JP4406480B2 - Inverter control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction motor with a low resolution pulse generator, and more particularly to an inverter speed control system.
[0002]
[Prior art]
A conventional inverter speed control system is shown below.
FIG. 7 is a block diagram showing an example of the prior art, and FIG. 8 is a block diagram showing two examples of the prior art.
In FIG. 7, power is supplied from the power converter 1 to the induction motor 2.
The torque / magnetic flux controller 6 is a primary voltage command for controlling the output of the power converter 1 so that the torque T and the primary magnetic flux φ1 of the induction motor 2 follow a predetermined torque command value T * and a primary magnetic flux command value φ1 *. Outputs the value v1 *.
[0003]
The torque T and primary magnetic flux φ1 of the induction motor 2 input to the torque / flux controller 6 are calculated by a torque / flux calculator 9. The torque / magnetic flux calculator 9 receives the primary current i1 of the induction motor 2 that is the output of the current detector 5 and the secondary magnetic flux φ2i of the induction motor 2 that is the output of the secondary magnetic flux calculator 20. The secondary magnetic flux φ2i of the induction motor 2 is obtained by using the primary current i1 of the induction motor 2 that is the output of the current detector 5 and the rotational speed ωm of the induction motor 2 that is the output of the speed detector 3. Calculated with The speed controller 10 controls the torque command value T * so that the rotational speed ωm of the induction motor 2 follows a predetermined speed command value ωm *.
[0004]
FIG. 8 is a block diagram showing an improvement of this, and in FIG. 8, power is supplied from the power converter 1 to the induction motor 2.
The torque / magnetic flux controller 6 is a primary voltage command for controlling the output of the power converter 1 so that the torque T and the primary magnetic flux φ1 of the induction motor 2 follow a predetermined torque command value T * and a primary magnetic flux command value φ1 *. Outputs the value v1 *. The torque T and primary magnetic flux φ1 of the induction motor 2 input to the torque / flux controller 6 are calculated by a torque / flux calculator 9.
[0005]
The torque / magnetic flux calculator 9 receives the primary current i1 of the induction motor 2 that is the output of the current detector 5 and the secondary magnetic flux φ2i of the induction motor 2 that is the output of the first secondary magnetic flux calculator 8. The secondary magnetic flux φ2i of the induction motor 2 is obtained by using the primary current i1 of the induction motor 2 that is the output of the current detector 5 and the calculation speed ωm ^ that is the output of the second speed calculator 12. 8 is calculated.
The speed controller 10 controls the torque command value T * so that the calculation speed ωm ^ of the second speed calculator 12 follows a predetermined speed command value ωm *. The secondary magnetic flux φ2 of the induction motor 2 includes the primary voltage v1 of the induction motor 2 that is the output of the voltage detector 4, the primary current i1 of the induction motor 2 that is the output of the current detector 5, and the first secondary magnetic flux calculator 8. Is calculated by the second secondary magnetic flux calculator 7 using the calculated secondary magnetic flux φ2i.
[0006]
The first speed calculator 11 uses the primary current i1 of the induction motor 2 that is the output of the current detector 5 and the calculated secondary magnetic flux φ2 of the second secondary flux calculator 7 to calculate the instantaneous rotational speed of the induction motor 2. Calculate. The second speed calculator 12 corrects the calculation speed ωmc using the rotation speed ωm of the speed detector 3 and the calculation speed ωmc of the first speed calculator 11. By feeding back the calculation speed ωm ^ of the second speed calculator 12 to the speed controller 10 and the first secondary magnetic flux calculator 8, stable speed control can be performed in the speed region where the speed information from the speed detector 3 is missing. Realize.
[0007]
[Problems to be solved by the invention]
In the first secondary magnetic flux calculator 8 and the speed controller 10 of the above-described technology, the calculation speed ωm ^ that is the output of the second speed calculator 12 is used. Further, the rotational speed ωm of the speed detector 3 and the calculation speed ωmc of the first speed calculator 11 are input to the second speed calculator 12.
