Method for suppressing traction fluctuation of magnetically levitated train

Abstract

The invention relates to the technical field of magnetic levitation train traction force control, in particular to a magnetic levitation train traction force fluctuation suppression method, which comprises the following steps of: estimating mutual inductance flux linkage between a stator winding and an exciting winding in real time by observing extended back electromotive force of a long stator linear motor; the mutual inductance flux linkage parameters are used for calculating q-axis current and feed-forward voltage, output voltage is adjusted on line, and traction fluctuation caused by excitation current changes of the suspension system can be effectively restrained. The observed mutual inductance flux linkage parameters are used for real-time control of the traction system of the long-stator linear motor, and traction fluctuation caused by a suspension system can be effectively restrained when a track is uneven, load disturbance occurs or external force interference in the vertical direction occurs.

Description

Technical Field

[0001] The invention relates to the technical field of traction force control of maglev trains, and in particular to a method for suppressing fluctuations in traction force of maglev trains. Background Art

[0002] The maglev train is driven by a long stator linear motor (LSLSM). The primary stator core and three-phase armature winding of the long stator linear motor are installed along the track, and the secondary (i.e., excitation pole) electromagnet is installed on the suspension frame under the car body. The traveling wave magnetic field generated by the primary stator three-phase armature winding is coupled with the DC magnetic field of the secondary electromagnet to generate traction, which drives the train to run; the primary stator core and the secondary electromagnet attract each other to generate suspension force, so that the train is suspended 8 to 12 mm above the track.

[0003] Since the excitation poles of the long stator linear motor are also the electromagnets that generate the suspension force, there is a nonlinear coupling relationship between the traction force and the suspension force. Adjusting one variable will affect the other variable. In order to achieve the decoupling control of the traction force and the suspension force, the change of the stator current should have as little effect on the suspension force of the train as possible. The motor is mostly i d = 0, the armature reaction is minimal, the coupling between the two is minimal, and the stator current i q The excitation current of the excitation magnetic pole controls the traction force and the suspension force respectively, so that independent control of the traction system and the suspension system can be achieved.

[0004] However, in the actual operation of the train, due to the uneven track, load disturbance or vertical external force interference, the suspension air gap will fluctuate. In order to keep the suspension air gap constant, the suspension control system will dynamically adjust the excitation current to keep the air gap stable near the rated air gap. Figure 3 As shown in the figure, the main components of the suspension control system of the maglev train include: power supply, suspension controller, suspension sensors (gap sensor, current sensor, acceleration sensor), chopper and suspension electromagnet. The electromagnetic attraction and the suspension gap are inversely proportional to the square function. During operation, the suspension system adjusts the suspension force by adjusting the electromagnet current (i.e., the excitation current of the long stator linear motor) to ensure the constant suspension air gap. Due to the adjustment of the suspension controller, the air gap often does not change much, while the excitation current changes greatly. The change of the excitation current causes the excitation flux to change, which in turn affects the mutual induction flux between the stator winding and the excitation winding, which will inevitably cause the traction force to fluctuate.

[0005] The invention patent (CN110071677A) detects the air gap of each suspension control point of the maglev train, obtains the average air gap length, and then establishes a suspension system model to estimate the mutual inductance flux between the stator winding and the excitation winding of the long stator linear motor, and then applies the mutual inductance flux parameters to the external speed loop and the internal current loop, thereby effectively suppressing the traction force fluctuation caused by the suspension system. However, due to the complexity of the suspension control system model, involving multiple parameter changes and model uncertainty, the mutual inductance flux estimated by the suspension system model may have a large error and cannot effectively avoid traction force fluctuations. Summary of the invention

[0006] In order to overcome the technical defects that the existing suspension control system model is complex, the mutual inductance flux estimated by the suspension system model may have large errors, and the traction force fluctuation cannot be effectively avoided, the present invention provides a method for suppressing the traction force fluctuation of a magnetic levitation train. The method estimates the mutual inductance flux between the stator winding and the excitation winding of the motor in real time by observing the extended back electromotive force of the long-stator linear motor, and uses the flux parameters for the calculation of the q-axis current and the feedforward voltage, and adjusts the output voltage online, so that the traction force fluctuation caused by the suspension system can be effectively suppressed when the track is uneven, the load is disturbed, or there is external force interference in the vertical direction.

