Starting control device, system and method for induction motor

Abstract

The present invention provides a starting control device, system and method for an induction motor. The device is configured to: control a driving control device of the motor so that the rotating induction motor enters a DC braking state; receive a first parameter and a second parameter, the first parameter including a given value of an excitation current, a given value of a torque current and a given value of a stator electrical angle, and the second parameter including a phase current of the induction motor; based on the first parameter and the second parameter, calculate the feedback value of the excitation current and the feedback value of the torque current in a current closed-loop controller; determine the direction and frequency of the induction motor based on the change of the feedback value of the excitation current over time, the change of the feedback value of the torque current over time, and the relationship between the changes of the two; and determine a power supply scheme for the induction motor based on the determined direction and frequency, so that the induction motor enters a starting state from a DC braking state.

Description

Technical Field

[0001] The present application generally relates to control technology of induction motors, and more particularly to a starting control device, system and method for induction motors. Background Art

[0002] Induction motors convert electrical energy into mechanical energy and are widely used in a variety of mechanical systems. In addition to rotating under the control of a control signal output by its control system, induction motors may also rotate without the control signal, for example, driven by another coupled motor or in a free stop state due to a failure of the microcontroller of the control system. Once such a situation occurs, the practice in the prior art is to stop the rotating induction motor first and then start the induction motor from a stationary state. In this way, if the induction motor has a large inertia, it may take a long time (possibly up to 2-3 hours) to stop, and thus, a long time has to be waited before starting the induction motor, which seriously affects the operating efficiency of the mechanical system in which the induction motor is set. Summary of the invention

[0003] In view of the above problems in the prior art, an embodiment of the first aspect of the present invention provides a starting control device for an induction motor, which is configured to: when the induction motor is in a state where it rotates without being controlled by a control signal output by its drive control device, control the drive control device so that the rotating induction motor enters a DC braking state; receive a first parameter and a second parameter, the first parameter including a given value of an excitation current, a given value of a torque current and a given value of a stator electrical angle, wherein the given value of the excitation current is associated with the rated current of the induction motor, and the second parameter including a phase current of the induction motor; based on the first parameter and the second parameter, calculate a feedback value of the excitation current and a feedback value of the torque current in a current closed-loop controller; determine the direction and frequency of the induction motor based on changes in the feedback value of the excitation current over time, changes in the feedback value of the torque current over time, and the relationship between the changes between the two; and based on the determined direction and frequency, determine a power supply scheme for the induction motor so that the induction motor enters a starting state from a DC braking state.

[0004] An embodiment of the second aspect of the present invention provides a starting control system for an induction motor, comprising: a drive control device, configured to be electrically connected to the induction motor and including a plurality of control switches, wherein the plurality of control switches are configured to place the induction motor in a DC braking state; an input device, configured to receive a first parameter used as an input to a current closed-loop controller, including a given value of an excitation current, a given value of a torque current, and a given value of a stator electrical angle; a detection device, configured to be electrically connected to the induction motor and detect the phase currents of each phase of the induction motor, used as a second parameter of the input to the current closed-loop controller; and a starting control device as described above, configured to receive the first parameter and the second parameter, calculate feedback values ​​of the torque current and the excitation current based on the first parameter and the second parameter, determine the direction and frequency of the motor based on changes in the feedback value of the torque current, changes in the feedback value of the excitation current, and the relationship between the changes therebetween, and determine a power supply scheme for the motor based on the direction and frequency so that the motor enters a starting state.

[0005] According to an embodiment of a third aspect of the present invention, a starting control method for an induction motor is provided. Optionally, the method is executed by the device as described above and / or the system as described above, and the method comprises: when the induction motor is in a state where it rotates without being controlled by a control signal output by its drive control device, controlling the drive control device so that the rotating induction motor enters a DC braking state; receiving a first parameter and a second parameter, the first parameter comprising a given value of an excitation current, a given value of a torque current and a given value of a stator electrical angle, wherein the given value of the excitation current is associated with a rated current of the induction motor, and the second parameter comprising a phase current of the induction motor; based on the first parameter and the second parameter, calculating a feedback value of the excitation current and a feedback value of the torque current in a current closed-loop controller; determining a direction and a frequency of the induction motor based on changes in the feedback value of the excitation current over time, changes in the feedback value of the torque current over time, and the relationship between the changes; and determining a power supply scheme for the induction motor based on the determined direction and frequency so that the induction motor enters a starting state from a DC braking state. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Various aspects of the present invention will be described below in conjunction with the accompanying drawings. These drawings are provided to illustrate rather than limit the present invention.

