Energy conversion device and control method thereof

Abstract

The technical solution of the present application provides an energy conversion device and a control method thereof. The energy conversion device includes a bridge arm converter, a first battery pack, a motor, a second battery pack and a controller. The controller is used to obtain the battery parameters of the first battery pack and the battery parameters of the second battery pack, and control the bridge arm converter according to the battery parameters, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the first battery pack, or heating and / or charging of the second battery pack. Compared with the prior art, the present application reuses the bridge arm converter and the motor in the vehicle, which are respectively connected to the first battery pack and the second battery pack, and determines the duty cycle of the bridge arm converter by obtaining the battery parameters of the first battery pack and the second battery pack, thereby achieving heating and / or starting between the first battery pack and the second battery pack, and starting the battery.

Description

Technical Field

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

[0002] With the widespread use of new energy, battery packs can be used as power sources in various fields. The performance of the battery pack will be affected by the different environments in which the battery pack is used as a power source. For example, the performance of the battery pack in a low temperature environment will be greatly reduced compared to normal temperature. For example, at zero temperature, the discharge capacity of the battery pack will decrease as the temperature decreases. Under -30°C conditions, the discharge capacity of the battery pack is basically 0, which makes the battery pack unusable, and then the vehicle cannot start. In order to be able to use the battery pack in a low temperature environment, the battery pack needs to be preheated before using it. Summary of the invention

[0003] The purpose of the present application is to provide an energy conversion device and a control method thereof, which can heat the battery by controlling the bridge arm converter and then start the battery.

[0004] The present application is implemented in this way. In a first aspect, the present application provides an energy conversion device, characterized in that the energy conversion device comprises:

[0005] A bridge arm converter, wherein the first ends of the bridge arms of the bridge arm converter are connected together to form a first bus terminal, and the second ends of the bridge arms of the bridge arm converter are connected together to form a second bus terminal;

[0006] A first battery pack, wherein a first polarity end of the first battery pack is connected to the first bus terminal, and a second polarity end of the first battery pack is connected to the second bus terminal;

[0007] Second battery pack;

[0008] A motor, wherein a first end of a motor winding of the motor is connected to the bridge arm converter, a second end of the motor winding is connected together to form a neutral point and is connected to a first polarity end of a second battery pack, and a second polarity end of the second battery pack is connected to a second bus terminal of the bridge arm converter;

[0009] A controller is used to obtain battery parameters of the first battery pack and battery parameters of the second battery pack, and control the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the first battery pack, or heating and / or charging of the second battery pack.

[0010] The present application provides an energy conversion device and a control method thereof. The energy conversion device includes a bridge arm converter, a first battery pack, a motor, a second battery pack, and a controller. The controller is used to obtain battery parameters of the first battery pack and battery parameters of the second battery pack, and control the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack so that the first battery pack, the bridge arm converter, the motor winding, and the second battery pack form different current loops to achieve heating and / or charging of the first battery pack, or heating and / or charging of the second battery pack. Compared with the prior art, the present application reuses the bridge arm converter and the motor in the vehicle, which are respectively connected to the first battery pack and the second battery pack, and determines the duty cycle of the bridge arm converter by obtaining the battery parameters of the first battery pack and the second battery pack, thereby achieving heating and / or starting between the first battery pack and the second battery pack, thereby achieving battery starting. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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.

[0012] Figure 1 is a circuit diagram of an energy conversion device provided in Example 1 of the present application;

[0013] Figure 2 is another circuit diagram of an energy conversion device provided in Example 1 of the present application;

[0014] Figure 3 is a flow chart of a control method of an energy conversion device provided in Example 2 of the present application;

[0015] Figure 4 is a specific flow chart of step S102 in a control method for an energy conversion device provided in Embodiment 2 of the present application;

[0016] Figure 5 It is a schematic diagram of a current time variation curve in a control method of an energy conversion device provided in Example 2 of the present application;

[0017] Figure 6 is another specific flow chart of step S102 in a control method for an energy conversion device provided in Embodiment 2 of the present application;

[0018] Figure 7 is another specific flow chart of step S102 in a control method for an energy conversion device provided in Embodiment 2 of the present application;

[0019] Figure 8 is another specific flow chart of step S102 in a control method for an energy conversion device provided in Embodiment 2 of the present application;

[0020] Fig. 9 is another specific flow chart of step S102 in a control method for an energy conversion device provided in Embodiment 2 of the present application;

[0021] Fig.10 is a circuit diagram of an energy conversion device provided in Example 2 of the present application;

[0022] Fig.11 This is a schematic diagram of voltage difference and current waveforms in a control method for an energy conversion device provided in Example 2 of the present application;

[0023] Fig.12 is a schematic diagram of the structure of an energy conversion device provided in Example 2 of the present application;

[0024] Fig.13 is a current flow diagram of an energy conversion device provided in Example 2 of the present application;

[0025] Fig.14 is another current flow diagram of an energy conversion device provided in Example 2 of the present application;

[0026] Fig.15 is another current flow diagram of an energy conversion device provided in Example 2 of the present application;

[0027] Fig.16 This is another current flow diagram of an energy conversion device provided in Example 2 of the present application. DETAILED DESCRIPTION

[0028] 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.

[0029] In order to illustrate the technical solution of the present application, a specific embodiment is provided below for illustration.

[0030] Embodiment 1 of the present application provides an energy conversion device, such as Figure 1 As shown, the energy conversion device includes:

[0031] 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;

[0032] A first battery pack 103, wherein a first polarity end of the first battery pack 103 is connected to the first bus terminal, and a second polarity end of the first battery pack 103 is connected to the second bus terminal;

[0033] A second battery pack 104;

[0034] The motor 102, the first end of the motor winding of the motor 102 is connected to the bridge arm converter 101, the second end of the motor winding is connected together to form a neutral point and connected to the first polarity end of the second battery pack 104, and the second polarity end of the second battery pack 104 is connected to the second bus terminal of the bridge arm converter 101;

[0035] The controller is used to obtain the battery parameters of the first battery pack 103 and the battery parameters of the second battery pack 104, and control the bridge arm converter according to the battery parameters of the first battery pack 103 and the battery parameters of the second battery pack 104, so that the first battery pack 103, the bridge arm converter 101, the motor winding and the second battery pack 104 form different current loops to achieve heating and / or charging of the first battery pack 103, or heating and / or charging of the second battery pack 104.

