A current equalization control method for a multi-disc axial flux permanent magnet motor

Abstract

The application discloses a kind of multi-disc axial flux permanent magnet motor current equalization control methods, method includes detecting the actual rotating speed of n axial superposition stator disc (hereinafter referred to as n disc, n is greater than or equal to 2) of multi-disc axial flux permanent magnet motor, and difference with given rotating speed is input into rotating speed controller to obtain n output currents;Output current and the actual current of n disc after coordinate transformation are input into current equalization controller to obtain n q-axis equalization given currents;Difference of dq-axis equalization given current and actual dq-axis current is input into current controller to obtain n dq-axis given voltages, and multi-disc axial flux permanent magnet motor is driven based on dq-axis given voltage and operates.The method of the application makes the stator current of n disc of multi-disc axial flux permanent magnet motor reach dynamic balance in the process of operation, inhibits the uneven heating phenomenon of multi-disc axial flux permanent magnet motor stator disc, reduces torque ripple, prolongs the service life of motor, enhances system reliability and stability.

Description

Technical Field

[0001] This invention belongs to the field of motor control, specifically relating to a current balancing control method for a multi-disc axial flux permanent magnet motor. Background Technology

[0002] Disc motors, with their axially distributed magnetic flux and planar air gap, offer advantages such as compact structure, small size, high efficiency, and high power density, making them increasingly popular in the market. Based on the number and relative positions of the stator and rotor, disc motor topologies can be categorized into four main types: single-stator single-rotor single-air-gap structure, single-stator dual-rotor structure, dual-stator single-rotor structure, and multi-disc structure. The multi-disc structure involves axially stacking disc motors, adding stator and rotor modules to form a multi-air-gap structure. This increases the motor's electrical load and power density, meeting the needs of high-torque direct drive, reducing the size of the drive system, and improving efficiency. Disc-type axial flux permanent magnet synchronous motors combine the characteristics of disc motors and permanent magnet motors, offering even higher efficiency and greater power density, and have broad application prospects in aerospace, drones, new energy, and heavy machinery equipment.

[0003] Currently, many scholars both domestically and internationally are researching disc-type permanent magnet motors. For example, patent number 201811013321X, titled "A Low-Voltage High-Power Axial Combined Disc-Type Permanent Magnet Motor," decomposes a high-voltage, high-power motor into multiple low-voltage, normal-power axially combined disc-type permanent magnet motor units to directly drive the load, providing greater torque, reducing the manufacturing, transportation, installation, and maintenance costs of the motor, and improving system reliability. However, due to the special structure of multi-disc axial flux permanent magnet motors, the parameters of each stator disc, such as stator resistance, inductance, and the power supply voltage applied to the windings, inevitably differ. When the multi-disc axial flux permanent magnet motor is running, the stator current of each disc will inevitably differ, resulting in different torque loads during motor operation, increased torque pulsation, unstable motor operation, and uneven heating of each disc. If not controlled in time, this will damage the insulation of the multi-disc permanent magnet motor for long-term operation, shorten the overall system life, and reduce system reliability. Therefore, in order to suppress the adverse effects of current imbalance and achieve high-performance drive control, it is necessary to adopt effective control strategies to suppress the current imbalance phenomenon of multi-disc permanent magnet motors. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a current balancing control method for a multi-disc axial flux permanent magnet motor, which enables the stator current of each disc of the multi-disc axial flux permanent magnet motor to achieve dynamic balance during operation, realize coordinated torque control, avoid the impact of torque pulsation on the system's operational stability and bearings, improve the system's dynamic response performance, suppress the uneven heating phenomenon of the stator discs of the multi-disc axial flux permanent magnet motor, extend the motor's service life, and enhance the system's reliability and stability.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: A current balancing control method for a multi-disc axial flux permanent magnet motor, wherein the multi-disc axial flux permanent magnet motor can be an axial superposition of multiple single-disc motors, or a form in which the stator and rotor are arranged coaxially at intervals, comprising n axially superimposed stator disks (hereinafter referred to as n disks), where n is greater than or equal to 2, and permanent magnets are fixedly mounted on the rotor, with the stator and rotor being coaxial. The method is characterized by the following steps: Step 1: The multi-disc axial flux permanent magnet motor adopts a dual closed-loop control system with n speed and current loops, including n current loops and n speed loops, with the current loop being the inner loop and the speed loop being the outer loop; the actual speed ω of the multi-disc axial flux permanent magnet motor is detected by the detection unit. mk (k=1,2……n), given the rotational speed ω ref With actual rotational speed ω mk The difference (k=1,2……n) is input to the speed controller, and the output current i is obtained after adjustment by the speed controller. qk (k=1,2……n); Step 2: Detect the actual current i of the n disks. pk (p=a,b,c……m, where m is the number of phases of a multi-disc axial flux permanent magnet motor; k=1,2……n), i pk The actual d-axis and q-axis currents i of the n disks are obtained after Clark and Park transformations. dak and i qak (k=1,2……n); Step 3: Set the output current i of the speed controller qk (k=1,2……n) and the actual q-axis current i of n disks qak (k=1,2……n) Input current equalization controller, after which the q-axis equalization current is obtained through the action of the current equalization controller. (k=1,2……n); Step 4: Equalize the current applied to the d-axis and q-axis of the n disks. (k=1,2……n) and the actual current i of n disks dak and i qakThe differences (k=1,2……n) are input into the d-axis and q-axis current controllers of the n disks respectively, to obtain the given output voltages of the d-axis and q-axis of the n disks. (k=1,2……n) The α-axis and β-axis output voltages of the n disks are obtained after the inverse Park transformation. (k=1,2……n); Step 5: Output the given voltage based on the α-axis and β-axis of the n disks. (k=1,2……n) The motor control signal is generated by SVPWM or other modulation methods to drive the multi-disc axial flux permanent magnet motor.

