A method for suppressing traction force fluctuation of a maglev train

Abstract

The present application relates to the field of magnetic levitation train traction force control technology, and more particularly to a magnetic levitation train traction force fluctuation suppression method, which estimates the mutual inductance flux between the stator winding and the excitation winding in real time by observing the extended back electromotive force of the long stator linear motor, and uses the mutual inductance flux parameter in q The calculation of the shaft current and the feedforward voltage can effectively suppress the traction force fluctuation caused by the change of the suspension system excitation current. The mutual inductance flux parameter observed by the present application is used in the real-time control of the long stator linear motor traction system, which can effectively suppress the traction force fluctuation caused by the suspension system when the track is uneven, load disturbance occurs or vertical external force interference occurs.

Description

Technical Field

[0001] This invention relates to the field of traction control technology for maglev trains, and in particular to a method for suppressing traction fluctuations in maglev trains. Background Technology

[0002] Maglev trains are driven by long stator linear motors (LSLSMs). The primary stator core and three-phase armature windings of the LSLSM are mounted along the track, while the secondary (excitation pole) electromagnets are mounted on a suspension frame below the train body. The traveling wave magnetic field generated by the primary stator three-phase armature windings couples with the DC magnetic field of the secondary electromagnets to generate traction, propelling the train. The mutual attraction between the primary stator core and the secondary electromagnets generates levitation force, suspending the train 8–12 mm above the track.

[0003] Because the excitation poles of a long-stator linear motor also function as electromagnets that generate levitation force, a nonlinear coupling relationship exists between traction force and levitation force. Adjusting one variable (potential) will affect the other. To achieve decoupled control of traction force and levitation force, minimizing the impact of stator current changes on train levitation force, the motor often employs an i-type... d In the rotor field-oriented control mode with i=0, the armature reaction is minimized, and the coupling between the two is also minimized. This can be achieved by adjusting the stator current i. q The excitation current of the excitation poles controls the traction force and levitation force respectively, thereby enabling independent control of the traction system and the levitation system.

[0004] However, during actual train operation, fluctuations in the levitation air gap can occur due to factors such as uneven track surfaces, load disturbances, or vertical external forces. To maintain a constant levitation air gap, the levitation control system dynamically adjusts the excitation current, ensuring the air gap remains stable near its rated position. For example... Figure 3 As shown, the levitation control system of a maglev train mainly consists of: a power supply, a levitation controller, levitation sensors (gap sensor, current sensor, acceleration sensor), a chopper, and levitation electromagnets. The electromagnetic attraction force and the levitation gap have an inverse square relationship. During operation, the levitation system adjusts the levitation force by regulating the electromagnet current (i.e., the excitation current of the long stator linear motor), thereby ensuring a constant levitation air gap. Due to the adjustment of the levitation controller, the air gap often changes little, while the excitation current changes significantly. Changes in the excitation current cause changes in the excitation flux linkage, which in turn affects the mutual inductance flux linkage between the stator winding and the excitation winding, inevitably leading to fluctuations in the traction force.

[0005] The invention patent (CN110071677A) obtains the average air gap length by detecting the air gap of each suspension control point of the maglev train, then establishes a suspension system model, and further estimates 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, the mutual inductance flux estimated by the suspension system model may have a large error, and the fluctuation of the traction force cannot be effectively avoided. SUMMARY

[0006] To overcome the technical defects of the prior art that the suspension control system model is complex, the mutual inductance flux estimated by the suspension system model may have a large error, and the fluctuation of the traction force cannot be effectively avoided, the present application provides a maglev train traction force fluctuation suppression method. The method estimates the mutual inductance flux between the stator winding and the excitation winding of the long stator linear 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 q-axis current and 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 the vertical external force interference occurs.