[0036] Among them, the energy conversion device can also include a first capacitor C1 and a second capacitor C2, the first end of the first capacitor C1 is connected to the first bus terminal, and the second end of the first capacitor C1 is connected to the second bus terminal; the first end of the second capacitor C2 is connected to the first polarity end of the second battery pack 104, and the second end of the second capacitor C2 is connected to the second polarity end of the second battery pack 104.

[0037] 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 102 includes M-phase windings, the first end of each phase winding in the M-phase windings is respectively connected to the midpoint of each bridge arm in the M bridge arms in a one-to-one correspondence, 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 second capacitor C2.

[0038] For example, when M=3, the bridge arm converter 101 includes three bridge arms, the first end of each of 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 of the three bridge arms is connected in common to form a second bus terminal of the bridge arm converter 101; 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 and a sixth power switch, the first power switch unit and the fourth power switch unit are connected in series to form a first bridge arm, the second power switch unit and the fifth switch unit are connected in series to form a second bridge arm, the third power switch unit and the sixth switch unit are connected in series to 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 series to form a first bus terminal of the bridge arm converter 101, and one end of the second power switch unit, the fourth power switch unit and the sixth power switch unit are connected in series to form a second bus terminal of the bridge arm converter 101.

[0039] Among them, the motor winding includes M-phase windings, the first end of each phase winding in the M-phase windings is the first end of the motor winding, the first end of each phase winding in the M-phase windings is connected to the midpoint of each bridge arm in the M bridge arms one by one, and the second end of each phase winding in the M-phase windings is connected together to form a neutral point.

[0040] For example, corresponding to the bridge arm converter 101, when the bridge arm converter 101 includes three bridge arms, the motor winding includes a three-phase winding, the first end of each phase winding in the three-phase winding is connected to the midpoint of each bridge arm in the three bridge arms in a one-to-one correspondence, and the second end of each phase winding in the three-phase winding is connected together to form a neutral point. The first phase winding of the three-phase winding is connected to the midpoint of the first bridge arm, the second phase winding of the three-phase winding is connected to the midpoint of the second bridge arm, and the third phase winding of the three-phase winding is connected to the midpoint of the third bridge arm.

[0041] The controller (not shown) may include a vehicle controller, a control circuit of the bridge arm converter 101, and a BMS battery manager circuit, which are connected via a CAN line. The controller may be a controller of the first battery pack, communicating with a controller of the second battery pack, or a controller of the second battery pack, communicating with a controller of the first battery pack, or a controller of the first battery pack and a controller of the second battery pack.

[0042] The controller is used to obtain the battery parameters of the first battery pack 103 and the battery parameters of the second battery pack 104, and control the bridge arm converter according to the battery parameters of the first battery pack 103 and the battery parameters of the second battery pack 104, so that the first battery pack 103, the bridge arm converter 101, the motor winding and the second battery pack 104 form different current loops to achieve heating and / or charging of the first battery pack 103, or heating and / or charging of the second battery pack 104.

[0043] The selection of battery parameters for the first battery pack 10 and the second battery pack 104 is determined by the working scenario. The battery parameters of the first battery pack 103 may be temperature, maximum discharge current, and maximum charging power. The battery parameters of the second battery pack may be temperature, maximum discharge current, and maximum charging power. When the temperature of the first battery pack 103 is lower than a preset temperature and the temperature of the second battery pack 104 is a normal temperature, or when the temperature of the second battery pack is lower than a preset temperature and the temperature of the first battery pack 103 is a normal temperature, the controller controls the bridge arm converter so that the first battery pack 103, the bridge arm converter 101, the motor winding, and the second battery pack 104 form different current loops to achieve heating and / or charging of the first battery pack or the second battery pack.

[0044] When the controller controls the bridge arm converter to heat the first battery pack or the second battery pack, the first battery pack, the bridge arm converter, the motor winding, and the second battery pack form a first heating circuit, and the motor winding, the bridge arm converter and the second battery pack form a second heating circuit, wherein when the second battery pack is heated, when the first heating circuit is working, the first battery pack charges the second battery pack through the bridge arm converter and the motor winding, at this time, current flows out of the first battery pack, and the current flows into the second battery pack through the bridge arm converter and the motor winding to charge the second battery pack; when the second heating circuit is working, the motor winding discharges the second battery pack through the bridge arm converter; due to the internal resistance in the second battery pack, when the first heating circuit and the second heating circuit are alternately executed by controlling the bridge arm converter, current flows in and out of the second battery pack, which causes the internal resistance of the second battery pack to generate heat, thereby increasing the temperature of the second battery pack. Similarly, the first battery pack can be heated, the second battery pack, the motor winding, the bridge arm converter form a third heating circuit, the second battery pack, the motor winding, the bridge arm converter, and the first battery pack form a fourth heating circuit, when the third heating circuit is working, the second battery pack discharges the motor winding through the bridge arm converter; when the fourth heating circuit is working, the second battery pack and the motor winding discharge the first battery pack through the bridge arm converter; due to the internal resistance in the first battery pack, when the discharge process and the charging process are executed, the current flowing into and out of the first battery pack will cause the internal resistance of the first battery pack to generate heat, thereby increasing the temperature of the first battery pack. Alternatively, the heating circuit can also be a charging circuit, when the charging circuit is operated by the bridge arm converter, the first battery pack charges the second battery pack, or the second battery pack charges the first battery pack. Alternatively, the heating circuit can also be a charging heating circuit, when the charging heating circuit is operated by the bridge arm converter, the first battery pack charges and heats the second battery pack at the same time, or the second battery pack charges and heats the first battery pack.

[0045] Among them, the first battery pack can be used in the first vehicle, and the second battery pack can be used in the second vehicle. When the second battery pack of the second vehicle cannot be started due to the low ambient temperature, the first battery pack can be used to heat and charge the second battery pack through the energy conversion device, thereby starting the second battery pack.

[0046] As an embodiment, the energy conversion device further includes an inductor, such as Figure 2 As shown, the inductor is connected between the neutral point of the motor winding and the positive electrode of the second battery pack.

[0047] Among them, by adding inductance in the energy conversion device, it is used for filtering and energy storage, as well as improving the charging and discharging efficiency and having a buffering effect.

