MOTOR CONTROLLER, HEAT EXCHANGE SYSTEM, AND CURRENT INJECTION METHOD

Abstract

A motor controller, a heat exchange system, and a current injection method are provided for improving the heating efficiency of a motor. The motor controller includes a control device and an inverter circuit. The control device is configured to control the inverter circuit to input an AC current to the motor, the AC current having a DC current bias, and the AC current is used to heat the motor. The inverter circuit is configured to output the AC current to a direct axis or a zero axis of the motor under control of the control device.

Description

[Technical field]

[0001] This application relates to a new energy Car skills The present invention relates to the field of electrical engineering, particularly to motor controllers, heat exchange systems, and current injection methods. [Background technology]

[0002] With the technological development of the new energy field, new energy vehicles, such as electric vehicles / electric automobiles, car / Hybrid vehicles are becoming more widely used. In low temperature environment, the performance of the power battery of electric vehicles will decrease. Therefore, the power battery needs to be heated to improve the performance of the power battery.

[0003] In the prior art, the heating solution for the power battery is as follows: current is input to the motor, the end windings of the motor are used to generate heat, and then the generated heat is released through a heat exchange system to heat the power battery. In this solution, neither the iron loss nor the permanent magnet loss of the motor can be excited, so the heat emission power is relatively low and the heating rate of the power battery is relatively low.

[0004] Therefore, the solutions provided by the prior art suffer from low heat dissipation output and slow heating rate of the power battery. Summary of the Invention

[0005] SUMMARY OF THE DISCLOSURE The embodiments of the present application provide a motor controller, a heat exchange system, and a current injection method to improve the heating efficiency of the motor.

[0006] According to a first aspect, an embodiment of the present application provides a motor controller. The motor controller includes a controller and an inverter circuit. The controller is configured to control the inverter circuit to input an AC current to the motor, the AC current having a DC current bias, and the AC current is used to heat the motor. The inverter circuit is configured to output the AC current to a direct axis or a zero axis of the motor under the control of the controller.

[0007] The alternating current may be one of a sine wave, a square wave, a triangular wave, a sawtooth wave, a trapezoidal wave, or may be another non-direct current that varies periodically.

[0008] According to the motor controller provided in the first aspect, no current is input to the quadrature axis of the motor, so that the motor has no additional vibration or torque. An AC current with a DC current bias is input to the direct axis or zero axis. Compared with the method in the prior art in which only the end winding is used to generate heat, the current input to the motor contains an AC current component, which can effectively induce the iron loss and permanent magnet loss of the motor, and can improve the heat dissipation output of the motor, thus improving the heating rate of the power battery.

[0009] In a possible design, a three-phase, three-wire system is used with an inverter circuit, which is specifically configured to output a first AC current with a DC current bias to a direct shaft of the motor under the control of a controller.

[0010] According to the above solution, no current is input to the quadrature axis of the motor, so there is no additional vibration or torque in the motor. The first AC current, which has a DC current bias and is input to the direct axis, contains an AC current component. Therefore, it can effectively induce the iron loss and permanent magnet loss of the motor, and can improve the heat dissipation output of the motor, so that the heating rate of the power battery is improved.

[0011] In another possible design, a three-phase, four-wire system is used with an inverter circuit that is specifically configured to output a second AC current with a DC current bias on the zero axis of the motor under control of the controller, or to output a third AC current with a DC current bias on the direct axis of the motor under control of the controller.

[0012] According to the above solution, no current is input to the quadrature axis of the motor, so there is no additional vibration or torque in the motor. The second AC current, which has a DC current bias and is input to the zero axis, contains an AC current component. Therefore, it can effectively induce the iron loss and permanent magnet loss of the motor, and can improve the heat dissipation output of the motor, so that the heating rate of the power battery is improved.

[0013] In addition, when a second AC current with a DC current bias is input to the zero axis of the motor, the three-phase currents have the same amplitude and the same phase. Therefore, the three-phase windings of the motor will heat up evenly and have the same temperature, and the case where one phase winding reaches its temperature limit while the temperatures of the other two phase windings are relatively low will not occur, so that the heat dissipation capacity of the windings can be more fully utilized.

