a protection circuit is connected in series between a neutral point of the AC motor and the first connection point.

[0008] In one embodiment, the battery capacity of the first cell group and the battery capacity of the second cell group are the same.

[0009] In one embodiment, the first controller further adjusts the drive signal so that an average value of the current intensity of the first cell group is 1C to 5C and an average value of the current intensity of the second cell group is 1C to 5C during a first period, the first period being 60 seconds.

[0010] In one embodiment, the first controller further adjusts the drive signal such that within one second, the real-time current of the first cell group switches from a positive cycle to a negative cycle 1 to 1000 times and the real-time current of the second cell group switches from a positive cycle to a negative cycle 1 to 1000 times.

[0011] In one embodiment, the first controller further adjusts the drive signal such that within one second, the real-time current of the first cell group switches from a positive cycle to a negative cycle 1 to 100 times and the real-time current of the second cell group switches from a positive cycle to a negative cycle 1 to 100 times.

[0012] In one embodiment, the first controller further adjusts the drive signal such that within one second, the real-time current of the first cell group switches from a positive cycle to a negative cycle 10 times and the real-time current of the second cell group switches from a positive cycle to a negative cycle 10 times.

[0013] In one embodiment, the first controller further adjusts the drive signal such that a magnitude of a real-time current in the first group of cells is the same as a magnitude of a real-time current in the second group of cells.

[0014] In one embodiment, the first controller further adjusts the drive signal so that a target ratio is greater than or equal to 0.3, the target ratio being a ratio between a first value and a second value, the first value being the smaller of the absolute value of the real-time current of the first cell group and the absolute value of the real-time current of the second cell group, and the second value being the larger of the absolute value of the real-time current of the first cell group and the absolute value of the real-time current of the second cell group.

[0015] In one embodiment, when adjusting the drive signal, the first controller adjusts a duty cycle and / or a frequency of the drive signal.

[0016] An electric vehicle according to a second aspect of the present disclosure includes a power battery and a heating circuit according to any one of the first aspects.

[0017] In the power battery heating circuit and electric vehicle of the embodiments of the present disclosure, a circuit is added based on the existing circuit topology structure of the electric vehicle, the circuit being from the neutral point of the AC motor to the connection point between the first cell group and the second cell group, and this heating circuit can be used to improve the overall heating performance.

[0018] The features and advantages of the embodiments of the present specification will become apparent from the detailed description of the exemplary embodiments of the present specification given below with reference to the drawings. [Brief description of the drawings]

[0019] The drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the embodiments of the present invention.

[0020] [Figure 1] FIG. 2 is a block diagram of a heating circuit for a power battery according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a specific circuit diagram of a heating circuit of a power battery according to an embodiment of the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram showing the effect of the magnitude of the excitation current on the capacity of a power battery. [Figure 4] FIG. 1 is a schematic diagram showing the effect of the frequency of the excitation current on the heating rate. [Diagram 5] FIG. 1 is a schematic diagram showing the battery impedance spectrum analysis of a power battery under different SOC conditions and under the action of excitation currents of different frequencies. [Figure 6] FIG. 1 is a schematic diagram showing the battery impedance spectrum analysis of a power battery under different SOC conditions and under the action of excitation currents of different frequencies. [Figure 7] FIG. 1 is a schematic diagram showing the battery impedance spectrum analysis of a power battery under different SOC conditions and under the action of excitation currents of different frequencies. [Figure 8] FIG. 1 is a schematic diagram showing the battery impedance spectrum analysis of a power battery under different SOC conditions and under the action of excitation currents of different frequencies. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the drawings.

[0022] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the embodiments herein, their application, or uses.

[0023] It should be noted that similar symbols and letters represent similar things in the following drawings, so that once something is defined in one drawing, it does not need to be further discussed in the subsequent drawings.

[0024] In an electric vehicle, an inverter is connected between a power battery and an AC motor, and one of the main roles of the inverter is to convert the DC current output from the power battery into AC current to drive the AC motor to rotate, and further drive the wheel side to rotate. The heating means of the power battery of the embodiment of the present disclosure utilizes a circuit topology structure between the power battery, the inverter, and the AC motor. Hereinafter, the heating circuit of the power battery according to the embodiment of the present disclosure will be described with reference to FIG. 1 and FIG. 2.

