JPH06245600A - Frequency detecting device - Google Patents

Abstract

PURPOSE:To detect a frequency high accurately at a high speed by a rough sampling period similar to the control period of a controller. CONSTITUTION:From each phase voltage (ea, eb, ec) and current (ia, ib, ic) of a synchronous machine, a signal (ea'', eb'', ec'') in proportion to a number of interlinkage magnetic fluxes is detected, and by a value of the signal as an input, a sum of products of a value at time (t) and a signal before 1 sampling period, obtained through delay circuits 11, to 13, is detected by multipliers 14 to 22 and adders 23 to 25, to detect a frequency (f) from these values. Thus in no relation to operation and external conditions of the synchronous machine, a frequency can be realized by a rough sampling period high accurately at a high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a frequency with high accuracy and high speed in a synchronous machine excitation device without being affected by waveform distortion, load change and the like.

[0002]

2. Description of the Related Art Conventionally, in order to detect the frequency of a synchronous excitation device, the frequency is detected by measuring the time during which the voltage waveform exists on the plus side or the minus side by using a high frequency pulse using the synchronous machine terminal voltage waveform. Was there. This method has a problem that the error due to the voltage waveform distortion (particularly the point near the zero cross point) is large. For this reason, a thyristor load or SVA (Static Voltage Adju
If there is a load such as ster) that causes waveform distortion,
The correct frequency could not be detected with high speed and high accuracy due to waveform distortion.

A method of detecting the frequency by providing an electromagnetic pickup device on the turbine side is also used. However, since this method spreads the influence of shaft twist of the turbine, this signal is used as a power system stabilization signal. Then, there was a problem that the shaft torsional excitation of the turbine shaft was promoted.

As a method of improving the waveform distortion of the synchronous machine terminal voltage waveform described above, there is a method of using a multistage filter. However, since there is a time delay due to the filter, a power system stabilizer (PSS) or the like which requires high speed is used. Could not be used for the input signal of.

Further, in the conventional frequency detection method, it is necessary to apply a high frequency pulse in order to detect the frequency with high accuracy, and to count the number of pulses whose voltage waveform is on the plus side or the minus side to detect the frequency. Since it was impossible to detect the frequency with sufficient accuracy even by using a high-speed controller, it was necessary to provide a dedicated signal processing processor such as a DSP (Digital Signal Processor).

[0006]

In the above-mentioned conventional frequency detection method, the influence of the voltage waveform distortion of the synchronous machine terminal voltage is not considered at all, and a large thyristor load or SVC (Static Voltage Controller) is present nearby. If there is a waveform distortion due to this, an accurate frequency could not be detected at high speed.

The present invention has been made in view of the above circumstances, and as a signal source for detecting a frequency, a direct-axis transient transient reactance x proportional to the number of internal magnetic fluxes of a synchronous machine.
The purpose is to detect the back voltage E ″ of d ″, and to detect an accurate frequency at high speed by using this sine wave voltage waveform E ″.

[0008]

The frequency detecting device of the present invention comprises back voltage detecting means for detecting the back voltage E "of the direct-axis transient transient xd" of the synchronous machine for each of the three phases, and the back voltage detecting means. Frequency detecting means for detecting the frequency of the synchronous machine exciting device based on the back voltage detected by the voltage detecting means.

Further, in the frequency detecting apparatus of the present invention, the frequency detecting means delays the output of each of the three phases of the back voltage detecting means by one sampling period (H), and the back voltage detecting means. The present invention is characterized by further comprising arithmetic means for obtaining an inner product or an inner product and an outer product of the detection output of each phase of the detection means and the output of the signal delay means, and calculating the frequency based on the operation result of these.

Further, in the frequency detecting device of the present invention, the frequency detecting means includes signal delay means for delaying the output of each of the three phases of the back voltage detecting means by one sampling period,
The inner product of the detection output of each phase of the back voltage detecting means and the output of the signal delay means, or the inner product and the outer product are obtained, and the amount proportional to cos ωH, sin ωH, tan ωH is obtained based on these calculation results, And a calculating means for calculating the frequency from each trigonometric function value of.