[0007] The present invention provides a method for suppressing traction fluctuation of a magnetic levitation train, wherein the position signal θ and the rotor angular velocity ω of a long stator linear motor are r Obtained by detecting the stator slots by the vehicle-mounted positioning and speed measurement system; according to the bus voltage u DC And the duty cycle S of the three-phase upper bridge arm switch tube abc Reconstruct the phase voltage u in the three-phase rotating coordinate system A 、u B 、u C , phase voltage u A 、u B 、u C After voltage transformation, the voltage u in the two-phase stationary coordinate system is obtained α 、u β , the feedback current i in the three-phase rotating coordinate system a 、i b After current transformation, the feedback current i in the two-phase stationary coordinate system is obtained respectively. α 、i β And the feedback current i in the two-phase rotating coordinate system d 、i q ; Extended back-EMF observer according to rotor angular velocity ω r , voltage u in the two-phase stationary coordinate system α 、u β The current i in the two-phase stationary coordinate system α 、i β, we get the component of the extended back electromotive force in the two-phase stationary coordinate system The flux estimation unit is constructed by expanding the components of the back electromotive force in the two-phase stationary coordinate system. and the rotor angular velocity ω r , get the estimated mutual inductance flux Speed ​​reference V ref and the rotor angular velocity ω r The converted speed V is adjusted by PI, and then the speed feedforward value is subtracted to obtain the reference value F of the traction force. ref ; From the reference value of traction F ref and the estimated mutual inductance flux Calculate the q-axis current reference value i q_ref ; To achieve decoupling control of traction and suspension force, i d = 0, that is, the d-axis current reference value i d_ref =0; the mutual inductance flux estimated by the feedforward voltage calculation unit q-axis current reference value i q_ref and the rotor angular velocity ω r The feedforward voltage u in the two-phase rotating coordinate system is calculated d_fwd and u q_fwd ;q-axis current reference value i q_ref With the q-axis feedback current i q The difference is adjusted by PI, and then the q-axis feedforward voltage u q_fwd , get the given voltage of q axis in two-phase rotating coordinate system D-axis current reference value i d_ref and the d-axis feedback current i d The difference is adjusted by PI, and then the d-axis feedforward voltage u d_fwd , get the given voltage of d axis in two-phase rotating coordinate system Given voltage in two-phase rotating coordinate system The coordinate transformation is performed through the position signal θ to obtain the given voltage in the two-phase stationary coordinate system. Given voltage After being processed by the PWM module and the inverter, it is used to control the operation of the long-stator linear motor in real time.

[0008] Compared with the prior art, the technical solution provided by the present invention has the following technical effects: by adopting the traction force fluctuation suppression method proposed in the present invention, the maglev train can ensure the smooth exertion of traction, reduce traction force fluctuations, and ensure the smooth operation of the vehicle when the track is uneven, the load is disturbed, or external forces in the vertical direction interfere. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 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.

[0010] 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.

[0011] Figure 1 A control block diagram of a method for suppressing traction force fluctuation of a magnetic levitation train according to an embodiment of the present invention;

[0012] Figure 2 It is a flow chart of a method for suppressing traction force fluctuation of a magnetic levitation train described in a certain embodiment of the present invention;

[0013] Figure 3 It is a schematic diagram of a suspension control device in the background technology of the present invention;

[0014] Figure 4 The component of the expanded back electromotive force in the two-phase stationary coordinate system in the method for suppressing the traction force fluctuation of a magnetic levitation train in a certain embodiment of the present invention is Schematic diagram of the calculation. DETAILED DESCRIPTION

[0015] 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.

[0016] In the description, it should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be understood as indicating or implying relative importance. It should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0017] 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.

