Non-inductive FOC starting method and system for heavy-load industrial fan

Abstract

The invention discloses a non-inductive FOC starting method and system for a heavy-load industrial fan, and belongs to the technical field of motor control, and the method comprises the steps: carrying out the power-on initialization of a brushless motor of the heavy-load industrial fan, and completing the power supply and driving signal preparation; meanwhile, setting a plurality of frequency control variables for controlling the starting process, including open-loop final frequency, V / F frequency acceleration, given operation frequency, current closed-loop frequency and current closed-loop given current; thirdly, adopting a V / F starting mode, presetting relevant parameters, maintaining the constant ratio of voltage to frequency, driving the motor to accelerate to a current closed-loop frequency in an open-loop mode, then switching to a current closed-loop control mode, adjusting current through PI, generating an incremental angle based on the final frequency of V / F starting, and continuously dragging the motor to accelerate to the final open-loop frequency; and finally, when the motor reaches the final open-loop frequency, the closed-loop control of the non-inductive position observer is switched to, so that the heavy-load industrial fan stably runs.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a sensorless FOC starting method and system for a heavy-load industrial fan. Background Art

[0002] In many fields such as industrial manufacturing, high-end technology, home appliances, and transportation, motors are widely used, bringing great convenience to the development of various industries. At present, motors are developing from traditional brushed motors to brushless motors, and the driving algorithms of brushless motors are also constantly evolving. Among them, FOC sine wave drive has become the mainstream due to its good performance.

[0003] In the FOC control mode, it is crucial to accurately obtain the angle position of the motor rotor. However, the solution without position sensor is widely adopted due to factors such as cost and working environment. This makes it difficult to obtain rotor position information, greatly increasing the difficulty and failure risk of motor starting. Especially in the application scenario of industrial heavy-duty fans, the load is heavy and the moment of inertia is large. The back electromotive force is insufficient when the motor is stationary or at low speed, and the rotor angle cannot be accurately calculated, resulting in frequent problems such as start-up failure and abnormality, which seriously affects the product reputation and corporate reputation. In order to improve the starting performance, the industry chooses two methods to start: high-frequency injection to directly obtain the rotor position or pre-positioning plus open-loop forced drag. However, the former has limitations on the motor and requires the motor to have salient polarity. At the same time, there will be obvious noise, which is difficult for many customers to accept. In heavy-duty and large-inertia applications, pre-positioning plus open-loop forced drag takes a long time to locate, consumes a lot of current, and is prone to jitter after positioning, which greatly increases the starting time and the probability of failure. Therefore, improving the starting reliability and success rate of heavy-duty fans has become a key issue that the industry needs to solve urgently. Summary of the invention

[0004] The object of the present invention is to provide a sensorless FOC starting method and system for a heavy-load industrial fan to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a sensorless FOC starting method for a heavy-load industrial fan, the method comprising:

[0006] Step S100: power on and initialize the brushless motor of the heavy-duty industrial fan to complete power supply and drive signal preparation; at the same time, set multiple frequency control variables for controlling the startup process, including open-loop final frequency, V / F frequency acceleration, given operating frequency, current closed-loop frequency, and current closed-loop given current;

[0007] Step S200: adopting the V / F starting mode, maintaining a constant ratio of voltage to frequency through preset direct-axis voltage, quadrature-axis voltage and self-increase angle, and driving the motor to accelerate from a stationary state to a current closed-loop frequency in an open-loop control mode;

[0008] Step S300: After the operating frequency of the motor reaches the current closed-loop frequency, switch to the current closed-loop control mode, adjust the direct-axis current and quadrature-axis current through PI regulation, and generate an increasing angle based on the final frequency of V / F startup, and continue to drive the motor to accelerate to the open-loop final frequency in an open-loop angle mode;

[0009] Step S400: When the operating frequency of the motor reaches the open-loop final frequency, switch to the closed-loop control regulated by the sensorless position observer for feedback, and the heavy-duty industrial fan enters the stable operating state.

[0010] Furthermore, the open-loop final frequency represents the frequency threshold for switching from current closed-loop driving to closed-loop control regulated by the sensorless position observer for feedback; the V / F frequency acceleration is used to control the acceleration / deceleration frequency in the V / F startup stage; the given operating frequency represents the target frequency for the motor to reach stable operation; the current closed-loop frequency represents the frequency threshold for switching from the V / F startup stage to the current closed-loop driving stage; the current closed-loop given current represents the target values of the direct-axis current and quadrature-axis current in the current closed-loop stage.

