Speed sensorless control method for long-stator linear motor

Abstract

The invention relates to the technical field of motor control, in particular to a speed sensorless control method of a long-stator linear motor for a maglev train in a full-speed domain range. According to the method, when the train runs at a low speed, the mechanical position sensor is adopted for control, and control precision is high; when the train runs at a high speed, speed sensorless control based on extended back electromotive force is adopted, so that control errors caused by data transmission delay can be avoided; and a weighted average switching algorithm is provided when switching is controlled by adopting a mechanical sensor at a low speed and adopting a speed-free sensor at a high speed, and the weighted average switching algorithm comprises motor rotating speed switching and motor angle switching, so that stable transition of the rotating speed and the angle of the motor during high and low speed switching is realized, and overcurrent of the motor is avoided. By adopting the method, stable operation of the long-stator linear motor in a full-speed domain range can be realized, and safe operation of a train is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of motor control, and in particular to a speed sensorless control method for a long-stator linear motor. Background Art

[0002] The maglev train is driven by a long-stator linear motor. The control of the long-stator linear motor requires motor speed and angle information, which can be obtained by detecting the stator tooth slots and the positioning mark plate of the track through the speed sensor, and sent to the ground control system through a wireless transmission device. However, when the train is running at high speed, the train position changes greatly in the fixed wireless transmission interval, and it is impossible to ensure that the ground traction control system obtains accurate control information, which affects the stable operation of the train. Severe delays may cause the train to lose control. Therefore, when the train is running at high speed, it is necessary to adopt a speed sensorless control algorithm to observe the motor speed and angle information in real time through the motor stator voltage and current, reduce the control information transmission delay, and improve the stability and safety of the train operation.

[0003] At present, there are many control strategies for long-stator linear motors without speed sensors, including model reference adaptive observer, sliding film observer, extended Kalman filter, extended back-EMF observer, etc. Most of the research is concentrated in the medium and high speed area. This type of method requires the use of motor stator voltage and current information. When the train is running at low speed, the nonlinearity of the switching device causes the system to produce a large noise error, and the identification accuracy is reduced. In addition, there are methods based on high-frequency injection. This method works better at low speeds, but this type of method requires continuous excitation during the operation of the motor, which reduces the voltage utilization of the inverter. In addition, this type of method has a complex signal processing process and poor dynamic performance. Therefore, in practical applications, the mechanical speed sensor solution is still used for low-speed operation of trains. The train is controlled by mechanical speed sensors when running at low speeds, and speed sensorless control is used when running at high speeds. Due to the transmission delay of the mechanical speed sensor to collect data and the error of the speed sensorless estimated data, it is easy to cause motor overcurrent when switching directly between the two, affecting the stable operation of the train, so a suitable transition switching algorithm is needed, and there is little research on the existing technology. Summary of the invention

[0004] In order to overcome the technical defects that the direct switching between the mechanical speed sensor and the speed sensorless data collection data is prone to cause motor overcurrent and affect the stable operation of the train due to the transmission delay of the mechanical speed sensor and the error of the speed sensorless estimated data, the present invention provides a long stator linear motor speed sensorless control method. The method of the present invention provides a weighted average switching algorithm when transitioning between the use of mechanical sensors at low speed and the use of speed sensorless at high speed. In the method, the mechanical speed sensor is used for high control accuracy when the train is running at low speed, and the speed sensorless is used for high speed operation to avoid the control delay caused by wireless transmission, and a good transition is achieved between the mechanical sensor at low speed and the speed sensorless at high speed, thereby achieving stable control of the train in the entire operating range.

