JPH07311227A - Signal detector - Google Patents

Abstract

PURPOSE:To detect the signals of the terminal voltage, terminal current, effective power, reactive power, frequency and the like of a synchronous machine at a high speed and in high accuracy. CONSTITUTION:A fundamental frequency f0 of an input AC signal is detected by using a spectrum detector (FFT) 3 and a maximum spectrum-frequency detector 4 based on the output of an analog/digital converter 1. With the fundamental frequency fo as the central frequency, the signal of the fundamental frequency of the input AC signal is detected highly accurately with an adaptive bandpass filter 6, which is set at the specified pass-band width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal detecting device,
In particular, in a synchronous machine exciter, voltage, current, and
The present invention relates to a signal detection device that detects signals such as active power, reactive power, and frequency.

[0002]

2. Description of the Related Art In a conventional device of this type, when a control signal necessary for control is detected from an alternating current signal, a signal obtained by digitizing the alternating current signal through an analog / digital converting device is taken in Signal detection was carried out using this method (Japanese Patent Laid-Open No. 05-282771).

[0003]

In the above-described conventional apparatus, it is impossible to detect a signal with high precision due to a quantization error that occurs when the AC signal to be detected is subjected to analog / digital conversion.

Further, if a filter is used to average the quantization error, a multi-stage low-pass filter is required to obtain sufficient averaging, and there is a problem that the response required for control cannot be obtained. .

Further, since the filter for averaging the quantization error is a filter having a fixed center frequency, there is a problem that an erroneous signal is output when the frequency of the synchronous machine changes.

The present invention has been made in view of the above circumstances, and has been made in view of the terminal voltage, terminal current, active power, and
An object of the present invention is to provide a signal detection device capable of detecting signals such as reactive power and frequency at high speed and with high accuracy.

[0007]

A signal detecting apparatus according to the present invention comprises a frequency detecting means for detecting an approximate value of a fundamental frequency of an AC signal, an analog / digital converting means for analog / digital converting the AC signal, Based on the bandpass filter having the approximate value of the fundamental frequency as the center frequency based on the detection output of the frequency detection means and the output signal of the analog / digital conversion means as the input signal, and the signal extracted by the bandpass filter And a signal detecting means for detecting an AC signal.

Further, in the signal detecting apparatus of the present invention, the frequency detecting means captures the output signal of the analog / digital converting means and performs spectrum analysis on the frequency spectrum, and a frequency spectrum analysis result of the spectrum detecting means. And a maximum spectrum frequency selecting means for selecting a frequency at which the vector becomes maximum based on
The bandpass filter is an adaptive bandpass filter.

Further, the signal detecting apparatus of the present invention removes the ripple component contained in the detection output of the frequency detecting means 1
A second delay filter is provided between the frequency detecting means and the adaptive bandpass filter.

Further, the signal detecting device of the present invention takes in a system fault detecting means for detecting a power system fault and a detection output of the system fault detecting means, and based on the detected output, the frequency is maintained for a certain period after the occurrence of the system fault. The present invention is characterized by including control means for locking the detection output of the detection means and holding the detection value before the occurrence of the system fault.

Further, the signal detecting apparatus of the present invention comprises frequency detecting means for detecting an approximate value of the fundamental frequency of the three-phase AC signal,
A plurality of analog / digital converting means for analog / digital converting the three-phase alternating current signal for each phase, and an approximate value of a basic frequency as a center frequency based on a detection output of the frequency detecting means, and each analog / digital converting means. A plurality of adaptive bandpass filters using the output signal of the means as an input signal, and a signal detection means for detecting a three-phase AC instantaneous value signal based on the signals extracted by the plurality of adaptive bandpass filters. Characterize.

Further, the signal detecting apparatus of the present invention comprises: an output signal of the adaptive bandpass filter;
The digital value of the AC signal to be detected, which is the output signal of the digital converting means, is compared, and if there is a deviation of a predetermined value or more, the analog / digital signal is used instead of the output signal of the adaptive bandpass filter. It is characterized by further comprising signal switching selection means for selecting a signal so that the output signal of the conversion means is directly used without passing through the adaptive bandpass filter.