The calculation speed ωmc of the first speed calculator 11 is calculated using the primary current i1 of the current detector 5 and the calculation secondary magnetic flux φ2 of the second secondary magnetic flux calculator 7. Then, the calculated secondary magnetic flux φ2 of the second secondary magnetic flux calculator 7 includes the primary voltage v1 of the voltage detector 4, the primary current i1 of the current detector 5, and the calculated secondary magnetic flux φ2i of the first secondary magnetic flux calculator 8. Is calculated using. In the vicinity of the magnitude of the primary current i1 of the induction motor 2 becoming zero, the detection error included in the primary voltage v1 that is the output of the voltage detector 4 increases.
[0008]
This detection error causes a calculation error in the calculation secondary magnetic flux φ2 of the second secondary magnetic flux calculator 7. The calculation error generated in the calculation secondary magnetic flux φ2 of the second secondary magnetic flux calculator 7 causes a calculation error in the calculation speed ωmc of the first speed calculator 11, and at the same time, the calculation speed ωm ^ of the second speed calculator 12 Also causes computation errors. Since the calculation speed ωm ^ of the second speed calculator 12 causing the calculation error is fed back to the speed controller 10 or the first secondary magnetic flux calculator 8, stable and highly accurate speed control becomes difficult.
The present invention has been made in view of the above-described points, and an object of the present invention is to provide an inverter control device that solves these problems.
[0009]
[Means for Solving the Problems]
In other words, the means to achieve that purpose is
1. In claim 1,
In an inverter control device that performs vector control by a power converter that supplies power to an induction motor, a voltage detector that detects a primary voltage equivalent of the induction motor, a current detector that detects a primary current equivalent of the motor, A speed detector for detecting the rotation speed of the motor, a current comparator for comparing the absolute value of primary current information of the current detector with a set threshold value, and feedback from the output state of the current comparator to the control system A speed switch for switching speed information to be performed, a first speed calculator for calculating a rotation speed of the motor from primary voltage information of the voltage detector, primary current information of the current detector, and an electric circuit constant of the motor; , A second speed calculator for obtaining high-quality instantaneous speed information from the speed information obtained from the speed detector and the calculated speed information of the first speed calculator; A speed controller that generates a torque command value so that the calculated speed information that is force follows a predetermined speed command value, and a disturbance torque estimator from the calculated speed information that is the output of the torque command value and the speed switch. Comprising a third speed calculator configured to calculate the rotational speed of the electric motor by utilizing this,
Inverter control characterized in that the calculation speed information of the third speed calculator and the calculation speed information of the second speed calculator are inputted to the speed switch and are effectively switched and used as speed information fed back to the control system. Device.
[0010]
That is, as shown in FIG. 1 to be described later, a current comparator 15 that compares the absolute value of the primary current i1 of the current detector 5 with a set threshold value ith, and a variable sw that is an output of the current comparator 15 The speed switch 13 for switching the speed information fed back to the speed controller 10 and the first secondary magnetic flux calculator 8 according to the state, the torque command value T * which is the output of the speed controller 10 and the output of the speed switch 13 A third speed calculator 14 for calculating the rotational speed of the induction motor 2 from the calculation speed ω ^ is provided.