[0014] Further, the inverter circuit is connected to a DC bus. A two-level topology is used for the inverter circuit, and a neutral point of the inverter circuit is connected to a positive pole of the DC bus via a first switch unit and a first inductor. Alternatively, a two-level topology is used for the inverter circuit, and a neutral point of the inverter circuit is connected to a negative pole of the DC bus via a second switch unit and a second inductor. Alternatively, a two-level topology is used for the inverter circuit, and a neutral point of the inverter circuit is connected to a positive pole of the DC bus via a third switch unit and a third inductor, and a neutral point of the inverter circuit is connected to a negative pole of the DC bus via a fourth switch unit and a fourth inductor.

[0015] According to the above solution, a star point loop (neutral line loop) can be provided for the current flowing in the neutral line of the power supply of a three-wire or four-wire system.

[0016] In addition, if an open winding structure or a multi-level topology is used in the inverter circuit, there is no need to additionally connect the star point loop.

[0017] In a possible design, the alternating current has no negative values.

[0018] Not having a negative value means that the AC current has a positive value at any time. When the AC current has no negative value, the magnetic field generated by the winding is a pulsating magnetic field with only amplitude changes and no direction changes, and no demagnetizing magnetic field is generated. Therefore, the risk of demagnetization in the motor heating process can be reduced, and the electromagnetic vibration and noise caused by the positive and negative changes of the magnetic field in the same direction are reduced.

[0019] According to a second aspect, an embodiment of the present application provides a heat exchange system including a motor, a heat exchanger, a hydraulic pump, a power battery, and a motor controller provided in any one of the first aspect and the possible designs of the first aspect. The motor, the heat exchanger, and the hydraulic pump are connected via pipes. The motor controller is configured to output an AC current to a direct axis or a zero axis of the motor. The AC current has a DC current bias and is used to enable the motor to release heat. The hydraulic pump is configured to drive the pipes such that the heat released by the motor is exchanged through the heat exchanger to the power battery.

[0020] In a possible design, the motor is an oil-cooled motor.

[0021] For specific functions and structures of the motor controller in the heat exchange system provided in the second aspect, please refer to the relevant description of the motor controller provided in the first aspect.

[0022] According to a third aspect, an embodiment of the present application provides a current injection method, the method including the steps of: a motor controller determines parameters of an AC current output to a motor, the AC current having a DC current bias, the AC current being used to heat the motor; the motor controller outputs the AC current to a direct axis or a zero axis of the motor.

[0023] Specifically, the parameters of the AC current include the waveform, phase, amplitude, frequency, and DC current bias value of the AC current.

[0024] The AC current output to the motor is used to heat the motor in order to heat the power battery, and therefore the motor controller may determine parameters of the AC current based on factors such as the temperature of the motor, the temperature of the power battery, and the current and temperature limits of the three-phase windings of the motor.

[0025] The current injection method provided in the third aspect may be regarded as a method executed by the motor controller provided in the first aspect. For specific implementation, please refer to the related description of the motor controller provided in the first aspect.

[0026] According to a fourth aspect, an embodiment of the present application further provides a power assembly comprising a motor, a reducer and a motor controller provided in any one of the first aspect and possible designs of the first aspect.

[0027] According to a fifth aspect, an embodiment of the present application further provides a vehicle comprising a power battery and a power assembly provided in the fourth aspect.

[0028] In addition, for the technical effects brought about by any possible design methods of the second to fifth aspects, please refer to the technical effects brought about by different design methods of the first aspect, and the details will not be described again here. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram of a structure of a heat exchange system according to an embodiment of the present application.

[0030] [Diagram 2] FIG. 1 is a schematic diagram of a structure of a motor according to an embodiment of the present application.

[0031] [Diagram 3] FIG. 2 is a schematic diagram of the structure of a motor controller according to an embodiment of the present application.

[0032] [Figure 4] FIG. 2 is a schematic diagram of an AC current with a DC current bias according to an embodiment of the present application.

[0033] [Diagram 5] FIG. 2 is a schematic diagram of an alternating current with a small negative value according to an embodiment of the present application.

[0034] [Figure 6] FIG. 2 is a schematic diagram of the structure of an inverter circuit using a three-phase three-wire system according to an embodiment of the present application.

[0035] [Figure 7] FIG. 2 is a schematic diagram of three-phase currents output to a motor according to an embodiment of the present application.

[0036] [Figure 8] FIG. 2 is a schematic diagram of the structure of an inverter circuit using a three-phase four-wire system according to an embodiment of the present application.

[0037] [Figure 9] FIG. 13 is a schematic diagram of another three-phase current output to a motor according to an embodiment of the present application.