[0005] The present invention provides a speed sensorless control method for a long stator linear motor, the steps of which are:

[0006] S1. Reconstruct three-phase stator voltage:

[0007] Due to the influence of factors such as controller calculation delay and switch device conduction delay, the voltage command of the controller may have a certain error with the voltage at the end of the long stator linear motor. In order to measure the motor voltage more accurately, it is necessary to use the bus voltage and the duty cycle of the switch tube to calculate the phase voltage of the motor; according to the bus voltage u DC And the duty cycle S of the three-phase upper bridge arm switch tube abc When voltage reconstruction is performed, the phase voltage u in the three-phase rotating coordinate system is A 、u B 、u C The calculation formula is:

[0008]

[0009] S2, voltage and current conversion:

[0010] The speed sensorless control algorithm uses the voltage and current in the two-phase stationary coordinate system, and the motor control also uses the current in the two-phase rotating coordinate system. The voltage u in the three-phase rotating coordinate system is reconstructed using the Clark transformation formula A 、u B 、u C Converted into voltage u in two-phase stationary coordinate system α 、u β ; Use Clark transformation formula to transform the current i in the three-phase rotating coordinate system a 、i b Converted into the current i in the two-phase stationary coordinate system α 、i β ; Use Park transformation formula to convert the current i in the two-phase stationary coordinate system α 、i βConverted into the current i in the two-phase rotating coordinate system d 、i q ; The Clark transformation formulas for voltage and current and the Park transformation formula for current are:

[0011]

[0012]

[0013]

[0014] S3. Build an extended back-EMF observer:

[0015] The extended back EMF term contains flux information, using i d = 0 control, and the long-stator linear synchronous motor has large leakage inductance, and the salient pole effect is not obvious. The extended back-EMF and the back-EMF are slightly different in amplitude during the dynamic process, but there is no difference between the two in the steady state. Therefore, the magnetic flux can be calculated based on the observed extended back-EMF; then the mathematical model of the long-stator linear synchronous motor in the αβ coordinate system is:

[0016]

[0017] Where, L d , L q is the direct-axis and quadrature-axis inductance of the motor; R is the stator phase winding resistance, ω r is the rotor angular velocity; E is the extended back electromotive force, E=(L d -L q )(ω r i d -pi q )+ω r ψ f ;in, contains position information, which is defined as the extended back EMF term, then

[0018]

[0019] In the formula, E α and E β are the components of the extended back electromotive force E on the α and β axes of the two-phase stationary coordinate system respectively;

[0020] The mathematical model of the long stator linear motor in the two-phase stationary coordinate system is obtained:

[0021]

[0022] In the formula, u α 、u β is the given voltage in the two-phase stationary coordinate system, i α 、iβ is the actual value of the current in the two-phase stationary coordinate system, is the estimated value of the current in the two-phase stationary coordinate system; u α 、u β 、i α 、i β It is obtained indirectly through measurement transformation. They are used as the input of the extended back-EMF observer. The extended back-EMF term cannot be measured. The difference between the measured value and the estimated value of the current can be calculated, and then the estimated value of the extended back-EMF can be expressed through the PI regulator. The component of the extended back-EMF in the two-phase stationary coordinate system is and and The calculation formula is:

[0023]

[0024] in, is the estimated value of the current, ω rH is the motor speed estimated by the speed sensorless control algorithm,

[0025]

[0026] S4. Estimate motor speed and angle:

[0027] The motor speed and angle estimation is based on the phase-locked loop principle. According to the two orthogonal components of the extended back electromotive force, the angle information of the long-stator linear motor is extracted; the tracking angle error function is:

[0028]

[0029] When the error is 0, the motor angle estimate θ H It is approximately equal to the actual value of the motor angle θ; after being processed by the PI regulator, the angular velocity ω of the motor rotor is obtained rH ; Then integrate the rotor angular velocity to get the estimated value of the rotor angle θ H ;

[0030] S5, weighted switching of train speed and motor angle:

[0031] The train is controlled by mechanical sensors when running at low speeds, and by speed sensorless control when running at high speeds. Due to the transmission delay of mechanical sensor data collection and the error of speed sensorless estimated data, direct switching between the two can easily cause motor overcurrent, affecting system safety, so a weighted average switching algorithm is required; the weighted average switching algorithm includes motor speed switching and motor angle switching;

[0032] Speed ​​ω of long stator linear motor in full speed range rz The available formula is:

[0033] ω rz =λω rL +(1-λ)ω rH ,

[0034] The corresponding motor angle θ in the full speed range z It can be expressed as:

[0035] θ z =λθ L +(1-λ)θ H , where the expression of λ is

[0036]

[0037] In the formula, ω L ,ω H They are the upper limit of the motor speed controlled by a mechanical speed sensor at low speed and the lower limit of the motor speed controlled by a speed sensorless at high speed, ω rz is the motor speed after the weighted average switching process.

