CN114744681A - Control method and device for grid-connected operation of electric motor, and grid-connected operation control system - Google Patents

Abstract

The embodiments of the present application provide a control method, device and grid-connected operation control system for a motor, wherein when the first switch, the second switch and the third switch are all off, if an instruction sending device is received The start-up command sent to control the second switch and the third switch to close, connect the asynchronous start permanent magnet synchronous motor and the power grid to the inverter, and when the operation mode carried in the start-up command is the grid-connected mode, the asynchronous start is controlled based on the frequency converter. When the operating frequency of the permanent magnet synchronous motor reaches the target frequency carried in the speed control command, and then it is determined that the maximum voltage deviation between the power grid and the inverter is less than the preset voltage threshold, the third switch is controlled to open and the first switch is closed. In order to integrate the asynchronous start permanent magnet synchronous motor into the grid operation. The application can connect the motor to the grid through the frequency converter, thereby overcoming the difficulty of starting the motor directly connected to the grid and the unsafe problems caused by over-torque and low voltage during operation.

Description

Grid-connected operation control method, device and grid-connected operation control system for electric motors

technical field

The invention relates to the technical field of motor operation, in particular to a control method and device for grid-connected operation of a motor and a grid-connected operation control system.

Background technique

Asynchronous start permanent magnet synchronous motors are widely used in grid-connected fixed-speed drive scenarios due to their high efficiency and high power density. In actual operation, the asynchronous start permanent magnet synchronous motor often runs in the way of direct grid connection. However, the excessive starting current of the asynchronous start permanent magnet synchronous motor in the process of direct grid connection will cause the capacity of the power supply transformer to increase and the torque to be excessive. Large, easy to damage couplings and shaft extension keys and other connecting mechanisms, and when driving large inertia loads, the start-up process is long or the synchronization cannot be switched to generate a large current that lasts for a long time, resulting in excessive heating and loss of magnetism of the rotor permanent magnet, etc. In addition, after the asynchronous start permanent magnet synchronous motor is connected to the grid, once there is an excessive load torque or a short-term low voltage of the grid, the step will be lost, resulting in excessive current and torque, causing the rotor to fail. Magnetic and mechanical failures can also cause overheating damage if the power is not disconnected in time.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a control method, device and grid-connected operation control system for a motor to be connected to the grid, so that the asynchronous start permanent magnet synchronous motor can be started by a frequency converter, which overcomes the direct effect of the asynchronous start permanent magnet synchronous motor. Difficulty starting grid connection and unsafe problems caused by over-torque and low voltage during operation.

In a first aspect, an embodiment of the present invention provides a method for controlling the grid-connected operation of an electric motor, wherein the method is applied to a controller in a grid-connected operation control system, and the grid-connected operation control system further includes an asynchronous motor that is communicatively connected to the controller. Start the permanent magnet synchronous motor, the frequency converter, the first switch, the second switch and the third switch, wherein the asynchronous start permanent magnet synchronous motor is connected to the grid through the first switch, the frequency converter is connected to the grid through the second switch, and the frequency converter is connected to the grid through the second switch. The third switch is connected to the asynchronous start permanent magnet synchronous motor, and the asynchronous start permanent magnet synchronous motor is a motor with a rotor with a damping cage; the method includes: when the first switch, the second switch and the third switch are all disconnected, based on The power-on command sent by the received command sending device controls the second switch and the third switch to close, so as to connect the asynchronous start permanent magnet synchronous motor and the power grid to the frequency converter; determine whether the operation mode carried in the power-on command is the grid-connected mode; If it is, send a speed control command to the inverter to trigger the inverter to control the running frequency of the permanent magnet synchronous motor to start asynchronously to the target frequency carried in the speed control command; determine the maximum voltage deviation between the power grid and the inverter; When the voltage deviation is less than the preset voltage threshold and the operating frequency of the asynchronous start permanent magnet synchronous motor reaches the target frequency, the third switch is controlled to open and the first switch is closed, so as to integrate the asynchronous start permanent magnet synchronous motor into the grid for operation.

The method further includes: if it is judged that the operating mode is the inverter control mode, sending a speed command or a torque command to the inverter to trigger the inverter to control the asynchronous start of the permanent magnet synchronous motor based on the speed command or the torque command.

