JPH0637635A - Error correction method for analog input section - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting an error in an analog input section used in a device for protecting and controlling a power system, an electric device and the like.

[0002]

2. Description of the Related Art Conventionally, there are the following techniques for checking an analog input section. FIG. 2 is a diagram showing a conventional example of an analog input section, and FIG. 4 is a flowchart showing a conventional inspection method. In FIG. 2, 1 is an input transformer, 2
Is an analog filter, 3 is a multiplexer, 4 is an analog-digital (hereinafter referred to as A / D) converter, and 5 is C.
PU, 7 is an inspection input, and 9 is a switch. The analog circuit section of the device shown in FIG. 2 extends from the input transformer 1, the analog filter 2, the multiplexer 3, and the A / D converter 4. The analog circuit unit includes a fine adjustment function unit (not shown), a capacitor, and other parts that are prone to secular change, and to detect accuracy defects and circuit defects due to secular change of this part, etc. Or, the equipment is automatically inspected irregularly.

In the prior art, as shown in the flow chart of FIG. 4, when an inspection command is received from the CPU 5, in step 31, the switch 9 is closed while the system electricity quantity is still connected, and the known signal inspection input 7 is connected to the system electricity quantity. And is applied to each analog filter unit 2 in a duplicated manner. This signal whose input is sequentially switched by the multiplexer 3 is output as numerical data by the A / D converter 4 and is read by the CPU 5, respectively, and then waveform analysis is performed in step 32 to determine AC gain, offset, etc. The calculation process is performed to calculate the error. After the switch 9 is opened in step 33, the various errors calculated in step 34 are compared with the predetermined inspection failure detection level. Only when each error exceeds the inspection defect detection level, the inspection defect is output in step 35, and after the inspection, the device lock or the like is performed in step 37 as necessary.

[0004]

In such a conventional method, when the calculated various error data are in the vicinity of the inspection failure detection level, the apparatus does not detect the inspection failure, and the error of the analog circuit section is detected during the operation of the apparatus. Since the signal is output as it is included, it causes the deterioration of the device performance and causes the device performance error.

The present invention has been made in view of the above-mentioned problems of the prior art. The analog input is used to detect defects in the analog input portion by performing inspection and to perform various corrections by utilizing various calculated error data. The purpose of the present invention is to provide a method for correcting an error in a part.

[0006]

In order to achieve the above object, the present invention determines a correction value necessary for performing the correction from error data of an analog input section obtained by automatic inspection of the device, The correction value is stored in a memory so that error correction can be performed on an analog signal input during operation, and correction is performed by folding the correction value into the coefficient of the digital filter during operation. To do.

[0007]

The error is corrected by using the error data obtained by the inspection as well as the inspection of the analog input section.

[0008]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an analog input section for performing correction according to the present invention. 6 is a memory and 8 is a switch. In FIG. 1, the memory 6 is a CPU as compared with the conventional example shown in FIG.
5 and a switch 8 is provided between the input transformer 1 and the analog filter 2.

FIG. 3 is a flowchart of the error correction method according to the present invention. In FIG. 3, the inspection command is sent from the CPU 5 at regular intervals or at irregular intervals by the switch 8 and the switch 9.
Then, in step 11, the switches 8 are simultaneously opened to cut off the system electricity quantity. In the next step 12, the switch 9 is closed and a known analog signal is applied to each analog filter 2 from the inspection input 7. After the analog signals of the inspection input pass through the analog filters 2, the inputs are switched by the multiplexer 3 and are sequentially sent to the A / D converter 4. In step 13, the analog signal is converted into a digital signal by the A / D converter 4 and then sent to the CPU 5. Here, the following waveform analysis is performed.

