阅读说明：本技术 一种变磁通永磁电机充磁状态闭环控制方法和系统 (Closed-loop control method and system for magnetizing state of variable flux permanent magnet motor ) 是由 陈俊桦 曲荣海 于 2020-06-11 设计创作，主要内容包括：本发明公开了一种变磁通永磁电机充磁状态闭环控制方法和系统,属于变磁通永磁电机驱动控制领域。首先,检测d轴电流反馈值并利用电流磁链曲线获取d轴电枢磁链,并结合前一控制周期的d轴电枢磁链计算d轴电枢磁链的变化以获取感应电压Udi；再基于感应电压与充磁状态间的关系曲线,利用所述感应电压Udi获得充磁状态估计值Φest；然后,将充磁状态指令Φcmd与所述充磁状态估计值Φest进行误差比较后,经逻辑判断生成d轴电流指令差值,进而更新d轴电流指令Id*,用于进行电流闭环控制。本发明基于d轴电流在充退磁过程中产生的感应电压变化进行充磁状态估计,并引入电压解耦合器,使得变磁通永磁电机静止和旋转状态下均能达到电机充磁状态的精确控制。(The invention discloses a closed-loop control method and a closed-loop control system for the magnetizing state of a variable flux permanent magnet motor, and belongs to the field of variable flux permanent magnet motor drive control. Firstly, detecting a d-axis current feedback value, acquiring a d-axis armature flux linkage by using a current flux linkage curve, and calculating the change of the d-axis armature flux linkage by combining the d-axis armature flux linkage of the previous control period to acquire an induced voltage Udi; based on a relation curve between the induced voltage and the magnetizing state, obtaining a magnetizing state estimated value phi est by utilizing the induced voltage Udi; and then, after error comparison is carried out on the magnetizing state command phi cmd and the magnetizing state estimated value phi est, a d-axis current command difference value is generated through logic judgment, and then the d-axis current command Id is updated and used for carrying out current closed-loop control. The invention estimates the magnetizing state based on the induced voltage change generated by d-axis current in the magnetizing and demagnetizing processes, and introduces the voltage decoupling device, so that the magnetizing state of the variable flux permanent magnet motor can be accurately controlled in the static and rotating states.)

1. A closed-loop control method for the magnetizing state of a variable flux permanent magnet motor is characterized by comprising the following steps:

detecting a d-axis current feedback value, acquiring a d-axis armature flux linkage by using a current flux linkage curve, and calculating the change of the d-axis armature flux linkage by combining the d-axis armature flux linkage of the previous control period to acquire an induced voltage Udi;

based on a relation curve between the induced voltage and the magnetizing state, obtaining a magnetizing state estimated value phi est by utilizing the induced voltage Udi;

and after error comparison is carried out on the magnetizing state command phi cmd and the magnetizing state estimated value phi est, a d-axis current command difference value is generated through logic judgment, and then the d-axis current command Id is updated and used for carrying out current closed-loop control.

2. The closed-loop control method for the charging state of the variable flux permanent magnet motor according to claim 1, further comprising

Obtaining q-axis rotation coupling voltage according to the product of the d-axis armature flux linkage and the rotating speed, and setting a q-axis current instruction to be zero;

and taking the q-axis current command and the updated d-axis current command Id as input, and simultaneously taking the induced voltage Udi and the q-axis rotation coupling voltage as feedforward compensation to realize current closed-loop control.

3. A closed-loop control system for the magnetizing state of a variable flux permanent magnet motor is characterized by comprising a magnetizing state controller and a current closed-loop controller; wherein, the current closed-loop controller is used for the current closed-loop control in the process of magnetization and demagnetization, and the magnetization state controller comprises

The magnetizing state estimator is used for detecting a d-axis current feedback value, acquiring a d-axis armature flux linkage by using a current flux linkage curve, and calculating the change of the d-axis armature flux linkage by combining the d-axis armature flux linkage of the previous control period to acquire an induced voltage Udi; then based on a relation curve between the induced voltage and the magnetizing state, obtaining a magnetizing state estimated value phi est by utilizing the induced voltage Udi;

and the closed-loop controller of the variable flux permanent magnet motor is used for comparing the magnetizing state command phi cmd with the magnetizing state estimated value phi est, generating a d-axis current command difference value through a logic judger, and further updating a d-axis current command Id for current closed-loop control.