Before determining the maximum voltage deviation between the power grid and the frequency converter, the method further includes: judging whether the first shutdown command sent by the command sending device is received; if so, triggering the frequency converter to stop running, and sequentially turning off the third switch and the second switch; if not, perform the steps of determining the maximum voltage deviation between the grid and the frequency converter.

The method further includes: if the maximum voltage deviation is not less than the preset voltage threshold and/or the operating frequency of the asynchronously started permanent magnet synchronous motor does not reach the target frequency, executing the step of judging whether the first shutdown command sent by the command sending device is received.

The above-mentioned grid-connected operation control system further includes a first voltage sensor and a second voltage sensor that are communicatively connected to the controller; the step of determining the maximum voltage deviation between the power grid and the frequency converter includes: receiving the first voltage sensor of the power grid collected by the first voltage sensor. a three-phase voltage instantaneous value, and a second three-phase voltage instantaneous value of the output of the inverter collected by the second voltage sensor; three phase sequences are calculated based on the first three-phase voltage instantaneous value and the second three-phase voltage instantaneous value, respectively The corresponding voltage deviation; the largest voltage deviation among the three voltage deviations is determined as the maximum voltage deviation.

The above-mentioned grid-connected operation control system further includes a current sensor connected in communication with the controller; the method further includes: receiving the instantaneous value of the three-phase input current of the asynchronous start permanent magnet synchronous motor collected by the current sensor; and determining the instantaneous value of the three-phase input current. Whether the instantaneous value of the maximum current is greater than the preset current threshold; if it is, open the first switch, close the third switch, and send a current cut-in command to the inverter to trigger the inverter to cut into the current cut-in command to the asynchronous start permanent magnet synchronous motor The driving current carried, and the step of sending a speed control command to the inverter to trigger the inverter to control the running frequency of the asynchronous start permanent magnet synchronous motor to the target frequency carried in the speed control command.

Before receiving the instantaneous value of the three-phase input current of the asynchronous start permanent magnet synchronous motor collected by the current sensor, the method further includes: judging whether the second shutdown command sent by the command sending device is received; if so, sequentially disconnecting the first switches and the second switch; if not, perform the step of receiving the instantaneous value of the three-phase input current of the asynchronous start permanent magnet synchronous motor collected by the current sensor.

The above method further includes: if the maximum current instantaneous value of the three-phase input current instantaneous values is less than or equal to the preset current threshold value, executing the step of judging whether a second shutdown command sent by the command sending device is received.

In a second aspect, an embodiment of the present invention further provides a control device for the grid-connected operation of a motor, wherein the control device is applied to a controller in a grid-connected operation control system, and the grid-connected operation control system further includes a The asynchronous start permanent magnet synchronous motor, the frequency converter, the first switch, the second switch and the third switch, wherein the asynchronous start permanent magnet synchronous motor is connected to the grid through the first switch, the frequency converter is connected to the grid through the second switch, and the frequency converter The asynchronous start permanent magnet synchronous motor is connected to the asynchronous start permanent magnet synchronous motor through the third switch, and the asynchronous start permanent magnet synchronous motor is a motor with a rotor with a damping cage; the above-mentioned control device includes: a first control module, which is used for the first switch, the second switch and the third switch. When the switches are all off, the second switch and the third switch are controlled to be closed based on the power-on command sent by the received command sending device, so as to connect the asynchronous start permanent magnet synchronous motor and the power grid with the frequency converter; the judgment module is used to judge Whether the running mode carried in the start-up command is grid-connected mode; the sending module is used to send a speed control command to the inverter if the judgment module judges it to be yes, to trigger the inverter to control the running frequency of the permanent magnet synchronous motor to start asynchronously to The target frequency carried in the speed control command; the determination module is used to determine the maximum voltage deviation between the power grid and the inverter; the second control module is used to asynchronously start the permanent magnet synchronous motor if the maximum voltage deviation is less than the preset voltage threshold The operating frequency of the motor reaches the target frequency, and the third switch is controlled to open and the first switch to be closed, so as to integrate the asynchronous start permanent magnet synchronous motor into the power grid for operation.

