ENGINE, CONTROL METHOD, POWER SYSTEM AND ELECTRIC VEHICLE

Description

TECHNICAL FIELD

[0001] This application relates to the field of electric vehicles, and more specifically, to an electrical machine, a control method, a power system, and an electric vehicle.BACKGROUND

[0002] Electric vehicles are vehicles powered by traction batteries. Limited by traction battery materials, traction batteries can stably exert optimal performance only at its rated cell temperature. Therefore, when an electric vehicle is to be used in an area where the cell temperature is low, the traction battery needs to be heated to the rated cell temperature.

[0003] Existing traction battery heating methods may include indirect heating and direct heating. The indirect heating refers to heating a traction battery through a heat source outside the traction battery. The direct heating refers to heating a traction battery from inside. A direct heating method currently proposed in the industry is to heat a traction battery by using an electrical machine.

[0004] However, when the existing electrical machine provides heating currents to the traction battery, severe rotor-generated heat and an electrical machine NVH (full name: Noise, Vibration, Harshness) problem may occur, which affects electrical machine life and reduces passenger comfort. Therefore, the heat generation and NVH problems of the electrical machine require an urgent solution.

[0005] WO2017 / 214232A1 discloses an electric motor which can be used for heating batteries, the stator in the motor comprises a plurality of stator windings, in one embodiment, the motor is a three-phase four-pole motor, and it can be considered that each phase winding can be divided into sub-windings according to different poles. And it discloses two ways to supply power to the stator without rotor rotation: one is to apply DC voltage / current to the stator winding, and the other is to apply the same AC drive signal to each of the phases of the stator winding. Both of these methods will make the magnetic flux of some sub-windings cancel the magnetic flux of other sub-windings.

[0006] US2011 / 048821A1 discloses a single-phase switched reluctance motor, and it shows a simple single-phase switched reluctance motor with 6 / 6 topology, in which each stator pole is wound with a winding, and it is disclosed that each phase stator winding in this application includes a first sub-winding set and a second sub-winding set. WO 2019 / 193749 A1 can be seen as the closest prior art. It discloses a battery that is self heated in a mode of the motor where stator sub-windings have a 180 degrees phase difference such that the total magnetic field of the stator is substantially zero hence not producing any torque on the rotor. Nonetheless, the sub windings are not arranged to provide alternating current to the battery so that the battery uses its internal resistance to generate heat.SUMMARY

[0007] When an existing electrical machine provides heating currents to a traction battery, severe heat is generated by a rotor, making long-term heating unsustainable. A serious electrical machine NVH (full name: Noise, Vibration, Harshness) problem also occurs, further reducing driver and passenger comfort.

[0008] An embodiment of this application provides an electrical machine, a control method, a power system, and an electric vehicle, to resolve technical problems of a large amount of heat generated by a rotor and non-compliant electrical machine NVH indicators when the electrical machine operates for providing heating currents to a traction battery.

[0009] According to a first aspect, this application provides an electrical machine, including: stator windings of M phases, where M is a positive integer, each phase stator winding includes a first sub-winding set and a second sub-winding set, and the electrical machine is used to heat a traction battery; and when the electrical machine energizes the first sub-winding set and the second sub-winding set to provide alternating currents to the traction battery, so that the traction battery uses its internal resistance to generate heat, a direction of a total magnetic field generated by the first sub-winding set is caused to be opposite to a direction of a total magnetic field generated by the second sub-winding set.

[0010] In some embodiments, the first sub-winding set includes a first sub-winding, the second sub-winding set includes a second sub-winding, a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, in the winding direction, the first sub-winding includes a head end and a tail end, and the second sub-winding includes a head end and a tail end, where when the electrical machine heats the traction battery, the tail end of the first sub-winding is connected to the tail end of the second sub-winding.

[0011] According to this embodiment, the tail end of the first sub-winding is connected to the tail end of the second sub-winding, so that the direction of a total magnetic field of the first sub-winding set is opposite to the direction of a total magnetic field generated by the second sub-winding set, magnetic fields generated by the two winding sets cancel each other out, and the air gap magnetic flux approaches zero to alleviate the heat generation and NVH problems of the electrical machine.

[0012] In some embodiments, the electrical machine further includes: M sets of intra-phase switches, where each set of intra-phase switches includes a first intra-phase switch and a second intra-phase switch; and the first intra-phase switch is connected between the tail end of the first sub-winding and the head end of the second sub-winding in one phase stator winding, and the second intra-phase switch is connected between the tail end of the first sub-winding and the tail end of the second sub-winding in the phase stator winding.

[0013] According to this embodiment, two sets of intra-phase switches are set to implement connection type switching for the first sub-winding and the second sub-winding. In this way, when the electrical machine heats the traction battery, the tail end of the first sub-winding can be connected to the tail end of the second sub-winding, so that magnetic fields generated by the two winding sets cancel each other out, and the air gap magnetic flux approaches zero to alleviate the heat generation and NVH problems of the electrical machine.

[0014] In some embodiments, the electrical machine further includes: M sets of inter-phase switches, where each set of inter-phase switches includes a first inter-phase switch and a second inter-phase switch; and the first inter-phase switch is connected between the head end of the second sub-winding of one phase stator winding and the head end of the second sub-winding of another phase stator winding, and the second inter-phase switch is connected between the tail end of the second sub-winding of the one phase stator winding and the tail end of the second sub-winding of the another phase stator winding.