[0038] The method of the present invention uses the motor speed and angle collected by the mechanical speed sensor for control when the speed of the long stator linear motor is low; when the motor speed is high, the motor speed and angle estimated by the speedless sensor are used for control; and a weighted average switching algorithm is provided when the motor is switched between mechanical sensor control at low speed and speedless sensor control at high speed, so as to smoothly switch the motor speed and angle and realize stable control of the long stator linear motor in the full speed range. The speedless sensor control method used estimates the two-phase extended back electromotive force based on the extended back electromotive force model, and then extracts the speed and angle information of the motor based on the phase-locked loop principle, and the speedless sensor control algorithm always operates synchronously during the operation of the motor.

[0039] Compared with the prior art, the technical solution provided by the present invention has the following technical effects: by adopting the speed sensorless control method of the long stator linear motor suitable for the maglev train in the full speed range, the mechanical speed sensor is used for the low-speed operation of the train to achieve high control accuracy, and the speed sensorless is used for the high-speed operation to avoid the control delay caused by wireless transmission, and a good transition between the mechanical sensor used at low speed and the speed sensorless used at high speed is achieved, thereby achieving stable control of the train in the entire operating range and improving the stability and safety of the train operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 A control block diagram of a speed sensorless control method for a long-stator linear motor according to an embodiment of the present invention;

[0043] Figure 2 It is a flow chart of a speed sensorless control method of a long-stator linear motor described in an embodiment of the present invention;

[0044] Figure 3 is a control block diagram of an extended back electromotive force observer described in a certain embodiment of the present invention;

[0045] Figure 4 A block diagram of the motor speed and angle estimation principle in an embodiment of the present invention;

[0046] Figure 5 Schematic diagram of the weighted switching principle of motor speed and angle in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0048] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0049] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0050] In one embodiment, Figures 1 to 5 As shown, a speed sensorless control method for a long stator linear motor is disclosed, wherein the motor angle and speed collected by the mechanical speed sensor of the long stator linear motor are θ L and ω rL The motor angle and speed estimated by the speed sensorless control method based on extended back electromotive force are θ H and ω rH ,θ L ,θ H ,ω rL ,ω rHThe weighted average switching is fully involved in the calculation of the entire motor operation process. The output of the weighted average switching is the motor angle θ used for motor control. z and speed ω rz The speed weighted average switch sets the speed upper limit of the mechanical speed sensor control at low speed. L , and the lower speed limit of high speed sensorless control ω H , when the weighted motor speed ω rz Below the lower speed limit L When the motor angle θ z and speed ω rz and the data collected by the mechanical speed sensor; when the weighted motor speed ω rz Above the upper speed limit H When the motor angle θ z and speed ω rz Equal to the data estimated without speed sensor; when the weighted motor speed ω rz Between the lower speed limit L and upper speed limitω H When the motor angle θ z and speed ω rz The result used is the weighted average calculation result of the data collected by the mechanical sensor and the estimated data without the speed sensor.

