Multi-motor control method and device based on droop control

Abstract

The invention provides a multi-motor control method and device based on droop control, and the method enables a droop control mode, namely a distributed power balance mode, to be applied to coal mine multi-point drive belt conveyor equipment, and overcomes the defects of an existing master-slave control mode. Feedback of the actual torque measured value is referenced in the rotational speed control reference value, so that the rotational speed control reference value can reflect information of the actual torque current. When the variable-frequency driving load is too heavy, namely the torque is too large, the rotating speed control reference value can be adjusted through the rotating speed droop feedback channel, so that the torque control reference value is changed, and the purpose that the frequency converter controls power balance among the driving motors is achieved.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and in particular to a multi-motor control method and device based on droop control. Background Art

[0002] Belt conveyor is the main conveying equipment for transporting materials in coal mines. Generally, there are more than two drive motors for belt conveyors. If the belt conveyor is more than 2 kilometers long, it is often necessary to add a drive device in the middle. Therefore, the belt conveyor is a typical multi-point drive equipment. For multi-point drive equipment, it is necessary to achieve power balance between each drive motor to ensure that the output of each drive motor is the same. If the power of one motor is too large, it may cause overload and cause equipment shutdown. Generally, a frequency converter is used to control the power balance between each drive motor. Motor power P=U*I, U is voltage, I is current, and the frequency converter changes the power of the motor by changing the power frequency of the motor. When the speed of the motor is reduced, the required input current and voltage will also decrease accordingly due to the reduction of the impedance and loss inside the motor, resulting in a decrease in input power; conversely, when the speed is increased, the input power will also increase accordingly.

[0003] In the past, when completing the power balance of multi-point drive belt conveyors, it was achieved through master-slave control. That is, one inverter is set as the master, and the other inverters are slaves to follow the speed and torque. At the same time, a master control device is required to handle the data exchange of the entire system. However, this control method has the following defects and shortcomings: (1) A master device is required to centrally control the entire system, which increases the complexity of the system and its dependence on the master device. Once the master device fails, the entire system may be affected; (2) Master-slave control requires communication between devices to coordinate control, which increases the communication burden of the system and the potential risk of communication failure; (3) If a device fails, especially the host fails, the entire device needs to be stopped and reconfigured, and the response speed is slow. Summary of the invention

[0004] The present invention provides a multi-motor control method based on droop control. Through a high-voltage explosion-proof inverter product, the droop control method, a distributed power balancing method, is applied to multi-point drive belt conveyor equipment in coal mines to solve the technical problems of power imbalance, slow response speed, and defects in master-slave control of existing coal mine belt conveyors, thereby improving the reliability of the entire machine.

[0005] In one aspect, the present invention provides a multi-motor control method based on droop control, characterized in that the method comprises: Step 1: Receive the speed command issued by the PLC and generate the speed ramp output after ramp processing; Step 2: receiving the torque measurement value, adjusting the speed droop gain according to the torque measurement value, and determining the speed control reference value according to the speed ramp output and the speed droop gain; Step 3: receiving the motor speed feedback value, comparing the speed control reference value with the motor speed feedback value, and determining the comparison result; Step 4: Send the comparison result to the speed controller of the frequency converter device.

[0006] In combination with any embodiment of the present invention, the speed instruction is a target speed value issued by the PLC, which controls the speed that the frequency converter finally accelerates to.

[0007] In combination with any embodiment of the present invention, the speed ramp formula is a=Δf / Δt, wherein Δf represents the desired frequency change of the inverter, Δt represents the change time corresponding to the frequency change, and a represents the acceleration or deceleration of the inverter.

[0008] In combination with any embodiment of the present invention, the torque measurement value is sent by the motor, the motor collects the motor current measurement value, and calculates the torque measurement value based on the relationship between the torque and the current.