[0015] According to this embodiment, two sets of inter-phase switches are set to implement connection type switching between the phase windings to adapt to different types of winding connections.

[0016] In some embodiments, the first sub-winding set includes N first sub-windings, and the second sub-winding set includes N second sub-windings, where N is an integer greater than 1, a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, in the winding direction, the first sub-winding comprises a head end and a tail end, and the second sub-winding comprises a head end and a tail end; and when the electrical machine heats the traction battery, a tail end of the i th< first sub-winding is connected to a tail end of the i th< second sub-winding, and a head end of the j th< second sub-winding is connected to a head end of the (j+1) th< first sub-winding, where 1≤i≤N, and 1≤j≤N-1.

[0017] According to this embodiment, multiple sub-windings may be set to increase heating power for the electrical machine to heat the traction battery.

[0018] In some embodiments, the electrical machine further includes a rotor; and when the electrical machine heats the traction battery, the rotor is at rest.

[0019] According to a second aspect, this application provides a heating control method, applied to the electrical machine according to any one of claims 1 to 6, where the electrical machine is connected to a traction battery through an inverter, the electrical machine includes stator windings of M phases, and each phase stator winding includes a first sub-winding and a second sub-winding, and the method includes: receiving a cell temperature of the traction battery and operating state information of the electrical machine; determining whether a heating condition is met based on the cell temperature and the operating state information; and connecting a tail end of the first sub-winding to a tail end of the second sub-winding under the condition that a determining result is yes.

[0020] In some embodiment, after the connecting a tail end of the first sub-winding to a tail end of the second sub-winding under the condition that a determining result is yes, the method further includes: controlling a state of the inverter, so that when the traction battery energizes the first sub-winding and the second sub-winding, a direction of a total magnetic field generated by the first sub-winding set is opposite to a direction of a total magnetic field generated by the second sub-winding set, wherein, a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, in the winding direction, the first sub-winding comprises a head end and a tail end, and the second sub-winding comprises a head end and a tail end.

[0021] In some embodiments, the electrical machine further includes: M sets of inter-phase switches and M sets of intra-phase switches, where each set of inter-phase switches includes a first inter-phase switch and a second inter-phase switch, and each set of intra-phase switches includes a first intra-phase switch and a second intra-phase switch; and the connecting a tail end of the first sub-winding to a tail end of the second sub-winding under the condition that a determining result is yes specifically includes: closing the second intra-phase switch in each set of intra-phase switches and the first inter-phase switch in each set of inter-phase switches.

[0022] According to a third aspect, this application provides a power system, where the system includes: a traction battery, an inverter, and the electrical machine according to the first aspect and optional solutions, and the electrical machine heats the traction battery through the inverter.

[0023] According to a fourth aspect, this application provides an electric vehicle, including a power system, where the power system includes: a traction battery, an inverter, and the electrical machine according to the first aspect and optional solutions, and the electrical machine heats the traction battery through the inverter.

[0024] This application provides an electrical machine, a control method, a power system, and an electric vehicle. The electrical machine is connected to a traction battery through an inverter. Each phase stator winding of the electrical machine includes two sub-winding sets. When the traction battery needs to be heated, the two sub-winding sets in the electrical machine serve as energy storage elements to provide alternating currents to the traction battery, so that the traction battery uses its internal resistance to generate heat. In addition, the two sub-winding sets generate opposite magnetic fields which cancel each other out, so that the strength of the magnetic fields inside the stator windings and the air gap magnetic flux are reduced, thereby alleviating the heat generation and NVH problems of the electrical machine.BRIEF DESCRIPTION OF DRAWINGS

[0025] FIG. 1 is a schematic circuit diagram of a power system of an electric vehicle according to this application; FIG. 2 is a functional block diagram of a power system according to this application; FIG. 3 is a schematic diagram of stator winding connection of an electrical machine according to a second embodiment of this application in power output mode; FIG. 4 is a schematic diagram of stator winding connection of an electrical machine according to a second embodiment of this application in heating mode; FIG. 5 is a schematic diagram of a connection between a stator winding and switches according to a third embodiment of this application; FIG. 6 is a schematic structural diagram of a stator winding according to a third embodiment of this application; FIG. 7 is a schematic diagram of stator winding connection of an electrical machine according to a fourth embodiment of this application in power output mode; and FIG. 8 is a schematic diagram of stator winding connection of an electrical machine according to a fourth embodiment of this application in heating mode. DESCRIPTION OF EMBODIMENTS

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following clearly and completely describes the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Apparently, the described embodiments are some but not all of the embodiments of this application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of this application without creative efforts shall fall within the protection scope of this application.

[0027] Electric vehicles are vehicles powered by traction batteries. As shown in FIG. 1, a power system 100 of an electric vehicle includes a traction battery 10, an inverter 20, an electrical machine 30, and an electrical machine controller unit (MCU) 40. Positive and negative electrodes of the traction battery 10 are connected to a direct current side of the inverter 300, and an alternating current side of the inverter 20 is connected to a stator winding of the electrical machine 30. When the electric vehicle is running, the traction battery 10 supplies electrical energy to the electrical machine 30 through the inverter 20, and the electrical machine outputs power to drive the vehicle. The MCU 40 has a plurality of input terminals for receiving electrical machine operating state data and an electrical machine control instruction. The MCU 40 generates a pulse width modulation (PWM) signal according to the electrical machine control instruction, the electrical machine operating state data, and traction battery operating state data, and controls the inverter to provide voltage and current to the electrical machine 30 to control an electrical machine speed, so as to control a driving speed of the vehicle.