[0006] Furthermore, the functions of the current balancing controller include: (1) Find the actual current i of the q-axis of the n disks. qak The average of the maximum and minimum values ​​of (k=1,2……n) gives the current i. a = (max(i qak ) + min(i qak )) / 2; (2) Find the output current i of the n speed controllers. qk The average current i is obtained by averaging the values ​​of (k=1,2……n). qa = ; (3) Take the current i a and i qa The equilibrium value is obtained by deriving the q-axis equilibrium current for the n disks. .

[0007] Specifically, when the n actual rotational speeds ω of the multi-disc axial flux permanent magnet motor are detected... mk When (k=1,2……n) are the same, that is: ω m1 =ω m2 =……=ω mn At this time, the output current i obtained through the speed controller q1 = i q2 =……= i qn At this time, the average current i qa = It can be directly connected to the current i a Equalization is performed to obtain the q-axis equalization current. .

[0008] Furthermore, the detection unit for detecting the actual rotational speed of a multi-disc axial flux permanent magnet motor can be used with an encoder, speed sensor, or displacement sensor. Furthermore, the actual current i of the n disks in the multi-disc axial flux permanent magnet motor pk It can be detected by a current sensor; Furthermore, the speed controller or current controller can employ traditional PI control, various improved PI control methods, or suitable intelligent control methods.

[0009] Furthermore, the multi-disc axial flux permanent magnet motor control system can employ a vector control strategy, particularly an i-axis control system. d =0 vector control strategy.

[0010] Furthermore, the multi-disc axial flux permanent magnet motor control system can use a structure of one controller + n drive circuit modules to control the motor operation, or it can use an independent structure of n (controller + drive circuit modules) to control the motor operation. Furthermore, the controller of the multi-disc axial flux permanent magnet motor control system completes the system's signal acquisition, analysis, calculation, and sends control signals to the drive circuit module; the drive circuit module of the multi-disc axial flux permanent magnet motor control system is connected to the stator of the m-phase multi-disc axial flux permanent magnet motor to complete the drive control of the multi-disc axial flux permanent magnet motor.

[0011] Furthermore, the controller of the multi-disc axial flux permanent magnet motor control system can be a combination of MCU, DSP, FPGA, and various chips. Furthermore, the drive circuit module of the multi-disc axial flux permanent magnet motor control system can use thyristors or field-effect transistors.

