Energy conversion device and vehicle

Abstract

This invention discloses an energy conversion device and a vehicle, comprising: a battery pack; an inverter unit including Y-phase bridge arms, the first end of each phase bridge arm being connected to the positive terminal of a first battery pack, and the second end of each phase bridge arm being connected to the negative terminal of a second battery pack; a motor, the third end of each phase bridge arm being connected to the first end of a phase coil of a corresponding set of windings, the second ends of the multi-phase coils of at least one set of windings in X sets of windings being shared and led out with an N line, and the second ends of the multi-phase coils of the remaining sets of windings in X sets of windings being shared, wherein the number of phases of the bridge arm is equal to the number of phases of the coil, X≥2; and a first switching unit, the first end of the first switching unit being connected to the N line, and the second end of the first switching unit being connected to the midpoint of the first battery pack and the second battery pack. Using this energy conversion device can fully utilize the multiple sets of windings of the motor to meet the functional requirements of the vehicle under different states, improve energy utilization efficiency, and enhance system compatibility.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an energy conversion device and a vehicle. Background Technology

[0002] With the development and rapid popularization of electric vehicles, numerous challenges have emerged. Lithium-ion batteries are widely used, and due to their inherent characteristics, charging and discharging at suitable temperatures can improve their efficiency and extend their lifespan. However, at low temperatures, their charging and discharging capabilities decrease significantly, impacting the practicality of electric vehicles in cold regions. Especially for electric vehicles, winter often brings slow charging speeds, reduced range, and reluctance to use air conditioning or heating. "Low-temperature anxiety" has become a major pain point affecting user experience in the marketization of electric vehicles. Therefore, improving the performance of lithium-ion batteries at low temperatures is a crucial issue that urgently needs to be addressed. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one object of the present invention is to provide an energy conversion device that can fully utilize multiple windings of a motor to meet the functional requirements of a vehicle under different conditions, improve energy utilization efficiency, and enhance system compatibility.

[0004] The second objective of this invention is to provide a vehicle.

[0005] To address the aforementioned problems, a first aspect of the present invention provides an energy conversion device, comprising: a battery pack, the battery pack including two first battery packs and a second battery pack connected in series; an inverter unit, the inverter unit including Y-phase bridge arms, each phase bridge arm including an upper bridge arm and a lower bridge arm, a first end of each phase bridge arm connected to the positive terminal of the first battery pack, and a second end of each phase bridge arm connected to the negative terminal of the second battery pack; a motor, the motor including X sets of windings, the third end of each phase bridge arm connected to the first end of a phase coil of a corresponding set of windings, the second ends of the multi-phase coils of at least one set of windings in the X sets of windings being connected together and led out to an N line, the second ends of the multi-phase coils of the remaining sets of windings in the X sets of windings being connected together, wherein the number of phases of the bridge arm is equal to the number of phases of the coil, X≥2; and a first switching unit, the first end of the first switching unit being connected to the N line, and the second end of the first switching unit being connected to the midpoint of the first battery pack and the second battery pack.

[0006] According to the energy conversion device of the present invention, when the first switching unit is turned on, the motor output energy is controlled by adjusting the duty cycle corresponding to each phase bridge arm in the inverter unit. Based on the motor setting multiple sets of windings, the energy generated by the motor can be used to cause the first battery pack and the second battery pack in the battery pack to alternately charge and discharge to generate heat, achieving the effect of self-heating inside the battery pack. At the same time, the energy generated by the motor can be used to meet the functional requirements of the vehicle in different states such as driving, charging or discharging. Thus, while solving the problem of the battery being unable to be used in low-temperature environments, the energy utilization efficiency is maximized and the system compatibility is improved.

[0007] To address the aforementioned problems, a second aspect of the present invention provides a vehicle including the energy conversion device described in the above embodiments.

[0008] According to the vehicle of the present invention, by employing the energy conversion device of the above embodiment, the multiple windings of the motor can be fully utilized to meet the functional requirements of the vehicle under different states, improve energy utilization efficiency, and enhance system compatibility.

[0009] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0010] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0011] Figure 1 This is a circuit diagram of an energy conversion device according to an embodiment of the present invention;

[0012] Figure 2 This is a torque curve diagram according to an embodiment of the present invention;

[0013] Figure 3 This is a circuit connection diagram of an energy conversion device using a six-phase motor according to another embodiment of the present invention;

[0014] Figure 4 This is a control schematic diagram of an energy conversion device according to an embodiment of the present invention;

[0015] Figure 5 This is a structural block diagram of a vehicle according to an embodiment of the present invention.

[0016] Figure label:

[0017] Vehicle 100; Energy conversion device 10;

[0018] Battery pack 11; motor 1; inverter unit 2; first switch unit 3. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present invention are described in detail below.

[0020] Lithium-ion batteries are sensitive to low temperatures. At low temperatures, the internal resistance of lithium ions increases sharply, which greatly limits the discharge capacity and charge / discharge performance. This results in insufficient power performance and a significantly shortened driving range for electric vehicles in low-temperature environments. Moreover, batteries can hardly be charged below -20°C. If forced to charge, it can easily cause internal short circuits and create safety hazards.

[0021] In related technologies, to address the low-temperature use of lithium-ion batteries, self-heating during charging and discharging can be utilized to improve self-heating safety and efficiency. Specifically, the battery's AC self-heating circuit consists of a first energy storage device, a second energy storage device, a power electronic switch, a motor controller, and a motor. The motor's neutral point is electrically connected to the equipotential point between the first and second energy storage devices via the power electronic switch. The power electronic switch is connected in series between the motor's neutral point and the equipotential point. However, in this scheme, the power electronic switch is controlled by the self-heating control system, and it only closes when the power battery needs self-heating in a low-temperature parking environment; otherwise, it remains open. In other words, the above scheme only enables self-heating when the battery is parked, and cannot achieve self-heating during DC charging or while driving. This results in a limited functional scope, narrow environmental adaptability, low system component utilization, low system integration, and an inability to maximize system efficiency and battery performance.

[0022] To address the aforementioned problems, the first aspect of this invention proposes an energy conversion device. This energy conversion device can fully utilize the multiple windings of the motor to meet the functional requirements of the vehicle under different conditions, thereby improving energy utilization efficiency and enhancing system compatibility.

[0023] The following is for reference. Figure 1 The energy conversion device described in the embodiments of the present invention, such as Figure 1 As shown, the energy conversion device 10 includes a battery pack 11, a motor 1, an inverter unit 2, and a first switching unit 3.

