Vehicle, energy conversion device and control method thereof

Abstract

The technical solution of the present application provides a vehicle, an energy conversion device and a control method thereof, wherein the energy conversion device includes a bridge arm converter, a motor and an energy storage element, wherein the motor, the energy storage element and the battery are connected to form a battery heating circuit, and the control method includes: when a battery heating instruction is obtained, the bridge arm converter is controlled with the initial charge and discharge frequency as the target charge and discharge frequency of the battery heating circuit, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated; the temperature parameters of the motor are obtained, and the target charge and discharge frequency of the battery heating circuit is adjusted according to the temperature parameters of the motor; the bridge arm converter is controlled according to the target charge and discharge frequency to adjust the current flowing through the battery heating circuit to adjust the iron loss of the motor. The present application adjusts the bridge arm converter according to the change of the temperature parameters of the motor to achieve the control of the iron loss of the motor, thereby avoiding the phenomenon that the motor heats up lightly and smokes in severe cases as the heating time increases during the battery self-heating process.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and in particular to a vehicle, an energy conversion device and a control method thereof. Background Art

[0002] With the widespread use of new energy, batteries can be used as power sources in various fields. The performance of batteries will be affected by the different environments in which they are used as power sources. For example, the performance of batteries in low temperature environments will be greatly reduced compared to normal temperatures. For example, at zero temperature, the discharge capacity of the battery will decrease as the temperature decreases. Under -30°C conditions, the discharge capacity of the battery is basically 0, making the battery unusable. In order to use the battery in a low temperature environment, the battery needs to be preheated before use.

[0003] like Figure 1 As shown, the prior art includes a bridge arm converter 101, a motor 102, and a battery 103. When the battery 103 is in the discharging process, the transistor VT1 and the transistor VT6 in the bridge arm converter 101 are triggered to be turned on at the same time, and the current flows out from the positive electrode of the battery 103, passes through the transistor VT1 and the transistor VT6, and the two stator inductors of the motor 102, and returns to the negative electrode of the battery 103. The current rises, and the energy is stored in the two stator inductors; when the battery 103 is in the charging process, as shown in FIG. Figure 2 As shown, transistor VT1 and transistor VT6 are disconnected at the same time, and the current returns to battery 102 from the two stator inductors of motor 102 and bridge arm converter 101 through two discharge diodes VD4 and VD3, and the current decreases. Repeating the above two processes, the battery is in a rapid alternating state of charging and discharging. Due to the existence of the internal resistance of the battery, a large amount of internal heat is generated, and the temperature rises rapidly. However, the prior art has the following problems: in the process of controlling the motor, since the charging and discharging frequency of the battery is fixed, as the battery heating time increases, the motor will generate heat or smoke, which will cause great damage to the motor and seriously affect the service life of the motor. At the same time, the noise generated by the motor is also very loud, which seriously affects the driver's driving experience. Summary of the invention

[0004] The purpose of the present application is to provide a vehicle, an energy conversion device and a control method thereof, which can adjust the iron loss of the motor by adjusting the bridge arm converter according to the temperature parameters of the motor, thereby avoiding the problems of motor heating, smoking and loud noise during battery heating.

[0005] The present application is implemented in this way. In a first aspect, the present application provides a control method for an energy conversion device, characterized in that the energy conversion device comprises:

[0006] A bridge arm converter, a motor and an energy storage element, wherein the bridge arm converter, the motor and the energy storage element are connected to a battery to form a battery heating circuit;

[0007] The control method comprises:

[0008] When a battery heating instruction is obtained, the bridge arm converter is controlled using the initial charge and discharge frequency as the target charge and discharge frequency of the battery heating circuit, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated;

[0009] acquiring a temperature parameter of the motor, and adjusting a target charge and discharge frequency of the battery heating circuit according to the temperature parameter of the motor;

[0010] The bridge arm converter is controlled according to the target charge and discharge frequency to adjust the current flowing through the battery heating circuit to adjust the iron loss of the motor.

[0011] A second aspect of the present application provides an energy conversion device, the energy conversion device comprising:

[0012] A bridge arm converter, a motor and an energy storage element, wherein the bridge arm converter, the motor and the energy storage element are connected to a battery to form a battery heating circuit;

[0013] The energy conversion device further comprises a control module, wherein the control module is used for:

[0014] When a battery heating instruction is obtained, the bridge arm converter is controlled using the initial charge and discharge frequency as the target charge and discharge frequency of the battery heating circuit, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated;

[0015] acquiring a temperature parameter of the motor, and adjusting a target charge and discharge frequency of the battery heating circuit according to the temperature parameter of the motor;

[0016] The bridge arm converter is controlled according to the target charge and discharge frequency to adjust the current flowing through the battery heating circuit to adjust the iron loss of the motor.

[0017] A third aspect of the present application provides a vehicle, comprising the energy conversion device described in the second aspect.

[0018] The technical solution of the present application provides a vehicle, an energy conversion device and a control method thereof, wherein the energy conversion device includes a bridge arm converter, a motor and an energy storage element, wherein the motor, the energy storage element and the battery are connected to form a battery heating circuit, and the control method includes: when a battery heating instruction is obtained, the bridge arm converter is controlled with the initial charge and discharge frequency as the target charge and discharge frequency of the battery heating circuit, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated; the temperature parameters of the motor are obtained, and the target charge and discharge frequency of the battery heating circuit is adjusted according to the temperature parameters of the motor; the bridge arm converter is controlled according to the target charge and discharge frequency to adjust the current flowing through the battery heating circuit to adjust the iron loss of the motor. The present application adjusts the bridge arm converter according to the change of the temperature parameters of the motor to achieve the control of the iron loss of the motor, thereby avoiding the phenomenon that the motor heats up lightly and smokes in severe cases as the heating time increases during the battery self-heating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 It is a current flow diagram of a motor control circuit provided by the prior art;

[0021] Figure 2 is another current flow diagram of a motor control circuit provided by the prior art;

[0022] Figure 3 is a circuit diagram of an energy conversion device provided in Example 1 of the present application;

