JP4274618B2 - Inverter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter device, and more particularly to a speed control system for an induction motor using a low-resolution pulse generator.
[0002]
[Prior art]
FIG. 2 shows a block diagram of an example of the prior art, which will be described below with reference to this figure. In FIG. 2, electric power is supplied to the induction motor 2 from the power converter 1. The torque / magnetic flux controller 5 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 of the induction motor 2 and the primary magnetic flux φ1 input to the torque / flux controller 5 are calculated by the torque / flux calculator 7. The torque / flux calculator 7 receives the primary current i 1 of the induction motor 2 that is the output of the current detector 4 and the secondary flux φ 2 i of the induction motor 2 that is the output of the secondary flux calculator 6. 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 4 and the rotational speed ωm of the induction motor 2 that is the output of the speed detector 3 to obtain the secondary magnetic flux calculator 6. Calculated with The speed controller 8 controls the torque command value T * so that the rotational speed ωm of the induction motor 2 follows a predetermined speed command value ωm *.
[0003]
[Problems to be solved by the invention]
The secondary magnetic flux calculator 6 and the speed controller 8 of the prior art use the rotational speed ωm of the induction motor 2 that is the output of the speed detector 3. The rotational speed ωm of the induction motor 2 is detected by the speed detector 3 based on information from the speed sensor.
As a speed sensor, a pulse generator adapted for digital control is generally used. In addition, an inexpensive low-resolution pulse generator is used in terms of cost. Actually, the rotational speed ωm of the induction motor 2 is detected by the speed detector 3 as follows.
Within the sampling period, the rotational speed ωm of the induction motor 2 is detected using the number of pulses generated from the pulse generator and the measurement time. When the rotational speed of the induction motor 2 is reduced, the number of pulses generated from the pulse generator decreases within the sampling period, and at a very low speed, no pulse is generated from the pulse generator within the sampling period. In addition, when a low-resolution pulse generator is used, the rate at which no pulses are generated within the sampling period increases. In the speed region where no pulse is generated from the pulse generator within the sampling period, it is impossible to detect the instantaneous rotational speed of the induction motor 2 for each sampling period. Therefore, it becomes difficult to perform stable speed control due to the speed detection error included in the output of the speed detector 3.
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 device that solves these problems.
[0004]
[Means for Solving the Problems] In other words, means for achieving the purpose are:
1. In claim 1,
In an inverter 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 induction motor, The rotation speed of the induction motor is determined from a speed detector that detects the rotation speed of the motor, primary voltage information that is the output of the voltage detector, primary current information that is the output of the current detector, and an electric circuit constant of the induction motor. A corrected speed is obtained using a first speed calculator to be calculated, speed information obtained from the speed detector, and an average value of the calculated speed information obtained from the first speed calculator, and the corrected speed is used. in the inverter apparatus characterized by being composed of a second speed calculator configured to calculating the instantaneous speed information by correcting the operation speed information obtained from the first speed calculator That.
[0005]
2. Regarding claim 2,
The calculation of the calculation speed information obtained from the first speed calculator includes a first secondary magnetic flux for calculating a secondary magnetic flux of the induction motor from the primary current information, the instantaneous speed information, and an electric circuit constant of the induction motor. A second computing unit that computes the secondary magnetic flux of the induction motor from the first computing secondary magnetic flux information obtained from the first secondary magnetic flux computing unit, the primary voltage information, the primary current information, and the electric circuit constant of the induction motor; A configuration in which the calculation speed information is calculated from the secondary magnetic flux calculator, the second calculation secondary magnetic flux information obtained from the second secondary magnetic flux calculator, the primary current information, and the electric circuit constant of the induction motor. The inverter device according to claim 1.
[0007]
That is, in the prior art shown in FIG. 2, a voltage detector 9 that detects a primary voltage v1 of the induction motor 2 shown in FIG. 1 to be described later, a primary voltage v1 of the voltage detector 9, and a primary current i1 of the current detector 4 The second secondary magnetic flux calculator 10 for calculating the secondary magnetic flux φ2 of the induction motor 2 from the calculated secondary magnetic flux φ2i of the first secondary magnetic flux calculator 11, the primary current i1 and the second speed calculator of the current detector 4 13, the first secondary magnetic flux calculator 11 for calculating the secondary magnetic flux φ2i of the induction motor 2 from the calculation speed ωm ^, the calculated secondary magnetic flux φ2 of the second secondary magnetic flux calculator 10 and the primary current of the current detector 4. a first speed calculator 12 for calculating the rotational speed of the induction motor 2 from i1, and a second speed calculation for correcting the calculated speed ωmc from the rotational speed ωm of the speed detector 3 and the calculated speed ωmc of the first speed calculator 12. A device 13 is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described based on the block diagram of FIG.
In FIG. 1, the voltage detector 9, the second secondary magnetic flux calculator 10, the first secondary magnetic flux calculator 11, the first speed calculator 12, and the second speed calculator 13 are provided. Different.