4. The closed-loop control system for the magnetization state of a variable flux permanent magnet motor of claim 3, wherein the magnetization state controller further comprises

And the voltage decoupling device is used for generating a q-axis current instruction and separating the induced voltage and the rotating coupling voltage from the dq-axis voltage to be used as a current control feedforward compensation voltage.

5. The variable flux permanent magnet motor magnetization state closed-loop control system of claim 4, wherein the voltage decoupler sets the q-axis current command to zero and derives the q-axis rotational coupling voltage based on a product of the d-axis armature flux linkage and the rotational speed.

6. The closed-loop control system for the magnetization state of the variable flux permanent magnet motor according to claim 5, wherein the current closed-loop controller uses the q-axis current command and the updated d-axis current command Id as input, and the induced voltage Udi and the q-axis rotation coupling voltage as feed-forward compensation to realize the closed-loop control of the current.

7. The closed-loop control system for the magnetizing state of the variable-flux permanent magnet motor according to any one of claims 3 to 6, wherein a magnetizing state command Φ cmd is compared with the magnetizing state estimation value Φ est to obtain an error Φ diff, a d-axis current command difference Did is output through a logic judger, and then the d-axis current command Id is added to the d-axis current feedback value Id to form the d-axis current command Id;

wherein the logic of the logic judger is:

DId ═ Idf if the error Φ diff is greater than or equal to zero; idf is the current stepping precision in the process of magnetization and demagnetization;

if the error Φ diff is less than zero, DId ═ -Id, thereby clearing the magnetizing and demagnetizing current command.

Technical Field

The invention belongs to the field of variable flux permanent magnet motor drive control, and particularly relates to a closed-loop control method and a closed-loop control system for a variable flux permanent magnet motor magnetizing state.

Background

The variable flux permanent magnet motor is used for improving the comprehensive efficiency of the traditional permanent magnet motor in the field of speed regulation driving application. The traditional permanent magnet motor adopts a high-coercivity permanent magnet, and the magnetizing state of the motor cannot be changed after the permanent magnet is magnetized. When a traditional permanent magnet motor operates in a high-speed interval, the voltage of the motor terminal exceeds the voltage of a direct current bus, so that weak magnetic current needs to be continuously injected into a d axis of a motor rotating coordinate system to offset counter potential voltage increased along with the rotating speed, namely weak magnetic control.

In the field weakening control of the traditional permanent magnet motor, because of the existence of continuous field weakening current, extra copper loss is introduced into the field weakening current, and the high-speed operation efficiency is reduced. The weak magnetic current increases the phase difference between the current and the voltage, thereby reducing the power factor of the motor. In the application of wide speed regulation range, for example, the ratio of the highest rotating speed to the rated rotating speed is more than 4: 1, the flux weakening control will reduce the efficiency of the motor more significantly.

The variable magnetic flux permanent magnet motor is characterized in that the motor adopts a low-coercivity permanent magnet or adopts a mixed configuration of the low-coercivity permanent magnet and a high-coercivity permanent magnet. The low-coercivity permanent magnet is used as a variable magnet in the motor, and because the coercivity of the permanent magnet is low, the magnetizing and demagnetizing operation can be completed by properly loading the armature magnetic field of the motor. The purpose of changing the air gap magnetic field intensity is achieved through the magnetizing and demagnetizing operations of the variable flux permanent magnet motor, and then the no-load permanent magnet flux linkage of the motor, namely the magnetizing degree of the variable flux permanent magnet motor, is changed.

The variable magnetic flux permanent magnet motor has the operating characteristics that the motor is magnetized in a low-speed interval, so that the motor operates in a high magnetizing state, and the voltage of the motor is increased; the motor is demagnetized in a high-speed interval, so that the motor operates in a low magnetizing state, the voltage of the motor is reduced, continuous weak magnetic current is eliminated, loss is reduced, and the efficiency of the motor is improved. The high-efficiency operation in a wide speed range is realized by controlling the magnetizing state of the variable flux permanent magnet motor.

The magnetizing state control of the variable magnetic flux permanent magnet motor is realized through d-axis pulse current, and the magnetizing state control precision can be improved through the magnetizing state closed-loop control. The closed-loop control of the magnetizing state is realized by identifying the magnetizing state of the current motor in real time through methods such as detection, estimation, observation and the like in the magnetizing and demagnetizing processes, and comparing the magnetizing state with a magnetizing and demagnetizing state instruction set to generate a proper d-axis magnetizing and demagnetizing current instruction value.