[0009] In combination with any embodiment of the present invention, the relationship between torque and current is T=K*I, wherein T represents torque in Newton-meters; I represents current in amperes; and K is a proportionality coefficient, also known as the torque constant of the motor, in Newton-meters / amperes.

[0010] In combination with any embodiment of the present invention, the speed droop gain is a set internal data value, and the speed control reference value is adjusted by increasing or decreasing the speed droop gain.

[0011] In combination with any embodiment of the present invention, a speed encoder is provided in the motor, and the speed encoder transmits the motor speed via a communication line.

[0012] In combination with any embodiment of the present invention, the comparison result is used to control the motor torque. If the speed control reference value is smaller than the current actual motor speed, the motor speed should be reduced to reduce the torque control reference value; if the speed control reference value is larger than the current actual motor speed, the motor speed should be increased to increase the torque control reference value.

[0013] In combination with any embodiment of the present invention, the speed controller outputs a torque control reference value according to the comparison result to adjust the speed and torque of the motor.

[0014] In one aspect, the present invention provides a multi-motor control device based on droop control, the device comprising: The receiving module is used to receive the speed command, torque measurement value, and motor speed feedback value; the speed command is sent by the host computer PLC, and the torque measurement value and motor speed feedback value are sent by the motor; The speed ramp module is used to generate a speed ramp output after performing ramp processing on the speed command; A speed droop gain module, used to adjust the speed droop gain according to the torque measurement value; A speed control module, used for determining a speed control reference value according to a speed ramp output and a speed droop gain; A comparison module is used to compare the speed control reference value with the motor speed feedback value to determine the comparison result; The sending module is used to send the comparison result.

[0015] In another aspect, the present invention provides an electronic device, the electronic device comprising a processor and a memory, wherein the memory is used to store a computer program, the computer program comprises program instructions, and the processor is configured to call the program instructions to execute some or all of the steps in the above method. In one aspect, the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by a processor, the processor executes part or all of the steps in the above method.

[0016] The multi-point driven belt conveyor control method based on the droop control high-voltage explosion-proof inverter control strategy of the present invention has the following beneficial effects: (1) Apply the droop control method, a distributed power balancing method, to multi-point driven belt conveyor equipment in coal mines. The feedback of the actual torque measurement value is quoted in the speed control reference value, so that the speed control reference value can reflect the information of the actual torque current. When the frequency conversion drive load is too heavy, that is, the torque is too large, the speed control reference value can be adjusted through the speed droop feedback channel, thereby changing the torque control reference value, and achieving the purpose of the frequency converter controlling the power balance between the various drive motors; (2) Droop control is a decentralized control and does not require a master device as the host system, which reduces single points of failure and improves system reliability and efficiency; (3) Droop control does not require complex communication and coordination mechanisms, and the system design is relatively simple, so it performs better in terms of reliability; (4) Droop control can adapt to various load changes. Once a drive device has a problem, you only need to disconnect the device. There is no need to re-install the device, and it can adapt to the changes, which makes the response faster. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0018] Figure 1 A schematic diagram of the system structure provided by the present invention; Figure 2 A schematic diagram of a multi-motor control process based on droop control provided by the present invention; Figure 3 A schematic diagram of a multi-motor control method based on droop control provided by the present invention; Figure 4 A schematic diagram of a multi-motor control device based on droop control provided by the present invention; Figure 5 A schematic structural diagram of a multi-motor control electronic device provided by the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in the field based on the embodiments in the embodiments of the present invention should fall within the scope of protection of the embodiments of the present invention.

[0020] In addition, in the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection of two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0021] In the mechanical coupling system of frequency conversion drive, there are situations where multiple frequency conversion devices drive the same motor together, or a single frequency conversion device drives the motor alone, and multiple motors are coupled together by mechanical devices such as belts and gears to drive a load together. For example, in coal mining production, there is a scenario where a belt conveyor is driven by multiple motors, and each motor is independently driven by its own frequency conversion device.