[0012] The beneficial effects of the present invention are as follows: The current balancing control method for the multi-disc axial flux permanent magnet motor described in the present invention enables the stator current of the n discs of the multi-disc axial flux permanent magnet motor to achieve dynamic balancing during operation, avoids uneven heating of the stator discs of the multi-disc axial flux permanent magnet motor, reduces torque pulsation, extends the service life of the motor and bearings, effectively suppresses the adverse effects of current imbalance on the reliability and stability of system operation, and realizes high-performance drive control of the multi-disc axial flux permanent magnet motor. Attached Figure Description

[0013] Figure 1 A schematic diagram of an embodiment of a multi-disc axial flux permanent magnet motor.

[0014] Figure 2 A schematic diagram of another embodiment of a multi-disc axial flux permanent magnet motor.

[0015] Figure 3 A schematic diagram of the principle of the multi-disc axial flux permanent magnet motor control system according to an embodiment of the present invention.

[0016] Figure 4 An example of a current balancing controller according to an embodiment of the present invention.

[0017] 1. Stator disc; 2. Rotor disc; 3. Permanent magnet; 4. Bearing; 5. Shaft; 6. Housing; A. Disc motor 1; B. Disc motor 2; N. Disc motor n. Detailed Implementation

[0018] Depending on the topology of the disc motor, the structure of the multi-disc axial flux permanent magnet motor also varies. Currently, the dual external rotor structure is the most commonly used in the market. This invention takes the multi-disc permanent magnet motor with dual external rotor structure as an example, and further explains the invention with reference to the accompanying drawings.

[0019] This invention provides a current balancing control method for a multi-disc axial flux permanent magnet motor. The multi-disc axial flux permanent magnet motor can be an axial superposition of n (n greater than or equal to 2) single-disc motors. A schematic diagram of one embodiment is shown below. Figure 1 As shown, each disc motor includes one stator disc 1 and two rotor discs 2, and adjacent disc motor rotor discs 2 are independent. The permanent magnet 3 is fixedly installed on the side of the rotor disc 2 closest to the stator disc 1. As another embodiment, the multi-disc axial flux permanent magnet motor can also be in the form of coaxially spaced stator and rotor. Figure 2 The schematic diagram shows that each disc motor includes one stator disc 1 and two rotor discs 2. The rotor discs 2 of adjacent disc motors are shared. Permanent magnets 3 are fixedly installed on both sides of the rotor discs. In the embodiment, the permanent magnet 3 on the leftmost rotor disc 2 of the multi-disc axial flux permanent magnet motor with two structures is fixedly installed on the side close to the stator disc 1, and the other side of the rotor disc 2 is connected to the housing 6; the permanent magnet 3 on the rightmost rotor disc 2 is also fixedly installed on the side close to the stator disc 1, and the other side of the rotor disc 2 is connected to the housing 6; the stator disc 1 and the rotor disc 2 are coaxial and are both fixed on the shaft 5 by bearings 4.

[0020] The current balancing control method for a multi-disc axial flux permanent magnet motor includes the following steps: Step 1: The multi-disc axial flux permanent magnet motor adopts an n-loop dual closed-loop control system consisting of n current loops and n speed loops, with the current loops being the inner loops and the speed loops being the outer loops. As an embodiment of the invention, the control system can employ a vector control strategy, particularly a vector control strategy with id=0. A schematic diagram of the control system in this embodiment is shown below. Figure 3 As shown. The actual rotational speed ω of the multi-disc axial flux permanent magnet motor is detected by the detection unit in the system. mk (k=1,2……n), given the rotational speed ω ref With actual rotational speed ω mk (k=1,2……n) are compared, and the difference between the two is input to the speed controller. After adjustment by the speed controller, the output current i is obtained. qk(k=1,2……n), where the speed controller can use traditional PI control, various improved PI control methods, or suitable intelligent control methods; the detection unit can use an encoder, speed sensor, or displacement sensor to detect the actual speed ω of the multi-disc axial flux permanent magnet motor. mk .

[0021] Step 2: Detect the actual current i of the n disks using a current sensor. pk (p=a,b,c……m, where m is the number of phases of a multi-disc axial flux permanent magnet motor; k=1,2……n), after Clark transformation, the actual currents i of the n disks in the natural coordinate system are... pk Transform the variable i into a stationary coordinate system sk (s=α,β,…o2;k=1,2…n), then i sk (s=α,β,……o2; k=1,2……n) The actual d-axis and q-axis currents i of n disks are obtained through Park transformation. dak and i qak (k=1,2……n).