[0007] Figure 1 A schematic diagram of a starting control system for an induction motor according to a possible embodiment of the present invention is shown.

[0008] Figure 2 A flowchart of a startup control method for an induction motor according to a feasible embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0009] Considering that the induction motor may rotate "freely" without being controlled by the control signal output by its drive control system, the present invention proposes a control scheme that can quickly start the induction motor in this situation without waiting for the motor to stop before starting.

[0010] The "free" rotation state of the induction motor can be understood as the rotation of the motor being in an uncontrolled state, for example, not being controlled by the control signal output by its drive control system. The "free" rotation state can include: a state of rotation due to external force (for example, a fan is blown by the wind or an induction motor is driven by another coupled motor); a motor that was originally driven and controlled by a control signal and rotated at high speed, but lost the control signal due to a driver failure or stop, and the induction motor is in a free stop state.

[0011] Specifically, according to the starting control scheme of the induction motor of an embodiment of the present invention, during the process of DC braking of the rotating induction motor, the state of the induction motor (for example, the direction and frequency of the induction motor) can be quickly captured, and a power supply scheme can be determined for the motor based on the captured motor state, so that the induction motor enters the starting state from the DC braking state.

[0012] The control scheme according to the embodiment of the present invention can realize the rapid start of the induction motor mainly because it includes such control logic, that is, the feedback value of the excitation current and the feedback value of the torque current are calculated in the current closed-loop controller, and the direction and frequency of the induction motor are determined based on the change of the feedback value of the excitation current over time, the change of the feedback value of the torque current over time, and the relationship between the changes of the two. The control logic can be implemented by one or more software modules.

[0013] The control scheme according to the embodiment of the present invention can not only realize the rapid start-up of the motor, but also determine a suitable power supply scheme for the induction motor, because the state of the induction motor has been captured, so that a suitable power supply scheme can be determined based on the motor state, and the motor will not be damaged due to excessive power provided, nor will the induction motor be unable to start normally due to too little power provided.

[0014] The specific implementation of the present invention is described below with reference to the accompanying drawings.

[0015] Figure 1A start control system 100 for an induction motor M according to a feasible embodiment of the present invention is schematically shown, which mainly includes an input device 10, a detection device (not shown), a drive control device 20 and a start control device 30. In one embodiment of the present invention, the induction motor M is implemented as a three-phase asynchronous motor.

[0016] The input device 10 is used to receive a first parameter. The first parameter is used as an input of the current closed-loop controller and participates in calculation in the current closed-loop controller.

[0017] The first parameter may include some parameter set values ​​used as inputs to the current closed-loop controller, for example, a set value I of the excitation current d *、Torque current given value I q * and a given value θ* of the stator electrical angle.

[0018] The input device 10 can be implemented as an input interface, a touch screen, etc., which can receive input from a user. The user can input given values ​​of various parameters through the input device.

[0019] In one embodiment, the given value of the excitation current is associated with a motor parameter of the induction motor. For example, the given value of the excitation current is a value between 0.5 and 2 times the rated current of the induction motor.

[0020] In one embodiment, the given value of the excitation current is associated with a motor parameter of the induction motor. For example, the given value of the excitation current is a value between the no-load current and the rated current of the induction motor.

[0021] In one embodiment, the given value of the torque current is 0.

[0022] In one embodiment, the given value of the stator electrical angle is any value between 0° and 360°.

[0023] The detection device (not shown) is used to detect the phase current (for example, I a ~I c ). The phase current is used as the second parameter of the input of the current closed-loop controller and participates in the calculation in the current closed-loop controller. The detection device can be implemented by setting a resistor on the branch of each phase to obtain the current of each phase, or by obtaining the current of each phase through Hall sampling current. The present invention does not limit the detection method of the phase current.

[0024] The drive control device 20 is electrically connected to the induction motor M. The drive control device 20 may include a plurality of control switches, and the power supply control or the brake control of the induction motor M is realized by setting the disconnection and connection of each control switch.