[0048] Embodiment 2 of the present application provides a control method based on an energy conversion device, such as Figure 3 As shown, the control method of the energy conversion device includes:

[0049] Step S101: Obtain battery parameters of a first battery pack and battery parameters of a second battery pack.

[0050] Among them, for step S101, when the first battery pack and the second battery pack are controlled to be in different states, the battery parameters of the first battery pack and the battery parameters of the second battery pack are different. For example, when the second battery pack is heated, the maximum discharge current of the first battery pack is obtained, and the temperature and the maximum discharge current of the second battery pack are obtained; when the second battery pack is heated and charged, the maximum discharge current and the maximum charging power of the first battery pack are obtained, and the temperature, the maximum discharge current and the maximum charging power of the second battery pack are obtained; when the first battery pack is heated, the maximum discharge current of the second battery pack is obtained, and the temperature and the maximum discharge current of the first battery pack are obtained; when the first battery pack is heated and charged, the maximum discharge current and the maximum charging power of the second battery pack are obtained, and the temperature, the maximum discharge current and the maximum charging power of the first battery pack are obtained.

[0051] Step S102. Control the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the first battery pack, or heating and / or charging of the second battery pack.

[0052] Among them, for step S102, as an implementation mode, the application scenario of this implementation mode is that the temperature is extremely low, and only the second battery pack is heated. At this time, the battery parameters of the first battery pack and the battery parameters of the second battery pack are obtained, including:

[0053] The maximum discharge current of the first battery pack is obtained, and the temperature and the maximum discharge current of the second battery pack are obtained.

[0054] The controller may obtain the maximum discharge current of the first battery pack, and the temperature and the maximum discharge current of the second battery pack by communicating with the power manager of the first battery pack and the power manager of the second battery pack.

[0055] In this embodiment, if Figure 4 As shown, step S102 includes:

[0056] Step S121. When the temperature of the second battery pack is lower than the first preset temperature value, a target current amplitude of a target current waveform of the current loop is obtained according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack.

[0057] Among them, the first preset temperature value is a lower temperature value, such as -40°C. At this time, the temperature of the second battery pack is low, and the second battery pack needs to be heated. The first battery pack is used to discharge the second battery pack through a heating circuit to achieve heating of the second battery pack.

[0058] Wherein, obtaining the target current amplitude of the target current waveform of the current loop according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack in step S121 includes:

[0059] The smaller current value of the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack is obtained, and the target current amplitude of the target current waveform of the current loop is obtained by doubling the smaller current value.

[0060] Step S122. Obtain a target duty cycle according to a target current amplitude and a target current waveform function.

[0061] Among them, the target current waveform function is y=((A*sin(2*pi*f*t)+B)*R+Ub) / Ua; A is the target current amplitude of the current waveform, f is the current frequency, B is the target current average value, R is the sum of the internal resistance of the first battery pack and the second battery pack, Ua is the voltage of the first battery pack, Ub is the voltage of the second battery pack, and y is the target duty cycle.

[0062] Among them, under the conditions provided in this embodiment, in the above-mentioned target current waveform function, A can be obtained from step S121, the current frequency f is a fixed frequency, for example, 800 Hz, and the target current average value B is 0. The target duty cycle y can be obtained by bringing it into the target current waveform function, wherein the target current waveform is as follows: Figure 5 Phase A shown.

[0063] Step S123. Control the bridge arm converter according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to heat the second battery pack.

[0064] Among them, controlling the bridge arm converter according to the target duty cycle to charge and discharge the first battery pack and the second battery pack means controlling the bridge arm converter according to the target duty cycle to make the first heating circuit formed by the bridge arm converter, the motor winding, and the second battery pack and the second heating circuit formed by the motor winding, the bridge arm converter and the second battery pack work alternately, and the current flowing into and out of the second battery pack will cause the internal resistance of the second battery pack to generate heat, thereby increasing the temperature of the second battery pack.

[0065] The technical effect of this embodiment is that when it is detected that one of the first battery pack and the second battery pack is in an extremely low temperature condition and cannot be started, the duty cycle is obtained according to the battery parameters of the first battery pack and the second battery pack, and the bridge arm converter is controlled according to the duty cycle to heat the first battery pack or the second battery pack, thereby starting the first battery pack or the second battery pack.

[0066] Among them, for step S102, as an implementation mode, the application environment of this implementation mode is to heat and charge the second battery pack at a lower temperature, and obtain the battery parameters of the first battery pack and the battery parameters of the second battery pack, including:

[0067] The maximum discharge current and the maximum charge power of the first battery pack are obtained, and the temperature, the maximum discharge current, and the maximum charge power of the second battery pack are obtained.

[0068] The controller may obtain the maximum discharge current and maximum charging power of the first battery pack, and obtain the temperature, maximum discharge current, and maximum charging power of the second battery pack by communicating with the power manager of the first battery pack and the power manager of the second battery pack.

[0069] In this embodiment, if Figure 6 As shown, step S102 includes:

[0070] Step S124. When the temperature of the second battery pack is not lower than the first preset temperature value and lower than the second preset temperature, the target current average value of the target current waveform of the current loop is obtained according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack, and the target current amplitude of the target current waveform of the current loop is obtained according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack.

[0071] The temperature of the second battery pack being not lower than the first preset temperature value and lower than the second preset temperature means that under the condition of low battery temperature, for example, -20°C, the second battery pack can be charged at a low power while still meeting the heating requirement.

[0072] Wherein, in step S124, obtaining a target current average value of a target current waveform of a current loop according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack includes:

[0073] The target current average value is obtained according to the smaller maximum charging power of the first battery pack and the maximum charging power of the second battery pack.

[0074] Among them, since the maximum charging power of the second battery pack is related to the temperature of the second battery pack, when the temperature of the second battery pack does not reach the minimum temperature that meets the maximum charging power of the second battery pack, the maximum charging power of the second battery pack will increase with the increase of the temperature of the second battery pack. When the maximum charging power of the second battery pack increases, the target current average value also increases accordingly.

[0075] Wherein, in step S124, obtaining the target current amplitude of the target current waveform of the current loop according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack includes:

[0076] The smaller current value of the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack is obtained, and the target current amplitude of the target current waveform of the current loop is obtained by performing a difference operation and then doubling the smaller current value and the target current average value.

[0077] Step S125. Obtain a target duty cycle according to a target current average value, a target current amplitude, and a target current waveform function.

