Starting method of permanent magnet synchronous motor without position sensor
Through the fast start strategy of IF current closed loop and speed open loop, the jitter and unreliability problems of position sensor-free permanent magnet synchronous motor during low-speed start-up, achieving reliable start-up and good operation effect of the motor under voltage fluctuations.
Patent Information
- Application Number
- CN202411577853.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-07
- Publication Date
- 2025-02-18
AI Technical Summary
The permanent magnet synchronous motor without position sensors has jitter and unreliability during low-speed start-up. Especially in the case of voltage fluctuations, the existing VF startup method is difficult to control the current magnitude, resulting in loss of steps and damage to the controller.
Using the fast start strategy of IF current closed loop and speed open loop, by setting the IF primary function curve, gradually lowering the operating frequency and current, so that the angle estimated by the observer coincides with the open loop angle, and then switch to the angle of the closed loop observer to complete Open-loop and closed-loop start process.
The smooth transition between open-loop start and closed-loop control is achieved, the motor runs well, effectively controls the current magnitude, and starts reliably in the case of voltage fluctuations, avoiding the risk of loss of steps and controller damage.
Smart Images
Figure CN119483359A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of motors, and in particular to a method for starting a permanent magnet synchronous motor without a position sensor. Background Art
[0002] One of the difficulties in the industry for controlling permanent magnet synchronous motors without position sensors is low-speed starting, which requires no jitter during starting and as reliable and successful as possible. The usual practice is to start with a strong pull in VF (voltage-frequency control mode). The problem with VF starting is that the current cannot be controlled, and it is difficult to ensure reliable starting under voltage fluctuations. In addition, the transition stage between open-loop starting and closed-loop control is often accompanied by switching current jitter, resulting in poor motor operation and frequent loss of steps, which may damage the controller in severe cases.
[0003] Therefore, the existing VF startup is unreliable and needs to be improved. Summary of the invention
[0004] The object of the present invention is to provide a method for starting a permanent magnet synchronous motor without a position sensor, so as to solve the problems raised in the above background technology.
[0005] To achieve the above object, the present invention provides the following technical solutions:
[0006] A method for starting a permanent magnet synchronous motor without a position sensor comprises the following steps:
[0007] Step 1, determine the initial position of the motor rotor;
[0008] Step 2, set an IF linear function curve, whose independent variable is frequency (speed), and dependent variable is current, to drive the motor to rotate;
[0009] Step 3: The given operating frequency is gradually reduced, and the current given value is also reduced accordingly, so that the angle estimated by the observer slowly coincides with the open-loop angle;
[0010] Step 4: When the motor speed reaches the second threshold speed and the angle difference between the open-loop angle and the angle observed by the observer is less than the second set value, the open-loop angle used for current decoupling is switched to the angle of the closed-loop observer to complete the open-loop and closed-loop startup process.
[0011] As a further solution of the present invention: in step 1, the initial position of the motor rotor is determined by forced pre-positioning.
[0012] As a further solution of the present invention: in step 1, the initial position of the motor rotor is determined by IPD pulse injection.
[0013] As a further solution of the present invention: In step 2, the current and frequency (IF) are used as a linear function as the first curve, and the starting point and the end point of the linear function are determined. The linear function can be determined by two points, and the coordinates of the starting point (N start ,I start ), end point coordinates (N end ,I end ), where I start Represents the starting given current of Q axis, N start Represents the given starting speed, I end Represents the given current at the end of the Q axis, N end Represents a given terminal speed, and the open-loop angle is integrated according to the given speed value;
[0014] The motor is dragged quickly according to the first curve. When the open-loop speed N openloop The speed N estimated by the observer obs At the same time, N openloop >N Thr , N obs >N Thr Then go to step 3, where N Thr It is a first threshold speed set in advance.
[0015] As a further solution of the present invention: in step 2, the starting current I start The value is the rated current, I end The value is 30% of the rated current, N start is 0, N end It is the open loop ending speed, which is 2% to 10% of the rated speed.
[0016] As a further solution of the present invention: in step 3, the second curve is obtained by using the current and frequency as a linear function, and the given current also decreases, but is not less than the lower limit threshold I Thr , the speed increases, the open-loop acceleration is reduced, and the second curve is entered. At the same time, the open-loop angle θ needs to be determined. openloop Angle θ with the observer obs When the deviation between the two is θ error Stable and less than the first set value θ Thr When the switch is made, the open loop angle is entered, i.e. θ error <θ Thr ,θ Thr It should not be too large, preferably 5° to 10°.