[0023] Figure 4 is another circuit diagram of an energy conversion device provided in Example 1 of the present application;

[0024] Figure 5 is another circuit diagram of an energy conversion device provided in Example 1 of the present application;

[0025] Figure 6 is a flow chart of a control method for an energy conversion device provided in Example 1 of the present application;

[0026] Figure 7 This is a specific flow chart of step S10 of a control method for an energy conversion device provided in Example 1 of the present application;

[0027] Figure 8 is a specific flow chart of step S20 in a control method for an energy conversion device provided in Example 1 of the present application;

[0028] Fig. 9 is a specific flow chart of step S30 in a control method of an energy conversion device provided in Example 1 of the present application;

[0029] Fig.10 is another circuit diagram of an energy conversion device provided in Example 1 of the present application;

[0030] Fig.11 is a current flow diagram of an energy conversion device provided in Example 1 of the present application;

[0031] Fig.12 is another current flow diagram of an energy conversion device provided in Example 1 of the present application;

[0032] Fig.13 is another current flow diagram of an energy conversion device provided in Example 1 of the present application;

[0033] Fig.14 is another current flow diagram of an energy conversion device provided in Example 2 of the present application;

[0034] Fig.15 This is another current flow diagram of an energy conversion device provided in Example 2 of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] In order to illustrate the technical solution of the present application, a specific embodiment is provided below for illustration.

[0037] Embodiment 1 of the present application provides an energy conversion device, the energy conversion device comprising:

[0038] The bridge arm converter, the motor and the energy storage element are connected with the battery to form a battery heating circuit.

[0039] As a first implementation method of the connection relationship between the bridge arm converter, the motor and the energy storage element, Figure 3 As shown, the energy conversion device includes:

[0040] A bridge arm converter 101, wherein the first ends of the bridge arms of the bridge arm converter 101 are connected together to form a first bus terminal, and the second ends of the bridge arms of the bridge arm converter 101 are connected together to form a second bus terminal;

[0041] An energy storage element C1, wherein a first end of the energy storage element C1 is connected to a first bus terminal, and a second end of the energy storage element C1 is connected to a second bus terminal;

[0042] The motor 102, the first end of the motor 102 is respectively connected to the midpoint of each phase bridge arm of the bridge arm converter 101, the second end of the motor 102 is commonly connected to the positive electrode of the battery 103, and the negative electrode of the battery 103 is connected to the first bus terminal;

[0043] Among them, the bridge arm converter 101 includes M bridge arms, the first end of each bridge arm in the M bridge arms is connected together to form a first bus terminal of the bridge arm converter 101, the second end of each bridge arm in the M bridge arms is connected together to form a second bus terminal of the bridge arm converter 101, each bridge arm includes two power switch units connected in series, the power switch unit can be a transistor, IGBT, MOS tube or other device types, the midpoint of each bridge arm is formed between the two power switch units, the motor includes M-phase windings, the first end of each phase winding in the M-phase windings is connected one-to-one with the midpoint of each bridge arm in a group of M bridge arms, the second end of each phase winding in the M-phase windings is connected together to form a neutral point, and the neutral point is connected to the positive pole of the battery 103.

[0044] When M=3, the bridge arm converter 101 is a three-phase inverter, which includes three bridge arms, the first end of each bridge arm in the three bridge arms is connected in common to form a first bus terminal of the bridge arm converter 101, and the second end of each bridge arm in a group of three bridge arms is connected in common to form a second bus terminal of the bridge arm converter 101; the three-phase inverter includes a first power switch unit, a second power switch unit, a third power switch unit, a fourth power switch unit, a fifth power switch and a sixth power switch, the first power switch unit and the fourth power switch unit form a first bridge arm, the second power switch unit and the fifth switch unit form a second bridge arm, the third power switch unit and the sixth switch unit form a third bridge arm, one end of the first power switch unit, the third power switch unit and the fifth power switch unit are connected in common to form a first bus terminal of the three-phase inverter, and one end of the second power switch unit, the fourth power switch unit and the sixth power switch unit are connected in common to form a second bus terminal of the three-phase inverter.

[0045] Among them, the motor 102 includes a three-phase winding, the first end of each phase winding in the three-phase winding is connected one-to-one with the midpoint of each bridge arm in the three bridge arms, the second end of each phase winding in the three-phase winding is connected together to form a neutral point, the first end of the first phase winding of the motor 102 is connected to the midpoint of the first bridge arm, the first end of the second phase winding of the motor 102 is connected to the midpoint of the second bridge arm, and the first end of the third phase winding of the motor 102 is connected to the midpoint of the third bridge arm.

[0046] Among them, the first power switch unit in the three-phase inverter includes a first upper bridge arm VT1 and a first upper bridge diode VD1, the second power switch unit includes a second lower bridge arm VT2 and a second lower bridge diode VD2, the third power switch unit includes a third upper bridge arm VT3 and a third upper bridge diode VD3, the fourth power switch unit includes a fourth lower bridge arm VT4 and a fourth lower bridge diode VD4, the fifth power switch unit includes a fifth upper bridge arm VT5 and a fifth upper bridge diode VD5, the sixth power switch unit includes a sixth lower bridge arm VT6 and a sixth lower bridge diode VD6, the motor is a three-phase four-wire system, and can be a permanent magnet synchronous motor or an asynchronous motor, and the three-phase windings are connected at one point and connected to the positive pole of the battery 103.

[0047] In another embodiment, if Figure 4 As shown, the energy conversion device further includes a first switch module 104 and a second switch module 105. The first end of the first switch module 104 is connected to the first end of the energy storage element C1, and the second end of the first switch module 104 is connected to the positive electrode of the battery 103; the second switch module 105 is connected between the neutral point of the motor 102 and the positive electrode or negative electrode of the battery 103.

[0048] Among them, the first switch module 104 is used to realize the conduction or disconnection between the battery 103 and the energy storage element C1 according to the control signal, so that the battery 103 charges or stops charging the energy storage element C1; the second switch module 105 is used to realize the conduction or disconnection between the motor 102 and the battery 103 according to the control signal, so that the battery 103 outputs electrical energy to the motor 102 or stops outputting electrical energy.

