A multi-stage adjustable speed power shunt motor system and its control method

Abstract

This invention discloses a multi-stage adjustable speed power shunt motor system and its control method, relating to the field of motor technology. The system includes at least two stages of motor units arranged sequentially along the axial or radial direction; the rotor of the first-stage motor unit serves as the total power output end; the rotor of the second-stage motor unit is driven by the stator of the previous-stage motor unit, driving the stator to rotate; except for the last stage, all other stators are rotatable structures. By controlling the rotation direction and speed of the rotors of the second-stage and subsequent motor units, the relative speed between the stator and rotor of the previous-stage motor unit is adjusted, achieving electromagnetic coupling and power shunt, thus changing the system's total output torque, speed, and back electromotive force. This invention has a compact structure, achieves optimized efficiency under all operating conditions, balances low-speed high torque and high-speed constant power operation, and optimizes both drive and power generation performance, making it suitable for electric vehicles, wind power generation, industrial transmission, and other fields.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and more specifically, to a multi-stage motor system capable of achieving wide-range and efficient speed regulation, particularly suitable for scenarios requiring wide-speed-range and efficient operation, such as electric vehicles, wind power generation, and industrial transmissions. Background Technology

[0002] Traditional motors typically operate with a fixed stator and a rotating rotor, resulting in a relatively fixed speed range and efficiency range. To broaden the speed range, some multi-rotor or dual-stator designs have emerged in existing technologies.

[0003] Prior art 1 (CN91102215.5) discloses an externally driven low-speed rotating stator type three-phase AC speed-regulating asynchronous motor, which uses an external small-power motor and a reduction gear to make the stator of the main motor rotate at low speed, and uses speed superposition to achieve speed regulation. However, this solution has the following shortcomings: (1) It requires an external auxiliary motor and a reduction gear, which is complex in structure and occupies a large space; (2) It can only achieve unidirectional speed superposition (speed increase), which cannot meet the requirements of low-speed and high-torque working conditions; (3) The stator rotation speed cannot be actively adjusted according to the working conditions, and the efficiency optimization capability is limited.

[0004] Existing technology 2 (CN114285240A) discloses a dual-stator multi-winding permanent magnet synchronous motor, which achieves low-speed high torque and high-speed high power operation by setting multiple sets of windings with different pole pairs and cooperating with a controller for commutation. However, this scheme has the following shortcomings: (1) It belongs to the electric speed regulation scheme, which requires multiple sets of windings, resulting in high copper loss and difficult heat dissipation; (2) The winding switching is stepped regulation, which causes torque fluctuations; (3) Efficiency optimization under power generation conditions is not considered.

[0005] Prior art 3 (US5677605) discloses a magnetic field weakening technology for a brushless permanent magnet motor, which weakens the magnetic field at high speeds by applying an additional current. However, this solution is an electrical field weakening method, which generates additional losses and heat, and is complex to control.

[0006] In addition, there are some mechanical power shunt devices in the existing technology (such as US8639423B2), which change the power shunt ratio by adjusting the axial spacing through a planetary roller mechanism. They belong to the category of pure mechanical transmission, have a complex structure, and cannot achieve bidirectional flow and fine adjustment of electromagnetic energy.

[0007] To address the aforementioned problems, this invention proposes a novel multi-stage power shunt motor system based on electromagnetic coupling. Summary of the Invention

[0008] This invention aims to solve the technical problems of low efficiency, limited speed range, and complex structure of existing motors over a wide speed range. It provides a multi-stage adjustable speed power shunt motor system that is compact, can achieve full-condition efficiency optimization through electromagnetic power shunt, balances low-speed high torque and high-speed constant power operation, and simultaneously optimizes drive and power generation performance.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A multi-stage adjustable speed power shunt motor system includes: At least two motor units arranged sequentially along the axial or radial direction; The first-stage motor unit, whose rotor serves as the total power output end of the system; At least one second-stage motor unit, the rotor of which is drivenly connected to the stator of an adjacent first-stage motor unit, for directly driving the stator of the first-stage motor unit to rotate; Except for the last stage motor unit, the stators of all other motor units are rotatable; the stator of the last stage motor unit is fixed or releasably fixed to the housing.

