Closed-loop switching control method and controller for non-inductive starting of permanent magnet synchronous motor

Abstract

The invention discloses a closed-loop switching control method for non-inductive starting of a permanent magnet synchronous motor and a controller, and relates to the technical field of motor control, and the method comprises the following steps: S1, when the motor is static or at a low speed, giving an open-loop angle and instruction current to drive the motor to rotate; s2, estimating the rotating speed and angle of the rotor in real time to obtain an observation rotating speed and an observation angle; s3, when the rotating speed reaches a switching threshold value, according to the real-time error of the open-loop angle and the observation angle, the instruction current is dynamically corrected through closed-loop feedback adjustment, and the open-loop angle is forced to be automatically converged to the observation angle; and S4, when the real-time error is lower than a stable threshold value, switching to a closed-loop operation mode based on the observation angle. According to the method, the instruction current is dynamically corrected, the open-loop angle is not directly modified, the open-loop angle is automatically converged to the observation angle according to the motor power self-balancing principle, and torque zero-impact smooth switching is achieved.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, specifically to a closed-loop switching control method and controller for sensorless starting of a permanent magnet synchronous motor. Background Technology

[0002] Currently, sensorless algorithms in brushless DC motor control mainly employ model-based control methods. At low speeds, the voltage and back EMF are small, making closed-loop control impossible. However, at high speeds, they can operate stably without noise and have minimal requirements regarding motor type. Regarding the issue of low-speed starting difficulties, current sensorless starting methods for brushless DC motors primarily involve initial induction (IF) starting. Once the speed reaches a certain threshold, the sensorless observer functions correctly, obtaining the accurate angle. At this point, the system switches to sensorless closed-loop operation. During startup, the brushless motor speed and current are both zero, making it impossible to obtain the actual motor angle. Initially, an open-loop method is used, where the motor angle is manually set along with a command current, causing the motor to rotate open-loop. Once the speed reaches a certain level, the sensorless method is activated. After the sensorless algorithm stabilizes, the angle used to control the motor must be switched from the open-loop angle to the sensorless estimated angle. Because there is a deviation between the open-loop given angle and the sensorless estimated angle, a strategy is often designed to ensure a smooth transition from the open-loop angle to the sensorless estimated angle.

[0003] For angle switching, there are methods using variable-rate switching, such as sinusoidal curve switching. This method uses a small accumulated value at the beginning of the switching, a larger accumulated value in the middle, and then switches to a smaller accumulated value when approaching the sensorless estimated angle. This ensures a fast and smooth switching effect. However, the sinusoidal curve switching scheme has the following technical problems: First, it involves a large amount of computation. Many single motors do not support sinusoidal calculations, requiring a custom lookup table function, which increases program complexity and requires additional memory to store the table. Second, the sinusoidal curve is planned based on the open-loop angle and the estimated angle error at the start-up moment. However, in practical applications, the open-loop angle and estimated angle may fluctuate, resulting in the error angle not being small at the moment of switching to the sensorless estimated angle, leading to a large angle step and switching failure. For example, Chinese patent CN106788066B discloses a method for sensorless PMSM vector control angle tracking switching to start a compressor. During the acceleration start-up process, it detects the angle difference between the preset angle and the actual angle of the rotor and controls the angle difference to gradually decrease by adjusting the size of the preset angle. Summary of the Invention

[0004] To achieve efficient and stable angle switching during sensorless starting of a motor, this invention proposes a closed-loop switching control method and controller for sensorless starting of a permanent magnet synchronous motor. By dynamically correcting the command current instead of directly modifying the open-loop angle, the open-loop angle is automatically converged to the observed angle using the motor power self-balancing principle, thus achieving smooth switching with zero torque impact.