[0038] [Figure 10] FIG. 2 is a schematic diagram of a star point loop structure according to an embodiment of the present application.

[0039] [Figure 11] FIG. 2 is a schematic diagram of the structure of an inverter circuit according to an embodiment of the present application.

[0040] [Figure 12] FIG. 1 is a schematic diagram of the structure of an inverter circuit with a three-level topology according to an embodiment of the present application.

[0041] [Figure 13] FIG. 2 is a schematic diagram of a structure of another heat exchange system according to an embodiment of the present application.

[0042] [Figure 14] 1 is a schematic flow chart of a current injection method according to an embodiment of the present application.

[0043] [Figure 15] FIG. 2 is a schematic diagram of a structure of a power assembly according to an embodiment of the present application.

[0044] [Figure 16] 1 is a schematic diagram of a vehicle structure according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] First, application scenarios in the embodiments of the present application will be described below.

[0046] In an embodiment of the present application, the heat exchange system shown in Figure 1 may be used. The heat exchange system may be a heat exchange system of an electric vehicle.

[0047] The heat exchange system shown in FIG. 1 includes a power battery 101 , a motor controller 102 , a motor 103 , a heat exchanger 104 , and a hydraulic pump 105 .

[0048] The power battery 101 is configured to output direct current and may be, for example, a storage battery, a lithium battery, a fuel cell, or a supercapacitor. The motor controller may also be called a motor control unit (MCU) and includes a control device and an inverter circuit. The motor 103 may be a permanent magnet synchronous motor, an asynchronous motor, a reluctance motor, an electrically excited motor, etc.

[0049] The power battery 101 is connected to an inverter circuit via a DC bus, and the inverter circuit is connected to the motor 103 via a three-phase line. The motor 103, the heat exchanger 104, and the hydraulic pump 105 are coupled through an oil-cooled pipe through which an insulating coolant flows. The insulating coolant may include mineral insulating oil, synthetic insulating oil, vegetable oil, etc. The motor controller 102, the heat exchanger 104, and the power battery 101 are coupled through a water-cooled pipe. The water inlet of the water-cooled pipe is disposed around the motor controller 102, and the water outlet is disposed around the power battery 101. In particular, the heat exchanger 104 may be disposed around the power battery 101 to facilitate heat exchange with the power battery 101. There is no insulation requirement for the coolant in the water-cooled pipe. For example, the coolant may be water, alcohol, or a mixture of different types of antifreeze. For ease of explanation, in this embodiment of the present application, an example in which the coolant flowing in the water-cooled pipe is water is used for explanation.

[0050] In this embodiment of the present application, the motor controller 102 injects current into the motor 103 to heat the motor 103. The heat generated by the motor 103 is exchanged with the power battery 101 via the heat exchanger 104 to heat the power battery 101 to improve the performance of the power battery 101.

[0051] Specifically, the process of heating the aforementioned power battery 101 may be as follows: the control device controls the inverter circuit to inject current into the motor 103, and the motor 103 releases heat. The hydraulic pump 105 pumps the insulating coolant between the motor 103 and the heat exchanger 104, so that the heat released by the motor 103 is transferred to the heat exchanger 104 to cool the motor 103. The heat released by the motor 103 is exchanged with the water in the water-cooling pipe in the heat exchanger 104. The water in the water-cooling pipe transfers its heat to the power battery 101 to heat the power battery 101.

[0052] In addition, in an embodiment of the present application, when the motor controller 102 operates, the heat released by the resistor in the motor controller 102 is also transferred to the power battery 101 through the water-cooled pipe to heat the power battery 101.

[0053] In the heat exchange system shown in FIG. 1, a schematic diagram of a possible structure of the motor 103 can be shown in FIG. 2. In the cross-sectional view shown in FIG. 2, the motor 103 includes a housing, a rotor core, a stator, and a rotating shaft. A winding (not shown in FIG. 2) is wound around the stator. The winding is a coil wound on the iron teeth of the stator of the motor and is configured to provide a path for the current input to the motor. The parts extending from the stator core at the two axial ends of the rotating shaft of the motor are called end windings. The material of the winding is usually copper. A permanent magnet (not shown in FIG. 2) is installed in the rotor core to generate an exciting magnetic field. An oil channel is reserved in the housing, the rotating shaft, and the rotor core. When the hydraulic pump 105 drives the oil cooling pipe, the insulating coolant can flow into the oil channel of the motor 103, so that the heat released by the motor 103 can be more completely removed and the motor 103 is completely cooled. Specifically, the insulating coolant may enter and exit the motor cavity from the motor housing, or may enter and exit the motor cavity from both ends of the motor.