[0049] In this embodiment, the bridge arm converter 101 and the motor 102 in the battery heating circuit can reuse the three-phase inverter and the motor in the vehicle motor drive circuit, and the energy storage module reuses the bus capacitor of the motor drive circuit, using the same module for different functions. By setting the first switch module 104 and the second switch module 105, components are reused to achieve multiple function switching, thereby increasing the utilization of the bridge arm converter 101 and the motor 102 and saving costs.

[0050] When the first switch module 104 is turned on and the second switch module 105 is turned off, the battery 103, the first switch module 104, the bridge arm converter 101, the energy storage element C1, and the motor 102 form a motor drive circuit. At this time, the motor output power is achieved by controlling the bridge arm converter 101.

[0051] Among them, when the first switch module 104 is turned off and the second switch module 105 is turned on, the battery 103, the second switch module 105, the motor 102, the bridge arm converter 101, and the energy storage element C1 form a battery heating circuit. At this time, the battery heating is achieved by controlling the bridge arm converter 101 to realize the charging and discharging of the battery 101 and the energy storage element C1.

[0052] When the first switch module 104 is turned off and the second switch module 105 is turned on, Figure 4 Can be equivalent to Figure 3 The first bus terminal of the bridge arm converter 101 is connected to the first end of the energy storage element C1, the second bus terminal of the bridge arm converter 101 is connected to the second end of the energy storage element C1, the first end of the motor 102 is connected to the bridge arm converter 101, the second end of the motor 102 is connected to the first end of the battery 101, and the second end of the battery 103 is connected to the second bus terminal of the bridge arm converter 101, forming a battery heating circuit.

[0053] The battery heating circuit includes a discharge circuit and a charging circuit. The discharge circuit refers to the discharge of the energy storage element C1 by the battery 103 through the motor 102 and the bridge arm converter 101. At this time, current flows out of the battery 103, and the current flows into the energy storage element C1 through the motor 102 and the bridge arm converter 101 to charge the energy storage element C1; the charging circuit refers to the charging of the battery 103 by the energy storage element C1 through the motor and the bridge arm converter 101. At this time, current flows out of the energy storage element C1, and the current flows through the bridge arm converter 101 and the motor 102 and flows into the battery 103. Due to the internal resistance in the battery 103, when the discharge circuit and the charging circuit are working, the internal resistance of the battery 103 will generate heat, thereby increasing the temperature of the battery 103.

[0054] When the battery heating circuit is working, the battery 103, the motor 102, and the bridge arm converter 101 form a discharge energy storage circuit, and the battery 103, the motor 102, the bridge arm converter 101, and the energy storage element C1 form a discharge energy release circuit; the energy storage element C1, the bridge arm converter 101, the motor 102, and the battery 103 form a charging energy storage circuit, and the motor 102, the battery 103, and the bridge arm converter 101 form a charging energy release circuit.

[0055] Among them, the discharge circuit includes a discharge energy storage circuit and a discharge energy release circuit, and the charging circuit includes a charging energy storage circuit and a charging energy release circuit. When the discharge energy storage circuit is controlled to work by the bridge arm converter 101, the battery 103 outputs electric energy to store energy in the winding of the motor; when the discharge energy release circuit is controlled to work by the bridge arm converter 101, the battery 103 discharges and the winding of the motor releases energy to charge the energy storage element C1; when the charging energy storage circuit is controlled to work by the bridge arm converter 101, the energy storage element C1 discharges to charge the battery 103, and the winding of the motor 102 stores energy; when the charging energy release circuit is controlled to work by the bridge arm converter 101, the winding of the motor 102 releases energy to charge the battery 103. By controlling the bridge arm converter 101, the discharge process of the battery 103 to the energy storage element C1 and the charging process of the energy storage element C1 to the battery 103 are alternately performed, so that the temperature of the battery 103 is increased; in addition, by controlling the duty cycle of the PWM control signal of the bridge arm converter 101, the current value flowing through the battery heating circuit is adjusted. Controlling the duty cycle is equivalent to controlling the conduction time of the upper bridge arm and the lower bridge arm. By controlling the conduction time of the upper bridge arm or the lower bridge arm to be longer or shorter, the current in the battery heating circuit will increase or decrease, and the heating power generated by the battery 103 can be adjusted.

[0056] It should be noted that, in the process of controlling the operation of the discharge circuit and the charging circuit, the discharge energy storage circuit, the discharge energy release circuit, the charging energy storage circuit and the charging energy release circuit in the discharge circuit can be controlled to operate in sequence, and the current value flowing through the battery heating circuit can be adjusted by controlling the duty cycle of the PWM control signal of the bridge arm converter 101. Alternatively, the discharge energy storage circuit and the discharge energy release circuit in the discharge circuit can be controlled to be alternately turned on for discharge, and then the charging energy storage circuit and the charging energy release circuit in the charging circuit can be controlled to be alternately turned on for discharge, and the current values ​​flowing through the discharge circuit and the charging circuit can be adjusted respectively by controlling the duty cycle of the PWM control signal of the bridge arm converter 101.

[0057] This embodiment controls the bridge arm converter 101 to operate the battery heating circuit, so that the battery 103 in the discharge circuit discharges the energy storage element C1 and the energy storage element C1 in the charging circuit charges the battery 103, thereby increasing the temperature of the battery 103. The bridge arm converter 101 can also be controlled to adjust the current in the self-heating circuit of the battery 103 and adjust the heating power generated by the battery 103.

[0058] As a second embodiment of the connection relationship between the bridge arm converter 101, the motor 102 and the energy storage element, Figure 5As shown, the first bus terminal of the bridge arm converter 101 is connected to the positive electrode of the battery 103, and the second bus terminal of the bridge arm converter 101 is connected to the negative electrode of the battery 103; the first end of the motor 102 is connected to the bridge arm converter 101, the second end of the motor 102 is connected to the first end of the energy storage element C2, and the second end of the energy storage element C2 is connected to the second bus terminal of the bridge arm converter 101, forming a battery heating circuit.