[0025] The power battery includes a first cell group 1 and a second cell group 2 connected in series, and the heating circuit includes an inverter 3, an AC motor 4 and a first controller 6.

[0026] The AC motor 4 is star-connected, and three terminals of the three-phase coil (coil A, coil B, coil C) are commonly connected to form a common terminal, which is a neutral point P2. The neutral point P2 of the AC motor 4 is connected to a first connection point P1, which is a connection point between the first cell group 1 and the second cell group 2. In one example, the battery pack includes the first cell group and the second cell group, and provides a positive main port, a negative main port, and a third port drawn from the first connection point P1 to the outside, and connects the first connection point P1 and the neutral point P2 of the AC motor 4 through the third port. In another example, the first cell group 1 and the second cell group 2 are different battery packs.

[0027] The first controller inputs a drive signal to the inverter 3 to control the inverter 3 to alternately establish electrical continuity between the first cell group 1 and the AC motor 4, and between the second cell group 2 and the AC motor 4, thereby causing the first cell group and the second cell group to alternately charge each other.

[0028] In one example, as shown in FIG. 1 and FIG. 2, the inverter 3 includes an IGBT transistor T1, an IGBT transistor T2, an IGBT transistor T3, an IGBT transistor T4, an IGBT transistor T5, and an IGBT transistor T6, and the IGBT transistors T1 to T6 form three bridge arms. An IGBT (Insulated Gate Bipolar Transistor) is a composite voltage-driven power semiconductor device composed of a BJT transistor (Bipolar Junction Transistor) and a MOS transistor (Meial-Oxide-Semiconductor, Insulated Gate Field Effect Transistor), and combines the advantages of both the high input impedance of a MOSFET field effect transistor and the low on-voltage drop of a GTR (Giant Transistor, high power transistor). As shown in FIG. 2, in the inverter 3, a diode is connected in reverse parallel to each IGBT transistor, and the diode can play a role of circuit protection. In another embodiment, the IGBT transistors T1 to T6 may be replaced with MOS transistors.

[0029] In the embodiment of the present disclosure, the IGBT transistor can output current signals of different frequencies and amplitudes in real time according to the frequency and period of the driving signal. In one example, the driving signal output from the first controller is a PWM (Pulse Width Modulation Wave) driving signal, that is, a pulse wave signal with a variable duty ratio.

[0030] In an embodiment of the present disclosure, as shown in FIG. 2, the first controller outputs six drive signals Q1 to Q6, where drive signal Q1 is applied to IGBT transistor T1, drive signal Q2 is applied to IGBT transistor T2, drive signal Q3 is applied to IGBT transistor T3, drive signal Q4 is applied to IGBT transistor T4, drive signal Q5 is applied to IGBT transistor T5, and drive signal Q6 is applied to IGBT transistor T6. By applying drive signals Q1 to Q6 to the IGBT transistors T1 to T6, the first controller alternately energizes the circuit between the first cell group 1 and the AC motor 4 and the circuit between the second cell group 2 and the AC motor 4, thereby causing the first cell group 1 and the second cell group 2 to alternately charge each other. In one example, the first cell group 1 discharges, the inverter 3 converts the DC current output from the first cell group 1 into AC current and inputs it to the AC motor 4, and the AC motor 4 stores the electrical energy in its coils to charge the second cell group 2. After that, the second cell group 2 discharges, the inverter 3 converts the DC current output from the second cell group 2 into AC current and inputs it to the AC motor 4, and the AC motor 4 stores the electrical energy in its coils to charge the first cell group 1. Repeating in this manner, the first cell group and the second cell group alternately charge each other.

