JP3990044B2 - Inverter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction motor speed control system.
[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. Electric power is supplied from the power converter 1 to the induction motor 2. 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 / magnetic flux calculator 7 receives the primary current i1 of the induction motor 2 that is the output of the current detector 4 and the secondary magnetic flux φ2 of the induction motor 2 that is the output of the secondary magnetic flux calculator 6.
[0003]
The secondary magnetic flux φ2 of the induction motor 2 is obtained by using the primary voltage v1 of the induction motor 2 that is the output of the voltage detector 3 and the primary current i1 of the induction motor 2 that is the output of the current detector 4 as a secondary magnetic flux calculator. 6 is calculated. The secondary current i2 of the induction motor 2 is secondary using the secondary magnetic flux φ2 of the induction motor 2 that is the output of the secondary magnetic flux calculator 6 and the primary current i1 of the induction motor 2 that is the output of the current detector 4. Calculated by the current calculator 10.
The rotational speed ωm of the induction motor 2 is calculated using the secondary magnetic flux φ2 of the induction motor 2 that is the output of the secondary magnetic flux calculator 6 and the torque T of the induction motor 2 that is the output of the torque / flux calculator 7. It is calculated by a device (not shown).
[0004]
The speed calculator 12 determines the rotational speed ωm of the induction motor 2 and the secondary magnetic flux φ2 of the induction motor 2 that is the output of the secondary magnetic flux calculator 6 and the second of the induction motor 2 that is the output of the secondary current calculator 10. Calculation is performed using the secondary current i2. The speed controller 9 controls the torque command value T * so that the respective rotational speeds ωm of the induction motor 2 follow a predetermined speed command value ωm *.
[0005]
[Problems to be solved by the invention]
In a conventional speed calculator (not shown), for example, as described in “Speed Sensorless Vector Control of Induction Motor Using VVVF Applying Instantaneous Space Vector Theory” published in the Journal of the National Conference of the Electrical Engineering Society of Japan in 1989. The rotational speed ωm of the induction motor 2 is obtained by subtracting the slip speed from the rotational speed of the secondary magnetic flux φ2.
Information on the secondary resistance value of the induction motor 2 is necessary for the calculation of the sliding speed. However, since the secondary resistance value fluctuates due to a temperature change of the induction motor 2, a speed calculation error occurs. Here, for example, the speed calculation algorithm described in “Speed calculation method of induction machine without using secondary resistance” published in the 1993 National Institute of Electrical Engineers of Japan paper is adopted as the speed calculator 12, and a speed calculation (not shown) is performed. It is provided separately from the generator so that the influence of the secondary resistance value variation due to the temperature change of the induction motor 2 does not appear in the speed calculation result.
[0006]
The calculation speed of the speed calculator 12 is fed back to the speed controller 9 to control the speed of the induction motor 2. In the torque / magnetic flux controller 5 of the prior art, the primary magnetic flux φ1 of the induction motor 2 is made to follow the predetermined primary magnetic flux command value φ1 * so that the magnitude of the magnetic flux of the induction motor 2 is constant. Is doing.
At this time, the speed calculator 12 calculates the rotational speed ωm of the induction motor 2 using the secondary magnetic flux φ2 and the secondary current i2 of the induction motor 2. Actually, in the speed calculator 12, the rotational speed ωm of the induction motor 2 is obtained by calculating the inner product of the secondary magnetic flux φ2 and the secondary current i2 by calculating the outer product of the time differential value p (φ2) of the secondary magnetic flux φ2 and the secondary current i2. It is calculated by dividing by the result.
[0007]
Here, p () represents time differentiation of the amount in (). If the magnitude of the magnetic flux of the induction motor 2 becomes a constant value according to the control result of the torque / flux controller 5, the vector of the secondary magnetic flux φ2 of the induction motor 2 and the secondary current i2 are orthogonal, so the output of the speed calculator 12 Becomes zero, making speed calculation impossible. Generally, PWM is used for the control method of the output voltage of the power converter 1 and ripples are generated in the magnetic flux of the induction motor 2 and the magnitude thereof does not become a constant value. Calculation is possible. However, since the ripple component with respect to the fundamental wave component of the magnetic flux of the induction motor 2 is small, it is difficult to ensure the accuracy of the speed calculation result by the speed calculator 12. Further, since the ripple generated in the magnetic flux of the induction motor 2 with the high response of the torque / flux controller 5 due to the high switching frequency of the power converter 1 and the high speed of the control cycle is suppressed, the speed calculation is performed. The speed calculation by the device 12 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 device that solves these points.
[0008]
[Means for Solving the Problems]