[0013]

In the signal detecting device having the above-mentioned structure, the frequency having the maximum spectrum, that is, the input AC signal is converted from the input signal (AC signal) digitized by the analog / digital converting device by the maximum spectrum detecting device which is the frequency detecting means. Calculate the approximate value of the fundamental frequency. By applying the output signal of the analog / digital conversion device to an adaptive bandpass filter whose center frequency is the fundamental frequency of the input AC signal detected by the maximum spectrum detection device, a high frequency quantum generated during analog / digital conversion is applied. It is possible to detect only the AC signal of the fundamental frequency from which the conversion error is almost completely removed. By using this detection signal, it is possible to detect the voltage effective value, current effective value, active power, reactive power, frequency, etc. required for control with extremely high accuracy.

On the other hand, if the frequency selection characteristic of the adaptive bandpass filter is sharpened in order to extract the fundamental wave component of the input AC signal with high accuracy, the transient response characteristic in the time domain deteriorates. In the present invention, a function of constantly monitoring the input signal and the output signal of the adaptive bandpass filter is provided, and when the absolute value of the difference between the input signal and the output signal of the adaptive bandpass filter is a certain value or more, analog / digital conversion is performed. By using the output of the device for control as it is and using the output of the adaptive bandpass filter when the absolute value of the difference between the input signal and the output signal of the adaptive bandpass filter is less than a certain value, high-speed and high-precision Enables signal detection.

Further, when a system fault such as a short-circuit item or a ground fault item occurs, there is a risk that the frequency or the like will be detected as an abnormal value due to the phase imbalance and the superimposed DC component of the AC input signal. Therefore, in the present invention, the system fault detection device is provided by utilizing the rate of change of voltage and current, the range of variation, or the armature reaction, so that the update of the detection value of the frequency detection is stopped when the system fault occurs, and the detection value before the accident is stopped. By holding, it is possible to prevent the abnormal value from being detected.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of the signal detecting device according to the present invention. In the figure, the signal detection device comprises an analog / digital conversion device 1, a maximum spectrum detection device 2, an adaptive bandpass filter 5, and an AC signal detection device 6.

The maximum spectrum detector 2 comprises a spectrum detector 3 and a maximum spectrum frequency selector 4.

The spectrum detector 3 analyzes the frequency spectrum of the input signal. Further, the maximum spectrum frequency selection device 4 selects the spectrum frequency f ₀ that maximizes the spectrum intensity based on the frequency spectrum analysis result of the spectrum detection device 3, that is, the frequency of the fundamental wave of the input AC signal. Here, the spectrum detection device 3 can be realized by using a fast Fourier transform device.

Further, the adaptive band pass filter 5
Is set to have a predetermined pass band width centered on the fundamental frequency f ₀ selected by the maximum spectrum frequency selection device 4.

The AC signal detecting device 6 may be, for example, any one of a voltage detecting device, a current detecting device, an active power detecting device, a reactive power detecting device, a frequency detecting device and the like.

In the above structure, when the AC input signal x is inputted to the analog / digital converter 1, the input signal x is converted into a digital value, and the AC signal converted into the digital value is converted into the maximum spectrum detecting device 2 And the adaptive bandpass filter 5 respectively.

The spectrum detection device 3 performs frequency spectrum analysis on the digitized AC signal input to the maximum spectrum detection device 2, and the maximum spectrum frequency selection device 4 determines that the spectrum intensity is maximum based on the analysis result. The selected spectrum frequency f ₀ , that is, the frequency of the fundamental wave of the AC input signal x is selected and output to the adaptive bandpass filter 5.

In the adaptive band pass filter 5, the center frequency is set to a filter characteristic of a predetermined pass band width with the fundamental frequency f ₀ of the input AC signal x as the center frequency based on the output signal of the maximum spectrum frequency selection device 4. . As a result, the output signal of the analog / digital converter 1 has a harmonic band component other than the fundamental wave, a waveform distortion, a DC component, a quantization error at the time of the analog / digital conversion by the analog / digital converter 1 due to the adaptive bandpass filter 5. The AC signal detecting device 6 is removed, and the signal can be detected with high accuracy.

The adaptive bandpass filter 5 is realized by the following known method. That is, the transfer function when the input signal of the adaptive band pass filter 5 is x and its output signal is y is shown in the following equation.

[0025]

[Equation 1]

Here, K is determined by the amount of stopband attenuation,
When K = 1000, the amount of attenuation is 60 dB. Next, A (z) in the equation (1) can be expressed by the following equation.

[0027]

[Equation 2]

K ₁ in the equation (2) can be expressed by the following equation.