[0028] As shown in FIG. 2, the traction battery 10 includes a battery module 101, an auxiliary structure 102, and a battery management system 103. The battery module 101 has a plurality of traction cells connected in series and parallel. The traction cells are core components of the traction battery, and also a source of electrical energy provided by the traction battery. The common auxiliary structure 102 includes an external frame, a fixture, an electrical connector, and an isolation component. Main functions of the battery management system 103 include charge and discharge management, high voltage control, battery state evaluation, battery data acquisition, and battery thermal management.

[0029] The battery management system 103 is configured to ensure that the traction battery operates within a suitable temperature range. Main functions of the battery thermal management system include accurate battery temperature measurement and monitoring, active cooling upon excessively high temperature of a battery pack, rapid heating upon excessively low temperature, for example, below a temperature threshold, and uniform temperature field distribution guarantee for the battery pack. Limited by traction battery materials, traction batteries can stably exert optimal performance only under its rated cell temperature. Therefore, when a traction battery is to be used in an environment where the cell temperature is low, the traction battery needs to be heated to the rated cell temperature.

[0030] Existing traction battery heating methods may include indirect heating and direct heating. The indirect heating refers to heating a traction battery through a heat source outside the traction battery. An indirect heating method may be air heating, liquid heating, heating using a heating film, or the like. For different heating sources, heating rates of a battery may be different. Because the battery is heated by an external heat source, heat loss occurs on a heat transfer medium, and the efficiency of indirect heating is not high. The direct heating refers to heating a traction battery from inside. A direct heating method currently proposed in the industry is to heat a traction battery by using an electrical machine.

[0031] However, when an existing electrical machine provides heating currents to a traction battery, a rotor generates severe heat, long-term heating cannot be maintained, and an electrical machine NVH problem also occurs. NVH is an abbreviation of Noise, Vibration, and Harshness. NVH is an important indicator used to measure the vehicle comfort performance.

[0032] This application provides an electrical machine, a control method, a power system, and an electric vehicle, to resolve the foregoing problems. The inventive concept of this application is: When an electrical machine is used to directly heat a battery, a conventional mode of the electrical machine changes, resulting in an extremely uneven air gap magnetic flux density distribution in the electrical machine in this mode. Consequently, a rotor generates severe heat, long-term heating cannot be maintained, and an electrical machine NVH problem also occurs. To resolve the problem of the extremely uneven magnetic flux density distribution, a stator winding is split into two sub-winding sets in this application based on the foregoing analysis. When the electrical machine outputs power, directions of magnetic fields generated by the two sub-winding sets are the same, the magnetic fields inside the electrical machine are evenly distributed to provide power to the vehicle. When the electrical machine is used as an inductor in a heating circuit of the traction battery, the directions of the magnetic fields generated by the two sub-winding sets are opposite, so that the magnetic fields cancel each other out, and the magnetic fields inside a winding of each phase are reduced, which in turn reduces the air gap magnetic flux density, and the magnetic density on the rotor becomes very low to reduce heat generated by the rotor. Electrical machine vibration is related to the non-uniform air gap magnetic flux density and distribution. Due to decrease in the air gap magnetic flux density, the electrical machine NVH problem caused by non-uniform magnetic field distribution has also been suppressed to some extent.

[0033] The following focuses on a structure of an electrical machine in a first embodiment of this application. The electrical machine in this application includes: stator windings of M phases, a stator core, and a rotor, where M is a positive integer. The stator winding is configured to be connected to an inverter.

[0034] The stator winding is wound around the stator core, and may be a concentrated winding or a distributed winding, which is not limited herein. Each phase stator winding includes a first sub-winding set and a second sub-winding set.

[0035] The electrical machine has two operating modes: heating mode and power output mode. Heating mode means that the stator winding in the electrical machine is used as an energy storage element to provide alternating currents to the traction battery, so that the traction battery uses its internal resistance to generate heat and heat itself. Power output mode refers to a case in which the electrical machine outputs mechanical power.

[0036] When the electrical machine operates in power output mode and energizes the first sub-winding set and the second sub-winding set, a direction of a total magnetic field generated by the first sub-winding set is the same as a direction of a total magnetic field generated by the second sub-winding set. The total magnetic field generated by the first sub-winding set and the total magnetic field generated by the second sub-winding set are superimposed and become stronger, and jointly interact with the rotor to output power.

[0037] When the electrical machine heats the traction battery and energizes the first sub-winding set and the second sub-winding set, a direction of a total magnetic field generated by the first sub-winding set is opposite to a direction of a total magnetic field generated by the second sub-winding set, the total magnetic field generated by the first sub-winding set and the total magnetic field generated by the second sub-winding set cancel each other out, a magnetic field generated by the stator winding approaches zero, the air gap magnetic flux density is reduced, and the magnetic density on the rotor becomes lower.

[0038] The following analyzes how the heat generated by a rotor and electrical machine vibration are reduced. The formula for calculating a rotor eddy-current loss is as follows: P C = K C f 2 B S 2 where, P C represents the rotor eddy-current loss, K C is an eddy-current loss coefficient, f is a current frequency, and B S is a rotor flux density amplitude.