The key of the closed-loop control of the magnetizing state is that the controller needs to accurately acquire the current magnetizing state. In document 1, the current magnetization state is calculated using dq-axis command voltages Ud and Uq, dq-axis currents Id and Iq, and a motor electromagnetic synchronous rotation speed w 1. The method is derived based on a motor steady state mathematical model. The limitation of the method is that the reciprocal of the speed is involved in the calculation process, so the method fails in the demagnetization control at the zero speed.

In document 2, the observation of the degree of magnetization is performed using a principle based on an observer. The observer method has the problem of convergence speed, and when the magnetizing and demagnetizing speeds approach the observer convergence speed, the magnetizing state obtained by the observer cannot effectively track the magnetizing state of the actual motor, so that errors in observation and control of the magnetizing state are caused.

Further, the observation methods adopted in documents 1 and 2 are developed based on the back electromotive force of the motor, and therefore when the motor is operated in a low rotation speed range, the accuracy of observation of the state of magnetization is significantly reduced subject to the influence of the low back electromotive force and the dead zone effect of the power electronic inverter.

Document 1: chinese patent 201410075969

Document 2: paper DOI: 10.1109/TIA.2018.2810804

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a closed-loop control method and a closed-loop control system for the magnetizing state of a variable flux permanent magnet motor, and aims to ensure that the precise control of the magnetizing state of the motor can be achieved in the static and rotating states of the variable flux permanent magnet motor.

In order to achieve the above object, in one aspect, the present invention provides a closed-loop control method for a magnetization state of a variable flux permanent magnet motor, including the following steps:

detecting a d-axis current feedback value, acquiring a d-axis armature flux linkage by using a current flux linkage curve, and calculating the change of the d-axis armature flux linkage by combining the d-axis armature flux linkage of the previous control period to acquire an induced voltage Udi;

based on a relation curve between the induced voltage and the magnetizing state, obtaining a magnetizing state estimated value phi est by utilizing the induced voltage Udi;

and after error comparison is carried out on the magnetizing state command phi cmd and the magnetizing state estimated value phi est, a d-axis current command difference value is generated through logic judgment, and then the d-axis current command Id is updated and used for carrying out current closed-loop control.

Further, the method also comprises

Obtaining q-axis rotation coupling voltage according to the product of the d-axis armature flux linkage and the rotating speed, and setting a q-axis current instruction to be zero;

and taking the q-axis current command and the updated d-axis current command Id as input, and simultaneously taking the induced voltage Udi and the q-axis rotation coupling voltage as feedforward compensation to realize current closed-loop control.

The invention also provides a closed-loop control system for the magnetizing state of the variable flux permanent magnet motor, which comprises a magnetizing state controller and a current closed-loop controller; wherein, the current closed-loop controller is used for the current closed-loop control in the process of magnetization and demagnetization, and the magnetization state controller comprises

The magnetizing state estimator is used for detecting a d-axis current feedback value, acquiring a d-axis armature flux linkage by using a current flux linkage curve, and calculating the change of the d-axis armature flux linkage by combining the d-axis armature flux linkage of the previous control period to acquire an induced voltage Udi; then based on a relation curve between the induced voltage and the magnetizing state, obtaining a magnetizing state estimated value phi est by utilizing the induced voltage Udi;

and the closed-loop controller of the variable flux permanent magnet motor is used for comparing the magnetizing state command phi cmd with the magnetizing state estimated value phi est, generating a d-axis current command difference value through a logic judger, and further updating a d-axis current command Id for current closed-loop control.

Further, the magnetizing state controller further comprises

And the voltage decoupling device is used for generating a q-axis current instruction and separating the induced voltage and the rotating coupling voltage from the dq-axis voltage to be used as a current control feedforward compensation voltage.

Further, the voltage decoupling device sets the q-axis current command to be zero, and obtains the q-axis rotation coupling voltage according to the product of the d-axis armature flux linkage and the rotating speed.

Further, the current closed-loop controller takes the q-axis current command and the updated d-axis current command Id as input, and the induced voltage Udi and the q-axis rotation coupling voltage are used as feedforward compensation, so that current closed-loop control is realized.