In a third aspect, an embodiment of the present invention further provides a grid-connected operation control system, wherein the grid-connected operation control system includes a controller, an asynchronous start permanent magnet synchronous motor, a frequency converter, and a first switch that are communicatively connected to the controller. , a second switch and a third switch, wherein the asynchronous start permanent magnet synchronous motor is connected to the grid through the first switch, the frequency converter is connected to the grid through the second switch, and the frequency converter is connected to the asynchronous start permanent magnet synchronous motor through the third switch, The asynchronous start permanent magnet synchronous motor is a motor with a damping cage in the rotor; the controller is used to implement the above-mentioned control method for the motor connected to the grid.

The embodiments of the present invention have brought the following beneficial effects:

Embodiments of the present application provide a control method, device, and grid-connected operation control system for a motor, wherein when the first switch, the second switch, and the third switch are all turned off, if an instruction sending device is received After sending the power-on command, control the second switch and the third switch to close, connect the asynchronous start permanent magnet synchronous motor and the power grid to the inverter, and when it is judged that the operation mode carried in the power-on command is the grid-connected mode, the inverter is sent to the frequency converter. The inverter sends a speed control command to trigger the inverter to control the running frequency of the permanent magnet synchronous motor to start asynchronously to the target frequency carried in the speed control command; further, after it is determined that the maximum voltage deviation between the power grid and the inverter is less than the preset voltage When the threshold value and the operating frequency of the asynchronous start permanent magnet synchronous motor reaches the target frequency, the third switch is controlled to open and the first switch is closed, so as to integrate the asynchronous start permanent magnet synchronous motor into the grid for operation. The present application can connect the asynchronous start permanent magnet synchronous motor to the grid through the frequency converter, thereby overcoming the difficulty of directly connecting the asynchronous start permanent magnet synchronous motor to the grid and the unsafe problems caused by over-torque and low voltage during operation.

Further, in the above manner, the asynchronous start permanent magnet synchronous motor is a motor with a rotor with a damping cage, which mainly plays a damping role, thereby effectively ensuring the dynamic stability of the motor during grid-connected operation.

Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the description and drawings.

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below, and are described in detail as follows in conjunction with the accompanying drawings.

Description of drawings

In order to illustrate the specific embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the specific embodiments or the prior art. Obviously, the accompanying drawings in the following description The drawings are some embodiments of the present invention, and for those skilled in the art, other drawings can also be obtained from these drawings without creative efforts.

1 is a schematic structural diagram of a grid-connected operation control system provided by an embodiment of the present invention;

2 is a flowchart of a control method for a grid-connected motor provided by an embodiment of the present invention;

3 is a flowchart of another method for controlling the grid-connected operation of an electric motor provided by an embodiment of the present invention;

4 is a schematic structural diagram of another grid-connected operation control system provided by an embodiment of the present invention;

FIG. 5 is a flowchart of another method for controlling the grid-connected operation of an electric motor according to an embodiment of the present invention.

icon:

100-controller; 101-asynchronous start permanent magnet synchronous motor; 102-frequency converter; K1-first switch; K2-second switch; K3-third switch; CV1-first voltage sensor; CV2-second voltage sensor ; CT - current sensor.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. example. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

Considering that the existing asynchronous start permanent magnet synchronous motor may have difficulty in starting and unsafe problems caused by over-torque and low voltage during operation in the process of direct grid-connected start-up operation; based on this, an embodiment of the present invention provides a The control method, the device and the grid-connected operation control system for the electric motor can connect the asynchronous start permanent magnet synchronous motor to the grid through the frequency converter, thereby overcoming the difficulty of the asynchronous start permanent magnet synchronous motor directly connected to the grid and the over-rotation during operation. Unsafe problems caused by torque and low voltage.

In order to facilitate the understanding of this embodiment, the control method for the grid-connected operation of the electric motor provided by the embodiment of the present invention is first introduced in detail below. The controller in the grid-connected operation control system, as shown in FIG. 1 , includes the above-mentioned controller 100 , an asynchronous start permanent magnet synchronous motor 101 , a frequency converter 102 , an asynchronous start permanent magnet synchronous motor 101 , a frequency converter 102 , a The first switch K1, the second switch K2 and the third switch K3, wherein the asynchronous start permanent magnet synchronous motor 101 is connected to the grid through the first switch K1, the frequency converter 102 is connected to the grid through the second switch K2, and the frequency converter 102 is connected to the grid through the first switch K2. The three switches K3 are connected to the asynchronous start permanent magnet synchronous motor 101 , and the asynchronous start permanent magnet synchronous motor is a motor with a damping cage in the rotor. The dotted line in FIG. 1 represents the communication connection.