[0031] In one example, a switch 5 is connected in series between the neutral point P2 of the AC motor and the first connection point P1. The heating circuit further includes a second controller 7. The second controller controls the on / off state of the switch 5 to turn on the switch 5 when the power battery needs to be heated and turn off the switch 5 when the power battery does not need to be heated, thereby ensuring the safety of the vehicle and the power battery. For example, the second controller controls the switch 5 to turn off when the electric vehicle is running, thereby ensuring the safety during the running process of the vehicle.

[0032] In one example, in order to improve safety during the heating process of the battery, a protection circuit 8, such as a fuse, is connected in series between the neutral point P2 of the AC motor and the first connection point P1.

[0033] In one example, the battery capacity of the first cell group is the same as the battery capacity of the second cell group, which is advantageous for simplifying the control logic algorithm and facilitating model selection of related devices of the heating circuit.

[0034] In the heating circuit of the power battery according to the embodiment of the present disclosure, a circuit is added based on the existing circuit topology structure of the electric vehicle, and the circuit is from the neutral point of the AC motor to the connection point between the first cell group and the second cell group, with only minor changes to the original circuit and simple means for easy implementation.

[0035] In the heating process of the power battery, the frequency and magnitude of the charge / discharge current, i.e., the excitation current, are limited by related components, and the heating circuit according to the embodiment of the present disclosure can reduce the limit of the excitation current and heat the battery with a large excitation current. For example, considering the limit on the excitation current by a single coil of the motor alone, assuming that the maximum allowable current value passing through a single coil of the motor is 100 units, the heating circuit according to the embodiment of the present disclosure can make three coils store and discharge energy simultaneously, so that the upper limit of the excitation current can be 300 units.

[0036] In the heating process of the power battery, the control of the excitation current is very important. Under the action of a large excitation current, the temperature rise rate of the power battery is fast. Figure 4 shows the capacity retention rate of lithium iron phosphate and ternary battery under self-heating conditions. The inventor has found through many research experiments that when the temperature is -20°C, the power battery is heated using an excitation current of 1C, and the capacity retention rate is 99.0%-99.94% after heating a certain number of times, that is, the battery capacity is 99.0%-99.94% of the original battery capacity after heating a certain number of times. 1C is the current intensity when the battery is fully discharged for 1 hour. The predetermined number is 200 times. When the power battery is heated using a charge / discharge current of 2C-5C, Figure 4 can be similarly referred to. That is, the adverse effect on the battery capacity also increases with the increase in excitation current.

[0037] The inventor has found through many research experiments that the frequency of the excitation current is too high, which affects the heating efficiency and slows down the temperature rise of the battery. This is caused by the inherent electrochemical characteristics of the battery, and the battery has a higher impedance with low-frequency current oscillation, so the temperature rise effect is higher. However, in the heating process in a low-temperature environment, low-frequency excitation may shorten the battery life and even cause lithium precipitation. As shown in Figure 3, the power battery is heated with an excitation current of 2C, an excitation current of 3C, and an excitation current of 4C, respectively, and the frequency of the excitation current is set to 1Hz to 1000Hz. It can be seen that the temperature rise rate is high in the low-frequency stage, especially in the range of 1Hz to 100Hz.

[0038] 5 to 8 are schematic diagrams showing the battery impedance spectrum analysis of a power battery under different SOC conditions and under the action of excitation currents of different frequencies. SOC (State of Charge) refers to the state of residual charge of a battery, and is generally expressed as a percentage, i.e., the percentage of the remaining battery capacity relative to the total capacity. The horizontal axis is the time of the excitation current cycle, in seconds, and its inverse is the frequency of the excitation current, and the frequency gradually decreases from left to right along the horizontal axis. The vertical axis is the time distribution of the impedance, in ohms / second. As can be seen from FIG. 5 to FIG. 8, when the SOC is different, a large peak appears in the time distribution of the impedance in the section where the excitation current cycle is 0.01 seconds to 0.1 seconds (frequency 10 Hz to 100 Hz). As can be seen from FIG. 5 to FIG. 8, when the SOC is different, when the excitation current cycle is longer than 1 second (frequency is less than 1 Hz), the risk of lithium precipitation is high.