[0054] Additionally, the insulating coolant flowing through the motor 103 may be further used to lubricate the motor components, including the bearings.

[0055] In order to better understand the embodiments of the present application, the following describes some basic concepts in the embodiments of the present application.

[0056] 1.U / V / W three-phase coordinate axes

[0057] At present, the motor of an electric vehicle is usually an AC motor, and the power battery is a DC power source. Therefore, the DC current output by the power battery is converted into a three-phase AC current of the motor through an inverter circuit. The coordinate axes of the three-phase AC current are the U axis, the V axis, and the W axis, respectively. The three phases of the AC current can also be individually called the U phase, the V phase, and the W phase.

[0058] 2. Direct, quadrature, and zero axes

[0059] To simplify the analysis of motors, the stationary three-phase coordinates are usually transformed into rotating dq coordinates. Such a transformation is called the Park transformation.

[0060] In the dq coordinate system, the three coordinate axes are called the direct, quadrature, and zero axes, respectively.

[0061] The direct axis, also called the D axis or d axis, is a time-varying direct current coordinate axis obtained by Park transformation from the stationary U / V / W three-phase coordinate axis.

[0062] The quadrature axis, also called the Q axis or q axis, is a time-varying alternating current coordinate axis obtained by Park transformation from the stationary U / V / W three-phase coordinate axis.

[0063] The zero axis, also called the 0 axis or 0-axis, is the coordinate axis perpendicular to the dq plane in which the direct and quadrature axes lie.

[0064] Specifically, the formula for the Park transformation can be:

number

[0065] θ is the included angle between the d-axis and the U-axis. I_d is called the direct-axis current, which is mainly used to adjust the magnetic field. I_q is called the quadrature-axis current, which is mainly used to adjust the torque. I_0 is called the zero-sequence current. I_u, I_v, and I_w are the currents on the U-axis, V-axis, and W-axis, respectively, i.e., the three-phase currents.

[0066] In an embodiment of the present application, outputting a current to the direct axis of the motor is equivalent to inputting I_d to the motor, and I_q and I_0 are controlled to be 0. Outputting a current to the zero axis of the motor is equivalent to inputting I_0 to the motor, and I_d and I_q are controlled to be 0.

[0067] The above matrix is ​​the formula for converting the three-phase currents to I_d, I_q, and I_0. The formula for converting I_d, I_q, and I_0 to three-phase currents can be obtained by inverse transformation of the matrix transformation. It will not be described in detail here.

[0068] Because the three-phase current is the current corresponding to the actual windings of the motor, when outputting current to the direct axis of the motor, the motor controller needs to convert I_d into three-phase currents I_u, I_v, and I_w by inverse transformation of Park's transformation, and input I_u, I_v, and I_w to the windings of the motor; or, when outputting current to the zero axis of the motor, the motor controller needs to convert I_0 into three-phase currents I_u, I_v, and I_w by inverse transformation of Park's transformation, and input I_u, I_v, and I_w to the windings of the motor.

[0069] 3. Copper loss in permanent magnets, rotor core loss, eddy current loss

[0070] Copper losses, abbreviated as copper losses, refer to the losses due to current flowing in copper conductors.

[0071] Rotor core loss, abbreviated as iron loss, refers to the loss that occurs in the rotor core in an AC magnetic field, and includes eddy current loss caused by eddy currents induced by induction and hysteresis loss caused by hysteresis effects. Similarly, the rotor shaft and stator also generate eddy current loss and hysteresis loss in an AC magnetic field.

[0072] The eddy current loss of a permanent magnet is abbreviated as permanent magnet loss, which means that a permanent magnet generates an eddy current in an alternating magnetic field, resulting in a corresponding eddy current loss.

[0073] The following further describes in detail the embodiments of the present application with reference to the accompanying drawings.

[0074] It should be noted that "plurality" in the embodiments of the present application means two or more. In addition, in the description of the present application, terms such as "first" and "second" are merely used for distinction and explanation, and should not be understood as indicating or implying relative importance or indicating or implying order.

[0075] One embodiment of the present application provides a motor controller. As shown in Fig. 3, the motor controller 300 includes a control device 301 and an inverter circuit 302. The control device 301 is configured to control the inverter circuit 302 to input an AC current to the motor, and the AC current has a DC current bias and is used to heat the motor. The inverter circuit 302 is configured to output an AC current to a direct or zero axis of the motor under the control of the control device 301.

