A Sensorless Switching Method for Permanent Magnet Synchronous Motor Based on I / F Starting

Abstract

The present invention discloses a speed sensorless switching method for a permanent magnet synchronous motor based on I / F starting. The method comprises: setting I / F starting parameters, including a given current value and mechanical angular acceleration, based on the permanent magnet synchronous motor parameters and load; using a pre-positioning method to find the motor's initial position and perform I / F starting; after the I / F starting reaches the set switching speed, switching into a current regulation transition process; designing a feedback regulator to regulate the current, and after the current regulation decreases and remains stable, switching into speed and current dual closed-loop control based on a back-electromotive force speed observer. The present invention incorporates a feedback regulator consisting of a PI regulator and an angle difference regulator into the I / F starting process. This allows the motor to automatically adjust the relationship between current and angle difference during the transition process before switching, ensuring matching between current and input position angle before and after switching, thereby increasing system stability and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of speed sensorless control of permanent magnet synchronous motors, and in particular to a speed sensorless switching method of permanent magnet synchronous motors based on I / F starting. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in production and everyday life due to their high power density, high efficiency, high reliability, and simple control. These motors often employ field-oriented control, which requires speed and rotor position information. Mechanical sensors are typically used to control these motors. However, these sensors take up considerable space, increase production costs, and carry the risk of failure. Therefore, sensorless control of PMSMs has high economic value and practical significance, and is currently a hot topic of research for scholars both domestically and internationally.

[0003] When a permanent magnet synchronous motor is running at medium or high speeds, methods such as sliding mode observers, state observers, and model-referenced adaptive observers can be used. These methods collect motor current and voltage information and observe speed and position based on the motor's back-EMF model. However, when the permanent magnet synchronous motor is running at zero or low speed, methods based on the motor's back-EMF model often fail due to the low signal-to-noise ratio of the collected signal. To avoid this, the motor can be started using a constant current variable frequency (I / F) method. When it reaches a certain speed, it switches to a speed observation method based on the back-EMF model, enabling stable, sensorless operation of the permanent magnet synchronous motor across the entire speed range.

[0004] The I / F starting strategy is a closed-loop current, open-loop speed control method. By assigning a new current rotation vector to the original synchronous coordinate system, the current vector is constantly accelerated to a specified speed. This drives the motor's rotor to rotate based on the "torque-power angle self-balancing" principle. After reaching the specified speed, the permanent magnet synchronous motor's speed fluctuates around the specified speed and gradually converges to the given value. During the switchover to the speed observer based on the back-EMF model, there is an angular difference between the rotor position angle assigned by the I / F starting method and the rotor position angle observed by the observer. This leads to a mismatch between the current and rotor position angle before and after the switchover, causing a sudden change in motor torque and thus affecting motor operational stability. Therefore, improvements are needed to the switching method used in the I / F control process. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the defects in the existing technology and provide a speed sensorless switching method for a permanent magnet synchronous motor based on I / F starting, aiming to solve the problems of torque mutation and unstable motor operation caused by the mismatch between current and position angle during the process of switching to a speed observation method based on a back electromotive force model after traditional I / F starting.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] The present invention provides a speed sensorless switching method for a permanent magnet synchronous motor based on I / F starting, the method comprising the following steps:

[0008] Step 1: Set the starting parameters of I / F starting according to the permanent magnet synchronous motor parameters and load, including the given current value and mechanical angular acceleration;

[0009] Step 2: Use the pre-positioning method to find the initial position of the motor and perform I / F starting according to the set starting parameters;

[0010] Step 3: After the I / F starts and reaches the switching set speed, it enters the transition process of current regulation;

[0011] Step 4: Design a feedback regulator to regulate the current. After the current regulation decreases and remains stable, switch to the speed and current dual closed-loop control based on the back electromotive force speed observer.

[0012] Furthermore, the method for setting a given current value in step 1 of the present invention includes:

[0013] According to the torque equation of the motor, the relationship between the current and load during motor acceleration is obtained:

[0014]

[0015] Further get the given current i q * The value range of is:

[0016]

[0017] Among them, T e is the motor torque, p n is the number of magnetic pole pairs of the permanent magnet synchronous motor, Ψ f is the permanent magnet flux, θ is the angle between the given current vector and the motor rotor q axis, T L is the load torque. Select the appropriate current value i within the above range q * As I / F starting given current.