[0039] In the embodiment of the present disclosure, the first controller obtains the battery state (temperature, power, voltage), the amplitude and frequency of the charging and discharging current, etc., monitored by the vehicle measurement system, and dynamically adjusts the frequency or current amplitude of the excitation current in real time according to a predetermined policy. The control method of the excitation current, i.e., the charging and discharging current, in this embodiment will be described below.

[0040] In the embodiment of the present disclosure, the real-time current of the first cell group 1 is I A and the real-time current of the second cell group 2 is I B I A The flow of I from the positive electrode of the first cell group 1 is called a positive cycle. A The flow of I to the positive electrode of the first cell group 1 is called a negative cycle, and I B The flow of I from the positive electrode of the second cell group 2 is called a positive cycle. B flowing into the positive electrode of the second cell group 2 is referred to as a negative cycle.

[0041] In policy 1, the first controller further adjusts the driving signal so that the average value of the current intensity of the first cell group is 1C-5C and the average value of the current intensity of the second cell group is 1C-5C in a first period, the first period being 60 seconds. That is, in the heating process of the power battery, the average value of the current intensity of the first cell group is 1C-5C and the average value of the current intensity of the second cell group is 1C-5C within a time of at least 60 seconds.

[0042] The average current strength of the cell group is

number

[0043] Here, "C" is the rate of the battery charge / discharge current, and 1C is the current strength when the battery is fully discharged for 1 hour. For the first group of cells, 1C=CA / 3600 seconds, where CA is the rated capacity of the first group of cells in ampere-hours. For the second group of cells, 1C=CB / 3600 seconds, where CB is the rated capacity of the second group of cells in ampere-hours. That is, 1*(CA / 3600s)≦I effA ≦5*(CA / 3600s) 1*(CB / 3600s)≦I effB≦5*(CB / 3600s) In the formula, I effA is the average value of the current intensity in the first cell group 1 during the first period, and I effB is the average value of the current intensity of the second cell group 2 in the first period.

[0044] In the embodiment of the present disclosure, by controlling the excitation current to be 1C to 5C, it is possible to ensure heating efficiency and minimize adverse effects on battery capacity, while preventing the cell from being overcharged or overdischarged at low temperatures, thereby ensuring the safety of the cell.

[0045] In policy 2, In one example, the first controller further adjusts the driving signal such that within 1 second, the real-time current of the first cell group switches from positive cycle to negative cycle 1-1000 times, and the real-time current of the second cell group switches from positive cycle to negative cycle 1-1000 times, that is, during the heating process of the power battery, within a time of at least 1 second, the real-time current of the cell group switches from positive cycle to negative cycle 1-1000 times.

[0046] In one example, the first controller further adjusts the driving signal so that the real-time current of the first cell group switches from positive cycle to negative cycle 5-1000 times within 1 second, and the real-time current of the second cell group switches from positive cycle to negative cycle 5-1000 times within 1 second, that is, in the heating process of the power battery, the real-time current of the cell group switches from positive cycle to negative cycle 5-1000 times within at least 1 second.

[0047] In one example, the first controller further adjusts the driving signal such that within 1 second, the real-time current of the first cell group switches from positive cycle to negative cycle 1-100 times, and the real-time current of the second cell group switches from positive cycle to negative cycle 1-100 times, that is, during the heating process of the power battery, within a time of at least 1 second, the real-time current of the cell group switches from positive cycle to negative cycle 1-100 times.

[0048] In one example, the first controller further adjusts the driving signal such that within 1 second, the real-time current of the first cell group switches from positive cycle to negative cycle 5-100 times, and the real-time current of the second cell group switches from positive cycle to negative cycle 5-100 times, that is, during the heating process of the power battery, within a time of at least 1 second, the real-time current of the cell group switches from positive cycle to negative cycle 5-100 times.

[0049] In one example, the first controller further adjusts the driving signal such that within 1 second, the real-time current of the first cell group switches from positive cycle to negative cycle 10 times, and the real-time current of the second cell group switches from positive cycle to negative cycle 10 times, i.e., during the heating process of the power battery, within a time of at least 1 second, the real-time current of the cell group switches from positive cycle to negative cycle 10 times.

