WO2022267378A1

WO2022267378A1 - Low-speed operation control method for switched reluctance motor, and switched reluctance motor

Info

Publication number: WO2022267378A1
Application number: PCT/CN2021/137227
Authority: WO
Inventors: 何舟; 孙琍
Original assignee: 深圳拓邦股份有限公司
Priority date: 2021-06-23
Filing date: 2021-12-10
Publication date: 2022-12-29
Also published as: CN113612426A

Abstract

The present invention relates to a low-speed operation control method for a switched reluctance motor, and a switched reluctance motor. The method comprises: acquiring a real-time rotational speed of a switched reluctance motor; determining a reference current according to the real-time rotational speed and a set rotational speed; obtaining a control parameter of low-speed operation of the switched reluctance motor according to the reference current; and according to the control parameter, controlling the switched reluctance motor to operate. According to the present invention, the reference current is determined on the basis of the real-time rotational speed and the set rotational speed of the switched reluctance motor, and the control parameter of the low-speed operation of the switched reluctance motor is obtained according to the reference current, so that low-speed operation control is performed on the switched reluctance motor according to the obtained control parameter, so as to control the switched reluctance motor to operate stably in a low-speed state, thereby improving the stability and reliability of the switched reluctance motor.

Description

Switched reluctance motor low-speed operation control method, switched reluctance motor

technical field

The invention relates to the technical field of motors, and more specifically, to a low-speed operation control method of a switched reluctance motor and a switched reluctance motor.

Background technique

The existing switched reluctance motor has a wide speed range, generally up to 40rpm~1200rpm. However, due to the wide range adjustment of the switched reluctance motor, when it is controlled at low speed, due to the low power, the switched reluctance motor Unstable at low speeds with poor stability control.

technical problem

The technical problem to be solved by the present invention is to provide a low-speed operation control method of a switched reluctance motor and a switched reluctance motor in view of the above-mentioned defects of the prior art.

technical solution

The technical solution adopted by the present invention to solve the technical problem is: to construct a method for controlling the low-speed operation of a switched reluctance motor, comprising the following steps:

Obtain the real-time speed of the switched reluctance motor;

determining a reference current according to the real-time rotational speed and the set rotational speed;

Obtaining control parameters for the low-speed operation of the switched reluctance motor according to the reference current;

The operation of the switched reluctance motor is controlled according to the control parameters.

In the method for controlling the low-speed operation of the switched reluctance motor according to the present invention, the determining the reference current according to the real-time rotation speed and the set rotation speed includes:

making a difference between the set speed and the real-time speed to obtain a difference between the set speed and the real-time speed;

According to the difference between the set rotation speed and the real-time rotation speed, a preset adjustment algorithm is used for calculation to obtain the reference current.

In the low-speed operation control method of the switched reluctance motor according to the present invention, the preset adjustment algorithm is any one or more of incremental PI adjustment algorithm, positional PI algorithm and PID algorithm.

In the method for controlling the low-speed operation of the switched reluctance motor according to the present invention, the obtaining of the control parameters for the low-speed operation of the switched reluctance motor according to the reference current includes:

determining a current deviation value according to the reference current;

A current upper limit and a current lower limit are determined according to the current deviation value and the reference current.

A reference duty cycle for controlling the switched reluctance motor is determined according to the reference current.

According to the reference current, the turn-on angle and turn-off angle of each phase of the switched reluctance motor are obtained.

In the method for controlling the low-speed operation of the switched reluctance motor according to the present invention, the controlling the operation of the switched reluctance motor according to the control parameters includes:

Obtaining the real-time conduction current of the switched reluctance motor;

Comparing the real-time conduction current with the current upper limit and the current lower limit;

According to the comparison result, the currently on-phase of the switched reluctance motor is controlled to be turned off or the currently off-phase of the switched reluctance motor is controlled to be turned on.

In the method for controlling low-speed operation of switched reluctance motors according to the present invention, the comparison results include: the real-time conduction current is greater than the current upper limit, or the real-time conduction current is smaller than the current lower limit value.

In the method for controlling the low-speed operation of the switched reluctance motor according to the present invention, the controlling the current conducting phase of the switched reluctance motor to turn off or controlling the current closing phase of the switched reluctance motor to conduct according to the comparison result includes:

If the real-time conduction current is greater than the current upper limit value, the current conduction phase of the switched reluctance motor is controlled to be turned off.

If the real-time conduction current is less than the current lower limit value, the currently closed phase of the switched reluctance motor is controlled to conduct.

According to the reference duty cycle, the duty cycle of the current conduction phase of the switched reluctance motor is controlled.

