CN113271050B - Quasi-synchronous power supply control method for long-stator double-fed linear motor - Google Patents

Abstract

The invention relates to a quasi-synchronous power supply control method of a long stator double-fed linear motor, which comprises a stator side power supply control sub-method and a rotor side power supply control sub-method, wherein the stator side power supply control sub-method comprises the following steps: according to the external rotor operation speed requirement, regulating the stator power supply frequency, determining the stator power supply voltage amplitude based on the stator power supply frequency, and performing power supply control on the long stator; the method for controlling the power supply of the rotor side comprises the following steps: and obtaining an expected slip frequency according to the power supply requirement of the rotor side, obtaining a rotor side expected current according to the expected slip frequency, the levitation force and the thrust requirement, determining a rotor power supply voltage amplitude based on the rotor side expected current, and simultaneously controlling the slip frequency within a permissible amplitude limit according to the rotor side power supply device parameter, so as to maintain the long stator double-fed linear motor in a quasi-synchronous running state. Compared with the prior art, the method has the advantages of easiness in implementation, high reliability, low system complexity, rotor-stator decoupling control and the like.

Description

A quasi-synchronous power supply control method for a long-stator double-fed linear motor

Technical Field

The invention belongs to the field of motor and control technology, and in particular relates to a stator power supply control method for a long-stator linear motor.

Background Art

Linear motor is an electromechanical energy conversion device that can directly convert electrical energy into linear motion mechanical energy. It has broad application prospects in rail transportation, textile industry, heavy industry and other fields. Long stator linear motor can be used as the core driving part of rail transportation, which is of great significance to the development of transportation field. In particular, variable air gap rotor suspension linear motor is the technical basis of magnetic levitation rail transportation.

Power supply control technology is the key in long stator linear motor drive system.

For linear motors with stator and mover excitation on both sides, in order to achieve long-term stable electromechanical energy conversion, the basic requirement for linear motor power supply control is that the stator and mover traveling wave magnetic fields must be mutually constrained and coordinated in frequency, amplitude and phase. However, for application scenarios such as rail transit, the mover of the linear motor operates on a large spatial scale. At this time, "motor-stator decoupling control" is very valuable. Otherwise, in order to achieve effective motor power supply control, real-time high-precision detection, transmission or estimation of state information such as the current and position of the mover side must be required, which will greatly affect the reliability and robustness of the high-power electromechanical energy conversion of the entire linear motor system.

The known magnetic levitation linear motor technology realizes the drive of the electric excitation synchronous motor, the DC excitation on the mover side, and the real-time transmission of the mover position and other information to the stator inverter through high-frequency communication. The stator inverter realizes the motor magnetic field oriented control by adjusting the stator excitation current. Another problem with this solution is that an independent contact or non-contact mover power supply device is required.

The linear doubly-fed motor is also called an "AC excitation asynchronous motor". Its characteristic is that the mover side uses a variable frequency AC excitation method, which allows the "different power supply states on the stator side and the change of the motion state on the mover side" to be met by controlling the power supply frequency and phase on the mover side. This provides a technical basis for the independent and decoupled power supply control of the stator and mover.

However, the two common long-stator linear doubly-fed motor control strategies currently have the following shortcomings:

(1) The first known solution (NBP technology solution from Germany) refers to the method of electrically excited synchronous motors. The position and other information of the mover are transmitted to the stator-side inverter in real time through a communication channel. Its advantage is that it can achieve a more flexible control effect. However, it inherits the disadvantage of tight coupling between the mover and stator control of synchronous motors and cannot achieve independent decoupling control of the mover and stator.

(2) In the control method of the doubly-fed linear motor studied in the known scheme 2 (Southwest Jiaotong University, etc.), the stator magnetic field is oriented controlled on the mover side, the independent mover operation state is controlled, and a fixed frequency and constant voltage amplitude is used for power supply on the stator side. The advantage is that the stator power supply control is simple and efficient, but the disadvantage is that in order to adapt to the wide range of slip frequency changes caused by the fixed stator frequency, the capacity of the mover side inverter is significantly increased; and in order to adapt to the wide range of changes in the mover speed, a large-capacity energy storage component needs to be configured on the mover side to store the charge and discharge energy on the mover side.