[0011] Furthermore, the step S200 includes:

[0012] Step S201: Preset the direct-axis voltage Ud, quadrature-axis voltage Uq, and self-increasing angle θ; during the motor startup process, monitor the values of voltage and frequency in real time. When it is detected that the frequency changes, according to the adjustment mechanism of U = k vf ×f, synchronously adjust the voltage to keep the ratio of voltage to frequency constant during startup, where U represents the voltage value detected in real time, f represents the frequency value detected in real time, and k vf is the preset V / F ratio coefficient;

[0013] Step S202: After completing the constant control of the voltage-to-frequency ratio in step S201, drive the motor in an open-loop control mode; according to the parameters preset in step S201, generate corresponding control signals through inverse Park transformation and SVPWM, and apply them to the stator windings of the motor to generate a rotating magnetic field to drive the motor to accelerate from the stationary state; during the acceleration process, the rotational speed of the motor gradually increases, and the self-increasing angle continuously increases according to the preset linear increasing law; at the same time, monitor the operating frequency of the motor in real time. When it is monitored that the operating frequency of the motor reaches the current closed-loop frequency set in step S100, it indicates that the acceleration process of the V / F startup stage of the motor is completed.

[0014] Furthermore, the step S300 includes:

[0015] Step S301: When it is monitored that the operating frequency of the motor reaches the current closed-loop frequency set in Step S100, trigger the control mode switching mechanism, and switch the control mode from the open-loop control mode in the V / F startup stage to the current closed-loop control mode; after completing the mode switching, collect the direct-axis current and quadrature-axis current of the motor in real time, and determine the target value of the direct-axis current and the target value of the quadrature-axis current according to the current closed-loop given current preset in Step S100; compare the collected actual direct-axis current with the target direct-axis current to calculate the direct-axis current error; compare the collected actual quadrature-axis current with the target quadrature-axis current to calculate the quadrature-axis current error; input the calculated direct-axis current error and quadrature-axis current error into the corresponding PI regulators respectively to adjust the direct-axis and quadrature-axis voltages to the preset target values;

[0016] Step S302: Based on the final frequency of V / F startup, calculate the initial incremental angle of angle open-loop according to the formula: Δθ0 = f cl ×T×360°; where Δθ0 represents the initial incremental angle of angle open-loop, f cl is the current closed-loop frequency, and T is the angle incremental period; set the angle incremental period to be equal to the execution period of the current loop; in each angle incremental period, multiply Δθ0 by the angle incremental coefficient m to obtain the actual incremental angle Δθ = Δθ0×m, where m ∈ (1, 2); in the angle open-loop mode, combine the direct-axis and quadrature-axis voltages output by the PI regulators, and generate control signals through inverse Park transformation and SVPWM, and apply them to the stator windings of the motor to drive the motor to continuously accelerate; during the acceleration process, monitor the operating frequency of the motor in real time. When it is monitored that the operating frequency of the motor reaches the open-loop final frequency set in Step S100, switch to the closed-loop control regulated by the sensorless position observer, and the heavy-duty industrial fan enters the stable operating state.

[0017] A sensorless FOC startup system for a heavy-duty industrial fan, the system includes: an initialization module, a V / F startup module, a current closed-loop angle open-loop driving module, and a closed-loop control module;

[0018] The initialization module powers on and initializes the brushless motor of the heavy-duty industrial fan to complete the power supply and drive signal preparation; at the same time, set multiple frequency control variables to control the startup process;

[0019] The V / F startup module adopts the V / F startup method, maintains the ratio of voltage to frequency constant through the preset direct-axis voltage, quadrature-axis voltage, and self-increasing angle, and drives the motor to accelerate from the stationary state to the current closed-loop frequency in an open-loop control manner;

[0020] After the motor operating frequency reaches the current closed-loop frequency, the current closed-loop angle open-loop driving module switches to the current closed-loop control mode, adjusts the direct-axis current and quadrature-axis current through PI regulation, and generates an increasing angle based on the final frequency of V / F starting, and continues to drive the motor to accelerate to the open-loop final frequency in an angle open-loop manner;

[0021] When the motor operating frequency reaches the open-loop final frequency, the closed-loop control module switches to the closed-loop control with the feedback regulated by the sensorless position observer, and the heavy-duty industrial fan enters the stable operating state.