[0011]
2. In claim 2,
In an inverter control device that performs vector control by a power converter that supplies power to an induction motor, a voltage detector that detects a primary voltage of the induction motor, a current detector that detects a primary current equivalent of the motor, and the motor A speed detector for detecting the rotation speed of the current detector, a current comparator for comparing the absolute value of the primary current information of the current detector with a set threshold value, and a high-frequency signal contained in the output of the current comparator is removed A filter circuit, a speed switch for switching speed information to be fed back to the control system from the output state of the filter circuit, primary voltage information of the voltage detector, primary current information of the current detector, and electric circuit constants of the motor From the first speed calculator for calculating the rotational speed of the electric motor from the above, the speed information obtained from the speed detector and the calculated speed information of the first speed calculator A second speed calculator for obtaining high-quality instantaneous speed information; a speed controller for generating a torque command value so that the calculated speed information output from the speed switch follows a predetermined speed command value; and the torque A disturbance torque estimator is configured from a command value and calculation speed information that is an output of the speed switch, and a third speed calculator that calculates the rotational speed of the motor by using the disturbance torque estimator is provided.
The calculation speed information of the third speed calculator and the calculation speed information of the second speed calculator are inputted to the speed switch, and are smoothly switched based on the output of the filter circuit as speed information to be fed back to the control system. This is an inverter control device.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an embodiment of the first aspect of the present invention. In FIG. 1, a speed switch 13, a third speed calculator 14, and a current comparator 15 are provided. This is different from the conventional one shown in FIG.
The current comparator 15 determines the value of the variable sw according to the flowchart of FIG. 2 using the primary current i1 of the current detector 5 and the set threshold value ith.
[0013]
In FIG. 2, iu, iv, and iw respectively represent the u-phase current, the v-phase current, and the w-phase current of the primary current i1. When the absolute values | iu |, | iv |, | iw | of all phases of the primary current i1 of the current detector 5 are equal to or larger than the set threshold value ith, for example, a constant 4096 is substituted into the variable sw. If at least one of | iu |, | iv |, and | iw | is smaller than the set threshold value isth, for example, a constant 2048 is substituted into the variable sw.
In the flowchart of FIG. 2, the value of the variable sw is set to 2048 and 4096, but two different values are arbitrarily set.
[0014]
The third speed calculator 14 uses the torque command value T * of the speed controller 10, the variable sw of the current comparator 15, the calculation speed ω ^ of the speed switch 13, and the rotational speed ωm of the speed detector 3 to calculate the calculation speed. ωmd is obtained as shown in the block diagram of FIG.
In the block diagram of FIG. 3, the disturbance torque estimator 16 uses the torque command value T * of the speed controller 10 and the calculation speed ω ^ of the speed switch 13 to convert the estimated disturbance torque Td ^ into equation (1). Td ^ = {(T *) − J · p (ω ^)} / (p · Tc + 1) (1)
Ask more.
Here, p () represents the time differentiation of the amount in (), and J is the moment of inertia. 1 / (p · Tc + 1) represents a first-order lag filter, and Tc is a filter time constant.
[0015]
When the switch sw2 is opened, the storage device 17 stores and holds the disturbance torque estimated value Td ^ that is the output of the disturbance torque estimator 16 immediately before the switch sw2 is opened.
When the switch sw2 is closed, the output Td ^ mem of the storage device 17 outputs the disturbance torque estimated value Td ^ of the disturbance torque estimator 16 every sampling period.
The switch sw2 opens and closes depending on the value of the variable sw of the current comparator 15. The switch sw2 is opened when the value of the variable sw of the current comparator 15 is 2048, and is closed when the value is 4096.
That is, when the absolute values | iu |, | iv |, | iw | of all phases of the primary current i1 of the current detector 5 are equal to or larger than the set threshold value ith, the switch sw2 is closed, and | iu |, | If at least one of iv | and | iw | is smaller than the set threshold value isth, the switch sw2 is opened and the disturbance torque estimator Td ^ of the disturbance torque estimator 16 is stored in the storage device 17.
[0016]
The fourth speed calculator 18 uses the torque command value T * of the speed controller 10, Td ^ mem that is the output of the storage device 17, and the rotational speed ωm of the speed detector 3 to calculate the calculated speed ωmd from equation (2). Ωmd = 1 / J · ∫ {(T *) − Td ^ mem} dt (2)
Ask more.
