KR20020016182A - Apparatus and method for diagnosing error of phase control rectifier - Google Patents

Abstract

PURPOSE: A fault diagnosis apparatus and method of a phase controlled rectifier are provided, which can diagnose the phase controlled rectifier rapidly without dissembling a device or an additional wire. CONSTITUTION: An excitation control system(30) supplying a DC voltage to a field winding(3) of a synchronous generator(1) further comprises a fault diagnosis apparatus(40) diagnosing a normal operation of a phase controlled rectifier(8) in the excitation control system. The fault diagnosis apparatus comprises a signal processor part(10) performing a noise removal and scaling by receiving a DC output voltage of the phase controlled rectifier, and an analog-digital converter(11) converting an analog signal from the signal processor part into a digital signal, and a CPU(12) performing a DFT(Discrete Fourier Transform) by receiving data from the analog-digital converter and performing a fault diagnosis as to the phase controlled rectifier according to the result of the DFT.

Description

Apparatus and method for diagnosing error of phase control rectifier}

The present invention relates to an apparatus and method for diagnosing a failure of a phase controlled rectifier, and more particularly, to an apparatus and method for quickly determining an abnormality of a phase controlled rectifier for supplying a DC current to a field winding of a generator.

In general, when the phase controlled rectifier operates normally, as shown in FIG. 1, when the DC output voltage of the phase controlled rectifier is three phase and the input frequency is f, the output waveform of the phase controlled rectifier is 6f− as shown in FIG. It becomes a DC voltage including harmonics of the order.

However, as shown in FIG. 2, when the thyristor breakdown or the gate drive circuit partially fails, the pulsating frequency component of the DC output is changed. That is, when one thyristor is short-circuited, the output waveform of the phase-controlled rectifier becomes as illustrated in FIG. 3B, and when the driving signal is not connected to the gate of the thyristors connected to one phase, only one phase is operated. The output waveform of the phase controlled rectifier is as illustrated in FIG. 3C.

In the case of a phase-controlled rectifier without a thyristor fault diagnosis device, the other healthy phase outputs more voltage, so that the effective value voltage on the DC side does not change and there is no change in the terminal voltage of the generator. Continued operation in this state causes each healthy thyristor to bear more current, resulting in increased heat generation and ultimately overall thyristor failure.

As described above, the characteristics of the thyristor element were individually examined.

In this regard, as described in Korean Patent Application No. 1997-66193 (Name: Thyristor Deterioration Diagnosis Device), the device to be diagnosed is completely stopped, the thyristor is separated from the device, and an electrical signal is applied thereto to normal semiconductor. There is a way to check whether it functions as a switch.

In another method, the voltage across each individual thyristor and the current passing through it are detected, and this state is associated with the firing signal so that the conduction signal does not become a conduction state even if there is a conduction signal or the current is not interrupted even when a reverse voltage is applied. There is a way to detect.

The former method is time consuming because the separation and wiring of the device is essential, a diagnostic device is required, and the expert must judge the result. In the latter case, only devices with the function can be diagnosed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fault diagnosis apparatus for a phase controlled rectifier for quickly diagnosing an abnormality of a phase controlled rectifier without the need for disassembling or additional wiring. There is this.

Another object of the present invention is to provide a method for diagnosing a failure of a phase controlled rectifier for quickly diagnosing an abnormality of the phase controlled rectifier without the need for disassembling or additional wiring of the device.

1 is a diagram illustrating a general output voltage waveform when the phase controlled rectifier is in normal operation.

2 is a diagram illustrating a general output voltage waveform of the phase-controlled rectifier when one thyristor fails;

3A illustrates a typical output waveform when the phase controlled rectifier is in normal operation.

3b and 3c illustrate a general output waveform when a failure occurs in the phase controlled rectifier;

4 is a configuration diagram of an excitation control system to which a fault diagnosis apparatus of a phase controlled rectifier according to the present invention is applied;

5 is an internal configuration diagram of the signal processing means shown in FIG. 4;

6 is a flowchart illustrating a fault diagnosis method of the phase controlled rectifier according to the present invention;

7 is a diagram showing the result of the Discrete Fourier Transform employed in explaining the method of the present invention;

8A is a diagram illustrating a result output of a discrete Fourier transform when the phase controlled rectifier is in normal operation;

8B and 8C are diagrams illustrating the output of the result of the Discrete Fourier Transform when a failure occurs in the phase controlled rectifier.