Further, comparing a magnetizing state command Φ cmd with the magnetizing state estimation value Φ est to obtain an error Φ diff, outputting a d-axis current command difference value Did through a logic judger, and adding the d-axis current command difference value to the d-axis current feedback value Id to form a d-axis current command Id;

wherein the logic of the logic judger is:

DId ═ Idf if the error Φ diff is greater than or equal to zero; idf is the current stepping precision in the process of magnetization and demagnetization;

if the error Φ diff is less than zero, DId ═ -Id, thereby clearing the magnetizing and demagnetizing current command.

Through the technical scheme, compared with the prior art, the invention can obtain the following beneficial effects:

(1) according to the invention, the magnetizing state is estimated based on the parameter nonlinear characteristic caused by the motor saturation effect in the magnetizing and demagnetizing processes and the induced voltage change generated by the d-axis current in the magnetizing and demagnetizing processes, so that additional signal injection is not needed, and the system configuration difficulty is reduced; in addition, because the method does not need a rotating speed signal in the calculation process, the method can be applied to low-speed and zero-speed states, and the application rotating speed interval of the magnetizing state estimation is expanded.

(2) The invention introduces the voltage decoupling coupler, sets the q-axis current instruction as zero, and calculates and generates the dq-axis voltage compensation instruction in the current closed-loop control, thereby improving the precision of the magnetizing state estimation method and reducing the cross saturation influence caused by the q-axis current.

Drawings

FIG. 1 is a schematic diagram of a closed-loop control system for the magnetizing state of a variable flux permanent magnet motor according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a magnetization state controller in a magnetization state closed-loop control system of a variable flux permanent magnet motor according to an embodiment of the present invention;

FIG. 3 is a graph of magnetizing current versus d-axis flux linkage in an embodiment of the present invention;

FIG. 4 is a graph of induced voltage versus an estimate of state of magnetization in an embodiment of the present invention;

FIG. 5 is a schematic diagram of a current closed-loop controller according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The embodiment of the invention provides a closed-loop control method for the magnetizing state of a variable flux permanent magnet motor on the one hand, which comprises the following steps:

detecting a d-axis current feedback value, acquiring a d-axis armature flux linkage by using a current flux linkage curve, and calculating the change of the d-axis armature flux linkage by combining the d-axis armature flux linkage of the previous control period to acquire an induced voltage Udi;

based on a relation curve between the induced voltage and the magnetizing state, obtaining a magnetizing state estimated value phi est by utilizing the induced voltage Udi;

and after error comparison is carried out on the magnetizing state command phi cmd and the magnetizing state estimated value phi est, a d-axis current command difference value is generated through logic judgment, and then the d-axis current command Id is updated and used for carrying out current closed-loop control.

Further, the method also comprises

Obtaining q-axis rotation coupling voltage according to the product of the d-axis armature flux linkage and the rotating speed, and setting a q-axis current instruction to be zero;

and taking the q-axis current command and the updated d-axis current command Id as input, and simultaneously taking the induced voltage Udi and the q-axis rotation coupling voltage as feedforward compensation to realize current closed-loop control.

On the other hand, the embodiment of the present invention further provides a closed-loop control system for a magnetization state of a variable flux permanent magnet motor, as shown in fig. 1, which is a system diagram of the variable flux permanent magnet motor during a magnetization and demagnetization operation.

In the figure, a variable flux permanent magnet motor 109 is driven by a three-phase half-bridge power electronic inverter circuit 105, and the three-phase inverter circuit 105 is energized by a dc power supply 106. A position detecting unit 110 is attached to the shaft of the flux-changing permanent magnet motor 109, and a speed calculating unit 111 obtains an electromagnetic synchronous rotational speed w1 of the motor by calculation based on the detected rotor position θ. And a current sensor 108 is arranged on a three-phase outlet wire of the variable flux permanent magnet motor and used for acquiring phase currents Iu and Iv of the motor. The dq-axis currents Id and Iq in the synchronous rotation coordinate system are calculated by the first coordinate conversion unit 107.

The input amounts of the magnetizing state controller 101 are a command value Φ cmd of the magnetizing state, a motor synchronous rotation speed w1, and a motor d-axis current feedback value Id. The magnetizing state controller 101 executes a magnetizing state closed-loop control algorithm, and generates instructions Id and Iq of dq-axis current according to input quantities; meanwhile, the magnetizing state controller 101 may further generate dq-axis compensation voltages Udff, Uqff in the dq-axis current controller for the auxiliary current control section 102 to control the dq-axis current.