[0024] The battery pack 11 includes two battery packs E1 and E2 connected in series. The motor 1 includes X sets of windings. The first end of the first switching unit 3 is connected to the first battery pack E1. The inverter unit 2 includes Y-phase bridge arms, each phase bridge arm including an upper bridge arm and a lower bridge arm. The first end of each phase bridge arm is connected to the positive terminal of the first battery pack E1, and the second end of each phase bridge arm is connected to the negative terminal of the second battery pack E2. The motor 1 includes X sets of windings. The third end of each phase bridge arm is connected to the first end of a phase coil of the corresponding set of windings. The second ends of the multi-phase coils of at least one set of windings in the X sets of windings are connected together and led out to the N line. The second ends of the multi-phase coils of the remaining sets of windings in the X sets of windings are connected together. The number of phases of the bridge arm is equal to the number of phases of the coil, and X≥2. The first end of the first switching unit 3 is connected to the N line, and the second end of the first switching unit 3 is connected to the midpoint of the first battery pack E1 and the second battery pack E2.

[0025] Specifically, based on the above connection configuration, the self-heating circuit formed by the first battery pack E1 or the second battery pack E2, the inverter unit 2, and the motor 1 is turned on or off by controlling the switching state of the first switch unit 3. That is, when the first switch unit 3 is in the closed state, the self-heating circuit is turned on. Then, by adjusting the duty cycle of each phase arm in the inverter unit 2, the upper and lower arms of each phase arm are controlled to work alternately, thereby driving the motor 1. Furthermore, based on the multiple winding configuration of the motor 1, the energy generated by the motor allows for mutual charging and discharging between the first battery pack E1 and the second battery pack E2. During charging and discharging, the current flowing through the battery's internal resistance heats up, thus self-heating the battery pack 11 and achieving rapid battery temperature rise. This solves the problem of reduced battery pack charging and discharging capacity at low temperatures, improves the lifespan of the battery pack 11, and simultaneously meets the functional requirements of the vehicle in different states such as driving, charging, or discharging. Therefore, while solving the problem of battery inoperability in low-temperature environments, energy utilization efficiency is maximized, and system compatibility is improved.

[0026] In this embodiment, motor 1 can be a permanent magnet synchronous motor or an asynchronous motor. The number of phases of the coils in motor 1 can be three-phase, double three-phase, five-phase, six-phase, nine-phase, etc., and there is no limitation thereto. In the embodiment, refer to... Figure 1 As shown, motor 1 includes X sets of windings, where X ≥ 2 and X is an integer, and the number of phases of the Xth set of windings is m. X Each phase winding in the Xth set of windings includes n phases. X Each coil branch has n phase windings. X The first ends of each coil branch are connected to form a phase endpoint, and the n-th phase winding of each phase winding in the Xth set of windings... X The second end of one of the coil branches in each coil branch is also connected to n in other phase windings. xThe second end of one of the coil branches is connected to form n. X There are n connection points, where n X ≥1,m X ≥2, and n X m X The value is an integer. Based on this, X sets of windings form a total of... One connection point, Connecting points form T neutral points, and from these T neutral points, x neutral lines are drawn, where the value of T ranges from 1 to 1. ≥1, the range of x is T≥x≥1, and T and x are both integers;

[0027] Furthermore, the inverter unit includes a Y-group P N Bridge arm, a set of P N At least one bridge arm has its midpoint connected to one phase endpoint of X sets of windings. No two phase endpoints are connected to the same bridge arm. Among these, P... N ≥m X , Y≥X, and Y, P N All are integers.

[0028] It is understandable that when the vehicle is in a power-off state, that is, when the vehicle is not charging, not driving, and the system is powered off, all switches in the energy conversion device 10 are in the off state. This can reduce energy loss and effectively avoid the danger of electric shock, thus improving vehicle safety.

[0029] According to an embodiment of the present invention, the energy conversion device 10, when the first switching unit is turned on, controls the motor output energy by adjusting the duty cycle corresponding to each phase bridge arm in the inverter unit. Based on the motor's configuration of multiple windings, the energy generated by the motor can be used to alternately charge and discharge the first and second battery packs within the battery pack, generating heat and achieving a self-heating effect within the battery pack. Simultaneously, the energy generated by the motor can also be used to meet the functional requirements of the vehicle in different states, such as driving, charging, or discharging. Therefore, while solving the problem of batteries being unusable in low-temperature environments, this maximizes energy utilization efficiency and improves system compatibility.

[0030] In some embodiments, such as Figure 1 As shown, motor 1 includes two sets of windings, each set of windings includes two pairs of poles, and each pair of poles includes three coil branches; wherein, in the same set of windings, the first ends of the coil branches of the same phase in the three coil branches of the two pairs of poles are connected together and connected to the midpoint of the corresponding bridge arm; the second ends of the three coil branches of each pair of poles are connected together to form a neutral point, and all the neutral points of the two sets of windings are connected together and the N line is led out.

[0031] Specifically, refer to Figure 1The diagram shows the circuit connection of a six-phase motor. The two battery packs of battery pack 11, namely the first battery pack E1 and the second battery pack E2, are first connected in series and then connected to the DC bus of inverter unit 2 through switches K1 and K2. Inverter unit 2 includes six phase bridge arms, namely: phase A bridge arm, phase B bridge arm, phase C bridge arm, phase U bridge arm, phase V bridge arm, and phase W bridge arm. The three coil branches of one pair of poles of one set of windings of motor 1 are: phase A1 coil branch, phase B1 coil branch, and phase C1 coil branch, and the three coil branches of the other pair of poles are: phase A2 coil branch, phase B2 coil branch, and phase C2 coil branch. The three coil branches of one pair of poles of the other set of windings of motor 1 are: phase U1 coil branch, phase V1 coil branch, and phase W1 coil branch, and the three coil branches of the other pair of poles are: phase U2 coil branch, phase V2 coil branch, and phase W2 coil branch. Specifically, the first end of the A1 phase coil branch is connected to the first end of the A2 phase coil branch and to the midpoint of the A phase bridge arm; the first end of the B1 phase coil branch is connected to the first end of the B2 phase coil branch and to the midpoint of the B phase bridge arm; the first end of the C1 phase coil branch is connected to the first end of the C2 phase coil branch and to the midpoint of the C phase bridge arm, and so on, so that the midpoint of each phase bridge arm is connected to the first end of one phase coil of the corresponding winding set; the second end of the A1 phase coil branch, the second end of the B1 phase coil branch, and the second end of the C1 phase coil branch... The terminals of the A2, B2, and C2 phase coil branches are connected to form a neutral point n1. The second terminals of the U1, V1, and W1 phase coil branches are connected to form a neutral point n3. The second terminals of the U2, V2, and W2 phase coil branches are connected to form a neutral point n4. Neutral points n1, n2, n3, and n4 are connected together and a neutral line (N) is drawn out. The N line from motor 1 is connected to one end of the first switching unit 3, i.e., switch K3. The other end of the first switching unit 3 is connected to the midpoint (equipotential point) between the first battery pack E1 and the second battery pack E2. The bus capacitor C1 is connected in parallel to the positive and negative busbars of inverter unit 2. Therefore, based on the above connection configuration, the multiple windings of the motor can be fully utilized to meet the functional requirements of the vehicle under different conditions, improving energy utilization efficiency and enhancing system compatibility.