[0059] Among them, the difference between this embodiment and the above embodiment lies in the different connection methods between the modules. The specific structures of the modules are the same, and can be referred to the above embodiment, which will not be repeated here.

[0060] Among them, for the battery heating circuit, the battery heating circuit includes a discharge circuit and a charging circuit. The discharge circuit refers to the discharge of the energy storage element C2 by the battery 103 through the bridge arm converter 101 and the motor 102. At this time, current flows out of the battery 103, and the current flows into the energy storage element C2 through the bridge arm converter 101 and the motor 102 to charge the energy storage element C2; the charging circuit refers to the charging of the battery 103 by the energy storage element C2 through the motor 102 and the bridge arm converter 101. At this time, current flows out of the energy storage element C2, and the current flows through the motor 102 and the bridge arm converter 101 and flows into the battery 103. Due to the internal resistance in the battery 103, when the discharge circuit and the charging circuit are working, the battery 103 has current flowing in and out, which will cause the internal resistance of the battery to generate heat, thereby increasing the temperature of the battery 103.

[0061] like Figure 6 As shown, the control method includes step S10, step S20 and step S30, and the specific steps are as follows:

[0062] Step S10. When a battery heating instruction is obtained, the initial charge and discharge frequency is used as the target charge and discharge frequency of the battery heating circuit to control the bridge arm converter, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated.

[0063] Among them, obtaining a battery heating instruction refers to an instruction that causes the battery and other modules to form a heating circuit and generate heat. When the battery heating instruction is obtained, the battery heating circuit formed by connecting the bridge arm converter, the motor winding, the energy storage element and the battery is in a working state, and the bridge arm converter is controlled by the initial charge and discharge frequency to put the battery heating circuit in a working state, wherein the initial charge and discharge frequency can be determined by multiple charge and discharge frequencies preset for the battery.

[0064] Among them, the step of controlling the bridge arm converter with the initial charge and discharge frequency to charge and discharge the battery and the energy storage element in step S10 also includes obtaining the initial charge and discharge frequency, such as Figure 7As shown, the step of obtaining the initial charge and discharge frequency includes step S101, step S102, step S103 and step S104, and the specific steps are as follows:

[0065] Step S101: Acquire multiple charging and discharging frequencies of the battery.

[0066] In step S101, the charge and discharge frequency of the battery can be multiple values, for example, 50HZ, 95HZ, 250HZ, etc. There is a corresponding relationship between the charge and discharge frequency of the battery and the effective value of the current of the battery heating circuit. For example, the charge and discharge frequency of 50HZ corresponds to an effective current of 50A, the charge and discharge frequency of 95HZ corresponds to an effective current of 60A, the charge and discharge frequency of 250HZ corresponds to an effective current of 80A, and so on.

[0067] Step S102: Under each charge and discharge frequency of the battery, the duty cycle of the PWM control signal is adjusted to control the bridge arm converter to obtain the effective current value corresponding to each charge and discharge frequency.

[0068] Among them, different battery charge and discharge frequencies correspond to different effective current values ​​in the battery heating circuit. Different duty cycles of PWM control signals under the same battery charge and discharge frequency also correspond to different effective current values ​​in the battery heating circuit. Therefore, by keeping the battery charge and discharge frequency unchanged, the effective current value flowing through the battery heating circuit can be adjusted by adjusting the duty cycle of the PWM control signal, and the effective current value can be recorded by the current sensor.

[0069] Step S103: Obtain the effective current value corresponding to each charge and discharge frequency to obtain a current-frequency mapping table.

[0070] Step S104: Obtain the maximum current effective value according to the current effective value, and use the charge and discharge frequency corresponding to the maximum current effective value as the initial charge and discharge frequency.

[0071] The duty cycle of the PWM control signal is adjusted at each charge and discharge frequency in turn. For example, the duty cycle of the PWM control signal can be adjusted by gradually increasing or decreasing the change amount of the duty cycle of the PWM control signal. Then, multiple current effective values ​​corresponding to each charge and discharge frequency are obtained to obtain a current-frequency mapping table, in which the current effective values ​​in the current-frequency mapping table correspond to the charge and discharge frequency. The current effective values ​​in the current-frequency mapping table are sorted to obtain the maximum current effective value, and the corresponding charge and discharge frequency is obtained according to the maximum current effective value as the initial charge and discharge frequency.

[0072] The technical effect of this embodiment is that: the duty cycle of the PWM control signal is adjusted at each charge and discharge frequency to obtain the effective value of the current, and then the corresponding charge and discharge frequency is obtained according to the maximum effective value of the current as the initial charge and discharge frequency, so that the battery heating circuit can perform battery self-heating at a charge and discharge frequency close to the resonant frequency point, because the current value output by the battery is the largest at the resonant frequency point, so that the battery heating circuit can achieve an ideal self-heating effect

[0073] Step S20: Acquire the temperature parameters of the motor, and adjust the target charge and discharge frequency of the battery heating circuit according to the temperature parameters of the motor.

[0074] The temperature parameters of the motor include the motor rotor temperature and the motor stator temperature.

[0075] like Figure 8 As shown, as an implementation mode, adjusting the target charge and discharge frequency of the battery heating circuit according to the temperature parameter of the motor in step S20 includes:

[0076] Step S201: When at least one of the motor rotor temperature and the motor stator temperature reaches a preset temperature value, obtain a current effective value of the battery heating circuit under the current temperature parameters of the motor.

[0077] When the motor rotor temperature reaches the preset temperature value, or the motor stator temperature reaches the preset temperature value, or both the motor rotor temperature and the motor stator temperature reach the preset temperature value, it means that the motor temperature is too high and the motor iron loss is too large. The motor temperature needs to be adjusted, and the current effective value of the battery heating circuit is detected. The preset temperature value of the motor rotor can be the same as or different from the preset temperature value of the motor stator, and can be set according to actual needs.