[0039] Based on the foregoing formula, the rotor eddy-current loss is proportional to the second power of the rotor magnetic flux density. With the decrease in the rotor magnetic flux density, the rotor eddy-current loss is squared down, and the heating power is reduced, so that problems of rotor temperature rise and inability to keep long-term self-heating can be resolved. In addition, the electrical machine vibration is related to the uneven air gap magnetic flux density distribution. When the air gap magnetic flux density approaches zero, the electrical machine vibration noise caused by uneven magnetic field distribution is also significantly reduced.

[0040] For the electrical machine according to this embodiment of this application, when the electrical machine operates in heating mode, the two sub-winding sets generate opposite magnetic fields, and the magnetic fields cancel each other out. A total magnetic field can be controlled to be within a reasonable threshold range, so that NVH requirements can be met in a process of heating the traction battery by using the electrical machine. In addition, the NVH requirements can be met in the heating process through settings of the electrical machine, reducing the difficulty of electrical machine control.

[0041] An electrical machine according to a second embodiment of this application is described below by using an example in which the first sub-winding set and the second sub-winding set each include only one sub-winding, and a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding. The electrical machine according to this embodiment of this application includes: stator windings of M phases, a stator core, and a rotor.

[0042] Each phase stator winding includes a first sub-winding set and a second sub-winding set. The first sub-winding set includes a first sub-winding, the second sub-winding set includes a second sub-winding, and a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding. Both the first sub-winding and the second sub-winding are provided with a head end and a tail end, where an end at which winding starts or ends is taken as the head end, and the other end is called the tail end.

[0043] A head end of a first sub-winding of each phase stator winding is configured to be connected to an inverter. When the electrical machine is in power output mode, a tail end of the first sub-winding is connected to a head end of a second sub-winding. In addition, a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, so that a direction of a magnetic field generated by the first sub-winding set is the same as a direction of a magnetic field generated by the second sub-winding set. The magnetic fields generated by the two sub-windings are superimposed, a magnetic field generated by the stator winding interacts with a magnetic field generated by the rotor, and the rotor is driven to rotate to output power.

[0044] When the electrical machine is in heating mode, the electrical machine rotor is fixed, so that the tail end of the first sub-winding is connected to the tail end of the second sub-winding. The electrical machine controller unit inputs a PWM signal to a control terminal of the inverter, and a closed circuit is formed by the traction battery, the inverter, and the stator winding, where the stator winding stores electrical energy. Due to the inductance characteristic of the stator winding, the stator winding applies alternating current excitation to the battery, and the traction battery uses its own internal resistance for heating. Because the tail end of the first sub-winding is connected to the tail end of the second sub-winding, and the wire winding direction of the first sub-winding is the same as the wire winding direction of the second sub-winding, a direction of a magnetic field generated by the first sub-winding set is opposite to a direction of a magnetic field generated by the second sub-winding set, the magnetic fields generated by the two sub-windings cancel each other out, a magnetic field generated by the stator winding approaches zero, the air gap magnetic flux density is reduced, and the magnetic density on the rotor becomes lower.

[0045] In some embodiments, the number of turns of each first sub-winding is the same as the number of turns of each second sub-winding, and the first sub-winding and the second sub-winding may be wound with a same type of wire. With the foregoing settings, a total magnetic field in the first sub-winding set and a total magnetic field in the second sub-winding set may be entirely canceled, the magnetic flux density of the air gap approaches zero, and an amount of heat generated by the rotor may approach zero. It should be noted that the first sub-winding and the second sub-winding alternatively may be wound with different types of wire. The number of turns of the first sub-winding may alternatively be different from that of the second sub-winding, which is not limited herein.

[0046] The following describes the stator windings of the electrical machine by using a three-phase electrical machine as an example. The stator windings are wound according to a conventional wire winding method. The phase A winding, the phase B winding, and the phase C winding each need to be divided into two sub-windings. The division may be performed by cutting off each phase winding, or each phase winding can be divided into two sub-windings and wound during the winding process. As shown in FIG. 3, a divided phase A winding includes a first sub-winding A1X1 and a second sub-winding A2X2, a divided phase B winding includes a first sub-winding B1Y1 and a second sub-winding B2Y2, and a divided phase C winding includes a first sub-winding C1Z1 and a second sub-winding C2Z2.

[0047] Still referring to FIG. 3, when the electrical machine operates in power output mode, the sub-windings in each phase winding are connected in series. A tail end X1 of the first sub-winding A1X1 is connected to a head end A2 of the second sub-winding A2X2, a tail end Y1 of the first sub-winding B1Y1 is connected to a head end B2 of the second sub-winding B2Y2, and a tail end Z1 of the first sub-winding C1Z1 is connected to a head end C2 of the second sub-winding C2Z2. A direction of a magnetic field generated by the first sub-winding set is the same as a direction of a magnetic field generated by the second sub-winding set. The magnetic fields generated by the two sub-windings are superimposed, a magnetic field generated by the stator winding interacts with a magnetic field generated by the rotor, and the rotor is driven to rotate to output power.