[0078] Among them, the target current waveform function is y=((A*sin(2*pi*f*t)+B)*R+Ub) / Ua; A is the target current amplitude of the current waveform, f is the current frequency, B is the target current average value, R is the sum of the internal resistance of the first battery pack and the second battery pack, Ua is the voltage of the first battery pack, Ub is the voltage of the second battery pack, and y is the target duty cycle.

[0079] Among them, under the conditions provided in this embodiment, A and B can be obtained from step S124 in the above-mentioned target current waveform function, and the current frequency f is a fixed frequency, such as 800 Hz, which can be brought into the target current waveform function to obtain the target duty cycle y, wherein the target current waveform is as follows: Figure 5 Phase B shown.

[0080] Among them, since the maximum charging power of the second battery pack increases as the temperature of the second battery pack increases, when the maximum charging power of the second battery pack increases, the target current average value also increases accordingly, and therefore, the duty cycle also changes accordingly.

[0081] Step S126. Control the bridge arm converter according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, charge the second battery pack with the target current average value and heat the second battery pack with the target current amplitude.

[0082] Among them, controlling the bridge arm converter according to the target duty cycle to charge and discharge the first battery pack and the second battery pack means controlling the bridge arm converter according to the target duty cycle to make the first heating and charging circuit formed by the bridge arm converter, the motor winding, and the second battery pack and the second heating and charging circuit formed by the motor winding, the bridge arm converter and the second battery pack work alternately. Due to the internal resistance in the second battery pack, when the heating and discharging process and the heating and charging process are performed, current flows into and out of the second battery pack, which causes the internal resistance of the second battery pack to generate heat, thereby increasing the temperature of the second battery pack, and charging the second battery pack at the same time.

[0083] The technical effect of this embodiment is that when it is detected that one of the first battery pack and the second battery pack is at a low temperature and cannot be started, the duty cycle is obtained according to the battery parameters of the first battery pack and the second battery pack, and the bridge arm converter is controlled according to the duty cycle to heat and charge the first battery pack or the second battery pack, thereby starting the first battery pack or the second battery pack.

[0084] Among them, for step S102, as an implementation mode, the application environment of this implementation mode is that the battery temperature is within a preset temperature range, at this time, the second battery pack is heated and charged, and the battery parameters of the first battery pack and the battery parameters of the second battery pack are obtained, including:

[0085] The maximum discharge current and the maximum charge power of the first battery pack are obtained, and the temperature, the maximum discharge current, and the maximum charge power of the second battery pack are obtained.

[0086] As an implementation method, Figure 7 As shown, step S102 includes:

[0087] Step S127. When the temperature of the second battery pack is not lower than the second preset temperature value and lower than the third preset temperature, the target current average value of the target current waveform of the current loop is obtained according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack, and the target current amplitude of the target current waveform of the current loop is obtained according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack.

[0088] The temperature of the second battery pack being not lower than the second preset temperature value and lower than the third preset temperature means that when the battery has a certain temperature, such as 15° C., the second battery pack can be charged and still has a heating requirement.

[0089] Wherein, in step S127, obtaining a target current average value of a target current waveform of a current loop according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack includes:

[0090] The target current average value is obtained according to the smaller maximum charging power of the first battery pack and the maximum charging power of the second battery pack.

[0091] Among them, since the maximum charging power of the second battery pack is related to the temperature of the second battery pack, when the temperature of the second battery pack reaches the minimum temperature that meets the maximum charging power of the second battery pack, the maximum charging power of the second battery pack remains unchanged when the temperature of the second battery pack increases, and the target current average value also remains unchanged.

[0092] Step S128. Obtain a target duty cycle according to a target current average value, a target current amplitude, and a target current waveform function.

[0093] Among them, the target current waveform function is y=((A*sin(2*pi*f*t)+B)*R+Ub) / Ua; A is the target current amplitude of the current waveform, f is the current frequency, B is the target current average value, R is the sum of the internal resistance of the first battery pack and the second battery pack, Ua is the voltage of the first battery pack, Ub is the voltage of the second battery pack, and y is the target duty cycle.

[0094] Among them, under the conditions provided in this embodiment, A and B can be obtained from step S124 in the above-mentioned target current waveform function, and the current frequency f is a fixed frequency, such as 800 Hz, which can be brought into the target current waveform function to obtain the target duty cycle y, wherein the target current waveform is as follows: Figure 5 Stage C is shown.

[0095] Step S129. Control the bridge arm converter according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, charge the second battery pack with the target current average value and heat the second battery pack with the target current amplitude.

[0096] Among them, controlling the bridge arm converter according to the target duty cycle to charge and discharge the first battery pack and the second battery pack means controlling the bridge arm converter according to the target duty cycle to make the first heating and charging circuit formed by the bridge arm converter, the motor winding, and the second battery pack and the second heating and charging circuit formed by the motor winding, the bridge arm converter and the second battery pack work alternately; due to the internal resistance in the second battery pack, when the heating and discharging process and the heating and charging process are performed, current flows into and out of the second battery pack, which causes the internal resistance of the second battery pack to generate heat, thereby increasing the temperature of the second battery pack, and charging the second battery pack at the same time.

[0097] The technical effect of this embodiment is that when it is detected that one of the first battery pack and the second battery pack is under certain temperature conditions, the duty cycle is obtained according to the battery parameters of the first battery pack and the second battery pack, and the bridge arm converter is controlled according to the duty cycle to heat and charge the first battery pack or the second battery pack, thereby achieving heating and charging of the first battery pack or the second battery pack.

[0098] Wherein, as an implementation mode, step S102 is applied in an environment where the battery temperature is within a preset temperature range but the external environment temperature is low, and the battery parameters of the first battery pack and the battery parameters of the second battery pack are obtained, including:

[0099] Obtaining a maximum discharge current and a maximum charging power of the first battery pack, and obtaining a temperature, a maximum discharge current, and a maximum charging power of the second battery pack;

[0100] Step S102 includes:

[0101] Step S130: When the temperature of the second battery pack reaches the optimal charging temperature and the ambient temperature is lower than a fourth preset temperature value, a target current average value of the target current waveform of the current loop is obtained according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack.