[0029]

[Equation 3]

[0030] Equation (2), to determine the bandwidth of the pass band by K ₂ in (3), determines the center frequency by K ₁ shown in equation (3). In the equation (3), f ₀ is the center frequency and H is the sampling period.

Next, the configuration of another embodiment of the signal detecting apparatus according to the present invention is shown in FIG. The present embodiment is different from the embodiment shown in FIG. 1 in that a first-order lag filter 7 is provided between the maximum spectrum detection device 2 and the adaptive bandpass filter 5, and other configurations are the same. Since it is exactly the same, duplicate description will be omitted.

In the synchronous machine, the rate of change of frequency is sufficiently smaller than the sampling period H. Therefore, there is no problem even if the detection of the center frequency f ₀ of the adaptive bandpass filter 5 is delayed. In this embodiment, the first-order lag filter 7 is provided after the maximum spectrum detection device 2 to remove the ripple component of the center frequency detection value f ₀ and prevent the center frequency of the adaptive bandpass filter 5 from excessively fluctuating. And can be operated stably.

When the pass band of the adaptive band pass filter is adjusted so that a strict center frequency is not required, the time between adjacent zero-cross points of the AC input signal is measured as a substitute for the maximum spectrum detector 2. By doing so, it is possible to use a frequency detection device that detects the frequency.

Next, FIG. 3 shows the configuration of another embodiment of the signal detecting apparatus according to the present invention. In a synchronous machine, a three-phase AC signal having a phase difference of 120 ° can be used. Therefore, FIG.
Separately for each of the three phases as shown in
A more accurate signal is obtained by extracting the AC instantaneous value of the fundamental wave component of each of the three phases by the adaptive band pass filter 5 whose center frequency is the frequency detected by Detection can be performed.

Next, FIG. 4 shows the structure of the main part of the signal detecting device according to the present invention. The present embodiment takes into consideration that the input signal, which is a detection reference, can respond at a high speed when the input signal suddenly changes, and specifically, the magnitude of the deviation between the input signal and the output signal of the adaptive band pass filter 5 is considered. According to the above, either the output value of the adaptive band pass filter 5 or the output signal of the analog / digital conversion device which is the input value thereof is selectively output.

An output signal (x) from an analog / digital converter (not shown in FIG. 4) and an output value of the adaptive band pass filter 5 are set to the signal switching selection circuit 10.
If the deviation is within a constant value ε, the switches SW1 and SW2 are switched so as to select the output value of the adaptive bandpass filter 5, and the fundamental wave component of the input AC signal is extracted. Is the output signal y.

When the deviation is equal to or more than a constant value ε, it is assumed that the input signal suddenly changes, and the output signal of the analog / digital conversion apparatus 1 is bypassed without passing through the adaptive bandpass filter 5 in order to realize a high-speed response. Is an output signal of the signal switch selection circuit 10 (not shown) (corresponding to the AC signal detection device 6 in FIG. 1).
By switching the switch SW1 and the switch SW2 so that the input signal is input to, the response delay due to the adaptive bandpass filter 5 is eliminated, and high-speed signal detection becomes possible.

According to the above-described embodiment, during normal operation, high speed and highly accurate signal detection is possible. However, when the input signal itself to be detected becomes abnormal, such as when a system fault occurs, there is a problem that an abnormal value is detected even by using the signal detection device of each of the above embodiments. That is, when a system accident such as a short circuit accident or a ground fault occurs,
Each phase component of the AC signal becomes unbalanced, and a transient DC component is superimposed on this AC signal. In such a case, the maximum spectrum detection device 2 shown in FIG. 1 may not operate normally and may give an incorrect center frequency f ₀ to the adaptive bandpass filter 5. However, as described above, since the actual speed change of the generator does not occur rapidly, there is no problem even if the central frequency f ₀ of the adaptive bandpass filter 5 is fixed during the occurrence of the system fault. In consideration of this point, in another embodiment of the present invention, a system fault detection device for detecting the occurrence of the system fault is newly installed, and during the system fault occurrence,
The update of the center frequency f ₀ of the adaptive bandpass filter 5 which is the output of the maximum spectrum detection device 2 is configured to be locked.

