Speed sensorless vector control starting self-adaptive adjustment method for asynchronous motor

Abstract

The invention relates to a speed sensorless vector control starting self-adaptive adjustment method for an asynchronous motor, and belongs to the technical field of motor control. Aiming at the problems of starting failure and incapability of self-adjustment caused by misalignment of rotating speed estimation and insufficient starting torque during low-speed starting of speed sensorless vector control, a solution based on dynamic comparison of a dual-stage frequency criterion and a modulation degree is provided. The technical scheme comprises the following steps: pre-exciting to establish a stable magnetic field; the low-frequency band takes the filtering rotating speed as feedback frequency rising, and first and second frequency judgment points are set; the starting state is judged according to the difference value between the given frequency and the modulation degree module value, the pulse is blocked and the acceleration time is adaptively prolonged in case of failure, and restarting is performed after the exciting current is increased. According to the method, starting failure can be accurately recognized, control parameters are dynamically optimized, the defects that a traditional method is high in misjudgment rate and insufficient in starting torque are overcome, the starting success rate of heavy loads or high static friction loads is remarkably increased, the system stability and self-healing capacity are enhanced, and overcurrent damage is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of motor control and relates to a speed sensorless vector control starting adaptive adjustment method for an asynchronous motor. Background Art

[0002] Vector control of asynchronous motors requires closed-loop speed estimation. Speed acquisition methods include speed encoders and sensorless algorithms. Sensorless methods are widely used because they eliminate the need for hardware sensors, maintaining a simple and robust motor structure. However, this method suffers from two major technical bottlenecks: First, the speed estimation algorithm lacks accuracy at low speeds due to the weak motor back EMF; second, startup failure is prone to occur during the motor startup phase when static friction or high-inertia loads must be overcome.

[0003] In traditional voltage-to-frequency ratio open-loop control, insufficient starting torque is often addressed by a torque boost strategy, which increases the initial voltage to enhance the starting torque. However, if the rotor fails to accelerate synchronously due to load resistance, excessive slip will result, causing a surge in current and triggering overcurrent protection. In this case, successful motor startup can be directly determined by the current status.

[0004] In contrast, sensorless vector control uses a current closed-loop regulation system, with the excitation current fixed and the torque current generated by the speed closed-loop. If the actual rotor speed cannot be increased due to resistance, the system will reduce the output voltage to limit the current, further reducing the starting torque and creating a vicious cycle of starting failure. Furthermore, because speed estimation relies on back-EMF and motor models, the estimated value deviates significantly from the actual speed under high-slip conditions, making it impossible for the system to accurately sense the starting state, unable to trigger protection mechanisms, and lacking an adaptive adjustment strategy.

[0005] The above defects result in low success rate and poor reliability of existing vector control methods in heavy-load startup scenarios. There is an urgent need for a technical solution that can autonomously determine the startup status and dynamically adjust the control parameters. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an adaptive adjustment method for starting of an asynchronous motor with speed sensorless vector control, and to provide an adaptive adjustment strategy after starting failure.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for adaptively adjusting the startup of a speed sensorless vector control of an asynchronous motor comprises the following steps:

[0009] S1: Pre-excite the motor and set the pre-excitation parameters according to the motor's no-load excitation current;

[0010] S2: After the magnetic field is established, the motor is started, the frequency is increased in the low frequency range of 0Hz to the first frequency judgment point, and the actual speed feedback is set to the filtered value of the given speed;

[0011] S3: When the given frequency reaches or exceeds the first frequency judgment point, the first startup failure judgment is performed: if the difference between the modulus of the given frequency and the modulus of the modulation index exceeds the first judgment threshold, the startup is judged to have failed, the startup failure flag is set to 1, and the process proceeds to S6; otherwise, the startup failure flag is set to 0, and the process proceeds to S4;

[0012] S4: Enters normal vector control mode, the actual speed is fed back and calculated through the back-EMF phase-locked loop, and the speed continues to increase;

[0013] S5: When the given frequency reaches or exceeds the second frequency judgment point, a second startup failure judgment is performed: if the difference between the modulus of the given frequency and the modulus of the modulation index exceeds the second judgment threshold, the startup is judged to have failed, the startup failure flag is set to 1, and the process proceeds to S6; otherwise, the startup failure flag is set to 0, and the process proceeds to S7;

[0014] S6: Block pulse output, extend acceleration time and increase excitation current, return to S1 and restart;

[0015] S7: Determine that the startup is successful and continue to increase the speed according to the set frequency;

[0016] The modulation index is a calculated value of the voltage component of the current loop closed-loop output.