The present invention also provides a switched reluctance motor, including: a detection device and a controller;

The detection device is used to detect the rotational speed of the switched reluctance motor and output a photoelectric switch signal;

The controller is used to implement the above-mentioned method for controlling the low-speed operation of the switched reluctance motor.

Beneficial effect

Implementing the switching reluctance motor low-speed operation control method and the switched reluctance motor of the present invention have the following beneficial effects: including: obtaining the real-time rotational speed of the switched reluctance motor; determining the reference current according to the real-time rotational speed and the set rotational speed; obtaining the switching speed according to the reference current The control parameters of the low-speed operation of the reluctance motor; the operation of the switched reluctance motor is controlled according to the control parameters. The present invention determines the reference current based on the real-time rotational speed and the set rotational speed of the switched reluctance motor, and obtains the control parameters of the low-speed operation of the switched reluctance motor according to the reference current, thereby controlling the low-speed operation of the switched reluctance motor according to the obtained control parameters , so as to control the stable operation of the switched reluctance motor at a low speed and improve the stability and reliability of the switched reluctance motor.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

FIG. 1 is a schematic flowchart of a method for controlling low-speed operation of a switched reluctance motor provided by an embodiment of the present invention;

Fig. 2 is a schematic diagram of the current waveform of the current chopping control;

Fig. 3 is a schematic diagram of a current waveform of voltage chopping control;

Fig. 4 is a schematic diagram of current waveforms when conduction angles are different;

Fig. 5 is a schematic diagram of current waveforms when the turn-off angle is different;

Fig. 6 is a schematic diagram of a motor drive circuit;

Fig. 7 is a schematic diagram of the relative position and sector division of the winding inductance.

BEST MODE FOR CARRYING OUT THE INVENTION

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described in detail with reference to the accompanying drawings.

In order to solve the problem of unstable operation of switched reluctance motors at low speeds, the present invention provides a method for controlling the low-speed operation of switched reluctance motors. Combined with the method, the switched reluctance motor can run stably at low speed. In addition, the method can also improve the response speed of the switched reluctance motor, so that the switched reluctance motor can quickly respond to load changes.

Specifically, refer to FIG. 1 , which is a schematic flowchart of an alternative embodiment of a method for controlling low-speed operation of a switched reluctance motor provided by the present invention. Optionally, the method for controlling the low-speed operation of the switched reluctance motor can be applied to include but not limited to four-phase switched reluctance motors, six-phase switched reluctance motors, eight-phase switched reluctance motors, and the like. For example, as shown in FIG. 6 , it is a drive circuit for a four-phase switched reluctance motor. In Figure 6, phases A and C share the upper bridge (Q1), and phases B and D share the upper bridge (Q5). When phase A needs to be turned on, control Q1 and Q3 to be turned on; when phase C needs to be turned on, control Q1, Q4 is turned on; when phase B needs to be turned on, Q5 and Q6 are controlled to turn on; when phase D needs to be turned on, Q5 and Q2 are controlled to turn on. Among them, in Figure 6, R1 is the current detection resistor. By detecting the current flowing through R1, the conduction current corresponding to the open phase can be detected.

Specifically, as shown in Figure 1, the low-speed operation control method of the switched reluctance motor is characterized in that it includes the following steps:

Step S101, acquiring the real-time rotational speed of the switched reluctance motor.

Optionally, the real-time rotational speed of the switched reluctance motor may be detected by an existing conventional method.

Step S102, determining a reference current according to the real-time rotational speed and the set rotational speed.

In some embodiments, determining the reference current according to the real-time speed and the set speed includes: making a difference between the set speed and the real-time speed to obtain the difference between the set speed and the real-time speed; according to the difference between the set speed and the real-time speed, using The preset adjustment algorithm is used for calculation to obtain the reference current. Optionally, the preset adjustment algorithm is any one or more of incremental PI adjustment algorithm, positional PI algorithm and PID algorithm. PID is a linear control algorithm that adjusts the output according to the deviation from the setpoint and feedback. P means Proportion, I means Integral, and D means Differential. The PID control formula is as follows:

(1).

(1) In the formula, Kp------proportional gain (proportional coefficient); Tt------integral time constant; Td------differential time constant; u(t)------ Output; e(t) ----- deviation.

Discretizing formula (1) can get:

(2).

(2) where,

------Integral coefficient;

------differential coefficient; u(k)-------kth output; e(k)-------kth deviation.