[0032] In some embodiments, the energy conversion device 10 further includes a controller connected to the inverter unit 2.

[0033] Specifically, based on Figure 1In the connection shown, the controller is configured as follows: In the first state, it controls the first switching unit 3 to be turned on, and obtains the differential mode voltage value corresponding to each phase arm based on the phase current value, rotor electrical angle, D-axis target current value, and Q-axis target current value of each phase arm; it obtains the common mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, and self-heating current frequency of each phase arm; it obtains the duty cycle corresponding to each group of arms based on the differential mode voltage value and the common mode voltage value; and it controls the upper and lower arms of each phase arm to work alternately according to the duty cycle corresponding to each phase arm, so as to achieve the coordination of motor drive and battery self-heating. Thus, by controlling the operation of motor 1 through the above control method, the battery can be self-heated even when the vehicle is in motion, making full use of the multiple windings of the motor to achieve coordinated control of vehicle operation and battery self-heating, improving energy utilization efficiency and enhancing system compatibility.

[0034] The duty cycle refers to the duty cycle of the upper bridge arm. The duty cycles of the upper and lower bridge arms are complementary, and a certain dead time is reserved according to the characteristics of the power devices. Specifically, the differential-mode voltage value and the common-mode voltage value Un corresponding to each phase bridge arm are calculated to obtain the phase voltage value corresponding to each phase bridge arm. The phase voltage values ​​of each phase bridge arm in the Y phase are modulated with the bus voltage value and the carrier wave to obtain the PWM duty cycle corresponding to each phase bridge arm. Through the modulation effect of the bridge arms, the required motor phase current values ​​are obtained.

[0035] In some embodiments, the duty cycle corresponding to each phase arm can also be obtained by using SVPWM modulation based on Uα and Uβ.

[0036] Specifically, when the vehicle is in motion, the torque and speed values ​​of motor 1 are collected in real time, along with a pre-calibrated torque curve within the vehicle, such as... Figure 2As shown, the horizontal axis represents the D-axis current value, the vertical axis represents the Q-axis current value, the MTPA curve is the 0-HFDA curve in the torque curve diagram, and the MTPV curve is the BEGIC curve in the torque curve diagram. Based on the torque curve, the target current values ​​id* on the D-axis and iq* on the Q-axis are obtained from the motor torque value Te, the motor speed value ωe, and the bus voltage value Udc by looking up a table or by a combination of looking up a table and interpolation or by piecewise linear fitting. Then, the current vector on the dq axis is controlled in a closed loop according to the motor's vector control method to calculate the duty cycle corresponding to each bridge arm and complete the self-heating of the battery pack 11. Therefore, by combining the bus voltage, motor torque, and motor speed to obtain the target current values ​​for the D-axis and Q-axis, it is possible to support battery self-heating control when the vehicle is parked, such as when the user is warming up the vehicle before a trip or waiting for someone, thus solving the problem of limited battery discharge performance caused by low battery pack temperature when the vehicle is parked. At the same time, it is also possible to effectively solve the problem of limited battery discharge performance caused by low battery pack temperature during driving without affecting the normal driving function of the vehicle.

[0037] It should be noted that when the vehicle is parked, the motor is not working, so the torque and speed of motor 1 are both 0.

[0038] In some embodiments, the vehicle 100 also includes an air conditioning unit. The following is a detailed description of the battery self-heating coolant circuit.

[0039] In the vehicle, the cooling circuits of the battery system and the air conditioning system are connected via valve bodies, pipes, and heat exchange plates. Switching valves allows the coolant heated by the air conditioning system via the heat exchange plates to flow to the battery. Similarly, the heat generated by the electric drive system's motor stator and electronically controlled water-cooled circuit flows through valve bodies and pipes to the battery via the coolant heated by the electric drive system. If an oil-cooled motor is used, the electric drive system's motor rotor oil-cooled circuit is connected via valve bodies, pipes, and heat exchange plates, transferring heat from the motor rotor to the battery coolant circuit. In low-temperature environments, when the battery is self-heating, it is necessary to wait for the electric drive system to generate sufficient heat to heat the coolant before opening the valves to transfer the heat generated by the electric drive system to the battery thermal circulation system, preventing the heat generated during initial self-heating from being carried away.

[0040] The controller acquires the torque and speed values ​​of the vehicle's motors, as well as the target heating power value of the air conditioning system. Based on the bus voltage, motor torque, speed, and target heating power value, it selects a speed that increases or decreases on the motor's constant torque curve, ensuring constant torque and overall vehicle power performance. This increases or decreases the combined current amplitude of the D-axis and Q-axis current values ​​to obtain the target D-axis and Q-axis current values. By obtaining these target D-axis and Q-axis current values, reactive power can be increased or decreased to fully utilize the heat generated by motor 1 and inverter unit 2. This allows the air conditioning system to start and operate normally, heating the passenger compartment to meet user temperature requirements, and also provides heat for battery self-heating. This achieves coordinated control of vehicle operation, battery self-heating, and inefficient heating, effectively solving the problem of limited battery discharge performance due to low battery temperature during driving without affecting normal vehicle operation. The target heating power value can be understood as the heating power used to achieve the required temperature for passengers inside the vehicle.

[0041] Furthermore, it is understandable that when the vehicle is parked, motor 1 is not in operation, and the torque and speed of motor 1 are both zero. Therefore, based on the bus voltage, motor torque, motor speed, and target heating power, the motor speed is adjusted by sliding up or down the constant torque curve of the motor according to the target heating power. This increases or decreases the combined current amplitude of the D-axis and Q-axis current values ​​to obtain the target D-axis and Q-axis current values. This allows the heat generated by the electric drive system to be used to heat both the battery and the passenger compartment, achieving coordinated control of battery self-heating and inefficient heating. This effectively solves the problem of limited battery discharge performance caused by low battery pack temperature when the vehicle is parked.

[0042] In some embodiments, the energy conversion device 10 further includes a controller connected to the inverter unit 2.

[0043] Specifically, based on Figure 1In the connection shown, the controller is configured as follows: In the second state, it controls the first switching unit to conduct and obtains the differential-mode voltage value corresponding to each phase arm based on the phase current value, rotor electrical angle, D-axis target current value, and Q-axis target current value of each phase arm; it obtains the common-mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating balancing current of each phase arm; it obtains the duty cycle corresponding to each group of arms based on the differential-mode voltage value and the common-mode voltage value; and it controls the upper and lower arms of each phase arm to work alternately based on the duty cycle corresponding to each phase arm, so as to achieve the coordination of motor drive, battery pack self-heating, and battery pack balancing. Thus, by controlling the motor operation through the above control method, the vehicle can achieve both battery self-heating and battery pack balancing while driving, fully utilizing the multiple windings of the motor to achieve coordinated control of vehicle driving, battery balancing, and battery self-heating, improving energy utilization efficiency and enhancing system compatibility.

[0044] In some embodiments, the energy conversion device 10 further includes a controller connected to the inverter unit 2.