[0007] The present application provides a maglev train traction force fluctuation suppression method, the position signal θ and the rotor angular velocity ω of the long stator linear motor r The stator tooth gap is detected by the vehicle-mounted positioning and speed measurement system; the bus voltage u DC And the duty cycle S of the three-phase upper bridge arm switch tube abc The phase voltage u A , u B , u C In the three-phase rotating coordinate system is reconstructed, the phase voltage u A , u B , u C After voltage transformation, the voltage u α , u β In the two-phase stationary coordinate system is obtained, the feedback current i a , i b In the three-phase rotating coordinate system is transformed to obtain the feedback current i α , i β In the two-phase stationary coordinate system and the feedback current i d , i q In the two-phase rotating coordinate system; the extended back electromotive force observer is based on the rotor angular velocity ω r , the voltage u α , u β In the two-phase stationary coordinate system and the current i α , i βThe components of the extended back electromotive force in the two-phase stationary coordinate system are obtained. The flux linkage estimation unit expands the components of the back electromotive force in the two-phase stationary coordinate system. and rotor angular velocity ω r The estimated mutual inductance flux was obtained. Speed ​​Reference V ref With the rotor angular velocity ω r The converted velocity V is adjusted by a PI controller, and then the velocity feedforward value is subtracted to obtain the reference value F of the traction force. ref ;Based on the reference value F of the traction force ref and estimated mutual inductance flux The q-axis current reference value i is calculated. q_ref To achieve decoupled control of traction and suspension, i d Rotor field-oriented control mode with 0 = , that is, setting the d-axis current reference value i d_ref =0; the mutual inductance flux estimated by the feedforward voltage calculation unit is 0. q-axis current reference value i q_ref and 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 q-axis feedback current i q The difference is adjusted by a PI controller, and then the q-axis feedforward voltage u is added. q_fwd The given voltage along the q-axis in the two-phase rotating coordinate system is obtained. d-axis current reference value i d_ref With d-axis feedback current i d The difference is adjusted by a PI controller, and then the d-axis feedforward voltage u is added. d_fwd The given voltage along the d-axis in the two-phase rotating coordinate system is obtained. Given voltage in a two-phase rotating coordinate system The given voltage in the two-phase stationary coordinate system is obtained by performing coordinate transformation on the position signal θ. Given voltage After processing by the PWM module and inverter, it is used for real-time control of the long stator linear motor.

[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 stable performance of traction force, reduce traction force fluctuation, and ensure the smooth operation of the vehicle when affected by uneven track, load disturbance or vertical external force interference. Attached Figure Description

[0009] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced hereinafter. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0011] Figure 1 The control block diagram of the magnetic levitation train traction force fluctuation suppression method in some embodiments of the present application;

[0012] Figure 2 The flow chart of the magnetic levitation train traction force fluctuation suppression method in some embodiments of the present application;

[0013] Figure 3 The schematic diagram of the levitation control device in the background art;

[0014] Figure 4 The calculation schematic diagram of the component of the extended counter electromotive force in the two-phase stationary coordinate system in the magnetic levitation train traction force fluctuation suppression method in some embodiments of the present application The calculation schematic diagram of the component of the extended counter electromotive force in the two-phase stationary coordinate system in the magnetic levitation train traction force fluctuation suppression method in some embodiments of the present application DETAILED DESCRIPTION

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced hereinafter. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0016] In the description, it should be noted that the terms "first", "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 explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0017] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein; obviously, the examples in the specification are only some of the embodiments of the present application, not all the embodiments.