It can be seen from formula (2) that the output of the proportional part is proportional to the deviation, that is, when there is a deviation in the system, there is a proportional output, which can quickly respond to reduce the deviation, but the pure proportional control requires the existence of the deviation to maintain a certain output. Therefore, there must be a steady-state error in pure proportional control, and integral control needs to be introduced;

The existence of the integral control function is related to the existence time of the deviation. As long as there is a deviation in the system, the integral control will continue to work, integrate the input deviation, make the output change continuously, and produce a control effect to reduce the deviation. In the case of sufficient integral time, the static error can be completely eliminated, and the integral control function will remain unchanged at this time. Therefore, the proportional + integral (PI) controller can make the system have no steady-state error after entering the steady state. Although the introduction of integral control can eliminate the steady-state error, it reduces the response speed of the system, especially for the system with large inertia It is difficult to obtain better dynamic adjustment quality by only using PI controller, and the system will produce large overshoot and oscillation. At this time, differential control can be introduced. Differential control adjusts the output in advance according to the variation trend of the deviation, thereby speeding up the response speed of the system and reducing the adjustment time, but the differential control is a predictive control. If the proportion of the differential action is too large (wechat coefficient is large), it will The system's anti-interference ability will be reduced.

Formula (2) is a discretized formula, and there is a problem in it: the integral part needs to continuously accumulate the deviation, which requires a large storage space. Therefore, according to formula (1), the incremental formula can be deduced as follows:

(3).

The use of formula (3) does not need to accumulate deviations, which can greatly reduce the storage space requirements. The motor is a control object with small inertia. Therefore, in the embodiment of the present invention, the incremental PI adjustment algorithm is preferably used. Among them, the input deviation is the difference between the set speed and the real speed, and the incremental value of the reference current can be obtained by the following formula:

(4).

(4) In the formula, △ I _ref ( k ) is the reference current incremental value.

(5).

(5) In the formula, I _ref ( k ) is the reference current.

Step S103 , obtaining control parameters for the low-speed operation of the switched reluctance motor according to the reference current.

In some embodiments, obtaining the control parameters for the low-speed operation of the switched reluctance motor according to the reference current includes: determining a current deviation value according to the reference current; determining a current upper limit value and a current lower limit value according to the current deviation value and the reference current.

Specifically, after the reference current is calculated, an allowable current deviation value is set according to the reference current, and then an upper current limit value and a current lower limit value are calculated based on the obtained current deviation value.

For example, if the calculated reference current is 1000mA, at this time, the reference current is relatively large, and the allowable current deviation value can be set to be relatively large. For example, if it can be set to 200mA, the current upper limit is 1200mA, and the current lower 800mA. If the reference current is 200mA, at this time, the reference current is small, and the allowable current deviation value can be set to be relatively small. For example, it can be set to 50mA, the upper limit of the current is 250mA, and the lower limit of the current is 150mA.

In some embodiments, obtaining the control parameters for the low-speed operation of the switched reluctance motor according to the reference current includes: determining a reference duty cycle for controlling the switched reluctance motor according to the reference current.

It can be understood that the duty cycle is used to adjust the current rising speed. Therefore, after the reference duty cycle is calculated through the calculated reference current, the switched reluctance motor can be performed using the calculated reference duty cycle. Duty cycle control to regulate the rate of current rise. For example, when the reference current is 1000mA, the current is relatively large, and the rate of current rise can be set accordingly. For example, the reference duty cycle can be set to 100%, that is, the opened phase is completely turned on. At this time, the current rise rate is the highest. ; If the reference current is 200mA, the current is small, and the current rise rate also needs to be reduced. Therefore, the duty cycle can be reduced accordingly, for example, it can be set to 20%, which reduces the current rise speed and makes the current control more accurate.

In some embodiments, obtaining the control parameters for the low-speed operation of the switched reluctance motor according to the reference current includes: obtaining the conduction angle and the turn-off angle of each phase of the switched reluctance motor according to the reference current.

Step S104, controlling the operation of the switched reluctance motor according to the control parameters.

In some embodiments, controlling the operation of the switched reluctance motor according to the control parameters includes: obtaining the real-time conducting current of the switched reluctance motor; comparing the real-time conducting current with the current upper limit value and the current lower limit value; controlling the switch according to the comparison result The currently on phase of the reluctance motor is turned off or the currently off phase of the switched reluctance motor is controlled to be turned on.

Optionally, the comparison result includes: the real-time conduction current is greater than the upper limit value of the current, or the real-time conduction current is smaller than the lower limit value of the current.