[0102] Step S131. When the temperature of the second battery pack is detected to be lower than the optimal charging temperature, the target current amplitude is obtained according to the corresponding relationship between the temperature and the target current amplitude, and the target duty cycle is obtained according to the target current average value, the target current amplitude and the target current waveform function.

[0103] When the battery temperature reaches the optimal charging temperature, the battery needs to be heated due to the low ambient temperature. At this time, the current value corresponding to the maximum charging power is the average self-heating current. The optimal battery temperature is the control target. By monitoring the battery temperature in real time as the feedback value of the PID closed-loop control, the self-heating current amplitude is controlled in real time to keep the battery at the optimal temperature. The target current waveform is as follows: Figure 5 Stage D is shown.

[0104] Step S132. Control the bridge arm converter according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to heat and charge the second battery pack while maintaining the temperature of the second battery pack at an optimal charging temperature.

[0105] The technical effect of this embodiment is that when it is detected that one of the first battery pack and the second battery pack is under certain temperature conditions and the ambient temperature is low, the duty cycle is obtained according to the battery parameters of the first battery pack and the second battery pack, the duty cycle is adjusted according to the temperature of the battery pack, and the bridge arm converter is controlled according to the duty cycle to heat and charge the first battery pack or the second battery pack, thereby maintaining the temperature of the first battery pack or the second battery pack.

[0106] Among them, for step S102, as an implementation mode, the application environment of this implementation mode is that the battery temperature is the optimal charging temperature and no heating is required.

[0107] like Fig. 9 As shown, step S102 includes:

[0108] Step S133. When the temperature of the second battery pack reaches the optimal charging temperature and heating is not required, the target current amplitude is controlled to gradually decrease so that the duty cycle of the bridge arm converter is a fixed value;

[0109] Step S134. Controlling the bridge arm converter according to the duty cycle of the bridge arm converter to charge and discharge the first battery pack and the second battery pack, so as to charge the second battery pack;

[0110] Step S135: When it is detected that the second battery pack is in a fully charged state, the duty cycle is reduced to 0.

[0111] Among them, in the above steps, when the battery temperature is the optimal charging temperature and no heating is required, the battery self-heating current amplitude gradually decreases until it reaches zero. Figure 5 As shown in the E phase of the charging current waveform, the charging current waveform is the same as the conventional charging waveform. Figure 5 As shown in stage F, the charging is completed and the charging current gradually decreases to 0, completing the charging process.

[0112] The present application is described in detail below through a specific circuit structure:

[0113] The present application proposes an energy conversion device, such as Fig.10As shown, firstly, the N line of the motor is led out, and the second capacitor C2 is connected. Then, through the switching of the contactor, not only the torque output in the normal driving state, the DC charging in the parking state and the battery charging in the parking state can be realized, but also the battery heating can be performed when the battery is charged. The battery heating function mainly realizes the rapid charging and discharging between the first battery pack and the second battery pack by controlling the high-frequency switching of the IGBT of the bridge arm converter. Due to the existence of the internal resistance of the battery, a large amount of heat is generated inside the battery to achieve the purpose of battery heating.

[0114] like Fig.10 As shown, the energy conversion device includes a bridge arm converter 101, a motor winding, a first capacitor C1, a second capacitor C2, a switch K1, a switch K2, a switch K3, a switch K4, a switch K5, a resistor R, a first battery pack 103 and a second battery pack 104, a positive electrode of the first battery pack 103 is connected to a first end of the resistor R and a first end of the switch K2, a second end of the resistor R is connected to a first end of the switch K3, a second end of the switch K3 is connected to a second end of the switch K2, a first end of the first capacitor C1 and a first busbar 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-phase windings of the motor windings, the connection points of the three-phase windings of the motor windings 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 second capacitor C2 and the positive electrode of the second battery pack 104, the second end of the second capacitor C2 is connected to the second bus terminal of the bridge arm converter 101, the second end of the first capacitor C1, the second end of the switch K4, the first end of the switch K5, and the negative electrode of the first battery pack 103, and the second end of the switch K5 is connected to the negative electrode of the second battery pack 104.

[0115] 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 101, 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 101, the first phase winding of the motor winding is connected to the midpoint of the first bridge arm, the second phase winding of the motor winding is connected to the midpoint of the second bridge arm, and the third phase winding of the motor winding is connected to the midpoint of the third bridge arm.

[0116] 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 winding connection.

[0117] In the normal driving mode, switches K1 and K5 are disconnected, and the first capacitor C1 is between the positive and negative electrodes of the bus. The first capacitor C1 can effectively stabilize the bus voltage, absorb ripple current, and improve the reliability of IGBT operation and the output efficiency of the battery pack. According to the torque requirements of the vehicle, the controller controls the IGBT to achieve the output of the motor torque to meet the driving function of the vehicle.

[0118] In the vehicle VTOV mode, switches K1 and K5 are closed, and the first capacitor C1 is connected between the positive and negative poles of the busbar, one end of the second capacitor C2 is connected to the negative pole of the busbar, and the other end is connected to the motor point N through switch K1. The controller controls the IGBT to achieve rapid alternation of charging and discharging of the first battery pack and the second battery pack, so that the battery pack continuously outputs or inputs current. Due to the existence of the battery internal resistance, a large amount of heat is generated inside the battery, and the battery heats up rapidly. The controller controls the switching action of the three-phase bridge arm, so that the first battery pack and the second battery pack are continuously and rapidly charged and discharged. Due to the existence of the battery pack internal resistance, a large amount of heat is generated, causing the battery pack to heat up rapidly.

[0119] The duty cycle in each battery charge and discharge cycle determines whether the current increases or decreases, that is, it determines the direction of current change. Specifically: an increase in the duty cycle of the lower bridge arm will cause the discharge current of the second battery pack to increase, or the charging current of the second battery pack to decrease; a decrease in the duty cycle of the lower bridge arm will cause the discharge current of the second battery pack to decrease, or the charging current of the second battery pack to increase. Through continuous and multiple duty cycle adjustments, not only the maximum and minimum values ​​of the current can be controlled, but also the shape of the current can be controlled. During VTOV, sinusoidal current waveform self-heating, sinusoidal current waveform self-heating while charging, and DC charging can be achieved. Overall, the first battery pack and the second battery pack interact with each other, and changes in the charge and discharge current of the second battery pack will also be reflected in the charge and discharge current of the first battery pack.

[0120] The four typical working modes of the vehicle are as follows:

[0121] Working mode 1: heating only.