[0051] The specific steps are:

[0052] S1. Reconstruct three-phase stator voltage:

[0053] Due to the influence of factors such as controller calculation delay and switch device conduction delay, the voltage command of the controller may have a certain error with the voltage at the end of the long stator linear motor. In order to measure the motor voltage more accurately, it is necessary to use the bus voltage and the duty cycle of the switch tube to calculate the phase voltage of the motor; according to the bus voltage u DC And the duty cycle S of the three-phase upper bridge arm switch tube abc When voltage reconstruction is performed, the phase voltage u in the three-phase rotating coordinate system is A 、u B 、u C The calculation formula is:

[0054]

[0055] S2, voltage and current conversion:

[0056] The speed sensorless control algorithm uses the voltage and current in the two-phase stationary coordinate system, and the motor control also uses the current in the two-phase rotating coordinate system. The voltage u in the three-phase rotating coordinate system is reconstructed using the Clark transformation formula A 、u B 、uC Converted into voltage u in two-phase stationary coordinate system α 、u β ; Use Clark transformation formula to transform the current i in the three-phase rotating coordinate system a 、i b Converted into the current i in the two-phase stationary coordinate system α 、i β ; Use Park transformation formula to convert the current i in the two-phase stationary coordinate system α 、i β Converted into the current i in the two-phase rotating coordinate system d 、i q ; The Clark transformation formulas for voltage and current and the Park transformation formula for current are:

[0057]

[0058]

[0059]

[0060] S3. Build an extended back-EMF observer:

[0061] The extended back EMF term contains flux information, using i d = 0 control, and the long-stator linear synchronous motor has large leakage inductance, and the salient pole effect is not obvious. The extended back-EMF and the back-EMF are slightly different in amplitude during the dynamic process, but there is no difference between the two in the steady state. Therefore, the magnetic flux can be calculated based on the observed extended back-EMF; then the mathematical model of the long-stator linear synchronous motor in the αβ coordinate system is:

[0062]

[0063] Where, L d , L q is the direct-axis and quadrature-axis inductance of the motor; R is the stator phase winding resistance, ω r is the rotor angular velocity; E is the extended back electromotive force, E=(L d -L q )(ω r i d -pi q )+ω r ψ f ;in, contains position information, which is defined as the extended back EMF term, then

[0064]

[0065] In the formula, E α and E βare the components of the extended back electromotive force E on the α and β axes of the two-phase stationary coordinate system respectively;

[0066] The mathematical model of the long stator linear motor in the two-phase stationary coordinate system is obtained:

[0067]

[0068] In the formula, u α 、u β is the given voltage in the two-phase stationary coordinate system, i α 、i β is the actual value of the current in the two-phase stationary coordinate system, is the estimated value of the current in the two-phase stationary coordinate system; u α 、u β 、i α 、i β It is obtained indirectly through measurement transformation. They are used as the input of the extended back-EMF observer. The extended back-EMF term cannot be measured. The difference between the measured value and the estimated value of the current can be calculated, and then the estimated value of the extended back-EMF can be expressed through the PI regulator. The component of the extended back-EMF in the two-phase stationary coordinate system is and and The calculation formula is:

[0069]

[0070] in, is the estimated value of the current, ω rH is the motor speed estimated by the speed sensorless control algorithm,

[0071]

[0072] S4. Estimate motor speed and angle:

[0073] The motor speed and angle estimation is based on the phase-locked loop principle. According to the two orthogonal components of the extended back electromotive force, the angle information of the long stator linear motor is extracted, and the tracking angle error function is:

[0074]

[0075] When the error is 0, the motor angle estimate θ H It is approximately equal to the actual value of the motor angle θ; after being processed by the PI regulator, the angular velocity ω of the motor rotor is obtained rH ; Then integrate the rotor angular velocity to get the estimated value of the rotor angle θ H ;

[0076] S5, weighted switching of train speed and motor angle:

[0077] The train is controlled by mechanical sensors when running at low speeds, and by speed sensorless control when running at high speeds. Due to the transmission delay of mechanical sensor data collection and the error of speed sensorless estimated data, direct switching between the two can easily cause motor overcurrent, affecting system safety, so a weighted average switching algorithm is required; the weighted average switching algorithm includes motor speed switching and motor angle switching;

[0078] Speed ​​ω of long stator linear motor in full speed range rz The available formula is:

[0079] ω rz =λω rL +(1-λ)ω rH ,

[0080] The corresponding motor angle θ in the full speed range z It can be expressed as:

[0081] θ z =λθ L +(1-λ)θ H , where the expression of λ is

[0082]

[0083] In the formula, ω L ,ω H They are the upper limit of the motor speed controlled by a mechanical speed sensor at low speed and the lower limit of the motor speed controlled by a speed sensorless at high speed, ω rz is the motor speed after the weighted average switching process.

