A permanent magnet synchronous motor and a control method thereof

Abstract

The present invention discloses a permanent magnet synchronous motor and a control method thereof. The permanent magnet synchronous motor comprises: a first inverter, a second inverter, a first three-phase winding, a second three-phase winding, a winding switch conversion component and a three-phase uncontrolled rectifier bridge. One end of the first three-phase winding is connected to the first inverter, the other end of the first three-phase winding is respectively connected to one end of the winding switch conversion component and the three-phase uncontrolled rectifier bridge, and the second three-phase winding is respectively connected to the second inverter and the other end of the winding switch conversion component. The present invention enables the motor to switch winding working modes at low speed, medium speed and high speed through the winding switch conversion component and the three-phase uncontrolled rectifier bridge, so that the motor can adopt maximum torque current ratio control under low speed, medium speed and high speed working conditions, improves the efficiency when running at low speed and high speed, and does not need weak magnetic speed regulation under high speed working conditions, avoids irreversible demagnetization of permanent magnets during weak magnetic control, and improves the service life of the motor.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and in particular to a permanent magnet synchronous motor and a control method thereof. Background Art

[0002] Although traditional permanent magnet synchronous motors perform well under the rated operating conditions, their performance is limited when operating under multiple operating conditions with a wide speed range (including low and high speed ranges). Specifically, since the motor windings and permanent magnet excitation magnetic field are fixed after manufacturing, the efficiency of the motor will be reduced when it runs at a speed that deviates from the rated operating point. Especially in the high-speed operating range, when the motor's back electromotive force approaches or exceeds the inverter's bus voltage, a weak magnetic control strategy must be used to further increase the speed.

[0003] Although weak magnetic field control can effectively expand the speed regulation range of the motor, its side effects cannot be ignored. As the weak magnetic field current increases, the reactive power of the motor increases, which not only directly reduces the overall efficiency of the system, but also may generate additional heat due to excessive current, affecting the stable operation of the motor. More seriously, the increase in weak magnetic field current will also increase the risk of irreversible demagnetization of the permanent magnet, which will seriously damage the performance and life of the motor in the long run. Summary of the invention

[0004] The purpose of the present invention is to provide a permanent magnet synchronous motor and a control method thereof, aiming to solve the problems that the existing permanent magnet synchronous motor has poor efficiency when running at low and high speeds, and requires weak magnetic speed regulation under high-speed conditions, which significantly increases the risk of irreversible demagnetization of the permanent magnet.

[0005] An embodiment of the present invention provides a permanent magnet synchronous motor, comprising: a first inverter, a second inverter, a first three-phase winding, a second three-phase winding, a winding switch conversion component and a three-phase uncontrolled rectifier bridge, wherein one end of the first three-phase winding is connected to the first inverter, the other end of the first three-phase winding is respectively connected to one end of the winding switch conversion component and the three-phase uncontrolled rectifier bridge, the second three-phase winding is respectively connected to the second inverter and the other end of the winding switch conversion component, and the winding switch conversion component is used to realize the first three-phase winding and the second three-phase winding working in series, or the first three-phase winding and the second three-phase winding working separately.

[0006] Furthermore, the winding switch conversion component includes three conversion switches, the common end of each winding in the first three-phase winding and the lead end of each winding in the second three-phase winding are respectively connected through a conversion switch, the lead ends of the three windings in the first three-phase winding are all connected to the first inverter, the common ends of the three windings in the first three-phase winding are all connected to the three-phase uncontrolled rectifier bridge, the lead ends of the three windings in the second three-phase winding are all connected to the second inverter, and the common ends of the three windings in the second three-phase winding are connected together and serve as a neutral point.

[0007] Furthermore, it also includes: a control switch, the common anode of the three-phase uncontrolled rectifier bridge is connected to one end of the control switch, the common cathode of the three-phase uncontrolled rectifier bridge is connected to the other end of the control switch, and the three-phase input ends of the three-phase uncontrolled rectifier bridge are respectively connected to the common ends of the three windings in the first three-phase winding.