[0076] The AC current with the DC current bias is obtained after the DC current is superimposed on the AC current. For example, example a in Fig. 4 shows an AC current without a DC current bias input to the direct shaft of the motor, and example b in Fig. 4 shows an AC current with a DC current bias input to the direct shaft of the motor. In example b, Id_1 is the superimposed DC current bias.

[0077] It should be noted that in the example of Fig. 4, an example in which the AC current is a sine wave is used for explanation. In practical application, the AC current in this embodiment of the present application may be any one of a sine wave, a square wave, a triangular wave, a sawtooth wave, and a trapezoidal wave, or may be another non-DC current that changes periodically.

[0078] In particular, in this embodiment of the present application, the AC current input to the direct axis or zero axis may have no negative value or only a small amount of negative value. Not having a negative value means that the AC current always has a positive value. For example, in example b of FIG. 4, the AC current input to the direct axis has no negative value. As another example, the AC current shown in FIG. 5 has only a small amount of negative value.

[0079] When the AC current has no negative value, the magnetic field generated by the winding is a pulsating magnetic field with only amplitude change and no direction change, and no demagnetizing magnetic field is generated. In this case, it is easy to understand that the AC current has no negative value or only a small negative value, so the demagnetizing magnetic field is generated by the winding or the demagnetizing magnetic field is generated with only low intensity. Therefore, the risk of demagnetization in the motor heating process can be reduced, and the electromagnetic vibration and noise caused by the positive and negative changes of the magnetic field in the same direction can be reduced.

[0080] The control device 301 controls the inverter circuit 302 to output AC current to the direct or zero axis of the motor. Since no current is input to the quadrature axis of the motor, the motor has no additional vibration and torque. AC current with DC current bias is input to the direct or zero axis. Compared with the method in the prior art where only the end windings are used to release heat, the current input to the motor contains AC components, which can effectively induce the iron loss and permanent magnet loss of the motor, and can improve the heat release output of the motor, thereby improving the heating rate of the power battery. In addition, the heat released by the resistor of the motor controller 300 can also be used to heat the power battery. In addition, the current on the DC current bus is also AC current, and the effective value of the AC current is significantly greater than the effective current value that exists when only DC is input, so that the internal resistance of the battery can be fully utilized to heat the battery.

[0081] In addition, compared with a solution in which an AC current without a DC current bias is input to the DC axis or the zero axis, when the upper limit of the current on the DC current bus is the same, when an AC current with a DC current bias is input to the DC axis or the zero axis, the AC component flowing through the DC current bus may be relatively small, so that the fluctuation of the DC current bus can be reduced and the reliability of the system can be improved.

[0082] In practical applications, a three-phase three-wire system or a three-phase four-wire system may be used for the inverter circuit 302. For the three-phase three-wire system and the three-phase four-wire system, the motor controller 300 may inject current into the motor in different ways. The following describes the two cases separately.

[0083] 1. Three-phase, three-wire system

[0084] A three-phase, three-wire system is used for the inverter circuit 302. Specifically, the inverter circuit 302 is configured to output a first AC current having a DC current bias to a direct shaft of a motor under the control of the controller 301.

[0085] For example, a schematic diagram of the structure of an inverter circuit in a three-phase three-wire system may be shown in Figure 6. As described above, when a current is output to the direct axis of the motor, the motor controller 300 needs to convert I_d into three-phase currents I_u, I_v, and I_w by the inverse transformation of the Park transformation, and input I_u, I_v, and I_w to the windings of the motor. The three-phase currents output to the windings of the motor by the motor controller 300 are injected through the three-phase wires of the inverter circuit in the three-phase three-wire system.

[0086] The AC current with DC current bias in example b of Figure 4 is used as an example. The current is converted into a three-phase current. The waveform of the three-phase current can be shown in Figure 7. From Figure 7, it can be seen that when a first AC current with DC current bias is input into the direct shaft of the motor, the phases of the three-phase currents are the same or opposite, and the amplitudes of the three-phase currents are not equal. The V phase current and the W phase current have the same amplitude and the same phase, and the U phase current and the V phase current have opposite phases and different amplitudes.