[0005] A further objective of this invention is to eliminate the preset transition process and perform closed-loop feedback adjustment in real time based on the current state of the system, thereby improving the stability and reliability of the system during the switching process and increasing computational efficiency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor, comprising the following steps: S1, When the motor is stationary or at low speed, the given open-loop angle and command current drive the motor to rotate; S2, real-time estimation of rotor speed and angle, to obtain the observed speed and observed angle; S3, when the rotational speed reaches the switching threshold, the dynamic correction command current is adjusted through closed-loop feedback based on the real-time error between the open-loop angle and the observation angle, forcing the open-loop angle to automatically converge to the observation angle. S4, when the real-time error is lower than the stable threshold, switches to the closed-loop operation mode based on the observation angle.

[0007] In this technical solution, after starting the current feedforward control, the sensorless observer is also enabled to observe the angle and speed. When the speed is higher than a certain threshold, the sensorless observer can obtain the correct motor angle position. However, the current feedforward control is operated by actively setting the angle. It needs to transition from the given angle to the motor angle estimated by the angle observer. According to the principle of power self-balancing in motor control, the command current is modified in a closed loop to modify the given angle and the estimated angle by the observer, so that the motor automatically adjusts the speed to make the angle given by the current feedforward and the estimated angle close to equal. When the error between the two angles is less than the threshold, the switching can be completed smoothly.

[0008] Preferably, in step S3, the convergence of the open-loop angle is achieved by dynamically correcting the command current, without relying on a preset path and a fixed switching period.

[0009] Preferably, in step S3, when the observation angle is greater than the open-loop angle, the command current is reduced; when the observation angle is less than the open-loop angle, the command current is increased.

[0010] Preferably, in step S3, the dynamic correction command current is achieved through a closed-loop feedback controller, which includes a PID controller, a fuzzy controller, and a sliding mode controller.

[0011] Preferably, in step S3, the dynamic correction of the command current includes: S31, calculate the real-time error between the open-loop angle and the observed angle; S32 inputs the real-time error value into the closed-loop feedback controller to generate the command current correction amount; S33 dynamically adjusts the command current according to the command current correction amount.

[0012] Preferably, in step S1, the given open-loop angle and command current drive the motor to rotate are achieved using current feedforward control.

[0013] Preferably, in step S2, the rotor speed and angle are estimated in real time using a sliding diaphragm observer, an adaptive filter, an extended Kalman filter, or model predictive control.

[0014] Preferably, step S4 includes: S41, continuously detect the error values ​​of the open-loop angle and the observation angle, and determine that the system has reached a stable state when the error value is lower than the preset stability threshold; S42, completely stop current feedforward control and switch to drive the motor according to the observation data, including the observation angle and observation speed signals; S43, the closed-loop switching process ends, the motor enters the high-speed sensorless closed-loop control state, and the subsequent operation relies entirely on the observation data to estimate the state.

[0015] Preferably, in step S3, the switching threshold is dynamically adjusted according to the load status.

[0016] The present invention also adopts the following technical solution: a motor controller, which stores a computer program, and when the computer program is executed, implements the above-mentioned closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor.

[0017] The beneficial effects of this invention are: 1) The path planning stage is eliminated, and angle self-alignment is achieved directly through current adjustment, which reduces the amount of computation and saves the chip's memory usage; 2) Closed-loop switching can adjust the current and other parameters in real time according to the motor's operating conditions, which has stronger robustness, can better cope with sudden conditions, and avoids the failure of the pre-set transition process due to sudden load conditions during the switching process. 3) Utilizing the self-balancing physical characteristics of motor power, the switching speed can be adjusted according to the closed-loop PID parameters. The PID adjustment method is simple and easy. Attached Figure Description

[0018] Figure 1 This is a flowchart of a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to the present invention.

[0019] Figure 2 This is a control block diagram of the closed-loop switching control in Embodiment 2 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] First, it's important to note that a motor requires an angle to start. The ultimate goal of the motor startup phase is for the controller to use the FOC algorithm to orient the rotor magnetic field based on the actual rotor angle. An observer is used to estimate the actual rotor angle, but it requires the rotational speed to reach a threshold before it can output a reliable angle.

[0022] To resolve the conflict between the observer and the motor starting, an open-loop angle needs to be set for the controller to start the motor first. When the speed reaches the threshold, the observer can obtain a reliable actual angle of the motor rotor in real time, i.e., the real-time observation angle. At this point, the real-time observation angle can be used to replace the open-loop angle so that the controller can obtain the correct understanding and enter the seamless closed-loop operation.