[0045] Specifically, based on Figure 1 In the connection method shown, the controller is configured as follows: In the third state, it controls the first switching unit to conduct, and obtains the common-mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating balancing current on each phase arm; it obtains the duty cycle corresponding to each group of arms based on the common-mode voltage value; and it controls the upper and lower arms of each phase arm to work alternately based on the duty cycle corresponding to each phase arm, so as to achieve the synergy of battery pack self-heating and battery pack balancing. Thus, by controlling the motor operation through the above control method, the energy generated by the motor can achieve both battery self-heating and battery pack balancing, thereby fully utilizing the multiple windings of the motor to achieve synergistic control of battery balancing and battery self-heating, improving energy utilization efficiency and enhancing system compatibility.

[0046] In some embodiments, the energy conversion device 10 further includes a DC charging / discharging port and a controller.

[0047] The positive terminal of the DC charging / discharging port is connected to the first bus terminal, and the negative terminal of the DC charging / discharging port is connected to the second bus terminal. The first end of the Y-phase bridge arm is connected to form the first bus terminal, and the second end of the Y-phase bridge arm is connected to form the second bus terminal. The controller is connected to the inverter unit 2.

[0048] Specifically, based on Figure 1The connection method shown indicates that the controller is configured to: in the fourth state, control the first switching unit to conduct, and obtain the common-mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, and self-heating current frequency on each phase arm; obtain the duty cycle corresponding to each group of arms based on the common-mode voltage value; and control the upper and lower arms of each phase arm to work alternately based on the duty cycle corresponding to each phase arm, so as to achieve the synergy of DC charging / discharging and battery pack self-heating. Therefore, through the connection configuration of the DC charging / discharging port and inverter unit 2, the charging or discharging function of the battery pack is effectively combined with the self-heating function of the battery pack, thus facilitating simultaneous battery self-heating even when the vehicle is charging or discharging, thereby effectively improving the charging / discharging capacity and efficiency of the battery pack.

[0049] In some embodiments, the vehicle 100 further includes an air conditioning unit. Based on the aforementioned coordinated control of vehicle charging / discharging and battery self-heating, the controller is specifically configured to obtain the target heating power value of the air conditioning unit and, based on the target heating power value, obtain the target current value on the D-axis and the target current value on the Q-axis. Thus, by using the target heating power value to obtain the target current value on the D-axis and the target current value on the Q-axis, the heat generated by the electric drive system can be used to heat both the battery and the passenger compartment, achieving coordinated control of charging / discharging, battery self-heating, and inefficient heating. This effectively solves the problem of limited battery discharge performance due to low battery pack temperature during charging / discharging. It is understood that the vehicle should be in a parked state during charging. Therefore, when obtaining the target current value on the D-axis and the target current value on the Q-axis using the torque curve, the motor torque and motor speed are both 0. Based on the target heating power value, the motor's constant torque curve is adjusted by sliding up or down the lookup speed, thereby increasing or decreasing the combined current amplitude of the D-axis and Q-axis current values ​​to determine the target current value on the D-axis and the target current value on the Q-axis.

[0050] In some embodiments, such as Figure 1 As shown in Figure 3, the energy conversion device 10 also includes a fourth switching unit K4 and a fifth switching unit K5.

[0051] In this configuration, the first terminal of the fourth switch unit K4 is connected to the positive terminal of the DC charging / discharging port, and the second terminal of the fourth switch unit K4 is connected to the second terminal of switch K1. The first terminal of the fifth switch unit K5 is connected to the negative terminal of the DC charging / discharging port, and the second terminal of the fifth switch unit K5 is connected to the second terminal of switch K2. The controller is connected to the fourth switch unit K4 and the fifth switch unit K5 and is used to control the switching states of the fourth switch unit K4 and the fifth switch unit K5. Therefore, through the connection configuration of the fourth switch unit K4 and the fifth switch unit K5, the charging or discharging function of the battery is effectively combined with the self-heating function of the battery pack. This allows for simultaneous battery self-heating while the vehicle is charging or discharging, thereby effectively improving the charging and discharging capacity and efficiency of the battery pack.

[0052] In some embodiments, after receiving a charging command or a discharging command, the controller controls both the fourth and fifth switching units to be in a closed state. For example, refer to... Figure 1 As shown in Figure 3, when the vehicle is DC charged in a low-temperature environment, the controller will control K1, K2, K3, K4, and K5 to close, forming a charging circuit between the charging / discharging interface, K1, K2, K4, K5, and battery pack 11. The charging current from the external DC charging pile will directly charge battery pack 11 through the charging / discharging interface. At the same time, a self-heating circuit will be formed between the first battery pack E1 or the second battery pack E2, K1, K2, K3, inverter unit 2, and motor 1. This achieves coordinated control of vehicle charging and battery self-heating, effectively solving the problems of low battery pack temperature causing charging to be prohibited, low charging current, and long charging time during charging. Alternatively, when the vehicle is in a low-temperature environment and is undergoing DC discharge, the controller will close K1, K2, K3, K4, and K5, forming a discharge circuit between the charging / discharging interface, K1, K2, K4, K5, and battery pack 11. The output current of battery pack 11 directly charges the external load through the charging / discharging interface. At the same time, a self-heating circuit is formed between the first battery pack E1 or the second battery pack E2, K1, K2, K3, inverter unit 2, and motor 1. This achieves coordinated control of vehicle discharge and battery self-heating, effectively solving the problems of low battery pack temperature causing discharging restrictions, low discharge current, and reduced charge during discharge.

[0053] In some embodiments, based on Figure 1In the connection shown, the controller is further configured to: in the fifth state, control the first switching unit to conduct, and obtain the common-mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating balancing current on each phase arm; obtain the duty cycle corresponding to each group of arms based on the common-mode voltage value; and control the upper and lower arms of each phase arm to work alternately based on the duty cycle corresponding to each phase arm, so as to achieve the coordination of DC charging and discharging, battery pack self-heating, and battery pack balancing. Therefore, based on the connection between the DC charging / discharging port and the inverter unit 2, the motor 1 is controlled to operate through the above control method, enabling the vehicle to achieve both battery self-heating and battery pack balancing during charging and discharging. This fully utilizes the multiple windings of the motor to achieve coordinated control of vehicle charging and discharging, battery balancing, and battery self-heating, improving energy utilization efficiency, enhancing system compatibility, effectively avoiding overcharging and over-discharging of the battery pack, and extending the battery pack's lifespan.

[0054] In some embodiments, such as Figure 3 As shown, motor 1 includes a first set of windings and a second set of windings. The first set of windings includes two pole pairs, each pole pair including three coil branches. The first ends of the coil branches of the same phase in the three coil branches of the two pole pairs of the first set of windings are connected together and connected to the midpoint of the corresponding phase bridge arm. The second ends of the three coil branches of the two pole pairs of the first set of windings are connected together and led out as N line.