[0025] In one embodiment, a plurality of control switches are configured to form a bridge inverter circuit, for example, a plurality of control switches form three parallel bridge arms. Each bridge arm may include a first control switch and a second control switch, wherein the first control switch of each bridge arm forms an upper bridge arm of the inverter circuit, and the second control switch of each bridge arm forms a lower bridge arm of the inverter circuit.

[0026] In this embodiment, the induction motor can be placed in a DC braking state by setting each control switch. For example, the start control device 30 generates a setting signal for turning each control switch on or off, so that one of the two control switches constituting the same bridge arm among the multiple control switches is set to be off, and the other is set to be on, so that the induction motor is placed in a DC braking state. In other words, based on the setting method of the setting signal, one of the first control switch and the second control switch of each bridge arm is in a state of off, and the other is in a state of on.

[0027] The start control device 30 is electrically connected to the input device 10, the detection device and the drive control device 20, respectively. The start control device 30 is configured to perform the following operations: receiving a first parameter from the input device 10 and a second parameter from the detection device; calculating a feedback value of the torque current and a feedback value of the excitation current in a current closed-loop controller based on the first parameter and the second parameter; determining the direction and frequency of the motor based on changes in the feedback value of the torque current, changes in the feedback value of the excitation current and the relationship between the changes; and determining a power supply scheme for the motor based on the determined direction and frequency, so that the induction motor enters a starting state from a DC braking state.

[0028] In one implementation, the start control device 30 can be implemented in hardware or software or a combination of software and hardware. For the hardware-implemented part, it can be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic units designed to perform their functions, or combinations thereof. For the software-implemented part, it can be implemented with the aid of microcodes, program codes, or code segments, and can also be stored in a machine-readable storage medium such as a storage component.

[0029] In one implementation, the startup control device 30 is implemented as including a memory and a processor. The memory contains instructions, which, when executed by the processor, enable the processor to execute the startup control strategy / startup control method according to the embodiment of the present invention.

[0030] In one implementation, the start control device 30 can be implemented to include a motor state determination unit 31 and a microcontroller 32. The motor state determination unit 31 can be implemented by one or more software modules, and is used to determine the direction DIR and frequency FREQ of the motor. The microcontroller 32 generates a control signal (e.g., a PWM signal) based on the determined direction and frequency of the motor, and outputs the control signal to the drive control device 20, so as to enable the motor to enter the power supply strategy of the start state from the DC braking state. In this implementation, the motor state determination unit 31 can be set in the microcontroller 32.

[0031] Figure 2 A start-up control method 200 for an induction motor according to an implementation of the present invention is shown. The method 200 can be executed in the start-up control device 30 or in the start-up control system 100.

[0032] In block 202, the induction motor M is originally in a "free" rotating state, and the on or off state of multiple control switches of the drive control device 20 is set so that the induction motor M is in a DC braking state. For example, the start control device 30 generates a setting signal for controlling each control switch so that the start control device 30 is set to put the induction motor M in a DC braking state.

[0033] In one embodiment, based on the setting signal, one of two control switches constituting the same bridge arm among the multiple control switches of the drive control device 20 is set to be disconnected, and the other is set to be connected, so that the induction motor is in a DC braking state.

[0034] In block 204, the start control device 30 receives a first parameter and a second parameter. The first parameter includes a given value of the excitation current, a given value of the torque current, and a given value of the stator electrical angle, wherein the given value of the excitation current is associated with the rated current of the induction motor. The second parameter includes the phase current of each phase of the induction motor.

[0035] In one embodiment, the given value of the excitation current is between the no-load current and the rated current of the motor; or, between 0.5 times and 2 times the rated current of the motor. The given value of the torque current is 0.

[0036] In one embodiment, the given value of the stator electrical angle is any value between 0° and 360°.

[0037] It is understandable that the present invention does not limit the order in which the parameters are received.

[0038] In block 206 , the startup control device 30 calculates a feedback value of the excitation current and a feedback value of the torque current in a current closed-loop controller based on the first parameter and the second parameter.

[0039] The current closed-loop controller can perform closed-loop control on the input parameters (first parameter and second parameter), for example, decoupling, coordinate transformation, and PI adjustment, so as to obtain the feedback value of the excitation current (i.e., the feedback value of the d-axis current) and the feedback value of the torque current (i.e., the feedback value of the q-axis current), and enable the feedback value of the excitation current and the feedback value of the torque current to follow the corresponding set values ​​after experiencing the fluctuation process, that is, the feedback value of the torque current is ultimately its given value, and the feedback value of the excitation current is ultimately its given value.