In other words, the means to achieve that purpose is
In an inverter device that performs speed sensorless vector control with 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 of the induction motor, A secondary magnetic flux calculator for calculating a secondary magnetic flux of the induction motor from primary voltage information of the voltage detector and primary current information of the current detector, and calculated secondary magnetic flux information of the secondary magnetic flux calculator and the current detection From the secondary current calculator for calculating the secondary current of the induction motor from the primary current information of the generator, the calculated secondary current information of the secondary current calculator and the calculated secondary flux information of the secondary flux calculator A speed calculator for calculating the rotation speed of the induction motor, a calculation for calculating the torque and magnetic flux of the induction motor from the calculated secondary magnetic flux information of the secondary magnetic flux calculator and the primary current information of the current detector A magnetic flux calculator, a torque / flux controller for controlling the output of the power converter so that the calculated torque information and the calculated magnetic flux information of the torque / flux calculator follow a predetermined torque command value and the magnetic flux command value; A speed controller that generates the torque command value so that the calculated speed information of the speed calculator follows a predetermined speed command value, and an AC component generator that superimposes an AC component on the magnetic flux command value. It is an inverter device.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an embodiment of the present invention, and parts having the same reference numerals as those in FIG. 2 are parts having the same configuration and function. Further, the difference from FIG. 2 is that an AC component generator 11 is provided.
In FIG. 1, an alternating current component such as a sine wave function, a triangular wave function, and a rectangular wave function is output from the alternating current component generator 11, and is superimposed as a ripple component on the primary magnetic flux command value φ1 *. The AC component generator 11 can be configured by software using digital signal processing such as a digital filter.
[0010]
Depending on the control result of the torque / flux controller 5, a ripple component based on the AC component output from the AC component generator 11 appears in the magnetic flux of the induction motor 2. Since the phase component that the secondary magnetic flux φ2 of the induction motor 2 and the vector of the secondary current i2 are orthogonal does not hold due to the ripple component generated in the magnetic flux of the induction motor 2, the speed calculation by the speed calculator 12 becomes possible.
[0011]
【The invention's effect】
As described above, according to the present invention, since the output of the AC component generator 11 can be superimposed on the primary magnetic flux command value φ1 *, a ripple can be generated in the magnetic flux of the induction motor 2. Speed calculation can be performed reliably.
Since the AC component generator 11 can be configured by software using digital signal processing such as a digital filter, it is excellent in expandability with respect to an existing system.
Further, by adjusting the amplitude value of the AC component output from the AC component generator 11 to be large, the accuracy of the speed calculation result by the speed calculator 12 can be improved. realizable.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Power converter 2 Induction motor 3 Voltage detector 4 Current detector 5 Torque / flux controller 6 Secondary flux calculator 7 Torque / flux calculator 9 Speed controller 10 Secondary current calculator 11 AC component generator 12 Speed Computing unit

Claims (1)

In an inverter device that performs speed sensorless 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 of the induction motor, A secondary magnetic flux calculator for calculating a secondary magnetic flux of the induction motor from primary voltage information of the voltage detector and primary current information of the current detector, and calculated secondary magnetic flux information of the secondary magnetic flux calculator and the current detection From the secondary current calculator for calculating the secondary current of the induction motor from the primary current information of the generator, the calculated secondary current information of the secondary current calculator and the calculated secondary flux information of the secondary flux calculator A speed calculator for calculating the rotational speed of the induction motor, a calculation for calculating the torque and magnetic flux of the induction motor from the calculated secondary magnetic flux information of the secondary magnetic flux calculator and the primary current information of the current detector A magnetic flux calculator, a torque / flux controller for controlling the output of the power converter so that the calculated torque information and the calculated magnetic flux information of the torque / flux calculator follow a predetermined torque command value and the magnetic flux command value; A speed controller that generates the torque command value so that the calculated speed information of the speed calculator follows a predetermined speed command value, and an AC component generator that superimposes an AC component on the magnetic flux command value. Inverter device.

Images