[0022] Reference Figure 1 , Figure 1The system structure provided in the embodiment of the present invention includes a host computer PLC, multiple frequency converters, multiple motors, and loads. The host computer PLC is connected to the frequency converter, the frequency converter is connected to the motor, and the motor is connected to the load. The host computer sends user commands to the frequency converter, controls the operating state of the motor through frequency conversion, and the motor finally drives the load to operate.

[0023] Optionally, an interactive interface is provided on the host computer, and the user can select and control the frequency converter through the interactive interface. Specifically, the user can select some or all of the n frequency converters, and start, stop, and speed control the selected frequency converters. After receiving the user command, the host computer sends the user command to the selected frequency converter through the connection between the host computer and the frequency converter. The connection method between the host computer PLC and the frequency converter is not limited. For example, the host computer PLC and the frequency converter are connected through optical fibers and / or cables, and the host computer PLC commands are sent to the frequency converter.

[0024] The frequency converter includes two parts: a frequency converter controller and a speed controller. The frequency converter controller receives user commands from the frequency converter from the host computer and outputs speed control-related parameters in combination with the current running state of the motor, and controls the running state of the motor through the speed controller. The frequency converter is connected to the motor, on the one hand, so that the motor sends its current running state to the frequency converter, and on the other hand, the transmission controller of the frequency converter controls the running state of the motor. The connection method between the frequency converter and the motor is not limited. For example, the frequency converter and the motor are connected through optical fibers and / or cables to transmit information between the two.

[0025] Reference Figure 2 , Figure 2 A multi-motor control process based on droop control is provided in an embodiment of the present invention. In the entire control process, the host computer PLC sends a speed command to the frequency converter controller of the frequency converter, and the frequency converter controller generates a speed ramp output after processing the speed command with a set ramp; the motor measures and obtains a torque measurement value, and sends the torque measurement value to the frequency converter controller, so that the frequency converter controller adjusts the speed droop gain according to the torque measurement value; the frequency converter controller determines a speed control reference value according to the speed ramp output and the speed droop gain; the motor obtains a motor speed feedback amount, and sends the motor speed feedback amount to the frequency converter controller, so that the frequency converter controller compares the speed control reference value and the motor speed feedback amount to determine the comparison result; the frequency converter controller sends the comparison result to the speed controller of the frequency converter device, so that the speed controller outputs a torque control reference value according to the comparison result, thereby adjusting the speed and torque of the motor.

[0026] Reference Figure 3 , Figure 3A multi-motor control method based on droop control is provided in an embodiment of the present invention. The method runs on a frequency conversion device controller, and is specifically as follows.

[0027] Step 1: Receive the speed command issued by the PLC and generate a speed ramp output after ramp processing.

[0028] The speed command is the target speed value issued by the PLC, which controls the speed that the inverter finally reaches. The formula for the speed ramp is a=Δf / Δt; where Δf: represents the expected frequency change of the inverter; Δt: represents the change time corresponding to the frequency change; a: represents the acceleration or deceleration of the inverter. In fact, the inverter accelerates linearly at a certain slope, which can be set in advance; when the inverter receives a certain speed value given by the host computer, it accelerates to the given speed value according to this slope.

[0029] Step 2: Receive the torque measurement value, adjust the speed droop gain according to the torque measurement value, and determine the speed control reference value according to the speed ramp output and the speed droop gain.

[0030] Torque and current are proportional. The current of the motor is measured by setting a current measuring device on the motor, and the torque measurement value is determined based on the measured current. The relationship between torque and current can be expressed as T=K*I, where T represents torque in Newton meters (N·m); I represents current in amperes (A); and K is the proportionality factor, also known as the torque constant of the motor, in Newton meters / ampere (N·m / A). It can be seen that when the current increases, the torque will also increase, and vice versa.