[0084] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A speed sensorless control method for a long stator linear motor, characterized in that: The steps are: S1. Reconstruct three-phase stator voltage: According to the bus voltage u DC And the duty cycle S of the three-phase upper bridge arm switch tube abc When voltage reconstruction is performed, the phase voltage u in the three-phase rotating coordinate system is A 、u B 、u C The calculation formula is: S2, voltage and current conversion: The voltage u in the three-phase rotating coordinate system generated by voltage reconstruction using the Clark transformation formula A 、u B 、u C Converted into voltage u in two-phase stationary coordinate system α 、u β ; Use Clark transformation formula to transform the current i in the three-phase rotating coordinate system a 、i b Converted into the current i in the two-phase stationary coordinate system α 、i β ; Use Park transformation formula to convert the current i in the two-phase stationary coordinate system α 、i β Converted into the current i in the two-phase rotating coordinate system d 、i q ; The Clark transformation formulas for voltage and current and the Park transformation formula for current are: S3. Build an extended back-EMF observer: The extended back EMF term contains flux information, using i d = 0 control, the flux linkage is calculated according to the observed extended back electromotive force; then the mathematical model of the long stator linear synchronous motor in the αβ coordinate system is: Where, L d , L q is the direct-axis and quadrature-axis inductance of the motor; R is the stator phase winding resistance, ω r is the rotor angular velocity; E is the extended back electromotive force, E=(L d -L q )(ω r i d -pi q )+ω r ψ f ;in, contains position information, which is defined as the extended back EMF term, then In the formula, E α and E β are the components of the extended back electromotive force E on the α and β axes of the two-phase stationary coordinate system respectively; The mathematical model of the long stator linear motor in the two-phase stationary coordinate system is obtained: In the formula, u α 、u β is the given voltage in the two-phase stationary coordinate system, i α 、i β is the actual value of the current in the two-phase stationary coordinate system, is the estimated value of the current in the two-phase stationary coordinate system; u α 、u β 、i α 、i β Obtained indirectly through measurement transformation, they serve as the input of the extended back-EMF observer; the components of the extended back-EMF in the two-phase stationary coordinate system are and and The calculation formula is: in, is the estimated value of the current, ω rH is the motor speed estimated by the speed sensorless control algorithm, S4. Estimate motor speed and angle: The motor speed and angle estimation is based on the phase-locked loop principle. According to the two orthogonal components of the extended back electromotive force, the angle information of the long stator linear motor is extracted, and the tracking angle error function is: When the error is 0, the motor angle estimate θ H It is approximately equal to the actual value of the motor angle θ; after being processed by the PI regulator, the angular velocity ω of the motor rotor is obtained rH ; Then integrate the rotor angular velocity to get the estimated value of the rotor angle θ H ; S5, weighted switching of train speed and motor angle: The train is controlled by mechanical sensors when running at low speeds, and by speed sensorless control when running at high speeds. Due to the transmission delay of mechanical sensor data collection and the error of speed sensorless estimated data, a weighted average switching algorithm is adopted; the weighted average switching algorithm includes motor speed switching and motor angle switching; the speed ω of the long stator linear motor in the full speed range rz The available formula is: oh rz =I am rL +(1-λ)ω rH , The corresponding motor angle θ in the full speed range z It can be expressed as: i z =λθ L +(1-λ)θ H , The expression of λ is In the formula, ω L ,ω H They are the upper limit of the motor speed controlled by a mechanical speed sensor at low speed and the lower limit of the motor speed controlled by a speed sensorless at high speed, ω rz is the motor speed after the weighted average switching process.

Images