[0017] Furthermore, in S3 and S5, the first judgment threshold and the second judgment threshold are both the given frequency per unit value minus 0.03.

[0018] Furthermore, in S3, the frequency per unit value of the first frequency judgment point is 0.05 to 0.06; and in S5, the frequency per unit value of the second frequency judgment point is 0.1 to 0.11.

[0019] Furthermore, in S3 and S5, the startup failure judgment is realized by counter accumulation: when the difference between the given frequency and the modulation modulus exceeds the judgment threshold, the counter accumulates, and when the accumulated number of times exceeds the set number of times, the startup failure is determined.

[0020] Furthermore, the set number of times is 100 times.

[0021] Furthermore, in S6, the specific method of extending the acceleration time is: extending the current acceleration time to 1.5-2 times the original value.

[0022] Furthermore, in S6, the specific method of increasing the excitation current is: setting the excitation current to 1.2 times the no-load excitation current of the motor.

[0023] Furthermore, in S2, the upper frequency limit of the low frequency band is the lowest frequency value at which the phase-locked loop can stably estimate the rotational speed.

[0024] Furthermore, in S6, after the pulse output is blocked, the system enters a shutdown state and automatically restarts after a delay of 3 seconds.

[0025] Furthermore, the calculation formula of the modulation index modulus value is:

[0026]

[0027] Among them, U d is the d-axis voltage component of the current loop closed-loop output, U q It is the q-axis voltage component of the current loop closed-loop output.

[0028] The beneficial effects of the present invention are:

[0029] (1) By real-time monitoring of the dynamic relationship between the given frequency and the output voltage modulation, a two-stage startup failure judgment mechanism is established. This mechanism can accurately identify whether the motor has successfully started in the low-frequency and medium-speed ranges, solving the problem of misjudgment of the startup status caused by inaccurate speed estimation in traditional vector control. When startup failure is determined, the system automatically blocks the output and dynamically adjusts the acceleration time and excitation current parameters, significantly improving the starting torque for heavy loads or high static friction loads, and avoiding continuous startup failures caused by blind restarts.

[0030] (2) In the low-frequency band, a given speed filter value is used instead of the estimated speed as feedback. Combined with the pre-excitation strategy, a stable magnetic field is established. This effectively suppresses the speed estimation fluctuation caused by the weak back electromotive force under low-speed conditions, ensuring the stability of the current closed-loop control during the initial startup. By extending the low-frequency acceleration time, the risk of slip rate mutation is reduced, and the imbalance between the output voltage and load torque is avoided, thereby enhancing the system's adaptability to complex loads.

[0031] (3) The system has a self-healing function through the design of automatic restart and parameter adjustment after blocking the pulse. After a startup failure, the excitation current is dynamically increased to strengthen the magnetic field and the acceleration time is extended to match the load inertia. This forms a parameter iterative optimization mechanism that can adapt to different working conditions without manual intervention, greatly improving the robustness of the system.

[0032] (4) The proposed mechanism for associating the judgment threshold with the per-unit frequency value allows for flexible adjustment of the judgment interval based on different motor characteristics, avoiding over-reliance on specific motor models. The modulation index calculation is based on the standard voltage component of the current loop closed-loop output, making it seamlessly compatible with mainstream vector control architectures and easy to integrate into existing inverter systems, reducing modification costs.

[0033] (5) By timely blocking the pulse and adjusting the output when the startup fails, the risk of current loss of control caused by continuous high slip is effectively suppressed, which not only protects the motor and drive equipment from damage, but also reduces the energy waste caused by fault shutdown, thereby improving the overall energy efficiency and safety of the system.

[0034] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0036] Figure 1 It is a judgment flow chart of the present invention;

[0037] Figure 2 This is the vector control block diagram used in the present invention. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0040] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] like Figure 1 The following is a flow chart showing the determination process of the present invention. Given the motor's no-load excitation current, the motor is pre-excited. Since the motor has not yet been officially started, the magnetic field established at this point is a constant, unchanging field. The pre-excitation time is set to 3-5 seconds; of course, this time is not fixed; the goal is to establish a stable magnetic field. Once the magnetic field stabilizes, the motor can be started, meaning that the magnetic field begins to rotate.

[0042] During normal startup, the motor runs in closed loop mode. Figure 2 As shown in the figure, due to the lack of a speed sensor, the speed estimation is inaccurate in the low-speed range of 0-2.5Hz. Therefore, the actual speed feedback is given by the filtered value of the set speed wrset. Although the operating mode at this time is closed-loop, it is similar to the VF control of the speed closed loop. The speed set is the external input speed set signal wrset, and the speed feedback is directly given by the filtered value of wrset. Because the speed is relatively low at this time and the time spent in the low-speed range is relatively short, it is assumed that the rotor flux is basically coincident. When the d-axis coincides with the rotor flux axis, its back EMF is generated.