[0018] Furthermore, the method for setting the mechanical angular acceleration in step 1 of the present invention includes:

[0019] When the angle between the current vector and the q-axis of the motor rotor is zero, the instantaneous acceleration of the motor is maximum. Ignoring the viscous friction coefficient, the maximum mechanical angular acceleration of the motor at a given current amplitude is obtained from the mechanical equation of the motor:

[0020]

[0021] The starting setting mechanical angular acceleration range is:

[0022] 0≤a e ≤a r

[0023] Where J is the motor's moment of inertia, ar is the maximum mechanical angular acceleration at a given current when the motor is started by the I / F, and ae is the motor's given mechanical angular acceleration.

[0024] Furthermore, the method of step 2 of the present invention comprises:

[0025] Integrate the given mechanical angular acceleration ae of the motor to get the given speed ω of the motor * ;

[0026] Then for a given speed ω * Integrate to get the electrical angle of motor rotation:

[0027]

[0028] Use the motor pre-positioning method to find the initial position of the motor, and then the I / F starting given input angle is:

[0029]

[0030] Among them, θ * The electrical angle of the I / F starting position command input, θ if * is the electrical angle of motor rotation, θ0 is the initial electrical angle of the motor; the motor I / F starts with the above set values.

[0031] Furthermore, the method for designing a feedback regulator in step 4 of the present invention includes:

[0032] According to the speed sensorless observation method based on back electromotive force at medium and high speed, the estimated rotor electrical angle θ is obtained. e ;

[0033] According to the position angle given by I / F, the angle difference is obtained:

[0034] θ err =θ e -θ *

[0035] Design a feedback regulator, using θ err As the input of the feedback regulator to adjust the feedback current;

[0036] The input-output relationship of the feedback regulator is:

[0037]

[0038] After adding the feedback regulator, the control current i q for:

[0039]

[0040] In the feedback regulator, the input-output relationship of the designed angle difference regulator is:

[0041] e(t)=k e θ err

[0042] in,

[0043] Among them, k p 、k i ,λ,n are adjustable parameters, is the feedback current, k e is the angle adjustment coefficient, and e(t) is the output of the angle difference regulator.

[0044] Furthermore, the method of step 4 of the present invention includes:

[0045] Under the action of the feedback regulator, the given current of the q-axis is automatically adjusted to decrease and remain stable. After the current stabilizes, the speed and current dual closed-loop control based on the back electromotive force speed observer can be switched into.

[0046] The beneficial effects of the present invention are as follows: the speed sensorless switching method of the permanent magnet synchronous motor based on I / F starting of the present invention adds a feedback regulator consisting of a PI regulator and an angle difference regulator during the starting of the I / F control method, so that the relationship between the current and the angle difference is automatically adjusted during the transition process of the motor switching to the speed observation method based on the back electromotive force model, which not only ensures the matching of the current and the input position angle before and after switching, but also increases the stability and reliability of the system, and compared with the ordinary method, it also eliminates the step of setting the current switching threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0048] Figure 1 This is a structural block diagram of a permanent magnet synchronous motor speed sensorless control system based on I / F starting of the present invention;

[0049] Figure 2 This is a flow chart of a speed sensorless switching method for a permanent magnet synchronous motor based on I / F starting of the present invention;

[0050] Figure 3This is a schematic diagram of the principle of a feedback regulator in a speed sensorless switching method of a permanent magnet synchronous motor based on I / F starting according to the present invention;

[0051] Figure 4 This is a comparison chart of the speed change curves during the transition process with and without an angle difference regulator under load starting;

[0052] Figure 5 This is a comparison of the current change curves during the transition process with and without an angle difference regulator under load starting. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0054] like Figure 1 The block diagram shows the structure of a sensorless speed control system for a permanent magnet synchronous motor based on I / F starting according to the present invention. This vector control system first performs I / F starting with given parameters. After the I / F starting speed reaches the set switching speed, k1 is switched to enter the transition process of automatic current regulation. After the current stabilizes, k2 and k3 are switched to enter sensorless speed and current closed-loop control. In closed-loop control, the current and voltage in the α and β coordinates obtained by sampling the three-phase current and voltage signals are obtained through Clarke transformation. The motor speed and rotor position information are obtained through a state observer based on back-electromotive force.