[0050] Referring to the contents shown in FIG. 4 and FIG. 5 to FIG. 8, in consideration of the adverse effect on the battery life and the risk of lithium precipitation when the frequency of the excitation current is too low, in the embodiment of the present disclosure, the safe frequency range of the excitation current is set to 1 Hz or more, that is, the lower limit of the frequency of the excitation current is set to 1 Hz. In consideration of the heating efficiency, the upper limit of the frequency of the excitation current is set to 1000 Hz. In the embodiment of the present disclosure, the above-mentioned several ranges are preferable in the range of 1 Hz to 1000 Hz, and by setting the number of times that the real-time current of the cell group switches from a positive cycle to a negative cycle within a unit time in the above-mentioned method, it is possible to achieve both heating efficiency and reduce the impact of heating on the battery life and reduce the risk in the heating process.

[0051] In policy 3, the first controller further adjusts the driving signal so that the magnitude of the real-time current of the first cell group is the same as the magnitude of the real-time current of the second cell group. That is, during the heating process, at least for a certain period of time, |I A |=|I B | is the absolute value symbol.

[0052] If the magnitude of the real-time current of the first cell group is the same as the magnitude of the real-time current of the second cell group, it is advantageous for simplifying the control logic algorithm, and the model selection of related devices in the heating circuit is also facilitated, which can reduce costs.

[0053] Policy 4 states: The first controller further adjusts the drive signal so that the target ratio is greater than or equal to 0.3, the target ratio being a ratio between a first value and a second value, the first value being the smaller of the absolute value of the real-time current of the first cell group and the absolute value of the real-time current of the second cell group, and the second value being the larger of the absolute value of the real-time current of the first cell group and the absolute value of the real-time current of the second cell group.

[0054] As can be seen from policy 4, in the heating circuit according to the embodiment of the present disclosure, the magnitude of the real-time current of the first cell group and the magnitude of the real-time current of the second cell group may be different. By controlling the ratio between the smaller and larger of the two to be 0.3 or more, the difference between the magnitude of the real-time current of the first cell group and the magnitude of the real-time current of the second cell group will not be too large, thus making it possible to well realize the heating of the power battery and relatively easy to realize technically.

[0055] In the embodiments of the present disclosure, in order to achieve greater effectiveness, the above policies can be implemented in combination if they are not contradictory.

[0056] In an embodiment of the present disclosure, the first controller can adjust the duty ratio and / or frequency of the drive signal to realize the above control policy. For example, the first controller adjusts the duty ratio of the drive signal to adjust the magnitude of the excitation current. For example, the first controller adjusts the frequency of the drive signal to control the number of times the excitation current switches from a positive cycle to a negative cycle within a certain period of time.

[0057] In the embodiments of the present disclosure, the above policy can achieve both temperature rise efficiency and safety during the self-heating process, effectively heat the power battery, avoid excessive damage to the battery life, and ensure the safety of the battery.

[0058] A first controller of an embodiment of the present disclosure may include a processor, a memory, and a program or instructions stored in the memory and executable on the processor, which, when executed by the processor, realizes any of the heating control policies described in the above embodiments.

[0059] A vehicle according to an embodiment of the present disclosure includes a power battery and a power battery heating circuit according to any of the previous embodiments.

[0060] Each embodiment in this specification will be described step by step, and the same or similar parts of each embodiment may be referred to each other, and each embodiment will be described by focusing on the difference between the other embodiments, and the electric vehicle embodiment may be referred to the description of the method embodiment for the relevant part.

[0061] Certain embodiments of the present specification have been described above. Other embodiments are within the scope of the appended claims. In some cases, the acts or steps recited in the claims may be performed in an order different from that of the examples and still achieve desirable results. Also, the processes depicted in the figures do not necessarily require the particular order depicted, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or advantageous.

[0062] The embodiments herein may be systems, methods and / or computer program products. The computer program product may include a computer-readable storage medium having computer instructions that cause a processor to implement aspects of the embodiments herein.

