A dual-frequency magnetic field combination control method and device for a double-fed linear motor

Abstract

The present application relates to a kind of double-frequency magnetic field combination control method and equipment of double-fed linear motor, the control method is realized by generating two different frequency power supply current in secondary power supply combination control of double-fed linear motor under limit working condition, this control method includes the following steps: control the primary power supply current of motor, the first frequency component of secondary power supply current respectively generates spatially synchronous primary magnetic field and secondary first magnetic field in air gap, while, control the second frequency component of secondary power supply current of motor generates additional secondary second magnetic field in air gap;By controlling the size and relative position of the primary magnetic field and secondary first magnetic field, and the size of the secondary second magnetic field, the stable operation of double-fed linear motor is realized.Compared with prior art, the present application has the advantages of enabling double-fed linear motor to operate stably, strong working condition adaptability and the like.

Description

Technical Field

[0001] This invention belongs to the field of motor and control technology, and in particular relates to a method and device for combined control of dual-frequency magnetic fields of a doubly fed linear motor. Background Technology

[0002] Linear motors can serve as the core drive component of rail transit, and are of great significance to the development of the transportation sector. Among them, doubly-fed linear motors can simultaneously achieve traction, levitation, and secondary contactless power supply functions, and their application in rail transit has enormous potential.

[0003] In the control of a doubly-fed linear motor, the primary and secondary magnetic fields need to be synchronized in space. This means the frequency of the primary traveling wave magnetic field and the frequency of the secondary magnetic field (including the superposition of the secondary power supply winding's own movement and the secondary power supply frequency) must be equal. Therefore, a single-frequency synthetic traveling wave magnetic field is generated between the primary and secondary fields, ensuring the doubly-fed linear motor's traction, levitation, and contactless power supply. Currently known control strategies for long-stator doubly-fed linear motors all rely on the spatial synchronization of the primary and secondary magnetic fields as their control basis. For example,

[0004] (1) A relevant literature (DOI:10.1016 / S0967-0661(02)00039-4) introduces a doubly fed linear motor control method. This method transmits the current angle, motion speed information, and position information of the secondary motor to the primary motor control in real time through a wireless communication channel, and introduces synchronization units on both the primary and secondary motor sides to achieve spatial synchronization of the primary and secondary magnetic fields. It requires real-time transmission of the state information between the stator and the motor, and the data exchange between the stator and the motor is too demanding and has high timing requirements.

[0005] (2) The invention patent application 202110639986.7 describes a power supply control method for a long stator doubly fed linear motor. The primary side power supply control is based on the external operating speed requirements. The primary side power supply frequency is adjusted to complete the primary side speed closed-loop control. The secondary side power supply achieves spatial synchronization between the secondary magnetic field and the primary magnetic field by detecting the primary side magnetic field.

[0006] (3) The invention patent application 202210079904.2 and related documents (DOI:10.1109 / TTE.2022.3187608) both introduce a quasi-synchronous operation control method for a long stator doubly fed linear motor. The method adopts scalar control on the primary side, and its current amplitude and frequency are set by the secondary side through wireless communication; on the secondary side, vector control is adopted, and the secondary side realizes the synchronization of the secondary magnetic field with the primary magnetic field in space by detecting or estimating the relative stator position.

[0007] The existing quasi-synchronous operation control methods can meet the normal operating conditions of doubly fed linear motors and realize the reliable operation of doubly fed linear motors in traction, suspension, and non-contact power supply.

[0008] For doubly-fed linear motors, the voltage required for the secondary winding is positively correlated with the slip frequency, necessitating a certain secondary inverter bus voltage to balance the induced electromotive force (EMF) in the secondary winding. However, the secondary inverter bus voltage is limited in applications where the secondary winding is typically used in the moving part (carriage) of rail transit, where the bus voltage is constrained by the energy storage system. This means that under certain special or extreme conditions, such as primary magnetic field frequency misalignment or instantaneous deceleration of the secondary winding, a higher slip frequency may occur, potentially leading to excessively high induced EMF. In such cases, the secondary inverter bus voltage will be insufficient to balance the induced EMF and maintain sufficient AC excitation current for reliable operation of the doubly-fed linear motor's traction, levitation, and contactless power supply. Therefore, under certain special or extreme conditions, a single magnetic field control method that spatially synchronizes the primary and secondary magnetic fields cannot meet the application requirements of doubly-fed linear motors.