Summary of the invention

The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a quasi-synchronous power supply control method for a long-stator doubly-fed linear motor with low system complexity and capable of realizing mover-stator decoupling control.

The purpose of the present invention can be achieved by the following technical solutions:

A quasi-synchronous power supply control method for a long-stator double-fed linear motor is applied to the long-stator double-fed linear motor, wherein the long-stator double-fed linear motor comprises a long stator and a mover which are separately powered by a variable frequency and variable voltage AC power supply device, the long stator and the mover are non-contactly arranged, and the mover is suspended by the normal force of the air gap, and comprises a stator side power supply control sub-method and a mover side power supply control sub-method, wherein:

The stator side power supply control method is: according to the external mover running speed requirement, the stator power supply frequency is adjusted, the stator power supply voltage amplitude is determined based on the stator power supply frequency, the power supply of the long stator is controlled, and the mover speed closed-loop control is realized;

The power supply control method on the mover side is as follows: the expected slip frequency is obtained according to the power supply power demand on the mover side, the expected current on the mover side is obtained according to the expected slip frequency, suspension force and thrust demand, the mover power supply voltage amplitude is determined based on the expected current on the mover side, the power supply of the mover is controlled, and at the same time, according to the parameters of the power supply device on the mover side, the slip frequency is controlled within the allowable limit, the long stator double-fed linear motor is maintained in a quasi-synchronous operation state, and the current closed-loop and slip frequency dual closed-loop control are realized.

Furthermore, the adjustment of the slip frequency is mainly based on the mover side. When the mover side cannot control the slip frequency to meet the allowable limit, a control request is generated on the mover side. The stator side receives and responds to the control request and adjusts the stator power supply frequency.

Furthermore, the parameters of the power supply device on the mover side include the capacity of the power supply device.

Furthermore, in the mover-side power supply control sub-method, the desired slip frequency is obtained by open-loop setting or closed-loop regulation.

Furthermore, the voltage-frequency function is a positive correlation function.

Furthermore, after the stator power supply voltage amplitude is determined, the stator power supply voltage amplitude is dynamically corrected based on the actual value of the stator current and the protection optimization control strategy.

Furthermore, the protection optimization control strategy includes but is not limited to maximum output power protection, maximum output current protection, current source control mode, etc.

Furthermore, in the mover-side power supply control submethod, the state of the stator excitation magnetic field is detected or estimated in real time, and the mover-side current is closed-loop controlled based on the magnetic field oriented control principle.

Furthermore, the mover is driven by a plurality of unit motors, and the power supply current of each unit motor is independently controlled to achieve specific suspension state control of the mover.

Furthermore, the specific suspension state of the mover includes a long-term static floating state. In this long-term static floating state, some of the unit motors work in a driving state, and some of the unit motors work in a braking state. The driving force of the unit motor in the driving state is balanced with the braking force of the unit motor in the braking state. Under the constraint that the thrust in the horizontal direction of the mover is zero, stable non-zero regulation of the electromagnetic suspension force in the normal direction and the power supply power on the mover side is achieved.

Compared with the prior art, the present invention has the following beneficial effects:

(1) In the power supply control method of the present application, the stator power supply frequency and voltage amplitude are determined by the desired moving speed of the mover, and do not rely on the real-time power state feedback of the mover. The desired "motor-stator independent decoupling control" can be achieved, which reduces the degree of information coupling between the mover and the stator, significantly improves the reliability of system operation, and simplifies the complexity of system implementation.