[0043] When the speed reaches 2.5Hz, the per-unit value is 0.05. At this point, the phase-locked loop (PLL) has accurately locked the motor's back EMF, and the system speed can also be determined by the PLL. At this point, the speed is determined by the filtered value of the previously set speed, wrset, switching to the sum of the filtered value of wrset and the slip obtained by the EMF control loop.

[0044] When the speed reaches 0.05 of the per-unit value, that is, 2.5 Hz, judgment condition 1 is performed.

[0045] Judgment condition 1: When the speed is 0.05 ≤ f ≤ 0.06, if the output modulation index modulate is less than the frequency f - 0.03 (that is, the per-unit value of the modulation index is 0.03 less than the per-unit value of the frequency), then the start failure counter countnum1 is incremented. The frequency here is the set frequency output by the system's given speed through the ramp function, not the frequency obtained by the EMF phase-locked loop. Because the frequency obtained by the phase-locked loop contains harmonics, it is inaccurate when used as a comparison value.

[0046] When the counter countnum1 is greater than 100, the startup is judged to have failed. The error introduced by the modulation index fluctuation is eliminated by judging the accumulated value.

[0047] If judgment condition 1 is not met, regardless of the reason, such as the modulation index fluctuates at low speed, resulting in a false judgment, or the modulation index modulate and frequency f change simultaneously and the difference between the two is indeed small, then the startup is judged to be successful and the startup failure flag is set to 0. If judgment condition 1 is met, the startup failure flag is set to 1.

[0048] If the start failure flag is 1, the startup is considered a failure. The system blocks pulses, clears running variables, and enters the shutdown state. The system's acceleration time is then extended to 1.5 or 2 times the previous value. This multiple is variable and not fixed. By adjusting the acceleration time, the acceleration process during the startup phase is prolonged to prevent excessive motor slip. The excitation current setting is also adjusted to 1.2 times the no-load excitation current to provide greater torque. Using greater torque and slower acceleration to drive the motor resolves the startup failure.

[0049] After a delay of 3 seconds, the system automatically restarts.

[0050] If the startup failure flag is 0, the startup is considered successful. The accuracy of the initial startup success determination is low, so a second determination is required at high speed. The system continues to increase its speed.

[0051] When the speed reaches 0.1 of the per-unit value, that is, 5.0 Hz, judgment condition 2 is performed.

[0052] Criteria for judgment condition 2: When the speed is 0.1≤f≤0.11, if the output modulation index modulate is less than f-0.03, that is, the per-unit value of the modulation index is 0.03 less than the per-unit value of the frequency, then the start failure counter countnum2 is set to accumulate.

[0053] When the counter countnum2>100, it is determined that the startup has failed.

[0054] If the judgment condition 2 is not met, the startup is judged to have failed, and the startup failure flag is set to 0. If the judgment condition 2 is met, the startup failure flag is set to 1.

[0055] If the startup failure flag is 1, the startup is considered a failure. The system blocks pulses, clears running variables, and enters the shutdown state. Adjust system parameters, extend the system acceleration time to 1.5 or 2 times the previous value, and increase the excitation current reference to 1.2 times the no-load excitation current. Automatic restart occurs after a 3-second delay.

[0056] If the startup failure flag is 0, the startup is considered successful. Here, two judgments have been made. If the startup failure flag is 0 twice, it can be considered that the startup is successful.

[0057] Example 1: Two-stage adaptive starting under high static friction load

[0058] 1.1 Scenario and parameter configuration

[0059] Load type: The initial static friction torque of the conveyor belt is 180% of the rated torque.

[0060] Pre-excitation setting: no-load excitation current 4A, lasting 5 seconds to ensure magnetic field saturation.

[0061] Frequency judgment points: the first judgment point is 2.5Hz (unit value 0.05), the second judgment point is 5Hz (unit value 0.1).

[0062] Threshold rule: A failure is triggered when the modulation index modulus is lower than the given frequency per unit value of 0.03.

[0063] 1.2 Workflow

[0064] Pre-excitation stage: 4A DC excitation is applied when the motor is stationary. The flux observer monitors the d-axis flux and enters the starting stage after reaching the steady-state value of 0.95Wb.