※ Explanation of code for main part of drawing

1: Synchronous Generator 2: Terminal Voltage

3: field winding 4: current transformer

5: transformer 6: boost transformer

7: auxiliary power transformer 8: phase controlled rectifier

9: automatic voltage regulator 10: signal processor

11: analog-to-digital converter 12: CPU

14; Transformer 15: Current Transformer

16: current transformer 30: excitation control system

40: fault diagnosis device

In order to achieve the above object, a failure diagnosis apparatus for a phase controlled rectifier according to a preferred embodiment of the present invention includes: signal processing means for performing noise removal and scaling on an input power frequency from the phase controlled rectifier; And

Each frequency component is obtained by applying a discrete Fourier transform to an output signal of the signal processing means, and whether or not the phase control rectifier is broken according to whether the maximum frequency component among the frequency components is a harmonic component of a specific order of the input power frequency. And failure determining means for determining.

According to a preferred embodiment of the present invention, a fault diagnosis method for a phase controlled rectifier includes: a first process of performing noise removal and scaling on an input power frequency from a phase controlled rectifier; And

Each frequency component is obtained by applying Discrete Fourier Transform to the signal according to the noise removing and scaling result, and the fault of the phase control rectifier depends on whether the maximum frequency component among the frequency components is a harmonic component of a specific order of the input power frequency. A second process of determining whether or not is provided.

Hereinafter, with reference to the accompanying drawings for the fault diagnosis apparatus of the phase control rectifier according to an embodiment of the present invention will be described in more detail.

4 is a block diagram of an excitation control system to which a fault diagnosis apparatus for a phase controlled rectifier according to the present invention is applied, and the excitation control system 30 for supplying a DC voltage to the field winding 3 of the synchronous generator 1 is the excitation control system. Further provided is a failure diagnosis device 40 for diagnosing whether the phase controlled rectifier 8 in the control system 30 is in normal operation.

The excitation control system 30 includes a current transformer 4 for detecting the current of the output terminal of the synchronous generator 10, a transformer 5 for detecting the voltage 2 of the output terminal of the synchronous generator 10, and The voltage inputted through the booster transformer 6, the current transformer 4 and the transformer 5, which boosts the voltage 2 of the output terminal of the synchronous generator 1 to an appropriate ratio and provides it to the outside, is compared with a voltage reference value. Automatic voltage regulator 9 for suppressing fluctuations in power voltage and outputting a constant voltage through an output terminal, and a phase controlled rectifier for controlling the phase of the output voltage of the automatic voltage regulator 9 and providing it to the field winding 3. (8) and an auxiliary power transformer (7) for supplying power to the phase controlled rectifier (8).

In addition, the failure diagnosis apparatus 40 receives the DC output voltage of the phase controlled rectifier 8 to perform noise removal and scaling, and an analog signal output from the signal processing unit 10 as a digital signal. The analog-to-digital converter 11, which converts the signal to the digital converter, and the data output from the analog-to-digital converter 11, and performs a discrete Fourier transform (hereinafter, referred to as DFT) and performs the phase according to the result of the DFT. A CUP 12 for diagnosing a failure of the control rectifier 8 is provided.

The failure diagnosis apparatus 40 is implemented to detect not only the state of the synchronous generator 1 but also the states of the automatic voltage regulator 8 and the phase controlled rectifier 8, and the state of the synchronous generator 1. In addition, in order to have no influence on the excitation control system 30 in detecting the state of the automatic voltage regulator 8 and the phase controlled rectifier 8, the transformer 14 and the current transformers 15 and 16 are electrically connected. Isolate the signal. The primary side of the transformer 14 is connected between the transformer 5 and the automatic voltage regulator 9 and the secondary side of the transformer 14 is connected to the signal processing section 10. The current transformer 15 is installed between the current transformer 4 and the automatic voltage regulator 9 to provide a DC current to the signal processing unit 10, and the current transformer 16 is connected to an output terminal of the phase controlled rectifier 8. It is installed between the field winding (3) to provide a direct current to the signal processing unit (10).

As illustrated in FIG. 5, the signal processor 10 may remove the noise included in the output of the voltage detector 20 and the voltage detector 20 that detects the DC output voltage of the phase controlled rectifier 8. A low pass filter 21 and a scaler 22 for scaling the output signal of the low pass filter 21 to match the input signal of the analog-to-digital converter 11 are provided. The signal provided to the analog-to-digital converter 11 through the scaler 22 is transmitted through the insulation amplifier 4 for electrical isolation.

The analog-to-digital converter 11 and the CPU 12 are installed on a slot of a commercial computer, and the fault diagnosis result for the phase controlled rectifier 8 performed by the CPU 12 is monitored through the monitor of the commercial computer. It may appear as a predetermined text message or as a predetermined voice message through a speaker of a commercial computer.

