JPH10164883A - Inverter control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inverter control apparatus by which the rated voltage of a lifting motor is increased up to a power-supply voltage and by which the costs of the lifting motor and of an inverter for drive are lowered, by a method wherein, even when the DC voltage of a main circuit is lowered due to a change in the power-supply voltage, the output voltage waveform of the inverter is not distorted. SOLUTION: The required DC voltage, of a main circuit, which is computed by a required-DC-voltage computing part 22 on the basis of a voltage instruction to be outputted from a current regulator(ACR) 17, and an actual DC voltage which is detected by a voltage detector 20 are compared by a comparison part 23, and their difference Δv is computed. Then, when the DC voltage of the main circuit becomes lower than the required DC voltage, the correction amount ΔΦof a magnetic-flux instruction Φo according to the difference Δv is computed by a magnetic-flux-correction-amount computing part 24, the magnetic-flux instruction Φo is corrected, an exciting current is adjusted downward, and the output voltage of an inverter is lowered so that a voltage waveform is not distorted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a vector control inverter control device that drives an induction motor and controls speed.

[0002]

2. Description of the Related Art In recent years, with the advance of control technology, many electric motors of industrial machines have become AC motors driven by inverters, and among them, a vector control system capable of obtaining the same control performance as a DC motor has been widely adopted. .

Hereinafter, the application will be described by taking an AC elevator apparatus as an example. FIG. 3 is a diagram showing the overall configuration of a conventional general vector control system, wherein 1 is a three-phase AC power supply, 2 is a converter for converting AC power supply to DC, and 3 is a smoothing capacitor for smoothing the output of this converter. And 4, an inverter for converting the output of the converter 2 into an alternating voltage variable frequency alternating current;
5 is a current detector for detecting the output current of each phase of the output of the inverter 4; 6 is an induction motor fed by the inverter 4 to drive the elevator; 7 is a pulse generator;
Is a sheave of a hoist driven by the induction motor 6, 9 is a main rope wound around the sheave 8, 10 is a car connected to the main rope 9, 11 is a counterweight, and 12 is an ideal speed. A speed pattern generating circuit for outputting a pattern, 13 is an F / V converter, 14 is an ASR (speed regulator), 15 is a vector control circuit, and 16 is a magnetic flux command Φo for setting an exciting current.
Is a magnetic flux command setting circuit, 17 is an ACR (current regulator), 18 is a PWM circuit (pulse width modulation circuit), and 19 is a base drive circuit of an inverter element.

In the above configuration, during elevator operation, the output of the AC power supply 1 is rectified into DC through the converter 2 and the smoothing capacitor 3, and is again converted into the variable voltage and variable frequency AC power by the inverter 4. Thereby, the induction motor 6 is driven, and the elevator is operated.

On the other hand, the control of the inverter 4 is controlled according to the speed pattern output from the speed pattern generation circuit 12. That is, in the control method, the speed of the induction motor is fed back from the pulse generator 7 through the F / V converter 13, and the deviation between the fed-back induction motor speed and the speed pattern is input to the ASR 14 and amplified to become a torque command. , Which are input to the vector control circuit.

The vector control circuit 15 inputs the rotation angle of the induction motor 6 from the pulse generator 7 based on the theory of vector control, and uses the excitation current component based on the magnetic flux command and the torque command as an AC vector. A current command having a phase that can be controlled independently of each other is output so that the torque current component set in the above-described manner maintains the orthogonal state and is controlled in the same manner as a separately excited DC machine.

Next, the deviation between the current command from the vector control circuit 15 and the actual current detection value from the current detector 5 is amplified by the ACR 17 to become a voltage command for the inverter 4. , And the base drive circuit 19 switches the semiconductor elements constituting the inverter 4 to supply AC power of a variable voltage and a variable frequency to the induction motor 6 for control.