[0008] Furthermore, the conversion switch and the control switch both adopt contactors or power electronic switches.

[0009] Furthermore, it also includes: a stator core, on which a plurality of stator teeth are arranged, and each of the stator teeth is wound with a coil of the first three-phase winding and a coil of the second three-phase winding.

[0010] Further, the stator tooth portion is provided with a first stator tooth portion, an eighth stator tooth portion, a second stator tooth portion and a seventh stator tooth portion corresponding to one winding A in the first three-phase winding and one winding a in the second three-phase winding; the first stator tooth portion and the second stator tooth portion are arranged adjacent to each other, and the seventh stator tooth portion and the eighth stator tooth portion are arranged adjacent to each other; the first stator tooth portion and the seventh stator tooth portion are arranged opposite to each other, and the second stator tooth portion and the eighth stator tooth portion are arranged opposite to each other;

[0011] A coil A1 of the winding A and a coil a1 of the winding a are wound on the first stator tooth; a coil A2 of the winding A and a coil a2 of the winding a are wound on the second stator tooth; the coil A1 and the coil A2 are connected in reverse series, and the coil a1 and the coil a2 are connected in reverse series;

[0012] A coil A3 of the winding A and a coil a3 of the winding a are wound on the seventh stator tooth, and the coil A3 and the coil a3 are connected in series in reverse order;

[0013] A coil A4 of the winding A and a coil a4 of the winding a are wound on the eighth stator tooth portion, and the coil A4 and the coil a4 are connected in series in reverse order;

[0014] The coil A1, coil A2, coil A3 and coil A4 are connected in series, and the coil a1, coil a2, coil a3 and coil a4 are connected in series.

[0015] Furthermore, the first three-phase winding and the second three-phase winding have different numbers of turns.

[0016] Furthermore, the wire diameters of the first three-phase winding and the second three-phase winding are the same.

[0017] Furthermore, the maximum supply voltage of the first inverter is equal to the maximum supply voltage of the second inverter.

[0018] Furthermore, the back electromotive force of the permanent magnet synchronous motor is smaller than the maximum supply voltage of the first inverter, and the permanent magnet synchronous motor adopts maximum torque-to-current ratio control.

[0019] An embodiment of the present invention provides a control method for a permanent magnet synchronous motor, comprising: when the speed of the permanent magnet synchronous motor is less than or equal to a first speed threshold, controlling the three-phase uncontrolled rectifier bridge to be disconnected, the winding switch conversion component to be turned on, the first inverter to be turned on, and the second inverter to be turned off;

[0020] When the speed of the permanent magnet synchronous motor is greater than a first speed threshold and less than or equal to a second speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be turned on, the winding switch conversion component is disconnected, the first inverter is turned on, and the second inverter is turned on;

[0021] When the speed of the permanent magnet synchronous motor is greater than the second speed threshold and less than or equal to the third speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be turned on, the winding switch conversion component is disconnected, the first inverter is turned off, and the second inverter is turned on, wherein the first speed threshold is less than the second speed threshold, and the second speed threshold is less than the third speed threshold.

[0022] The present invention discloses a permanent magnet synchronous motor and a control method thereof. The permanent magnet synchronous motor comprises: a first inverter, a second inverter, a first three-phase winding, a second three-phase winding, a winding switch conversion component and a three-phase uncontrolled rectifier bridge. One end of the first three-phase winding is connected to the first inverter, and the other end of the first three-phase winding is respectively connected to one end of the winding switch conversion component and the three-phase uncontrolled rectifier bridge. The second three-phase winding is respectively connected to the second inverter and the other end of the winding switch conversion component. The winding switch conversion component is used to realize the first three-phase winding and the second three-phase winding working in series, or the first three-phase winding and the second three-phase winding working separately. The present invention uses a winding switch conversion component and a three-phase uncontrolled rectifier bridge to enable the motor to switch between low-speed, medium-speed and high-speed winding working modes, so that the motor can adopt maximum torque current ratio control under low-speed, medium-speed and high-speed working conditions, thereby improving the efficiency of the motor when running at low and high speeds. The motor does not need weak magnetic speed regulation under high-speed conditions, avoiding irreversible demagnetization of permanent magnets during weak magnetic control, and improving the service life of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0024] Figure 1 is a circuit diagram of a permanent magnet synchronous motor;