[0010] By controlling the rotation direction and speed of the rotors of the second-stage motor unit and subsequent motor units, the relative speed between the stator and rotor of the driven previous-stage motor unit is adjusted, thereby changing the total output torque, speed and back electromotive force of the system, and realizing the electromagnetic coupling and shunting of power between each stage of motor units.

[0011] Furthermore, the motor unit is a radial flux motor or an axial flux motor.

[0012] Furthermore, the transmission connection includes one or more combinations of coaxial fixed connection, coupling connection, gear transmission, belt transmission, chain transmission or transmission shaft connection.

[0013] Furthermore, the system also includes a controller, which includes a power flow management module that is electrically connected to the current detection unit and voltage detection unit of each stage of the motor unit; the controller adjusts the rotation direction and speed of the rotor of the second stage and subsequent stages of the motor unit according to the signals from the current detection unit and voltage detection unit.

[0014] This invention also protects a control method applied to the above-mentioned system, comprising: Drive mode: When the system operates in low-speed, high-torque mode, the rotation direction and speed of the rotor of at least one non-final-stage motor unit are controlled so that the stator of the preceding motor unit it drives rotates in the opposite direction to the rotor of the preceding motor unit. At this time, the first motor unit can still maintain a high electromagnetic torque at a lower output speed, achieving an equivalent "deceleration and torque increase", while the power required for speed regulation is input in electromagnetic form through the second motor unit.

[0015] When the system operates in high-speed mode, the rotation direction and speed of the rotor of at least one non-final-stage motor unit are controlled so that the stator of the preceding motor unit driven by the non-final-stage motor unit rotates in the same direction as the rotor of the preceding motor unit, thereby reducing the relative speed between them. At this time, the back electromotive force of the first-stage motor unit naturally decreases, eliminating the need for applying a field-weakening current and achieving an equivalent "mechanical field-weakening speed increase." Although the second-stage motor unit consumes some power to maintain the first-stage stator's rotation in the same direction, the field-weakening losses saved by the first-stage motor unit are usually far greater than this consumption, thus improving the overall system efficiency.

[0016] Power generation mode: When the system operates in low-speed power generation mode, the rotor rotation direction and speed of at least one non-final-stage motor unit are controlled so that the stator of the preceding motor unit it drives rotates in the opposite direction to the rotor of that preceding motor unit, thereby increasing the relative speed. At this time, even if the mechanical speed input to the prime mover is low, the first motor unit can still generate a sufficiently high back electromotive force for rectification or grid connection. The energy of this voltage gain comes partly from the mechanical energy of the prime mover and partly from the electrical energy input of the second motor unit—the latter can be considered a "active excitation" trade-off for achieving low-speed power generation capability.

[0017] When the system is operating in high-speed power generation mode, the rotation direction and speed of the rotor of at least one non-final stage motor unit are controlled so that the stator of the previous stage motor unit it drives rotates in the same direction as the rotor of the previous stage motor unit, thereby reducing the relative speed and preventing the generator back electromotive force from being too high and damaging the downstream power electronic devices, while avoiding the additional losses caused by deep field weakening.

[0018] This invention is applicable to various types of AC motors, although the performance of different motor types varies under the technical solution of this invention. Permanent magnet synchronous motors are the best application target of this invention because their back electromotive force is strictly proportional to the speed; the mechanical speed regulation of this invention can be directly converted into linear adjustment of the back electromotive force. Asynchronous motors show significant optimization effects in this invention. By driving the stator to rotate in the opposite direction through the upper-stage motor, a smaller slip rate can be maintained, transferring rotor copper losses to the stator. Simultaneously, the rotating stator can drive airflow inside the motor, improving low-speed heat dissipation. Axial flux motors have obvious structural advantages, with a short axial dimension, facilitating multi-stage series connection. Switched reluctance motors and electrically excited synchronous motors also show certain optimization effects.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. Integrated electromagnetic power shunt structure: Unlike existing technologies that use external auxiliary motors or purely mechanical transmission devices, this invention integrates the speed-regulating motor into the system. Through direct transmission and electromagnetic coupling of multi-stage motor units, it realizes active and continuous adjustment of the stator speed of the main motor, resulting in a more compact structure and higher power density.