[0008]

In general, in the case of an induction motor driven directly by a commercial power supply, when the power supply voltage decreases, the rotating magnetic field weakens, so that the temperature of the motor increases and the generated torque decreases due to an increase in the inflow current. . There is no particular problem if this is within the allowable range of the motor and the load. However, in the case of the induction motor driven by the vector control inverter as described above, the inverter torque control is performed by output current control (excitation of motor current, torque Therefore, even if the output voltage required for control cannot be generated due to a drop in power supply voltage or the like, the current control loop operates to allow the command current to flow as much as possible. Distortion occurs.

In the inverter control elevator, since the occurrence of torque ripple and the deterioration of torque control performance due to the waveform distortion described above lead to a decrease in running performance, the output of the inverter can be caused by a power supply voltage fluctuation or other voltage drop factors. The rated voltage of the hoisting motor is determined on the assumption that the voltage drops, and for example, the rated voltage of the motor for a 200 V system power supply is set to 170 V.

[0010] This is a special voltage setting for ensuring the running performance. For this reason, the winding specification of the electric motor is special, and the general-purpose motor (rated voltage 2
00V) cannot be used. In addition, since it is necessary to cope with an increase in current accompanying a decrease in the rated voltage of the motor, it is necessary to increase the current capacity of the inverter, resulting in an increase in cost.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and the features of the present invention are voltage detecting means for detecting a DC voltage of a main circuit, and voltage detecting means for the main circuit. Means for comparing the required DC voltage with the DC voltage detected by the DC detection means and calculating the difference (undervoltage); and calculating the amount of correction of the magnetic flux command in accordance with the value of the undervoltage. Means.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a DC voltage of a main circuit is detected by a voltage detector and compared with a required DC voltage calculated from a voltage command of an inverter. And the difference (undervoltage)
The correction amount of the magnetic flux command is calculated in accordance with the above equation, and the magnetic flux command is corrected to reduce the output voltage of the inverter so that the voltage waveform of the inverter is not distorted even when the DC voltage of the main circuit is reduced.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of the present invention.
0 is the DC voltage of the main circuit (terminal voltage of the smoothing capacitor 3)
A voltage detector 21 for detecting V1 functions as means for calculating a difference (undervoltage) Δv between the required DC voltage V2 of the main circuit and the actual DC voltage V1, and a magnetic flux according to the value of the undervoltage Δv. This is a microcomputer that realizes a function as a magnetic flux correction amount calculating unit that calculates a correction amount ΔΦ of the command Φo. The microcomputer 21 calculates a required DC voltage V2 of the main circuit necessary for the inverter to output a required voltage waveform without distortion from a voltage command of the ACR 17, and a required DC voltage calculation unit 22;
And the actual DC voltage V1 to calculate a difference Δv, and a magnetic flux correction amount calculation unit 24 that calculates a magnetic flux command correction amount ΔΦ according to the insufficient voltage Δv.
In addition, the same components as those in FIG. 3 are denoted by the same reference numerals.

In the above configuration, normally, the DC voltage V1 of the main circuit is higher than the DC voltage V2 required for the inverter to output a sine wave voltage waveform without distortion, and therefore it is not necessary to weaken the exciting current. Correction amount of magnetic flux command ΔΦ
Becomes 0, but the DC voltage V1 of the main circuit decreases due to fluctuations in the power supply voltage and the like, and when the DC voltage V2 falls below the required DC voltage V2, the difference Δ
v is calculated by the comparison unit 23, and a correction amount ΔΦ corresponding to the Δv is calculated by the magnetic flux correction amount calculation unit 24 and output. As a result, the magnetic flux command Φo is reduced by ΔΦ, that is, the exciting current is reduced by that amount, and the output voltage of the inverter is also reduced to prevent the output voltage waveform from being distorted.

Next, a processing procedure for calculating a magnetic flux correction amount executed by software in the microcomputer 21 will be described with reference to a flowchart of FIG.