[0055] Specifically, refer to Figure 3The diagram shows the circuit connection of a six-phase motor. The two battery packs of battery pack 11, namely the first battery pack E1 and the second battery pack E2, are first connected in series and then connected to the DC bus of inverter unit 2 through switches K1 and K2. Inverter unit 2 includes six phase bridge arms, namely: phase A bridge arm, phase B bridge arm, phase C bridge arm, phase U bridge arm, phase V bridge arm, and phase W bridge arm. The three coil branches of one pole of the first set of windings of motor 1 are: phase A1 coil branch, phase B1 coil branch, and phase C1 coil branch, and the three coil branches of the other pole are: phase A2 coil branch, phase B2 coil branch, and phase C2 coil branch. The three coil branches of one pole of the second set of windings of motor 1 are: phase U1 coil branch, phase V1 coil branch, and phase W1 coil branch, and the three coil branches of the other pole are: phase U2 coil branch, phase V2 coil branch, and phase W2 coil branch. Specifically, the first end of phase A1 coil branch is connected to the first end of phase A2 coil branch and to the midpoint of phase A bridge arm; the first end of phase B1 coil branch is connected to the first end of phase B2 coil branch and to the midpoint of phase B bridge arm; the first end of phase C1 coil branch is connected to the first end of phase C2 coil branch and to the midpoint of phase C bridge arm, and so on, so that the midpoint of each phase bridge arm is connected to the first end of one phase coil of the corresponding winding set; the second ends of phase A1 coil branch, phase B1 coil branch, and phase C1 coil branch are connected to the first end of phase C coil branch. A neutral point n1 is formed by connecting the two ends of the A2 phase coil branch, the B2 phase coil branch, and the C2 phase coil branch. A neutral point n2 is formed by connecting the two ends of the U1 phase coil branch, the V1 phase coil branch, and the W1 phase coil branch. A neutral point n3 is formed by connecting the two ends of the U2 phase coil branch, the V2 phase coil branch, and the W2 phase coil branch. A neutral point n4 is formed by connecting the two ends of the U2 phase coil branch, the V2 phase coil branch, and the W2 phase coil branch. Neutral points n1 and n2 are connected together, and neutral points n3 and n4 are connected together and lead out the N line. The N line from motor 1 is connected to one end of the first switching unit 3, i.e., switch K3. The other end of the first switching unit 3 is connected to the midpoint between the first battery pack E1 and the second battery pack E2, i.e., the equipotential point. The bus capacitor C1 is connected in parallel to the positive and negative busbars of inverter unit 2. Therefore, based on the above connection configuration, the multiple windings of the motor can be fully utilized to meet the functional requirements of the vehicle under different conditions, improve energy utilization efficiency, and enhance system compatibility.

[0056] In some embodiments, the energy conversion device 10 further includes a controller connected to the inverter unit 2.

[0057] Specifically, based on Figure 3The connection shown indicates that the controller is configured to: in the sixth state, control the first switching unit to conduct, control the bridge arm corresponding to the first set of windings to drive the vehicle, and control the upper and lower bridge arms of each phase bridge arm corresponding to the second set of windings to work alternately, so as to at least achieve self-heating of the battery pack. Thus, by controlling the motor operation through the above control method, the self-heating requirements of the battery can still be met while the vehicle is in motion. This fully utilizes the multiple sets of motor windings to achieve coordinated control of vehicle operation and battery self-heating, improving energy utilization efficiency and enhancing system compatibility.

[0058] In some embodiments, based on Figure 3 The connection shown indicates that the controller is further configured to: obtain the common-mode voltage value corresponding to each phase arm of the second winding based on the phase current value, the self-heating target current amplitude, and the self-heating current frequency; obtain the duty cycle corresponding to each phase arm of the second winding based on the common-mode voltage value; and control the upper and lower arms of each phase arm to work alternately according to the duty cycle, thereby achieving self-heating of the battery pack. Thus, by controlling the motor operation through the above control method, the self-heating requirements of the battery can still be met while the vehicle is in motion, effectively solving the problem of the battery not being able to self-heat while in motion.

[0059] In some embodiments, based on Figure 3 The connection method shown indicates that the controller is further configured to: obtain the differential-mode voltage value corresponding to each phase bridge arm based on the phase current value, rotor electrical angle, D-axis target current value, and Q-axis target current value of the second set of windings; obtain the common-mode voltage value corresponding to each phase bridge arm based on the phase current value, self-heating target current amplitude, and self-heating current frequency of each phase bridge arm of the second set of windings; obtain the duty cycle corresponding to each phase bridge arm of the second set of windings based on the differential-mode voltage value and the common-mode voltage value; and control the upper and lower bridge arms of each phase bridge arm to work alternately according to the duty cycle corresponding to each phase bridge arm of the second set of windings, so as to achieve the coordination of motor drive and battery self-heating. Thus, by controlling the motor operation through the above control method, the self-heating requirements of the battery can still be met while the vehicle is in motion. This fully utilizes the multiple sets of motor windings to achieve coordinated control of vehicle operation and battery self-heating, improving energy utilization efficiency and enhancing system compatibility.

[0060] In some embodiments, based on Figure 3The controller, in the seventh state, is configured to: control the first switching unit to conduct, control the bridge arm corresponding to the first set of windings to drive the vehicle, and control the upper and lower bridge arms of each phase bridge arm corresponding to the second set of windings to work alternately, so as to at least cause the first battery pack and the second battery pack to charge and discharge alternately, thereby achieving self-heating of the battery pack, and ensuring that the absolute value of the difference between the capacitance of the first battery pack and the capacitance of the second battery pack is lower than a preset threshold. Thus, by controlling the motor operation through the above control method, the vehicle can achieve both battery self-heating and battery pack balancing while driving. This fully utilizes the multiple sets of motor windings to achieve coordinated control of vehicle driving, battery balancing, and battery self-heating, improving energy utilization efficiency, enhancing system compatibility, effectively preventing over-discharge of the battery pack, and extending the battery pack's lifespan.

[0061] In some embodiments, based on Figure 3 The connection method shown indicates that the controller is further configured to: obtain the common-mode voltage value corresponding to each phase arm of the second winding based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating equalization current on each phase arm of the second winding; obtain the duty cycle corresponding to each phase arm of the second winding based on the common-mode voltage value; and control the upper and lower arms of each phase arm to work alternately according to the duty cycle corresponding to each phase arm of the second winding, so as to achieve self-heating of the battery pack and ensure that the absolute value of the difference between the capacitance of the first battery pack and the capacitance of the second battery pack is lower than a preset threshold. Thus, by controlling the motor operation through the above control method, the problem of battery self-heating during vehicle operation is effectively solved, and the problem of over-discharge of the battery pack is effectively avoided, thereby improving the service life of the battery pack.