[0025] Figure 2 It is a structural schematic diagram of a permanent magnet synchronous motor;

[0026] Figure 3 This is a schematic diagram of one quarter of the structure of a permanent magnet synchronous motor;

[0027] Figure 4 It is another 1 / 4 structural schematic diagram of the permanent magnet synchronous motor;

[0028] Figure 5 A slot potential star diagram of a permanent magnet synchronous motor according to an embodiment;

[0029] Figure 6 is a flow chart of a control method for a permanent magnet synchronous motor;

[0030] Description of the markings in the figure:

[0031] 1. stator core; 2. stator tooth; 3. first stator tooth; 4. second stator tooth; 5. seventh stator tooth; 6. eighth stator tooth. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more of the features, integers, steps, operations, elements, components and / or combinations thereof.

[0034] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0035] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0036] See also Figure 1 This embodiment provides a permanent magnet synchronous motor including: a first inverter, a second inverter, a first three-phase winding, a second three-phase winding, a winding switch conversion component and a three-phase uncontrolled rectifier bridge, one end of the first three-phase winding is connected to the first inverter, the other end of the first three-phase winding is respectively connected to one end of the winding switch conversion component and the three-phase uncontrolled rectifier bridge, the second three-phase winding is respectively connected to the second inverter and the other end of the winding switch conversion component, and the winding switch conversion component is used to realize the first three-phase winding and the second three-phase winding working in series, or the first three-phase winding and the second three-phase winding working separately.

[0037] This embodiment uses a winding switch conversion component and a three-phase uncontrolled rectifier bridge to enable the motor to switch between low-speed, medium-speed and high-speed winding operating modes, so that the motor can adopt maximum torque current ratio control under low-speed, medium-speed and high-speed operating conditions, thereby improving the efficiency of the motor when running at low and high speeds. The motor does not need weak magnetic speed regulation under high-speed conditions, avoiding irreversible demagnetization of permanent magnets during weak magnetic control, thereby improving the service life of the motor.

[0038] In this embodiment, the winding switch conversion component includes three conversion switches, and the common end of each winding in the first three-phase winding is connected to the lead end of each winding in the second three-phase winding through a conversion switch respectively. The lead ends of the three windings in the first three-phase winding are all connected to the first inverter, and the common ends of the three windings in the first three-phase winding are all connected to the three-phase uncontrolled rectifier bridge. The lead ends of the three windings in the second three-phase winding are all connected to the second inverter, and the common ends of the three windings in the second three-phase winding are connected together and serve as a neutral point.

[0039] Specifically, the first three-phase winding includes: winding B, winding C and winding D, the second three-phase winding includes: winding b, winding c and winding d, the winding switch conversion component includes a conversion switch S2, a conversion switch S3 and a conversion switch S4, winding B is connected to winding b through the conversion switch S2, winding C is connected to winding c through the conversion switch S3, and winding D is connected to winding d through the conversion switch S4. The lead ends of winding B, winding C and winding D are all connected to the first inverter, and the common ends of winding B, winding C and winding D are all connected to the three-phase uncontrolled rectifier bridge. The three-phase uncontrolled rectifier bridge can control the first three-phase winding to switch between the star-connected neutral point and the open winding. The lead ends of winding b, winding c and winding d are all connected to the second inverter, and the common ends of winding b, winding c and winding d are connected together and serve as the neutral point, wherein the first three-phase winding and the second three-phase winding are both star-connected.