Next, FIG. 5 shows the construction of an embodiment of the system fault detection apparatus. In the figure, the system fault detection device is composed of an effective value detection circuit 12 that detects the effective value of the generator current Ig, an incomplete differentiation circuit 13, a comparator 14, and an AND gate 15. When a system fault occurs in the above configuration, the effective value of the generator current Ig and the field current If rapidly increase in a stepwise manner. Therefore, the change increments are extracted from these outputs by the incomplete differentiation circuits 13 and 13, the comparators 14 and 14 detect that these values have exceeded a certain value, and the AND gate 15 detects these AND conditions. The occurrence of a system fault is detected by taking this.

Here, the effective value of the generator current is I _G.
The AND condition that both the increments of the effective value I _G of the generator current and the field current If are equal to or greater than a certain value is used because the generator current Ig or the field current If is rapidly increased due to a failure of the control device. This is because there is a possibility that Since the effective value I _G of the generator current and the field current If are detected from different different signal input sources, erroneous detection of a system fault does not occur when the control device has a single failure. Therefore, by using the system fault detection apparatus according to the present embodiment, it is possible to detect a system fault with high reliability.

Here, the generator current Ig of the synchronous machine and the field current If were used as input signals of the system fault detection device, but other signals such as the phase voltage effective value, current effective value, field current If, etc. are used. Any combination of may be used.

Further, in addition to the rate of change of the input signal, a signal superposed by the armature reaction when a system fault occurs may be detected and the system fault may be generated. For example, it is detected that a DC component is superimposed on the generator terminal current or an AC component is superimposed on the field current.If these values exceed a certain value, it is considered that a system fault has occurred, and You may make it detect an accident.

Next, FIG. 6 shows the construction of an embodiment of the armature reaction detecting device. In the figure, the armature reaction detection device is composed of a low-pass filter 16, a comparator 17, a band-pass filter 18, an effective value detection device 19, a low-pass filter 20, a comparator 21, and an AND gate 22. .

In the above configuration, the direct current component of the generator current Ig is detected by the low pass filter 16, and the comparator 17 detects that this value has exceeded a certain value.

The AC effective value of the one-side field current If is detected by the band pass filter 18, the effective value detecting device 19 and the low pass filter 20, and the comparator 21 detects that this value has exceeded a certain value.

Further, the AND gate 22 sets the AND condition of the comparators 17 and 21 to detect the occurrence of the armature reaction.

The detection of the armature reaction is carried out by the generator current Ig.
Although either the field current If is sufficient, in the present embodiment, in order to improve the reliability of the detection operation of the armature reaction, the AND output of the generator current Ig and the field current If is used to detect the occurrence of the system fault. Is configured to do.

The effects of the present invention will be specifically described. In FIG. 1, the adaptive bandpass filter 5
The characteristic is that in the formulas (1), (2) and (3), the center frequency f ₀ and the sampling period H are f ₀ = 50 Hz and H = 0.001.
K = 1000, K ₁ = -0.866 as 664Sec, the frequency response characteristic shown in FIG. 7 when K ₂ = 0.9.

Further, as the analog / digital converter 1 shown in FIG. 1, for example, the input signal voltage ± 10 V is converted into a value of ± 2000, and when the effective voltage value of the input signal is set to 5 V, the AC signal is detected. A frequency detector is used as the device 6, and the input signal is a signal in which 5% of the 7th harmonic is applied to the fundamental wave of 50 Hz. At this time, if the frequency is detected without using the adaptive band pass filter 5, the frequency is detected as 54.207 Hz to 45.804 Hz as shown in FIG.

On the other hand, when the adaptive band pass filter is used, it can be detected as 50.021 Hz to 49.981 Hz. That is, it can be seen that the detection error is improved to 0.04%, compared with 8.4% when the adaptive bandpass filter is not used.

Further, FIG. 9 and FIG. 10 show the voltage detection characteristics of the signal detecting device depending on the presence or absence of the signal switching selection circuit 10 in the embodiment shown in FIG. 4 when the input signal suddenly changes. In each of the voltage detection characteristics shown in FIGS. 9 and 10, the detected value when the input voltage is dropped in 10% steps from the rated value at 0.120 sec is shown as Vout. Signal switching selection circuit 10
If there is not, the response is delayed by the adaptive band pass filter 5 and the detection becomes slow as shown in FIG.

On the other hand, by adding the signal switching selection circuit 10 to select the output signal of the analog / digital converter 1 and use it for signal detection, as shown in FIG. And can respond quickly.

[0053]

As described above, according to the present invention,
Since the fundamental wave component is extracted by the adaptive bandpass filter before the signal detection is performed on the input signal to be detected, highly accurate signal detection can be performed.