[0087] The inverter circuit 302 outputs a first AC current with a DC current bias to the direct axis of the motor. Since no current is input to the quadrature axis of the motor, the motor has no additional vibration or torque. The first AC current with a DC current bias input to the direct axis includes an AC component. Therefore, it can effectively induce the iron loss and permanent magnet loss of the motor, and can improve the heat dissipation output of the motor, so that the heating rate of the power battery is improved. In addition, the heat generated by the resistor of the motor controller 300 can also be used to heat the power battery.

[0088] It should be noted that when the first AC current with DC current bias is input to the direct shaft of the motor, the amplitudes of the three-phase currents are not equal. For example, in the example of Figure 7, the amplitude of the U-phase current is large, and the amplitudes of the V-phase current and W-phase current are small. Therefore, the U-phase winding of the motor will release more heat, and the U-phase winding will reach its temperature limit first. In this case, the V-phase winding and the W-phase winding are still in a low temperature state. Therefore, this motor heating method has the problem that the heat release capacity of the windings is not fully utilized.

[0089] 2. Three-phase, four-wire system

[0090] An inverter circuit for a three-phase, four-wire system differs from an inverter circuit for a three-phase, three-wire system in that it has more than one neutral wire of the power supply from the neutral point (star point) of the three phases.

[0091] If a three-phase, four-wire system is used for the inverter circuit 302, the motor controller 300 may output current to the motor in two ways.

[0092] Method 1

[0093] A three-phase, four-wire system is used for the inverter circuit 302. The inverter circuit 302 is specifically configured to output a second AC current with a DC current bias to the zero axis of the motor under the control of the controller 301, i.e., to output a zero-sequence current to the motor.

[0094] For example, a schematic diagram of the structure of an inverter circuit in a three-phase four-wire system may be shown in Figure 8. As described above, when a current is output to the zero axis of the motor, the motor control device needs to convert I_d into three-phase currents I_u, I_v, and I_w by the inverse transformation of the Park transformation, and input I_u, I_v, and I_w to the windings of the motor. The three-phase currents output to the windings of the motor are input through the three-phase windings of the inverter circuit in a three-phase four-wire system.

[0095] Assume that the waveform of the second AC current having a DC current bias and outputted to the zero axis of the motor by the inverter circuit 302 is the same as the waveform shown in example b of Fig. 4. The current having the above waveform is converted into a three-phase current, and the waveform of the three-phase current can be shown in Fig. 9. From Fig. 9, it can be seen that when the second AC current having a DC current bias is inputted to the zero axis of the motor, the amplitude and phase of the three-phase current are the same.

[0096] The inverter circuit 302 outputs a second AC current with a DC current bias to the zero axis of the motor. Since no current is input to the quadrature axis of the motor, there is no additional vibration or torque in the motor. The second AC current with a DC current bias and input to the zero axis contains an AC component. Therefore, it can effectively induce the iron loss and permanent magnet loss of the motor, and can improve the heat dissipation output of the motor, so that the heating rate of the power battery is improved. In addition, the heat released by the resistor of the motor controller 300 can also be used to heat the power battery.

[0097] In addition, when a second AC current with a DC current bias is input to the zero axis of the motor, the three-phase currents have the same amplitude and the same phase. Therefore, the three-phase windings of the motor heat up evenly and have the same temperature, and the case where one phase winding reaches its temperature limit while the temperatures of the other two phase windings are relatively low does not occur, so that the heat dissipation output of the windings can be more fully utilized.

[0098] It should be noted that a three-phase four-wire system has more than one neutral conductor of the power supply from the neutral points (star points) of the three phases than a three-phase three-wire system. In this embodiment of the present application, a second AC with DC current bias is output to the zero axis of the motor, and current flows in the neutral conductor of the power supply. Thus, the inverter circuit 302 provides a flowing loop for the current in the neutral conductor of the power supply. If the inverter circuit 302 is not configured with such a loop, an additional star point loop needs to be connected.

[0099] In particular, the inverter circuit 302 is connected to the DC bus, and a two-level topology is used for the inverter circuit 302. The way of connecting the star point loop can be as follows: 1. The neutral point of the inverter circuit 302 is connected to the positive pole of the DC bus through a first switch unit and a first inductor, as shown in example a of FIG. 10; 2. The neutral point of the inverter circuit 302 is connected to the negative pole of the DC bus through a second switch unit and a second inductor, as shown in example b of FIG. 10; 3. The neutral point of the inverter circuit 302 is connected to the positive pole of the DC bus through a third switch unit and a third inductor, and the neutral point of the inverter circuit 302 is connected to the negative pole of the DC bus through a fourth switch unit and a fourth inductor, and the third switch unit and the fourth switch unit are not closed at the same time, as shown in example c of FIG. 10.