[0055] like Figure 2 As shown, the speed sensorless switching method of a permanent magnet synchronous motor based on I / F starting according to an embodiment of the present invention specifically includes the following steps:

[0056] Step 1: Select the appropriate starting current and starting mechanical angular acceleration;

[0057] According to the torque equation of the motor, the relationship between the current and load during motor acceleration can be obtained:

[0058]

[0059] We can further get the given current i q * The value range of is:

[0060]

[0061] Where T e is the motor torque, p n is the number of magnetic pole pairs of the permanent magnet synchronous motor, Ψ fis the permanent magnet flux, θ is the angle between the current vector and the q axis of the motor rotor, T L is the load torque. Select the appropriate current value i within the above range q * Used as I / F starting given current.

[0062] When the angle between the current vector and the q-axis of the motor rotor is zero, the instantaneous acceleration of the motor is maximum. Ignoring the viscous friction coefficient, the maximum mechanical angular acceleration of the motor at a given current amplitude can be obtained from the mechanical equation of the motor:

[0063]

[0064] It can be seen that the mechanical angular acceleration range of the startup setting is:

[0065] 0≤a e ≤a r ;

[0066] Where, J is the moment of inertia of the motor, a r is the maximum mechanical angular acceleration under the given current when the motor I / F starts, a e Give the motor a mechanical angular acceleration.

[0067] Step 2: Use the parameters set in step 1 to start the motor with I / F. Based on the motor's "torque-power angle self-balancing" performance, the motor is accelerated around the given speed during starting.

[0068] will a e Multiplying it by the starting time t can give the speed at a given uniform acceleration start;

[0069] ω * =a e t

[0070] Then for a given speed ω * Integrate and get the given electrical angle of motor rotation:

[0071]

[0072] Use the motor pre-positioning method to find the initial position angle of the motor, and then the I / F starting given input angle is:

[0073]

[0074] where ω * is the given speed for the motor to start with uniform acceleration, θ * The electrical angle of the I / F starting position command input, θ if *is the electrical angle obtained by applying a given mechanical angular acceleration to the motor using I / F startup, and θ0 is the motor's initial electrical angle. When the motor is started using I / F startup, the transition phase to step 3 begins after the speed stabilizes.

[0075] After the motor enters the switching set speed, it enters the transition process of current regulation.

[0076] The design of the closed-loop regulator in step 4 specifically includes:

[0077] According to the observation method based on the motor back electromotive force model at medium and high speed, the estimated rotor electrical angle θ is obtained e At this time, the observer can accurately observe the position of the motor at medium and high speeds, so the position angle obtained by the observer is used to replace the actual position angle of the motor;

[0078] The angle difference is obtained by subtracting the observation angle obtained by the observer from the position angle given by the I / F:

[0079] θ err =θ e -θ *

[0080] The angle difference reflects the relationship between the given control angle and the actual control angle in the I / F control transition state. The angle difference information is used as the input of the feedback regulator to automatically adjust the given current.

[0081] Design a feedback regulator, using θ err As the input of the entire feedback regulator to adjust the feedback current; the input and output relationship of the entire feedback regulator is:

[0082]

[0083] After adding the feedback regulator, the control current i q for:

[0084]

[0085] Reference Figure 3 ,The feedback regulator is composed of a PI regulator and an angle difference regulator.,The angle difference is adjusted before the PI regulator;

[0086] Among them, the input and output relationship of the angle difference regulator is:

[0087] e(t)=k e θ err

[0088] in,

[0089] Among them, k p 、ki ,λ,n are adjustable parameters, is the feedback current, k e is the angle adjustment coefficient, and e(t) is the output of the angle difference regulator.

[0090] The control parameters of the feedback regulator module include k p 、k i , the rate of decrease of the process current can be controlled and regulated.

[0091] The control parameters of the angle difference regulator module include λ and n, which can control the current to drop to a certain value and the matching degree of the speed and current dual closed-loop control.

[0092] Under the action of the feedback regulator, the given current of the q axis automatically decreases and remains stable. After the current stabilizes, the speed and current dual closed-loop control based on the back electromotive force speed observer can be switched into.

[0093] The following combination Figures 4 and 5 The feasibility of the present invention is verified by the simulation waveform.

[0094] Figure 4 This figure compares the speed curves during the transient process of the present invention's load starting process with and without an angular differential regulator in the feedback regulator. The I / F starting current is set at 10A, and the speed is accelerated to 600 r / min and then maintained constant. The feedback regulator is then engaged to adjust the q-axis current. With the angular differential regulator, the speed remains stable during the transient process. Without the angular differential regulator, the speed begins to diverge, causing the motor to lose steps.

