JPS5963982A - Controlling method for variable frequency inverter - Google Patents

Abstract

PURPOSE:To enable to variably control the frequency of an inverter due to software by storing in advance the operating frequency of the inverter as a frequency table, thereby reducing the external units. CONSTITUTION:The DC power from a converter 1 is converted by a transistor type voltage inverter 2 into AC power of variable frequency and variable voltage and supplied to a synchronous motor 3. An inverter control such as a PWM control software program is stored in the ROM55 of a microcomputer 5, various parameters, data such as analog and digital signals from the inverter 2 and data for calculation are stored in an RAM54, and a CPU56 obtains an inverter control signal in accordance with the program using these data.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 1ltlJ control method for a variable frequency inverter using a microcomputer as the control center, and particularly to a control method for sine wave traverse operation.

Variable speed operation of an induction motor or synchronous motor using a variable frequency inverter is applied, for example, to traverse operation in a fiber winding section, and is a speed that has a frequency change that repeatedly increases and decreases in quantity or sinusoidally around a set i degree. be controlled.

ζThe variable frequency control device used in such a variable frequency control device has traditionally been a pure hardware configuration using an analog system, partly due to the safety factor, but recently, with the advancement of digital equipment, micro A digital system with a computer as the central control unit is being adopted. However, when the traverse is not operating, in order to change the set speed from time to time, a high-speed calculation element (L
SI) etc., and calculation of trigonometric functions by Taylor expansion is required, resulting in a complicated and expensive 110 control device.

Also, inverter! When controlling an electric motor, there is a problem in that the Taylor expansion calculation requires a computer capable of high-speed processing due to the time limit of functional calculation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method that enables variable frequency control by software with a reduced number of external devices by storing the operating frequency of an inverter in advance as a frequency table.

FIG. 1 is a block diagram showing an embodiment of the present invention.

The DC power obtained from the converter 1 is converted back into variable frequency, variable voltage AC power by the transistor voltage type inverter 2, and is supplied to the synchronous motor or induction motor 3, and the load 4 of the motor 3. It operates in a sine wave traverse that increases and decreases in a sine wave shape around the set frequency. The gate control signal of inverter 2 is controlled by microcomputer 5.
Depending on the control method of inverter 2, the voltage side of converter 1 (signal 41 may also be given from microcomputer 5).
given from. Also, to protect inverter 2,
The microcomputer 5 receives a short-circuit overflow signal based on the current detection of the smoothing capacitor 6 and a load short-circuit detection signal based on the load' current detection. These detection signals are for the inverter ■10 interface 5 of the microcomputer 5.
．． , and you will be asked to pass line 52.

The frequency settings of the inverter 2 are set on the operation panel 7 using the settings A: A and 6 for the fundamental frequency and a maximum frequency change amount A to specify the sine wave traverse waveform shown in Figure 2. , is given as the frequency change period B. Further, from the operation panel 7, the ratio v/y of the inverter output voltage 2, which has a constant ratio to the fundamental frequency fs, and the frequency F is set. These settings 11i fs, A, B
, V/F is I10 interface 5 for operation panel
It is guided to pass line 5□ through s.

ROM 5 of the microcomputer 5 * Ic Binper □ A software program for evening control, for example, PWM control, is stored in the RAM 5. is set to the above-mentioned setting value f8.
A.

B, V/F: Data storage of parameters of @, analog and digital signals from the inverter 2, etc., and data storage for calculation are performed, and CPU5. Now, use these data to obtain the inverter output control signal according to the program.

Here, ROM5. also stores a sine wave table, 0
PU5a uses this sine wave table and the aforementioned setting value f6mA.
, B to achieve sinusoidal traverse operation using the inverter output frequency fout and this frequency f. Obtain data on the inverter output voltage Vout from ut and the set value V/F. This will be explained in detail below.

For the sine wave traverse operation shown in FIG.
Output frequency font and output 'paper pressure■. ut is obtained from the following equations (1) and (2).

fout=fs+As1n(Bt)−
,,...(1) ■out = (v/F) xf
ont...---(2) Here, the fundamental frequency f
E1. Maximum frequency change amount A.

It is set in advance on panel 7. Therefore, the microcomputer 5 calculates equations (1) and (2) to obtain fout,
■Out control data can be obtained, and in this calculation, the sine wave calculation of the second term on the right side of equation (1) is performed using ROM5+
1: Obtained from sample data using the included sine wave table.

ROM5. Sine wave sample data from 0 to π/2 radians of the sine wave is written in , and the sine values from π/2 to 2π are determined using the theorem of trigonometric functions.

The sine wave sample data is written in units of 0.01 radian as its minimum unit, and the sine value S is written in the following relationship.

In this table, ROM5. When writing data to , the decimal point cannot be inserted, so S<N> is multiplied by 10' (iM), and when calculating the above equation (1), it is multiplied by 10 so that the decimal point unit can be maintained. When calculating values, when the value is a fraction less than the minimum unit of 0.01 radian in the table, for example θ = (B t) = o, o23 radians, use the linear approximation method to find the value of S .

In the embodiment, the sine wave table stores sine values from 0 to π/2 radian in units of 0.01 radian, but this is done in units of 0.001 radian in order to reduce calculation accuracy, that is, output distortion. It is also possible to subdivide the R
OM5. storage capacity up to an acceptable range.

・In addition, although the example shows a case where the frequency is changed in a sinusoidal manner, the present invention is not limited to this.
The complicated speed from acceleration to stop of an elevator is difficult to calculate, except in cases where it can be calculated by simple calculations without relying on a table, such as a triangular wave.

This makes it suitable for controlling special frequency patterns such as -.

As described above, according to the present invention, when the output frequency of an inverter and the output voltage having a negative relationship with the frequency have a special pattern such as a sine wave, the pattern does not need to be obtained from a sloppy calculation. , a constant specifying the pattern, 1
Since a table is provided that reads the corresponding sample data group from the ROM based on the thread count setting value, the calculation time of the N microcomputer is greatly reduced, and one external calculation element circuit is not required, resulting in a relatively accurate frequency. , 'Voltage control is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing setting values for reading out a sine wave table in the present invention. DESCRIPTION OF SYMBOLS 1...Converter, 2...Inverter, 3...Electric motor, 4...Load, 5...Microcomputer,
7...Operation panel. Figure 1 Figure 2 455

Claims (1)

[Claims] In a variable frequency inverter with a microcomputer as the control center, each set value such as the cycle and peak value for specifying the summerization pattern of the output frequency of the inverter is given to the microcomputer, and the microcomputer inputs sample data of the own pattern. The variable frequency converter has a table written in a ROM, and when the set value is given, sample data of the table corresponding to the set value is sequentially read out to sequentially set the output frequency of the inverter. How to control frequency inverter.