Wherein, controlling the current conduction phase of the switched reluctance motor to turn off or controlling the current closed phase of the switched reluctance motor to conduct according to the comparison result includes: if the real-time conduction current is greater than the current upper limit value, then controlling the current conduction phase of the switched reluctance motor Pass phase off. Alternatively, if the real-time conduction current is less than the lower limit value of the current, the currently closed phase of the switched reluctance motor is controlled to conduct.

Specifically, as shown in FIG. 6, the real-time conduction current of the switched reluctance motor can be obtained by detecting the current flowing through the current-sensing resistor, and the real-time conduction current is compared with the current upper limit value and the current lower limit value respectively, If the real-time conduction current is greater than the current upper limit, control the corresponding switch to close to control the current conduction phase to close; as shown in Figure 6, if the current conduction phase is A phase or C phase, then control Q1 to close; If the current conduction phase is B phase or D phase, control Q5 to turn off. If the real-time conduction current is less than the lower limit value of the current, control the corresponding switch to conduct to control the conduction of the currently closed phase; as shown in Figure 6, if the current closed phase is A phase or C phase, control Q1 to conduct ; If the current closed phase is B phase or D phase, control Q5 to conduct.

As shown in Figure 2, when the real-time conduction current is greater than the upper limit of the current, the control Q1 is turned off to limit the upper limit of the current; Fluctuates within the set range, so that the positive and negative torque generated can be controlled.

In some embodiments, controlling the operation of the switched reluctance motor according to the control parameters includes: controlling the duty cycle of the currently conducting phase of the switched reluctance motor according to a reference duty cycle.

Specifically, as shown in Figure 6, if the current conduction phase is A phase or C phase, the duty cycle when Q1 is turned on is controlled according to the calculated reference duty cycle to adjust the current rising speed; if the current conduction phase If the on-phase is B-phase or D-phase, according to the calculated reference duty ratio, the duty ratio when Q5 is turned on is controlled to adjust the current rising speed.

As shown in Figure 3, the average voltage is adjusted by adjusting the duty cycle of Q1 or Q5 when it is turned on, and then the current is changed to adjust the speed of current rise, so that the current chopping control accuracy is higher, such as a smaller reference current , due to the large voltage, the current rising speed is fast, and it is difficult to control the current accurately. At this time, the current rising speed can be limited by reducing the duty cycle, thereby improving the accuracy of current control; when the load is large and the reference current is large , can increase the duty cycle to increase the current rising speed, improve the current response speed, and then improve the motor's response speed to load changes.

In some embodiments, controlling the operation of the switched reluctance motor according to the control parameters includes: controlling the conduction moment (conduction angle) and the turn-off moment (turn-off angle) of each phase of the switched reluctance motor according to the determined conduction angle and turn-off angle Angle) and then control the conduction interval of each phase, so as to generate a suitable average torque.

As shown in Figure 4 and Figure 5, by adjusting the conduction angle and turn-off angle, the current waveform and the relative position of the current waveform and the winding inductance waveform can be changed, thereby controlling the operation of the motor.

As shown in FIG. 7 , it is a schematic diagram of the relative position and sector division of the winding inductance. Among them, the division of sectors can be detected by two photoelectric switches installed on the motor. According to the running direction (forward rotation) of the motor in the figure, taking phase A as an example for illustration, there are four sectors in the inductor in one cycle, respectively. It is the inductance rise area (1), the inductance maximum area (0), the inductance drop area (2), and the inductance minimum area (3). Among them, in Figure 7, linear processing is done for the convenience of explanation. In fact, the inductance still changes between the maximum area and the minimum area, and the inductance rise and inductance drop are not completely linear. Area, that is, sector 1 corresponds to the area where the phase A inductance increases, the area where the phase B inductance is maximum, the area where the phase C inductance decreases, and the area where the phase D inductance is minimum. According to the working principle of the switched reluctance motor, we still take phase A as an example for illustration. During the inductance rising stage (sector 1, sector 0 and sector 3), current flows to generate positive torque, and in the inductance falling stage (Sector 2, Sector 0, and Sector 3) There is current flowing through to generate negative torque, therefore, it can be controlled by adjusting the conduction time (conduction angle) and the turn-off time (turn-off angle) of phase A The conduction interval of each phase produces a suitable average torque to make the motor run smoothly. For example, in the case of no load, in order to stabilize the speed, more negative torque will be generated. In the case of heavy load, phase A is only conducted in the positive torque range, and the conduction angle and cut-off angle vary with the load. And change, wherein, the on-off of Q3, Q4, Q6 and Q2 corresponds to the on-off of phase A, phase B, phase C and phase D respectively.