In the present invention, in order to determine the normal operation of the phase control rectifier 8 including the gate driving circuit as well as the thyristor element itself, instead of detecting the voltage and current of the thyristor, the DC output voltage of the phase control rectifier 8 is used. The method of detecting and analyzing its frequency spectrum is used. If the dominant frequency is a frequency component other than 6f through the analysis of the frequency spectrum of a certain section, the phase controlled rectifier 8 does not operate normally.

If the sequence signal obtained by discretizing the DC output voltage of the phase controlled rectifier 8 in the sampling period T is f (kT), the sequence signal includes a specific frequency component when the three-phase full-wave rectifier operates normally. do. That is, if the frequency of the input AC signal is f It has a harmonic component of.

In addition, in the normal operation in the magnitude of each harmonic order, the 0-order, that is, the DC component, is the most followed by the 6th order. However, when the thyristors fail, the harmonics of the order, rather than the multiples of the sixth order, become larger after the DC component. This is due to the fact that the phase controlled rectifier is fired at a constant angle and its output waveform is periodic.

When the thyristor or gate drive circuit fails, the firing is not performed at a certain point in time, so the output waveform of each firing point loses periodicity within one cycle of the power supply voltage, and is detected by frequency analysis.

DFT can be used to extract frequency components. A DFT algorithm using N sampling data can be expressed by the following equation.

here,

When the input power supply frequency is 60 Hz, a sampling period T = 1/1800 [seconds] and DFT of 30 or more includes at least one cycle of the input signal.

Therefore, the output F (n OMEGA) of the N-point DFT outputs the magnitude and phase information of the frequency component. By sampling N data at any point of time with the sampling period T and DFT, the magnitudes of the DC component and the harmonic component can be known, and it is possible to determine whether the phase control rectifier is qualitatively operated.

Due to the nature of the DFT, the phase of the input signal is not related to the magnitude of the frequency component of the output. Therefore, frequency characteristics can be known only by acquiring N data irrespective of time.

Next, a failure diagnosis method of the phase controlled rectifier according to the present invention will be described with reference to the flowchart of FIG. 6.

First, before performing the diagnostic test, the fault diagnosis device 40 may analyze data such as input power frequency (f_base), constant (1 or 3 phase), rectifier type (full wave rectification, half wave rectification, semiconverter method, etc.) of the rectifier to be tested. (Step S10).

Subsequently, the signal processor 10 in the fault diagnosis apparatus 40 acquires the DC output voltage information of the phase controlled rectifier 8 according to the start command. That is, the signal processor 10 detects the DC output voltage of the phase-controlled rectifier 8 by the voltage detector 20, and the output signal of the voltage detector 20 passes noise through the low pass filter 21. The components are removed and then scaled through scaler 22 and input to analog-to-digital converter 11 via insulation amplifier 23.

Accordingly, the analog-to-digital converter 11 converts the input analog signal into a digital signal (step S12) and sends it to the CPU 12.

The CPU 12 performs the DFT operation when the number of digital data converted and output from the analog-to-digital converter 11 reaches a value of N (YES in step S14) (step S16).

The N coefficients of F (n OMEGA) that result from an N-point DFT operation are, for example, if N = 30 and ~ T = 1/1800 Becomes That is, it appears in multiples of 60 [Hz]. Therefore, the value when n = 0 is a direct current component and the magnitude of harmonics can be known according to n. In general, the DFT gives a value of N to 2, for example, 2 ⁹ = 512 in order to use a fast FFT (Fast Fourier Transform).

Therefore, in general, each frequency component in the N-point DFT is given by the following equation.

Where m is the order of harmonics, and is 1, 2, 3, 4, 5, and 6, and x = (rounding of k + 1) of F (n OMEGA) becomes the magnitude of the harmonic component.

In practice, however, there may be variations in the input frequency, so the xth term may not necessarily be the m-order harmonic. Therefore, we use the method of finding the local maximum frequency components by using the appropriately sized region.

To find the harmonic component of the m-order, find the value of F (n OMEGA) which is the maximum within this range by using the area of [x-Δf, x + Δf] in the x value calculated above. Determined by the second harmonic component. The DFT output when N is 128 is shown in FIG. Since the value of N is the power of 2, it is calculated by the FFT algorithm, and the result is the same value symmetrically in the middle. Where m = 1 and N = 128,

If you set 2 to find the maximum value between [3, 7], the value becomes 60 [Hz] component (25 in Fig. 7), and if you set m = 6, x = 27 and [25, 29], the maximum value is the sixth harmonic component (35 in Fig. 7).