[0078] Step S202: The current effective value of the current is adjusted down by a current difference ΔI.

[0079] The current effective value of the current is adjusted downward according to the preset current difference ΔI.

[0080] Step S203: Based on the current-frequency mapping table, the charge and discharge frequency corresponding to the reduced current effective value is used as the target charge and discharge frequency.

[0081] The current-frequency mapping table stores the corresponding relationship between the effective current value and the charge-discharge frequency, and the corresponding target charge-discharge frequency is searched in the current-frequency mapping table according to the reduced effective current value.

[0082] Step S30. Control the bridge arm converter to adjust the current flowing through the battery heating circuit according to the target charge and discharge frequency to adjust the iron loss of the motor.

[0083] Among them, under the target charge and discharge frequency, the corresponding PWM control signal is obtained according to the reduced current effective value, the bridge arm converter is controlled according to the PWM control signal, and the current reaches the current effective value by adjusting the duty cycle of the PWM control signal.

[0084] Among them, in the initial stage of battery self-heating, the initial charging and discharging frequency of the battery heating circuit is close to the resonant frequency point, for example, Figure 3 As shown in the figure, during the operation of the battery heating circuit, the resonant frequency of the battery heating circuit is 760HZ, that is, when the battery charge and discharge frequency is 760HZ, the maximum heating current value output by the battery is 259A. However, as the battery heating time increases, when the battery continues to be heated at the current current value, the iron core (ferromagnetic material) in the motor will experience hysteresis and eddy current under the action of the alternating magnetic field, and under the action of these two factors, the motor will produce core loss. The core loss will cause the motor rotor and stator silicon steel sheets to generate unnecessary heat or smoke during the battery self-heating process, resulting in damage to the motor.

[0085] The formula for iron loss per unit weight is as follows:

[0086]

[0087] Where: P Fe is the iron loss, unit is W / Kg, is the iron loss coefficient, f is the charge and discharge frequency of the battery, β is the frequency index, and its value is in the range of 1.2 to 1.6, which varies with the steel content of the silicon steel sheet. m is the amplitude of the AC magnetic flux component. This formula refers to when B m When =1T and f=50HZ, the iron loss per kilogram of silicon steel sheet is in the range of 1.05~2.5.

[0088] From the iron loss formula, it can be seen that the iron loss of the motor is strongly correlated with the charge and discharge frequency of the battery. As the charge and discharge frequency of the battery increases, the motor core loss will increase exponentially. Therefore, when the motor rotor and stator silicon steel sheets are seriously heated, when at least one of them reaches the preset temperature, the current effective value of the current is adjusted down by a current difference ΔI. For example, the current difference ΔI is 22A. Based on the current-frequency mapping table, the effective value of the current is 259A, which is adjusted down by 22A to 237A. The effective value of the current is 237A, corresponding to a charge and discharge frequency of 666HZ, and 666HZ is used as the target charge and discharge frequency. The heating phenomenon of the motor is improved by adjusting the charge and discharge frequency of the battery. The heating power of the battery is proportional to the internal resistance of the battery, and the internal resistance of the battery is proportional to the charge and discharge frequency. Therefore, the heating power of the battery is also proportional to the charge and discharge frequency, but the two are weakly correlated. Therefore, when the motor is seriously heated, adjusting the charge and discharge frequency of the battery will not have a significant impact on the heating power of the battery.

[0089] like Fig. 9 As shown, as an implementation mode, the duty cycle of the PWM control signal is adjusted in step S30 to control the switches of the upper and lower bridge arms of the bridge arm converter, including:

[0090] Step S301: Obtain the switching frequency of the bridge arm converter, and obtain the number of charge and discharge cycles of the bridge arm converter according to the switching frequency of the bridge arm converter and the charge and discharge frequency of the battery.

[0091] Among them, the switching frequency of the bridge arm converter is pre-set in the battery management system. There is a corresponding relationship between the switching frequency of the bridge arm converter and the charge and discharge frequency of the battery. In a battery charge and discharge cycle, the bridge arm converter switch must act continuously N times. The number of charge and discharge cycles of the bridge arm converter is obtained according to the ratio of the switching frequency of the bridge arm converter to the charge and discharge frequency of the battery.

[0092] Step S302: Adjust the duty cycle of the PWM control signal according to the number of charge and discharge cycles of the bridge arm converter.

[0093] There are multiple ways to adjust the duty cycle of the PWM control signal. The duty cycle can be adjusted according to multiple duty cycles corresponding to the charge and discharge frequency of the battery, or the duty cycle variation can be set and the duty cycle can be gradually adjusted according to the duty cycle variation.

[0094] The duty cycle of the control signal is changed according to a preset comparison value, and the duty cycle is gradually adjusted by counting the number of charge and discharge cycles through a counter, so that the current value of the battery heating circuit reaches the effective current value.

[0095] Further, after the step of using the charge and discharge frequency corresponding to the target current effective value as the target charge and discharge frequency, the method further includes:

[0096] After the preset time, if at least one of the motor rotor temperature and the motor stator temperature still reaches the preset temperature value, the current effective value of the current will be further reduced by a current difference ΔI, and the charging and discharging frequency corresponding to the further reduced current effective value will be used as the target charging and discharging frequency.

[0097] The specific control method is described in steps S201 to S203 and will not be described in detail here.

[0098] In this embodiment, in order to avoid severe heating of the motor, when the temperature of the motor rotor or stator silicon steel sheet reaches a certain set value, the effective value of the current will be adjusted downward in real time, and then the charge and discharge frequency will be adjusted to reduce the iron loss of the motor. The corresponding optimal battery heating current value is obtained according to the adjusted charge and discharge frequency, and this value is used for subsequent battery heating.