[0020] 2. Full-speed-range bidirectional mechanical magnetic adjustment: Unlike existing technologies that can only achieve unidirectional speed superposition, this invention controls the direction of rotation of the upper motor rotor, which can achieve both opposite rotation of the lower motor stator and rotor, as well as same-direction rotation. For the first time, it achieves full-speed-range bidirectional speed regulation in the same system through pure electromagnetic means.

[0021] 3. Fundamentally optimize field weakening loss distribution: Unlike existing electrical solutions that use additional current to weaken the magnetic field, this invention achieves "mechanical field weakening" by rotating the stator in the same direction, which reduces the back electromotive force of the main motor from a physical perspective and eliminates the direct-axis current and its copper loss in the traditional field weakening process.

[0022] 4. A novel optimization path for power generation: Existing technologies have not considered the issue of power generation efficiency. This invention proposes for the first time a scheme to optimize performance by controlling the direction of the stator in power generation mode, providing a novel technical path for wide-speed-range power generation systems.

[0023] 5. Special optimization effects for asynchronous motors: This invention creatively solves the inherent defects of asynchronous motors under low-speed, high-torque conditions, transfers rotor copper losses to the stator, and improves low-speed heat dissipation conditions, thus breaking through the application bottleneck of asynchronous motors in this field.

[0024] 6. Flexible structure: This invention does not limit the specific type of motor or transmission method, and has strong scalability and adaptability. Attached Figure Description

[0025] Figure 1 : Structural diagram of Embodiment 1 of the present invention (two-stage motors coaxially connected) Figure 2 : Structural diagram of Embodiment 2 of the present invention (three-stage motor series structure) Detailed Implementation

[0026] Example 1: Two-stage coaxial motor structure like Figure 1 As shown, this embodiment provides a two-stage adjustable speed power shunt motor system. The system includes a housing 100, a first motor unit 200, and a second motor unit 300.

[0027] The first motor unit 200 includes a first stator 210 and a first rotor 220. The first stator 210 is rotatably supported within the housing 100, and the first rotor 220 is rotatably supported within the first stator 210. The central axis of the first rotor 220 serves as the system's total power output end and is connected to an external load. The second motor unit 300 includes a second stator 310 and a second rotor 320. The second stator 310 is fixed to the housing 100. The second rotor 320 is rotatably supported within the second stator 310, and the second rotor 320 is fixedly connected to the housing of the first stator 210 via a transmission connector 400. During operation, the controller controls the rotation direction and speed of the second rotor 320 according to the working conditions: when low-speed, high-torque output is required, the rotation direction of the second rotor 320 is controlled so that the first stator 210 and the first rotor 220 rotate in opposite directions, increasing the relative speed between them and achieving an equivalent "deceleration and torque increase"; when high-speed operation is required, the rotation direction of the second rotor 320 is controlled so that the first stator 210 and the first rotor 220 rotate in the same direction, reducing the relative speed between them and achieving an equivalent "mechanical field weakening and speed increase".

[0028] Example 2: Three-stage motor series structure like Figure 2 As shown, this embodiment provides a three-stage adjustable speed power shunt motor system. A third motor unit 500 is added to the first motor unit 200 and the second motor unit 300.

[0029] The third motor unit 500 includes a third stator 510 and a third rotor 520. The third stator 510 is fixed to the housing 100. The third rotor 520 is rotatably supported inside the third stator 510, and the third rotor 520 is drively connected to the housing of the second stator 310.