Further, in the frequency detecting device of the present invention, the frequency detecting means comprises π / 2 phase shifting means for shifting the phase of the output of each of the three phases of the back voltage detecting means by π / 2.
The output of each phase of the π / 2 phase shift means is set to one sampling period,
It is characterized by including a signal delay means for delaying, and a computing means for calculating a frequency based on the output of each phase of the back voltage detecting means, the output of the π / 2 phase shifting means and the output of the signal delaying means.

Further, the frequency detecting device of the present invention includes a reference frequency generating means for generating a reference sine wave signal, a back voltage obtained by the back voltage detecting means by taking in the outputs of the back voltage detecting means and the reference frequency generating means. And a sine wave signal detecting means for outputting a sine wave signal having a frequency deviation of the reference sine wave signal.

Further, the frequency detecting device of the present invention has an amplitude value calculating means for obtaining an amplitude value of a single-phase sine wave signal which is an original signal, and an amplitude value constant by dividing the original signal by the output of the amplitude value calculating means. And a calculating means for calculating the frequency based on the output signal of the divider.

The frequency detecting device of the present invention further includes a backside voltage detecting means for detecting the backside voltage E "of the direct-axis transient transient reactance xd" of the synchronous machine for each of the three phases, and the backside voltage detecting means. 7. The frequency detecting means according to claim 6, which is provided for each phase to detect the frequency by taking in the respective background voltage of each phase, and the frequency detected by the frequency detecting means provided for each phase. An average value calculating means for calculating an average value, an absolute value of a deviation between the output of the average value calculating means and each of the frequency detecting means is obtained, and it is determined whether or not each deviation value is within a predetermined value. And an arithmetic means for making an average value of frequencies detected only in the normal phase as a detection frequency.

That is, according to the present invention, in order to achieve the above object, a direct-axis-order transient reactance xd ″ which can be always regarded as an ideal sinusoidal signal without being affected by the operating state of the synchronous machine and the external load. The background voltage E ″ is detected for each phase.

Further, in order to obtain an accurate frequency regardless of the sampling period, the time t of each phase (a, b, c phase)
−H (where H is the sampling period) and the back voltage E ″ of the direct-axis transient reactance xd ″ at t are obtained. Even if the combination of the inner product and the outer product is detected from these values and the frequency f is roughly set to the sampling period H as in the control period, high-speed frequency detection can be performed.

[0017]

The back voltage E "of the direct-axis transient reactance xd" of the synchronous machine is an amount proportional to the number of interlinkage magnetic fluxes, so that an ideal sine wave signal is always produced regardless of the operating state of the synchronous machine and the type of load. Becomes

By configuring the frequency detection device using this sine wave signal as an input signal, it is possible to perform high-speed and high-accuracy frequency detection using the detection values at the times t-H and t of the input signal.

Particularly, by taking the product sum and product difference of the three-phase sine wave signals, the amplitude value and cosω at the times t and t-H are obtained.
H, sinωH, and tanωH can be obtained quickly and accurately without including ripple values.

Further, a reference sine wave signal is generated, a signal having a frequency deviation as a sine wave signal is detected from a product difference between the reference sine wave signal and the input signal, and this signal is used as an input signal of the frequency detecting device, whereby a slight change in frequency It is possible to detect.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

First, paying attention to the fact that the number of interlinkage magnetic flux of the synchronous machine has an ideal sinusoidal waveform, the back voltage E ″ of the direct-axis-order transient reactance xd ″ proportional to this number of interlinkage magnetic flux is obtained.
FIG. 1 shows the configuration of the backside voltage detection device. In the figure, the backside voltage detection device 1 includes adders 2A, 2B, 2
C, multipliers 3A, 3B and 3C, and adders 4A and 4B,
4C and.

Phase voltage ea of synchronous machine terminal voltage and phase voltage ea
The current ib-ic having a 90 ° phase lead is detected by the adder 2A, and the product of this detected current multiplied by 1 / √3 of the synchronous machine direct axis secondary transient reactance xd ″ is calculated by the multiplier 3A. This value and the synchronous machine phase voltage ea are added to the adder 4A.
To obtain the back voltage ea ″ of the a-phase direct-axis transient reactance xd ″. The back voltage ea ″ thus detected is always an ideal sinusoidal waveform because the back voltage ea ″ is an amount proportional to the number of interlinkage magnetic fluxes, even if the ea and ia have waveform distortion.