[0062] In some embodiments, based on Figure 3In the connection method shown, the controller is also configured to: obtain the differential mode voltage value corresponding to each phase bridge arm based on the phase current value, rotor electrical angle, D-axis target current value, and Q-axis target current value on each phase bridge arm of the second set of windings; obtain the common mode voltage value corresponding to each phase bridge arm based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating equalization current on each phase bridge arm of the second set of windings; obtain the duty cycle corresponding to each bridge arm based on the differential mode voltage value and the common mode voltage value; control the upper and lower bridge arms of each phase bridge arm to work alternately according to the duty cycle corresponding to each phase bridge arm of the second set of windings, so that the first battery pack and the second battery pack are charged and discharged alternately, so as to realize the coordination of motor drive and battery pack self-heating, and so that the absolute value of the difference between the capacitance of the first battery pack and the capacitance of the second battery pack is lower than a preset threshold. Therefore, by controlling the motor operation through the above control method, the vehicle can achieve both battery self-heating and battery pack balancing while in motion. By making full use of the multiple windings of the motor, the vehicle's operation, battery balancing, and battery self-heating can be coordinated and controlled, which not only improves energy utilization efficiency and system compatibility, but also effectively avoids the problem of over-discharge of the battery pack and extends the battery pack's lifespan.

[0063] In some embodiments, the energy conversion device 10 further includes a DC charging / discharging port and a controller.

[0064] The positive terminal of the DC charging / discharging port is connected to the first bus terminal, and the negative terminal of the DC charging / discharging port is connected to the second bus terminal. The first end of the Y-phase bridge arm is connected to form the first bus terminal, and the second end of the Y-phase bridge arm is connected to form the second bus terminal. The controller is connected to the inverter unit 2.

[0065] Specifically, based on Figure 1 The connection method shown indicates that the controller is configured as follows: In the eighth state, it controls the first switching unit to conduct, and obtains the common-mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, and self-heating current frequency on each phase arm of the second set of windings; it obtains the duty cycle corresponding to each group of arms based on the common-mode voltage value; and it controls the upper and lower arms of each phase arm to work alternately based on the duty cycle corresponding to each phase arm of the second set of windings, so as to achieve the synergy of DC charging / discharging and battery pack self-heating. Therefore, through the connection configuration of the DC charging / discharging port and the inverter unit 2, the charging or discharging function of the battery pack is effectively combined with the self-heating function of the battery pack, thus facilitating simultaneous battery self-heating even when the vehicle is charging or discharging, thereby effectively improving the charging / discharging capacity and efficiency of the battery pack.

[0066] In some embodiments, when obtaining the differential mode voltage value corresponding to each phase arm based on the phase current value, rotor electrical angle, D-axis target current value and Q-axis target current value on each phase arm, the controller is specifically configured to perform the following steps.

[0067] Step S1: Obtain the bus voltage value at both ends of the battery pack, the torque value of the motor, and the speed value of the motor;

[0068] The bus voltage value can be obtained by setting a voltage sampling unit, as shown in the reference. Figure 1 As shown, the voltage sampling unit is connected to capacitor C1 and controller, and is used to collect the bus voltage value across capacitor C1, denoted as Udc.

[0069] Step S2: Obtain the target current values ​​for the D-axis and Q-axis based on the bus voltage, motor torque, and motor speed.

[0070] Step S3: Obtain the differential mode voltage value corresponding to each phase bridge arm based on the phase current value, rotor electrical angle, D-axis target current value and Q-axis target current value on each phase bridge arm.

[0071] Specifically, the phase current value on each phase bridge arm can be obtained by setting a current sampling unit, such as a reference. Figure 1 As shown, the current sampling unit is connected to the inverter unit 2 and the controller to collect the phase current value on each group of bridge arms. For example, a current sensor can be installed on the connection line connecting each group of bridge arms to the corresponding winding of the motor to obtain the phase current value of each group of bridge arms.

[0072] In the embodiment, reference Figure 4 As shown, the sampled phase current values ​​i1, i2...ip on each bridge arm are transformed to iα and iβ in the αβ coordinate system using Clark coordinate transformation. Based on the motor rotor electrical angle, iα and iβ are then transformed to the dq coordinate system using Park coordinate transformation to obtain the actual current values ​​id on the D-axis and iq on the Q-axis. The difference between the target current value id* on the D-axis and the actual current value id on the D-axis is used to obtain the target voltage value Ud on the D-axis through PID control. Similarly, the difference between the target current value iq* on the Q-axis and the actual current value iq on the Q-axis is used to obtain the target voltage value Uq on the Q-axis through PID control.

[0073] Then, the target voltage value Ud on the D-axis, the target voltage value Uq on the Q-axis, and the electric angle of the motor rotor are obtained by inverse Park transformation to obtain Uα and Uβ. Then, Uα and Uβ are obtained by inverse Clark transformation to obtain the differential mode voltage value of each phase bridge arm control, denoted as U1, U2...Up.

[0074] In some embodiments, when the common-mode voltage value corresponding to each phase arm is obtained based on the phase current value, the self-heating target current amplitude, and the self-heating current frequency on each phase arm, the controller is specifically configured to perform the following steps.

[0075] Step S4: Obtain the actual current value of the N line based on the phase current value on each phase bridge arm.

[0076] In the embodiment, reference Figure 1 As shown, the motor is a six-phase seven-wire motor. Taking the direction of current flow into the motor as the whole, the phase current values ​​on the six bridge arms are denoted as ia, ib, ic, iu, iv, and iw respectively. The actual current value of the N line is denoted as in, and it satisfies ia+ib+ic+iu+iv+iw+in=0. Based on this, the actual current value of the N line in=-ia-ib-ic-iu-iv-iw.

[0077] In some embodiments, a current sensor may be directly installed on the N line of motor 4 to directly collect the actual current value of the N line; there are no restrictions on this.

[0078] Step S5: Obtain the target current value of the N-line based on the amplitude of the self-heating target current and the frequency of the self-heating current.

[0079] In this embodiment, the self-heating target current amplitude (denoted as ipk) and self-heating current frequency (denoted as f) can be obtained from the current cell temperature of the battery pack. Specifically, the self-heating power corresponding to the cell temperature, the self-heating target current amplitude, and the self-heating current frequency can be pre-calibrated. In actual application, the required self-heating power of the battery pack is first obtained based on the vehicle status and the power battery status. Then, the self-heating target current amplitude and self-heating current frequency are determined by looking up a table or by linear fitting based on the current cell temperature and the required self-heating power.

[0080] Furthermore, when balancing the battery packs, a self-heating balancing current value is introduced to calculate the target current value for the N-line. This self-heating balancing current value, denoted as indc, can be obtained from the difference in SOC (State of Charge) between the first battery pack E1 and the second battery pack E2, or it can be obtained from the current difference between the positive and negative terminals of the battery pack 11 bus. No restriction is placed on this. Specifically, the target current value for the N-line can be obtained using the following formula (1) or formula (2).