[0009] In summary, current control methods cannot solve the problems caused by excessively high slip frequency in doubly fed linear motors under certain special or extreme operating conditions. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a dual-frequency magnetic field combination control method and device for doubly fed linear motors that is highly flexible and suitable for extreme operating conditions.

[0011] The objective of this invention can be achieved through the following technical solutions:

[0012] A dual-frequency magnetic field combination control method for a doubly-fed linear motor is characterized by achieving combined control of the doubly-fed linear motor under extreme operating conditions by generating two supply currents of different frequencies in the secondary power supply. The two supply currents of different frequencies are respectively denoted as the first frequency component and the second frequency component of the secondary power supply current. The control method includes the following steps:

[0013] The primary power supply current and the first frequency component of the secondary power supply current of the motor generate a spatially synchronized primary magnetic field and a secondary first magnetic field in the air gap, respectively. At the same time, the second frequency component of the secondary power supply current of the motor generates an additional secondary second magnetic field in the air gap.

[0014] Stable operation of the doubly fed linear motor is achieved by controlling the magnitude and relative position of the primary magnetic field and the first secondary magnetic field, as well as the magnitude of the second secondary magnetic field.

[0015] Furthermore, the secondary second magnetic field is stationary relative to the secondary winding.

[0016] Furthermore, the control of the magnitude and relative position of the primary magnetic field and the secondary first magnetic field specifically involves:

[0017] The first frequency component of the secondary power supply current that generates the secondary first magnetic field is set to have components on the M and T coordinate axes. The magnitudes of the M-axis current component and the T-axis current component are controlled to partially or completely cancel the primary magnetic field, thereby realizing field weakening control and traction control. The M-axis current component is used for field weakening control, and the T-axis current component is used for traction control.

[0018] Furthermore, the control of the magnitude of the secondary magnetic field is specifically as follows:

[0019] By coordinating the control of the secondary first magnetic field and the secondary second magnetic field, the magnitude and fluctuation of the normal force of the doubly fed linear motor can be controlled, thus maintaining a constant normal force of the doubly fed linear motor.

[0020] Furthermore, the coordination control specifically includes:

[0021] The magnitude of the normal force is adjusted by the amplitude of the second frequency component of the secondary power supply current;

[0022] The components of the first frequency component of the secondary power supply current that generates the secondary first magnetic field are set on the M and T coordinate axes. The fluctuation of the normal force is adjusted by coordinating the three components: the M-axis current component of the first frequency component of the secondary power supply current, the T-axis current component of the first frequency component of the secondary power supply current, and the second frequency component of the secondary power supply current.

[0023] Furthermore, in multiple unit motors, the traction force fluctuations are mutually canceled out by directional control of the secondary magnetic field of different unit motors.

[0024] Furthermore, the directional control of the secondary magnetic field specifically involves:

[0025] The initial phase α of the current required for the second magnetic field of the adjacent unit motor is set at an angle that is out of phase.

[0026] Furthermore, the set angle is 60°, 120°, or 180°.

[0027] Furthermore, the extreme operating conditions include frequency misalignment of the primary magnetic field or instantaneous deceleration of the secondary winding.

[0028] The present invention also provides a computer-readable storage medium including one or more programs executable by one or more processors of a control device, the one or more programs including instructions for performing the doubly fed linear motor dual-frequency magnetic field combination control method as described above.

[0029] The present invention also provides a control device, including one or more processors, a memory, and one or more programs stored in the memory, said one or more programs including instructions for executing the doubly fed linear motor dual-frequency magnetic field combination control method as described above.