[0095] Figure 5 The present invention is a comparison of the current change curves of the feedback regulator with and without the angle difference regulator during the transition process under load starting. It can be seen that when the current decreases to a certain value, the current begins to diverge in the case of the angle difference regulator. This is because as the current decreases during the transition process, the current change has an impact on the angle difference θ. err The influence of θ gradually increases. err = 0 working point, if the speed and current dual closed-loop control is not switched in time, a small current fluctuation will cause θ err After adding the angle difference regulator of the present invention, the current can be kept stable in the transition state while solving the speed divergence problem, thus ensuring the stability of the motor during the transition process.

[0096] The present invention improves the switching process in the transition state after I / F starting. A feedback regulator is designed based on the relationship between a given current and an angle difference. The given current is adjusted by the feedback regulator without setting a switching current threshold. After the current stabilizes, a back electromotive force observation method suitable for medium and high-speed speed sensorless control is used, so that the current and rotor angle before and after switching tend to be consistent, eliminating the influence of torque mutation and improving the stability of the system.

[0097] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A speed sensorless switching method for a permanent magnet synchronous motor based on I / F starting, characterized in that: The method comprises the following steps: Step 1: Set the starting parameters of I / F starting according to the permanent magnet synchronous motor parameters and load, including the given current value and mechanical angular acceleration; Step 2: Use the pre-positioning method to find the initial position of the motor and perform I / F starting according to the set starting parameters; Step 3: After the I / F starts and reaches the switching set speed, it enters the transition process of current regulation; Step 4: Design a feedback regulator to regulate the current. After the current is reduced and remains stable, switch to the speed and current dual closed-loop control based on the back electromotive force speed observer; The method for designing the feedback regulator in step 4 includes: The estimated rotor electrical angle is obtained based on the speed sensorless observation method based on the motor back electromotive force at medium and high speeds. ; According to the position angle given by I / F, the angle difference is obtained: Design a feedback regulator with As the input of the feedback regulator to adjust the feedback current; The input-output relationship of the feedback regulator is: After adding the feedback regulator, the control current is obtained i q for: In the feedback regulator, the input-output relationship of the designed angle difference regulator is: in, ; in, k p 、k i 、 、n is an adjustable parameter, is the feedback current, k e is the angle adjustment coefficient, e ( t ) is the output of the angle difference regulator.

2. The method for switching a permanent magnet synchronous motor without a speed sensor based on I / F starting according to claim 1, characterized in that: The method for setting the given current value in step 1 includes: According to the torque equation of the motor, the relationship between the current and load during motor acceleration is obtained: Further get the given current i q * The value range of is: in, T e is the motor torque, p n is the number of magnetic pole pairs of the permanent magnet synchronous motor, Ψ f is the permanent magnet flux, θ Given the current vector and the motor rotor q The angle of the axis, T L For the load torque, select a suitable current value within the above range. i q * Used as I / F starting given current.

3. The method for switching a permanent magnet synchronous motor without a speed sensor based on I / F starting according to claim 2, characterized in that: The method for setting the mechanical angular acceleration in step 1 includes: When the current vector and the motor rotor q The instantaneous acceleration of the motor is maximum when the shaft angle is zero. Ignoring the viscous friction coefficient, the maximum mechanical angular acceleration of the motor at a given current amplitude is obtained from the mechanical equation of the motor: The starting setting mechanical angular acceleration range is: in, J is the moment of inertia of the motor, The maximum mechanical angular acceleration of the motor I / F at a given starting current, is the mechanical angular acceleration given to the motor.

4. The method for switching a permanent magnet synchronous motor without a speed sensor based on I / F starting according to claim 1, characterized in that: The method of step 2 comprises: Give the motor a given mechanical angular acceleration Integrate to get the given speed of the motor ; Then for a given speed The electrical angle of the motor rotation is obtained by integration: Use the motor pre-positioning method to find the initial position of the motor, and then the I / F starting given input angle is: in, The electrical angle of the I / F starting position command input, is the electrical angle of motor rotation, is the initial electrical angle of the motor; use the above set value to start the motor I / F.

5. The method for switching a permanent magnet synchronous motor without a speed sensor based on I / F starting according to claim 1, characterized in that: The method of step 4 includes: Under the action of the feedback regulator, q The given current of the shaft is automatically adjusted to decrease and remain stable. After the current stabilizes, the speed and current dual closed-loop control based on the back electromotive force speed observer can be switched into.

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