[0017] As a further solution of the present invention: in step 3, when the switching condition is not met, that is, when the open-loop angle deviates too much from the observer angle and the deviation is relatively fixed, the open-loop acceleration rate is automatically adjusted according to the current deviation angle to make it closer to the observer angle. The calculation method is: This acceleration rate is superimposed on the previously designed acceleration rate, and the θ error , until θ is satisfied error <θ Thr Switching is available only when
[0018] Compared with the prior art, the beneficial effects of the present invention are: the present invention proposes a fast starting strategy of IF current closed loop and speed open loop, the transition phase between open loop starting and closed loop control is switched smoothly, the motor operation effect is good, the current size is effectively controlled, and the starting is reliable under voltage fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is the IF diagram of the motor.
[0020] Figure 2 Schematic diagram of the open-loop angle and the observer observation angle.
[0021] Figure 3 This is a schematic diagram showing that the open-loop angle and the observer angle have the same frequency but a large phase deviation. DETAILED DESCRIPTION
[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0023] See also Figure 1 , a method for starting a permanent magnet synchronous motor without a position sensor, comprising the following steps:
[0024] Step 1, determine the initial position of the motor rotor;
[0025] Step 2, set an IF linear function curve, whose independent variable is frequency (speed), and dependent variable is current, to drive the motor to rotate;
[0026] Step 3: The given operating frequency is gradually reduced, and the current given value is also reduced accordingly, so that the angle estimated by the observer slowly coincides with the open-loop angle;
[0027] Step 4: When the motor speed reaches the second threshold speed and the angle difference between the open-loop angle and the angle observed by the observer is less than the second set value, the open-loop angle used for current decoupling is switched to the angle of the closed-loop observer to complete the open-loop and closed-loop startup process. Figure 2 shown.
[0028] In some cases, the open-loop angle and the observer angle may not coincide with each other and the angle deviation between the two may be large, but the open-loop speed is the same as the speed estimated by the observer, that is, the open-loop angle and the observer angle have the same frequency but the phase deviation is large, such as Figure 3 As shown, in this case, it is necessary to manually move the open-loop angle closer to the observer angle to achieve smooth switching.
[0029] In this example: See Figure 1 ,In step 1, the initial position of the motor rotor is determined by forced pre-positioning.
[0030] In this example: See Figure 1 ,In step 1, the initial position of the motor rotor is determined by IPD pulse injection.
[0031] In this example: See Figure 1 In step 2, a linear function is made of current and frequency (IF) as the first curve, and the starting point and the end point of the linear function are determined. The linear function can be determined by two points. The coordinates of the starting point (N start ,I start ), end point coordinates (N end ,I end ), where I start Represents the starting given current of Q axis, N start Represents a given starting speed (there is a proportional relationship between speed and frequency), I end Represents the given current at the end of the Q axis, N end Represents a given terminal speed, and the open-loop angle is integrated according to the given speed value;
[0032] The motor is dragged quickly according to the first curve. When the open-loop speed N openloop The speed N estimated by the observer obs At the same time, N openloop >N Thr , N obs >N Thr Then go to step 3, where N Thr It is a first threshold speed set in advance.
[0033] In this example: See Figure 1 In step 2, the open loop angle is integrated according to the given speed value. For sensorless motors, starting acceleration usually requires a large current. After the motor has been dragged, the current can be gradually reduced. Therefore, the starting current I start The value is the rated current, I end The value is 30% of the rated current, N sart is 0, N endIt is the open-loop ending speed, which is 2% to 10% of the rated speed and is close to the switching speed.
[0034] In this example: See Figure 1 In step 3, the second curve is obtained by using the current and frequency as a linear function. At the same time, the given current also decreases, but is not less than the lower limit threshold I Thr , the speed increases, the open-loop acceleration is reduced, and the second curve is entered. At the same time, the open-loop angle θ needs to be determined. openloop Angle θ with the observer obs When the deviation between the two is θ error Stable and less than the first set value θ Thr When the switch is made, the open loop angle is entered, i.e. θ error <θ Thr ,θ Thr It should not be too large, preferably 5° to 10°.