[0065] Low-frequency frequency increase stage: the frequency is increased to 2.5Hz at a ramp rate of 0.3Hz / s. During this period, the speed feedback adopts the value after the given frequency is filtered by a first-order low-pass filter (cut-off frequency 0.5Hz), and the voltage loop output is dynamically limited to 30% of the rated voltage.

[0066] First judgment point processing:

[0067] When it reaches 2.5Hz, the difference between the modulation index value (such as 0.32pu) and the given frequency per unit value (0.05pu) is calculated in real time.

[0068] If the difference value exceeds the threshold value of 0.03pu continuously for 100 control cycles (10ms / cycle), the startup is determined to have failed.

[0069] Parameter adjustment and restart:

[0070] Block PWM output, clear integrator status, extend acceleration time from 20 seconds to 40 seconds, and increase excitation current to 4.8A.

[0071] After a delay of 3 seconds, pre-excitation was resumed, and the voltage loop output limit was relaxed to 45% during the second startup, successfully overcoming static friction.

[0072] 1.3 Technical Effect

[0073] The system avoids speed estimation fluctuations through low-frequency filtering feedback, eliminates instantaneous interference through threshold accumulation judgment, and accurately identifies stalls caused by static friction.

[0074] Dynamically extend the acceleration time to reduce slip, increase voltage margin, and ensure a smooth increase in torque after restart.

[0075] Example 2: Secondary stability judgment at high speed for large inertia load

[0076] 2.1 Scenario and Parameter Configuration

[0077] Load type: Flywheel inertia is 8 times that of the motor rotor inertia.

[0078] Pre-excitation setting: no-load excitation current 5A, lasting 4 seconds.

[0079] Frequency judgment points: the first judgment point is 3Hz (unit value 0.06), the second judgment point is 8Hz (unit value 0.16).

[0080] 2.2 Workflow

[0081] Initial startup phase:

[0082] After pre-excitation, the frequency is increased to 3Hz at 0.4Hz / s. The difference between the modulation index value of 0.05pu and the frequency per unit value of 0.06pu does not exceed the threshold, and the startup is determined to be successful.

[0083] Switch to normal vector control mode, the speed feedback is switched to the estimated value of the phase-locked loop output, and the voltage loop releases the output limit.

[0084] Secondary monitoring of high-speed sections:

[0085] When the frequency is increased to 8 Hz, the load inertia causes insufficient acceleration, and the difference between the modulation modulus value of 0.12 pu and the per-unit frequency value of 0.16 pu exceeds the threshold of 0.03 pu.

[0086] If the start failure counter exceeds the limit 80 times within 50 cycles, the high-speed section is determined to be unstable.

[0087] Dynamic parameter optimization:

[0088] The output is blocked, the acceleration time is extended from 25 seconds to 50 seconds, the excitation current is increased to 6A, and after restarting, the voltage loop adopts a variable slope frequency increase (0.2Hz / s in the 0-3Hz stage, 0.4Hz / s above 3Hz).

[0089] After the second start, the modulation modulus value increases synchronously with the frequency, and the difference is stable within the threshold. The system successfully drives the flywheel to accelerate to the target speed.

[0090] 2.3 Technical Effects

[0091] Through the secondary stability judgment mechanism in high-speed sections, the problem of insufficient acceleration caused by inertia is identified, avoiding the traditional method of misjudging success in high-speed sections.

[0092] The variable slope frequency boost strategy takes into account both low-speed torque and high-speed response, and adapts to the nonlinear characteristics of large inertia loads.

[0093] Example 3: Multi-condition iterative parameter self-healing verification

[0094] 3.1 Scenario and parameter configuration

[0095] Load combination: initial jamming of the crusher (static friction) superimposed with periodic impact loads.

[0096] Initial parameters: acceleration time 15 seconds, excitation current 3.5A, maximum failure times 3 times.

[0097] 3.2 Workflow

[0098] First startup failure:

[0099] After pre-excitation, the frequency is increased to 2.5Hz, and the modulation index difference continues to exceed the limit, resulting in failure.

[0100] Parameter adjustment: acceleration time increased to 22.5 seconds, excitation current 4.2A.

[0101] The second boot was partially successful:

[0102] After restarting, static friction was broken, but at 5Hz, the modulation index fluctuated due to load impact, and the difference exceeded the limit 20 times before being judged as failure.

[0103] Secondary parameter adjustment: acceleration time increased to 33.75 seconds, excitation current 5.04A, and voltage feedforward compensation for impact load was added.

[0104] The third startup is successful:

[0105] Feedforward compensation offsets load shocks, the modulation index difference is always below the threshold, and the system runs stably to the target frequency.