[0030] Compared with existing technologies, this invention innovatively proposes a dual-frequency magnetic field combined control method, which solves the problem that a single magnetic field control method with primary and secondary synchronization cannot meet the application requirements of doubly-fed linear motors under certain special or extreme working conditions. Its beneficial effects in engineering applications are as follows:

[0031] 1) The amplitude and fluctuation of the normal force of the doubly fed linear motor can be adjusted by the coordinated control between the dual-frequency magnetic fields. This is a crucial basic function for applications such as magnetic levitation. In extreme working conditions, the present invention adopts dual-frequency control. The first magnetic field can still flexibly control the traction force even in the case of weak magnetic field. The normal force is controlled by the cooperation of the first magnetic field and the second magnetic field.

[0032] 2) When the secondary inverter bus voltage is limited, the induced electromotive force caused by the synthetic magnetic field in the secondary winding can be suppressed by the field weakening control of the secondary first magnetic field, thereby solving the problem of insufficient power supply to the secondary winding caused by excessive slip frequency and expanding the adaptability of the "quasi-synchronous operation" mentioned in relevant literature.

[0033] 3) The product of the orthogonal components of the secondary first magnetic field and the primary magnetic field can be flexibly adjusted to control the traction force of the doubly fed linear motor, thereby controlling the output mechanical power and the secondary power supply.

[0034] 4) The initial phase of the secondary magnetic field and the primary magnetic field can be flexibly adjusted, and the traction fluctuations in multiple unit motors are mutually canceled, ensuring the smoothness of the overall traction of the train. Attached Figure Description

[0035] Figure 1 This illustrates the working principle of the dual-frequency magnetic field combination control of the doubly fed linear motor in the MT coordinate system in the embodiment.

[0036] Figure 2 The example shown is a finite element model of a doubly fed linear motor.

[0037] Figure 3 The following are the finite element simulation results of constant normal force in the embodiments, where (3a) is a schematic diagram of normal force fluctuation controlled by dual-frequency magnetic field combination, (3b) is the result of applying weak magnetic control, and (3c) is the result of not applying weak magnetic control.

[0038] Figure 4The following are the finite element simulation results of the pure gliding process controlled by the dual-frequency magnetic field combination in the embodiment. Among them, (4a) shows the results of the pure gliding process controlled by the dual-frequency magnetic field combination in i. t1 =0A uses the simulation results of two unit motors with 180° phase shift, (4b) is the synthesized average traction force;

[0039] Figure 5 The following are the finite element simulation results of the dual-frequency magnetic field combination control drive process in the embodiment, wherein (5a) shows the results of the dual-frequency magnetic field combination control drive process in i t1 =-14.14A The simulation results of two unit motors with 180° phase misalignment are used, and (5b) is the synthesized average traction force;

[0040] Figure 6 The following are the finite element simulation results of the dual-frequency magnetic field combined control braking process in the embodiment. Among them, (6a) shows the results of the braking process in i t1 =14.14A The simulation results of two unit motors with 180° phase shift are used, and (6b) is the synthesized average traction force. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0042] This invention innovatively proposes a dual-frequency magnetic field combination control method for a doubly-fed linear motor. This method achieves combined control of the doubly-fed linear motor under extreme operating conditions by generating two different frequency supply currents in the secondary power supply. The two different frequency supply currents are denoted as the first frequency component and the second frequency component of the secondary power supply current, respectively. Specifically, the control method includes the following steps: controlling the primary power supply current and the first frequency component of the secondary power supply current to generate spatially synchronized primary and secondary first magnetic fields in the air gap, respectively; simultaneously, controlling the second frequency component of the secondary power supply current to generate an additional, relatively stationary secondary second magnetic field in the air gap; and achieving stable operation of the doubly-fed linear motor by controlling the magnitude and relative position of the primary and secondary first magnetic fields, as well as the magnitude of the secondary second magnetic field. This method utilizes the fact that the secondary first magnetic field can still flexibly control the traction force even under weak magnetic conditions, and achieves normal force control through the cooperation of the secondary first and secondary second magnetic fields. This method achieves motor control based on the primary magnetic field and the first secondary magnetic field under normal operating conditions. Under special or extreme operating conditions and when the slip frequency is too high, a second secondary magnetic field is introduced to solve the problem of insufficient power supply voltage to the secondary winding caused by the excessive slip frequency, thus ensuring the smoothness of the overall traction of the train.

