KR100737676B1 - Sensorless vector controled inverter for lifting machine with overload protection and fail safe - Google Patents

Abstract

A sensorless vector controlled inverter of an induction motor with fall and overload prevention functions is provided to prevent erroneous operation and fall of the inverter due to overload, and damage of equipments due to overweight by including an overload preventing apparatus and a fall detecting apparatus. A sensorless vector controlled inverter of an induction motor with fall and overload prevention functions includes an overload preventing apparatus(17), and a fall detecting apparatus(18). The overload preventing apparatus(17) calculates weight of a load through a torque component current of SFRF(Strain Frequency Response Function) which is calculated by an MRAS(8)(Model Reference Adaptive System), and generates an overload output when the equipment is overweighed. The fall detecting apparatus(18) detects a fall and generates an output when the speed is not controlled due to internal or external disorder of the inverter.

Description

Sensorless Vector Controled Inverter for Lifting Machine with Overload Protection and Fail Safe}

1 is a block diagram of an induction motor sensorless vector control inverter according to the present invention.

2 is a fall detection flowchart according to the present invention.

<Explanation of symbols for main parts of drawing>

1: speed command generator 2: speed controller 3: torque current controller

4: voltage command operator 5: magnetic flux command generator 6: magnetic flux controller

7: flux current controller

8: Model Reference Adaptive System (MRAS)

Adaptive Controller for Sensorless Vector Control of Induction Motors

9: D-Q converter 10: Current sensor 1 11: Current sensor 2

12: rectifying unit 13: smoothing unit 14: switching unit

15: voltage sensor 16: induction motor

17: Overload protector 18: Fall detector

21: magnetic flux test 22: torque test 23: speed test

<Definition of Terms>

Inverter Refers to an induction motor sensorless vector control inverter unless otherwise specified.

Adaptive Control System based on MRAS Mathematical Model

            (Model Reference Adaptive System)

Coordinate system rotates in synchronization with SFRF stator flux

            (State Flux Referenc Frame)

p differential operator (d / dt)

인버터의 DC-Link 전압

DC-Link voltage of the inverter

λ _s magnetic flux vector

λ ^e ds (λ ^e qs) The d-axis (q-axis) component of the stator flux seen from the SFRF

               (d-axis state flux in state flux reference frame, SFRF)

θ Angle of flux vector (Angle of λ _s )

angular speed ω _e of the magnetic flux vector (Angular frequency of λ _s)

ω _sl Sleep frequency (Sleep angular frquency of λ _s )

ω _r Angular frequency of motor

i ^e ds (i ^e qs) The d-axis (q-axis) component of the stator current as seen from the SFRF

         (d (q) -axis state current in state flux reference frame, SFRF)

R _s (R _r ) Stator (rotor) resistance

L _s (L _r , L _m ) Stator (rotor, mutual) inductance

σ leakage inductance (Total leakage coefficient (= 1-L ² m / (LsLr)))

^τ r Rotor Time Costant (Lr / Rr)

T _e Generated torque

K _T motor torque constant

Load torque by T _L item

T _M Machine torque

M _g Weight of item (Load)

Mg1 Weight of the item (Load)

P number of poles

R load rotation radius

ω _C Low pass filter cutoff frequency

Tolerance of δ _λ flux

δ _T torque change tolerance

δ _ω speed tolerance

The superscript * and ^ symbols added to each item mean each setting value and the value estimated by MRAS.

Display example

ω _r Actual speed of motor

ω ^* r Reference speed of motor

ω ^{^} rEstimated speed of motor by MRAS

Conventional induction motor sensorless vector control inverters have been used in induction motor driving devices such as washing machines and air conditioners. However, at low speeds below 1 Hz, torque and speed reliability is not secured. Application is avoided in a vertically moving drive such as a crane required.

The general configuration and operation of sensorless vector control inverters for induction motors are well known (see T. Ohtani, N. Takada and K. Takada, "Vector Control of Induction Motor without Shaft encoder", IEEE Trans.on Ind.Appl) ., vol. 28, no.1, pp.157-164, 1992), and thus, a detailed description of the induction motor sensorless vector control is omitted.

1 is a block diagram of an induction motor sensorless vector control inverter of the present invention.