[0040] The common ends of windings B, C and D are connected together as a neutral point through a three-phase uncontrolled rectifier bridge, and then the first three-phase winding and the first inverter are disconnected to form a first three-phase system with an independent neutral point, and the second three-phase winding and the second inverter are also connected to form a second three-phase system with an independent neutral point. The independence of the neutral points of the first three-phase system and the second three-phase system enables the system to switch to another three-phase system when a fault occurs in one of the three-phase systems, thereby improving the fault tolerance of the motor.

[0041] In this embodiment, it also includes: a control switch S1, a common anode of the three-phase uncontrolled rectifier bridge is connected to one end of the control switch S1, a common cathode of the three-phase uncontrolled rectifier bridge is connected to the other end of the control switch S1, and the three-phase input ends of the three-phase uncontrolled rectifier bridge are respectively connected to the common ends of the three windings in the first three-phase winding.

[0042] Specifically, the three-phase uncontrolled rectifier bridge is composed of six diodes, each two diodes form a layer, and there are three layers in total. The positive electrode of the diode on the left side of each layer is connected to the negative electrode of the diode on the right side. The negative electrodes of the diodes on the left side of the three layers (that is, the common anode of the three-phase uncontrolled rectifier bridge) are all connected to one end of the control switch S1, and the positive electrodes of the diodes on the right side of the three layers (that is, the common cathode of the three-phase uncontrolled rectifier bridge) are all connected to the other end of the control switch S1. The common ends of winding B, winding C, and winding D are respectively connected between the two diodes in the corresponding layer.

[0043] By setting a control switch S1 in the three-phase uncontrolled rectifier bridge, connecting the common anode of the three-phase uncontrolled rectifier bridge to one end of the control switch S1, and connecting the common cathode of the three-phase uncontrolled rectifier bridge to the other end of the control switch S1, the control switch S1 can be switched between connection and disconnection to realize the switching of the first three-phase winding between the star-connected neutral point and the open winding, thereby meeting different working requirements.

[0044] Among them, both the conversion switch and the control switch use contactors or power electronic switches. Contactors usually have large current and voltage carrying capacity and are suitable for high-power power transmission and control scenarios. Power electronic switches have extremely fast switching speeds and can complete on-off operations within microseconds, which are suitable for fast response scenarios.

[0045] In this embodiment, please refer to Figure 2-4 , further comprising: a stator core 1, on which a plurality of stator teeth 2 are arranged, and on each stator tooth 2 a coil of a first three-phase winding and a coil of a second three-phase winding are wound simultaneously.

[0046] Specifically, the stator tooth portion 2 is provided with a first stator tooth portion 3, a second stator tooth portion 4, a seventh stator tooth portion 5 and an eighth stator tooth portion 6 corresponding to one of the windings A in the first three-phase windings and one of the windings a in the second three-phase windings; the first stator tooth portion 3 and the second stator tooth portion 4 are arranged adjacent to each other, and the seventh stator tooth portion 5 and the eighth stator tooth portion 6 are arranged adjacent to each other; the first stator tooth portion 3 and the seventh stator tooth portion 5 are arranged opposite to each other, and the second stator tooth portion 4 and the eighth stator tooth portion 6 are arranged opposite to each other;

[0047] A coil A1 of winding A and a coil a1 of winding a are wound on the first stator tooth 3; a coil A2 of winding A and a coil a2 of winding a are wound on the second stator tooth 4; coil A1 and coil A2 are connected in series in reverse, and coil a1 and coil a2 are connected in series in reverse;

[0048] A coil A3 of winding A and a coil a3 of winding a are wound on the seventh stator tooth 5, and the coil A3 and the coil a3 are connected in series in reverse order;

[0049] A coil A4 of winding A and a coil a4 of winding a are wound on the eighth stator tooth 6, and the coil A4 and the coil a4 are connected in series in reverse order;

[0050] The coil A1, coil A2, coil A3 and coil A4 are connected in series, and the coil a1, coil a2, coil a3 and coil a4 are connected in series.