When a pulse is generated from the pulse generator, the integral initial value of equation (2) is corrected to the rotational speed ωm of the speed detector 3.
The calculation speed ωmd, which is the output of the fourth speed calculator 18, becomes the output of the third speed calculator 14. The speed switch 13 uses the calculation speed ωm ^ of the second speed calculator 12, the calculation speed ωmd that is the output of the third speed calculator 14, and the variable sw of the current comparator 15 to calculate the calculation speed ω ^ in FIG. Ask as shown.
[0017]
In FIG. 4, when the value of the variable sw of the current comparator 15 is 2048, that is, any one of absolute values | iu |, | iv |, | iw | of all phases of the primary current i1 of the current detector 5 If it is smaller than the set threshold value isth, the switch sw1 is switched to the calculation speed ωmd side of the third speed calculator 14, and the calculation speed ω ^ of the speed switch 13 outputs the calculation speed ωmd of the third speed calculator 14.
When the value of the variable sw of the current comparator 15 is 4096, that is, when | iu |, | iv |, | iw | is equal to or greater than the set threshold value ith, the switch sw1 is operated at the second speed calculator 12. The speed is switched to the ωm ^ side, and the calculation speed ω ^ of the speed switch 13 outputs the calculation speed ωm ^ of the second speed calculator 12.
[0018]
In the vicinity of the magnitude of the primary current i1 of the induction motor 2 becoming zero, that is, one of the absolute values | iu |, | iv |, | iw | of all phases of the primary current i1 of the current detector 5 is set. Instead of the calculation speed ωm ^ of the second speed calculator 12 that caused a calculation error due to the detection error included in the primary voltage v1 of the voltage detector 4 when the threshold value is smaller than the threshold value ith, the third speed calculator 14 The calculation speed ωmd is fed back to the speed controller 10 and the first secondary magnetic flux calculator 8.
[0019]
Since the calculation speed ωmd of the third speed calculator 14 is not affected by the detection error included in the primary voltage v1 of the voltage detector 4, stable and highly accurate speed control can be realized. The calculation speed ωmd of the third speed calculator 14 is calculated on the assumption that the actual disturbance torque does not fluctuate in the vicinity of the magnitude of the primary current i1 of the induction motor 2 becoming zero. Therefore, a calculation error occurs in the calculation speed ωmd of the third speed calculator 14 due to the estimation error generated in the disturbance torque estimation value Td ^ of the disturbance torque estimator 16 due to the fluctuation of the actual disturbance torque. When a pulse is generated from the pulse generator, the integrated initial value of the equation (2) is corrected to the rotational speed ωm of the speed detector 3 so that the calculation speed ωmd of the third speed calculator 14 varies due to fluctuations in the actual disturbance torque. The calculation error that occurs in the system is reduced.
[0020]
Next, claim 1 is an improvement of claim 1.
That is, in claim 1, if the absolute value of the primary current i1 of the current detector 5 is smaller than the set threshold value ith, the variable SW outputs 2048, and the absolute value of the primary current i1 of the current detector 5 is set. If the threshold value isth or more, 4096 is output.
When the variable SW of the current comparator 15 is 2048, the speed switch 13 feeds back the calculation speed ωmd of the third speed calculator 14 to the speed controller 10 and the first secondary magnetic flux calculator 8, and the third speed calculator 14, the estimated disturbance torque value is stored in the storage device.
When the variable SW of the current comparator 15 is 4096, the speed switch 13 feeds back the calculation speed ωm ^ of the second speed calculator 12 to the speed controller 10 and the first secondary magnetic flux calculator 8 to calculate the third speed calculation. The device 14 does not store the estimated disturbance torque in the storage device.
[0021]
In fact, since there is a noise component in the primary current i1 of the induction motor 2, the variable SW of the current comparator 15 is arbitrarily set near the threshold value ith of the primary current i1 of the induction motor 2. The two set values are output alternately. Therefore, the speed switch 13 cannot smoothly switch the speed information fed back to the speed controller 10 or the first secondary magnetic flux calculator 8.