[0040] In box 208, the starting control device 30 generates a first curve of the feedback value of the excitation current changing with time and a second curve of the feedback value of the torque current changing with time, monitors the first curve and the second curve, and determines whether the feedback value of the excitation current and the feedback value of the torque current have reached effective values ​​that can be used for subsequent processing.

[0041] In one embodiment, the feedback value of the excitation current will gradually increase from a smaller value until the feedback value of the excitation current reaches its given value, and it is considered that the feedback value of the excitation current has reached an effective value that can be used for subsequent processing. In addition, the feedback value of the torque current will also experience unstable fluctuations in the initial stage. When the feedback value of the torque current reaches more than 5% of the feedback value of the excitation current, preferably, more than 20% of the feedback value of the excitation current, it is considered that the feedback value of the torque current has reached an effective value that can be used for subsequent processing.

[0042] In block 210 , the start control device 30 determines the direction and frequency of the induction motor based on the change of the feedback value of the excitation current over time, the change of the feedback value of the torque current over time, and the relationship between the changes of the two.

[0043] In box 2101, the start control device 30 determines the direction of the induction motor based on such judgment logic, that is, when the feedback value of the excitation current reaches the set value of the excitation current, when the feedback value of the torque current is positive, the direction of the induction motor is determined to be one direction; and when the feedback value of the excitation current reaches the set value of the excitation current, when the feedback value of the torque current is negative, the direction of the induction motor is determined to be another direction opposite to the one direction. The one direction is forward rotation, and the other direction is reverse rotation; or the one direction is reverse rotation, and the other direction is forward rotation. It can be seen that the direction of the motor can be obtained by the positive and negative polarity of the feedback value of the excitation current and the feedback value of the torque current.

[0044] In block 2102, the start control device 30 determines the frequency of the induction motor based on such a judgment logic, that is, the frequency of the feedback torque current is obtained based on the change of the feedback value of the torque current over time, and the frequency of the feedback torque current is determined as the frequency of the induction motor. In the process of determining the frequency of the feedback torque current, the peak-to-peak value, the peak-to-trough value, the zero-crossing point, the peak-to-zero point, etc. of the feedback value-time curve of the torque current can be used to obtain the frequency.

[0045] It is understandable that the present invention does not limit the order of determining the direction and determining the frequency. In other words, the execution order of box 2101 and box 2102 is not limited.

[0046] In block 212 , the starting control device 30 determines a power supply scheme for the induction motor based on the determined direction and frequency, so that the induction motor enters a starting state from a DC braking state.

[0047] After the direction and frequency of the induction motor are obtained, a suitable power supply scheme can be determined for the induction motor based on the instruction including the direction and frequency. The present invention does not limit how to determine the power supply scheme.

[0048] It is understood that the process of determining the direction (DIR) and frequency (FREQ) of the induction motor according to the embodiment of the present invention is performed during the fluctuation of the feedback values ​​of the excitation current and the torque current. In other words, the process is performed before the feedback values ​​of the excitation current and the torque current stabilize at their given values.

[0049] In addition, according to the technical solution of the embodiment of the present invention, the time period for determining the direction (DIR) and frequency (FREQ) of the induction motor (for example, the time period from inputting parameters to the current closed-loop controller to determining the direction and frequency of the motor) is extremely short, between about 10ms and about 2000ms. For this time period, the greater the speed of the motor during the DC braking process, the shorter the time period; otherwise, the time period increases slightly.

[0050] The present invention also provides a machine-readable storage medium storing executable instructions, which, when executed, enable a processor to perform the startup control 200 .

[0051] Although some embodiments have been described above, these embodiments are given by way of example only and are not intended to limit the scope of the invention. The appended claims and their equivalents are intended to cover all modifications, substitutions and changes made within the scope and spirit of the invention.