[0022] The multiple frequency control variables set by the initialization module include the open-loop final frequency, V / F frequency acceleration, given operating frequency, current closed-loop frequency, and current closed-loop given current;

[0023] The open-loop final frequency represents the frequency threshold for switching from the current closed-loop driving to the closed-loop control with the feedback regulated by the sensorless position observer; the V / F frequency acceleration is used to control the acceleration / deceleration frequency in the V / F starting stage; the given operating frequency represents the target frequency for the motor to reach stable operation; the current closed-loop frequency serves as the frequency threshold for switching from the V / F starting stage to the current closed-loop driving stage; the current closed-loop given current represents the target values of the direct-axis current and quadrature-axis current in the current closed-loop stage.

[0024] The V / F starting module includes a V / F control unit and a real-time monitoring unit; the V / F control unit is used to preset the direct-axis voltage, quadrature-axis voltage, and self-increasing angle, and maintain the constant ratio of voltage to frequency according to the adjustment mechanism during the starting process to stabilize the motor magnetic flux; the real-time monitoring unit generates the control signal for driving the motor through inverse Park transformation and SVPWM, and real-time monitors the motor operating frequency, and triggers the switching to the current closed-loop control mode when the current closed-loop frequency is reached.

[0025] The current closed-loop angle open-loop driving module includes a current regulation unit and an angle open-loop acceleration unit; when the motor frequency reaches the current closed-loop frequency, the current regulation unit switches to the current closed-loop control mode, collects the direct-axis and quadrature-axis currents, and adjusts them through a PI regulator to make the current reach the target value; the angle open-loop acceleration unit calculates the initial increasing angle of the angle open-loop based on the final frequency of V / F starting, multiplies it by the angle increasing coefficient every period to obtain the actual increasing angle, combines the voltage output by the PI regulator, generates the control signal through inverse Park transformation and SVPWM, drives the motor to continuously accelerate, and monitors the motor frequency, and triggers the next mode switching when the open-loop final frequency is reached.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0027] The present invention adopts the technology of combining V / F startup with current closed-loop and angle open-loop drive, enabling the motor startup process to proceed orderly in stages. During V / F startup, the ratio of voltage to frequency is maintained constant to achieve low-current and smooth startup, reducing startup impact. During the current closed-loop and angle open-loop drive stage, the current and angle are precisely adjusted to ensure stable acceleration of the motor. Compared with the single startup method in the prior art, it solves the problems of difficult startup and easy failure of heavy-duty industrial fans, greatly improving the startup success rate and stability.

[0028] The present invention preset parameters and PI regulate the direct-axis current and quadrature-axis current, and can adjust the current in real time according to the operating state of the motor. During startup, it avoids the heating problem of the motor caused by excessive current or unstable magnetic flux. Compared with the traditional startup method, it reduces the copper loss caused by insufficient adjustment of the low-frequency startup voltage and the motor increasing the current to maintain the load, as well as the core eddy current loss and stray loss caused by the non-sinusoidal wave output of the frequency converter, effectively reducing the heating of the motor and the control board.

[0029] The present invention can flexibly adjust startup parameters according to the characteristics and application scenarios of different motors by setting multiple modifiable variables such as open-loop final frequency and V / F frequency acceleration. Different from the method of fixed startup parameters in the prior art, this method solves the problem that the startup method is difficult to adapt to a variety of motors, making this startup method widely applicable to various types of motors and enhancing the versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0031] Figure 1 is a method flow chart of a sensorless FOC startup method for heavy-duty industrial fans;

[0032] Figure 2 is a system flow chart of a sensorless FOC startup system for heavy-duty industrial fans. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Please refer to Figure 1 - Figure 2 , the present invention provides a technical solution: a sensorless FOC startup method for heavy-duty industrial fans, the method comprising:

[0035] Step S100: Power on and initialize the brushless motor of the heavy-duty industrial fan to complete the power supply and drive signal preparation; meanwhile, set multiple frequency control variables to control the startup process, including the open-loop final frequency, V / F frequency acceleration, given operating frequency, current closed-loop frequency, and current closed-loop given current;

[0036] Step S200: Adopt the V / F startup method. By presetting the direct-axis voltage, quadrature-axis voltage, and self-increasing angle, maintain the constant ratio of voltage to frequency, and drive the motor to accelerate from the stationary state to the current closed-loop frequency in an open-loop control manner;

[0037] Step S300: After the motor operating frequency reaches the current closed-loop frequency, switch to the current closed-loop control mode. Adjust the direct-axis current and quadrature-axis current through PI, and generate an increasing angle based on the final frequency of V / F startup, and continue to drive the motor to accelerate to the open-loop final frequency in an angle open-loop manner;

[0038] Step S400: When the motor operating frequency reaches the open-loop final frequency, switch to the closed-loop control regulated by the sensorless position observer, and the heavy-duty industrial fan enters the stable operating state.