[0023] However, it is easy to understand that if the open-loop angle is replaced with the observation angle at the moment the speed reaches the target, it will cause a sudden jump in the direction of the magnetic field and a sudden change in the direction of the electromagnetic torque, resulting in severe vibration of the motor or even loss of synchronization and stoppage. Therefore, it is necessary to smoothly transition the open-loop angle to the observation angle.

[0024] The core problem addressed by this invention is how to smoothly and efficiently transition the open-loop angle to the observation angle. The best existing solution is sinusoidal curve switching, a method that slowly approaches the initial observation angle using a fixed step size. When the rotational speed reaches the switching threshold, a switching path is planned with a fixed number of cycles based on the initial error between the open-loop angle and the observation angle. Based on a sinusoidal curve, the angle is periodically accumulated to compensate for the change, causing the open-loop angle to gradually approach the initial observation angle along a trajectory of "gradual initial change, rapid intermediate change, and gradual final change."

[0025] It's easy to see that the endpoint of the open-loop angle approximation in this scheme is a fixed value, namely the initial observed angle. However, the rotor angle changes in real time. When this angle switching process is completed, the actual rotor angle may deviate from the initial observed angle. Moreover, due to the rigidity and sluggish response of the switching process, this pre-defined path scheme is difficult to cope with sudden load changes. In addition, this scheme has a large computational load and requires a separate lookup table function, significantly increasing program complexity and storage space consumption.

[0026] Based on the above explanation, it is clear that the ultimate goal of angle switching is to make the open-loop angle approximate the observed angle, thereby enabling the FOC algorithm to generate a stator magnetic field leading by 90° based on the actual rotor position. Based on this, this invention discovers that the essence of angle switching is a torque balance problem, and solves the problems existing in the current scheme by replacing the preset path planning with dynamic current adjustment. The specific implementation method is as follows.

[0027] Example 1 This embodiment provides a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor, referencing... Figure 1 This includes the following steps.

[0028] When the motor is stationary or at a very low speed, the motor is driven to rotate by giving an open-loop angle and a command current. This step is the same as the existing technical solution, and the current feedforward (IF) method can be used for starting.

[0029] During startup, a sensorless observer is used to monitor the state, including back EMF, rotational speed, and angle. The sensorless observer can be a sliding diaphragm observer, an adaptive filter, an extended Kalman filter, or model predictive control can be used for state monitoring.

[0030] A switching threshold is preset, and when the rotational speed reaches the preset switching threshold, the closed-loop switching strategy is started.

[0031] The switching threshold here depends on the rotational speed requirement for the sensorless observer to output a reliable angle, and can be set to the minimum rotational speed at which the sensorless observer can output a reliable angle.

[0032] In this embodiment, the closed-loop switching strategy is implemented by a closed-loop switching controller. The closed-loop switching controller adjusts the command current in real time based on the feedback from the sensorless observer, thereby changing the error values ​​of the open-loop angle and the observation angle. When the system reaches a stable state, the switching is completed automatically, and then the system enters the standard sensorless closed-loop operation state.

[0033] Specifically, the input to the closed-loop switching controller is the real-time error signal between the open-loop angle and the observed angle. Based on this real-time error signal, the closed-loop controller dynamically adjusts the command current and uses the motor power self-balancing principle to force the given open-loop angle to actively converge to the angle estimated by the observer. When the error value between the open-loop angle and the observed angle is lower than the preset stability threshold, the system is determined to have reached a stable state.

[0034] It is worth noting that in this invention, the switching process does not depend on a fixed time or a preset path, but rather corrects the current command in real time through closed-loop feedback, and dynamically determines the switching timing based on the closed-loop error.

[0035] The principle of dynamically adjusting the command current to force the open-loop given angle to actively converge to the angle estimated by the observer is explained below.

[0036] In this technical solution, the power balance point is changed by adjusting the command current using the speed integral effect, so that the open-loop angle is automatically aligned with the observation angle.