[0048] As shown in FIG. 4, when the electrical machine operates in heating mode, the sub-windings of each phase winding are connected in parallel. A tail end X1 of the first sub-winding A1X1 is connected to a tail end X2 of the second sub-winding A2X2, a tail end Y1 of the first sub-winding B1Y1 is connected to a tail end Y2 of the second sub-winding B2Y2, and a tail end Z1 of the first sub-winding C1Z1 is connected to a tail end Z2 of the second sub-winding C2Z2. A direction of a magnetic field generated by the first sub-winding set is opposite to a direction of a magnetic field generated by the second sub-winding set. The magnetic fields generated by the two sub-windings entirely or partially cancel each other out, magnetic fields generated by the stator windings are reduced, the air gap magnetic flux density is reduced, the magnetic density on the rotor is reduced, and electrical machine vibration and heat generated by the rotor are reduced accordingly. When the magnetic fields generated by the two windings are theoretically entirely canceled by setting the number of turns and the wires of the two sub-windings, the magnetic fields generated by the stator windings approach zero, the magnetic density on the rotor can be ignored, and electrical machine vibration and heat generated by the rotor are significantly reduced.

[0049] In some embodiments, when the electrical machine operates in heating mode, the two sub-winding sets generate opposite magnetic fields, the magnetic fields are entirely canceled, the strength of the magnetic field inside each phase stator winding approaches zero, the air gap magnetic flux is reduced, and electrical machine vibration and heat generated by the rotor are reduced accordingly.

[0050] For the electrical machine according to this embodiment of this application, when the electrical machine operates in heating mode, the first sub-winding and the second sub-winding generate opposite magnetic fields which cancel each other out. A total magnetic field is controlled to be within a reasonable threshold range, so that NVH requirements can be met in a process of heating the traction battery by using the electrical machine. In addition, the NVH requirements can be met in the heating process through settings of the electrical machine, reducing the difficulty of electrical machine control.

[0051] The following focuses on a structure of an electrical machine in a third embodiment of this application. The electrical machine in this embodiment of this application includes stator windings of M phases. Different from the electrical machine in the first embodiment, the electrical machine in this embodiment further includes: M sets of intra-phase switches and M sets of inter-phase switches, where each set of intra-phase switches includes a first intra-phase switch and a second intra-phase switch; and each set of inter-phase switches includes a first inter-phase switch and a second inter-phase switch.

[0052] The first intra-phase switch is connected between a tail end of a first sub-winding and a head end of a second sub-winding in one phase stator winding, and the second intra-phase switch is connected between the tail end of the first sub-winding and a tail end of the second sub-winding in the phase stator winding. The first inter-phase switch is connected between a head end of a second sub-winding of one phase stator winding and a head end of a second sub-winding of another phase stator winding, and the second inter-phase switch is connected between a tail end of the second sub-winding of the one phase stator winding and a tail end of the second sub-winding of the another phase stator winding.

[0053] The electrical machine further includes an electrical machine controller unit. The electrical machine controller unit is configured to control the M sets of intra-phase switches and the M sets of inter-phase switches to close or open, implementing connection type switching for the first sub-winding and the second sub-winding.

[0054] When the electrical machine operates in power output mode, the electrical machine controller unit closes the first intra-phase switch in each set of intra-phase switches and the second inter-phase switch in each set of inter-phase switches, and the tail end of the first sub-winding is connected to the head end of the second sub-winding. A direction of a magnetic field generated by the first sub-winding set is the same as a direction of a magnetic field generated by the second sub-winding set. The magnetic fields generated by the two sub-windings are superimposed, a magnetic field generated by the stator winding interacts with a magnetic field generated by the rotor, and the rotor is driven to rotate to output power.

[0055] When the electrical machine operates in heating mode, the electrical machine controller unit closes the second intra-phase switch in each set of intra-phase switches and the first inter-phase switch in each set of inter-phase switches, and the tail end of the first sub-winding is connected to the tail end of the second sub-winding. A direction of a magnetic field generated by the first sub-winding set is opposite to a direction of a magnetic field generated by the second sub-winding set. The magnetic fields generated by the two sub-windings are canceled, and a magnetic field generated by the stator winding approaches zero, which in turn reduces the air gap magnetic flux density and the magnetic density on the rotor, thereby reducing electrical machine vibration and heat generated by the rotor.

[0056] The following describes a switch switching process by using a three-phase electrical machine as an example. As shown in FIG. 5 and FIG. 6, head ends of the first sub-windings A1X1 of phase A, phase B, and phase C are connected to a traction battery through an inverter, and the first intra-phase switch K1 is connected between the tail end of the first sub-winding A1X1 and the head end A2 of the second sub-winding A2X2 in the phase A winding, and the second intra-phase switch K2 is connected between the tail end of the first sub-winding A1X1 and the tail end X2 of the second sub-winding A2X2 in the phase A winding. The switch connection types in phase B and phase C are the same as that in phase A, and details are not described herein again.

[0057] The first inter-phase switch K3 is connected between the head end A2 of the second sub-winding A2X2 of the phase A stator winding and the head end B2 of the second sub-winding B2Y2 of the phase B stator winding. The second inter-phase switch K4 is connected between the tail end X2 of the second sub-winding A2X2 of the phase A stator winding and the tail end of the second sub-winding B2Y2 of the phase B stator winding. The switch connection types between phase B and phase C and between phase A and phase C are the same as the switch connection type between phase A and phase B, and details are not described herein again.