[0063] A computer-readable storage medium may be a tangible device that can hold and store computer instructions used by a computer instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above. More specific examples (non-exhaustive list) of computer-readable storage media include portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory stick, floppy disk, mechanically encoded devices such as punch cards or protrusions in grooves on which computer instructions are stored, and any suitable combination of the above. A computer-readable storage medium as used herein is not to be interpreted as being a transitory signal itself, such as, for example, radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a wave guide or other transmission medium (e.g., light pulses passing through a fiber optic cable), or electrical signals transmitted through electrical wires.

[0064] The computer instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or can be downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface of each computing / processing device receives the computer instructions from the network and forwards the computer instructions for storage in the computer-readable storage medium of each computing / processing device.

[0065] The flowcharts and block diagrams in the drawings illustrate possible architectures, functions, and operations of systems, methods, and computer program products according to several embodiments of the present specification. In this regard, each block in the flowcharts or block diagrams may represent a module, a program segment, or a portion of computer instructions, which includes one or more executable computer instructions for implementing a specified logical function. In some alternative implementations, the functions depicted in the blocks may occur in a different order from that depicted in the drawings. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or may be executed in reverse order depending on the related functions. It should be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be realized by a dedicated system based on hardware that executes the specified functions or operations, or may be realized by a combination of dedicated hardware and computer instructions. It is well known to those skilled in the art that implementation by hardware, implementation by software, and implementation by a combination of software and hardware are all equivalent.

[0066] Although each embodiment of the present specification has been described above, the above description is illustrative and not exhaustive, and is not limited to each embodiment disclosed. Many modifications and changes will be obvious to those skilled in the art without departing from the scope of each embodiment described. The terms used in this specification are selected to best interpret the principles, practical applications, or improvements in technology in the market of each embodiment, or to enable those skilled in the art to understand each embodiment disclosed in this specification.

Claims

1. A heating circuit for a power battery, the power battery including a first cell group (1) and a second cell group (2) connected in series, the heating circuit including an inverter (3), an AC motor (4) and a first controller (5); A neutral point (P2) of the AC motor (5) is connected to a first connection point (P1), and the first connection point (P1) is a connection point between the first cell group (1) and the second cell group (2), The first controller (5) controls the inverter (3) by inputting a drive signal to alternately establish electrical continuity between the first cell group (1) and the AC motor (4) and between the second cell group (2) and the AC motor (4), thereby causing the first cell group (1) and the second cell group (2) to alternately charge each other.

2. 2. The heating circuit according to claim 1, wherein a switch (5) is connected in series between a neutral point (P2) of the AC motor (4) and the first connection point (P1), and the heating circuit further includes a second controller, the second controller controlling the on / off state of the switch.

3. 3. The heating circuit according to claim 1, further comprising a protection circuit (8) connected in series between the neutral point (P2) of the AC motor (4) and the first connection point (P1).

4. The heating circuit according to any one of claims 1 to 3, characterized in that the battery capacity of the first cell group (1) and the battery capacity of the second cell group (2) are the same.

5. 5. The heating circuit according to claim 1, wherein the first controller (6) further adjusts the drive signal such that, during a first period, an average value of the current intensity of the first cell group (1) is between 1 C and 5 C and an average value of the current intensity of the second cell group (2) is between 1 C and 5 C, and the first period is 60 seconds.

6. 6. The heating circuit according to claim 1, wherein the first controller (6) further adjusts the drive signal such that within one second, the real-time current of the first cell group (1) switches from a positive cycle to a negative cycle 1 to 1000 times and the real-time current of the second cell group (2) switches from a positive cycle to a negative cycle 1 to 1000 times.

7. 6. The heating circuit according to claim 1, wherein the first controller (6) further adjusts the drive signal such that within one second, the real-time current of the first cell group (1) switches from a positive cycle to a negative cycle 1 to 100 times and the real-time current of the second cell group (2) switches from a positive cycle to a negative cycle 1 to 100 times.