[0043] The control of the magnitude and relative position of the primary magnetic field and the secondary first magnetic field is specifically as follows: the first frequency component of the secondary power supply current that generates the secondary first magnetic field is set to have components on the M and T coordinate axes, and the magnitudes of the M-axis current component and the T-axis current component are controlled respectively to partially or completely cancel the primary magnetic field, thereby realizing field weakening control and traction control. The M-axis current component is used for field weakening control, and the T-axis current component is used for traction control.

[0044] The control of the magnitude of the secondary magnetic field is specifically achieved by coordinating the control of the secondary first magnetic field and the secondary second magnetic field to control the magnitude and fluctuation of the normal force of the doubly-fed linear motor, thereby maintaining a constant normal force. Specifically, the coordinated control involves adjusting the magnitude of the normal force by adjusting the amplitude of the second frequency component of the secondary power supply current; setting the M-axis and T-axis components of the first frequency component of the secondary power supply current that generates the secondary first magnetic field; and coordinating the fluctuation of the normal force by adjusting the M-axis current component, the T-axis current component, and the second frequency component of the secondary power supply current.

[0045] The principle of this control method is as follows: Figure 1 As shown, its controlled object includes the primary current i s The first frequency component of the secondary supply current i r Secondary supply current second frequency component I rdc The primary current i s The primary magnetic field is generated, and the first frequency component i of the secondary power supply current is generated. r Generates a secondary first magnetic field synchronized with the primary magnetic field; the second frequency component I of the secondary power supply current. rdc A secondary second magnetic field is generated that is stationary relative to the secondary winding. Since the magnetic field of a doubly-fed linear motor is directly generated by current, in this invention, the generation of the magnetic field is directly represented by current.

[0046] In practical applications, the primary winding of a doubly-fed linear motor serves as the stator and is fixed to the ground; the secondary winding, as the moving part, is typically fixed to the train in rail transit. Because the secondary winding is the moving part, it possesses a certain velocity relative to the ground, denoted as V. m In a doubly fed linear motor, the corresponding angular frequency is ω. r And there are

[0047]

[0048] Where τ p This represents the polar distance.

[0049] exist Figure 1 In the middle, the current that generates the primary magnetic field is i sThis will generate a traveling wave magnetic field, the frequency of which is relative to the earth and denoted as ω. s The current that generates the secondary magnetic field is i. r The magnetic field generated by this current is synchronized with the primary magnetic field, meaning the frequency of the secondary magnetic field relative to the ground is also ω. s The angular frequency of the "secondary first magnetic field" in the secondary winding coordinate system is ω. f (i.e., slip frequency), and the following relationship is satisfied between each frequency:

[0050] ω s =ω r +ω f

[0051] This is manifested in the fact that the two traveling wave magnetic fields, the "primary magnetic field" and the "secondary first magnetic field", have the same frequency of motion in space, which means that the "secondary first magnetic field" and the "primary magnetic field" are synchronous magnetic fields.

[0052] To facilitate the mathematical analysis of the doubly-fed linear motor, a motion MT coordinate system with the same frequency as the synchronous magnetic field can be introduced. The angular frequency of this coordinate system is ω. s Therefore, in the MT coordinate system, the primary magnetic field and the current i that generates the primary magnetic field... s Secondary first magnetic field, current i that generates the secondary first magnetic field r It is stationary relative to the MT coordinate system itself. Taking the direction of the primary current as the positive direction of the M-axis, and the direction leading the M-axis by 90 degrees as the positive direction of the T-axis, the current i that generates the primary magnetic field... s The amplitude is i M This, in turn, generates a current i in the secondary primary magnetic field. r It can be decomposed into i on the M and T coordinate axes respectively. m1 and i t1 Because the MT coordinate system and the current i that generates the primary magnetic field... s The current i that generates the secondary primary magnetic field r Relative to stillness, i M i m1 and i t1 It is a direct current.