The back voltage e is similarly applied to the b and c phases.
b ″ and ec ″ can be obtained. The backside voltages ea ″, eb ″, and ec ″ of the direct-axis transient reactance xd ″ of the synchronous machine detected in this manner have phases of 120 ° (2
It becomes an ideal sine waveform that differs by / 3 π). After that,
For the sake of simplicity, the three-phase balanced sine waveform will be represented as VAS, VBS, VCS.

Next, FIG. 2 shows the configuration of an embodiment of the frequency detecting apparatus according to the present invention.

One sampling period H detected by using the delay circuits 11 to 13 with the input voltages of the A phase, the b phase, and the c phase at time t as VAS, VBS, and VCS, respectively.
The values at the previous time t-H are VAS0, VBS0, V
Set as CS0.

VAS, VBS, VCS, VAS0, VB
Since S0 and VCS0 are ideal sample values of the sine wave signal waveform, VAS = √2A (t) sin (ωt + φ) (1a) VBS = √2A (t) sin (ωt + φ-2 / 3π) ... (1b) VCS = √2A (t) sin (ωt + φ−4 / 3π) (1c) VAS0 = √2A (t ₀ ) sin (ωt + φ−ωH) (2a) VBS0 = √2A (t) ₀ ) sin (ωt + φ−2 / 3 π−ωH) (2b) VCS0 = √2A (t ₀ ) sin (ωt + φ−4 / 3 π−ωH) (2c) where A (T) and A (t ₀ ) are amplitude values at times t and t-H, respectively.

Next, these three-phase sine wave signals are regarded as vector quantities of E ₁ = (VAS, VBS, VCS) E ₀ = (VAS0, VBS0, VCS0), and the inner product of them is obtained.

When the inner product is detected using the multipliers 14 to 22 and the adders 23 to 25, the outputs (5) to (7) are obtained.

Inner product (E ₁ , E ₁ ) = AA = VAS · VAS + VBS · VBS + VCS · VCS = 3A (t) ² (5) Inner product (E ₀ , E ₀ ) = BB = VAS0 × VAS0 + VBS0 · VBS0 + VCS0 · VCS0 = 3A (t ₀ ) ² (6) Inner product (E ₀ , E ₁ ) = CC = VAS · VAS0 + VBS · VBS0 + VCS · VCS0 = 3A (t) A (t ₀ ) cosωH …… (7) where A Since (t) and A (t ₀ ) are unknown quantities,
(5) A (t) × A (t ₀ ) is calculated from A (t) ² and A (t ₀ ) ² detected by the equations (6) by the multiplier 26 and the square root unit 27, and by this, (7 (8) is obtained by dividing the CC of the equation) by the divider 28.

CC / √ (AA · BB) = cos (ωH) (8) The value detected by equation (8) is passed through the inverse function 29 of the cosine function,
In addition, the reciprocal 30 of the pi and the sampling period H
The frequency f can be detected by multiplying by. In other words, ωH = cos ~ ¹ {CC / √ (AA · BB)}, and ω = 2πf (π: circle ratio f is the frequency [H
z]) formed by using the relationship ^{f = 1 / 2πHcos ~ 1 (} CC / √ (AA · BB)) by ... (9) it is possible to detect the frequency f.

According to this embodiment, the sampling period H may be equal to the control period of the controller, so that the frequency f can be obtained at high speed and with high precision in a coarse sampling period.

In this embodiment, the amplitude values A (t), A at each instantaneous value are utilized by utilizing the characteristics of the three-phase balanced sine wave signal.
(T ₀ ) and A (t) · A (t ₀ ) cosωH are accurately obtained as a DC value that does not include a ripple component without a time delay.
From these values, cosωH was accurately detected at high speed without delay for each sampling synchronization.

Next, the VAS, VBS, and VCS are connected to each other at 90 degrees.
An embodiment in which a three-phase balanced sine wave signal with advanced phase is detected and the frequency is detected using these signals will be described with reference to FIGS. 3 and 4.