(2) Referring to the basic concept of V/F constant flux control, the stator power supply frequency is adjusted according to the expected rotor running speed; the closed-loop control of the slip frequency is achieved by controlling the effective power supply power on the rotor side, ensuring that the slip frequency on the rotor side can be basically maintained within a small fluctuation range, that is, maintaining the so-called "quasi-synchronous operation state". Because the power supply power on the rotor side (the so-called slip power) is proportional to the slip frequency and mechanical power, limiting the slip frequency means limiting the power supply power on the rotor side. Under the same mechanical power conditions, the capacity of the inverter and energy storage components on the rotor side can be significantly reduced.

(3) The stator-side power supply control step of the present invention responds upon receiving a control request from the mover side and intervenes in the stator power supply frequency, thereby ensuring that the desired slip frequency and the desired mover speed are always maintained, thereby ensuring the maintenance of the quasi-synchronous operation state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a quasi-synchronous power supply control method for a doubly-fed linear motor in Embodiment 1 of the present invention;

FIG2 is a schematic diagram of the V/F function law U _s =f(ω _s ) of the stator power supply in Example 1;

FIG3 is a schematic diagram of the results of various variables when the quasi-synchronous control method is applied in Example 1, wherein (a) is a schematic diagram of the acceleration process of the magnetic levitation linear motor, (b) is a schematic diagram of the motor thrust control result, (c) is a schematic diagram of the change of the power supply frequency of the mover, (d) is a schematic diagram of the change of the charging power on the mover side, and (e) is a schematic diagram of the change of the power of the energy storage device on the mover side;

FIG. 4 is a schematic diagram of the long-term static floating of the mover in Example 2.

DETAILED DESCRIPTION

The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

Example 1

The present embodiment provides a quasi-synchronous power supply control method for a long-stator doubly-fed linear motor, wherein the long-stator doubly-fed linear motor includes a long stator and a mover which are powered separately, and the long stator and the mover are non-contact arranged, that is, there is no wired or contact information and power transmission path between the mover and the stator, and the mover is suspended by the normal force of the air gap. The control principles of the stator side and the mover side in this method are shown in Figure 1. In this method, the stator and the mover are both powered by a variable frequency and voltage (VVVF) AC power supply device.

The method includes a stator side power supply control sub-method and a mover side power supply control sub-method, wherein the stator side power supply control sub-method is: according to the external mover running speed requirement, the stator power supply frequency is adjusted, the stator power supply voltage amplitude is determined based on the stator power supply frequency, the long stator is powered on and closed-loop control of the mover speed is achieved; the mover side power supply control sub-method is: according to the mover side power supply power requirement, the expected slip frequency is obtained, according to the expected slip frequency, suspension force and thrust requirement, the mover side expected current is obtained, the mover power supply voltage amplitude is determined based on the expected current on the mover side, the mover is powered on and controlled, and at the same time, according to the mover side power supply device parameters, the slip frequency is controlled within the allowable limit, the long stator double-fed linear motor is maintained in a quasi-synchronous operation state, and the current closed-loop and slip frequency double closed-loop control are achieved.

The control principle on the stator side is as follows:

和检测得到的动子实际速率v_r，通过调节定子供电频率ω_s，从而完成动子速率闭环控制。其中，如图2所示，本实施例中，定子供电电压幅值U_s作为因变量，由定子供电频率ω_s按照线性V/F函数确定：The stator side is based on the expected speed of the mover

The actual speed v _r of the mover is detected, and the closed-loop control of the speed of the mover is completed by adjusting the stator power supply frequency ω _s . As shown in FIG2 , in this embodiment, the stator power supply voltage amplitude U _s is used as a dependent variable, and is determined by the stator power supply frequency ω _s according to a linear V/F function:

U _s ＝f(ω _s )＝kω _s +U ₀

After determining the stator supply voltage amplitude, the stator supply voltage amplitude is dynamically corrected as necessary based on the actual value of the stator current and the protection optimization control strategy, and then the long stator is powered on. The protection optimization control strategy includes but is not limited to maximum output power protection, maximum output current protection, current source control mode, etc.