[0018] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] In one embodiment, a method for suppressing traction force fluctuations in a magnetic levitation train is disclosed, such as... Figure 1 and Figure 2 As shown, the train levitation control device generates an excitation current i f This controls the levitation height, keeping the train suspended 8-12mm above the track. Furthermore, the levitation control device can control the excitation current. f The size of the long stator linear motor, the position signal θ and the rotor angular velocity ω r The information is obtained by detecting the stator slots using an onboard positioning and speed measurement system; based on the bus voltage u. DC Duty cycle S of the three-phase upper bridge arm switch 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 Feedback current i in a 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 a two-phase rotating coordinate system d i q The extended back EMF observer is based on the rotor angular velocity ω. r Voltage u in a two-phase stationary coordinate system α u β Current i in a two-phase stationary coordinate system α i β The components of the extended back electromotive force in the two-phase stationary coordinate system are obtained. The flux linkage estimation unit expands the components of the back electromotive force in the two-phase stationary coordinate system. and rotor angular velocity ω r The estimated mutual inductance flux was obtained. Speed ​​Reference V ref With the rotor angular velocity ω r The converted velocity V is adjusted by a PI controller, and then the velocity feedforward value is subtracted to obtain the reference value F of the traction force. ref ;Based on the reference value F of the traction force ref and estimated mutual inductance flux The q-axis current reference value i is calculated. q_ref To achieve decoupled control of traction and suspension, i dThe rotor field-oriented control mode with a value of 0, i.e., setting the d-axis current reference value i... d_ref =0; the mutual inductance flux estimated by the feedforward voltage calculation unit is 0. q-axis current reference value i q_ref and 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 q-axis feedback current i q The difference is adjusted by a PI controller, and then the q-axis feedforward voltage u is added. q_fwd The given voltage along the q-axis in the two-phase rotating coordinate system is obtained. d-axis current reference value i d_ref With d-axis feedback current i d The difference is adjusted by a PI controller, and then the d-axis feedforward voltage u is added. d_fwd The given voltage along the d-axis in the two-phase rotating coordinate system is obtained. Given voltage in a two-phase rotating coordinate system The voltage in the two-phase stationary coordinate system is obtained by performing coordinate transformation on the position signal θ. Voltage After processing by the PWM module and inverter, it is used for real-time control of the long stator linear motor.

[0020] Due to factors such as the controller's calculation delay and the switching device's turn-on delay, the controller's voltage command may have a certain error compared to the voltage at the terminals of the long stator linear motor. To measure the motor voltage more accurately, it is necessary to calculate the voltage of each phase of the motor using the bus voltage and the duty cycle of the switching transistors. Specifically, the bus voltage u... DC Duty cycle S of the three-phase upper bridge arm switch abc During voltage reconstruction, the phase voltage u in the three-phase rotating coordinate system A u B u C The calculation formula is:

[0021]

[0022] Regarding voltage and current transformation, the Clark transformation formula is used to transform the voltage u in a three-phase rotating coordinate system. A u B u C Voltage u converted to a two-phase stationary coordinate system α u β Using the Clark transformation formula, the current i in the three-phase rotating coordinate system is... a i b Converted to current i in a two-phase stationary coordinate system α iβ The Clark transformation formulae of voltage and current are respectively:

[0023]

[0024] In motor control, the current in two-phase rotating coordinate system is also needed, and the Park transformation formula is used to convert the current i α , i β in two-phase static coordinate system into the current i d , i q in two-phase rotating coordinate system, and the Park transformation formula of current is:

[0025]

[0026] The extended back electromotive force item contains the flux linkage information. Since the rotor flux orientation control method with i d =0 is adopted, and since the leakage inductance of long-stator linear synchronous motor is large and the saliency effect is not obvious, the extended back electromotive force and the back electromotive force are slightly different in amplitude in dynamic process, but there is no difference between them in steady state, so the mutual flux linkage can be calculated according to the observed extended back electromotive force.

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

[0028]

[0029] In the formula, L d , L q are the direct-axis and quadrature-axis inductances of the motor; R is the resistance of the stator winding; 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 ; wherein, contains position information, and it is defined as the extended back electromotive force item, then

[0030]

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

[0032]

[0033] In the formula, u αu β i α i β These values ​​are indirectly obtained through measurement transformation and serve as inputs to the extended back EMF observer. Since the extended back EMF term cannot be measured, the difference between the measured and estimated current values ​​is used, and then a PI controller is applied to represent the estimated extended back EMF value. 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, This is an estimated value for the current.

[0036]

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

[0038]

[0039] The speed loop allows the vehicle to operate according to a pre-set speed curve. Typically, the speed loop regulator is a PI regulator, and its output is the reference value F of the traction force. ref To achieve faster speed response, a speed feedforward element is added to the speed loop, working together to obtain the reference value of traction force F. ref The calculation formula is:

[0040]

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

[0042] To suppress traction force fluctuations caused by changes in the excitation current of the suspension system, based on the estimated mutual inductance flux... Real-time calculation of q-axis current reference value i q_ref for:

[0043]

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

[0045]

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

[0047] The given voltage u in the two-phase rotating coordinate system is transformed by the position signal θ to obtain the given voltage u in the two-phase stationary coordinate system. The given voltage u is modulated by a PWM module to generate a wave, and the PWM modulation herein 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 force fluctuation in the train running process.