[0081] in*=indc+ipk*cos 2 Formula (1)

[0082] in*=indc+ipk*sin 2 Formula (2)

[0083] Whereindc is the self-heating equalization current value,ipk is the self-heating target current amplitude, andf is the self-heating current frequency.

[0084] Step S6: Obtain the common-mode voltage value corresponding to each phase bridge arm based on the actual current value of the N-line and the target current value of the N-line.

[0085] Specifically, the common-mode voltage Un of each phase arm can be obtained through PI or PR closed-loop control based on the neutral line target current value In* and the actual neutral line current value in.

[0086] In some embodiments, the energy conversion device 10 further includes a first switching transistor VT13 and a second switching transistor VT14. The drain terminal of the first switching transistor VT13 is connected to the first end of the first switching unit 3, and the gate terminal of the first switching transistor VT13 is connected to the controller. The source terminal of the second switching transistor VT14 is connected to the source terminal of the first switching transistor VT13, the drain terminal of the second switching transistor VT14 is connected to the neutral point of the motor 1, and the gate terminal of the second switching transistor VT14 is connected to the controller. Therefore, by setting the first switching transistor VT13 and the second switching transistor VT14, and considering that the switching speeds of the first switching transistor VT13 and the second switching transistor VT14 are higher than the switching speed of the third switching unit 7, the disconnection speed of the self-heating circuit can be effectively improved, thus protecting the third switching unit 7 and preventing sintering problems in the third switching unit 7.

[0087] In summary, the energy conversion device according to the embodiments of the present invention can realize battery self-heating and waste heat utilization technology of electric drive system in any state of vehicle, especially self-heating when the vehicle is in charging / discharging state or driving state, realize high reuse of electric drive system, maximize system energy utilization efficiency and battery performance, greatly improve the performance of power battery in low temperature environment, solve the problem of limited use of battery in low temperature environment, improve battery compatibility and improve user experience.

[0088] A second aspect of the present invention provides a vehicle, such as Figure 5 As shown, the vehicle 100 includes the energy conversion device 10 of the above embodiment.

[0089] According to the vehicle 100 of the present invention, by employing the energy conversion device 10 of the above embodiment, the multiple windings of the motor can be fully utilized to meet the functional requirements of the vehicle under different states, improve energy utilization efficiency, and enhance system compatibility.

[0090] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0091] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An energy conversion device, characterized in that, It includes: A battery pack, the battery pack comprising two first battery packs and a second battery pack connected in series; An inverter unit, the inverter unit includes Y-phase bridge arms, each phase bridge arm includes an upper bridge arm and a lower bridge arm, the first end of each phase bridge arm is connected to the positive terminal of the first battery pack, and the second end of each phase bridge arm is connected to the negative terminal of the second battery pack. The motor comprises X sets of windings. The third end of each phase bridge arm is connected to the first end of a phase coil of the corresponding set of windings. The second ends of the multi-phase coils of at least one set of windings in the X sets of windings are connected together and led out with an N wire. The second ends of the multi-phase coils of the remaining sets of windings in the X sets of windings are connected together. The number of phases of the bridge arm is equal to the number of phases of the coil, X ≥ 2, and the number of phases of each set of windings is m. X Each phase, in each set of windings, includes n phase coils. X There are n coil branches. X ≥1,m X ≥2, wherein the X sets of windings are used to realize one or more of the following: motor drive, battery self-heating, battery equalization processing, and DC charging and discharging; A first switching unit, wherein a first end of the first switching unit is connected to the N line, and a second end of the first switching unit is connected to the midpoint between the first battery pack and the second battery pack; A controller, connected to the inverter unit, is configured to: in a first state, control the first switching unit to be turned on, and obtain the differential mode voltage value corresponding to each phase arm based on the phase current value, rotor electrical angle, D-axis target current value and Q-axis target current value on each phase arm; The common-mode voltage value corresponding to each phase arm is obtained based on the phase current value, the self-heating target current amplitude, and the self-heating current frequency on each phase arm. The duty cycle of each bridge arm is obtained based on the differential mode voltage value and the common mode voltage value. The upper and lower bridge arms of each phase bridge arm are controlled to work alternately according to the duty cycle of each phase bridge arm, so as to achieve the synergy between motor drive and the self-heating of the battery pack.

2. The energy conversion device according to claim 1, characterized in that, The inverter unit includes a six-phase bridge arm, and the motor includes two sets of windings, each set of windings includes two pairs of poles, and each pair of poles includes three coil branches. In the same set of windings, the first ends of the coil branches in phase in the three coil branches of the two pairs of poles are connected together and connected to the midpoint of the corresponding bridge arm. The second ends of the three coil branches of each pair of poles are connected together to form a neutral point. All neutral points of the two sets of windings are connected together and the N line is led out.

3. The energy conversion device according to claim 2, characterized in that, It also includes: The controller is connected to the inverter unit and is configured to: in a second state, control the first switching unit to be turned on, and obtain the differential mode voltage value corresponding to each phase arm based on the phase current value, rotor electrical angle, D-axis target current value and Q-axis target current value on each phase arm; The common-mode voltage value corresponding to each phase arm is obtained based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating equalization current on each phase arm. The duty cycle of each bridge arm is obtained based on the differential mode voltage value and the common mode voltage value. Based on the duty cycle of each phase bridge arm, the upper and lower bridge arms of each phase bridge arm are controlled to work alternately, so as to achieve the coordination of motor drive, self-heating of the battery pack and equalization processing of the battery pack.

4. The energy conversion device according to claim 2, characterized in that, It also includes: A controller, connected to the inverter unit, is configured to: in a third state, control the first switching unit to turn on, and obtain the common-mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating equalization current on each phase arm; The duty cycle corresponding to each bridge arm is obtained based on the common-mode voltage value; The upper and lower arms of each phase bridge arm are controlled to work alternately according to the duty cycle of each phase bridge arm, so as to achieve the coordinated self-heating of the battery pack and the equalization processing of the battery pack.

5. The energy conversion device according to claim 2, characterized in that, It also includes: A DC charging / discharging port is provided, with its positive terminal connected to a first busbar and its negative terminal connected to a second busbar. The first busbar is formed by the first end of the Y-phase bridge arm and the second busbar is formed by the second end of the Y-phase bridge arm. A controller, connected to the inverter unit, is configured to: in a fourth state, control the first switching unit to turn on, and obtain the common-mode voltage value corresponding to each phase arm based on the phase current value, the self-heating target current amplitude, and the self-heating current frequency on each phase arm; The duty cycle corresponding to each bridge arm is obtained based on the common-mode voltage value; The upper and lower arms of each phase bridge arm are controlled to work alternately according to the duty cycle of each phase bridge arm, so as to achieve the synergy of DC charging and discharging and the self-heating of the battery pack.

6. The energy conversion device according to claim 5, characterized in that, The controller is also configured to: in the fifth state, control the first switching unit to be turned on, and obtain the common mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude, self-heating current frequency and self-heating equalization current on each phase arm; The duty cycle corresponding to each bridge arm is obtained based on the common-mode voltage value; The upper and lower arms of each phase bridge arm are controlled to work alternately according to the duty cycle of each phase bridge arm, so as to achieve the coordinated operation of DC charging and discharging, self-heating of the battery pack and equalization processing of the battery pack.