The power grid in Figure 1 is a three-phase power grid, and the three-phase power grid can be represented by U, V, and W. The first switch, the second switch, and the third switch can be mechanical switches or electronic switches, which can be selected according to actual needs. Here Not limited.

The above damping cage can be made of cast aluminum, or cast copper, or copper strips, or aluminum strips and has the same structure as the squirrel cage of the cage-type asynchronous motor rotor, or it can be made of aluminum wire or copper wire and winding. The closed coil structure is the same as the rotor winding of the induction motor. The shape of the damping cage is less complex and the area is small, so it can play a good damping role, thereby ensuring the dynamic stability of the motor during grid-connected operation.

Based on the above-mentioned controller, the present embodiment provides a method for controlling the grid-connected operation of a motor, wherein, referring to the flowchart of a control method for the grid-connected operation of a motor shown in FIG. 2 , the method specifically includes the following steps:

Step S202, when the first switch, the second switch and the third switch are all off, the second switch and the third switch are controlled to be closed based on the power-on command sent by the received command sending device, so that the asynchronous start permanent magnet synchronous The motor and the grid are connected with the frequency converter;

The schematic structural diagram of FIG. 1 shows that the first switch, the second switch and the third switch are all in an off state. The command sending device in this embodiment refers to a host computer or a command switch device, which is not limited here.

The start-up command sent by the command sending device refers to the command to control the asynchronous start of the permanent magnet synchronous motor to start running. If the controller receives the start-up command, it can control the second switch and the third switch to close, so that the inverter can pass through the second switch. The utility model is connected to the power grid, and the asynchronous start permanent magnet synchronous motor is connected to the frequency converter through the third switch.

Step S204, judging whether the operation mode carried in the boot command is a grid-connected mode;

The grid-connected mode refers to the mode in which the asynchronous start permanent magnet synchronous motor is connected to the grid for operation.

Step S206, if yes, send a rotational speed control command to the frequency converter to trigger the frequency converter to control the asynchronous start of the permanent magnet synchronous motor to the target frequency carried in the rotational speed control command;

Usually, the target frequency carried in the speed control command can be determined by the same rated frequency and slip frequency as the grid frequency, that is, the target frequency is: fv=fn-fb; where fn is the rated frequency, fb is the slip frequency, The value range of fb is: [0.5%·fn, 5%·fn]. For example, fn=50Hz, fb=1Hz, then the target frequency fv=49Hz, that is, the operating frequency of the asynchronous start permanent magnet synchronous motor needs to be adjusted to 49Hz.

Step S208, determining the maximum voltage deviation between the power grid and the frequency converter;

Step S210, if the maximum voltage deviation is less than the preset voltage threshold and the operating frequency of the asynchronous start permanent magnet synchronous motor reaches the target frequency, control the third switch to open and the first switch to close, so as to merge the asynchronous start permanent magnet synchronous motor into the grid for operation .

If the maximum voltage deviation is less than the preset voltage threshold and the operating frequency of the asynchronous start permanent magnet synchronous motor reaches the target frequency, it means that the asynchronous start permanent magnet synchronous motor is required to be merged into the power grid. Therefore, the controller can control the third switch to turn off to make the The asynchronous start permanent magnet synchronous motor is disconnected from the frequency converter, and the first switch is controlled to be closed so that the asynchronous start permanent magnet synchronous motor is integrated into the grid and continues to run. The preset voltage threshold can be set according to actual needs, which is not limited here.

An embodiment of the present application provides a method for controlling the grid-connected operation of a motor, wherein, when the first switch, the second switch and the third switch are all turned off, if a power-on command sent by the command sending device is received, the first switch is controlled to The second switch and the third switch are closed to connect the asynchronous start permanent magnet synchronous motor and the power grid to the inverter, and when it is judged that the operation mode carried in the startup command is the grid-connected mode, a speed control command is sent to the inverter to trigger the The frequency converter controls the running frequency of the asynchronous start permanent magnet synchronous motor to the target frequency carried in the speed control command; further, after it is determined that the maximum voltage deviation between the power grid and the frequency converter is less than the preset voltage threshold and the permanent magnet synchronous motor is asynchronously started The operating frequency of the motor reaches the target frequency, and the third switch is controlled to open and the first switch to be closed, so as to integrate the asynchronous start permanent magnet synchronous motor into the power grid for operation. The present application can connect the asynchronous start permanent magnet synchronous motor to the grid through the frequency converter, thereby overcoming the difficulty of directly connecting the asynchronous start permanent magnet synchronous motor to the grid and the unsafe problems caused by over-torque and low voltage during operation.