The power supply control principle of the mover side is as follows:

According to the formula:

开环给出期望转差频率

The power supply requirement on the mover side can be

Open loop gives the expected slip frequency

期望悬浮力

和推力需求

实时检测或者估算定子激磁磁场状态，基于磁场定向控制原理，计算得到期望动子电流矢量

基于定子磁场定向实现电流闭环的基础上形成完整的转差频率ω_f闭环控制。期望转差频率

可通过开环设定或者闭环调节方式获得。According to the expected slip frequency

Expected suspension force

and thrust requirements

Real-time detection or estimation of the stator excitation magnetic field state, based on the field oriented control principle, calculate the desired rotor current vector

Based on the stator magnetic field orientation to realize the current closed loop, a complete slip frequency ω _f closed loop control is formed. Expected slip frequency

It can be obtained through open-loop setting or closed-loop adjustment.

和供电功率限幅

当动子侧不能维持转差频率ω_f在允许限幅内的情况下，产生所述动子侧的控制请求，对“定子供电频率ω_s”进行干预，进而可以确保一直维持“期望的转差频率

”和期望的动子速率

即维持所谓“准同步运行状态”。The adjustment of the slip frequency is mainly based on the mover side. When the mover side cannot control the slip frequency to meet the allowable limit, a control request is generated on the mover side. The stator side receives and responds to the control request and adjusts the stator power supply frequency. The control request on the mover side is generated in the following way: Determine the current mover side slip frequency limit according to parameters such as the capacity of the mover AC power supply device

and power supply limiting

When the mover side cannot maintain the slip frequency ω _f within the allowable limit, a control request is generated on the mover side to intervene in the "stator power supply frequency ω _s ", thereby ensuring that the "desired slip frequency

" and the desired mover velocity

That is, maintain the so-called "quasi-synchronous operation state".

The mover is driven by a number of unit motors, and the power supply current of each unit motor is independently controlled to achieve suspension force control of the mover.

Referring to FIG2 , the above method can be implemented by a control system, which includes a power supply frequency adjustment module 11, a stator power supply voltage calculation module 12, a long stator VVVF power supply device 13, a mover speed detection module 14, a stator current feedback correction module 15, a mover side power supply power adjustment module 21, a mover side desired current calculation module 22, a mover side power supply current adjustment module 23, a stator magnetic field observation or detection module 24 and a mover VVVF power supply device 25. The control process of the above control system is as follows:

获得定子供电频率ω_s；定子供电电压计算模块12根据ω_s计算定子供电电压幅值U_s，计算函数采用预选的V/F函数规律U_s＝f(ω_s)；通过计算获得的定子供电电压幅值U_s对长定子VVVF供电装置13的供电参数进行调节；定子电流反馈修正模块15对定子电流进行检测和动态修正，实现保护和电流源控制等功能。Stator side: The power supply frequency adjustment module 11 detects the rotor speed v _r and the desired rotor speed in real time according to the rotor speed detection module 14.

The stator power supply frequency ω _s is obtained; the stator power supply voltage calculation module 12 calculates the stator power supply voltage amplitude U _s according to ω _s , and the calculation function adopts the pre-selected V/F function law U _s =f(ω _s ); the power supply parameters of the long stator VVVF power supply device 13 are adjusted by the calculated stator power supply voltage amplitude U _s ; the stator current feedback correction module 15 detects and dynamically corrects the stator current to realize functions such as protection and current source control.

及实时测得的动子供电功率P_er，通过开环设定或者闭环调节方式给出“期望转差频率

”，动子侧期望电流计算模块22根据期望转差频率

期望悬浮力

和推力需求

以及定子磁场观测或检测模块24对当前运行状态进行检测和估计的结果，计算得到期望动子电流矢量

完成对动子VVVF供电装置25的电流闭环调节，并在此基础上形成完整的转差频率ω_f闭环控制。Movers: Movers power supply adjustment module 21 adjusts the power supply according to the movers power demand.

The real-time measured power supply of the actuator _Per is used to give the "expected slip frequency" through open-loop setting or closed-loop adjustment.