[0100] In some cases, the topology of the inverter circuit 302 may provide a loop for the current flowing in the neutral conductor of the power supply, and therefore no additional star point loop needs to be connected.

[0101] Case 1:

[0102] When the inverter circuit 302 includes two circuits with inverter functions, the inverter circuit 302 already includes a star point loop, and there is no need to additionally connect a star point loop.

[0103] For example, an inverter circuit 302 arranged for a dual three-phase motor or a six-phase motor can be shown in example a of Figure 11. The inverter circuit 302 includes two circuits with inverter functions and does not require an additional star point loop to be connected.

[0104] As another example, as shown in example b of FIG. 11, an open winding structure is used for the inverter circuit 302, and there is no need to additionally connect the star point loop.

[0105] Case 2:

[0106] When a multi-level topology is used for the inverter circuit 302, there is no need to additionally connect the star point loop because the multi-level topology includes the star point loop.

[0107] For example, the structure of an inverter circuit 302 using a three-level topology may be shown in Figure 12. From Figure 12, it can be seen that the inverter circuit 302 already includes a current-carrying loop on the neutral point (star point).

[0108] It should be noted that only the three-level topology shown in Figure 12 is used as an example for illustration in this embodiment of the present application. In the prior art, other three-level, five-level, or multi-level topologies are also applicable to this embodiment of the present application.

[0109] Method 2

[0110] A three-phase, four-wire system is used for the inverter circuit 302. The control device 301 is specifically configured to control the inverter circuit 302 to output a third AC current having a DC current bias to a direct shaft of the motor.

[0111] In other words, if a three-phase, four-wire system is used for the inverter circuit 302, the control device 301 may also control the inverter circuit 302 to output a third AC current with a DC current bias to the direct shaft of the motor, in which case no current flows in the neutral wire of the power supply.

[0112] In Method 2, for the method of connecting the star point loop, please refer to the relevant description in Method 1, and will not be described in detail here.

[0113] Compared with Method 1, in Method 2, the amplitude and phase of the three-phase current are not completely the same (see the example in Figure 7). Therefore, there is the aforementioned problem that the heat dissipation power of the windings is not fully utilized.

[0114] In conclusion, current is input to the motor using the motor controller 300 provided in the embodiment of the present application. Since no current is input to the quadrature axis of the motor, the motor has no additional vibration or torque. An AC current with a DC current bias is input to the direct axis or zero axis. Compared with the method in the prior art where only the end winding is used to radiate heat, the current input to the motor contains an AC component, which can effectively induce the iron loss and permanent magnet loss of the motor, and can improve the heat dissipation output of the motor, thereby improving the heating rate of the power battery. In addition, the heat released by the resistor of the motor controller 300 can also be used to heat the power battery.

[0115] An embodiment of the present application further provides a heat exchange system. As shown in Fig. 13, the heat exchange system 1300 includes a motor 1301, a heat exchanger 1302, a hydraulic pump 1303, a power battery 1304, and the above-mentioned motor controller 300. The motor 1301, the heat exchanger 1302, and the hydraulic pump 1303 are connected through pipes.

[0116] The motor controller 300 is configured to output an AC current to a direct or zero axis of the motor 1301, where the AC current has a DC current bias and the AC current is used to enable the motor 1301 to dissipate heat.

[0117] A hydraulic pump 1303 is configured to drive the pipes so that heat released by the motor 1301 is exchanged via the heat exchanger 1302 to the power battery 1304 .

[0118] The motor 1301 may be an oil-cooled motor. A schematic diagram of a possible structure of the motor 1301 may be shown in Figure 2. Certainly, the structure of another oil-cooled motor in the prior art may also be applied to this embodiment of the present application.

[0119] For the specific operation principle and connection method of the heat exchange system 1300, please refer to the related description of the heat exchange system shown in Figure 1. The details will not be described again here.

[0120] Based on the same inventive concept, an embodiment of the present application further provides a current injection method, see Fig. 14. The method includes the following steps:

[0121] S1401. The motor controller determines parameters of the AC current to be output to the motor.

[0122] The AC current has a DC current bias and is used to heat the motor.