This embodiment provides another control method for the grid-connected operation of the motor, which is implemented on the basis of the above-mentioned embodiment; as shown in FIG. The control method for the grid-connected operation of the electric motor in the system includes the following steps:

Step S302, when the first switch, the second switch and the third switch are all in an off state, control the second switch and the third switch to close based on the power-on command sent by the received command sending device, so that the asynchronous start permanent magnet synchronous The motor and the grid are connected with the frequency converter;

Step S304, judging whether the operation mode carried in the boot command is a grid-connected mode;

Specifically, the above-mentioned operation modes include grid-connected mode and inverter control mode. The grid-connected mode refers to a mode in which an asynchronous start permanent magnet synchronous motor is connected to the power grid for operation, and the inverter control mode refers to using a frequency converter to drive the asynchronous start mode. For the operation mode of the permanent magnet synchronous motor, in this embodiment, if the operation mode is the grid-connected mode, step S306 is performed; if the operation mode is not the grid-connected mode, that is, the operation mode is the inverter control mode, step S316 is performed.

Step S306, sending a rotational speed control command to the frequency converter to trigger the frequency converter to control the asynchronous start of the permanent magnet synchronous motor to the target frequency carried in the rotational speed control command;

Step S308, judging whether the first shutdown instruction sent by the instruction sending device is received;

If no, go to step S310, if yes, go to step S318.

Step S310, determining the maximum voltage deviation between the power grid and the frequency converter;

On the basis of FIG. 1 , as shown in FIG. 4 , the grid-connected operation control system further includes a first voltage sensor CV1 and a second voltage sensor CV2 communicatively connected to the controller 100 , wherein the first voltage sensor CV1 is installed on the grid , used to collect the first three-phase voltage instantaneous value (UA, UB, UC) of the power grid, and the second voltage sensor CV2 is installed at the output end of the inverter to collect the second three-phase voltage instantaneous value of the output end of the inverter ( ua, ub, uc), where the three-phase phase sequences of the power grid and the inverter are consistent, therefore, the voltage deviations corresponding to the three phase sequences can be calculated based on the obtained instantaneous value of the first three-phase voltage and the instantaneous value of the second three-phase voltage. Vub=UA-ua; Vvb=UB-ub; Vwb=UC-uc; then, the maximum voltage deviation is Vb=max(Vub, Vvb, Vwb), and max() is the function of taking the maximum value, that is, three The largest voltage deviation among the voltage deviations is determined as the maximum voltage deviation Vb.

Step S312, if the maximum voltage deviation is less than the preset voltage threshold and the operating frequency of the asynchronously started permanent magnet synchronous motor reaches the target frequency, control the third switch to open and the first switch to close, so as to merge the asynchronously started permanent magnet synchronous motor into the grid for operation. ;

Step S314, if the maximum voltage deviation is not less than the preset voltage threshold and/or the operating frequency of the asynchronously started permanent magnet synchronous motor does not reach the target frequency, execute the step of judging whether the first shutdown command sent by the command sending device is received;

If the maximum voltage deviation is not less than the preset voltage threshold and/or the operating frequency of the asynchronous start permanent magnet synchronous motor does not reach the target frequency, it indicates that the asynchronous start permanent magnet synchronous motor does not meet the requirements for grid integration, so continue to step S308.

Step S316, sending a speed command or a torque command to the frequency converter to trigger the frequency converter to control the asynchronous start of the permanent magnet synchronous motor based on the speed command or the torque command;

When the operation mode is the inverter control mode, the inverter can be used to directly control the asynchronous start permanent magnet synchronous motor to run.

In step S318, the frequency converter is triggered to stop running, and the third switch and the second switch are turned off in sequence.

After the inverter stops running, the asynchronous start permanent magnet synchronous motor will also slowly stop running.