Furthermore, in order to make the switched reluctance motor run more stably, the present invention also introduces current chopping control (that is, controlling the operation of the switched reluctance motor according to the set current upper and lower limit values) and voltage chopping control (that is, according to duty cycle controls switched reluctance motor operation).

The present invention combines the three driving modes of current chopping control, voltage chopping control and conduction position angle control, so that the switched reluctance motor can run stably at low speed, and can also quickly respond to the change of the load, effectively improving the switching reluctance motor. stability and reliability.

The detecting device is used for detecting the rotating speed of the switched reluctance motor and outputting a photoelectric switch signal.

The controller is also used to implement the low-speed operation control method of the switched reluctance motor disclosed in the embodiment of the present invention. Wherein, the controller calculates the real-time rotational speed of the switched reluctance motor according to the received photoelectric switch signal. Optionally, the detection device may be a photoelectric switch.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other. As for the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and for the related part, please refer to the description of the method part.

Professionals can further realize that the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software or a combination of the two. In order to clearly illustrate the possible For interchangeability, in the above description, the composition and steps of each example have been generally described according to their functions. Whether these functions are executed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be regarded as exceeding the scope of the present invention.

The steps of the methods or algorithms described in connection with the embodiments disclosed herein may be directly implemented by hardware, software modules executed by a processor, or a combination of both. Software modules can be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other Any other known storage medium.

The above embodiments are only to illustrate the technical conception and characteristics of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and cannot limit the protection scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the claims of the present invention shall fall within the scope of the claims of the present invention.

Claims

A method for controlling low-speed operation of a switched reluctance motor, comprising the following steps:

Obtain the real-time speed of the switched reluctance motor;

determining a reference current according to the real-time rotational speed and the set rotational speed;

Obtaining control parameters for the low-speed operation of the switched reluctance motor according to the reference current;

The operation of the switched reluctance motor is controlled according to the control parameters.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 1, wherein said determining the reference current according to the real-time rotational speed and the set rotational speed comprises:

making a difference between the set speed and the real-time speed to obtain a difference between the set speed and the real-time speed;

According to the difference between the set rotation speed and the real-time rotation speed, a preset adjustment algorithm is used for calculation to obtain the reference current.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 2, wherein the preset adjustment algorithm is any one or more of an incremental PI adjustment algorithm, a positional PI algorithm and a PID algorithm.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 1, wherein the obtaining of the control parameters for the low-speed operation of the switched reluctance motor according to the reference current comprises:

determining a current deviation value according to the reference current;

A current upper limit and a current lower limit are determined according to the current deviation value and the reference current.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 1, wherein the obtaining of the control parameters for the low-speed operation of the switched reluctance motor according to the reference current comprises:

A reference duty cycle for controlling the switched reluctance motor is determined according to the reference current.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 1, wherein the obtaining of the control parameters for the low-speed operation of the switched reluctance motor according to the reference current comprises:

According to the reference current, the turn-on angle and turn-off angle of each phase of the switched reluctance motor are obtained.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 4, wherein the controlling the operation of the switched reluctance motor according to the control parameters comprises:

Obtaining the real-time conduction current of the switched reluctance motor;

Comparing the real-time conduction current with the current upper limit and the current lower limit;

According to the comparison result, the currently on-phase of the switched reluctance motor is controlled to be turned off or the currently off-phase of the switched reluctance motor is controlled to be turned on.
The method for controlling low-speed operation of a switched reluctance motor according to claim 7, wherein the comparison result includes: the real-time conduction current is greater than the current upper limit value, or the real-time conduction current is less than the set The lower limit value of the current mentioned above.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 8, wherein, according to the comparison result, controlling the current conduction phase of the switched reluctance motor to be closed or controlling the current close phase of the switched reluctance motor Conduction includes:

If the real-time conduction current is greater than the current upper limit value, the current conduction phase of the switched reluctance motor is controlled to be turned off.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 8, wherein, according to the comparison result, controlling the current conduction phase of the switched reluctance motor to be closed or controlling the current close phase of the switched reluctance motor Conduction includes:

If the real-time conduction current is less than the current lower limit value, the currently closed phase of the switched reluctance motor is controlled to conduct.
The method for controlling the low-speed operation of the switched reluctance motor according to claim 5, wherein the controlling the operation of the switched reluctance motor according to the control parameters comprises:

According to the reference duty cycle, the duty cycle of the current conduction phase of the switched reluctance motor is controlled.
A switched reluctance motor, characterized by comprising: a detection device and a controller;

The detection device is used to detect the rotational speed of the switched reluctance motor and output a photoelectric switch signal;

The controller is used to execute the method for controlling the low-speed operation of the switched reluctance motor according to any one of claims 1-11.