JPH1127998A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the stoppage of an inverter device, when the control of the device is switched to V/F constant control from vector control due to the detection of an abnormal speed by smoothly performing a control switching. SOLUTION: An inverter device is operated under a closed loop condition by normal speed control 12 and vector control 13-35 and when an abnormal speed is detected, under an open loop condition by a V/F constant control 36. The V/F constant control block 36 is provided with a means, which decides an output angular frequency ω by using a set speed Ns as an output frequency command, a means which computes a primary voltage V1 based on a preset V/F ratio by using the set speed Ns as an output frequency command ω', a means which computes two shaft current components of an exciting current shaft and a torque current shaft from the angle ϕbetween the primary voltage V1 and the exciting current shaft and the primary voltage V1 , and a means which corrects voltage quantities Vd and Vq, the angle ϕ, a phase θ, and the output angular frequency ω, so that voltage control will not become discontinuous when the control of the inverter device is switched. When an abnormal speed is detected, the control of the device is switched so that a signal given to a voltage waveform generating circuit 37 does not change abruptly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Inverter device that attaches a detector and performs closed-loop speed control and vector control of the motor based on the detection signal. More specifically, it relates to an inverter device that switches the control method and continues operation when an error occurs in the speed detector. It is.

[0002]

2. Description of the Related Art In vector control, the linearization of torque can be controlled in the same manner as a DC motor by independently controlling the primary current of an electric motor, which is an AC amount, into an excitation current and a torque current. This is a control method of the induction motor.

Conventionally, the configuration of a speed control and vector control system of a slip frequency control method will be described.

FIG. 2 shows a TI equivalent circuit of an induction motor. This is equivalent to a T-type equivalent circuit of an induction motor which has been conventionally used, and the secondary leakage inductance is apparently concentrated on the primary side. FIG. 3 is a vector diagram using the exciting current as a reference axis with reference to FIG.

The signals shown in FIGS. 2 and 3 are shown below. I ₁ : Primary current I ₀ : Excitation current I _T : Torque current L ₁ : Primary inductance M ': Equivalent excitation inductance L _σ : Primary conversion leakage inductance R ₁ : Primary resistance R ₂ ': Equivalent 2 Secondary resistance V ₁ : Primary voltage V _q : Excitation component of primary voltage V _d : Torque component of primary voltage θ: Voltage phase.

In order for the excitation component current I ₀ and the torque component current _IT to always be orthogonal, the condition of the slip angular frequency ω _S is obtained by the following equation. ω _S = (R ₂ / M ′) · ( _IT / I ₀ ) (1) Each axis component of the primary voltage can be expressed by the equations (2) and (3). _{V d = RI · I 0 -ωL} σ · I T ... (2) V q = ωL 1 · it 0 + R 1 · I T ... (3) vector control by the vector condition is met can be realized.

FIG. 4 shows a configuration example of the vector control.
1 is a vector controlled PWM inverter (main circuit),
2 is an induction motor driven by an inverter, 3 is a pulse generator provided on the rotating shaft of the motor, 4 is a speed detection circuit that outputs a speed detection Nd and a speed detection angular frequency ωr from this pulse generator, and 12 is a speed setting Ns. Speed controller that calculates the difference between the speed and the speed detection Nd.

Reference numerals 13 to 35 denote vector operation circuits, and 13 (1
5 to 24) are non-interference calculation units, 15 and 18 are multiplication circuits for multiplying the exciting current setting I ₀ * by the primary resistance R ₁ and the primary inductance L ₁ , respectively, and 16 and 17 are from the speed controller 12 respectively. A multiplication circuit for multiplying the torque component current command I _T * by the leakage inductance L _σ and the primary resistance R ₁ ,
Reference numeral 9 denotes a slip frequency calculation circuit for obtaining a slip frequency ωs from the excitation current setting I ₀ * and the torque component current command I _T *, and reference numeral 20 denotes an addition for adding the speed detection angular frequency ωr and the slip frequency ωs to output a speed output angular frequency ω. vessel, respectively 21 and _22, ωL σ I _T * and ωL ₁ I ₀ * to obtain multiplier multiplying the velocity output angle frequency ω to the multiplication result of the multiplier circuit 16 and 18, 23 to the multiplier 15 and 21 of An adder that takes the difference between the multiplication results and outputs a torque component component command V _d * of the primary voltage, and outputs an excitation component command V _q * of the primary voltage by taking the sum of the multiplication results of the multipliers 17 and 22. Adder.