[0039] Furthermore, the open-loop final frequency represents the frequency threshold for switching from the current closed-loop drive to the closed-loop control regulated by the sensorless position observer; the V / F frequency acceleration is used to control the acceleration / deceleration frequency in the V / F startup stage; the given operating frequency represents the target frequency for the motor to reach stable operation; the current closed-loop frequency represents the frequency threshold for switching from the V / F startup stage to the current closed-loop drive stage; the current closed-loop given current represents the target values of the direct-axis current and quadrature-axis current in the current closed-loop stage.

[0040] Furthermore, the step S200 includes:

[0041] Step S201: Preset the direct-axis voltage Ud, quadrature-axis voltage Uq, and self-increasing angle θ; during the motor startup process, real-time monitor the values of voltage and frequency. When it is detected that the frequency changes, adjust the voltage synchronously according to the adjustment mechanism of U = k vf ×f, so that the ratio of voltage to frequency remains constant during startup, where U represents the real-time detected voltage value, f represents the real-time detected frequency value, and k vf is the preset V / F ratio coefficient;

[0042] Step S202: After completing the constant control of the voltage-frequency ratio in step S201, drive the motor in an open-loop control mode; according to the preset parameters in step S201, generate corresponding control signals through inverse Park transformation and SVPWM, apply them to the stator windings of the motor to generate a rotating magnetic field, and drive the motor to accelerate from a stationary state; during the acceleration process, the speed of the motor gradually increases, and the self-increasing angle continuously increases according to the preset linear increasing law; at the same time, monitor the operating frequency of the motor in real time. When it is detected that the operating frequency of the motor reaches the current closed-loop frequency set in step S100, it indicates that the acceleration process of the V / F startup stage of the motor is completed.

[0043] Further, the step S300 includes:

[0044] Step S301: When it is detected that the operating frequency of the motor reaches the current closed-loop frequency set in step S100, trigger the control mode switching mechanism to switch the control mode from the open-loop control mode in the V / F startup stage to the current closed-loop control mode; after completing the mode switching, collect the direct-axis current and quadrature-axis current of the motor in real time, and determine the target value of the direct-axis current and the target value of the quadrature-axis current according to the current closed-loop given current preset in step S100; compare the collected actual direct-axis current with the target direct-axis current to calculate the direct-axis current error; compare the collected actual quadrature-axis current with the target quadrature-axis current to calculate the quadrature-axis current error; input the calculated direct-axis current error and quadrature-axis current error into the corresponding PI regulators respectively to adjust the direct-axis and quadrature-axis voltages to the preset target values;

[0045] Step S302: Based on the final frequency of the V / F startup, calculate the initial increasing angle of the angle open loop according to the formula: Δθ0 = f cl ×T×360°; where Δθ0 represents the initial increasing angle of the angle open loop, f cl is the current closed-loop frequency, and T is the angle increasing period; set the angle increasing period to be equal to the execution period of the current loop; in each angle increasing period, multiply Δθ0 by the angle increasing coefficient m to obtain the actual increasing angle Δθ = Δθ0×m, where m ∈ (1, 2); in the angle open-loop mode, combine the direct-axis and quadrature-axis voltages output by the PI regulators, generate control signals through inverse Park transformation and SVPWM, apply them to the stator windings of the motor, and drive the motor to continue accelerating; during the acceleration process, monitor the operating frequency of the motor in real time. When it is detected that the operating frequency of the motor reaches the open-loop final frequency set in step S100, switch to the closed-loop control regulated by the sensorless position observer, and the heavy-duty industrial fan enters the stable operation state.