This embodiment provides another method for controlling the grid-connected operation of the motor, which is implemented on the basis of the above-mentioned embodiment; as shown in FIG. The control method for the grid-connected operation of the electric motor in the system includes the following steps:

Step S502, when the first switch, the second switch and the third switch are all in the off state, control the second switch and the third switch to close based on the power-on command sent by the received command sending device, so that the asynchronous start permanent magnet synchronous The motor and the grid are connected with the frequency converter;

Step S504, judging whether the operation mode carried in the boot command is a grid-connected mode;

Step S506, if yes, send a rotational speed control command to the frequency converter to trigger the frequency converter to control the asynchronous start of the permanent magnet synchronous motor to the target frequency carried in the rotational speed control command;

Step S508, determining the maximum voltage deviation between the power grid and the frequency converter;

Step S510, if the maximum voltage deviation is less than the preset voltage threshold and the operating frequency of the asynchronous start permanent magnet synchronous motor reaches the target frequency, control the third switch to open and the first switch to close, so as to merge the asynchronous start permanent magnet synchronous motor into the grid for operation. ;

Step S512, judging whether the second shutdown instruction sent by the instruction sending device is received;

After the permanent magnet synchronous motor is asynchronously started and integrated into the power grid for normal operation, the controller needs to check in real time whether the second shutdown command is received. If yes, go to step S514; if not, go to step S516. The second shutdown command is the same as the first shutdown command The shutdown command is not repeated here.

Step S514, turn off the first switch and the second switch in sequence;

After disconnecting the first switch and the second switch, the asynchronous start permanent magnet synchronous motor and the frequency converter both slowly stop running.

Step S516, receiving the instantaneous value of the three-phase input current of the asynchronous start permanent magnet synchronous motor collected by the current sensor;

As shown in FIG. 4 , the grid-connected operation control system further includes a current sensor CT connected to the controller 100 in communication, wherein the current sensor CT is installed on the connection circuit between the asynchronous start permanent magnet synchronous motor and the grid, and the asynchronous start collected by the current sensor The instantaneous value of the three-phase input current of the permanent magnet synchronous motor is IA, IB, and IC.

Step S518, judging whether the maximum current instantaneous value in the three-phase input current instantaneous value is greater than the preset current threshold value;

The maximum current instantaneous value is the largest current instantaneous value among the above three-phase input current instantaneous values, and the maximum current instantaneous value can be determined by the following formula: Im=max(IA, IB, IC). In this embodiment, the preset current The threshold value range is: (1.05～2.5)·IN·1.414, where IN is the RMS value of the rated current.

If the instantaneous value of the maximum current is greater than the preset current threshold, step S520 needs to be performed, and if the instantaneous value of the maximum current is less than or equal to the preset current threshold, step S512 is performed.

Step S520, open the first switch, close the third switch, and send a current cut-in command to the frequency converter, so as to trigger the frequency converter to cut the drive current carried in the current cut-in command to the asynchronous start permanent magnet synchronous motor, and continue to execute the frequency conversion. The controller sends a speed control command to trigger the step of the inverter to control the running frequency of the permanent magnet synchronous motor to start asynchronously to the target frequency carried in the speed control command.

When the instantaneous value of the maximum current is greater than the preset current threshold, it means that the asynchronous start permanent magnet synchronous motor operates abnormally after being integrated into the power grid. In this embodiment, the asynchronous start permanent magnet synchronous motor can be reconnected to the frequency converter, and step S506 is repeated. Go to step S510, so that after the frequency converter controls the asynchronous start permanent magnet synchronous motor to run normally, it is connected to the power grid again for operation, that is, the application can temporarily take over the operation by the frequency converter when the asynchronous start permanent magnet synchronous motor runs abnormally, Overcurrent is prevented by limiting output torque and reducing rotational speed.

The control method for the grid-connected operation of the motor in this embodiment is mainly aimed at the equipment that is connected to the grid for a long time and operates at a constant speed. In actual operation, most of the time is connected to the grid, so there is no loss of the inverter itself and the motor caused by the high-frequency power supply of the inverter. The high-frequency additional loss of the main body improves the overall efficiency of the grid-connected operation control system, and improves the energy efficiency of some loads such as fans and pumps running at a constant speed. For fixed-speed load equipment with a long working time, the electricity cost saved can be greater than the increased cost caused by adding a frequency converter. The control method for the grid-connected operation of the motor of the present application is also applicable to equipment that operates at a fixed speed part of the time and operates at a variable speed part of the time. , improve the overall energy efficiency of the grid-connected operation control system.