A sine wave signal having a phase difference of 120 ° with respect to the a-phase, b-phase, and c-phase at time t is used to detect a signal having a phase difference of 90 ° from each signal using a 90-degree phase shift circuit. The configuration of the 90 ° phase shift circuit is shown in FIG. In the figure, the 90 ° phase shift circuit 40 has adders 41 and 42 and multipliers 43 to 45. For example, the three-phase sine wave signals VAS, VBS, VCS are VAS = √2 × A (t) sin (ωt + φ) (1a) VBS = √2 × A (t) sin (ωt + φ−2 / 3π) ... (1b) VCS = √2 × A (t) sin (ωt + φ−4 / 3π) (1c) VAC = (VC−VB) / √3 = √2 × A (t)
sin (ωt + π / 2 + φ) = √2 × A (t) cos (ωt + φ), and (VC−VB) / √3 has a phase of 90 ° with respect to VA.
It is an advanced signal. That is, VAC = √2 × A (t) cos (ωt + φ) (3a) VBC = √2 × A (t) cos (ωt + φ−2 / 3π) (3b) VCC = √2 × A (t) ) Cos (ωt + φ−4 / 3π) (3c), it is possible to detect signals with a 90 ° phase advance with respect to VAS, VBS, and VCS.

In each of the equations (3a), (3b), and (3c), the data before one sampling period H is VAC0 = √2 × A (t ₀ ) cos (ω (t−H) + φ) (4a ) VBC0 = √2 × A (t ₀ ) cos (ω (t−H) −φ−2 / 3π) (4b) VCC0 = √2 × A (t ₀ ) cos (ω (t−H) -Φ-4 / 3 π) (4c). Next, FIG. 4 shows the configuration of a frequency detection device that performs frequency detection using these detection values. In the figure, the frequency detection device 50 includes delay circuits 51 to 53 and a multiplier 5
4 to 62, 66, adders 63 to 65, and square root device 67
And a divider 68, an inverse function calculator 69, and a multiplier 70.

Equations (2a), (2b), (2c) and (4
The signals given by the equations a), (4b), and (4c) are regarded as a vector of E ₁ = (VAS, VBS, VCS) E ₃ = (VAC, VBC, VCC) E ₄ = (VAC0, VBC0, VCC0) And the multipliers 54 to 6 shown in FIG.
2 and the adders 63 to 65 AA = inner product (E ₃ , E ₃ ) = VAC * VAC + VBC * VBC + VCC * VCC = 3A (t) ² (5-1) BB = inner product (E ₄ , E ₄₎ ) = VAC0 * VAC0 + VBC0 * VBC0 + VCC0 * VCC0 = 3A (t 0) 2 ...... (6-1) CC = inner product _{(E 1, E 4) =} VAS * VAC0 + VBS * VBC0 + VCS * VCC0 = 3 · A (t) A It can be detected as (t ₀ ) sin (ωH) (7-1).

[0038] Here, A (t), A (t 0) is the square root device 67 through the multiplier 66 shown in FIG. 4 the product of A (t) and A (t ₀₎ for an unknown amount When the CC of the equation (7-1) is divided by the divider 68 by this detected value, CC / √ (AA · BB) = sin (ωH) (8-1) is obtained.

The value obtained by the equation (8-1) is used as the inverse function calculator 6
9 and the pi and sampling period H
F is obtained by multiplying the reciprocal of 1 by the multiplier 70.

[0040] can detect the ^{ωH = sin ~ 1 {CC /} √ (AA · BB)} f = 1 / 2πHsin ~ 1 {CC / √ (AA · BB)} ...... at (9-1) frequency f.

As a third frequency detection method, the times t and t
Amplitude values A (t), A (t ₀ ) of the sine wave vibration at −H
FIG. 5 shows an embodiment of the frequency detecting device for detecting the frequency without directly obtaining the value. In the figure, the frequency detection device 8
0 is the delay circuits 81 to 83, the multipliers 84 to 89, the adders 90 and 91, the divider 92, and the inverse function calculator 93.
And a multiplier 94.

First, the signals used in the frequency detecting device shown in FIG. 5 are shown again.