[0022] To better illustrate the coordinate transformation method of a multi-phase, multi-disc axial flux permanent magnet motor, the transformation matrices of Clark transformation and Park transformation will be explained below using a 6-phase (a, b, c, u, v, w phase) multi-disc axial flux permanent magnet motor as an example.

[0023] In the Clark transformation, the actual current i in the natural coordinate system of the disc motor is represented as... pk (p=a,b,c,u,v,w; k=1,2……n) Transform the variable i to the stationary coordinate system sk The transformation matrix of (s=α,β,……o2; k=1,2……n) is defined as Then we have: (k=1,2……n) (1) Where: transformation matrix for: (2) Transformation matrix The coefficient of 1 / 3 is used to ensure that the magnitude of the variable remains unchanged before and after the transformation. The first two lines correspond The three subspaces are orthogonal to each other. The middle two rows correspond to the xy subspace, and the last two rows correspond to the zero-order subspace.

[0024] In the Park transformation, the actual current i of the disc motor in the stationary coordinate system is represented as... sk(s=α,β,……o2; k=1,2……n) Transformed to the actual current i of the n disks' d-axis and q-axis in a synchronous rotating coordinate system dak and i qak The transformation matrix (k=1,2……n) is defined as (k=1,2……n), the relation can be obtained as: (3) Among them, the traditional transformation matrix for: (4) Step 3: Set the output current i of the speed controller qk (k=1,2……n) and the actual q-axis current i of n disks qak (k=1,2……n) Input current equalization controller, Figure 4 This is an example of a current equalization controller. After the current equalization controller is applied, the q-axis equalization current is obtained. (k=1,2……n).

[0025] The functions of the current balancing controller are as follows: (1) Find the actual current i of the q-axis of the n disks. qak The average of the maximum and minimum values ​​of (k=1,2……n) gives the current i. a = (max(i qak ) + min(i qak )) / 2; (2) Find the output current i of the n speed controllers. qk The average current i is obtained by averaging the values ​​of (k=1,2……n). qa = ; (3) Take the current i a and i qa The equilibrium value is obtained by deriving the q-axis equilibrium current for the n disks. .

[0026] Step 4: Equalize the current applied to the d-axis and q-axis of the n disks. (k=1,2……n) and the actual current i of n disks dak and i qak The differences (k=1,2……n) are input into the d-axis and q-axis current controllers of the n disks respectively, to obtain the given output voltages of the d-axis and q-axis of the n disks. (k=1,2……n) The α-axis and β-axis output voltages of the n disks are obtained after the inverse Park transformation. (k=1,2……n), where the current controller can be a traditional PI controller, or various improved PI control methods or a suitable intelligent control method.

[0027] Step 5: Output the given voltage based on the α-axis and β-axis of the n disks. (k=1,2……n) The motor control signal is generated by SVPWM or other modulation methods to drive the multi-disc axial flux permanent magnet motor.

[0028] As a specific embodiment, when the actual rotational speed ω of the n disks of the multi-disc axial flux permanent magnet motor is detected... mk When (k=1,2……n) are the same, that is: ω m1 =ω m2 =……=ω mn The output current i obtained through the speed controller q1 =i q2 =……= i qn At this time, the average current i qa = It can be directly connected to the current i a Equalization is performed to obtain the q-axis equalization current. .

[0029] Based on the aforementioned current balancing control method for multi-disc axial flux permanent magnet motors, the control system for these motors can utilize a structure of one controller + n drive circuit modules to control their operation, or it can employ an independent structure of n controllers + drive circuit modules. The controller of the multi-disc axial flux permanent magnet motor control system completes signal acquisition, analysis, calculation, and sends control signals to the drive circuit modules. The controller can be a combination of MCU, DSP, FPGA, or various chips. The drive circuit modules of the multi-disc axial flux permanent magnet motor control system are connected to the stator of the m-phase multi-disc axial flux permanent magnet motor, completing the drive control of the motor. The drive circuit modules can use thyristors or field-effect transistors.