The grid-connected operation control system provided by the embodiment of the present invention has the same technical features as the control method of the motor grid-connected operation provided by the above-mentioned embodiment, so it can also solve the same technical problem and achieve the same technical effect.

The method and device for controlling the grid-connected operation of a motor, and the computer program product of the grid-connected operation control system provided by the embodiments of the present invention include a computer-readable storage medium storing program codes, and the instructions included in the program codes can be used to execute the preceding For the specific implementation of the method described in the method embodiment, reference may be made to the method embodiment, which will not be repeated here.

Those skilled in the art can clearly understand that, for the convenience and brevity of description, for the specific working process of the system described above, reference may be made to the corresponding process in the foregoing method embodiments, which will not be repeated here.

In addition, in the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection , or integrally connected; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or the internal communication between the two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

The functions, if implemented in the form of software functional units and sold or used as independent products, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention can be embodied in the form of a software product in essence, or the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including Several instructions are used to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, Read-Only Memory (ROM, Read-Only Memory), Random Access Memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program codes .

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation or a specific orientation. construction and operation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first", "second", and "third" are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

Finally, it should be noted that the above embodiments are only specific implementations of the present invention, and are used to illustrate the technical solutions of the present invention, but not to limit them. The protection scope of the present invention is not limited thereto, although with reference to the foregoing embodiments The present invention has been described in detail, and those skilled in the art should understand that: any person skilled in the art can still modify the technical solutions described in the foregoing embodiments within the technical scope disclosed by the present invention or can easily think of change, or equivalently replace some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Inside. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (10)