VAS = √2 · A (t) · sin (ωt + φ) …… (1a) VBS = √2 · A (t) · sin (ωt + φ−2 / 3π) …… (1b) VCS = √2・ A (t) ・ sin (ωt + φ−4 / 3π) ・ ・ ・ (1c) VAC = √2 × A (t) ・ cos (ωt + φ) ・ ・ ・ (3a) VBC = √2 × A (t) ・ cos (Ωt + φ−2 / 3π) (3b) VBC = √2 × A (t) · cos (ωt + φ−4 / 3π) (3c) VAC0 = √2 × A (t ₀ ) cos (ω) (t−H + φ) (4a) VBC0 = √2 × A (t ₀ ) cos (ω (t−H + φ−2 / 3π) (4b) VCC0 = √2 × A (t ₀ ) cos (ω) (t-H + φ-4 / 3π) ...... (4c) E 1 = (VAS, VBS, VCS) E 2 = (VAS0, VBS0, VCS0) E 3 = (VAC, VBC, VCC) E 4 = (V _{C0, VBC0, VCC0) E 1} , the inner product AA of E _4, E _3, the inner product BB of E ₄ multiplier 84
˜89 and adders 90 and 91 are used for detection.

[0044] _{AA = (E 1, E 4} ) = VAS * VAC0 + VBS * VBC0 + VCS * VCC0 = 3A (t) A (t 0) sinωH BB = (E 3, E 4) = VAC * VAC0 + VBC * VBC0 + VCC * VCC0 = 3A (T) A (t ₀ ) cosωH Unknown amplitude value A (t) A (t ₀ ) from these AA and BB
Tan ωH can be detected by dividing the value of AA by BB using the divider 92 in order to eliminate the value of.

Since AA / BB = tan (ωH) tan (ωH) was detected, the inverse function ta of tan ta
n to ¹ is calculated by the inverse function calculator 93, and 1 is added to this calculation result.
By multiplying / 2πH by the multiplier 94, f = (1 / 2πH) tan ~ ¹ (AA / BB) and the frequency f can be detected.

According to the present embodiment, it is possible to obtain the frequency with the same accuracy with a smaller calculation amount as compared with the first and second frequency detection methods.

As a fourth frequency detection method, an embodiment will be shown in which the outer product of the vectors E ₀ and E ₄ is obtained and the frequency is detected from this. Letting these components be d ₁ , d ₂ , and d ₃ , d ₁ = VAS0 · VBS-VBS0 · VBS d ₂ = VBS0 · VCS-VCS0 · VBS d ₃ = VCS0 · VAS-VAS0 · VAC is obtained. When the measured values shown in the equations (1) to (4) are applied to these to obtain d ₁ , d ₂ and d ₃ , these are all d ₁ = d ₂ = d ₃ = √3A (t) A (T ₀ ) sin (ωH).

The sum of d ₁ , d ₂ and d ₃ is taken and divided by √3. DD = (d ₁ + d ₂ + d ₃ ) / √3 = 3 A (t) · A (t ₀ ) sin (ωH) …… (12) is obtained.

Similarly to the case of the inner product, the equation (12) is divided by the square of the product of the equations (5) and (6) to obtain DD / √ (AA · BB) = sin (ωH).

Therefore, as in the case of the inner product, the frequency f can be detected as f = 1 / (2π · H) sin ~ ¹ {DD / √ (AA · BB)} (13).

Further, from equations (9) and (10), ωH <π
If the sampling period H is selected to be / 2, c
Since osωH ≠ 0, the formula (12) is divided by the formula (7) to obtain DD / CC = sin ωH / cos ωH = tan (ωH) (14) (14) Formula can be obtained, and the sum of the inner product and the outer product can be obtained. the ratio f = tan ~ frequency f using ¹ (DD / CC) can be detected with ... (15).

Next, FIG. 6 shows an embodiment of a frequency detecting device for detecting the frequency of a single-phase AC signal. In the figure, the frequency detection device 100 includes a multiplier 101, 106, a filter circuit 102, 107, a square root 103, and a divider 10.
4, a delay circuit 105, an inverse function calculator 108, and a multiplier 109.

First, the sine wave voltage signal VAS is squared using the multiplier 3.