[0053] Consider the voltage equation for the generation of the first secondary magnetic field on the secondary side of a doubly fed linear motor.

[0054]

[0055] Where u m1 and u t1 These are the voltages in the MT coordinate system that provide the current required to supply the secondary first magnetic field, R and R. r L is the resistance of the secondary winding. r L is the self-inductance of the secondary winding.m Let be the mutual inductance between the primary and secondary windings. Considering steady-state operation and neglecting the resistance term, the steady-state mover voltage amplitude is .

[0056]

[0057] It can be seen that the required current i for a doubly fed linear motor to maintain its position is... m1 and i t1 Therefore, a certain secondary inverter bus voltage needs to be provided to balance the slip frequency ω. f Induced electromotive force.

[0058] On the other hand, the traction force and normal force generated by the secondary first magnetic field of the doubly fed linear motor are as follows:

[0059]

[0060] Where F x and F z These are the traction force and normal force, respectively. κ is the turns ratio of the primary and secondary windings, and δ is the air gap between the primary and secondary windings. Equation (3) reflects the traction force F of the doubly fed linear motor. x This represents the product of the orthogonal components of the secondary magnetic field and the primary magnetic field. For example... Figure 1 As shown, the primary M-axis current that generates the primary magnetic field is i M , with the primary M-axis current i M Orthogonal T-axis current i t1 i is the first frequency component of the secondary supply current. r With primary M-axis current i M The orthogonal components. The primary current i that generates the primary magnetic field. M The secondary first frequency component that generates the secondary first magnetic field is the orthogonal component i of the supply current and the primary current. t1 Each as Figure 1 As shown. Furthermore, in the absence of the second frequency component I of the secondary supply current. rdc Introduced, and the primary supply current i M Under fixed conditions, for the same electromagnetic force requirement, the current i in the secondary primary magnetic field is... r The choice (or i) m1 and i t1 The numerical value is unique.

[0061] Under certain special or extreme operating conditions, such as frequency misalignment of the primary magnetic field or instantaneous deceleration of the secondary winding, a higher slip frequency ω may occur. fAccording to equation (2), the slip frequency may cause a very high induced electromotive force, and the bus voltage of the secondary inverter may not be able to provide sufficient AC excitation current to meet the requirements of the traction force and normal force of the doubly fed linear motor in equation (3). In magnetic levitation applications, the normal force of the doubly fed linear motor plays the role of levitation force and is of vital importance. In order to address the problem that the normal force and traction force of the doubly fed linear motor cannot be maintained under certain special or extreme working conditions, this invention innovatively proposes to introduce a secondary second magnetic field into the secondary winding.

[0062] The secondary magnetic field is generated by the second frequency component I of the secondary power supply current. rdc The generation of the second frequency component of the secondary power supply current is discussed. In principle, the supply frequency of the second frequency component of the secondary power supply current can be selected in several ways: it can be lower than the first frequency, higher than the first frequency, or even a negative sequence supply frequency. To reduce the complexity of the doubly-fed linear motor control system, a simplified method for generating the second frequency component I of the secondary power supply current is proposed. rdc The selection method is to use a DC power supply that is relatively stationary compared to the secondary winding, such as... Figure 1 As shown. Due to the current I that generates the secondary magnetic field. rdc While stationary relative to the secondary winding, it undergoes an equivalent counterclockwise rotational motion in the MT coordinate system, with a relative angular frequency of -ω. f Its angle θ with the M-axis fdc It can be represented as

[0063] θ fdc =∫-ω f dt+α(4) where α is the initial phase angle. Similarly, the current I that generates the secondary magnetic field is... rdc It can also be decomposed into i in the MT coordinate system. m2 and i t2 i m2 and i t2 Let be the alternating current variation over time in the MT coordinate system.

[0064]

[0065] For the secondary winding, under steady-state conditions, only a low DC voltage component is needed to generate the current I required to produce the secondary magnetic field. rdc ,Right now

[0066] U rdc =I rdc R r (6)

[0067] Among them U rdc This is the DC voltage component required for the secondary winding, which, in steady state, only needs to overcome the voltage drop across the resistor.