[0030] By controlling the combination of direction of rotation and speed of the second rotor 320 and the third rotor 520, a more flexible speed regulation range can be achieved. For example, under extremely low-speed conditions, the second rotor 320 can be controlled to rotate in the opposite direction to the first rotor 220, while the third rotor 520 can be controlled to rotate in the opposite direction to the second rotor 320, so that the first stator 210 obtains a higher reverse speed, further improving the equivalent torque of the first motor unit 200. Based on the signals from the current detection unit and voltage detection unit of each motor unit, the controller adjusts the direction of rotation and speed of the second rotor 320 and the third rotor 520 through the power flow management module, so that the electromagnetic power flow of each motor unit matches the external characteristic requirements.

[0031] Example 3: Gear transmission connection method The difference between this embodiment and Embodiment 1 lies in the transmission connection method. The second rotor 320 and the first stator 210 are connected by a gear transmission mechanism.

[0032] Specifically, a driving gear is fixed on the central shaft of the second rotor 320, and a driven gear is fixed on the outer shell of the first stator 210. The driving gear meshes with the driven gear. The rotation of the second rotor 320 drives the first stator 210 to rotate through gear transmission.

[0033] This transmission method is suitable for scenarios where the motor units are arranged with parallel shafts, and the transmission ratio can be flexibly adjusted to optimize the power matching between the two motors.

[0034] Example 4: Belt drive connection method The difference between this embodiment and embodiment 3 is that belt drive is used. A driving pulley is fixed on the central shaft of the second rotor 320, and a driven pulley is fixed on the outer shell of the first stator 210. The driving pulley and the driven pulley are connected by a belt.

[0035] Belt drives have the advantages of buffering and shock absorption, and low cost, making them suitable for scenarios where transmission accuracy requirements are not high but vibration isolation is necessary.

[0036] Example 5: Multi-level Cooperative Control This embodiment details the specific operation of the controller. The controller includes a speed detection module, a torque detection module, a mode determination module, a drive control module, and a power flow management module. The speed detection module is electrically connected to the speed sensors of the first rotor 220 and the second rotor 320, the torque detection module is electrically connected to the torque sensor of the first rotor 220, and the power flow management module is electrically connected to the current detection unit and voltage detection unit of each stage of the motor unit.

[0037] The speed detection module monitors the output speed n_out of the first rotor 220 and the speed n_drive of the second rotor 320 in real time. The torque detection module monitors the output torque T_out in real time. The mode judgment module determines whether the current operating condition belongs to the low-speed, high-torque region, the high-speed operating region, or the transition region based on n_out and T_out. The power flow management module calculates the instantaneous power of each stage of the motor based on the signals from the current detection unit and the voltage detection unit.

[0038] When the system is identified as operating in a low-speed, high-torque range, the drive control module calculates the required relative speeds of the first stator 210 and the first rotor 220 based on the target torque. It then calculates the target speed and direction of rotation (opposite to the first rotor 220) of the second rotor 320 and drives the second motor unit 300 to operate according to these parameters. At this time, the second motor unit 300 operates in motor mode, and its input power is used to establish the relative speed.

[0039] When the system is determined to be in the high-speed operating zone, the drive control module calculates the required relative speeds of the first stator 210 and the first rotor 220 based on the target speed. It then calculates the target speed and direction of the second rotor 320 (in the same direction as the first rotor 220) and drives the second motor unit 300 to operate according to these parameters. At this time, the second motor unit 300 also operates in motor mode, but its power consumption is less than the losses saved by the first motor unit if it used electrical field weakening.

[0040] When the transition zone is identified, the drive control module adopts a smooth transition algorithm to make the speed and direction of the second rotor 320 change continuously, avoiding sudden torque changes.

[0041] In power generation mode, the controller also selects the direction of rotation of the second rotor 320 (reverse direction to increase voltage, same direction to decrease voltage) based on the input speed and target power generation voltage. During low-speed power generation, the second motor unit 300 operates in motor mode, consuming a small amount of electrical energy for "active excitation" to establish voltage; during high-speed power generation, the second motor unit 300 can operate in power generation mode or no-load mode, depending on the control strategy.