Since the sine wave voltage signal VAS is an ideal sine wave, VAS = √2A (t) * sin (ωt + φ). Therefore, VAS · VAS = 2A (t) ² · sin ² (ωt + φ) = A (t) ² {1-cos (2ωt + 2φ)} is obtained. First, an amplitude value A (t) multiplier 101 that is an unknown quantity
Then, the squared value of VAS is calculated by the filter circuit 102, and the filter circuit 102 removes the component of 2ωt.
Amplitude value A (t) of VAS is obtained through 3. However, the amplitude value A (t) thus obtained is the filter circuit 102.
Strictly speaking, the amplitude value is slightly different from the amplitude value at the actual time t, but the time change of the normal amplitude value A (t) is a negligible amount compared to the time change of sin (ωt + φ). Therefore, it can be regarded as the amplitude value A (t) at the time t without any problem.

Next, the original signal VAS = √2 × A (t) * si
When n (ωt + φ) is divided by the value obtained through the square root unit 103 by the divider 104, it is possible to obtain a sine wave voltage signal of amplitude √2, which is VAS / A (t) = VAN = √2sin (ωt + φ).

Next, VAN = √2 · sin (ωt + φ)
And a value obtained through the delay circuit 105 VAN0 = √2 ·
When the product of sin (ω (t−H) + φ) is obtained by the multiplier 106, VAN * VAN0 = {cos (ωH) −cos (2ωt−ωH + 2φ)} is obtained. The value of VAN · VAN0 thus obtained is passed through the filter circuit 107 to cos (2ωt−ωH + 2
If the value obtained by removing φ) is AA, AA = cos (ωH)
Becomes Therefore, ω is calculated by the inverse function calculator 108 that calculates the inverse function of cos, and the inverse of 2πH is multiplied by the multiplier 109.
It is possible to detect cos (ωH) by multiplying by and obtain the frequency f from this.

F = 1 / (2πH) cos ~ ¹ (AA) When the frequency is detected through a single phase, a two-stage filtering process is required as shown in FIG. 6, but a sampling period of 1 ms is about 20 ms. Therefore, sufficient response and accuracy can be obtained for excitation control of the synchronous machine such as power system stabilization control.

As described above, the frequency f is calculated from the single-phase sine wave signal.
In the case of detecting, it is possible to perform an abnormality diagnosis of each phase signal for detecting the frequency independently for each of the three-phase power supply VAS, VBS, and VCS. In addition, by taking the average value of the normal phase, Accurate frequency detection can be performed.

Next, FIG. 7 shows the configuration of another embodiment of the frequency detecting apparatus. In the figure, a frequency detection device 200 includes frequency detection circuits 201 to 20 for detecting the frequency of each phase signal.
3, an average value calculation circuit 204 for calculating an average value of these frequency detection circuits 201 to 203, and an average value calculation circuit 20.
4 and the outputs of the frequency detection circuits 201 to 203, and adders 205 to 207 for calculating the deviation between the outputs of the frequency detection circuits 201 to 203, and the adder 20.
Comparing circuits 208 to 210 for comparing the absolute value of the deviation of 5 to 207 with a predetermined value (ε), and discriminating circuits 211 to 213.
And multipliers 214 to 216 and adders 217 and 218,
And a divider 219.

In the above structure, the phase signals VAS, VB
The frequencies of S and VCS are detected by the frequency detection circuits 201 to 2
03, and let these values be fa, fb, and fc. The average value f ₀ of these values is obtained by the average value calculation circuit 204, and the deviation Δ between this value and each frequency fa, fb, fc
fa, Δfb, Δfc are obtained by the adders 205 to 207, and when the absolute value of these deviations is equal to or less than a predetermined value ε (ε is usually a value of several%), it is regarded as normal and 1.0, the condition is not satisfied. In the case of 0.0, it is output by the comparison circuits 208 to 210 and the discrimination circuits 211 to 213.

[0061] Therefore, the frequency f of f = (fa * KA + fb * KB + fc * KC) / (KA + KB + KC) is multiplied by the multipliers 214 to 216, the adder 217,
218 and the divider 219 can be used for detection.
By doing so, the average value of the normal detection phases can always be obtained.

Using the above embodiment, the frequency f can be detected with high accuracy and high speed for both the three-phase sine wave signal input and the single-phase sine wave input signal. However, in order to detect an extremely small value of frequency change, each of the above-mentioned methods is a method of detecting an absolute value of frequency, and is not suitable.

Therefore, as a method for solving this, it is only necessary to detect a sine wave signal including these frequency deviations from the sine wave signal input and the reference sine wave signal, and apply the frequency detection method described above.