[0106] 3.3 Technical Effects

[0107] During iterative adjustment, the parameters are increased by a factor of 1.5, and feedforward compensation is combined to enhance interference immunity, demonstrating the system's progressive optimization capability in multi-fault scenarios.

[0108] The failure limit mechanism prevents infinite loops and ensures safety and practicality.

[0109] Example 4: Multi-motor compatibility verification

[0110] 4.1 Test Objects

[0111] Motor A: 5.5kW, rated current 12A, no-load excitation current 2.8A.

[0112] Motor B: 22kW, rated current 42A, no-load excitation current 8.5A.

[0113] 4.2 Unified parameter configuration

[0114] Judgment threshold: frequency per unit value -0.03.

[0115] Per-unit reference value: Motor A is based on 50 Hz, and Motor B is based on 60 Hz.

[0116] 4.3 Adaptive Process

[0117] Motor A test:

[0118] The first judgment point is 2.5Hz (unit value 0.05), and the modulation modulus is detected to be 0.02pu. After the difference exceeds the limit, the acceleration time is adjusted to 30 seconds, the excitation current is increased to 3.36A, and the startup is successful.

[0119] Motor B test:

[0120] The first judgment point is 3Hz (unit value 0.05), the modulation modulus is 0.04pu, and after the difference exceeds the limit, the parameters are adjusted in the same proportion (acceleration time 45 seconds → 67.5 seconds, excitation current 10.2A), and the startup is successful.

[0121] 4.4 Technical Effects

[0122] The per-unit judgment mechanism enables motors of different powers to share the same threshold logic without the need to re-adjust parameters.

[0123] The proportional adjustment strategy adapts to the differences in motor parameters and verifies the versatility and scalability of the solution.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for adaptive adjustment of asynchronous motor speed sensorless vector control startup, characterized by: The following steps are involved: S1: Pre-excite the motor and set the pre-excitation parameters according to the motor's no-load excitation current; S2: After the magnetic field is established, the motor is started, the frequency is increased in the low frequency range of 0Hz to the first frequency judgment point, and the actual speed feedback is set to the filtered value of the given speed; S3: When the given frequency reaches or exceeds the first frequency judgment point, the first startup failure judgment is performed: if the difference between the modulus value of the given frequency and the modulus value of the modulation index exceeds the first judgment threshold, the startup is judged to have failed, the startup failure flag is set to 1, and the process proceeds to S6; Otherwise, the startup failure flag is set to 0 and the process goes to S4; S4: Enters normal vector control mode, the actual speed is fed back and calculated by the back-EMF phase-locked loop, and the speed continues to increase; S5: When the given frequency reaches or exceeds the second frequency judgment point, a second startup failure judgment is performed: if the difference between the modulus of the given frequency and the modulus of the modulation index exceeds the second judgment threshold, the startup is judged to have failed, the startup failure flag is set to 1, and the process proceeds to S6; Otherwise, the startup failure flag is set to 0 and the process goes to S7; S6: Block pulse output, extend acceleration time and increase excitation current, return to S1 and restart; S7: Determine that the startup is successful and continue to increase the speed according to the set frequency; The modulation index is a calculated value of the voltage component of the current loop closed-loop output.

2. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: In S3 and S5, the first judgment threshold and the second judgment threshold are both the given frequency per unit value minus 0.

03.

3. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: In S3, the frequency per unit value of the first frequency determination point is 0.05 to 0.06; in S5, the frequency per unit value of the second frequency determination point is 0.1 to 0.

11.

4. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: In S3 and S5, the startup failure judgment is realized by counter accumulation: when the difference between the given frequency and the modulation modulus exceeds the judgment threshold, the counter accumulates, and when the accumulated number of times exceeds the set number, it is determined that the startup has failed.

5. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 4, characterized in that: The set number of times is 100 times.

6. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: In S6, the specific method of extending the acceleration time is: extending the current acceleration time to 1.5-2 times of the original value.

7. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: In the above-mentioned S6, the specific method of increasing the excitation current is: setting the excitation current to 1.2 times the no-load excitation current of the motor.

8. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: In S2, the upper frequency limit of the low frequency band is the lowest frequency value at which the phase-locked loop can stably estimate the rotational speed.

9. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: In S6, after the pulse output is blocked, the system enters a shutdown state and automatically restarts after a delay of 3 seconds.

10. The method for adaptive adjustment of asynchronous motor speed sensorless vector control startup according to claim 1, characterized in that: The calculation formula of the modulation index modulus value is: Among them, U d is the d-axis voltage component of the current loop closed-loop output, U q It is the q-axis voltage component of the current loop closed-loop output.

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