First, in step S1, the DC voltage V1 of the main circuit is detected, and in step S2, the required DC voltage V2 at that time is calculated from the voltage command of the ACR 17. Here, the required DC voltage V2 can be calculated as the absolute value of its peak value, that is, V2 = | Vac peak value |, assuming that the voltage command is Vac (sine wave).

Next, at step S3, Δv, which is the difference between V2 and V1, is calculated, and the correction amount ΔΦ of the magnetic flux as shown in FIG. 1 is determined at step S4 and thereafter according to the value of Δv. First, in step S4, it is determined whether Δv is larger than a predetermined value a. If Δv is equal to or smaller than the predetermined value a, the excitation current does not need to be weakened, so that the correction amount ΔΦ = 0 in step S5. If Δv
Is larger than the predetermined value a, the upper limit value b is set in step S6.
It is determined whether or not it is greater than
In step S8, the correction amount ΔΦ is output so that the correction amount ΔΦ is proportional to Δv, that is, as follows: ΔΦ = c (Δva) / (ba). If Δv exceeds the upper limit value b, the correction amount ΔΦ is set to the upper limit value c in step S7, so that the exciting current does not drop extremely.

In this way, when the DC voltage of the main circuit falls below the required DC voltage, the magnetic flux command Φo output from the magnetic flux command generating device is adjusted downward according to the shortage, and as a result, the inverter Is also reduced, and the vector control is performed without causing distortion in the output waveform.

In the above description, when the excitation current is adjusted downward and the motor voltage is lowered, the current increases at approximately the same rate and the motor loss increases, but such operation is performed under the following four conditions. In the case of a variable load that repeatedly drives and regenerates, such as an elevator, the proportion of the period during which the excitation weakening control is required is small when viewed from the entire operation cycle, and the effect on the motor temperature rise is small. .

(1) The power supply voltage drop is large. (2) The direction of the load is the drive side. (3) The load is heavy. (4) The motor speed is near the rating.

In particular, in the acceleration / deceleration region where a large current flows and the motor generation loss is large, the motor speed does not reach the rating, so that it is not necessary to weaken the excitation, and the regenerative operation occupying about half of the elevator operation cycle. Since the DC voltage of the main circuit sometimes rises, it is not necessary to weaken the excitation.
Therefore, according to the present invention, even if the excitation is weakened, the influence on the motor temperature is small, and there is no particular problem.

[0022]

According to the present invention, a general-purpose motor having the same rated voltage as the power supply voltage can be used for a hoist. In addition, by increasing the rated voltage of the motor, the effective current in consideration of the maximum current during acceleration and the duty cycle is also reduced, leading to a reduction in the capacity of the inverter, resulting in a significant cost reduction in the elevator hoist motor and the drive inverter. Down can be planned.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of the present invention.

FIG. 2 is a flowchart illustrating a processing procedure for calculating a magnetic flux correction amount according to the present invention.

FIG. 3 is a diagram showing an overall configuration of a conventional vector control inverter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-phase AC power supply 2 Converter 3 Smoothing capacitor 4 Inverter 5 Current detector 6 Induction motor 10 Car 12 Speed command generation circuit 14 ASR 15 Vector control circuit 16 Magnetic flux command generation circuit 17 ACR 18 PWM circuit 19 Base drive circuit 20 Voltage detector Reference Signs List 21 microcomputer 22 required DC voltage calculation unit 23 comparison unit 24 magnetic flux correction amount calculation unit

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Hayashi 1-28-10 Sho, Ibaraki-shi, Osaka Inside Fujitec Co., Ltd.

Claims (1)

[Claims] 1. An inverter control device comprising: a converter for converting AC power to DC power; and an inverter for converting the DC power into an AC having an arbitrary variable voltage and variable frequency by vector control and supplying power to an induction motor. ,
Voltage detection means for detecting the DC voltage of the main circuit, means for comparing the required DC voltage of the main circuit with the DC voltage detected by the DC detection means, and calculating the difference (undervoltage);
A magnetic flux correction amount calculating means for calculating a correction amount of the magnetic flux command according to the value of the undervoltage.