[0099] Embodiment 1 of the present application provides a control method for an energy conversion device, the energy conversion device includes a bridge arm converter, a motor and an energy storage element, the motor, the energy storage element and the battery are connected to form a battery heating circuit, and the control method includes: obtaining the vehicle state; when the vehicle state is in the heating mode, controlling the bridge arm converter to adjust the current flowing through the battery heating circuit, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated; obtaining the temperature parameters of the motor, and adjusting the bridge arm converter according to the temperature parameters of the motor to adjust the iron loss of the motor. The present application adjusts the bridge arm converter according to the change of the temperature parameters of the motor to achieve the control of the iron loss of the motor, thereby avoiding the phenomenon that the motor heats up or smokes as the heating time increases during the battery self-heating process.

[0100] The present embodiment is described in detail below through a specific circuit structure:

[0101] like Fig.10 As shown, the energy conversion device includes a bridge arm converter 101, a motor 102, a first switch module 104, a second switch module 105, a bus capacitor C1, an energy storage capacitor C2, and a switch K4. The first switch module 104 includes a switch K2, a switch K3, and a resistor R. The second switch module 105 includes a switch K1. The positive electrode of the battery 103 is connected to the first end of the resistor R and the first end of the switch K2. The second end of the resistor R is connected to the first end of the switch K3. The second end of the switch K3 is connected to the second end of the switch K2, the first end of the capacitor C1, and the first bus terminal of the bridge arm converter 101. The midpoints of the three bridge arms of the bridge arm converter 101 are respectively connected to the three coils of the motor 102. The connection points of the three coils of the motor 102 are connected to the first end of the switch K1. The second end of the switch K1 is connected to the first end of the energy storage capacitor C2. The second end of the energy storage capacitor C2 is connected to the second bus terminal of the bridge arm converter 101, the second end of the bus capacitor C1, and the second end of the switch K4.

[0102] Among them, the bridge arm converter 101 includes a first power switch unit, a second power switch unit, a third power switch unit, a fourth power switch unit, a fifth power switch unit and a sixth power switch unit. The first power switch unit and the fourth power switch unit form a first bridge arm, the third power switch unit and the sixth power switch unit form a second bridge arm, the fifth power switch unit and the second power switch unit form a third bridge arm, one end of the first power switch unit, the third power switch unit and the fifth power switch unit are connected together and constitute a first bus terminal of the bridge arm converter, one end of the second power switch unit, the fourth power switch unit and the sixth power switch unit are connected together and constitute a second bus terminal of the bridge arm converter, the first phase coil of the motor 102 is connected to the midpoint of the first bridge arm, the second phase coil of the motor 102 is connected to the midpoint of the second bridge arm, and the third phase coil of the motor 102 is connected to the midpoint of the third bridge arm.

[0103] The first power switch unit in the bridge arm converter 101 includes a first upper bridge arm VT1 and a first upper bridge diode VD1, the second power switch unit includes a second lower bridge arm VT2 and a second lower bridge diode VD2, the third power switch unit includes a third upper bridge arm VT3 and a third upper bridge diode VD3, the fourth power switch unit includes a fourth lower bridge arm VT4 and a fourth lower bridge diode VD4, the fifth power switch unit includes a fifth upper bridge arm VT5 and a fifth upper bridge diode VD5, the sixth power switch unit includes a sixth lower bridge arm VT6 and a sixth lower bridge diode VD6, the three-phase AC motor is a three-phase four-wire system, and can be a permanent magnet synchronous motor or an asynchronous motor, and a neutral line is drawn out at the midpoint of the three-phase coil connection.

[0104] like Fig.11 As shown, the bus capacitor is pre-charged before the energy conversion device is heated. The pre-charging control is specifically as follows: first, the switch K2 is disconnected to prepare for pre-charging, and then the switches K3 and K4 are closed to start pre-charging the bus capacitor C1. The battery 103 causes the voltage on the bus capacitor C1 to rise to a certain value, which is close to the voltage of the battery 103. Then the switch K2 is closed and the switch K3 is disconnected to complete the pre-charging process. If the voltage of the bus capacitor C1 fails to reach this determined value, the pre-charging fails and the entire program ends.

[0105] Then, when the bridge arm converter 101 is controlled to enter the high-frequency control mode, the formal heating process begins. During the battery heating process, a high switching frequency control method is adopted. In a battery charge and discharge cycle, the IGBT switch must act continuously N times, so the IGBT switching frequency is N times the battery charge and discharge frequency. By controlling the duty cycle, the charge and discharge current and capacitor voltage value are controlled. The battery self-heating process includes the following four working states:

[0106] The first stage is the discharge energy storage circuit operation: Fig.12 As shown, when the upper arm of the bridge arm converter 101 is turned on, the current flowing out from the positive electrode of the battery 103 is combined with the current flowing out from the bus capacitor C1 after passing through the switch K2, and then flows back to the negative electrode of the battery 103 and the bus capacitor C1 through the upper bridge arms (the first upper bridge arm VT1, the third upper bridge arm VT3, the fifth upper bridge arm VT5) of the bridge arm converter 101, the motor 102, the switch K1, and the energy storage capacitor C2, and the current continues to increase. In this process, the battery 103 and the bus capacitor C1 discharge to the outside, so that the voltage of the energy storage capacitor C2 continues to increase.

[0107] The second stage is the discharge energy release circuit operation: Fig.13As shown, the upper bridge arm of the bridge arm converter 101 is disconnected, the lower bridge arm is closed, the current flows out from the connection point of the three-phase coil of the motor 102, passes through the switch K1, flows to the positive electrode of the energy storage capacitor C2, and then flows back to the three-phase coil of the motor 102 through the lower bridge arm (the second lower bridge diode VD2, the fourth lower bridge diode VD4, and the sixth lower bridge diode VD6) of the bridge arm converter 101, the current continues to decrease, and the voltage of the energy storage capacitor C2 continues to increase. When the current drops to zero, the voltage of the capacitor C2 reaches the maximum value. At the same time, since the output current of the battery 103 decreases, the voltage at both ends of the battery 102 increases, and the bus capacitor C1 will continue to be charged. As the voltage of the capacitor bus C1 increases, the current also gradually decreases.