Further, the third speed calculator 14 cannot smoothly store the disturbance torque estimated value in the storage device. In the vicinity where the magnitude of the primary current i1 of the induction motor 2 becomes the set threshold value ith, it is difficult to stably control the speed switch 13 and the third speed calculator 14 by the variable SW of the current comparator 15. This leads to deterioration of speed control characteristics. A configuration that eliminates these points will be described below.
[0022]
FIG. 5 is a block diagram showing an embodiment of the second aspect of the present invention. The difference from FIG. 1 is that a filter circuit 19 is provided.
The filter circuit 19 uses the variable SW of the current comparator 15 to obtain the variable SWf by the following equation.
SWf = SW / (p * TSW + 1) (3)
Here, p represents time differentiation. 1 / (p * TSW + 1) represents a first-order lag filter, and TSW is a filter time constant.
[0023]
6 (a) and 6 (b) are characteristic diagrams showing the state of the current comparator variables and the filter circuit variables in FIG. 5. In FIG. 6, the magnitude of a phase of the primary current i1 of the induction motor 2 is shown. The state of the variable SW of the current comparator 15 and the variable SWf that is the output of the filter circuit 19 in the vicinity of the set threshold value ith is shown, and when the state shifts from a state larger than the threshold value ith to a smaller state. Represents.
[0024]
Since there is a noise component in the primary current i1 of the induction motor 2, the variable SW of the current comparator 15 is arbitrarily set near the threshold value ith of the primary current i1 of the induction motor 2. Two values, 4096 and 2048, are output alternately.
The variable SWf of the filter circuit 19 is an output obtained by passing the variable SW of the current comparator 15 through the first-order lag filter expressed by the equation (1), and changes smoothly as shown in FIG. 6B.
When the speed switch 13 and the third speed calculator 14 are controlled using the variable SW of the current comparator 15, the speed switch 13 feeds back speed information to the speed controller 10 and the first secondary magnetic flux calculator 8. Cannot be switched smoothly. Further, the third speed calculator 14 cannot smoothly store the disturbance torque estimated value in the storage device.
[0025]
When the variable SWf of the filter circuit 19 is controlled and the value of the variable SWf is 4096, the speed switch 13 uses the speed controller 10 or the first secondary magnetic flux calculator as the calculation speed ωm ^ of the second speed calculator 12. Feedback to 8.
If the third speed calculator 14 does not store the estimated disturbance torque in the storage device, the speed switch 13 calculates the third speed calculator 14 when the value of the variable SWf deviates from 4096. The speed ωmd is fed back to the speed controller 10 and the first secondary magnetic flux calculator 8, and the third speed calculator 14 stores and holds the estimated disturbance torque in the storage device.
[0026]
Therefore, the speed switch 13 can smoothly switch the speed information fed back to the speed controller 10 and the first secondary magnetic flux calculator 8. Further, the third speed calculator 14 can smoothly store the disturbance torque estimated value in the storage device.
By using the variable SWf of the filter circuit 19 for the control of the speed switch 13 and the third speed calculator 14 in the vicinity where the magnitude of the primary current i1 of the induction motor 2 becomes the set threshold value ith, speed control characteristics are obtained. Can be prevented.
[0027]
【The invention's effect】
As described above, according to the present invention, the absolute value | iu |, | iv | of all phases of the primary current i1 of the current detector 5 is in the vicinity where the magnitude of the primary current i1 of the induction motor 2 becomes zero. , | Iw |, the calculation speed ωm of the second speed calculator 12 that caused a calculation error due to a detection error included in the primary voltage v1 of the voltage detector 4 when the threshold value is smaller than the set threshold value isth. Instead of ^, the calculation speed ωmd of the third speed calculator 14 is fed back to the speed controller 10 and the first secondary magnetic flux calculator 8, so that stable and highly accurate speed control can be realized. It can prevent the speed control characteristics from deteriorating, and is extremely useful in practice.