", the expected current calculation module 22 on the mover side calculates the expected slip frequency

Expected suspension force

and thrust requirements

The stator magnetic field observation or detection module 24 detects and estimates the current operating state, and calculates the desired rotor current vector

The current closed-loop regulation of the mover VVVF power supply device 25 is completed, and on this basis, a complete slip frequency ω _f closed-loop control is formed.

This embodiment introduces the quasi-synchronous power supply control method of a long-stator doubly-fed linear motor by combining the parameters of a specific doubly-fed linear motor maglev prototype. The unit motor parameters are: stator resistance 0.433Ω, mover resistance 0.86Ω, stator self-inductance 85.4mH, mover self-inductance 68.4mH, mutual inductance 59.8mH, pole pitch 0.157m, and pole pair number 5. The magnetic floater is driven by 10 unit motors, and the total suspension mass is 40 tons.

The working condition is set as the magnetic levitation linear motor accelerating from the initial uniform motion state of 10m/s to the uniform speed state of 15m/s, as shown in Figure 3(a); the thrust control result of each unit motor is shown in Figure 3(b).

需求设为26kW，如图3(c)所示；根据动子侧功率需求，计算得出期望转差频率

如图3(d)所示；由于动子匀速和加速的切换过程中期望转差速率变化较大，在实际控制中对转差速率控制进行修正，使其均匀缓慢调节，所以动子侧实际充电功率P_er并未完全跟随动子侧需求充电功率，但这不并影响动子侧储能装置电量在大时间尺度上维持在一个稳定的范围内；如图3(e)所示，初始时刻动子侧储能装置电量为20kW·h，在由匀速到加速再到匀速过程中，储能装置电量控制在允许的波动范围以内。During the operation of this magnetic levitation motor, the average power demand of the power supply equipment on the rotor side is 26kW. In order to maintain the constant power of the energy storage device on the rotor side, the total charging power on the rotor side is

The demand is set to 26kW, as shown in Figure 3(c); based on the power demand on the rotor side, the expected slip frequency is calculated

As shown in Figure 3(d); due to the large change in the expected slip rate during the switching process of the mover between uniform speed and acceleration, the slip rate control is corrected in the actual control to make it evenly and slowly adjusted, so the actual charging power _Per on the mover side does not completely follow the required charging power on the mover side, but this does not affect the power of the energy storage device on the mover side to be maintained within a stable range on a large time scale; as shown in Figure 3(e), at the initial moment, the power of the energy storage device on the mover side is 20kW·h. In the process from uniform speed to acceleration and then to uniform speed, the power of the energy storage device is controlled within the allowable fluctuation range.

Example 2

This embodiment focuses on how to achieve "long-term static floating" of the mover.

As shown in FIG4 , the mover can be divided into two groups of unit motors, and the power supply current of each group of unit motors is independently controlled so that unit motor 1 works in a driving state and unit motor 2 works in a braking state; the current amplitude I _r1 of unit motor 1 on the mover side is controlled to be equal to the current amplitude I _r2 of unit motor 2:

I _r1 ＝I _r2

And control to ensure that the angle α ₁ between the current vector i _r1 and the stator _{current is} , and the angle α ₂ between the current vector i _r2 and the stator _{current is}

Opposite phase:

α ₁ = -α ₂

According to the relationship between current and thrust:

It can be seen that the driving force of the unit motor 1 in the driving state is balanced with the braking force of the unit motor 2 in the braking state, that is,

_Fx1 = _-Fx2

At this time, according to the normal force formula:

It can be seen that

F _z1 = F _z2

The normal force of the unit motor 1 in the driving state is equal to the normal force of the unit motor 2 in the braking state, thereby achieving stable non-zero regulation of the electromagnetic suspension force in the normal direction under the constraint that the thrust in the horizontal direction of the mover is zero.