[0031] The speed droop gain is a set internal data value. The speed output is obtained by increasing or decreasing the speed droop gain to obtain a new speed control reference value. The function of the speed droop function is to quote the feedback of the actual torque measurement value in the speed control reference value, so that the new speed control reference value reflects the information of the actual torque current. When the frequency converter load is too heavy, that is, the torque is too large, the speed control reference value can be adjusted through the speed droop feedback channel. Changing the speed controller input also adjusts the torque control reference value output by it, so as to achieve the purpose of power balance between the various drive motors controlled by the frequency converter.

[0032] Step 3: receiving the motor speed feedback value, comparing the speed control reference value with the motor speed feedback value, and determining the comparison result; A speed encoder is provided in the motor, and the speed encoder is connected to the frequency converter through a communication line to send the speed of the motor to the frequency converter controller.

[0033] Step 4: Send the comparison result to the speed controller of the frequency converter device.

[0034] After receiving the comparison result, the speed controller outputs the torque control reference value according to the comparison result, and the inverter adjusts the speed and torque of the motor according to the torque control reference value. If the speed control reference value is smaller than the current actual speed of the motor, the motor speed should be reduced to reduce the torque control reference value, that is, let the motor output less; conversely, if the speed control reference value is larger than the current actual speed of the motor, the motor speed should be increased to increase the torque control reference value, that is, let the motor output more.

[0035] In this embodiment, the control core of the host computer generally adopts a programmable controller, that is, a PLC. The PLC sends a target speed value to each inverter, and the inverter accelerates according to the slope of a certain speed ramp until it reaches a given speed. In this case, certain measures need to be taken in the motor drive control strategy of the frequency converter to ensure that a certain load balance is achieved when each drive motor works together to drive the load; in addition, when the frequency converter drives the motor to change the motor speed to add or subtract load operations, the drive current of the frequency converter must also achieve a corresponding balance to avoid overcurrent in the frequency converter.

[0036] See also Figure 4 , Figure 4 A multi-motor control device based on droop control is provided in an embodiment of the present invention. It should be noted that: Figure 4 The multi-motor control device shown is used to implement the present invention Figure 3 For the convenience of explanation, only the part related to the embodiment of the present invention is shown, and the specific technical details are not disclosed. Figure 3 The embodiment shown. The multi-motor control device 400 includes: a receiving module 401, a speed ramp module 402, a speed droop gain module 403, a speed control module 404, a comparison module 405, and a sending module 406. Among them: The receiving module 401 is used to receive the speed command, the torque measurement value, and the motor speed feedback value; wherein the speed command is sent by the host computer PLC, and the torque measurement value and the motor speed feedback value are sent by the motor; The speed ramp module 402 is used to generate a speed ramp output after performing ramp processing on the speed command; A speed droop gain module 403, used to adjust the speed droop gain according to the torque measurement value; The speed control module 404 is used to determine a speed control reference value according to the speed ramp output and the speed droop gain; A comparison module 405 is used to compare the speed control reference value with the motor speed feedback value to determine a comparison result; The sending module 406 is used to send the comparison result.

[0037] See also Figure 5 , Figure 5 The schematic diagram of the structure of a multi-motor control electronic device provided by an embodiment of the present invention. Figure 5 As shown, the electronic device 500 includes: at least one processor 501 and a memory 502. Optionally, the electronic device may further include a network interface. The processor 501, the memory 502 and the network interface may exchange data, the network interface is controlled by the processor 501 to send and receive messages, the memory 502 is used to store computer programs, the computer programs include program instructions, and the processor 501 is used to execute the program instructions stored in the memory 502. The processor 501 is configured to call the program instructions to execute the above method.

[0038] The memory 502 may include a volatile memory, such as a random-access memory (RAM); the memory 502 may also include a non-volatile memory, such as a flash memory, a solid-state drive (SSD), etc.; the memory 502 may also include a combination of the above types of memory.