[0037] When the controller dynamically corrects the command current based on the angle error, the motor system achieves angle convergence through the automatic balance of "electromagnetic torque - mechanical power" as follows: The controller outputs the command current, the stator coil generates a magnetic field, and the magnetic field interacts with the rotor permanent magnet to generate electromagnetic torque, causing the rotor to accelerate or decelerate. The load torque changes adaptively, reaching a new balance point between the load torque and the electromagnetic torque.

[0038] The open-loop angle is the integral of the rotor speed over time. The corrective command current can change the instantaneous speed, which accumulates into an angle offset through the integral effect.

[0039] When the observation angle is greater than the open-loop angle, it indicates that the rotor is ahead. At this time, reducing the command current reduces the electromagnetic torque and rotor speed, slows down the accumulation of the open-loop angle, and shows a trend of waiting for the observation angle to change.

[0040] When the observation angle is smaller than the open-loop angle, it indicates that the rotor is lagging. At this time, increasing the command current will increase the electromagnetic torque, increase the rotor speed, and accelerate the accumulation of the open-loop angle, showing a trend of catching up with the observation angle.

[0041] The entire handover process is completed in a closed loop, without relying on fixed time delays or planned paths, making the handover process smoother and more robust.

[0042] Existing sine curve switching methods directly modify the open-loop angle setting value. This invention adjusts the command current to trigger power self-balancing, and uses the motor's dynamic inertia to make the open-loop angle automatically approach the predicted angle, achieving smooth transition and zero-impact switching.

[0043] Example 2 This embodiment provides another implementation of a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor, including the following steps.

[0044] When the motor is stationary or at a very low speed, the motor is driven to rotate by giving an open-loop angle and a command current. This step is the same as the existing technical solution, and the current feedforward (IF) method can be used for starting.

[0045] During startup, an adaptive filter is used to observe the state, including back EMF, rotational speed, and angle.

[0046] A switching threshold is preset, and when the rotational speed reaches the preset switching threshold, the closed-loop switching strategy is started.

[0047] The switching threshold here depends on the rotational speed requirement for the sensorless observer to output a reliable angle, and can be set to the minimum rotational speed at which the sensorless observer can output a reliable angle.

[0048] In this embodiment, the closed-loop switching strategy is implemented by a PID controller. The PID controller adjusts the command current in real time based on the feedback from the sensorless observer, thereby changing the error values ​​of the open-loop angle and the observation angle. When the system reaches a stable state, the switching is completed automatically, and then it enters the standard sensorless closed-loop operation state.

[0049] Specifically, the input to the PID controller is the real-time error signal between the open-loop angle and the observed angle. The closed-loop controller dynamically adjusts the command current based on this real-time error signal, and uses the motor power self-balancing principle to force the given open-loop angle to actively converge to the angle estimated by the observer. When the error value between the open-loop angle and the observed angle is lower than the preset stability threshold, the system is determined to have reached a stable state.

[0050] It is worth noting that in this invention, the switching process does not depend on a fixed time or a preset path, but rather corrects the current command in real time through closed-loop feedback, and dynamically determines the switching timing based on the closed-loop error.

[0051] The principle of dynamically adjusting the command current to force the open-loop given angle to actively converge to the angle estimated by the observer is explained below.

[0052] In this technical solution, the power balance point is changed by adjusting the command current using the speed integral effect, so that the open-loop angle is automatically aligned with the observation angle.

[0053] When the controller dynamically corrects the command current based on the angle error, the motor system achieves angle convergence through the automatic balance of "electromagnetic torque - mechanical power" as follows: The controller outputs the command current, the stator coil generates a magnetic field, and the magnetic field interacts with the rotor permanent magnet to generate electromagnetic torque, causing the rotor to accelerate or decelerate. The load torque changes adaptively, reaching a new balance point between the load torque and the electromagnetic torque.

[0054] The open-loop angle is the integral of the rotor speed over time. The corrective command current can change the instantaneous speed, which accumulates into an angle offset through the integral effect.