At this time, the mover and the stator are in a relatively static state, and the effective power supply formula on the mover side is:

It can be seen that the unit motor 1 in the driving state absorbs electromagnetic power from the stator side to charge the on-board energy storage device, and the unit motor 2 in the braking state outputs electromagnetic power of equal amplitude to the stator side, so that the energy circulates between the mover side and the stator side; and the size of the transmitted energy can be adjusted by adjusting the size of the power supply frequency ω _f .

Furthermore, the absolute values of _α1 and _α2 may be adjusted to be unequal, thereby adjusting the power supply to the mover side.

In this long-term static floating state, some of the unit motors work in the driving state, and the other unit motors work in the braking state. The driving force of the unit motor in the driving state is balanced with the braking force of the unit motor in the braking state. Under the constraint that the thrust in the horizontal direction of the mover is zero, stable non-zero regulation of the electromagnetic suspension force in the normal direction and the power supply power on the mover side is achieved.

The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims (8)

1. The quasi-synchronous power supply control method for the long-stator double-fed linear motor is applied to the long-stator double-fed linear motor, the long-stator double-fed linear motor comprises a long stator and a rotor which are respectively and independently powered by a variable-frequency and variable-voltage alternating-current power supply device, the long stator and the rotor are arranged in a non-contact mode, and the rotor is in suspension operation through an air gap normal force, and is characterized by comprising a stator side power supply control sub-method and a rotor side power supply control sub-method,

the stator side power supply control method comprises the following steps: according to the external rotor running speed requirement, regulating the stator power supply frequency, determining the stator power supply voltage amplitude based on the stator power supply frequency, and performing power supply control on the long stator to realize rotor speed closed-loop control;

the method for controlling the power supply of the rotor side comprises the following steps: the method comprises the steps of obtaining expected slip frequency according to the power supply requirement of a rotor side, detecting or estimating the state of a stator exciting magnetic field in real time according to the expected slip frequency, levitation force and thrust requirement, obtaining the expected current of the rotor side based on a magnetic field orientation control principle, determining the amplitude of the power supply voltage of the rotor based on the expected current of the rotor side, performing power supply control on the rotor, controlling the slip frequency within the allowable amplitude limit according to the parameters of a power supply device of the rotor side, maintaining the long stator doubly-fed linear motor in a quasi-synchronous running state, and realizing current closed loop and slip frequency double closed loop control.

2. The method for quasi-synchronous power supply control of a long stator doubly-fed linear motor according to claim 1, wherein the adjustment of the slip frequency is based on a rotor side, and when the slip frequency cannot be controlled by the rotor side to meet the allowable clipping, a control request of the rotor side is generated, and the stator side receives and responds to the control request to adjust the stator power supply frequency.

3. The method of claim 1, wherein the mover-side power supply parameter includes a power supply capacity.

4. The method for quasi-synchronous power supply control of a long stator doubly-fed linear motor according to claim 1, wherein the desired slip frequency is obtained by an open loop setting or a closed loop adjustment.

5. The method of claim 1, wherein the stator supply voltage magnitude is given by a voltage frequency function, and the voltage frequency function is a positive correlation function.

6. The method for quasi-synchronous power supply control of a long stator doubly-fed linear motor according to claim 1, wherein after determining the stator power supply voltage amplitude, the stator power supply voltage amplitude is dynamically modified based on a stator current actual value and a protection optimization control strategy.

7. The method of claim 6, wherein the protection optimization control strategy comprises maximum output power protection, maximum output current protection, or current source control mode.

8. The method for quasi-synchronous power supply control of a long stator doubly-fed linear motor according to claim 1, wherein the mover is driven by a plurality of unit motors, the power supply current of each unit motor is independently controlled to realize specific levitation state control of the mover, the specific levitation state of the mover comprises a long-time levitation state in which part of the unit motors of the plurality of unit motors are operated in a driving state and part of the unit motors are operated in a braking state, the driving force of the unit motors in the driving state is balanced with the braking force of the unit motors in the braking state, and stable non-zero adjustment of the electromagnetic levitation force in the normal direction and the power supply power at the side of the mover is realized under the constraint that the thrust applied to the horizontal direction of the mover is zero.

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