When the sine wave Asinωt is sampled at every 30 electrical degrees of the fundamental wave, each sampling value X is expressed by the following equation. _{x n = Asinωt (1) x} n-1 = Asin (ωt-π / 6) (2) x n-2 = Asin (ωt-π / 3) (3) x n-3 = Asin (ωt-π / 2) (4) ... _xn-6 = Asin (ωt-π) (5) Using these sampling values X, the magnitude A of the sine wave
Is calculated by the following equation.

A ² = x _n ² + x _n−3 ² (6) ∵ (Asin ωt) ² + {A sin (ωt−π / 2)} ² = A ² (sin ² ωt + cos ² ωt) = A ² The fundamental wave gain after passing 2 is obtained.

The DC component (offset) contained in the output signal of the analog filter 2 is obtained by the following equation. x _n + x _n-6 (7) Further, by using Σ from the equation (7), by obtaining Σ (x _n + x _n-6 ) (8), the number of frequencies that can be removed increases, and the offset can be more accurate. It can be calculated well.

The phase difference φ is given by tanφ shown in the following equation.

[0014]

[Equation 1]

The magnitude of the harmonic component gain may be obtained in the same manner as the fundamental wave gain. Various errors are calculated for each analog filter based on the data of the fundamental wave gain, the phase difference, the offset, the harmonic wave gain and the like obtained by the above analysis. In the next step 14,
In order to minimize the interruption time of the system electric energy, the switch 9 is opened to interrupt the inspection input at this stage before the inspection is finished, and the switch 8 is closed in step 15 to start the input of the system electricity amount and then step 16 Go to. In step 16, the various errors obtained in step 13 are compared with various predetermined inspection failure detection levels, and the various errors are 1
If any of the conditions (error) ≧ (check failure detection level) is satisfied, the process proceeds to step 17, and if all the errors satisfy 0 <(error) <(check failure detection level), the process proceeds to step 20.

In response to the result of the comparison in step 16 being (error) ≧ (inspection defect detection level), in step 17 the inspection defect is output and the inspection is finished, as in the prior art. After that, in step 19, measures such as locking the device function are taken. Further, when proceeding to step 20, various correction values are calculated for each analog filter section based on various errors obtained at step 13, and are stored in the memory 6 at step 21 to finish the inspection.

According to the present invention, after completion of the inspection, various correction values stored in the memory 6 during operation of the apparatus are folded into the coefficients of the digital filter to correct various errors in each analog filter section. Even during circuit inspection, after switching the input in steps 14 and 15, step 2
Until the correction value calculation is performed with 0, various corrections are performed by the various correction values calculated last time. And step 20
In step 21, new correction values are updated and saved in the memory 6, and the correction values saved in the memory 6 are valid until the next correction value calculation is performed. Become.

[0018]

EFFECT OF THE INVENTION At the same time as determining whether or not the device can be continuously used by the automatic device inspection, the error near the inspection failure detection level, which has been treated as the device performance error in the prior art, and the error due to the secular change of the analog circuit part, etc. After the analog signal is converted into the digital signal, the correction is performed by adjusting the constant in the digital filter, so that the maintenance of the analog filter becomes unnecessary and the performance of the apparatus including the A / D conversion accuracy is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an analog input unit that performs error correction according to the present invention.

FIG. 2 is a block diagram of a conventional device with an analog input section that performs only inspection.

FIG. 3 is a flowchart of an error correction method according to the present invention.

FIG. 4 is a flowchart of an inspection method according to the related art.

[Explanation of symbols]

 1 Input Converter 2 Analog Filter 3 Multiplexer 4 A / D Converter 5 CPU 6 Memory 7 Inspection Input 8 Switch 9 Switch

Claims (1)

[Claims] 1. An analog signal is converted into a digital signal,
In an error correction method for an analog input unit of a device for processing a digital signal, error data of the analog input unit is obtained and stored in a memory as a correction value by automatic inspection of the device performed at regular intervals or irregularly. Then
An error correction method for an analog input unit, which comprises converting the analog signal into a digital signal and then correcting the error occurring in the analog input unit by using the correction value by digital processing.