Further, according to the present invention, by using the signal switching selection circuit, it is possible to prevent sudden changes in the input signal.
Since the analog / digital converted input signal is directly used for signal detection instead of the value obtained through the adaptive bandpass filter, high-speed signal detection can be performed.

Further, according to the present invention, when the system fault is detected, the central frequency of the adaptive bandpass filter is locked, so that the signal can be detected with high accuracy even when the system fault occurs. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a signal detection device according to the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment of the signal detection device according to the present invention.

FIG. 3 is a block diagram showing the configuration of another embodiment of the signal detection device according to the present invention.

FIG. 4 is a block diagram showing a configuration of a main part of still another embodiment of the signal detection device according to the present invention.

FIG. 5 is a block diagram showing the configuration of an embodiment of a system fault detection apparatus.

FIG. 6 is a block diagram showing a configuration of an embodiment of an armature reaction detection device.

FIG. 7 is a characteristic diagram showing an example of frequency response characteristics of the adaptive bandpass filter shown in FIG.

FIG. 8 is a diagram showing a comparison between a detection result when frequency detection is performed using an adaptive bandpass filter and a detection result when frequency detection is performed without using an adaptive bandpass filter.

9 is a characteristic diagram showing a voltage detection characteristic of the signal detection device according to the embodiment shown in FIG. 1 when an input signal suddenly changes.

10 is a characteristic diagram showing a voltage detection characteristic of the signal detection device according to the embodiment shown in FIG. 4 when an input signal suddenly changes.

[Explanation of symbols]

 1 Analog / Digital Converter 2 Maximum Spectrum Detector 3 Spectrum Detector 4 Maximum Spectrum Frequency Selector 5 Adaptive Bandpass Filter 6 AC Signal Detector 7 Primary Delay Filter 8 Frequency Detector 9 Three-Phase AC Instantaneous Value Signal Detector 10 Signal switching selection circuit 11 Comparator 12 Effective value detection circuit 13 Incomplete differentiation circuit 14 Comparator 15 AND gate 16 Low pass filter 17 Comparator 18 Band pass filter 19 Effective value detection circuit 20 Low pass filter 21 Comparator 22 AND gate

Claims (6)

[Claims] 1. A frequency detecting means for detecting an approximate value of a fundamental frequency of an alternating current signal, an analog / digital converting means for performing an analog / digital conversion on the alternating current signal, and a fundamental frequency A bandpass filter having an approximate value as a center frequency and an output signal of the analog / digital conversion means as an input signal; and signal detection means for detecting an alternating current signal based on the signal extracted by the bandpass filter A signal detection device characterized by: 2. The frequency detecting means is the analog /
The output signal of the digital converting means, the spectrum detecting means for performing frequency spectrum analysis, and the maximum spectrum frequency selecting means for selecting the frequency at which the spectrum becomes maximum based on the frequency spectrum analysis result of the spectrum detecting means, The signal detection device according to claim 1, wherein the bandpass filter is an adaptive bandpass filter. 3. A first-order lag filter for removing a ripple component included in a detection output of the frequency detecting means is provided between the frequency detecting means and the adaptive bandpass filter. The signal detection device described. 4. A system fault detecting means for detecting a power system fault and a detection output of the system fault detecting means, and based on the detected output, locks the detection output of the frequency detecting means for a certain time after the occurrence of the system fault. The signal detection apparatus according to claim 2, further comprising a control unit that holds the detection value before the occurrence of the system fault. 5. A frequency detecting means for detecting an approximate value of a fundamental frequency of a three-phase alternating current signal, a plurality of analog / digital converting means for analog / digital converting the three-phase alternating current signal for each phase, and the frequency detecting means. Based on the detection output of the means, the approximate value of the fundamental frequency is set as the center frequency, and a plurality of adaptive bandpass filters having the output signals of the respective analog / digital converting means as input signals, and extracted by the plurality of adaptive bandpass filters And a signal detecting means for detecting a three-phase AC instantaneous value signal based on the signal. 6. When the output signal of the adaptive band pass filter and the digital value of the AC signal to be detected, which is the output signal of the analog / digital conversion means, are compared, and there is a deviation of a predetermined value or more. Has signal switching selection means for selecting a signal to directly use the output signal of the analog / digital conversion means instead of the output signal of the adaptive bandpass filter without passing through the adaptive bandpass filter. The signal detection device according to any one of claims 2 to 5, which is characterized.