[0108] The third stage is the operation of the charging energy storage circuit: Fig.14 As shown, the lower bridge arm of the bridge arm converter 101 is disconnected, and the current flows out from the positive electrode of the energy storage capacitor C2, flows into the motor 102 through the switch K1, and then passes through the three-phase coil of the motor 102, and then passes through the upper bridge arm of the bridge arm converter 101 (the first upper bridge diode VD1, the third upper bridge diode VD3, and the fifth upper bridge diode VD5) to flow to the bus capacitor C1 and the positive electrode of the battery 103, and finally flows back to the negative electrode of the energy storage capacitor C2.

[0109] The fourth stage is the operation of the charging and energy release circuit: Fig.15 As shown, the lower bridge arm of the bridge arm converter 101 is controlled to be turned on, and the current flows out from the three-phase coil of the motor 102, passes through the lower bridge arms (the second lower bridge arm VT2, the fourth lower bridge arm VT4, and the sixth lower bridge arm VT6) of the bridge arm converter 101, flows to the negative electrode of the energy storage capacitor C2, and finally flows to the neutral point of the motor 102 through the switch K1. The voltage of the energy storage capacitor C2 continues to decrease, and the current also continues to decrease. At the same time, since the charging current of the battery 103 decreases, the voltage at both ends of the battery 103 decreases, and the bus capacitor C1 begins to charge the battery 103. As the voltage of the bus capacitor C1 decreases, the current gradually decreases to zero.

[0110] The above four processes are continuously cycled, so that the battery is continuously and rapidly charged and discharged. Due to the existence of the internal resistance of the battery, a large amount of heat is generated, causing the battery to heat up rapidly.

[0111] The control strategy for real-time adjustment of the charge and discharge frequency proposed in this application is to realize the battery self-heating function by controlling the IGBT through software. The specific implementation steps are as follows:

[0112] Step 1: Follow Fig.11 Connect the system hardware circuit as shown to ensure that all components function well.

[0113] Step 2: Given the IGBT switching frequency of the system, the switching frequency is generally fixed, and the corresponding number of cycles in the calculation program is obtained by the program software algorithm.

[0114] Step 3: Determine the initial charge and discharge frequency of the system based on system design requirements and simulation analysis results.

[0115] Step 4: Calculate the initial duty cycle based on the input and output voltage levels and the control principle of the hardware circuit of the current system.

[0116] Step 5: Calculate the counter of the control cycle configuration controller according to step 2, and determine the comparison value of the counter according to the duty cycle value calculated in step 4. The comparison value can also be set according to historical data. The comparison value is used to change the duty cycle of the control signal.

[0117] Step 6: Apply the control signal to the three-phase bridge arm of the bridge arm converter (the control of the three-phase bridge arm remains consistent), and change the charge and discharge current value by adjusting the duty cycle to achieve the battery charge and discharge function.

[0118] Step 7: During the charging and discharging process, always monitor the motor rotor temperature, the temperature of the motor stator silicon steel sheet, the three-phase current value, the battery charging and discharging current value, the current value on the capacitor C1 side, the voltage value at both ends of the battery, the voltage value at both ends of the C1 capacitor, the motor and IGBT temperature and other status parameters.

[0119] Step 8: Continuously monitor the motor rotor temperature and the motor stator silicon steel sheet temperature. When either temperature reaches the temperature setting value T, the battery charge and discharge frequency is reduced by one gear (for example, if the original charge and discharge frequency is 830HZ, the algorithm will reduce the charge and discharge frequency to 760HZ). The battery current output is the maximum output current value corresponding to the battery charge and discharge frequency after adjustment. Subsequent battery heating will output current at this current value.

[0120] Step 9: Re-set the duty cycle according to the adjusted charge and discharge frequency, so that the system outputs the maximum battery heating current value under the updated battery charge and discharge frequency. Subsequent battery heating will use this current value for battery self-heating.

[0121] Step 10: After the charge and discharge are completed, the battery charge and discharge current value is gradually reduced to 0 by reducing the duty cycle of the three-phase IGBT control signal, and the battery charge and discharge process is completed.

[0122] The above debugging steps are to charge and discharge the battery according to the current flowing out of the charging pile and into the motor through the motor. Fig.10 The present invention is described with reference to the system hardware structure shown in the figure, but is not limited to the above hardware structure and is also applicable to other situations with similar structures.

[0123] Embodiment 2 of the present invention further provides an energy conversion device, the energy conversion device comprising:

[0124] The bridge arm converter, the motor and the energy storage element are connected with the battery to form a battery heating circuit;

[0125] The energy conversion device further includes a control module, which is used to:

[0126] When a battery heating instruction is obtained, the initial charge and discharge frequency is used as the target charge and discharge frequency of the battery heating circuit to control the bridge arm converter, so that the battery and the energy storage element are charged and discharged, so that the battery can be self-heated; the temperature parameters of the motor are obtained, and the target charge and discharge frequency of the battery heating circuit is adjusted according to the temperature parameters of the motor; according to the target charge and discharge frequency, the bridge arm converter is controlled to adjust the current flowing through the battery heating circuit to adjust the iron loss of the motor.

[0127] Among them, the specific control method of the controller can refer to the above control method, which will not be repeated here.

[0128] The bridge arm converter includes N-phase bridge arms, the motor includes N-phase windings, and the N-phase bridge arms are connected to the N-phase windings in a one-to-one correspondence.

[0129] In one embodiment, the bridge arm converter, the motor, the energy storage element and the battery are connected to form a battery heating circuit, which specifically includes: the first ends of the N-phase bridge arms are connected together to form a first bus terminal, the first bus terminal is connected to the first end of the energy storage element, the second ends of the N-phase bridge arms are connected together to form a second bus terminal, the second bus terminal is connected to the second end of the energy storage element, the first ends of the N-phase windings are respectively connected one by one to the midpoints of the N-phase bridge arms, the second ends of the N-phase windings are connected to the positive pole of the battery, and the negative pole of the battery is connected to the second bus terminal.