[0055] When the observation angle is greater than the open-loop angle, it indicates that the rotor is ahead. At this time, reducing the command current reduces the electromagnetic torque and rotor speed, slows down the accumulation of the open-loop angle, and shows a trend of waiting for the observation angle to change.

[0056] When the observation angle is smaller than the open-loop angle, it indicates that the rotor is lagging. At this time, increasing the command current will increase the electromagnetic torque, increase the rotor speed, and accelerate the accumulation of the open-loop angle, showing a trend of catching up with the observation angle.

[0057] The entire handover process is completed in a closed loop, without relying on fixed time delays or planned paths, making the handover process smoother and more robust.

[0058] like Figure 2 As shown, the closed-loop switching control includes a PID controller module, a current correction module, a power self-balancing feedback loop, and an angle convergence module.

[0059] The PID controller module receives the real-time error signal between the open-loop angle and the observed angle. The current correction module dynamically adjusts the command current according to the PID output. The power self-balancing feedback loop drives the rotor speed adjustment through electromagnetic torque changes. The angle convergence module automatically approaches the observed angle based on the speed integral effect.

[0060] Existing sine curve switching methods directly modify the open-loop angle setting value. This invention adjusts the command current to trigger power self-balancing, and uses the motor's dynamic inertia to make the open-loop angle automatically approach the predicted angle, achieving smooth transition and zero-impact switching.

[0061] Example 3 This embodiment provides another implementation of a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor, including the following steps.

[0062] When the motor is stationary or at a very low speed, the motor is driven to rotate by giving an open-loop angle and a command current. This step is the same as the existing technical solution, and the current feedforward (IF) method can be used for starting.

[0063] During startup, a dual-observer fusion strategy is used to observe the state, including back EMF, rotational speed, and angle.

[0064] A sliding mode observer is used as the master observer to ensure fast response, and an extended Kalman filter is used as the auxiliary observer to improve noise immunity.

[0065] A switching threshold is preset, and when the rotational speed reaches the preset switching threshold, the closed-loop switching strategy is started.

[0066] The switching threshold here depends on the rotational speed requirement for the sensorless observer to output a reliable angle, and can be set to the minimum rotational speed at which the sensorless observer can output a reliable angle.

[0067] In this embodiment, the closed-loop switching strategy is implemented by a closed-loop switching controller. The closed-loop switching controller adjusts the command current in real time based on the feedback from the sensorless observer, thereby changing the error values ​​of the open-loop angle and the observation angle. When the system reaches a stable state, the switching is completed automatically, and then the system enters the standard sensorless closed-loop operation state.

[0068] Specifically, the input to the closed-loop switching controller is the real-time error signal between the open-loop angle and the observed angle. Based on this real-time error signal, the closed-loop controller dynamically adjusts the command current and uses the motor power self-balancing principle to force the given open-loop angle to actively converge to the angle estimated by the observer. When the error value between the open-loop angle and the observed angle is lower than the preset stability threshold, the system is determined to have reached a stable state.

[0069] It is worth noting that in this invention, the switching process does not depend on a fixed time or a preset path, but rather corrects the current command in real time through closed-loop feedback, and dynamically determines the switching timing based on the closed-loop error.

[0070] The principle of dynamically adjusting the command current to force the open-loop given angle to actively converge to the angle estimated by the observer is explained below.

[0071] In this technical solution, the power balance point is changed by adjusting the command current using the speed integral effect, so that the open-loop angle is automatically aligned with the observation angle.

[0072] When the controller dynamically corrects the command current based on the angle error, the motor system achieves angle convergence through the automatic balance of "electromagnetic torque - mechanical power" as follows: The controller outputs the command current, the stator coil generates a magnetic field, and the magnetic field interacts with the rotor permanent magnet to generate electromagnetic torque, causing the rotor to accelerate or decelerate. The load torque changes adaptively, reaching a new balance point between the load torque and the electromagnetic torque.

[0073] The open-loop angle is the integral of the rotor speed over time. The corrective command current can change the instantaneous speed, which accumulates into an angle offset through the integral effect.