[0122] Scenario: In an extremely low temperature environment, when the first battery pack or the second battery pack needs to be heated and the second battery pack cannot be charged, only heating is performed. Figure 5 The A phase is shown.

[0123] Control method: Control the average value of the charging current to zero, and control the self-heating power by controlling the current frequency and amplitude.

[0124] Working mode 2: Charging and heating.

[0125] Scenario: When the ambient temperature is low, the second battery pack is allowed to charge, and the first battery pack or the second battery pack needs to be heated, charging and heating are performed simultaneously. Figure 5 B and C stages.

[0126] Control method: Control the average current to I1, and control the charging power and self-heating power by controlling the frequency and amplitude of the charging current.

[0127] Working mode three: stable charging.

[0128] Scenario: When the ambient temperature is not particularly low, the battery temperature is maintained at a certain target temperature and charging is performed. Figure 5 The D stage.

[0129] Temperature maintenance charging: The battery temperature is used as the control target, and the heating power is adjusted in combination with the charging power.

[0130] Working mode 4: charging only.

[0131] Scenario: When the battery temperature is high and the first battery pack and the second battery pack do not need to be heated, only the second battery pack is charged. Figure 5 E and F stages.

[0132] Control method: Control the output voltage of the first battery pack to be higher than that of the second battery pack, and only charge the second battery pack.

[0133] The charging and heating process of electric vehicles is described below. The whole vehicle charging waveform control method is as follows:

[0134] 1. Charging self-heating waveform control method:

[0135] Step 1: Step 1: Obtain the voltages of the first battery pack and the second battery pack. Assume that the voltage of the first battery pack is Ua=600V, the voltage of the second battery pack is Ub=320V, and the sum of the internal resistances of the first battery pack and the second battery pack is R.

[0136] Step 2: Control the IGBT duty cycle of the bridge arm converter by controlling the modulation waveform. Assume that the debugging waveform is y = ((A*sin(2*pi*f*t)+B)*R+Ub) / Ua. A is the target current amplitude of the current waveform, f is the current frequency, B is the target current average value, R is the sum of the internal resistance of the first battery pack and the second battery pack, Ua is the voltage of the first battery pack, Ub is the voltage of the second battery pack, and y is the target duty cycle.

[0137] Step 3: The output voltage of the first battery pack is 600*y, and the voltage difference between the first battery pack and the second battery pack is 600*y-320.

[0138] Step 4: The sum of the internal resistances of the first battery pack and the second battery pack is R, that is, the charging self-heating waveform is (600*y-320) / R. The voltage difference waveform and current waveform are as follows Fig.11 shown.

[0139] 2. Temperature detection: Real-time monitoring of the temperature of the inductor, motor, IGBT, and battery to ensure the safety of the charging and heating process.

[0140] The specific implementation case of the vehicle VTOV heating charging control method is mainly divided into two stages:

[0141] System design phase: The first battery pack is located in vehicle A, and the second battery pack is located in vehicle B.

[0142] When the whole vehicle VTOV is charging and heating, the temperature rise rate of the battery is related to the amplitude and frequency of the current waveform. In this implementation case, according to the battery characteristics combined with simulation and testing, the fixed self-heating current waveform frequency is preferably 800Hz. Then the heating power is controlled by controlling the amplitude of the self-heating current waveform.

[0143] The CAN communication information interaction design between the first battery pack of car A and car B. Car A and car B obtain information such as battery voltage, temperature, maximum charge and discharge current, maximum charge and discharge power, heating requirements, etc. of the two cars through CAN communication, and design DC charging protocol interaction messages.

[0144] Heating strategy 1: When the battery temperature is extremely low, such as -40°C, the BMS of at least one of Car A and Car B needs to be heated. At this time, the maximum charge and discharge currents of Car A and Car B are obtained through messages. The amplitude of self-heating can be controlled according to its maximum charge and discharge current, and self-heating can be performed with the maximum current it can withstand to maximize the self-heating power. The smaller value of the maximum charge and discharge current of Car A and Car B at this time is taken as the current amplitude of the VTOV self-heating of the whole vehicle. Since the amplitude of alternating current is positive and negative, it is twice the current value. This self-heating current amplitude is used as the control target, and the amplitude of the self-heating current of the whole vehicle is controlled through a PID closed loop to heat the battery of the whole vehicle with maximum power. The battery temperature and various parameters are monitored in real time to ensure the safety of the heating process. Figure 5 The A phase is shown.

[0145] Heating strategy 2: Under low battery temperature conditions, such as -20°C, the battery can be charged at a low power and still has a heating requirement. Take the minimum value m of the maximum charge and discharge current of Car A and Car B at this time, and obtain the maximum charging power n of Car A and Car B at this time (the charging power of the battery is different at different temperatures. At extremely low temperatures, the charging power is 0, which means that it cannot be charged, such as in stage A). The current value corresponding to the smaller value of the charge and discharge power is the self-heating current average value. The VTOV self-heating current amplitude of the whole vehicle is 2*(mn). The self-heating current amplitude and current average value are used as the control targets, and the amplitude and average value of the self-heating current of the whole vehicle are controlled through a PID closed loop. As the battery temperature increases, the battery charge and discharge power also changes, gradually increasing the self-heating current average value until the maximum charging power of the battery is reached. And monitor the battery temperature and various parameters in real time to ensure the safety of the heating process. Such as Figure 5 As shown in stage B, during this process, both the self-heating current amplitude and the current average value change.

[0146] Heating strategy three: When the battery temperature reaches the minimum value that can meet the maximum charging power, such as 15°C, and there is still a need for heating. At this time, the maximum charge and discharge current m and charge and discharge power n of vehicle A and vehicle B are obtained through the message. Take the smaller value m of the maximum charge and discharge current of vehicle A and vehicle B, and take the current value corresponding to the smaller value of the charge and discharge power of the two vehicles as the self-heating current average value n. The VTOV self-heating current amplitude of the whole vehicle is 2*(mn). The self-heating current amplitude and average value n are used as the control target, and the amplitude and average value of the self-heating current of the whole vehicle are controlled through the PID closed loop. And monitor the battery temperature and various parameters in real time to ensure the safety of the heating process. Such as Figure 5 The C stage is shown in Figure 2. During this process, the average current value n remains unchanged, but the value m changes.