[0058] When the electrical machine operates in power output mode, the first intra-phase switch K1 in each set of intra-phase switches and the second inter-phase switch K4 in each set of inter-phase switches are closed, so that the tail end of the first sub-winding is connected to the head end of the second sub-winding, the tail ends of the second sub-windings of the phases are connected to each other, and the head ends of the first sub-windings of the phases are connected to the traction battery through the inverter. When the electrical machine operates in heating mode, the second intra-phase switch K2 in each set of intra-phase switches and the first inter-phase switch K3 in each set of inter-phase switches are closed, so that the tail end of the first sub-winding is connected to the tail end of the second sub-winding, the head ends of the second sub-windings of the phases are connected to each other, and the head ends of the first sub-windings of the phases are connected to the traction battery through the inverter.

[0059] For the electrical machine according to this embodiment of this application, when the electrical machine operates in heating mode, the second intra-phase switch in each set of intra-phase switches and the first inter-phase switch in each set of inter-phase switches are closed, so that the tail end of the first sub-winding is connected to the tail end of the second sub-winding. The two sub-winding sets generate opposite magnetic fields, the magnetic fields are canceled, the strength of the magnetic field inside each phase stator winding approaches zero, and the air gap magnetic flux is reduced to reduce electrical machine vibration and heat generated by the rotor.

[0060] The following focuses on a structure of an electrical machine in a fourth embodiment of this application. The electrical machine in this application includes: stator windings of M phases, a stator core, and a rotor. Different from the electrical machine in the second embodiment, a first sub-winding set includes N first sub-windings, and a second sub-winding set includes N second sub-windings, where N is an integer greater than 1. To be specific, the first sub-winding set includes two or more first sub-windings, and the second sub-winding set includes two or more second sub-windings.

[0061] When the electrical machine operates in power output mode, a tail end of the i th< first sub-winding is connected to a head end of the i th< second sub-winding, and a tail end of the j th< second sub-winding is connected to a head end of the (j+1) th< first sub-winding, where 1≤i≤N, and 1≤j≤N-1. A wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, a direction of a magnetic field generated by the i th< first sub-winding is the same as a direction of a magnetic field generated by the i th< second sub-winding, and the magnetic fields are superimposed and become stronger to generate mechanical power.

[0062] When the electrical machine operates in heating mode, a tail end of the i th< first sub-winding is connected to a tail end of the i th< second sub-winding, and a head end of the j th< second sub-winding is connected to a head end of the (j+1) th< first sub-winding, where 1≤i≤N, and 1≤j≤N-1. A wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, a direction of a magnetic field generated by the i th< first sub-winding is opposite to a direction of a magnetic field generated by the i th< second sub-winding, and the magnetic fields cancel each other out, and the magnetic fields inside each phase stator winding are reduced.

[0063] The following takes N=2 as an example, and describes the connection types of the sub-windings with reference to FIG. 7 and FIG. 8. The divided phase A winding includes the 1 st< first sub-winding A11X11 and the 2 nd< first sub-winding A12X12, and the 1 st< second sub-winding A21X21 and the 2 nd< second sub-winding A22X22. The divided phase B winding includes the 1 st< first sub-winding B11Y11 and the 2 nd< first sub-winding B12Y12, and the 1 st< second sub-winding B21Y21 and the 2 nd< second sub-winding B22Y22. The divided phase C winding includes the 1 st< first sub-winding C11Z11 and the 2 nd< first sub-winding C12Z12, and the 1 st< second sub-winding C21Z21 and the 2 nd< second sub-winding C22Z22.

[0064] Still referring to FIG. 7, when the electrical machine operates in power output mode, the sub-windings in each phase winding are connected in series. A tail end X11 of the 1 st< first sub-winding A11X11 is connected to a head end A21 of the 1 st< second sub-winding A21X21, a tail end X21 of the 1 st< second sub-winding A21X21 is connected to a head end A12 of the 2 nd< first sub-winding A12X12, and a tail end X12 of the 2 nd< first sub-winding A12X12 is connected to a head end A22 of the 2 nd< second sub-winding A22X22. The connection types in phase B and phase C are the same as that in phase A, and details are not described herein again. A direction of a magnetic field generated by the first sub-winding set is the same as a direction of a magnetic field generated by the second sub-winding set. The magnetic fields generated by the two sub-windings are superimposed and become stronger, a magnetic field generated by the stator winding interacts with a magnetic field generated by the rotor, and the rotor is driven to rotate to output power.

[0065] As shown in FIG. 8, when the electrical machine operates under the heat mode, the tail end X11 of the 1 st< first sub-winding A11X11 is connected to the tail end X21 of the 1 st< second sub-winding A21X21, the head end A21 of the 1 st< second sub-winding A21X21 is connected to the head end A12 of the 2 nd< first sub-winding A12X12, and the tail end X12 of the 2 nd< first sub-winding A12X12 is connected to a tail end X22 of the 2 nd< second sub-winding A22X22. The connection types in phase B and phase C are the same as that in phase A, and details are not described herein again. A direction of a magnetic field generated by the first sub-winding set is opposite to a direction of a magnetic field generated by the second sub-winding set, the magnetic fields generated by the two sub-windings are canceled, and the magnetic fields generated by the stator winding are reduced, which in turn reduces the air gap magnetic flux density and the magnetic density on the rotor, thereby reducing electrical machine vibration and heat generated by the rotor.