[0123] Specifically, the parameters of the AC current include a waveform, a phase, an amplitude, a frequency, and a DC current bias value. The AC current output to the motor with the DC current bias is used to heat the motor and heat the power battery. Thus, the motor controller may determine the parameters of the AC current based on factors such as the temperature of the motor, the temperature of the power battery, and the current and temperature limits of the three-phase windings of the motor.

[0124] S1402. The motor controller outputs an AC current to a direct or zero axis of the motor.

[0125] The current injection method may be considered as a method executed by the aforementioned motor controller 300. By executing this method, the motor controller 300 can input a current to the motor to heat the motor. For a detailed implementation process of the method executed by the motor controller 300, please refer to the related description of the motor controller 300 shown in FIG. The details will not be described again here.

[0126] Based on the same inventive concept, an embodiment of the present application further provides a power assembly. As shown in Fig. 15, the power assembly 1500 includes a motor 1501, a reducer 1502, and the motor controller 300 mentioned above.

[0127] In addition, an embodiment of the present application further provides a vehicle. As shown in FIG. 16, the vehicle 1600 includes a power battery 1601 and a power assembly 1500.

[0128] Undoubtedly, those skilled in the art may make various modifications and variations to the embodiments of the present application without departing from the scope of the embodiments of the present application. The present application intends to cover these modifications and variations, provided that they fall within the scope of protection defined by the following claims and their equivalent technologies.

Claims

1. A heat exchange system having a motor, a heat exchanger, a hydraulic pump, a power battery, and a motor controller, The motor controller includes a control device and an inverter circuit. the controller is configured to control the inverter circuit to input an alternating current to the motor, the alternating current having a DC current bias, the alternating current being used to heat the motor; The inverter circuit is configured to output the AC current to a direct axis or a zero axis of the motor under the control of the control device; the motor, the heat exchanger, and the hydraulic pump are connected via a first pipe through which a first fluid flows; the hydraulic pump circulates the first fluid among the motor, the heat exchanger, and the hydraulic pump to transfer heat dissipated by the motor to the heat exchanger; the motor controller, the heat exchanger, and the power battery are connected via a second pipe through which a second fluid different from the first fluid flows; the heat exchanger is configured to transfer heat from the first fluid to the second fluid and heat the power battery with the second fluid; Heat exchange system.

2. A three-phase, three-wire system is used in the inverter circuit, the inverter circuit comprising: configured to output a first AC current having a DC current bias to the DC shaft of the motor under control of the controller; The heat exchange system of claim 1 .

3. A three-phase, four-wire system is used for the inverter circuit, which comprises: outputting a second AC current with a DC current bias to the zero axis of the motor under control of the controller, or outputting a third AC current with a DC current bias to the direct axis of the motor under control of the controller. The heat exchange system of claim 1 .

4. the inverter circuit is connected to a DC bus; a two-level topology is used for the inverter circuit, and a neutral point of the inverter circuit is connected to a positive pole of the DC bus via a first switch unit and a first inductor; or A two-level topology is used for the inverter circuit, and the neutral point of the inverter circuit is connected to the negative pole of the DC bus via a second switch unit and a second inductor; or a two-level topology is used for the inverter circuit, the neutral point of the inverter circuit is connected to the positive pole of the DC bus via a third switch unit and a third inductor, and the neutral point of the inverter circuit is connected to the negative pole of the DC bus via a fourth switch unit and a fourth inductor; The heat exchange system of claim 2 .

5. An open winding structure or a multi-level topology is used in the inverter circuit; The heat exchange system of claim 2 .

6. The AC current is one of a sine wave, a square wave, a triangular wave, a sawtooth wave, and a trapezoidal wave. The heat exchange system of claim 1 .

7. The alternating current has no negative value. The heat exchange system of claim 1 .

8. The motor controller is connected upstream of the heat exchanger, and the power battery is connected downstream of the heat exchanger. A heat exchange system according to any one of claims 1 to 7.

9. The motor is an oil-cooled motor. A heat exchange system according to any one of claims 1 to 8.

10. A method of current injection for use in a heat exchange system according to any one of claims 1 to 9, comprising the steps of: determining, by the motor controller, parameters of an alternating current to be output to the motor, the alternating current having a DC current bias, the alternating current being used to heat the motor; and outputting, by the motor controller, the AC current to the direct axis or the zero axis of the motor; method.

11. A power assembly comprising a heat exchange system according to any one of claims 1 to 9 and a reducer.

12. 10. A vehicle comprising the heat exchange system according to claim 1 and a power assembly, the power assembly comprising the motor, a reducer, and the motor controller.

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