Claims

1. A starting control device for an induction motor, configured to: When the induction motor is in a state where it rotates without being controlled by a control signal output by its drive control device, controlling the drive control device so that the rotating induction motor enters a DC braking state; receiving a first parameter and a second parameter, wherein the first parameter includes a given value of an excitation current, a given value of a torque current, and a given value of a stator electrical angle, wherein the given value of the excitation current is associated with a rated current of the induction motor, and the second parameter includes a phase current of the induction motor; Based on the first parameter and the second parameter, a feedback value of the excitation current and a feedback value of the torque current are calculated in a current closed-loop controller; Determine the direction and frequency of the induction motor based on the change of the feedback value of the excitation current over time, the change of the feedback value of the torque current over time, and the relationship between the changes of the two; and Based on the determined direction and frequency, a power supply scheme is determined for the induction motor so that the induction motor enters a starting state from a DC braking state.

2. The startup control device according to claim 1, wherein: The starting control device determines the direction of rotation of the induction motor by: When the feedback value of the excitation current reaches the set value of the excitation current, when the feedback value of the torque current is positive, the direction of rotation of the induction motor is determined to be a first direction, and when the feedback value of the torque current is negative, the direction of rotation of the induction motor is determined to be an opposite second direction.

3. The startup control device according to claim 1, wherein: The starting control device determines the frequency of the induction motor by: The frequency of the fed-back torque current is obtained based on the change of the feedback value of the torque current over time, and the frequency of the fed-back torque current is determined as the frequency of the induction motor.

4. The startup control device according to claim 1, wherein: The given value of the excitation current is between the no-load current and the rated current of the motor, or between 0.5 times and 2 times the rated current of the motor; and the given value of the torque current is 0.

5. The startup control device according to claim 1, wherein: The given value of the stator electrical angle is any value between 0° and 360°.

6. The startup control device according to claim 1, wherein: The startup control device is also configured to: When the feedback value of the field current reaches its given value and when the feedback value of the torque current reaches 5% or more of the feedback value of the field current, determination on the direction of rotation and frequency of the induction motor is performed.

7. The startup control device according to claim 1, wherein: The startup control device is also configured to: After the feedback value of the field current reaches its given value and the feedback value of the torque current reaches more than 20% of the feedback value of the field current, determination on the direction of rotation and frequency of the induction motor is performed.

8. The startup control device according to claim 1, wherein: The start-up control device is configured to generate a setting signal for setting a plurality of control switches of a drive control device of the induction motor so that the induction motor is in a state of DC braking.

9. The startup control device according to claim 8, wherein: The setting signal sets one of two control switches constituting the same bridge arm among the plurality of control switches to be disconnected and the other to be connected, so that the induction motor is in a state of DC braking.

10. The startup control device according to claim 1, wherein: The induction motor is a three-phase asynchronous motor.

11. A starting control system for an induction motor, comprising: A drive control device, configured to be electrically connected to the induction motor and comprising a plurality of control switches, wherein the plurality of control switches are configured to put the induction motor in a DC braking state; An input device configured to receive first parameters used as inputs to the current closed-loop controller, including a given value of the field current, a given value of the torque current, and a given value of the stator electrical angle; a detection device, configured to be electrically connected to the induction motor and detect a phase current of each phase of the induction motor, which is used as a second parameter input to the current closed-loop controller; as well as The starting control device as described in any one of claims 1 to 10 is configured to receive the first parameter and the second parameter, calculate feedback values ​​of the torque current and the excitation current based on the first parameter and the second parameter, determine the direction and frequency of the motor based on changes in the feedback value of the torque current, changes in the feedback value of the excitation current and the relationship between the changes therebetween, and determine a power supply scheme for the motor based on the direction and frequency so that the motor enters a starting state.

12. A method for starting and controlling an induction motor, the method being executed by the device according to any one of claims 1 to 10 and / or the system according to claim 11, the method comprising: When the induction motor is in a state where it rotates without being controlled by a control signal output by its drive control device, controlling the drive control device so that the rotating induction motor enters a DC braking state; receiving a first parameter and a second parameter, wherein the first parameter includes a given value of an excitation current, a given value of a torque current, and a given value of a stator electrical angle, wherein the given value of the excitation current is associated with a rated current of the induction motor, and the second parameter includes a phase current of the induction motor; Based on the first parameter and the second parameter, a feedback value of the excitation current and a feedback value of the torque current are calculated in a current closed-loop controller; Determine the direction and frequency of the induction motor based on the change of the feedback value of the excitation current over time, the change of the feedback value of the torque current over time, and the relationship between the changes of the two; and Based on the determined direction and frequency, a power supply scheme is determined for the induction motor so that the induction motor enters a starting state from a DC braking state.

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