[0066] For the electrical machine according to this embodiment of this application, when the electrical machine operates in heating mode, the two sub-winding sets generate opposite magnetic fields, and the magnetic fields are canceled, so that the strength of the magnetic field inside each phase stator winding approaches zero, which in turn reduces the air gap magnetic flux, thereby reducing electrical machine vibration and heat generated by the rotor.

[0067] The following focuses on a heating control method in a fifth embodiment of this application. The control method includes the following steps.

[0068] S201. Obtain a cell temperature of a traction battery and operating state information of an electrical machine.

[0069] The cell temperature of the traction battery is acquired by a temperature sensor disposed inside the traction battery.

[0070] In some embodiments, the traction battery includes a battery management system. The battery management system obtains a traction battery temperature, and transmits battery temperature information to an electrical machine controller unit, where the electrical machine includes the electrical machine controller unit. The electrical machine controller unit receives the battery temperature information.

[0071] In some embodiments, the electrical machine controller unit also receives the operating state information of the electrical machine. The operating state information of the electrical machine includes: a temperature of an electrical machine stator, a temperature of an electrical machine stator winding, the electrical machine being in heating mode or power output mode, the electrical machine being in a locked-rotor state, and / or the electrical machine being in a stopped state, which are not specifically limited herein.

[0072] S202. Determine whether the cell temperature and the operating state of the electrical machine satisfy a heating condition. Under the condition that a determining result is yes, go to S203; otherwise, go to S204 or keep the electrical machine in the stopped state.

[0073] In some embodiments, the heating condition includes that the cell temperature of the traction battery is lower than a preset temperature threshold and the electrical machine is in the locked-rotor state, where the preset temperature threshold is determined based on a rated operating temperature of the traction battery.

[0074] In some embodiments, the heating condition includes that the cell temperature of the traction battery is lower than a preset temperature threshold and the electrical machine is in the stopped state.

[0075] In some embodiments, the heating condition includes that the cell temperature of the traction battery is lower than a preset temperature threshold, the electrical machine is in the locked-rotor state, and a temperature of the electrical machine stator and a temperature of the electrical machine stator winding are lower than a preset electrical machine temperature threshold, where the preset electrical machine temperature threshold is determined based on the rated operating temperature of the traction battery.

[0076] A person skilled in the art should understand that the heating condition can be set based on needs, which is not limited herein.

[0077] S203. Connect a tail end of the first sub-winding to a tail end of the second sub-winding.

[0078] The second intra-phase switch is connected between a tail end of a first sub-winding and a tail end of a second sub-winding in one phase stator winding. The first inter-phase switch is connected between a head end of a second sub-winding of one phase stator winding and a head end of a second sub-winding of another phase stator winding. The electrical machine controller unit controls to close the second intra-phase switch in each set of intra-phase switches and the first inter-phase switch in each set of inter-phase switches, so that the tail end of the first sub-winding is connected to the tail end of the second sub-winding.

[0079] S204. Connect the tail end of the first sub-winding to the head end of the second sub-winding.

[0080] The first intra-phase switch is connected between a tail end of a first sub-winding and a head end of a second sub-winding in one phase stator winding, and the second inter-phase switch is connected between a tail end of the second sub-winding of the one phase stator winding and a tail end of the second sub-winding of the another phase stator winding. The electrical machine controller unit controls to close the first intra-phase switch in each set of intra-phase switches and the second inter-phase switch in each set of inter-phase switches, so that the tail end of the first sub-winding is connected to the tail end of the second sub-winding.

[0081] In the heating control method according to this embodiment of this application, when the electrical machine operates in heating mode, the second intra-phase switch in each set of intra-phase switches and the first inter-phase switch in each set of inter-phase switches are closed, so that the tail end of the first sub-winding is connected to the tail end of the second sub-winding. When the first sub-winding and the second sub-winding are energized, the two sub-winding sets generate opposite magnetic fields, the magnetic fields are canceled, the strength of the magnetic field inside each phase stator winding is reduced, and the air gap magnetic flux is reduced, thereby reducing electrical machine vibration and heat generated by the rotor.

[0082] In some embodiments, after S203, the foregoing method further includes S205.

[0083] S205. Control a state of the inverter, so that the battery energizes the first sub-winding and the second sub-winding, and a direction of a total magnetic field generated by the first sub-winding set is opposite to a direction of a total magnetic field generated by the second sub-winding set.

[0084] The inverter includes a switch assembly, and the stator winding of the electrical machine is connected to the traction battery through the switch assembly. The electrical machine controller unit controls on / off state of the switch assembly. When a closed circuit is formed by the battery and one phase stator winding or stator windings of M phases, the phase stator winding or windings store electrical energy. When the circuit formed by the battery and the phase stator winding or the stator windings of M phases is disconnected, due to the inductance characteristic of the stator winding, the phase stator winding or the stator windings of M phases further apply currents to the battery, so that alternating current excitation is generated in the circuit connecting the stator windings of M phases and the battery, and the traction battery uses its internal resistance for heating. In this case, because the tail end of the first sub-winding is connected to the tail end of the second sub-winding, directions of magnetic fields generated by the first sub-winding set and the second sub-winding set are opposite. Through the settings of the number of turns and the wires of the first sub-winding and the second sub-winding, the magnetic fields can be entirely or partially canceled, the strength of the magnetic field inside each phase stator winding is reduced, and the air gap magnetic flux is reduced, thereby reducing electrical machine vibration and heat generated by the rotor.