Using these maximum values, obtain the maximum value for each harmonic below the maximum harmonic order determined by the constant and rectifier method of the power supply, and select the maximum value again to determine whether this frequency is already determined fundamental wave component. (Step S18).

As a result of the determination, if the frequency determined by the final maximum value selection is a fundamental wave component that has already been determined, it is determined to be in normal operation (step S20). Otherwise, it is determined as a failure (step S22) and displayed on the screen.

That is, FIG. 8A shows that the 360 [Hz] component is next to the DC component when the phase controlled rectifier 8 operates normally, and FIG. 8B shows that the DC component is 120 [Hz] when one thyristor is short-circuited. Next, Fig. 8C shows that the component below 60 [Hz] is larger than the DC component when one phase is opened, so that the CPU 12 uses this to check for abnormality of the phase control rectifier 8. Determine.

The CPU 12 continuously executes these calculations and determination algorithms at regular intervals to determine whether the phase control rectifier 8 is abnormal.

On the other hand, in the digital voltage regulator or excitation control system, the output voltage and current of the synchronous generator and the phase controlled rectifier are always maintained by the main controller for the purpose of control. Therefore, it is possible to easily determine whether the phase control rectifier operates normally by adding an auxiliary function that performs the algorithm and the determination procedure proposed by the present invention. The advantage of this method is that no separate hardware device is needed to detect the failure of the thyristor, or even a separate hardware device can be used as a backup for the device.

According to the present invention as described above, in order to determine the normal operation of the phase controlled rectifier including the gate driving circuit as well as the thyristor element itself, by detecting the DC output voltage of the phase controlled rectifier and analyzing the frequency spectrum thereof, If the dominant frequency is a frequency component other than 6f, it is determined that the phase controlled rectifier does not operate normally, so that the operation state of the phase controlled rectifier is determined in a short time with the minimum hardware and the minimum wiring.

In addition, according to the present invention, it is possible to easily check the failure diagnosis of the phase control rectifier used in the automatic voltage regulator of the generator or the DC motor control device, and the peripheral devices such as the gate driving circuit and the signal transmission unit as well as the failure of the thyristor. In addition, it is possible to check the overall operation of the phase controlled rectifier.

In addition, when the failure diagnosis apparatus and method of the present invention is mounted on a controller of an automatic voltage regulator or a DC motor, it is possible to determine whether the phase control rectifier is normally operated without a separate detection device or circuit.

On the other hand, the present invention is not limited only to the above-described embodiments, and modifications and variations are possible without departing from the gist of the present invention, and the modifications and variations should be regarded as belonging to the following claims.

Claims (8)

Signal processing means for performing noise removal and scaling on the input power frequency from the phase controlled rectifier; And Each frequency component is obtained by applying a discrete Fourier transform to an output signal of the signal processing means, and whether or not the phase control rectifier is broken according to whether the maximum frequency component among the frequency components is a harmonic component of a specific order of the input power frequency. A failure diagnosis apparatus for a phase controlled rectifier, characterized by comprising a failure determining means for determining. The method of claim 1, The signal processing means A voltage detector for detecting a DC output voltage of the phase controlled rectifier; A low pass filter for removing noise included in an output of the voltage detector; And And a scaler for scaling the output signal of the low pass filter to match the input signal of the failure determining means. 3. The apparatus of claim 2, wherein the signal processing means further comprises an insulation amplifier electrically insulating the scaler and the failure determining means. The method of claim 1, And a maximum frequency component of each frequency component according to the discrete Fourier transform result is a frequency component having a maximum value within a predetermined error region. The method of claim 1, The frequency component of the specific order is the fault diagnosis apparatus of the phase controlled rectifier, characterized in that determined according to the constant and the rectifier method indicating the input power frequency, phase 1 or 3 phase of the phase controlled rectifier to be diagnosed. A first step of performing noise removal and scaling on the input power frequency from the phase controlled rectifier; And Each frequency component is obtained by applying Discrete Fourier Transform to the signal according to the noise removing and scaling result, and the fault of the phase control rectifier depends on whether the maximum frequency component among the frequency components is a harmonic component of a specific order of the input power frequency. And a second process of determining whether or not there is a failure. The method of claim 6, The maximum frequency component of each frequency component according to the Discrete Fourier Transform result is a frequency component having a maximum value within a constant error region. The method of claim 6, The frequency component of the specific order is a fault diagnosis method of the phase-controlled rectifier, characterized in that determined according to the constant and the rectifier method indicating the input power frequency, phase 1 or 3 phase of the phase-controlled rectifier.