[0147] Heating strategy 4: When the battery temperature reaches the optimal charging temperature, the battery needs to be heated due to the low ambient temperature. At this time, the current value corresponding to the maximum charging power is the average self-heating current. With the optimal battery temperature as the control target, the battery temperature is monitored in real time as the feedback value of the PID closed-loop control, and the self-heating current amplitude is controlled in real time to keep the battery at the optimal temperature. Figure 4 The D stage is shown.

[0148] Heating strategy 5: When the battery temperature is at the optimal charging temperature and heating is not required, the battery self-heating current amplitude gradually decreases until it reaches zero. Figure 5 As shown in the E phase of the charging current waveform, the charging current waveform is the same as the conventional charging waveform. Figure 5 In the F stage, charging is completed and the charging current gradually decreases to 0, completing the charging process.

[0149] Debug control phase:

[0150] First, car B needs to be charged.

[0151] Step 1: Connect the DC charging ports of car A and car B via a DC charging cable. Fig.12 As shown, the power battery in car A is equivalent to Fig.10 The first battery pack in the B car is equivalent to Fig.10 The second battery pack in the

[0152] Step 2: Car A and Car B exchange information through CAN communication. First, Car A obtains the battery voltage of Car B and compares it with the battery voltage of Car A. If the battery voltage of Car A is higher than that of Car B and the DC charging protocol interaction can be successfully completed, the next charging process will be carried out.

[0153] Step 3: Car A obtains information such as the battery temperature, maximum charging current, maximum discharging current, maximum charging power, and heating requirements of Car B.

[0154] Step 4: If the battery temperature of car B is too low and needs to be heated, so charging is not possible, then the duty cycle of the three-phase bridge arm of the bridge arm converter of car A is adjusted according to the battery temperature, maximum charging current, and maximum discharging current of cars A and B, and the waveform and amplitude of the charging current of car B are controlled, such as Figure 5 The waveform of phase A is shown in Figure 1. The battery of vehicle B is only heated.

[0155] Step 5: After a period of heating, the battery temperature of car B continues to rise and charging is allowed. Then, according to the battery temperature, maximum charging current and maximum discharging current of cars A and B, the three-phase bridge arm duty cycle of the bridge arm converter of car A is adjusted in real time to control the charging current and waveform of car B, such as Figure 5The charging power of vehicle B is continuously increased while the battery is heated.

[0156] Step 6: When the charging and discharging power of car A and car B reaches the maximum value, the three-phase bridge arm duty cycle of the bridge arm converter of car A is adjusted in real time according to the battery temperature, maximum charging current and maximum discharging current of car A and car B, and the charging current and waveform of car B are controlled, such as Figure 5 The charging power of vehicle B is constant, and the battery is heated at the same time.

[0157] Step 7: As the battery temperature of car B increases, the heating power demand decreases. Then, according to the battery temperature, maximum charging current, and maximum discharging current of cars A and B, the three-phase bridge arm duty cycle of the bridge arm converter of car A is adjusted in real time to control the charging current and waveform of car B, such as Figure 5 As shown in stage D, the charging power of vehicle B is constant, and the battery self-heating waveform amplitude decreases, stabilizing the battery temperature.

[0158] Step 8: When there is no heating demand for car A and car B, the three-phase bridge arm duty cycle of the bridge arm converter of car A is adjusted in real time according to the battery temperature, maximum charging current and maximum discharging current of car A and car B, and the charging current and waveform of car B are controlled, such as Figure 5 The amplitude of the self-heating waveform of vehicle B gradually decreases until it reaches zero, and the battery of vehicle B is charged with DC.

[0159] Step 9: As the battery capacity of vehicle B increases, the charging power gradually decreases, such as Figure 5 The E stage is shown.

[0160] Step 10: During the entire VTOV process, the status parameters of vehicle A and vehicle B are monitored in real time to ensure the safety of the VTOV process.

[0161] When the first battery pack heats and / or charges the second battery pack, the current flow of its current loop is as follows:

[0162] like Fig.13 As shown, when the lower bridge arm of the bridge arm converter is turned off and the upper bridge arm is turned on, the current starts from the positive electrode of the first battery pack 103, passes through the upper bridge arm of the bridge arm converter 101 (the first upper bridge diode VD1, the third upper bridge diode VD3, the fifth upper bridge diode VD5), and the motor winding to charge the second battery pack 104.

[0163] like Fig.14 As shown, when the lower bridge arm of the bridge arm converter 101 is turned on, the current flows out from the motor winding, passes through the lower bridge arm of the bridge arm converter 101 (the second lower bridge arm VT2, the fourth lower bridge arm VT4, and the sixth lower bridge arm VT6), and flows to the negative electrode of the battery pack 104, and the current continues to increase.

[0164] When the second battery pack heats and / or charges the first battery pack, the current flow of its current loop is as follows:

[0165] like Fig.15 As shown, when the lower bridge arm of the bridge arm converter 101 is turned on, the current flows out from the negative electrode of the second battery pack 103, passes through the motor winding, the lower bridge arm of the bridge arm converter 101 (the second lower bridge diode VD2, the fourth lower bridge diode VD4, the sixth lower bridge diode VD6), and flows back to the positive electrode of the second battery pack.

[0166] like Fig.16 As shown, the lower bridge arm of the control arm converter 101 is disconnected and the upper bridge arm is closed. When the upper bridge arm of the bridge arm converter 101 is turned on, the current starts from the positive electrode of the second battery pack 104 and the motor winding, passes through the motor winding and the upper bridge arm of the bridge arm converter 101 (the first upper bridge arm VT1, the third upper bridge arm VT3, and the fifth upper bridge arm VT5) to charge the positive electrode of the first battery pack 103.

[0167] Compared with the existing technology, the circuit structure and control method have changed. Since the three-phase bridge arm control is exactly the same, the current vector inside the motor is zero and there is no torque pulsation. In addition, through the high switching frequency control of the IGBT of the bridge arm converter, the current waveform can be improved to meet the system's requirements for current amplitude, frequency and waveform. Finally, since the capacitance of the first capacitor C1 is relatively small, the influence of the first capacitor C1 during the energy interaction between the power battery of vehicle A and the power battery of vehicle A is effectively alleviated.