[0051] In this embodiment, through the winding method of the winding, one coil of the first three-phase winding and one coil of the second three-phase winding are wound on each stator tooth at the same time, so that the phase difference of the magnetomotive force of the first three-phase winding and the second three-phase winding in space is 0°, so when controlling, the current torque angle β of the first three-phase winding and the second three-phase winding is set to be equal, and the torque angle β only needs to be calculated once. The control system of the motor is simplified.

[0052] Among them, winding A can be any one of winding B, winding C and winding D, and winding a can be any one of winding b, winding c and winding d. After winding B and winding b are wound in the above manner, winding C and winding c are then rotated 120° in space in sequence to wind winding C, and then winding D and winding d are then rotated 120° in space in sequence to wind winding D.

[0053] In a specific application scenario, Z stator teeth are evenly distributed on the stator yoke along the circumferential direction on the stator core 1, and Z stator slots for winding are formed between the stator teeth. Magnetic steel slots with a pole pair number of p are evenly arranged along the circumference of the rotor core, and permanent magnets are installed in the magnetic steel slots. The relationship between the number of stator slots Z and the number of pole pairs p of the unit motor satisfies the following equation:

[0054] Z=2p±2N, N=1, 2, 3...

[0055] The number of motor pole pairs p=5, and the coefficient of the number of stator slots N=1, then the number of slots Z=12. The following description will be based on the motor with 12 slots and 10 poles. The formula for calculating the slot pitch electrical angle of the motor is:

[0056] α = 360°p / Z;

[0057] In this 12-slot 10-pole motor, the slot pitch electrical angle α of the motor is 150°, from which the slot potential star diagram of the unit motor is drawn as follows Figure 5 As shown, the slot potential star diagram only reflects the potential phase of each slot conductor of the first three-phase winding, and the potential phase of each slot conductor of the second three-phase winding is similar to that of the first three-phase winding.

[0058] The above winding split combination principle is suitable for permanent magnet synchronous motors with other rotor structures. The stator winding only needs to have more than 2 slots per pole per phase. In addition, the winding distribution ratio can be adjusted according to the speed regulation range.

[0059] In this embodiment, the number of turns of the first three-phase winding and the second three-phase winding are different. For example, the first inverter is used as the main inverter and the second inverter is used as the auxiliary inverter. At this time, the number of turns N1 of the first three-phase winding needs to be greater than the number of turns N2 of the second three-phase winding. In this way, it can be ensured that the number of turns of the first three-phase winding and the second three-phase winding meet the requirements of using more winding series turns at low speed and using fewer winding series turns at high speed, thereby achieving a three-stage speed regulation range.

[0060] In this embodiment, the wire diameters of the first three-phase winding and the second three-phase winding are the same.

[0061] When the wire diameters of the two three-phase windings are the same, designers can design and select materials based on unified specifications, without having to customize different wire diameters for different windings, thus simplifying the design process. During the manufacturing process, since the wire diameters are consistent, wires can be purchased and processed in batches, improving production efficiency and reducing production costs. Unified wire diameters also facilitate inventory management, reduce the types of spare parts, and reduce management costs.

[0062] It should be noted that the winding of each phase in the first three-phase winding and the second three-phase winding can be connected in series or in parallel, that is, the first three-phase winding and the second three-phase winding can be connected in series in star connection or in parallel in star connection.

[0063] In this embodiment, the capacities of the main inverter and the sub-inverter are equal, and the maximum supply voltage of the first inverter is equal to the maximum supply voltage of the second inverter.

[0064] Since the maximum supply voltage and capacity of the two inverters are the same, inverters of the same specifications and models can be selected, thereby reducing procurement costs. In addition, the unified voltage standard also helps to reduce the need for customized special parts or equipment due to voltage differences, further reducing system costs.

[0065] Furthermore, the back electromotive force of the permanent magnet synchronous motor is smaller than the maximum supply voltage of the first inverter, and the permanent magnet synchronous motor adopts maximum torque current ratio (MTPA) control.