[0068] After introducing the secondary magnetic field, the equations for the traction force and normal force of the doubly-fed linear motor are further expressed as follows:

[0069]

[0070] It can be seen that by introducing the DC component of the secondary supply current... rdc (Secondary magnetic field) increases the degree of freedom in adjusting the traction and normal forces of the doubly-fed linear motor. At this time, the traction force of the doubly-fed linear motor... x This represents the product of the orthogonal components of the primary magnetic field and the secondary first magnetic field after the secondary second magnetic field is superimposed. Comparing this with equation (3), it shows that under the same electromagnetic force requirement, especially the same levitation force requirement, the DC component I of the secondary power supply current... rdc The introduction of this technology allows for more flexible selection and adjustment of the current i in the secondary first magnetic field. r , or i m1 and i t1 The value.

[0071] Therefore, under special or extreme operating conditions, such as when a high slip frequency is induced, the secondary first magnetic field current i r (or i) m1 and i t1 If the value of the current cannot be maintained, the DC component I of the secondary supply current is introduced. rdc (Secondary magnetic field) can still maintain the electromagnetic force required, especially the constant levitation force. Furthermore, due to the DC component I of the secondary power supply current... rdc To help meet the requirements of electromagnetic force or maintain a constant levitation force, i can be appropriately reduced under special or extreme working conditions. m1 and i t1 The value is to satisfy the voltage requirements in equations (1) and (2); or other methods, such as field weakening control design, are used to satisfy the voltage requirements in equations (1) and (2).

[0072] The principle of field weakening control design is based on the current i on the M-axis. m1 It can be used to partially or completely cancel the primary magnetic field, weaken the combined magnetic field of the two, and thus suppress the induced electromotive force caused by the combined magnetic field in the secondary winding. That is, it can... m1 Set to

[0073] i m1 =-Ki M (8)

[0074] Where K > 0. It can be seen that i m1 Design offset (2) where (L) m i M +Lr i m1 The magnitude of the term () is adjusted to suppress the induced electromotive force caused by slip in equation (2), thereby achieving the purpose of weakening the magnetism. m1 Its weak magnetic function can also be used Figure 1 This is further reflected on the M-axis. The main purpose of field weakening control is to make ω in voltage equations (1) and (2) f (L m i M +L r i m1 The value of ) should be as small as possible to reduce the voltage amplitude.

[0075] According to equation (7), the current i on the T-axis is... t1 It is mainly used to control the magnitude of the average traction force of a doubly fed linear motor, while I rdc sin(θ fdc The term will cause a fluctuating traction force with an average force of 0. From the traction force equation (7), it can be seen that the average value of the traction force is still the product of the orthogonal components of the secondary first magnetic field and the primary magnetic field, such as... Figure 1 As shown. Through current i t1 The control can achieve traction force adjustment, and further control the output mechanical power and secondary power of the doubly fed linear motor. The mechanical power equation P... m and secondary feed power equation P er It can be represented as

[0076]

[0077] In a doubly fed linear motor, it is possible to further utilize ω f Design adjustment of secondary feed power P er If the slip frequency is set to

[0078] If the above methods are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0079] In another embodiment, a control device is also provided, including one or more processors, a memory, and one or more programs stored in the memory, the one or more programs including instructions for executing the doubly fed linear motor dual-frequency magnetic field combination control method as described above.

[0080] Application Example 1:

[0081] Based on the aforementioned analysis, this application example focuses on how to maintain a constant normal force in a doubly fed linear motor by controlling the field weakening of the primary magnetic field and coordinating the control of the secondary first magnetic field. Furthermore, the primary magnetic field is weakened by the secondary first magnetic field, thereby suppressing the induced electromotive force in the secondary winding caused by the combined magnetic field. The method is further verified by the finite element method.