The configuration of a conventional induction motor sensorless vector control inverter will be described with reference to FIG. The conventional induction motor sensorless vector control inverter includes a rectifying part 12 for converting AC power into direct current, a smoothing part 13 including a plurality of capacitors to smooth the direct current power rectified by the rectifying part 12, and The switching unit 14 for converting the DC power of the smoothing unit 13 to the AC power, the torque T ^{^} _e generated by the induction motor using the mathematical model of the induction motor, the speed of the magnetic flux ω ^{^} _r , the direction of the magnetic flux θ ^{^ Is} estimated by the MRAS (8) for calculating ^{^} , the speed command generator (1) adjusted by the inverter external speed command, and the speed command ω ^* _r generated by the speed command generator (1) and the MRAS (8). the speed of the car, type of ω ^{^} _r torque minutes instruction current i ^{e *} and the speed controller 2 to calculate a _qs, the torque minutes instruction current calculated by the speed controller 2, i ^{e *} _qs and MRAS (8 The input of the torque component current i ^{e ^} _qs estimated by A torque current controller 3 for controlling the torque component current, a magnetic flux command generator 5 for determining the magnitude of the magnetic flux generated in the motor, and? ^{E *} _ds and MRAS 8 outputted from the magnetic flux command generator 5; ) estimated by λ ^{e ^} _ds and a flux controller (6) for controlling the magnetic flux of the stator and the between difference the input magnetic flux minute current for the magnetic flux to raw calculated from the magnetic flux controller 6 sets the value i ^{e *} _The magnetic flux current controller 7 which controls the magnetic flux current by inputting the difference between _ds and i ^{e ^} _ds estimated by the MRAS 8, and the torque current controller 3 and the magnetic flux current controller 7 are calculated. A voltage command operator 4 for generating a PWM waveform by inputting the supplied voltage, and two current sensors 1 (10) and a current sensor 2 for detecting the current of two phases of the three-phase currents generated by the switching unit 14. 11 and the output signals of the two current sensors 1 (10) and the current sensor 2 (11) to the MRAS (8). And DQ converter 9 for converting the form of the input is configured as a voltage sensor 15 for recognizing a voltage of a DC power supply smoothing by the smoothing section 13.

Such a conventional sensorless vector control inverter has no means for detecting when the speed of the motor is not normally controlled due to an internal or external factor of the inverter. Use in devices where there is a risk of accidental falling of the article when the speed is not controlled is avoided. In addition, in order to prevent overload in a device such as a crane that moves vertically, a separate weight sensor such as a load cell is used to protect against overload. However, an induction motor sensorless vector control inverter generates an electric motor by internal software. Torque is controlled quantitatively, so that the product's weight can be calculated by software inside the inverter using torque generated by the induction motor sensorless vector control inverter in the vertical load to protect against overload without using a separate weight sensor. Will be.

According to the present invention, when an inverter applied to a driving unit of a device for vertically moving an article such as a crane has a step out of which the speed of the motor is not normally controlled due to an internal or external factor of the inverter, the inverter detects it without a rotation sensor. The present invention relates to a method of generating a signal to prevent a fall of an article, and a method of measuring an article's weight by an inverter to prevent an accident due to an overload. In the present invention, the fall prevention function and the overload protection function are implemented independently of each other in the inverter software, and the result is output as an external signal to the inverter through a relay.

1 is a configuration diagram of an induction motor sensorless vector control inverter of the present invention.

In the sensorless vector control inverter according to the present invention, descriptions of the same elements as those of the general structure and operation of the conventional sensorless vector control inverter will be omitted.

Hereinafter, the present invention will be described in more detail with reference to FIG. 1.

The present invention relates to a conventional senseless vector control inverter described with reference to FIG.

Overload protector (17) to calculate the weight of the load to prevent overload and

Fall detector (18) for generating a signal by predicting a fall

Is added.

First, the overload protector will be described using FIG. 1. The generation torque T _e of the induction motor in the sensorless vector control is calculated by (1).

[Equation 1]

In (Equation 1), the stator flux λ ^e _ds is constantly controlled, so treating this as a constant causes the torque generated by the motor to be proportional to the motor torque constants K _T and i ^e _qs expressed by Equation (2). Equation 3).

[Equation 2]

[Equation 3]

On the other hand, the relationship between the motor generated torque Te, the torque T _L by the weight of the article, the machine T _M , the moment of inertia J _m, and the speed can be expressed by Equation (4).

[Equation 4]

Substituting the torque T _L by the load into the equation T _L = M _g R expressed as the product of the weight and the load rotation radius R, and substituting (dω / dt) = 0, 5) can be expressed.

[Equation 5]

The linearly with the torque value T _M and the load radius of gyration R is because it does not change value, the weight of the load M _g is the torque current at SFRF system that is q-axis current i ^e _qs by the machine itself in (Equation 5) It can be seen that it is proportional. Therefore, by reading the currents i ^e _qs0 and j ^e _qs1 generated under the condition of load M _g = 0 and the reference load M _g = M _1g , the machine itself is obtained using (Equation 6) and (Equation 7). When the torque value T _M and the load rotation radius R are obtained, the weight of the arbitrary load M _g can be calculated through the current j ^e _qs as shown in Equation (8).

[Equation 6]

[Equation 7]

[Equation 8]

Since the current i ^e _qs is calculated and controlled quantitatively hundreds of times per second in the MRAS 8, the weight change of the load is calculated within 1/100 second. As described above, the overload protector 17 of FIG. 1 calculates the weight of the load through the torque component current i ^e _qs calculated by the MRAS 8 and exceeds the weight allowed by the machine. It generates overload output at and performs overload prevention function.

Next, a description of the fall prevention function will be described with reference to FIGS. 1 and 2.

The condition for normal operation without falling of the vertically moving load by the induction motor sensorless vector control inverter is that the magnetic flux of the induction motor is controlled to a certain magnitude, and the torque generated from the induction motor should not show a sharp change, and The speed of the motor should be controlled within the normal error at the request of the user. FIG. 2 is a flowchart of a fall detection for implementing the above contents as an internal program of an induction motor sensorless vector control inverter.