Reference numeral 25 denotes output currents iv to iw of the inverter 1.
Is converted to a two-phase current of d- and q-axis coordinates, and 31 is an excitation current setting I ₀ * and a coordinate conversion circuit 2
PI calculation of the deviation from the d-axis excitation current detection I ₀ from 5
Variation Δ of the torque component of the primary voltage that brings the deviation closer to 0
D-axis current controller for outputting the V _d, 32 is a torque current command I _T * and the q-axis torque current detection I _T and deviation PI calculation to the primary voltage to approximate the deviation to zero from the coordinate transformation circuit 25 A q-axis current controller that outputs a change ΔV _d of the excitation component of the current.

Reference numeral 33 denotes a torque component component command V of the primary voltage.
_d * is added with a change ΔV _d to obtain a torque component V _{d of the} primary voltage.
And outputs an adder, 34 is energized minute component V of the primary voltage by adding the change amount [Delta] V _d to the excitation minute component command V _q * of the primary voltage
An adder that outputs _q , 35 is an integrator that outputs the voltage phase θ by integrating the speed output angular velocity ω, and 37 is a torque component V _{d of the} primary voltage obtained by a vector control operation.
And based on the exciting component V _q and the velocity output angular frequency ω and voltage phase theta, a PWM circuit for generating a PWM pattern for controlling the inverter 1.

[0011]

In the above-described conventional control of the slip frequency system, accurate detection of the motor speed is a prerequisite for the control, so that the speed detector 3 is damaged or the detection line is disconnected. If the correct speed of the motor cannot be detected, control cannot be continued. Therefore, in a normal device, when an abnormality is detected in the speed detection system, the inverter device stops by failure. Further, in a device that cannot detect a speed detection abnormality, the speed becomes unstable.

However, in a final system or device incorporating an inverter, in an emergency, there may be a case where it is desired to continuously operate the system even without a high response realized by vector control. For example, in a mixer or the like that drives a motor with an inverter to stir the material, a variable speed is required, but if the motor stops during the stirring of the material, there is a risk that all the material will be unusable,
There are times when it is desirable to continue rotation even in an emergency (when speed detection is abnormal).

To solve the above problem, it is effective to switch the vector control to a control that does not require a speed sensor (for example, V / F control or sensorless vector control) when a speed detection abnormality is detected. However, simply switching the control method causes an overcurrent detection abnormality due to discontinuity of the output voltage phase or the like, and stops.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inverter device which can eliminate discontinuity due to a difference in control method associated with switching and can prevent the device from being stopped due to control switching.

[0015]

SUMMARY OF THE INVENTION The present invention always operates in closed loop speed control and vector control using a speed detector, and when an abnormal speed detection is detected, the open loop V / F is controlled by a constant V / F control block. In the inverter device which is operated by switching to the / F constant control, the control block includes a means for determining an output angular frequency ω using a speed setting of the speed control as an output frequency command, and a V which is determined in advance as the speed setting as an output frequency command. Primary voltage V based on / F ratio
Means for calculating ₁ and the angle φ between the primary voltage and the exciting current axis.
When means for calculating a biaxial voltage component of the exciting current axis and the torque current axis from the primary voltage V _1, at the time of V / F constant control switching from the vector control, so that the voltage controlled not discontinuous, the amount of voltage V _d , V _q , means for correcting the angle φ between the primary voltage and the exciting current axis, the phase θ, and the output angular frequency ω so that the vector control can be smoothly shifted to the V / F constant control. It is characterized by the following.

[0016]

FIG. 1 shows a configuration of a vector control system of an inverter device according to an embodiment. The same components as those shown in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, 1 is a PWM inverter, 2
Is an induction motor, 4 is a speed detection circuit, 5 is a speed detection circuit 4
Speed detection abnormality detection circuit that monitors the speed detection value from
2 is a speed controller, 13 to 35 are vector operation circuits, 36
Is a V / F constant control unit that takes in the speed setting Ns and outputs a torque component V _d ′, an excitation component V _q ′, and a voltage phase θ ′ of the primary voltage of V / F (voltage / frequency) constant control.

SW1 is a control changeover switch for switching between the torque component components _Vd and _Vd 'of the primary voltage from the vector control side and the V / F constant control side and outputting to the PWM circuit 37;
Is a control changeover switch for switching the excitation component _Vq and _Vq 'of the primary voltage to output to the PWM circuit, SW3 is a control changeover switch for switching the voltage phase θ and θ' and outputting to the PWM circuit, and SW4. Is a control changeover switch that switches between the speed output angular frequency ω from the vector control side and the speed setting ω ′ on the V / F constant control side and outputs the result to the PWM circuit.
Each is controlled by the abnormality detection signal of the speed detection abnormality detection circuit 5 to switch from the vector control side to V / F constant control.