[0085] In conclusion, it should be noted that the foregoing embodiments are merely intended for describing the technical solutions of this application but not for limiting this application. The scope of the invention is defined only by the appended claims.

Claims

1. An electrical machine (30), comprising: stator windings of M phases, wherein M is a positive integer, each phase stator winding comprises a first sub-winding set and a second sub-winding set, wherein the electrical machine is a motor which can be selectively used in a power output mode or in a heating mode to heat a traction battery (10); and in the heating mode the electrical machine (30) is adapted to energize the first sub-winding set and the second sub-winding set to provide alternating currents to the traction battery (10), so that the traction battery (10) uses its internal resistance to generate heat, a direction of a total magnetic field generated by the first sub-winding set is caused to be opposite to a direction of a total magnetic field generated by the second sub-winding set such that their magnetic fields cancel each other out and the magnetic field generated by the stator windings approaches zero in the heating mode.

2. The electrical machine (30) according to claim 1, characterized in that the first sub-winding set comprises a first sub-winding, the second sub-winding set comprises a second sub-winding, a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, in the winding direction, the first sub-winding comprises a head end and a tail end, and the second sub-winding comprises a head end and a tail end, wherein when the electrical machine (30) heats the traction battery (10), the tail end of the first sub-winding is connected to the tail end of the second sub-winding.

3. The electrical machine (30) according to claim 2, characterized in that the electrical machine (30) further comprises: M sets of intra-phase switches, wherein each set of intra-phase switches comprises a first intra-phase switch and a second intra-phase switch; and the first intra-phase switch is connected between the tail end of the first sub-winding and the head end of the second sub-winding in one phase stator winding, and the second intra-phase switch is connected between the tail end of the first sub-winding and the tail end of the second sub-winding in the phase stator winding.

4. The electrical machine (30) according to claim 2 or 3, characterized in that the electrical machine (30) further comprises M sets of inter-phase switches, wherein each set of inter-phase switches comprises a first inter-phase switch and a second inter-phase switch; and the first inter-phase switch is connected between the head end of the second sub-winding of one phase stator winding and the head end of the second sub-winding of another phase stator winding, and the second inter-phase switch is connected between the tail end of the second sub-winding of the one phase stator winding and the tail end of the second sub-winding of the another phase stator winding.

5. The electrical machine (30) according to claim 1, characterized in that the first sub-winding set comprises N first sub-windings, and the second sub-winding set comprises N second sub-windings, wherein N is an integer greater than 1, a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, in the winding direction, the first sub-winding comprises a head end and a tail end, and the second sub-winding comprises a head end and a tail end; and when the electrical machine (30) heats the traction battery (10), a tail end of the ith first sub-winding is connected to a tail end of the ith second sub-winding, and a head end of the jth second sub-winding is connected to a head end of the (j+1)th first sub-winding, wherein 1≤i≤N, and 1≤j≤N-1.

6. The electrical machine (30) according to any one of claims 1 to 5, characterized in that the electrical machine (30) further comprises a rotor; and when the electrical machine (30) heats the traction battery (10), the rotor is at rest.

7. A heating control method, characterized in that the method is applied to the electrical machine (30) according to any one of claims 1 to 6, the electrical machine (30) is connected to a traction battery (10) through an inverter (20), the electrical machine (30) comprises stator windings of M phases, each phase stator winding comprises a first sub-winding and a second sub-winding, and the method comprises: receiving a cell temperature of the traction battery (10) and operating state information of the electrical machine (30); determining whether a heating condition is met based on the cell temperature and the operating state information; and connecting a tail end of the first sub-winding to a tail end of the second sub-winding under the condition that a determining result is yes.

8. The method according to claim 7, characterized in that after the connecting a tail end of the first sub-winding to a tail end of the second sub-winding under the condition that a determining result is yes, the method further comprises: controlling a state of the inverter (20), so that when the traction battery (10) energizes the first sub-winding and the second sub-winding, a direction of a total magnetic field generated by the first sub-winding set is opposite to a direction of a total magnetic field generated by the second sub-winding set, wherein, a wire winding direction of the first sub-winding is the same as a wire winding direction of the second sub-winding, in the winding direction, the first sub-winding comprises a head end and a tail end, and the second sub-winding comprises a head end and a tail end.

9. The method according to claim 7, characterized in that the electrical machine (30) further comprises: M sets of inter-phase switches and M sets of intra-phase switches, wherein each set of inter-phase switches comprises a first inter-phase switch and a second inter-phase switch, and each set of intra-phase switches comprises a first intra-phase switch and a second intra-phase switch; and the connecting a tail end of the first sub-winding to a tail end of the second sub-winding under the condition that a determining result is yes specifically comprises: closing the second intra-phase switch in each set of intra-phase switches and the first inter-phase switch in each set of inter-phase switches.

10. A power system, characterized in that the system comprises: a traction battery (10), an inverter (20), and the electrical machine (30) according to any one of claims 1 to 6, wherein the electrical machine (30) heats the traction battery (10) through the inverter (20).

11. An electric vehicle, characterized by comprising a power system, wherein the power system comprises: a traction battery (10), an inverter (20), and the electrical machine (30) according to any one of claims 1 to 6, wherein the electrical machine (30) heats the traction battery (10) through the inverter (20).