[0048] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Although the foregoing embodiments are described in detail, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced 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 in the protection scope of the claims.

Claims

1. A method of suppressing fluctuation in traction force of a magnetic levitation train, characterized by, Position signal θ and rotor angular velocity ω of a long stator linear motor r The information is obtained by detecting the stator slots using an onboard positioning and speed measurement system; based on the bus voltage u. DC Duty cycle S of the three-phase upper bridge arm switch 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 Feedback current i in a 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 a two-phase rotating coordinate system d i q The extended back EMF observer is based on the rotor angular velocity ω. r Voltage u in a two-phase stationary coordinate system α u β Current i in a two-phase stationary coordinate system α i β The components of the extended back electromotive force in the two-phase stationary coordinate system are obtained. The flux linkage estimation unit expands the components of the back electromotive force in the two-phase stationary coordinate system. and rotor angular velocity ω r The estimated mutual inductance flux was obtained. Speed ​​Reference V ref With the rotor angular velocity ω r The converted velocity V is adjusted by a PI controller, and then the velocity feedforward value is subtracted to obtain the reference value F of the traction force. ref ;Based on the reference value F of the traction force ref and estimated mutual inductance flux The q-axis current reference value i is calculated. q_ref To achieve decoupled control of traction and suspension, i d Rotor field-oriented control mode with 0 = , that is, setting the d-axis current reference value i d_ref =0; the mutual inductance flux estimated by the feedforward voltage calculation unit is 0. q-axis current reference value i q_ref and 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 q-axis feedback current i q The difference between the d-axis current reference value id and the d-axis feedback current id is adjusted by PI, plus the d-axis feedforward voltage ud, to obtain the given voltage on the d-axis in the two-phase rotating coordinate system q_fwd The difference between the d-axis current reference value id and the d-axis feedback current id is adjusted by PI, plus the d-axis feedforward voltage ud, to obtain the given voltage on the d-axis in the two-phase rotating coordinate system d_ref d The difference between the d-axis current reference value id and the d-axis feedback current id is adjusted by PI, plus the d-axis feedforward voltage ud, to obtain the given voltage on the d-axis in the two-phase rotating coordinate system d_fwd The given voltage in the two-phase rotating coordinate system The given voltage in the two-phase rotating coordinate system is transformed by the position signal θ to obtain the given voltage in the two-phase stationary coordinate system The given voltage After being processed by the PWM module and the inverter, the given voltage is used to control the long-stator linear motor in real time.​​​ 2. The method of claim 1, wherein the method is characterized by: The long-stator linear motor in two-phase stationary coordinate system under the extended back electromotive force The calculation formula is: wherein, wherein, u α , u β is the given voltage in two-phase stationary coordinate system, i α , i β is the actual value of current in two-phase stationary coordinate system, is the estimated value of current in two-phase stationary coordinate system, L d , L q are the direct and quadrature axis inductances of the machine, respectively, R is the stator phase winding resistance, and ω r is the rotor angular speed.

3. The method of claim 1, wherein the method is characterized by, The mutual inductance flux linkage estimation formula between the long stator linear motor stator winding and the excitation winding is: wherein is the extended back EMF of the long-stator linear motor in the two-phase stationary coordinate system, ω r is the rotor angular velocity.

4. The method of claim 1, wherein the method is characterized by: In order to suppress the traction force fluctuation caused by the change of the suspension system excitation current, the estimated mutual inductance magnetic chain The q-axis current reference value i is calculated in real time q_ref The calculation formula is:

5. The method of claim 1, wherein the method is characterized by: In order to improve the dynamic response speed of the traction system, a feedforward voltage compensation link is added, and the mutual inductance flux linkage estimated in real time is used to calculate the feedforward voltage. The feedforward voltage calculation formula in the two-phase rotating coordinate system is:

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