[0042] Industrial applicability This invention can be widely applied in electric vehicle drive systems, wind turbine generator sets, industrial transmission equipment, and other fields. In electric vehicles, it can replace the traditional gearbox + motor combination, achieving continuously variable transmission and optimized efficiency under all operating conditions. In wind power generation, it can maintain the generator's high-efficiency speed range when wind speed changes, and establish grid-connected voltage through active excitation at low wind speeds. In industrial transmissions, it can meet the dual requirements of a wide speed range and high efficiency.

Claims

1. A multi-stage adjustable speed power shunt motor system, characterized in that, include: At least two-stage motor units, wherein the motor units are arranged sequentially along the axial or radial direction; The first-stage motor unit, whose rotor serves as the total power output end of the system; At least one second-stage motor unit, the rotor of which is drivenly connected to the stator of an adjacent first-stage motor unit, for driving the stator of the first-stage motor unit to rotate; Except for the last stage motor unit, the stators of all other motor units are rotatable; the stator of the last stage motor unit is fixed.

2. The multi-stage adjustable speed power shunt motor system according to claim 1, characterized in that, The transmission connection includes one or more combinations of coaxial fixed connection, coupling connection, gear transmission, belt transmission, chain transmission or transmission shaft connection.

3. The multi-stage adjustable speed power shunt motor system according to claim 1, characterized in that, The motor unit is a radial flux motor or an axial flux motor.

4. The multi-stage adjustable speed power shunt motor system according to claim 1, characterized in that, The motor unit is an AC rotating motor, including a permanent magnet synchronous motor, an asynchronous motor, a switched reluctance motor, or an electrically excited synchronous motor.

5. The multi-stage adjustable speed power shunt motor system according to claim 1, characterized in that, It also includes a controller, which includes a power flow management module that is electrically connected to the current detection unit and voltage detection unit of each stage of the motor unit; the controller adjusts the rotation direction and speed of the rotor of the second stage and subsequent stages of the motor unit according to the signals from the current detection unit and voltage detection unit.

6. The multi-stage adjustable speed power shunt motor system according to claim 1, characterized in that, When the system is operating in drive mode: under low speed and high torque conditions, the rotation direction and speed of the rotor of at least one non-final stage motor unit are controlled so that the stator of the previous stage motor unit driven by the non-final stage motor unit rotates in the opposite direction to the rotor of the previous stage motor unit. In high-speed operation, the rotation direction and speed of the rotor of at least one non-final stage motor unit are controlled so that the stator of the previous stage motor unit driven by the non-final stage motor unit rotates in the same direction as the rotor of the previous stage motor unit.

7. The multi-stage adjustable speed power shunt motor system according to claim 1, characterized in that, When the system is operating in power generation mode: In low-speed power generation conditions, the rotation direction and speed of the rotor of at least one non-final stage motor unit are controlled so that the stator of the previous stage motor unit driven by the non-final stage motor unit rotates in the opposite direction to the rotor of the previous stage motor unit. In high-speed power generation, the rotor rotation direction and speed of at least one non-final stage motor unit are controlled so that the stator of the previous stage motor unit driven by the non-final stage motor unit rotates in the same direction as the rotor of the previous stage motor unit.

8. The multi-stage adjustable speed power shunt motor system according to claim 1, characterized in that, The system includes three or more motor units.

9. A control method applied to the system according to any one of claims 1 to 8, characterized in that, Includes the following steps: Obtain current operating condition information, including output speed and output torque; In drive mode, when the output torque is greater than the first threshold and the output speed is less than the second threshold, the rotor of at least one non-final stage motor unit is controlled to rotate in the opposite direction to the rotor of the previous stage motor unit it drives; when the output speed is greater than the third threshold, the rotor of at least one non-final stage motor unit is controlled to rotate in the same direction as the rotor of the previous stage motor unit it drives. In power generation mode, when the input speed is less than the fourth threshold and power generation voltage needs to be established, the rotor of at least one non-final stage motor unit is controlled to rotate in the opposite direction to the rotor of the previous stage motor unit it drives; when the input speed is greater than the fifth threshold, the rotor of at least one non-final stage motor unit is controlled to rotate in the same direction as the rotor of the previous stage motor unit it drives.

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