[0046] Sensorless FOC starting system for overloaded industrial fans, the system comprising: an initialization module, a V / F starting module, a current closed-loop angle open-loop driving module, and a closed-loop control module;

[0047] The initialization module powers on and initializes the brushless motor of the overloaded industrial fan to complete power supply and drive signal preparation; meanwhile, a plurality of frequency control variables are set to control the starting process;

[0048] The V / F starting module adopts the V / F starting method, and maintains a constant ratio of voltage to frequency through preset direct-axis voltage, quadrature-axis voltage, and self-increasing angle, and drives the motor to accelerate from a stationary state to the current closed-loop frequency in an open-loop control manner;

[0049] After the motor running frequency reaches the current closed-loop frequency, the current closed-loop angle open-loop driving module switches to the current closed-loop control mode, adjusts the direct-axis current and quadrature-axis current through PI, and generates an increasing angle based on the final frequency of V / F starting, and continues to drive the motor to accelerate to the open-loop final frequency in an angle open-loop manner;

[0050] When the motor running frequency reaches the open-loop final frequency, the closed-loop control module switches to the closed-loop control regulated by the sensorless position observer, and the overloaded industrial fan enters a stable operation state.

[0051] The plurality of frequency control variables set by the initialization module include the open-loop final frequency, V / F frequency acceleration, given operating frequency, current closed-loop frequency, and current closed-loop given current; the open-loop final frequency represents the frequency threshold for switching from current closed-loop driving to closed-loop control regulated by the sensorless position observer; the V / F frequency acceleration is used to control the acceleration / deceleration frequency in the V / F starting stage; the given operating frequency represents the target frequency for the motor to reach stable operation; the current closed-loop frequency serves as the frequency threshold for switching from the V / F starting stage to the current closed-loop driving stage; the current closed-loop given current represents the target values of the direct-axis current and quadrature-axis current in the current closed-loop stage.

[0052] The V / F starting module includes a V / F control unit and a real-time monitoring unit; the V / F control unit is used to preset the direct-axis voltage, quadrature-axis voltage, and self-increasing angle, and maintain a constant ratio of voltage to frequency according to the adjustment mechanism during the starting process to make the motor magnetic flux stable; the real-time monitoring unit generates a control signal for driving the motor through inverse Park transformation and SVPWM, and real-time monitors the motor running frequency, and triggers the switching to the current closed-loop control mode when the current closed-loop frequency is reached.

[0053] The current closed-loop and angle open-loop driving module includes a current regulation unit and an angle open-loop acceleration unit; when the motor frequency reaches the current closed-loop frequency, the current regulation unit switches to the current closed-loop control mode, collects the direct-axis and quadrature-axis currents, and after being regulated by a PI regulator, the current reaches the target value; based on the final frequency of V / F starting, the angle open-loop acceleration unit calculates the initial increment angle of the angle open-loop, multiplies it by the angle increment coefficient every period to obtain the actual increment angle, combines the voltage output by the PI regulator, generates a control signal through inverse Park transformation and SVPWM, drives the motor to continuously accelerate, and monitors the motor frequency. When the open-loop final frequency is reached, the next mode switch is triggered.

[0054] Embodiment of the present invention:

[0055] Power on and initialize the brushless motor of the heavy-duty industrial fan to complete the preparation of power supply and drive signals; set multiple frequency control variables: open-loop final frequency = 8Hz; V / F frequency acceleration = 1.5Hz / s; given operating frequency = 50Hz; current closed-loop frequency = 4Hz; current closed-loop given current = 3.5A;

[0056] In the V / F starting stage, based on the V / F starting principle, by maintaining the constant ratio of voltage to frequency, the motor magnetic flux is ensured to be stable, and the motor starts smoothly from zero speed. The motor accelerates to the current closed-loop frequency of 4Hz at an acceleration of 1.5Hz / s.

[0057] After the motor reaches the current closed-loop frequency of 4Hz, it enters the current closed-loop driving stage. In this stage, current closed-loop control is adopted, and the direct-axis current and quadrature-axis current are regulated by PI to control the motor torque, making the current waveform have a high sinusoidality, and at the same time, dragging is carried out according to the current closed-loop given current of 3.5A.

[0058] The initial increment angle of the angle open-loop Δθ0 = current closed-loop frequency 4Hz × angle increment period (equal to the execution period of the current loop) 0.0001s × angle of one revolution 360° = 0.144°; based on the actual motor debugging, the angle increment coefficient is selected as 1.2; every 0.0001s, in each current loop execution period, the angle is incremented according to the actual increment angle Δθ = Δθ0 × 1.2 to achieve the purpose of further acceleration.