[0018] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0019] In one embodiment, a method for suppressing traction fluctuation of a maglev train is disclosed, such as Figure 1 and Figure 2 As shown, the train suspension control device generates an excitation current i f To control the suspension height, the train is suspended 8 to 12 mm above the track, and the suspension control device can control the excitation current i f The size of the long stator linear motor position signal θ and rotor angular velocity ω r Obtained by detecting the stator slots by the vehicle-mounted positioning and speed measurement system; according to the bus voltage u DC And the duty cycle S of the three-phase upper bridge arm switch tube abc Reconstruct the phase voltage u in the three-phase rotating coordinate system A 、u B 、u C , phase voltage u A 、u B 、u C After voltage transformation, the voltage u in the two-phase stationary coordinate system is obtained α 、u β , the feedback current i in the three-phase rotating coordinate system a 、i b After current transformation, the feedback current i in the two-phase stationary coordinate system is obtained respectively. α 、i β And the feedback current i in the two-phase rotating coordinate system d 、i q ; Extended back-EMF observer according to rotor angular velocity ω r , voltage u in the two-phase stationary coordinate system α 、u β The current i in the two-phase stationary coordinate system α 、i β , we get the component of the extended back electromotive force in the two-phase stationary coordinate system The flux estimation unit is constructed by expanding the components of the back electromotive force in the two-phase stationary coordinate system. and the rotor angular velocity ω r , get the estimated mutual inductance flux Speed ​​reference V ref and the rotor angular velocity ω r The converted speed V is adjusted by PI, and then the speed feedforward value is subtracted to obtain the reference value F of the traction force. ref ; From the reference value of traction F ref and the estimated mutual inductance flux Calculate the q-axis current reference value i q_ref ; To achieve decoupling control of traction and suspension force, i d= 0, that is, the d-axis current reference value i d_ref =0; the mutual inductance flux estimated by the feedforward voltage calculation unit q-axis current reference value i q_ref and the rotor angular velocity ω r The feedforward voltage u in the two-phase rotating coordinate system is calculated d_fwd and u q_fwd ;q-axis current reference value i q_ref With the q-axis feedback current i q The difference is adjusted by PI, and then the q-axis feedforward voltage u q_fwd , get the given voltage of q axis in two-phase rotating coordinate system D-axis current reference value i d_ref and the d-axis feedback current i d The difference is adjusted by PI, and then the d-axis feedforward voltage u d_fwd , get the given voltage of d axis in two-phase rotating coordinate system Given voltage in two-phase rotating coordinate system The position signal θ is transformed into coordinates to obtain the voltage in the two-phase stationary coordinate system Voltage After being processed by the PWM module and the inverter, it is used to control the operation of the long-stator linear motor in real time.

[0020] Due to the calculation delay of the controller, the conduction delay of the switch device and other factors, 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. 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:

[0021]

[0022] Regarding the voltage and current transformation, the Clark transformation formula is used to transform the voltage u in the three-phase rotating coordinate system 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 、iβ The Clark transformation formulas for voltage and current are:

[0023]

[0024] The motor control also needs to use the current in the two-phase rotating coordinate system. The Park transformation formula is used 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 Park transformation formula of current is:

[0025]

[0026] The extended back EMF term contains flux information. d =0, and because the long stator linear synchronous motor has large leakage inductance and insignificant salient pole effect, the extended back EMF and back EMF have a slight difference in amplitude in the dynamic process, but there is no difference between the two in the steady state. Therefore, the mutual inductance flux can be calculated based on the observed extended back EMF.

[0027] The mathematical model of the long stator linear motor in the two-phase stationary coordinate system is:

[0028]

[0029] 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

[0030]

[0031] In the formula, E α and E β They are the components of the extended back electromotive force E on the α and β axes in the two-phase stationary coordinate system; obtained from the mathematical model of the long stator linear motor in the two-phase stationary coordinate system:

[0032]

[0033] In the formula, u α、u β 、i α 、i β They are obtained indirectly through measurement transformation and serve 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 expressed as the estimated value of the extended back-EMF through the PI regulator. The components of the extended back-EMF in the two-phase stationary coordinate system are: and like Figure 4 As shown, and The calculation formula is:

[0034]

[0035] in, is the estimated value of the current,

[0036]

[0037] Estimating mutual inductance flux by extending back EMF and motor speed The estimated mutual inductance flux is The calculation formula is:

[0038]

[0039] The speed loop can make the vehicle run according to the pre-set speed curve. Usually, the speed loop regulator is a PI regulator, and its output is the reference value F of the traction force. ref In order to make the speed response faster, a speed feedforward link is added to the speed loop, and the reference value of traction force is obtained together. The reference value of traction force F ref The calculation formula is:

[0040]

[0041] Adopt i d =0 control mode, that is, let i d_ref =0, the reference value of traction force F ref The calculation formula is:

[0042] In order to suppress the traction force fluctuation caused by the change of the excitation current of the suspension system, the mutual inductance flux is estimated. Real-time calculation of q-axis current reference value i q_ref for:

[0043]

[0044] In order to improve the dynamic response speed of the traction system, a feedforward voltage compensation link is added, and the feedforward voltage is calculated using the real-time estimated mutual inductance flux. The feedforward voltage u in the two-phase rotating coordinate system is d_fwd and u q_fwd The calculation formula is:

[0045]