Normally, the control changeover switches SW1 to SW4 are in the vector control side, and the inverter device is operated by closed loop speed control by vector control. If an abnormality is detected in the speed detection system during operation, the control changeover switches SW1 to SW4 are continuously operated by V / F constant control. The control switching procedure is performed as follows.

First Embodiment A control switching procedure according to a first embodiment will be described. (1) The speed detection abnormality detection circuit 5 monitors the speed detection value Nd at regular time intervals, and if the amount of change in the detection value or the insulation value shows an abnormal value continuously for a certain period of time, the speed detection abnormality is detected. Judge.

(2) The control changeover switches SW1 to SW4 are switched from the vector control side to the V / F
Switch to constant control.

(3) V _d used in the PWM circuit 37,
The initial values of V _q , θ, and ω are switched by calculating as follows. V _d , V _q , θ, and ω are calculated by vector calculation from the time of the vector control to the time immediately before the switching of the constant V / F control. When switching to the constant V / F control, if these variables change discontinuously, voltage fluctuations and current fluctuations are caused, overvoltage and overcurrent protection of the device is activated, and as a result, the device stops. To prevent this, each variable is changed as follows using the immediately preceding vector operation data at the time of switching. Vector control side variables: _Vd , _Vq , φ, θ, ω. V / F constant control variables: V _d ′, V _q ′, φ ′, θ ′, ω ′
And _{V d '= 0 V q'} = √ (V d 2 + V q 2) φ '= 90 ° θ' = θ + (90 ° -φ) ω '= ω (4) switched after the output frequency speed setting N _S Setting (F
Command) ω 'is calculated and a voltage command value V ₁ determined from the V / F ratio is calculated and passed to the PWM circuit 37 as V _q '. _Vd '= 0 _Vq ' = V1 (primary voltage command value inversely calculated from output frequency setting and V / F ratio) (5) When changing the electric motor 2, the speed setting Ns is set as the output frequency setting ω '. It is passed to the PWM circuit 27.

Second Embodiment A control switching procedure according to a second embodiment will be described.

(1) The speed detection abnormality detection circuit 5 monitors the speed detection value Nd at regular time intervals, and when the amount of change in the detected value or the absolute value continuously shows an abnormal value for a certain period of time, the speed is detected. Judge as abnormal detection.

(2) The control switches SW1 to SW4 are switched from the vector control side to the V / F constant control side based on the determination of the speed detection abnormality.

(3) V _d used in the PWM circuit 37,
The initial values of V _q , θ, φ, ω are calculated and switched as follows.

V _d , V _q , and θ are calculated by vector calculation from the time of the vector control to the time immediately before the switching of the constant V / F control. When the control is switched to the constant V / F control, if these variables change discontinuously, electric fluctuations or current fluctuations are caused, and overvoltage and overcurrent protection of the device is activated, and as a result, the device is stopped. To prevent this, each variable is changed as follows using the immediately preceding vector operation data at the time of switching. Vector control variables: _Vd , _Vq , φ, θ, ω. V / F constant control side variables: V _d ′, V _q ′, φ ′, θ ′,
ω '. _{V d '= V d V q} ' = V q φ '= φ θ' = θ ω '= ω (4) switched after the output frequency sets a speed setting Ns (F
Set) omega 'calculates a voltage command value determined from the V / F ratio is V ₁ as the voltage component V _d of the V ₁ excitation current axis' voltage component V _q of the torque current axis 'is separated into, V _d' , V _q 'to the PWM circuit 27. These two axes are orthogonal. _{V d '= V 1 · cosφ} V q' = V 1 · sinφ (5) When the variable speed motor gives a speed setting N _S as an output frequency setting omega '.

Third Embodiment A control switching procedure according to a third embodiment will be described.

(1) The speed detection abnormality detection circuit 5 monitors the speed detection value Nd at regular time intervals, and when the amount of change in the detection value or the absolute value continuously shows an abnormal value for a certain period of time,
Judge as abnormal speed detection.

(2) The control switches SW1 to SW4 are switched from the vector control side to the V / F constant control side based on the determination of the speed detection abnormality.

(3) V _d used in the PWM circuit 27,
The initial values of V _q , θ, φ, and ω are calculated and switched as follows.