In the initial exciting time process of FIG. 2, the fall detector 18 does not operate as a step of forming a magnetic flux for generating torque in a state in which the brake of the motor is not opened. In the magnetic flux state inspection 21 of FIG. 2, the magnetic flux λ ^{e ^} _ds calculated by the MRAS 8 of FIG. 1 is compared with the magnetic flux λ ^{e *} _ds generated in the magnetic flux command generator 5, and the allowable error δ of the magnetic flux is set. Falling out of _λ produces fall prevention outputs. The torque state test 22 process generates a fall prevention output when the generated torque T ^{^} _e of the motor calculated by the MRAS 8 of FIG. 1 shows a sudden change exceeding a preset torque change allowable value δ _T. The speed test (23) consists of the following equations: (9), (10), (11), and the speed ω ^{^} _r of the motor calculated by the MRAS (8) is applied to the speed command generator (1). The fall prevention output is generated when the speed deviation exceeds the tolerance δ _ω in comparison with the calculated ω ^* _r .

[Equation 9]

[Equation 10]

[Equation 11]

Through the above operation, the fall detector 18 detects a state in which the speed is not normally controlled due to an error inside or outside the sensorless vector control inverter, thereby preventing the fall of the article.

As described above, the present invention further includes an overload protector 17 and a fall detector 18 in a conventional induction motor sensorless vector control inverter to prevent a fall due to malfunction and overload of the induction motor sensorless vector control inverter. It is effective in preventing damage to equipment and industrial accidents caused by preventing and transferring heavy weight.

Claims (3)

A rectifier 12 for converting an AC power into a direct current, a smoothing part 13 made up of a plurality of capacitors to smooth the direct current power rectified by the rectifying part 12, and a direct current power supply of the smoothing part 13 MRAS (8) which calculates the torque T ^{^} _e generated by the induction motor, the speed of the magnetic flux ω ^{^} _r , the direction of the magnetic flux θ ^{^} by using a switching unit 14 for converting into a power source, a mathematical model of the induction motor, The difference between the speed command generator 1 adjusted by the inverter external speed command and the speed command ω ^* _r generated by the speed command generator 1 and the speed ω ^{^} _r estimated by the MRAS 8 is input. the torque minutes instruction current i ^{e *} and the speed controller 2 to calculate a _qs, the speed controller 2, a torque minutes instruction current i ^{e *} _qs and the MRAS (8), the torque current estimated by i calculated in Torque current controller (3) for controlling torque current by inputting difference of ^{e ^} _qs And a difference between the magnetic flux command generator 5 for determining the magnitude of the magnetic flux generated in the motor, and the lambda ^{e *} _ds output from the magnetic flux command generator 5 and the lambda ^{e ^} _ds estimated by the MRAS 8. A magnetic flux controller 6 for controlling the magnetic flux of the stator as input, and a flux current setting value i ^{e *} _ds for generating magnetic flux calculated from the magnetic flux controller 6 and i estimated by the MRAS 8. ^A PWM waveform is generated by inputting a voltage calculated by the magnetic flux current controller 7 and the torque current controller 3 and the magnetic flux current controller 7 to control the magnetic flux current by inputting a difference between ^{e ^} _ds. Voltage command operator 4, two current sensors 1 (10) and current sensors 2 (11) for detecting the current of two phases of the three-phase current generated by the switching unit 14, and the two current sensors 1 (10) and the DQ side for converting the output signal of the current sensor 2 (11) into the form of the input of the MRAS (8) In the group (9) and, the induction being configured to include the voltage sensor 15 to recognize the voltage of the DC power smoothed by the smoothing unit 13, the electric motor sensorless vector control inverter, The inductive motor sensorless vector control inverter calculates the weight of the load through the torque component current i ^e _qs in the SFRF system calculated by the MRAS 8 and overloads the output when the weight exceeds the allowable weight of the machine. Generated overload protector (17), Induction motor sensorless vector control A fall detector 18 which detects a fall and generates an output when the speed is not controlled due to an abnormality inside or outside the inverter, Induction motor sensorless vector control inverter characterized in that it further comprises. The method of claim 1, The overload protector 17 includes a function of calculating the weight of the load using the equations 1, 2, 3, 4, 5, 6, 7, 8 and generating an overload output when the allowable weight is exceeded. Induction motor sensorless vector control inverter. The method of claim 1, The fall detector 18 falls when the magnetic flux λ ^{e ^} _ds calculated by the MRAS 8 deviates from the allowable error δ _λ of the set magnetic flux in comparison with the magnetic flux λ ^{e *} _ds generated in the magnetic flux command generator 5. Generates a prevention output and generates a fall prevention output when the generated torque T ^{^} _e of the motor calculated by the MRAS 8 shows a sudden change exceeding a preset torque change allowance δ _T , and is calculated by the MRAS 8. An induction motor comprising a function of generating a fall prevention output when the number of revolutions ω ^{^} _r of a given motor deviates from the allowable error δ _ω in comparison with ω ^* _r calculated by the speed command generator 1 Sensorless vector control inverter.

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