[0082] According to the normal force equation of a doubly fed linear motor

[0083]

[0084] It is known that the normal force equation contains both DC and AC quantities. Without proper control, fluctuations in the normal force will occur. To maintain a constant normal force in the doubly-fed linear motor, an effective control method is to control the component i of the current generating the secondary primary magnetic field on the M and T coordinate axes. m1 and i t1 Set as follows

[0085]

[0086] The normal force of the doubly-fed direct motor simplifies to:

[0087]

[0088] Therefore, the normal force can be maintained at a constant value, and can be controlled by I. rdc The magnitude of the normal force is adjusted by the amplitude.

[0089] Furthermore, because the leakage inductance of the secondary winding of a doubly-fed linear motor is relatively small, the mutual inductance is close to the self-inductance of the secondary winding.

[0090]

[0091] Therefore, based on equation (11), the steady-state voltage amplitude equation (2) for the generation of the secondary first magnetic field on the secondary side can be expressed as follows:

[0092]

[0093] It is evident that by weakening the primary magnetic field in the secondary side, the voltage requirement for generating the primary magnetic field on the secondary side can be significantly reduced (reducing voltage U). r1Amplitude).

[0094] Simultaneously, considering the application requirements of high-speed maglev, FEA simulation was performed on the doubly-fed linear motor of a levitation unit in a high-speed maglev train, and an FEA finite element model of the doubly-fed linear motor was built as follows: Figure 2 As shown, the model parameters are shown in Table 1.

[0095] Table 1 Simulation parameters of the doubly fed linear motor

[0096]

[0097]

[0098] Finite element analysis results as follows Figure 3 As shown, despite the limited secondary inverter bus voltage and the presence of a large slip frequency, the normal force can still be maintained at a relatively constant value by using dual-frequency magnetic field combination control. As shown in (3a), the normal force fluctuation is only 1%, which fully verifies the effectiveness of using dual-frequency magnetic field combination control to achieve normal force control.

[0099] Meanwhile, a comparison was made between field weakening control using equation (11) and without field weakening control. The FEA analysis results are shown in (3b) and (3c), where (3b) represents the result with field weakening control applied and (3c) represents the result without field weakening control applied. It can be seen that even at a high slip frequency, field weakening control of the secondary first magnetic field can still effectively suppress the induced electromotive force caused by the combined magnetic field of the primary magnetic field and the secondary first magnetic field in the secondary winding, thus meeting the voltage requirements of the secondary inverter under dual-frequency magnetic field combination control.

[0100] Application Example 2:

[0101] According to equation (9), the output mechanical power and secondary power of the doubly fed linear motor are affected by the traction force of the doubly fed linear motor, and they are both algebraically constrained by the traction force. This application example focuses on the process of controlling the traction force by adjusting the product of the superimposed magnetic field of the secondary first magnetic field and the secondary second magnetic field of the secondary power supply current and the orthogonal component of the primary magnetic field. Further analysis shows that in rail transit applications, the coordinated control of the two unit motors can achieve mutual cancellation of traction force fluctuations, ensuring the smoothness of the overall train traction.

[0102] (7) The traction force equation can be transformed into:

[0103]

[0104] The first term in the formula is the average value of the traction force, and the second term is the thrust fluctuation value caused by the dual-frequency magnetic field combination control.

[0105] As can be seen from equation (15), the component i of the secondary first magnetic field current on the T-axis can be adjusted. t1 The method involves adjusting the average traction force and driving direction to further regulate the output mechanical power and secondary power supply. This also applies to the thrust fluctuation component. One method to address this is to shift the initial phase α of the current required for the second magnetic field of two adjacent unit motors by 180°, thereby canceling out the traction force fluctuation components and ensuring the smoothness of the overall train traction. Other initial phase α shifts can also achieve the same goal of canceling out traction force fluctuation components, such as using a 120° initial phase shift for three unit motors.