[0074] When the observation angle is greater than the open-loop angle, it indicates that the rotor is ahead. At this time, reducing the command current reduces the electromagnetic torque and rotor speed, slows down the accumulation of the open-loop angle, and shows a trend of waiting for the observation angle to change.

[0075] When the observation angle is smaller than the open-loop angle, it indicates that the rotor is lagging. At this time, increasing the command current will increase the electromagnetic torque, increase the rotor speed, and accelerate the accumulation of the open-loop angle, showing a trend of catching up with the observation angle.

[0076] The entire handover process is completed in a closed loop, without relying on fixed time delays or planned paths, making the handover process smoother and more robust.

[0077] Existing sine curve switching methods directly modify the open-loop angle setting value. This invention adjusts the command current to trigger power self-balancing, and uses the motor's dynamic inertia to make the open-loop angle automatically approach the predicted angle, achieving smooth transition and zero-impact switching.

[0078] Example 4 This embodiment provides another implementation of a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor, including the following steps.

[0079] When the motor is stationary or at a very low speed, the motor is driven to rotate by giving an open-loop angle and a command current. This step is the same as the existing technical solution, and the current feedforward (IF) method can be used for starting.

[0080] During startup, model predictive control is used to observe the state, including back EMF, rotational speed, and angle.

[0081] A switching threshold is preset, and when the rotational speed reaches the preset switching threshold, the closed-loop switching strategy is started.

[0082] The switching threshold here depends on the rotational speed requirement for the sensorless observer to output a reliable angle, and can be set to the minimum rotational speed at which the sensorless observer can output a reliable angle.

[0083] In this embodiment, the closed-loop switching strategy is implemented by a closed-loop switching controller. The closed-loop switching controller adjusts the command current in real time based on the feedback from the sensorless observer, thereby changing the error values ​​of the open-loop angle and the observation angle. When the system reaches a stable state, the switching is completed automatically, and then the system enters the standard sensorless closed-loop operation state.

[0084] Specifically, the input to the closed-loop switching controller is the real-time error signal between the open-loop angle and the observed angle. Based on this real-time error signal, the closed-loop controller dynamically adjusts the command current and uses the motor power self-balancing principle to force the given open-loop angle to actively converge to the angle estimated by the observer. When the error value between the open-loop angle and the observed angle is lower than the preset stability threshold, the system is determined to have reached a stable state.

[0085] It is worth noting that in this invention, the switching process does not depend on a fixed time or a preset path, but rather corrects the current command in real time through closed-loop feedback, and dynamically determines the switching timing based on the closed-loop error.

[0086] The principle of dynamically adjusting the command current to force the open-loop given angle to actively converge to the angle estimated by the observer is explained below.

[0087] In this technical solution, the power balance point is changed by adjusting the command current using the speed integral effect, so that the open-loop angle is automatically aligned with the observation angle.

[0088] When the controller dynamically corrects the command current based on the angle error, the motor system achieves angle convergence through the automatic balance of "electromagnetic torque - mechanical power" as follows: The controller outputs the command current, the stator coil generates a magnetic field, and the magnetic field interacts with the rotor permanent magnet to generate electromagnetic torque, causing the rotor to accelerate or decelerate. The load torque changes adaptively, reaching a new balance point between the load torque and the electromagnetic torque.

[0089] The open-loop angle is the integral of the rotor speed over time. The corrective command current can change the instantaneous speed, which accumulates into an angle offset through the integral effect.

[0090] When the observation angle is greater than the open-loop angle, it indicates that the rotor is ahead. At this time, reducing the command current reduces the electromagnetic torque and rotor speed, slows down the accumulation of the open-loop angle, and shows a trend of waiting for the observation angle to change.

[0091] When the observation angle is smaller than the open-loop angle, it indicates that the rotor is lagging. At this time, increasing the command current will increase the electromagnetic torque, increase the rotor speed, and accelerate the accumulation of the open-loop angle, showing a trend of catching up with the observation angle.