In addition, although this detailed description demonstrated the structure which comprises the 1st, 2nd, 3rd speed calculator for easy understanding, even if the 2nd speed calculator of Claim 1 or 2 is not required, Of course, the present invention functions effectively.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the first aspect of the present invention.
FIG. 2 is a flowchart for explaining the current comparator of FIG. 1;
FIG. 3 is a detailed view of a third speed calculator of FIG. 1;
4 is a detailed view of the speed switch of FIG. 1. FIG.
FIG. 5 is a block diagram showing an embodiment of the second aspect of the present invention.
6 is a characteristic diagram showing a state of variables of the current comparator and filter circuit of FIG.
FIG. 7 is a block diagram showing a conventional example.
FIG. 8 is a block diagram showing two conventional examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Power converter 2 Induction motor 3 Speed detector 4 Voltage detector 5 Current detector 6 Torque / flux controller 7 Second secondary flux calculator 8 First secondary flux calculator 9 Torque / flux calculator 10 Speed control 11 First speed calculator 12 Second speed calculator 13 Speed switch 14 Third speed calculator 15 Current comparator 16 Disturbance torque estimator 17 Storage device 18 Fourth speed calculator 19 Filter circuit 20 Secondary flux calculator

Claims (2)

In an inverter control device that performs vector control by a power converter that supplies power to an induction motor, a voltage detector that detects a primary voltage of the induction motor, a current detector that detects a primary current equivalent of the motor, and the motor A speed detector for detecting the rotation speed of the current detector, a current comparator for comparing the absolute value of primary current information of the current detector with a set threshold value, and a feedback to the control system from the output state of the current comparator A speed switch for switching speed information; a first speed calculator for calculating the rotational speed of the motor from primary voltage information of the voltage detector; primary current information of the current detector; and an electric circuit constant of the motor; A second speed calculator for obtaining instantaneous speed information from the speed information obtained from the speed detector and the calculated speed information of the first speed calculator; and an output of the speed switch. A speed controller that generates a torque command value so that the speed information follows a predetermined speed command value, and a disturbance torque estimator configured from the torque command value and the calculated speed information that is the output of the speed switch. A third speed calculator for calculating the rotational speed of the electric motor by utilizing it,
Inverter control characterized in that the calculation speed information of the third speed calculator and the calculation speed information of the second speed calculator are inputted to the speed switch and are effectively switched and used as speed information fed back to the control system. apparatus. In an inverter control device that performs vector control by a power converter that supplies power to an induction motor, a voltage detector that detects a primary voltage of the induction motor, a current detector that detects a primary current equivalent of the motor, and the motor A speed detector for detecting the rotation speed of the current detector, a current comparator for comparing the absolute value of the primary current information of the current detector with a set threshold value, and a high-frequency signal contained in the output of the current comparator is removed A filter circuit, a speed switch for switching speed information to be fed back to the control system from the output state of the filter circuit, primary voltage information of the voltage detector, primary current information of the current detector, and electric circuit constants of the motor From the first speed calculator for calculating the rotational speed of the electric motor from the above, the speed information obtained from the speed detector and the calculated speed information of the first speed calculator A second speed calculator for obtaining instantaneous speed information; a speed controller for generating a torque command value so that the calculated speed information as an output of the speed switch follows a predetermined speed command value; A disturbance torque estimator is constructed from the calculated speed information that is the output of the speed switch, and a third speed calculator that calculates the rotational speed of the electric motor by using the disturbance torque estimator is provided.
The calculation speed information of the third speed calculator and the calculation speed information of the second speed calculator are inputted to the speed switch, and are smoothly switched based on the output of the filter circuit as speed information to be fed back to the control system. An inverter control device characterized by:

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