[0106] Further, based on the finite element model of the doubly fed linear motor in Application Example 2, FEA simulation was performed to verify the coasting process (where the average traction force is zero, such as...). Figure 4 As shown), the driving process (average traction force is positive, such as...) Figure 5 As shown), during the braking process (the average traction force is negative, such as...) Figure 6 The control effect is shown in (4a), (5a), and (6a). (4a), (5a), and (6a) respectively demonstrate the control effect at i. t1 =0A、i t1 =-14.14A, i t1 =14.14A The simulation results of two unit motors with 180° phase shift are shown in (4b), (5b) and (6b). The average traction force of the combined motor can be in a stable state.

[0107] It is evident that controlling the product of the orthogonal components of the secondary first magnetic field and the primary magnetic field can realize the control of the traction force of the doubly fed linear motor, and through the coordinated control of the two unit motors, the smoothness of the overall traction of the train can be guaranteed with high feasibility.

[0108] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for controlling a doubly-fed linear motor with a dual-frequency magnetic field combination, characterized in that, This method achieves combined control of a doubly-fed linear motor under extreme operating conditions by generating two supply currents of different frequencies in the secondary power supply. The two different frequency supply currents are denoted as the first frequency component and the second frequency component of the secondary power supply current, respectively. The control method includes the following steps: The primary power supply current and the first frequency component of the secondary power supply current of the motor generate a spatially synchronized primary magnetic field and a secondary first magnetic field in the air gap, respectively. At the same time, the second frequency component of the secondary power supply current of the motor generates an additional secondary second magnetic field in the air gap. Stable operation of the doubly fed linear motor is achieved by controlling the magnitude and relative position of the primary magnetic field and the first secondary magnetic field, as well as the magnitude of the second secondary magnetic field. The secondary second magnetic field is stationary relative to the secondary winding; The control of the magnitude of the secondary magnetic field is specifically as follows: By coordinating the control of the secondary first magnetic field and the secondary second magnetic field, the magnitude and fluctuation of the normal force of the doubly fed linear motor can be controlled, thus maintaining a constant normal force of the doubly fed linear motor.

2. The dual-frequency magnetic field combination control method for a doubly-fed linear motor according to claim 1, characterized in that, The control of the magnitude and relative position of the primary magnetic field and the secondary first magnetic field is specifically as follows: The first frequency component of the secondary power supply current that generates the secondary first magnetic field is set to have components on the M and T coordinate axes. The magnitudes of the M-axis current component and the T-axis current component are controlled to partially or completely cancel the primary magnetic field, thereby realizing field weakening control and traction control. The M-axis current component is used for field weakening control, and the T-axis current component is used for traction control.

3. The doubly-fed linear motor dual-frequency magnetic field combination control method according to claim 1, characterized in that, The coordination and control specifically refers to: The magnitude of the normal force is adjusted by the amplitude of the second frequency component of the secondary power supply current; The components of the first frequency component of the secondary power supply current that generates the secondary first magnetic field are set on the M and T coordinate axes. The fluctuation of the normal force is adjusted by coordinating the three components: the M-axis current component of the first frequency component of the secondary power supply current, the T-axis current component of the first frequency component of the secondary power supply current, and the second frequency component of the secondary power supply current.

4. The doubly-fed linear motor dual-frequency magnetic field combination control method according to claim 1, characterized in that, In multiple unit motors, the traction force fluctuations are mutually canceled by directional control of the secondary magnetic field of different unit motors.

5. The doubly-fed linear motor dual-frequency magnetic field combination control method according to claim 4, characterized in that, The directional control of the secondary magnetic field is specifically as follows: The initial phase of the current required for the second magnetic field of the adjacent unit motor. The angle is set by phase misalignment.

6. The dual-frequency magnetic field combination control method for a doubly-fed linear motor according to claim 5, characterized in that, The set angle is 60°, 120° or 180°.

7. A computer-readable storage medium, characterized in that, It includes one or more programs executed by one or more processors of a control device, the one or more programs including instructions for executing the doubly fed linear motor dual-frequency magnetic field combination control method as described in any one of claims 1-6.

8. A control device, characterized in that, It includes one or more processors, a memory, and one or more programs stored in the memory, said one or more programs including instructions for executing the doubly fed linear motor dual-frequency magnetic field combination control method as described in any one of claims 1-6.

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