7. The energy conversion device according to claim 1, characterized in that, The inverter unit includes six-phase bridge arms. The motor includes: The first set of windings includes two pairs of poles, each pair of poles includes three coil branches. The first ends of the coil branches of the same phase in the three coil branches of the two pairs of poles of the first set of windings are connected together and connected to the midpoint of the corresponding phase bridge arm. The second ends of the three coil branches of the two pairs of poles of the first set of windings are connected together. The second set of windings includes two pairs of poles, each pair of poles including three coil branches. The first ends of the coil branches of the same phase in the three coil branches of the two pairs of poles of the second set of windings are connected together and connected to the midpoint of the corresponding phase bridge arm. The second ends of the three coil branches of the two pairs of poles of the second set of windings are connected together and led out as N line.

8. The energy conversion device according to claim 7, characterized in that, Also includes: A controller, connected to the inverter unit, is configured to: in a sixth state, control the first switching unit to conduct, control the bridge arm corresponding to the first set of windings to drive the vehicle, and control the upper and lower bridge arms of each phase bridge arm corresponding to the second set of windings to work alternately to at least achieve self-heating of the battery pack.

9. The energy conversion device according to claim 8, characterized in that, The controller is configured to: The common-mode voltage value corresponding to each phase arm is obtained based on the phase current value, self-heating target current amplitude, and self-heating current frequency on each phase arm of the second set of windings. The duty cycle of each phase arm of the second set of windings is obtained based on the common-mode voltage value. The upper and lower bridge arms of each phase bridge arm are controlled to work alternately according to the duty cycle of each phase bridge arm of the second set of windings, so as to realize the self-heating of the battery pack.

10. The energy conversion device according to claim 8, characterized in that, The controller is configured to: The differential mode voltage value corresponding to each phase bridge arm is obtained based on the phase current value, rotor electrical angle, D-axis target current value and Q-axis target current value of the second set of windings; The common-mode voltage value corresponding to each phase arm is obtained based on the phase current value, self-heating target current amplitude, and self-heating current frequency on each phase arm of the second set of windings. The duty cycle of each phase arm of the second set of windings is obtained based on the differential mode voltage value and the common mode voltage value. Based on the duty cycle of each phase bridge arm of the second set of windings, the upper and lower bridge arms of each phase bridge arm are controlled to work alternately, so as to achieve the synergy between motor drive and the self-heating of the battery pack.

11. The energy conversion device according to claim 7, characterized in that, The controller is configured to: in the seventh state, control the first switching unit to turn on, control the bridge arm corresponding to the first set of windings to drive the vehicle, and control the upper and lower bridge arms of each phase bridge arm corresponding to the second set of windings to work alternately, so as to at least cause the first battery pack and the second battery pack to charge and discharge alternately, so as to achieve self-heating of the battery pack, and cause the absolute value of the difference between the capacitance of the first battery pack and the capacitance of the second battery pack to be lower than a preset threshold.

12. The energy conversion device according to claim 11, characterized in that, The controller is configured to: The common-mode voltage value corresponding to each phase arm is obtained based on the phase current value, self-heating target current amplitude, self-heating current frequency, and self-heating equalization current on each phase arm of the second set of windings. The duty cycle of each phase arm of the second set of windings is obtained based on the common-mode voltage value. According to the duty cycle of each phase bridge arm of the second set of windings, the upper and lower bridge arms of each phase bridge arm are controlled to work alternately to achieve self-heating of the battery pack, and to make the absolute value of the difference between the capacitance of the first battery pack and the capacitance of the second battery pack lower than the preset threshold.

13. The energy conversion device according to claim 11, characterized in that, The controller is configured to: The differential mode voltage value corresponding to each phase bridge arm is obtained based on the phase current value, rotor electrical angle, D-axis target current value and Q-axis target current value on each phase bridge arm of the second set of windings. The common-mode voltage value corresponding to each phase arm is obtained based on the phase current value, self-heating target current amplitude, self-heating current frequency and self-heating equalization current on each phase arm of the second set of windings. The duty cycle of each bridge arm is obtained based on the differential mode voltage value and the common mode voltage value. According to the duty cycle of each phase bridge arm of the second set of windings, the upper and lower bridge arms of each phase bridge arm are controlled to work alternately, so that the first battery pack and the second battery pack are charged and discharged alternately, so as to realize the synergy of motor drive and self-heating of the battery pack, and so that the absolute value of the difference between the capacitance of the first battery pack and the capacitance of the second battery pack is lower than the preset threshold.

14. The energy conversion device according to claim 7, characterized in that, It also includes: A DC charging / discharging port is provided, with its positive terminal connected to a first busbar and its negative terminal connected to a second busbar. The first busbar is formed by the first end of the Y-phase bridge arm and the second busbar is formed by the second end of the Y-phase bridge arm. The controller is connected to the inverter unit and is configured to: in the eighth state, control the first switching unit to be turned on, and obtain the common mode voltage value corresponding to each phase arm based on the phase current value, self-heating target current amplitude and self-heating current frequency on each phase arm of the second set of windings; The duty cycle corresponding to each bridge arm is obtained based on the common-mode voltage value; Based on the duty cycle of each phase bridge arm of the second set of windings, the upper and lower bridge arms of each phase bridge arm are controlled to work alternately to achieve the synergy of DC charging and discharging and the self-heating of the battery pack.

15. The energy conversion device according to any one of claims 1, 3, 10, and 13, characterized in that, When obtaining the differential mode voltage value corresponding to each phase arm based on the phase current value, rotor electrical angle, D-axis target current value, and Q-axis target current value of each phase arm, the controller is specifically configured as follows: Obtain the bus voltage value at both ends of the battery pack, the torque value of the motor, and the speed value of the motor; The target current values ​​for the D-axis and Q-axis are obtained based on the bus voltage value, the motor torque value, and the motor speed value. The differential mode voltage value corresponding to each phase bridge arm is obtained based on the phase current value, rotor electrical angle, target current value of the D-axis, and target current value of the Q-axis on each phase bridge arm.

16. The energy conversion device according to any one of claims 1, 5, 9, 10 and 14, characterized in that, When obtaining the common-mode voltage value corresponding to each phase arm based on the phase current value, the self-heating target current amplitude, and the self-heating current frequency on each phase arm, the controller is specifically configured as follows: The actual current value of the N-line is obtained based on the phase current value on each phase arm. The target current value of the N-line is obtained based on the amplitude of the self-heating target current and the frequency of the self-heating current. The common-mode voltage value corresponding to each phase arm is obtained based on the actual current value of the N-line and the target current value of the N-line.

17. A vehicle, characterized in that, Includes the energy conversion device according to any one of claims 1-16.

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