[0059] The motor continues to accelerate until it reaches the open-loop final frequency of 8Hz, and then enters the closed-loop operation stage. In the closed-loop operation stage, the position and speed information of the motor rotor is fed back through a sensorless position observer, and the control parameters are adjusted in real time according to the feedback, so that the motor operates stably at the given operating frequency of 50Hz to meet the working requirements of the heavy-duty industrial fan.

[0060] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Sensorless FOC starting method for overloaded industrial fans, characterized in that: The method includes: Step S100: Power on and initialize the brushless motor of the heavy-duty industrial fan to complete power supply and drive signal preparation; meanwhile, set multiple frequency control variables for controlling the startup process, including open-loop final frequency, V / F frequency acceleration, given operating frequency, current closed-loop frequency, and current closed-loop given current; Step S200: Adopt the V / F startup method, maintain the constant ratio of voltage to frequency through the preset direct-axis voltage, quadrature-axis voltage, and self-increasing angle, and drive the motor from the stationary state to the current closed-loop frequency in an open-loop control manner; Step S300: After the motor operating frequency reaches the current closed-loop frequency, switch to the current closed-loop control mode, adjust the direct-axis current and quadrature-axis current through PI, and generate an increasing angle based on the final frequency of V / F startup, and continue to drive the motor to accelerate to the open-loop final frequency in an angle open-loop manner; Step S400: When the motor operating frequency reaches the open-loop final frequency, switch to the closed-loop control regulated by the sensorless position observer, and the heavy-duty industrial fan enters the stable operating state.

2. The sensorless FOC starting method for heavy-duty industrial fans according to claim 1, wherein: The open-loop final frequency represents the frequency threshold for switching from current closed-loop drive to closed-loop control regulated by the sensorless position observer; the V / F frequency acceleration is used to control the acceleration / deceleration frequency in the V / F startup stage; the given operating frequency represents the target frequency for the motor to reach stable operation; the current closed-loop frequency represents the frequency threshold for switching from the V / F startup stage to the current closed-loop drive stage; the current closed-loop given current represents the target values of the direct-axis current and quadrature-axis current in the current closed-loop stage.

3. The sensorless FOC starting method for heavy-duty industrial fans according to claim 1, wherein: The step S200 includes: Step S201: Preset the direct-axis voltage Ud, quadrature-axis voltage Uq, and self-increasing angle θ; during the motor startup process, monitor the values of voltage and frequency in real time. When a change in frequency is detected, adjust the voltage synchronously according to the adjustment mechanism of U = k vf ×f, so that the ratio of voltage to frequency remains constant during startup, where U represents the voltage value detected in real time, f represents the frequency value detected in real time, and k vf is the preset V / F ratio coefficient; Step S202: After completing the constant control of the voltage-to-frequency ratio in step S201, drive the motor in an open-loop control manner; according to the preset parameters in step S201, generate corresponding control signals through inverse Park transformation and SVPWM, apply them to the stator windings of the motor to generate a rotating magnetic field, and drive the motor to start accelerating from the stationary state; during the acceleration process, the rotational speed of the motor gradually increases, and the self-increasing angle continuously increases according to the preset linear increasing law; meanwhile, monitor the operating frequency of the motor in real time. When it is monitored that the operating frequency of the motor reaches the current closed-loop frequency set in step S100, it indicates that the motor has completed the acceleration process in the V / F startup stage.