[0039] The processor 501 may be a central processing unit (CPU). In one embodiment, the processor 501 may also be a graphics processing unit (GPU). The processor 501 may also be a combination of a CPU and a GPU. The processor 501 may be used to call the device control application stored in the memory 502 to execute the above Figure 3 The description of the multi-motor control method in the corresponding embodiment will not be repeated here. In addition, the description of the beneficial effects of adopting the same method will not be repeated here either.

[0040] In a specific implementation, the device, processor, memory, etc. described in the embodiments of the present invention can execute the implementation described in the above method embodiments, and can also execute the implementation described in the embodiments of the present invention, which will not be repeated here.

[0041] An embodiment of the present specification further provides a computer-readable storage medium, which stores a computer program. The computer program includes program instructions, which are used to execute some or all of the steps in the above method when executed by a processor.

[0042] As for the computer-readable storage medium embodiment, since it is basically similar to the multi-motor control method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the multi-motor control method embodiment.

[0043] The above implementation methods are only used to illustrate the embodiments of the present invention, and are not limitations of the embodiments of the present invention. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the embodiments of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the embodiments of the present invention. The patent protection scope of the embodiments of the present invention should be defined by the claims.

Claims

1. A multi-motor control method based on droop control, characterized in that: The method comprises: Step 1: Receive the speed command issued by the PLC and generate the speed ramp output after ramp processing; Step 2: receiving the torque measurement value, adjusting the speed droop gain according to the torque measurement value, and determining the speed control reference value according to the speed ramp output and the speed droop gain; Step 3: receiving the motor speed feedback value, comparing the speed control reference value with the motor speed feedback value, and determining the comparison result; Step 4: Send the comparison result to the speed controller of the frequency converter device.

2. The method according to claim 1, characterized in that The speed command is the target speed value issued by the PLC, which controls the speed that the inverter finally accelerates to.

3. The method according to claim 1, characterized in that The speed ramp formula is a=Δf / Δt, where Δf represents the desired frequency change of the inverter, Δt represents the change time corresponding to the frequency change, and a represents the acceleration or deceleration of the inverter.

4. The method according to claim 1, characterized in that The torque measurement value is sent by the motor, the motor collects the motor current measurement value, and calculates the torque measurement value based on the relationship between the torque and the current.

5. The method according to claim 4, characterized in that The relationship between torque and current is T=K*I, where T represents torque in Newton meters; I represents current in amperes; and K is the proportionality coefficient, also known as the torque constant of the motor, in Newton meters / amperes.

6. The method according to claim 1, characterized in that The speed droop gain is a set internal data value, and the speed control reference value is adjusted by increasing or decreasing the speed droop gain.

7. The method according to claim 1, characterized in that A speed encoder is provided in the motor, and the speed encoder transmits the motor speed through a communication line.

8. The method according to claim 1, characterized in that The comparison result is used to control the motor torque. If the speed control reference value is smaller than the current actual motor speed, the motor speed should be reduced to reduce the torque control reference value; if the speed control reference value is larger than the current actual motor speed, the motor speed should be increased to increase the torque control reference value.

9. The method according to claim 1, characterized in that: The speed controller outputs a torque control reference value according to the comparison result to adjust the speed and torque of the motor.

10. A multi-motor control device based on droop control, characterized in that: The device comprises: The receiving module is used to receive the speed command, torque measurement value, and motor speed feedback value; the speed command is sent by the host computer PLC, and the torque measurement value and motor speed feedback value are sent by the motor; The speed ramp module is used to generate a speed ramp output after performing ramp processing on the speed command; A speed droop gain module, used to adjust the speed droop gain according to the torque measurement value; A speed control module, used for determining a speed control reference value according to a speed ramp output and a speed droop gain; A comparison module is used to compare the speed control reference value with the motor speed feedback value to determine the comparison result; The sending module is used to send the comparison result.

11. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory is used to store a computer program, the computer program comprises program instructions, and the processor is configured to call the program instructions to execute the method according to any one of claims 1 to 9.

12. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by a processor, the processor is caused to perform the method according to any one of claims 1 to 9.

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