V _d , V _q , and θ are calculated by vector calculation from the time of the vector control to the time immediately before the switching of the constant V / F control. If these variables change discontinuously when the control is switched to the constant V / F control, voltage fluctuation or current fluctuation is caused, and overvoltage and overcurrent protection of the device is operated, and as a result, the device is stopped. To prevent this, each variable is changed as follows using the immediately preceding vector operation data at the time of switching. Vector control variables: _Vd , _Vq , θ, φ, ω. V / F constant control side variables: V _d ′, V _q ′, φ ′, θ ′,
ω '. V _d ′ = √ (V ₀ ² + V _T ² ) V _q ′ = 0 φ ′ = 0 ° θ ′ = θ−φ ω ′ = ω (4) After switching, the speed setting Ns is changed to the output frequency setting (F
'Calculates a voltage command value V ₁ determined from the V / F ratio as, V _d' command) omega pass to the PWM circuit 27 as. V _d ′ = V ₁ (voltage command value inversely calculated from output frequency setting and V / F ratio) V _q ′ = 0 (5) When changing the speed of the motor, the speed setting Ns is given as the output frequency setting ω ′. .

As described above, each variable is changed at the time of control switching, and after the switching, the voltage command value V ₁ determined from the V / F ratio is calculated by using the speed setting Ns as the output frequency setting ω ′ and calculating _Vq ′ or Pd as V _d ′, V _q ′ or V _d ′
Since the control is passed to the M circuit and the V / F constant control is performed, the switching from the vector control to the V / F constant control becomes continuous.

[0034]

The present invention provides a control type inverter device which performs closed loop speed control and vector control using a speed detector and switches from vector control to V / F constant control when an abnormality occurs in the speed detection system. In the above, discontinuity such as a voltage phase at the time of control switching can be eliminated, and switching can be performed smoothly. Therefore, there is no need to stop the apparatus due to discontinuity such as a voltage phase, and the operation can be continued.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a vector control system including V / F constant control switching according to an embodiment;

FIG. 2 is an asymmetrical TI equivalent circuit diagram of an induction motor.

FIG. 3 is a vector diagram using an exciting current using the equivalent circuit as a reference axis.

FIG. 4 is a configuration diagram of a vector control system according to a conventional example.

[Explanation of symbols]

1 ... PWM inverter (main circuit) 2 ... induction motor 3 ... pulse generator (speed detector) 4 ... speed detection circuit 5 ... Speed detection error circuit 12 ... speed controller 13 ... noninterference computation circuit 15 ... R ₁ multiplier circuit 16 ... L _sigma multiplier circuit 17 ... R ₁ multiplication circuit 18 ... L ₁ multiplication circuit 19 ... slip frequency calculation circuit 25 ... 3-phase to two-phase coordinate conversion circuit 31 ... d-axis current controller 32 ... q-axis current controller 35 ... integrating Unit 36 V / F constant control unit 37 PWM circuit SW1 to SW4 Changeover switch Ns Speed setting Nd Speed detection ωr Speed detection angular frequency ωs Slip frequency ω Speed output angular frequency (ωr + ωs) ω 'output Frequency setting R ₁ … Primary resistance L _σ … Primary conversion leakage inductance L ₁ … Primary inductance M '… Equivalent excitation inductance I ₀ … Excitation current V _d … Torque of primary voltage A component I ₁ … Primary current V ₁ … Primary voltage _IT … Torque component current V _q … Excitation component of primary voltage.

Claims (4)

[Claims] An operation is normally performed by a closed loop speed control and a vector control using a speed detector. When an abnormal speed detection is detected, the operation is switched to an open loop V / F constant control by a V / F constant control block. In the inverter device, the control block comprises: means for determining an output angular frequency ω using a speed setting of speed control as an output frequency command;
Means for calculating the primary voltage V ₁ based on the / F ratio, and calculating the two-axis voltage components of the exciting current axis and the torque current axis from the angle φ between the primary voltage and the exciting current axis and the primary voltage V ₁ Means to perform voltage control so that voltage control does not become discontinuous when switching from vector control to constant V / F control, so that the voltage amounts V _d and V _q , the angle φ between the primary voltage and the exciting current axis, the phase θ, and the output angular frequency and a means for correcting ω, so that a smooth transition can be made from vector control to constant V / F control. 2. The method according to claim 1, wherein when an abnormal speed detection is detected, the voltage component of the exciting current axis, the voltage component of the torque current axis, and the angle, phase, and frequency of the primary voltage and the exciting voltage axis are given to the voltage waveform generating circuit. An inverter device, comprising: a switch for changing an operation result of an open loop V / F control from an operation result of vector control to each variable. 3. The method according to claim 1, wherein the angle φ between the primary voltage and the exciting current axis is V
An inverter device which retains a value at the time of switching to / F constant control. 4. The inverter device according to claim 1, wherein the angle φ between the primary voltage and the exciting current axis is 0 ° or 90 °.