8. 6. The heating circuit according to claim 1, wherein the first controller (6) further adjusts the drive signal such that within one second, the real-time current of the first cell group (1) switches from a positive cycle to a negative cycle 10 times and the real-time current of the second cell group (2) switches from a positive cycle to a negative cycle 10 times.

9. The heating circuit according to any one of claims 1 to 5, characterized in that the first controller (6) further adjusts the drive signal so that the magnitude of the real-time current of the first cell group (1) is the same as the magnitude of the real-time current of the second cell group (2).

10. The heating circuit of any one of claims 1 to 5, characterized in that the first controller (6) further adjusts the drive signal so that a target ratio is greater than or equal to 0.3, the target ratio being a ratio between a first value and a second value, the first value being the smaller of an absolute value of a real-time current of the first cell group (1) and an absolute value of a real-time current of the second cell group (2), and the second value being the larger of an absolute value of a real-time current of the first cell group (1) and an absolute value of a real-time current of the second cell group (2).

11. The heating circuit according to any one of claims 5 to 10, characterized in that, when adjusting the drive signal, the first controller (6) adjusts the duty ratio and / or the frequency of the drive signal.

12. An electric vehicle including a power battery and a heating circuit, The power battery includes a first cell group (1) and a second cell group (2) connected in series, and the heating circuit includes an inverter (3), an AC motor (4) and a first controller (5); A neutral point (P2) of the AC motor (5) is connected to a first connection point (P1), and the first connection point (P1) is a connection point between the first cell group (1) and the second cell group (2), The first controller (5) controls the inverter (3) by inputting a drive signal to alternately establish electrical continuity between the first cell group (1) and the AC motor (4) and between the second cell group (2) and the AC motor (4), thereby causing the first cell group (1) and the second cell group (2) to alternately charge each other.

13. 13. The electric vehicle according to claim 12, wherein a switch (5) is connected in series between a neutral point (P2) of the AC motor (4) and the first connection point (P1), and the heating circuit further includes a second controller, the second controller controlling the on / off state of the switch.

14. 14. The electric vehicle according to claim 12 or 13, characterized in that a protection circuit (8) is connected in series between the neutral point (P2) of the AC motor (4) and the first connection point (P1).

15. The electric vehicle according to any one of claims 12 to 14, wherein the first controller (6) further adjusts the drive signal such that, during a first period, an average value of a current intensity of the first cell group (1) is 1C to 5C and an average value of a current intensity of the second cell group (2) is 1C to 5C, and the first period is 60 seconds.

16. The electric vehicle according to any one of claims 12 to 14, characterized in that the first controller (6) further adjusts the drive signal such that within one second, the real-time current of the first cell group (1) switches from a positive cycle to a negative cycle 1 to 1000 times, and the real-time current of the second cell group (2) switches from a positive cycle to a negative cycle 1 to 1000 times.

17. The electric vehicle according to any one of claims 12 to 14, characterized in that the first controller (6) further adjusts the drive signal such that within one second, the real-time current of the first cell group (1) switches from a positive cycle to a negative cycle 1 to 100 times, and the real-time current of the second cell group (2) switches from a positive cycle to a negative cycle 1 to 100 times.

18. The electric vehicle according to any one of claims 12 to 14, characterized in that the first controller (6) further adjusts the drive signal such that within one second, the real-time current of the first cell group (1) switches from a positive cycle to a negative cycle 10 times and the real-time current of the second cell group (2) switches from a positive cycle to a negative cycle 10 times.

19. The electric vehicle of any one of claims 12 to 14, characterized in that the first controller (6) further adjusts the drive signal so that the magnitude of the real-time current of the first cell group (1) is the same as the magnitude of the real-time current of the second cell group (2).

20. The electric vehicle of any one of claims 12 to 14, wherein the first controller (6) further adjusts the drive signal so that a target ratio is 0.3 or greater, the target ratio being a ratio between a first value and a second value, the first value being the smaller of an absolute value of a real-time current of the first cell group (1) and an absolute value of a real-time current of the second cell group (2), and the second value being the larger of an absolute value of a real-time current of the first cell group (1) and an absolute value of a real-time current of the second cell group (2).

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