The first speed calculator 12 uses the calculated secondary magnetic flux φ2 of the second secondary magnetic flux calculator 10 and the primary current i1 of the current detector 4 to express the calculation speed ωmc in the following equation (1).
ωmc = p (φ2) −R2 · M · (φ2d · i1q−φ2q · i1d) / L2 / (φ2d · φ2d + φ2q · φ2q) (1)
Ask more. Here, i1d and i1q are components of the primary current i1, and φ2d and φ2q are components of the calculated secondary magnetic flux φ2. P () represents time differentiation of the amount in (). R2 is a secondary resistance, M is a mutual inductance, and L2 is a secondary self-inductance.
[0009]
The second speed calculator 13 calculates high-quality instantaneous speed information and uses the rotational speed ωm of the speed detector 3 and the calculated speed ωmc of the first speed calculator 12 to calculate the calculated speed ωm ^ (2 )
ωm ^ = ωmc + {ωm [k] − (Σωmc [m]) / n} (2)
Ask more. Here, k in ωm [k] represents a time series in which pulses are generated from the pulse generator, and the rotational speed ωm is detected from the speed detector 3 for each time series. Further, m in ωmc [m] represents a time series in which vector control is executed.
[0010]
In the example of the formula (2), the vector control is executed n times from the time when the pulse is generated from the pulse generator and the number of pulses is updated, and the calculation speed ωmc is added n times by Σωmc [m]. Yes. Then, the average value is obtained using (Σωmc [m]) / n and the n-point calculation speed ωmc.
As another means, there is a method of obtaining two points of the calculation speed ωmc when the pulse is generated from the pulse generator and obtaining the average value. In addition, there is a method of obtaining an average value by applying a statistical process such as a moving average or a least-squares method to an n-point calculation speed ωmc between pulses of the pulse generator. The second secondary magnetic flux calculator 10 uses the primary voltage v1 of the voltage detector 9, the primary current i1 of the current detector 4 and the calculated secondary flux φ2i of the first secondary flux calculator 11 to calculate the calculated secondary flux φ2. Is shown in equation (3),
φ2 = ∫ {(v1−R1 · i1) · L2 / M− (L1 · L2 / MM) · p (i1) −K · (φ2−φ2i)} dt (3)
Ask more.
Here, R1 is a primary resistance, L1 is a primary self-inductance, and K is a drift compensation gain.
[0011]
The first secondary magnetic flux calculator 11 uses the primary current i1 of the current detector 4 and the calculation speed ωm ^ of the second speed calculator 13 to indicate the calculated secondary magnetic flux φ2i in the equation (4).
φ2i = ∫ (M / L2 / R2 / i1-R2 / L2 / φ2i
+ J · ωm ^ · φ2i) dt (4)
Ask more. Here, j represents a rotation matrix.
In the speed region where the rotation speed of the induction motor 2 becomes low and no pulse is generated from the pulse generator within the sampling period, the instantaneous value of the induction motor 2 calculated every sampling period (every vector control period) by the equation (2) Is fed back to the speed controller 8 and the first secondary magnetic flux calculator 11 to achieve stable speed control.
[0012]
【The invention's effect】
As described above, according to the present invention, the instantaneous rotational speed ωm ^ of the induction motor 2 is calculated for each sampling period (for each vector control period) using the equation (2) to calculate the speed controller 8 or the first secondary. By feeding back to the magnetic flux calculator 11, stable speed control can be realized even in a speed region where no pulse is generated from the pulse generator within the sampling period.
Further, the calculation speed ωmc of the first speed calculator 12 causes a calculation error due to a detection error included in the output of the voltage detector 9 or the current detector 4 or a setting error due to a parameter variation of the induction motor 2. Then, every time a pulse is generated from the pulse generator, the calculation speed ωmc is corrected using the rotational speed ωm of the speed detector 3, so that stable speed control can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of an inverter device of the present invention.
FIG. 2 is a block diagram showing an example of a prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Power converter 2 Induction motor 3 Speed detector 4 Current detector 5 Torque / flux controller 6 Secondary flux calculator 7 Torque / flux calculator 8 Speed controller 9 Voltage detector 10 Second secondary flux calculator 11 First secondary magnetic flux calculator 12 First speed calculator 13 Second speed calculator

Claims (2)

In an inverter 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 induction motor, The rotation speed of the induction motor is determined from a speed detector that detects the rotation speed of the motor, primary voltage information that is the output of the voltage detector, primary current information that is the output of the current detector, and an electric circuit constant of the induction motor. A corrected speed is obtained using a first speed calculator to be calculated, speed information obtained from the speed detector, and an average value of the calculated speed information obtained from the first speed calculator, and the corrected speed is used. An inverter device comprising: a second speed calculator configured to calculate instantaneous speed information by correcting the calculated speed information obtained from the first speed calculator .   The calculation of the calculation speed information obtained from the first speed calculator includes a first secondary magnetic flux for calculating a secondary magnetic flux of the induction motor from the primary current information, the instantaneous speed information, and an electric circuit constant of the induction motor. A second computing unit that computes the secondary magnetic flux of the induction motor from the first computing secondary magnetic flux information obtained from the first secondary magnetic flux computing unit, the primary voltage information, the primary current information, and the electric circuit constant of the induction motor; A configuration in which the calculation speed information is calculated from the secondary magnetic flux calculator, the second calculation secondary magnetic flux information obtained from the second secondary magnetic flux calculator, the primary current information, and the electric circuit constant of the induction motor. The inverter device according to claim 1.

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