Next, FIG. 8 shows the configuration of an embodiment of a sine wave signal detection circuit for detecting a sine wave signal proportional to the frequency deviation between the sine wave signal input and the reference sine wave signal. In the figure, the sine wave signal detection circuit 300 has a multiplier 301 and a filter circuit 302.

Input signal VAS = √2A (t) (sin
ωt + φ) and the signal VBASE from the newly provided reference frequency generating circuit 303 are multiplied by the multiplier 301 to obtain VAS · VBASE = A (t) · (cos ((ω−ω ₀ ) t + φ−φ ₀ ) − A sinusoidal signal including the frequency components ω−ω ₀ and ω + ω ₀ is obtained as cos ((ω + ω ₀ ) t + φ + φ ₀ )}. Since the frequency ω ₀ of the reference sine wave signal is selected so that ω−ω ₀ << ω + ω ₀ ,
The term + ω ₀ can be easily removed by the filter circuit 302 as a first-order lag element or an integral filter.
A typical filter is (1 + Z ~ ¹ + Z ~ ² + Z ~ ³ + Z
~ ⁴ + Z ~ ⁵ ) / 6 integral filter may be used. Here, Z to i represent values at time t-i * H. (I = 1
5) In the case of a single phase, the filter is necessary as described above, but in the case of a three-phase balanced sine wave signal, this filter is unnecessary.

That is, Vsin0 = √2 · sin (ω ₀ t + φ ₀ ) Vcos0 = √2 · cos (ω ₀ t + φ) is provided as a reference signal for each phase. These values and VAS, VBS, VCS, VA
A sine wave signal having an angular frequency ω-ω ₀ and an amplitude A (t) can be obtained by obtaining the product difference between C, VBC, and VCC.

[0067] For example DsinA = VAS · Vcos0-VAC · Vsin0 = 2A (t) {sin (ωt + φ) · cos (ω 0 t + φ 0) -cos (ωt + φ) · sin (ω 0 t + φ 0)} = 2A (t) sin ((ω−ω ₀ ) t + φ−φ ₀ } Similarly, as DcosA = VAC · Vcos0 + VAS · Vsin0 = 2A (t) cos {(ω−ω ₀ ) t + φ−φ ₀ }, only the (ω−ω ₀ ) component is obtained. It is possible to instantly obtain a three-phase signal with a 90 ° phase advance with respect to the included sine wave input signal without requiring a special filter and without a time delay.

If these signals are used as the input signals of the frequency detection circuit (FIG. 7) described above, the angular frequency deviation value ω-
ω ₀ , that is, the value of the frequency deviation value Δf = f−f ₀ can be obtained very accurately.

FIG. 9 shows the overall structure of a synchronous machine excitation device to which the frequency detection device according to the present invention is applied. The automatic voltage regulator detects the terminal voltage of the generator 400 via the PT 404, compares the detected value with the value set by the setter 405, and if there is a deviation, it is detected by the amplifier 406 and the gate pulse generator. (Gate Pulse Genera
by controlling the gate of the thyristor 412 via the (tor) 407 to change the field current If in the field 414 of the generator 400 to control the terminal voltage of the generator 400 constant.

On the other hand, as a measure for improving the power system stability rate, a power system stabilizer (PSS: Power System Stem Stabilize) is used.
r) It is necessary to add 409 and the shaft twist suppression device 410, but high-speed and high-accuracy frequency detection is required as an input signal for this. The present invention provides a frequency detecting device 408 which detects a frequency signal, which is an essential signal for system stabilization, at high speed without being affected by waveform distortion.

As described above, in this embodiment, by detecting the voltage E ″ proportional to the number of flux linkages from the terminal voltage and terminal current of the synchronous machine, there is waveform distortion in the voltage and current of the synchronous machine. Has always made it possible to detect a voltage signal having a basic sine wave.

Further, the frequency detection using this detection signal is carried out at the same rough control sampling with the same control cycle by the combination of the inner product and the outer product using the simple product sum / product difference operation of the time t and the value of tH before the sampling. High-speed and highly-accurate frequency detection is possible even in the synchronization H.

Further, as a method for detecting a minute change in frequency, a sine wave signal having only a difference frequency component can be detected by providing a reference frequency generating circuit and taking a product difference between the original signal and the reference signal. This makes it possible to perform frequency fluctuations at high speed and with high accuracy.