1. a control method for electric motor grid-connected operation, it is characterized in that, described method is applied to the controller in the grid-connected operation control system, and described grid-connected operation control system also comprises the asynchronous start that is communicatively connected with described controller A permanent magnet synchronous motor, a frequency converter, a first switch, a second switch and a third switch, wherein the asynchronous start permanent magnet synchronous motor is connected to a power grid through a first switch, and the frequency converter is connected to the power grid through a second switch connection, the frequency converter is connected with the asynchronous start permanent magnet synchronous motor through a third switch, and the asynchronous start permanent magnet synchronous motor is a motor with a rotor with a damping cage; the method includes: When the first switch, the second switch and the third switch are all turned off, the second switch and the third switch are controlled to be closed based on the power-on instruction sent by the received instruction sending device, so as to start the asynchronous startup The permanent magnet synchronous motor and the power grid are connected with the frequency converter; Determine whether the operation mode carried in the boot command is a grid-connected mode; If yes, send a rotational speed control instruction to the frequency converter to trigger the frequency converter to control the operating frequency of the asynchronous start permanent magnet synchronous motor to the target frequency carried in the rotational speed control instruction; determining the maximum voltage deviation between the grid and the frequency converter; If the maximum voltage deviation is less than a preset voltage threshold and the operating frequency of the asynchronous start permanent magnet synchronous motor reaches the target frequency, control the third switch to open and the first switch to close, so as to turn the asynchronous start-up permanent magnet synchronous motor on. The permanent magnet synchronous motor is started to operate into the grid. 2. The control method according to claim 1, wherein the method further comprises: If it is determined that the operating mode is the inverter control mode, a speed command or torque command is sent to the inverter to trigger the inverter to control the asynchronous start permanent magnet synchronization based on the speed command or the torque command Motor runs. 3. The control method according to claim 1, wherein before determining the maximum voltage deviation between the power grid and the frequency converter, the method further comprises: judging whether the first shutdown instruction sent by the instruction sending device is received; If so, trigger the frequency converter to stop running, and turn off the third switch and the second switch in sequence; If not, the step of determining the maximum voltage deviation between the grid and the frequency converter is performed. 4. The control method according to claim 3, wherein the method further comprises: If the maximum voltage deviation is not less than the preset voltage threshold and/or the operating frequency of the asynchronous start permanent magnet synchronous motor does not reach the target frequency, a process of judging whether the first shutdown command sent by the command sending device is received is executed. step. 5. The control method according to claim 1, wherein the grid-connected operation control system further comprises a first voltage sensor and a second voltage sensor connected in communication with the controller; The step of determining the maximum voltage deviation between the grid and the frequency converter includes: receiving the first three-phase voltage instantaneous value of the power grid collected by the first voltage sensor, and the second three-phase voltage instantaneous value of the output end of the frequency converter collected by the second voltage sensor; Calculate the voltage deviations corresponding to the three phase sequences respectively based on the instantaneous value of the first three-phase voltage and the instantaneous value of the second three-phase voltage; The largest voltage deviation among the three said voltage deviations is determined as the maximum voltage deviation. 6. The control method according to claim 1, wherein the grid-connected operation control system further comprises a current sensor communicatively connected to the controller; the method further comprises: receiving the instantaneous value of the three-phase input current of the asynchronous start permanent magnet synchronous motor collected by the current sensor; judging whether the maximum current instantaneous value of the three-phase input current instantaneous values is greater than a preset current threshold; If yes, open the first switch, close the third switch, and send a current cut-in command to the frequency converter to trigger the frequency converter to cut the current cut-in command to the asynchronous start permanent magnet synchronous motor The drive current carried in the frequency converter, and continue to execute the step of sending a rotational speed control command to the frequency converter to trigger the frequency converter to control the operating frequency of the asynchronous start permanent magnet synchronous motor to the target frequency carried in the rotational speed control command . 7. The control method according to claim 6, wherein before receiving the instantaneous value of the three-phase input current of the asynchronous start permanent magnet synchronous motor collected by the current sensor, the method further comprises: judging whether a second shutdown instruction sent by the instruction sending device is received; If so, turn off the first switch and the second switch in sequence; If not, the step of receiving the instantaneous value of the three-phase input current of the asynchronous start permanent magnet synchronous motor collected by the current sensor is performed. 8. The control method according to claim 7, wherein the method further comprises: If the maximum current instantaneous value among the three-phase input current instantaneous values is less than or equal to the preset current threshold value, the step of judging whether the second shutdown command sent by the command sending device is received is performed. 9. A control device for the grid-connected operation of an electric motor, characterized in that the control device is applied to a controller in a grid-connected operation control system, and the grid-connected operation control system further comprises an asynchronous device communicatively connected to the controller. Start a permanent magnet synchronous motor, a frequency converter, a first switch, a second switch and a third switch, wherein the asynchronous start permanent magnet synchronous motor is connected to the grid through a first switch, and the frequency converter is connected to the power grid through a second switch The power grid is connected, and the frequency converter is connected to the asynchronous start permanent magnet synchronous motor through a third switch, and the asynchronous start permanent magnet synchronous motor is a motor with a rotor with a damping cage; the control device includes: a first control module, configured to control the second switch and the third switch to close based on the power-on command sent by the received command sending device when the first switch, the second switch and the third switch are all off , to connect the asynchronous start permanent magnet synchronous motor and the power grid with the frequency converter; a judgment module for judging whether the operation mode carried in the boot command is a grid-connected mode; The sending module is used to send a rotational speed control instruction to the frequency converter if the judgment module judges it to be yes, so as to trigger the frequency converter to control the running frequency of the permanent magnet synchronous motor to start asynchronously to the target carried in the rotational speed control instruction frequency; a determining module for determining the maximum voltage deviation between the power grid and the frequency converter; a second control module, configured to control the third switch to be turned off and the first switch to be turned off if the maximum voltage deviation is less than a preset voltage threshold and the operating frequency of the asynchronous start permanent magnet synchronous motor reaches the target frequency closed to operate the asynchronous start permanent magnet synchronous motor into the grid. 10. A grid-connected operation control system, characterized in that, the grid-connected operation control system comprises a controller, and an asynchronous start permanent magnet synchronous motor, a frequency converter, a first switch, a second synchronous motor that are communicatively connected to the controller. a switch and a third switch, wherein the asynchronous start permanent magnet synchronous motor is connected to the grid through a first switch, the frequency converter is connected to the grid through a second switch, and the frequency converter is connected to the asynchronous motor through a third switch starting the permanent magnet synchronous motor connection, and the asynchronous starting permanent magnet synchronous motor is a motor with a damping cage on the rotor; The controller is used for executing the control method for the grid-connected operation of the electric motor according to any one of claims 1-8.

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