[0066] Since the back electromotive force of the permanent magnet synchronous motor will not exceed the maximum supply voltage of the inverter, the permanent magnet synchronous motor adopts MTPA control throughout the process without the need to introduce complex weak magnetic field control, thus avoiding the irreversible demagnetization of the permanent magnet during weak magnetic field control and prolonging the service life of the motor. The use of maximum torque current ratio control can also reduce the current demand of the motor, thereby allowing the use of a smaller capacity inverter to supply power and reducing system costs.

[0067] The concentrated winding permanent magnet synchronous motor of this embodiment is divided into two main windings and auxiliary windings with different turns and equal wire diameters by the winding on one stator tooth, and connected to form independent three-phase main windings and three-phase auxiliary windings. This design enables the motor to have different operating modes at different speeds.

[0068] At low speeds, the primary and secondary windings run in series, which means that current flows through both the primary and secondary windings at the same time, giving the motor a higher torque output capability at low speeds.

[0069] When running at medium speed, the main winding and the auxiliary winding operate as independent dual three-phase windings, so that the motor can maintain a high torque output capacity when the speed continues to increase.

[0070] When running at high speed, only the auxiliary winding is kept running. This means that only the auxiliary winding generates a magnetic field, and the main winding does not participate in the work. Since the number of turns of the auxiliary winding is small, the back electromotive force of the motor is small at high speed, which can increase the maximum speed.

[0071] The concentrated winding permanent magnet synchronous motor using this method does not need to change the original motor stator and rotor punching, saving mold opening costs. When winding the machine, the existing tooling can be used for operation, which improves production efficiency. In addition, since the design of the main winding and auxiliary winding can be adjusted as needed, the performance of the motor can be optimized according to the specific application scenario.

[0072] See also Figure 6 This embodiment also provides a control method for a permanent magnet synchronous motor, including:

[0073] S101: When the speed of the permanent magnet synchronous motor is less than or equal to a first speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be disconnected, the winding switch conversion component is turned on, the first inverter is turned on, and the second inverter is turned off;

[0074] S102: When the speed of the permanent magnet synchronous motor is greater than the first speed threshold and less than or equal to the second speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be turned on, the winding switch conversion component is disconnected, the first inverter is turned on, and the second inverter is turned on;

[0075] S103: When the speed of the permanent magnet synchronous motor is greater than the second speed threshold and less than or equal to the third speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be turned on, the winding switch conversion component is disconnected, the first inverter is turned off, and the second inverter is turned on.

[0076] The first speed threshold is smaller than the second speed threshold, and the second speed threshold is smaller than the third speed threshold.

[0077] Specifically, when the speed of the permanent magnet synchronous motor increases from 0 to the first speed threshold n1, the control conversion switch S2, the conversion switch S3 and the conversion switch S4 are turned on, the control switch S1 is turned off, the first three-phase winding and the second three-phase winding are operated in series, and only the first inverter supplies power to the permanent magnet synchronous motor, and the second inverter is turned off. When the speed of the permanent magnet synchronous motor decreases from the first speed threshold n1 to 0, the state of the switch does not change. When the speed of the permanent magnet synchronous motor is the first speed threshold n1, the back electromotive force Un1 of the motor is the back electromotive force U of the first three-phase winding. ABC And the back EMF U of the second three-phase winding abc The sum of Un1 and U ABC +U abc , and the maximum supply voltage U of the inverter satisfies the relationship: Un1≤0.95U.