[0035] In this example: See Figure 1 In step 3, when the switching condition is not met, that is, when the open-loop angle deviates too much from the observer angle and the deviation is relatively fixed, the open-loop acceleration rate is automatically adjusted according to the current deviation angle to make it closer to the observer angle. The calculation method is: This acceleration rate is superimposed on the previously designed acceleration rate, and the θ error , until θ is satisfied error <θ Thr Switching is available only when
[0036] T adjust Free to choose, but T adjust It should not be selected too small, otherwise it will easily cause switching jitter.
[0037] The present invention proposes a fast starting strategy of IF current closed loop and speed open loop, the transition phase between open loop starting and closed loop control is switched smoothly, the motor operation effect is good, the current size is effectively controlled, and the starting is reliable under voltage fluctuations.
[0038] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered as exemplary and non-restrictive in all respects.
[0039] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.
Claims
1. A method for starting a permanent magnet synchronous motor without a position sensor, characterized in that: The method for starting the position sensorless permanent magnet synchronous motor comprises the following steps: Step 1, determine the initial position of the motor rotor; Step 2, set an IF linear function curve, whose independent variable is frequency (speed), and dependent variable is current, to drive the motor to rotate; Step 3: The given operating frequency is gradually reduced, and the current given value is also reduced accordingly, so that the angle estimated by the observer slowly coincides with the open-loop angle; Step 4: when the motor speed reaches the second threshold speed and the angle difference between the open-loop angle and the angle observed by the observer is less than a second set value, the open-loop angle used for current decoupling is switched to the angle of the closed-loop observer to complete the open-loop and closed-loop startup process.
2. The method for starting a position sensorless permanent magnet synchronous motor according to claim 1, characterized in that: In step 1, the initial position of the motor rotor is determined by forced pre-positioning.
3. The method for starting a position sensorless permanent magnet synchronous motor according to claim 1, characterized in that: In step 1, the initial position of the motor rotor is determined by IPD pulse injection.
4. The method for starting a position sensorless permanent magnet synchronous motor according to claim 1, characterized in that: In step 2, a linear function is made with current and frequency (IF) as the first curve, and the starting point and the end point of the linear function are determined. The linear function can be determined by two points, and the coordinates of the starting point (N start , I start ), end point coordinates (N end , I end ), where I start Represents the starting given current of Q axis, N start Represents the given starting speed, I end Represents the given current at the end of the Q axis, N end Represents a given terminal speed, and the open-loop angle is integrated according to the given speed value; The motor is dragged quickly according to the first curve. When the open-loop speed N openloop The speed N estimated by the observer obs At the same time, N openloop >N Thr , N obs >N Thr Then go to step 3, where N Thr It is a first threshold speed set in advance.
5. The method for starting a position sensorless permanent magnet synchronous motor according to claim 4, characterized in that: In step 2, the starting current I start The value is the rated current, I end The value is 30% of the rated current, N start is 0, N end It is the open loop ending speed, which is 2% to 10% of the rated speed.
6. The method for starting a position sensorless permanent magnet synchronous motor according to claim 1, characterized in that: In step 3, the second curve is obtained by using the current and frequency as a linear function. At the same time, the given current also decreases, but is not less than the lower limit threshold I Thr , the speed increases, the open-loop acceleration is reduced, and the second curve is entered. At the same time, the open-loop angle θ needs to be determined. openloop Angle θ with the observer obs When the deviation between the two is θ error Stable and less than the first set value θ Thr When the angle is θ, the switch can be made directly to enter the open loop angle, i.e. error <θ Thr ,θ Thr It should not be too large, preferably 5° to 10°.
7. The method for starting a position sensorless permanent magnet synchronous motor according to claim 6, characterized in that: In step 3, when the switching condition is not met, that is, when the open-loop angle deviates too much from the observer angle and the deviation is relatively fixed, the open-loop acceleration rate is automatically adjusted according to the current deviation angle to make it closer to the observer angle. The calculation method is: This acceleration rate is superimposed on the previously designed acceleration rate, and the θ error , until θ is satisfied error <θ Thr Switching is available only when
Citation Information
Cited By
Motor and control method and device thereof, storage medium and computer program product
CN120566969A