[0168] 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. An energy conversion device, characterized in that: The energy conversion device comprises: A bridge arm converter, wherein the first ends of the bridge arms of the bridge arm converter are connected together to form a first bus terminal, and the second ends of the bridge arms of the bridge arm converter are connected together to form a second bus terminal; A first battery pack, wherein a first polarity end of the first battery pack is connected to the first bus terminal, and a second polarity end of the first battery pack is connected to the second bus terminal; Second battery pack; A motor, wherein a first end of a motor winding of the motor is connected to the bridge arm converter, a second end of the motor winding is connected together to form a neutral point and is connected to a first polarity end of a second battery pack, and a second polarity end of the second battery pack is connected to a second bus terminal of the bridge arm converter; a controller, the controller being used to obtain battery parameters of the first battery pack and battery parameters of the second battery pack, and control the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, so as to achieve heating and / or charging of the first battery pack, or heating and / or charging of the second battery pack; The acquiring the battery parameters of the first battery pack and the battery parameters of the second battery pack includes: Acquire a maximum discharge current of the first battery pack, and acquire a temperature and a maximum discharge current of the second battery pack; The controlling the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the second battery pack includes: When the temperature of the second battery pack is lower than a first preset temperature value, obtaining a target current amplitude of a target current waveform of the current loop according to a maximum charge and discharge current of the first battery pack and a maximum charge and discharge current of the second battery pack; Acquire a target duty cycle according to the target current amplitude and the target current waveform function; The bridge arm converter is controlled according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, so as to heat the second battery pack.

2. The energy conversion device according to claim 1, characterized in that: Also includes: An inductor is connected between a neutral point of the motor winding and the second battery pack.

3. A control method for the energy conversion device according to claim 1, characterized in that: The control method comprises: Acquire battery parameters of the first battery pack and battery parameters of the second battery pack; The bridge arm converter is controlled according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the first battery pack, or heating and / or charging of the second battery pack; the obtaining of the battery parameters of the first battery pack and the battery parameters of the second battery pack includes: Acquire a maximum discharge current of the first battery pack, and acquire a temperature and a maximum discharge current of the second battery pack; The controlling the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the second battery pack includes: When the temperature of the second battery pack is lower than a first preset temperature value, obtaining a target current amplitude of a target current waveform of the current loop according to a maximum charge and discharge current of the first battery pack and a maximum charge and discharge current of the second battery pack; Acquire a target duty cycle according to the target current amplitude and the target current waveform function; The bridge arm converter is controlled according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, so as to heat the second battery pack.

4. The control method according to claim 3, characterized in that: The step of obtaining a target current amplitude of a target current waveform of the current loop according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack includes: The smaller current value of the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack is obtained, and the target current amplitude of the target current waveform of the current loop is obtained by doubling the smaller current value.

5. The control method according to claim 3, characterized in that: The acquiring of the battery parameters of the first battery pack and the battery parameters of the second battery pack further includes: Obtaining a maximum charging power of the first battery pack, and obtaining a maximum charging power of the second battery pack; The method further comprises: controlling the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the second battery pack; When the temperature of the second battery pack is not lower than a first preset temperature value and lower than a second preset temperature, a target current average value of the target current waveform of the current loop is obtained according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack, and a target current amplitude of the target current waveform of the current loop is obtained according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack; Obtaining a target duty cycle according to the target current average value, the target current amplitude, and a target current waveform function; The bridge arm converter is controlled according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, the second battery pack is charged with the target current average value and the second battery pack is heated with the target current amplitude.

6. The control method according to claim 3, characterized in that: The acquiring of the battery parameters of the first battery pack and the battery parameters of the second battery pack further includes: Obtaining a maximum charging power of the first battery pack, and obtaining a maximum charging power of the second battery pack; The method controls the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the second battery pack, and further includes: When the temperature of the second battery pack is not lower than a second preset temperature value and lower than a third preset temperature, a target current average value of the target current waveform of the current loop is obtained according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack, and a target current amplitude of the target current waveform of the current loop is obtained according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack; Obtaining a target duty cycle according to the target current average value, the target current amplitude, and a target current waveform function; The bridge arm converter is controlled according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, the second battery pack is charged with the target current average value and the second battery pack is heated with the target current amplitude.

7. The control method according to claim 5 or 6, characterized in that: The step of obtaining a target current average value of a target current waveform of the current loop according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack includes: Obtaining a target current average value according to a smaller maximum charging power of the first battery pack and a maximum charging power of the second battery pack; The step of obtaining a target current amplitude of a target current waveform of the current loop according to the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack includes: The smaller current value of the maximum charge and discharge current of the first battery pack and the maximum charge and discharge current of the second battery pack is obtained, and the target current amplitude of the target current waveform of the current loop is obtained by performing a difference operation and then doubling operation on the smaller current value and the target current average value.

8. The control method according to claim 3, characterized in that: The acquiring of the battery parameters of the first battery pack and the battery parameters of the second battery pack further includes: Obtaining a maximum charging power of the first battery pack, and obtaining a maximum charging power of the second battery pack; The method controls the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the second battery pack, and further includes: When the temperature of the second battery pack reaches an optimal charging temperature and the ambient temperature is lower than a fourth preset temperature, obtaining a target current average value of the target current waveform of the current loop according to the maximum charging power of the first battery pack and the maximum charging power of the second battery pack; When it is detected that the temperature of the second battery pack is lower than the optimal charging temperature, the target current amplitude is obtained according to the corresponding relationship between the temperature and the target current amplitude, and the target duty cycle is obtained according to the target current average value, the target current amplitude and the target current waveform function; The bridge arm converter is controlled according to the target duty cycle so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops, so as to heat and charge the second battery pack while maintaining the temperature of the second battery pack at an optimal charging temperature.

9. The control method according to claim 3, characterized in that: The method controls the bridge arm converter according to the battery parameters of the first battery pack and the battery parameters of the second battery pack, so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to achieve heating and / or charging of the second battery pack, and further includes: When the temperature of the second battery pack reaches the optimal charging temperature and does not need to be heated, the target current amplitude is controlled to gradually decrease so that the duty cycle of the bridge arm converter is a fixed value; Controlling the bridge arm converter according to the duty cycle of the bridge arm converter so that the first battery pack, the bridge arm converter, the motor winding and the second battery pack form different current loops to charge the second battery pack; When it is detected that the second battery pack is in a fully charged state, the duty cycle is reduced to 0.

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