[0046] q-axis current reference value i q_ref With the q-axis feedback current i q The difference is adjusted by PI, and then the q-axis feedforward voltage u q_fwd , get the given voltage of q axis in two-phase rotating coordinate system D-axis current reference value i d_ref and the d-axis feedback current i d The difference is adjusted by PI, and then the d-axis feedforward voltage u d_fwd , get the given voltage of d axis in two-phase rotating coordinate system

[0047] Given voltage in two-phase rotating coordinate system After the position signal θ is transformed, the given voltage in the two-phase stationary coordinate system is obtained Given voltage The PWM module modulates the wave, where PWM modulation includes but is not limited to SPWM modulation, SVPWM modulation, and SHEPWM modulation. The output modulated wave is used to control the inverter, thereby realizing the control of the long stator linear motor and effectively suppressing the traction fluctuation during the operation of the train.

[0048] 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 method for suppressing traction force fluctuation of a maglev train, characterized in that: Position signal θ and rotor angular velocity ω of a long stator linear motor r Obtained by detecting the stator slots by the vehicle-mounted positioning and speed measurement system; according to the bus voltage u DC And the duty cycle S of the three-phase upper bridge arm switch tube abc Reconstruct the phase voltage u in the three-phase rotating coordinate system A 、u B 、u C , phase voltage u A 、u B 、u C After voltage transformation, the voltage u in the two-phase stationary coordinate system is obtained α 、u β , the feedback current i in the three-phase rotating coordinate system a 、i b After current transformation, the feedback current i in the two-phase stationary coordinate system is obtained respectively. α 、i β And the feedback current i in the two-phase rotating coordinate system d 、i q ; Extended back-EMF observer according to rotor angular velocity ω r , voltage u in the two-phase stationary coordinate system α 、u β The current i in the two-phase stationary coordinate system α 、i β , we get the component of the extended back electromotive force in the two-phase stationary coordinate system The flux estimation unit is constructed by expanding the components of the back electromotive force in the two-phase stationary coordinate system. and the rotor angular velocity ω r , get the estimated mutual inductance flux Speed ​​reference V ref and the rotor angular velocity ω r The converted speed V is adjusted by PI, and then the speed feedforward value is subtracted to obtain the reference value F of the traction force. ref ; From the reference value of traction F ref and the estimated mutual inductance flux Calculate the q-axis current reference value i q_ref ; To achieve decoupling control of traction and suspension force, i d = 0, that is, the d-axis current reference value i d_ref =0; the mutual inductance flux estimated by the feedforward voltage calculation unit q-axis current reference value i q_ref and the rotor angular velocity ω r The feedforward voltage u in the two-phase rotating coordinate system is calculated d_fwd and u q_fwd ;q-axis current reference value i q_ref With the q-axis feedback current i q The difference is adjusted by PI, and then the q-axis feedforward voltage u q_fwd , get the given voltage of q axis in two-phase rotating coordinate system D-axis current reference value i d_ref and the d-axis feedback current i d The difference is adjusted by PI, and then the d-axis feedforward voltage u d_fwd , get the given voltage of d axis in two-phase rotating coordinate system Given voltage in two-phase rotating coordinate system After the position signal θ is transformed, the given voltage in the two-phase stationary coordinate system is obtained Given voltage After being processed by the PWM module and the inverter, it is used to control the operation of the long-stator linear motor in real time.

2. A method for suppressing traction force fluctuation of a maglev train according to claim 1, characterized in that: The extended back electromotive force of the long stator linear motor in the two-phase stationary coordinate system The calculation formula is: in, 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, L d , L q are the direct-axis and quadrature-axis inductances of the motor respectively, R is the stator phase winding resistance, ω r is the rotor angular velocity.

3. A method for suppressing traction force fluctuation of a maglev train according to claim 1, characterized in that: The mutual inductance flux estimation formula between the stator winding and the excitation winding of the long stator linear motor is: In the formula, is the extended back electromotive force of the long stator linear motor in the two-phase stationary coordinate system, ω r is the rotor angular velocity.

4. A method for suppressing traction force fluctuation of a maglev train according to claim 1, characterized in that: In order to suppress the traction force fluctuation caused by the change of the excitation current of the suspension system, the mutual inductance flux is estimated. Real-time calculation of q-axis current reference value i q_ref , the calculation formula is:

5. The method for suppressing traction force fluctuation of a maglev train according to claim 1, characterized in that: In order to improve the dynamic response speed of the traction system, a feedforward voltage compensation link is added, and the feedforward voltage is calculated using the real-time estimated mutual inductance flux. The feedforward voltage calculation formula in the two-phase rotating coordinate system is:

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