The current control unit 102 performs closed-loop control of the dq-axis current of the variable flux permanent magnet motor 109, and adjusts and generates dq-axis voltage commands Ud and Uq in accordance with the dq-axis current commands Id and Iq, the feedback currents Id and Iq, and the dq-axis voltage compensations Udff and Uqff generated by the magnetization state controller 101.

The second coordinate conversion unit 103 converts the dq-axis voltage commands Ud and Uq into three-phase voltage commands Uu, Uv, and Uw. The PWM control unit 104 generates a bridge arm switching signal of the three-phase half-bridge inverter circuit 105 for driving the motor by modulation according to the three-phase voltage commands Uu, Uv, and Uw.

Fig. 2 is a block diagram of an implementation of the charging state controller 101. The magnetizing state command Φ cmd is compared with the magnetizing state result Φ est estimated by the magnetizing state estimator 201 to obtain an error Φ diff, and a d-axis current command difference Did is output through the logic judger 209 and then added to the d-axis current feedback value Id to form a d-axis current command Id. This part of the operation is completed by a closed-loop controller of the variable flux permanent magnet motor.

The logic of the logic judger 209 is:

if Φ diff is greater than or equal to zero, DId ═ Idf; idf is the current stepping precision in the process of magnetization and demagnetization;

if Φ diff is less than zero, DId ═ Id; and the command is used for clearing the magnetizing and demagnetizing current.

The magnetizing state estimator 201 takes the d-axis current feedback value Id as input, and obtains the d-axis armature flux Φ dd corresponding to the current d-axis current feedback value through the current flux linkage curve 203 shown in fig. 3.Φ dd is input to the zeroth order keeper 204 for storage to calculate the difference in d-axis armature flux linkage over successive control cycles. The calculation method of the differentiator 205 is shown in formula (1):

Udi＝(Φdd-Φdd0)/T…(1)

where Φ dd0 is the d-axis armature flux linkage recorded by the zeroth order keeper 204 for the last control cycle and T is the control cycle. The difference of the flux linkage is an induced voltage term, so Udi is the induced voltage on the d-axis during the magnetization and demagnetization processes.

The magnetizing state curve 206 is shown in fig. 4, and Udi is different for different magnetizing state moments due to material saturation effect during the magnetizing and demagnetizing processes. Therefore, by performing the back-stepping of the state of magnetization Udi, the state of magnetization estimation value Φ est is obtained.

In the voltage decoupler 202, the q-axis current command Iq is set to a constant 0 in order to eliminate the d-axis rotation voltage introduced by the q-axis current and also eliminate the cross saturation effect introduced by the q-axis current. Further, the voltage decoupler 202 outputs dq-axis voltage compensation terms Udff and Uqff. Udff is the d-axis induced voltage and therefore equals Udi. Uqff is q-axis rotation coupling voltage, and the calculation method is shown as formula (2):

Uqff*＝w1*Φdd…(2)

fig. 5 is a schematic block diagram of the current control unit 102, in consideration of the dq-axis mathematical model of the variable flux permanent magnet motor, as shown in equations (3) and (4):

Ud*＝Ra*Id+dΦdd/dt-w1*Φqq…(3)

Uq*＝Ra*Iq+dΦqq/dt+w1*Φdd…(4)

wherein phi qq is a q-axis total flux linkage. d Φ dd/dt is the d-axis induced voltage, which is Udi. The q-axis current is controlled to zero by the voltage decoupler 202, so that Φ qq and its derivative d Φ qq/dt are zero.

In combination with the voltage compensation generated by the voltage decoupling device 202, the mathematical model of the flux-changing permanent magnet motor is transformed into the following equations (5) and (6):

Ud*＝Ra*Id+Udff*…(5)

Uq*＝Ra*Iq+Uqff*…(6)

the current control unit 102 performs closed-loop control of the dq-axis currents. Take d-axis current as an example. Voltage compensation terms Ra _ Id and Udff are added to the output of the PI regulator 301 to form a d-axis voltage command Ud. Ideally, the d-axis voltage command Ud is equal to the sum of the two compensation voltages. The PI regulator 301 is used to adjust the current sampling error, which causes the sampled Id to deviate from the actual Id.

As described above, the q-axis current is controlled in the same manner.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.