[0092] The entire handover process is completed in a closed loop, without relying on fixed time delays or planned paths, making the handover process smoother and more robust.

[0093] Existing sine curve switching methods directly modify the open-loop angle setting value. This invention adjusts the command current to trigger power self-balancing, and uses the motor's dynamic inertia to make the open-loop angle automatically approach the predicted angle, achieving smooth transition and zero-impact switching.

[0094] Example 5 This embodiment provides a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor. Based on embodiment 1, the switching threshold is dynamically adjusted according to the load status.

[0095] The load condition has a certain impact on the observer: under light load, the back EMF signal is clear, and the observer can output a reliable angle at a lower speed; under heavy load, the current noise interference increases, and a higher speed is required for the back EMF signal strength to exceed the noise; if the load changes abruptly, the instantaneous load change causes the observation angle to jitter, and the threshold needs to be increased to ensure the stability of the observation.

[0096] In this embodiment, a dynamic adjustment mechanism for the switching threshold is incorporated. The minimum reliable speed under no-load conditions is used as a benchmark, and the product of the load factor and the load compensation coefficient is used as a correction factor to map the benchmark. The load factor is obtained by the ratio of real-time load torque to the motor's rated torque. The load torque is estimated in real-time using the q-axis current or converted from the DC bus current.

[0097] Example 6 This embodiment provides a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor, which adds exception handling logic based on embodiment 1.

[0098] When the error between the open-loop angle and the observed angle exceeds the abnormal threshold, the current correction is frozen, the initial current feedforward control is restored, and the switching is triggered again.

Claims

1. A closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor, characterized in that, Includes the following steps: S1, When the motor is stationary or at low speed, the given open-loop angle and command current drive the motor to rotate; S2, real-time estimation of rotor speed and angle, to obtain the observed speed and observed angle; S3, when the rotational speed reaches the switching threshold, the dynamic correction command current is adjusted through closed-loop feedback based on the real-time error between the open-loop angle and the observation angle, forcing the open-loop angle to automatically converge to the observation angle. S4, when the real-time error is lower than the stable threshold, switches to the closed-loop operation mode based on the observation angle.

2. The closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 1, characterized in that, In step S3, the convergence of the open-loop angle is achieved by dynamically correcting the command current, without relying on a preset path or a fixed switching period.

3. A closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 1 or 2, characterized in that, In step S3, when the observation angle is greater than the open-loop angle, the command current is reduced; when the observation angle is less than the open-loop angle, the command current is increased.

4. A closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 1 or 2, characterized in that, In step S3, the dynamic correction command current is achieved through a closed-loop feedback controller, which includes a PID controller, a fuzzy controller, and a sliding mode controller.

5. The closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 4, characterized in that, In step S3, the dynamic correction of the command current includes: S31, calculate the real-time error between the open-loop angle and the observed angle; S32 inputs the real-time error value into the closed-loop feedback controller to generate the command current correction amount; S33 dynamically adjusts the command current according to the command current correction amount.

6. The closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 1, characterized in that, In step S1, the given open-loop angle and command current drive the motor to rotate using current feedforward control.

7. The closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 1, characterized in that, In step S2, the rotor speed and angle are estimated in real time using a sliding diaphragm observer, an adaptive filter, an extended Kalman filter, or model predictive control.

8. The closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 1, characterized in that, Step S4 includes: S41, continuously detect the error values ​​of the open-loop angle and the observation angle, and determine that the system has reached a stable state when the error value is lower than the preset stability threshold; S42, completely stop current feedforward control and switch to drive the motor according to the observation data, including the observation angle and observation speed signals; S43, the closed-loop switching process ends, the motor enters the high-speed sensorless closed-loop control state, and the subsequent operation relies entirely on the observation data to estimate the state.

9. The closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor according to claim 1, characterized in that, In step S3, the switching threshold is dynamically adjusted according to the load status.

10. A motor controller, characterized in that, The device contains a computer program that, when executed, implements a closed-loop switching control method for sensorless starting of a permanent magnet synchronous motor as described in any one of claims 1 to 9.

Images