[0078] When the speed of the permanent magnet synchronous motor rises from the first speed threshold n1 to the second speed threshold n2, the control conversion switch S2, the conversion switch S3 and the conversion switch S4 are first disconnected, and then the control switch S1 is turned on. The first three-phase winding and the second three-phase winding work separately as dual three-phase windings with independent neutral points. At this time, the first inverter supplies power to the first three-phase winding separately, and the second inverter supplies power to the second three-phase winding separately. However, when the speed of the permanent magnet synchronous motor drops from the second speed threshold n2 to the first speed threshold n1, it is necessary to first disconnect the control switch S1, and then turn on the conversion switch S2, the conversion switch S3 and the conversion switch S4. When running at medium speed, the first inverter and the first three-phase winding are always in working state, and the second inverter and the second three-phase winding can be selected to be in working state or closed state according to the load conditions. At this time, since the number of turns N1 of the first three-phase winding is greater than the number of turns N2 of the second three-phase winding, U ABC >U abc , so the back electromotive force of the permanent magnet synchronous motor depends on the back electromotive force U of the first three-phase winding ABC , and when the speed of the permanent magnet synchronous motor is the second speed threshold n2, it satisfies the relationship: U ABC =Un2≤0.95U.

[0079] When the speed of the permanent magnet synchronous motor increases from the second speed threshold n2 to the third speed threshold n3, the control switch S1 is kept open, the conversion switch S2, the conversion switch S3 and the conversion switch S4 are disconnected, and the first inverter is turned off at the same time. Only the second inverter supplies power to the second three-phase winding alone, and only the second inverter of the permanent magnet synchronous motor is in working state. When the speed of the permanent magnet synchronous motor decreases from the third speed threshold n3 to the second speed threshold n2, the state of the switch does not change. When the speed of the permanent magnet synchronous motor is the third speed threshold n3, the back electromotive force Un3 of the permanent magnet synchronous motor is equal to the back electromotive force U of the second three-phase winding. abc , which satisfies the relationship: Uabc =Un3≤0.95U.

[0080] In order to protect the controller and the motor, it is necessary to control the back EMF at each speed node to leave a margin, that is, Un1≤0.95*U, Un2≤0.95U and Un3≤0.95U. And because the maximum back EMF that can be achieved at the three speed nodes is the same, the ratio of the maximum speed of the motor in different speed ranges is:

[0081] .

[0082] It can be seen that the maximum speed of the three speed ranges of the motor can be changed by adjusting the number of series turns of each phase of the winding, which can be achieved by changing the number of turns of the coil of each phase winding on each stator tooth or changing the number of parallel branches of the motor winding. When the number of parallel branches of the motor is fixed, the maximum speed ratio can be changed by adjusting the ratio of the number of turns of the first three-phase winding and the second three-phase winding on the stator tooth. This method effectively expands the speed regulation range of the motor, and the ratio of the maximum speed of the motor to the rated speed can be adjusted according to the ratio of the number of turns of the first three-phase winding and the second three-phase winding.

[0083] In this embodiment, when the motor runs at low speed and high speed, it is a single three-phase motor system powered by a single inverter. When the motor runs at medium speed, it is a dual three-phase motor system powered by dual inverters. At this time, the power of the motor is the sum of the power of the first three-phase winding and the power of the second three-phase winding. Whether to use the second three-phase winding can be determined according to the needs of the load; according to the superposition principle, the required motor torque can be obtained by proportionally allocating the current values ​​of the two sets of windings, and the use of the two sets of windings can be smoothly switched to maintain a stable torque.

[0084] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0085] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive.