4. The sensorless FOC starting method for the heavy-duty industrial fan according to claim 1, wherein: The step S300 includes: Step S301: When it is monitored that the operating frequency of the motor reaches the current closed-loop frequency set in Step S100, trigger the control mode switching mechanism to switch the control mode from the open-loop control mode in the V / F startup stage to the current closed-loop control mode; after completing the mode switching, collect the direct-axis current and quadrature-axis current of the motor in real time, and determine the target value of the direct-axis current and the target value of the quadrature-axis current according to the current closed-loop given current preset in Step S100; compare the collected actual direct-axis current with the target direct-axis current to calculate the direct-axis current error; compare the collected actual quadrature-axis current with the target quadrature-axis current to calculate the quadrature-axis current error; input the calculated direct-axis current error and quadrature-axis current error into the corresponding PI regulators respectively to adjust the direct-axis and quadrature-axis voltages to reach the preset target values; Step S302: Based on the final frequency of V / F startup, calculate the initial incremental angle of open-loop angle according to the formula: Δθ0 = f cl ×T×360°; where Δθ0 represents the initial incremental angle of open-loop angle, and f cl is the current closed-loop frequency, and T is the angle increment period; set the angle increment period to be equal to the execution period of the current loop; in each angle increment period, multiply Δθ0 by the angle increment coefficient m to obtain the actual incremental angle Δθ = Δθ0×m, where m ∈ (1, 2); in the open-loop angle mode, combine the direct-axis and quadrature-axis voltages output by the PI regulator, generate a control signal through the inverse Park transformation and SVPWM, and apply it to the stator winding of the motor to drive the motor to continuously accelerate; during the acceleration process, monitor the operating frequency of the motor in real time. When it is monitored that the operating frequency of the motor reaches the open-loop final frequency set in step S100, switch to the closed-loop control regulated by the sensorless position observer, and the heavy-duty industrial fan enters the stable operating state.

5. Sensorless FOC starting system for overloaded industrial fans, characterized in that: The system includes: an initialization module, a V / F startup module, a current closed-loop angle open-loop driving module, and a closed-loop control module; The initialization module performs power-on initialization on the brushless motor of the heavy-duty industrial fan to complete power supply and drive signal preparation; at the same time, sets multiple frequency control variables to control the startup process; The V / F startup module adopts the V / F startup method, maintains the constant ratio of voltage to frequency through the preset direct-axis voltage, quadrature-axis voltage, and self-increasing angle, and drives the motor to accelerate from the stationary state to the current closed-loop frequency in an open-loop control manner; The current closed-loop angle open-loop driving module switches to the current closed-loop control mode after the operating frequency of the motor reaches the current closed-loop frequency, adjusts the direct-axis current and quadrature-axis current through PI, and generates an increasing angle based on the final frequency of V / F startup, and continues to drive the motor to accelerate to the open-loop final frequency in an angle open-loop manner; The closed-loop control module switches to the closed-loop control regulated by the sensorless position observer after the operating frequency of the motor reaches the open-loop final frequency, and the heavy-duty industrial fan enters the stable operating state.

6. The sensorless FOC starting system for heavy-duty industrial fans according to claim 5, characterized in that: The multiple frequency control variables set by the initialization module include the open-loop final frequency, V / F frequency acceleration, given operating frequency, current closed-loop frequency, and current closed-loop given current; The open-loop final frequency represents the frequency threshold for switching from current closed-loop driving to closed-loop control regulated by the sensorless position observer; the V / F frequency acceleration is used to control the acceleration / deceleration frequency in the V / F startup stage; the given operating frequency represents the target frequency for the motor to reach stable operation; the current closed-loop frequency serves as the frequency threshold for switching from the V / F startup stage to the current closed-loop driving stage; the current closed-loop given current represents the target values of the direct-axis current and quadrature-axis current in the current closed-loop stage.

7. The sensorless FOC starting system for heavy-duty industrial fans according to claim 5, characterized in that: The V / F startup module includes a V / F control unit and a real-time monitoring unit; the V / F control unit is used to preset the direct-axis voltage, quadrature-axis voltage, and self-increasing angle, and maintain the constant ratio of voltage to frequency according to the adjustment mechanism during startup to keep the motor magnetic flux stable; The real-time monitoring unit generates the control signal for driving the motor through inverse Park transformation and SVPWM, and real-time monitors the operating frequency of the motor. When the current closed-loop frequency is reached, it triggers the switching to the current closed-loop control mode.

8. The sensorless FOC starting system for heavy-duty industrial fans according to claim 5, characterized in that: The current closed-loop and angle open-loop drive module includes a current regulation unit and an angle open-loop acceleration unit; when the motor frequency reaches the current closed-loop frequency, the current regulation unit switches to the current closed-loop control mode, collects the direct-axis and quadrature-axis currents, and adjusts them through a PI regulator to make the current reach the target value; based on the final frequency of V / F startup, the angle open-loop acceleration unit calculates the initial increment angle of the angle open-loop, multiplies it by the angle increment coefficient in each period to obtain the actual increment angle, combines the voltage output by the PI regulator, generates a control signal through inverse Park transformation and SVPWM, drives the motor to continuously accelerate, and monitors the motor frequency. When the open-loop final frequency is reached, the next mode switch is triggered.

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