[0030] In summary, the control method and system for a multi-disc axial flux permanent magnet motor according to embodiments of the present invention, taking the multi-disc axial flux permanent magnet motor as the controlled object, achieves dynamic balancing of the stator current of the n discs during the operation of the multi-disc axial flux permanent magnet motor, improves the dynamic performance of current balancing, effectively avoids the phenomenon of uneven heating of the stator discs of the multi-disc axial flux permanent magnet motor, reduces torque pulsation, extends the service life of the motor and bearings, and enhances the stability and overall performance of the system.

[0031] Obviously, the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A current balancing control method for a multi-disc axial flux permanent magnet motor, wherein the multi-disc axial flux permanent magnet motor is an axially stacked combination of multiple single-disc motors, or a stator and rotor arranged coaxially at intervals, comprising n axially stacked stator disks, where n is greater than or equal to 2, and permanent magnets are fixedly mounted on the rotor, with the stator and rotor coaxial, characterized in that... Includes the following steps: Step 1: The multi-disc axial flux permanent magnet motor adopts a dual closed-loop control system with n speed and current loops, including n current loops and n speed loops, with the current loop being the inner loop and the speed loop being the outer loop; the actual speed of the multi-disc axial flux permanent magnet motor is detected by a detection unit. , give the speed Compared with actual speed The difference is input to the speed controller, and the output current is obtained after adjustment by the speed controller. , parameter k = 1, 2, ..., n; Step 2: Detect the actual current of n stator disks p = a, b, c...m, where m is the number of phases of a multi-disc axial flux permanent magnet motor; The actual d-axis and q-axis currents of the n stator disks are obtained after Clark and Park transformations. ; Step 3: Adjust the output current of the speed controller. and the actual q-axis current of n stator disks The input current equalization controller, after passing through the current equalization controller, produces the q-axis equalization current. ; Step 4: Equalize the given current along the d-axis and q-axis of the n stator disks. and With the actual current of n stator disks The difference is input into the d-axis and q-axis current controllers of the n stator disks, respectively, to obtain the given output voltages of the n stator disks along the d-axis and q-axis. and , and The α-axis and β-axis output voltages of the n stator disks are obtained after the inverse Park transformation. and ; Step 5: Output the given voltage based on the α-axis and β-axis of the n stator disks. and The motor control signal is generated by SVPWM or other modulation methods to drive the multi-disc axial flux permanent magnet motor.

2. The current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 1, characterized in that, The functions of the current equalization controller include: Find the actual q-axis current of n stator disks. The average of the maximum and minimum values ​​yields the current. ; Find the output current of n speed controllers The average value is used to obtain the average current. ; Take current and The equilibrium value is used to obtain the q-axis equilibrium current of the n stator disks. .

3. The current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 1, characterized in that, The detection unit for detecting the actual rotational speed of the multi-disc axial flux permanent magnet motor is used to detect the speed using an encoder, speed sensor, or displacement sensor.

4. The current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 1, characterized in that, The actual current of the n stator disks of the multi-disc axial flux permanent magnet motor Detected by a current sensor.

5. The current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 1, characterized in that, The speed controller or current controller adopts a traditional PI control method, various improved PI control methods, or a suitable intelligent control method.

6. The current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 1, characterized in that, The control system of the multi-disc axial flux permanent magnet motor adopts a vector control strategy.

7. A current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 1 or 6, characterized in that, The multi-disc axial flux permanent magnet motor control system uses a structure of one controller + n drive circuit modules to control the motor operation, or uses a structure of independent n controllers + n drive circuit modules to control the motor operation.

8. The current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 7, characterized in that, The controller of the multi-disc axial flux permanent magnet motor control system completes the system's signal acquisition, analysis, calculation, and sends control signals to the drive circuit module; the drive circuit module of the multi-disc axial flux permanent magnet motor control system is connected to the stator of the m-phase multi-disc axial flux permanent magnet motor to complete the drive control of the multi-disc axial flux permanent magnet motor.

9. A current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 8, characterized in that, The controller of the multi-disc axial flux permanent magnet motor control system adopts a combination of MCU, DSP, FPGA and various chips.

10. A current balancing control method for a multi-disc axial flux permanent magnet motor according to claim 8, characterized in that, The drive circuit module of the multi-disc axial flux permanent magnet motor control system uses thyristors or field-effect transistors.

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