[0130] In another embodiment, the bridge arm converter, the motor, the energy storage element and the battery are connected to form a battery heating circuit, which specifically includes:

[0131] The first ends of the N-phase bridge arms are connected together to form a first bus terminal, which is connected to the positive electrode of the battery. The second ends of the N-phase bridge arms are connected together to form a second bus terminal, which is connected to the negative electrode of the battery. The first ends of the N-phase windings are respectively connected to the midpoints of the N-phase bridge arms one by one, the second ends of the N-phase windings are connected to the first end of the energy storage element, and the second end of the energy storage element is connected to the second bus terminal.

[0132] The third embodiment of the present invention further provides a vehicle, comprising the energy conversion device provided in the first embodiment above.

[0133] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A control method for an energy conversion device, characterized in that: The energy conversion device comprises: A bridge arm converter, a motor and an energy storage element, wherein the bridge arm converter, the motor and the energy storage element are connected to a battery to form a battery heating circuit; The control method comprises: When a battery heating instruction is obtained, a plurality of charging and discharging frequencies of the battery are obtained; At each charge and discharge frequency of the battery, the bridge arm converter is controlled by adjusting the duty cycle of the PWM control signal to obtain the effective current value corresponding to each charge and discharge frequency; Obtaining the effective value of the current corresponding to each charge and discharge frequency to obtain a current-frequency mapping table; Using the charge and discharge frequency corresponding to the maximum current value in the current-frequency mapping table as the initial charge and discharge frequency; The bridge arm converter is controlled by using the initial charge and discharge frequency as the target charge and discharge frequency of the battery heating circuit, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated; acquiring a temperature parameter of the motor, and adjusting a target charge and discharge frequency of the battery heating circuit according to the temperature parameter of the motor; The bridge arm converter is controlled according to the target charge and discharge frequency to adjust the current flowing through the battery heating circuit to adjust the iron loss of the motor.

2. The control method according to claim 1, characterized in that: The obtaining of the temperature parameter of the motor comprises: A motor rotor temperature and a motor stator temperature in the motor are obtained.

3. The control method according to claim 2, characterized in that: The step of adjusting the target charge and discharge frequency of the battery heating circuit according to the temperature parameter of the motor includes: When at least one of the motor rotor temperature and the motor stator temperature reaches a preset temperature value, obtaining a current effective current value of the battery heating circuit under the current temperature parameter of the motor; The effective value of the current is adjusted down by a current difference ΔI; Based on the current-frequency mapping table, the charge and discharge frequency corresponding to the current effective value after the downward adjustment is used as the target charge and discharge frequency.

4. The control method according to claim 3, characterized in that: After the step of taking the charge and discharge frequency corresponding to the current effective value after the downward adjustment as the target charge and discharge frequency, the method further includes: After the preset time, if at least one of the motor rotor temperature and the motor stator temperature still reaches the preset temperature value, the current effective value of the current will continue to be reduced by a current difference ΔI, and the charging and discharging frequency corresponding to the current effective value after the further reduction will be used as the target charging and discharging frequency.

5. The control method according to claim 4, characterized in that: Controlling the bridge arm converter to adjust the current flowing through the battery heating circuit according to the target charge and discharge frequency includes: Acquire the switching frequency of the bridge arm converter, and acquire the number of charge and discharge cycles of the bridge arm converter according to the switching frequency of the bridge arm converter and the target charge and discharge frequency of the battery; The duty cycle of the PWM control signal is adjusted according to the number of charge and discharge cycles of the bridge arm converter to adjust the current flowing through the battery heating circuit.

6. The control method according to claim 1, characterized in that: The bridge arm converter, the motor, the energy storage element and the battery are connected to form a battery heating circuit, which specifically includes: the first ends of the N-phase bridge arms are connected together to form a first bus terminal, the first bus terminal is connected to the first end of the energy storage element, the second ends of the N-phase bridge arms are connected together to form a second bus terminal, the second bus terminal is connected to the second end of the energy storage element, the first ends of the N-phase windings are respectively connected one by one to the midpoints of the N-phase bridge arms, the second ends of the N-phase windings are connected to the positive pole of the battery, and the negative pole of the battery is connected to the second bus terminal.

7. The control method according to claim 1, characterized in that: The bridge arm converter, the motor, the energy storage element and the battery are connected to form a battery heating circuit, which specifically includes: The first ends of the N-phase bridge arms are connected together to form a first bus terminal, which is connected to the positive electrode of the battery. The second ends of the N-phase bridge arms are connected together to form a second bus terminal, which is connected to the negative electrode of the battery. The first ends of the N-phase windings are respectively connected to the midpoints of the N-phase bridge arms one by one, the second ends of the N-phase windings are connected to the first end of the energy storage element, and the second end of the energy storage element is connected to the second bus terminal.

8. An energy conversion device, characterized in that: The energy conversion device comprises: A bridge arm converter, a motor and an energy storage element, wherein the bridge arm converter, the motor and the energy storage element are connected to a battery to form a battery heating circuit; The energy conversion device further comprises a control module, wherein the control module is used for: When a battery heating instruction is obtained, a plurality of charging and discharging frequencies of the battery are obtained; At each charge and discharge frequency of the battery, the bridge arm converter is controlled by adjusting the duty cycle of the PWM control signal to obtain the effective current value corresponding to each charge and discharge frequency; Obtaining the effective value of the current corresponding to each charge and discharge frequency to obtain a current-frequency mapping table; Using the charge and discharge frequency corresponding to the maximum current value in the current-frequency mapping table as the initial charge and discharge frequency; The bridge arm converter is controlled by using the initial charge and discharge frequency as the target charge and discharge frequency of the battery heating circuit, so that the battery and the energy storage element are charged and discharged, so that the battery is self-heated; acquiring a temperature parameter of the motor, and adjusting a target charge and discharge frequency of the battery heating circuit according to the temperature parameter of the motor; The bridge arm converter is controlled according to the target charge and discharge frequency to adjust the current flowing through the battery heating circuit to adjust the iron loss of the motor.

9. A vehicle, characterized in that: The vehicle comprises the energy conversion device according to claim 8.

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