[0086] Inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "including a..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A permanent magnet synchronous motor, characterized in that: include: A first inverter, a second inverter, a first three-phase winding, a second three-phase winding, a winding switch conversion component and a three-phase uncontrolled rectifier bridge, wherein one end of the first three-phase winding is connected to the first inverter, the other end of the first three-phase winding is respectively connected to one end of the winding switch conversion component and the three-phase uncontrolled rectifier bridge, the second three-phase winding is respectively connected to the second inverter and the other end of the winding switch conversion component, and the winding switch conversion component is used to realize the first three-phase winding and the second three-phase winding working in series, or the first three-phase winding and the second three-phase winding working separately; The winding switch conversion component includes three conversion switches, the common end of each winding in the first three-phase winding and the lead end of each winding in the second three-phase winding are connected through a conversion switch respectively, the lead ends of the three windings in the first three-phase winding are all connected to the first inverter, the common ends of the three windings in the first three-phase winding are all connected to the three-phase uncontrolled rectifier bridge, the lead ends of the three windings in the second three-phase winding are all connected to the second inverter, and the common ends of the three windings in the second three-phase winding are connected together and serve as a neutral point; It also includes: a stator core, wherein a plurality of stator teeth are arranged on the stator core, and each of the stator teeth is wound with a coil of the first three-phase winding and a coil of the second three-phase winding at the same time; The stator tooth portion is provided with a first stator tooth portion, an eighth stator tooth portion, a second stator tooth portion and a seventh stator tooth portion corresponding to one of the windings A in the first three-phase windings and one of the windings a in the second three-phase windings; the first stator tooth portion and the second stator tooth portion are arranged adjacent to each other, and the seventh stator tooth portion and the eighth stator tooth portion are arranged adjacent to each other; the first stator tooth portion and the seventh stator tooth portion are arranged opposite to each other, and the second stator tooth portion and the eighth stator tooth portion are arranged opposite to each other.

2. The permanent magnet synchronous motor according to claim 1, characterized in that: Also includes: A control switch, the common anode of the three-phase uncontrolled rectifier bridge is connected to one end of the control switch, the common cathode of the three-phase uncontrolled rectifier bridge is connected to the other end of the control switch, and the three-phase input ends of the three-phase uncontrolled rectifier bridge are respectively connected to the common ends of the three windings in the first three-phase winding.

3. The permanent magnet synchronous motor according to claim 2, characterized in that: The conversion switch and the control switch both adopt contactors or power electronic switches.

4. The permanent magnet synchronous motor according to claim 1, characterized in that: A coil A1 of the winding A and a coil a1 of the winding a are wound on the first stator tooth; a coil A2 of the winding A and a coil a2 of the winding a are wound on the second stator tooth; the coil A1 and the coil A2 are connected in reverse series, and the coil a1 and the coil a2 are connected in reverse series; A coil A3 of the winding A and a coil a3 of the winding a are wound on the seventh stator tooth, and the coil A3 and the coil a3 are connected in series in reverse order; A coil A4 of the winding A and a coil a4 of the winding a are wound on the eighth stator tooth portion, and the coil A4 and the coil a4 are connected in series in reverse order; The coil A1, coil A2, coil A3 and coil A4 are connected in series, and the coil a1, coil a2, coil a3 and coil a4 are connected in series.

5. The permanent magnet synchronous motor according to claim 1, characterized in that: The first three-phase winding and the second three-phase winding have different numbers of turns.

6. The permanent magnet synchronous motor according to claim 1, characterized in that: The first three-phase winding and the second three-phase winding have the same wire diameter.

7. The permanent magnet synchronous motor according to claim 1, characterized in that: The maximum supply voltage of the first inverter is equal to the maximum supply voltage of the second inverter.

8. The permanent magnet synchronous motor according to claim 7, characterized in that: The back electromotive force of the permanent magnet synchronous motor is smaller than the maximum supply voltage of the first inverter, and the permanent magnet synchronous motor adopts maximum torque current ratio control.

9. A control method for a permanent magnet synchronous motor according to any one of claims 1 to 8, characterized in that: include: When the speed of the permanent magnet synchronous motor is less than or equal to a first speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be disconnected, the winding switch conversion component is turned on, the first inverter is turned on, and the second inverter is turned off; When the speed of the permanent magnet synchronous motor is greater than a first speed threshold and less than or equal to a second speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be turned on, the winding switch conversion component is disconnected, the first inverter is turned on, and the second inverter is turned on; When the speed of the permanent magnet synchronous motor is greater than the second speed threshold and less than or equal to the third speed threshold, the three-phase uncontrolled rectifier bridge is controlled to be turned on, the winding switch conversion component is disconnected, the first inverter is turned off, and the second inverter is turned on, wherein the first speed threshold is less than the second speed threshold, and the second speed threshold is less than the third speed threshold.

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