[0074]

As described above, according to the present invention, the back voltage E "of the direct axial transient reactance xd" proportional to the number of flux linkages is calculated from the terminal voltage and terminal current of the synchronous machine as a signal for frequency detection. Since it is used as a power source, frequency detection can be performed at high speed and with high accuracy even in a rough sampling cycle regardless of the operating state and external state of the synchronous machine.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a backside voltage detection device that detects a backside voltage of a direct-axis transient reactance xd ″ of a synchronous machine.

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

FIG. 3 is a block diagram showing a configuration of a 90 ° phase shift circuit used for frequency detection.

FIG. 4 is a block diagram showing the configuration of another embodiment of the frequency detection device according to the present invention.

FIG. 5 is a diagram showing the configuration of another embodiment of the frequency detection device according to the present invention.

FIG. 6 is a block diagram showing the configuration of another embodiment of the frequency detection device according to the present invention.

FIG. 7 is a block diagram showing the configuration of another embodiment of the frequency detection circuit according to the present invention.

FIG. 8 is a block diagram showing a configuration of a sine wave signal detection circuit that detects a sine wave signal including a frequency deviation ω−ω ₀ .

FIG. 9 is a block diagram showing a configuration of a synchronous machine excitation device to which the frequency detection device according to the present invention is applied.

[Explanation of symbols]

 1 Back Voltage Detection Device 10 Frequency Detection Device 40 90 ° Phase Shift Circuit 50 Frequency Detection Device 80 Frequency Detection Device 100 Frequency Detection Device 200 Frequency Detection Device 201 Frequency Detection Circuit 202 Frequency Detection Circuit 203 Frequency Detection Circuit 204 Average Value Calculation Circuit 205 Addition Unit 206 Adder 207 Adder 208 Comparison circuit 209 Comparison circuit 210 Comparison circuit 211 Discrimination circuit 212 Discrimination circuit 213 Discrimination circuit 214 Multiplier 215 Multiplier 216 Multiplier 217 Adder 218 Adder 219 Divider 300 Sine wave detection circuit 301 Multiplication Unit 302 Filter circuit 303 Reference frequency generation circuit

Claims (7)

[Claims] 1. A direct-axis transient reactance xd ″ of a synchronous machine.
Has a backside voltage detecting means for detecting the backside voltage E ″ of each of the three phases and a frequency detecting means for detecting the frequency of the synchronous machine excitation device based on the backside voltage detected by the backside voltage detecting means. A frequency detection device characterized by the above. 2. The frequency detecting means, a signal delay means for delaying the output of each of the three phases of the back voltage detecting means by one sampling period (H), and a detection of each phase of the back voltage detecting means. The frequency detecting apparatus according to claim 1, further comprising: an arithmetic means for obtaining an inner product or an inner product and an outer product of the output and the output of the signal delay means, and calculating a frequency based on a result of the arithmetic operation. 3. The frequency detecting means, a signal delay means for delaying the output of each of the three phases of the back voltage detecting means by one sampling cycle, a detection output of each phase of the back voltage detecting means and the signal. An inner product with the output of the delay means, or an inner product and an outer product are obtained, and an amount proportional to cos ωH, sin ωH, tan ωH is obtained based on these calculation results, and calculation means for calculating the frequency from each trigonometric function value The frequency detection device according to claim 1, further comprising: 4. The frequency detection means shifts the phase of the output of each of the three phases of the back voltage detection means by π / 2, and each of the π / 2 phase shift means. The phase output is 1 sampling cycle,
It has a signal delaying means for delaying, and a computing means for calculating a frequency based on the output of each phase of the back voltage detecting means, the output of the π / 2 phase shifting means and the output of the signal delaying means. Item 1. The frequency detection device according to item 1. 5. A reference frequency generating means for generating a reference sine wave signal, a back voltage obtained by the back voltage detecting means and a reference frequency generating means, and a frequency of the reference sine wave signal obtained by the back voltage detecting means. 5. A frequency detecting device according to claim 1, further comprising a sine wave signal detecting means for outputting a sine wave signal having a deviation. 6. An amplitude value calculating means for obtaining an amplitude value of a single-phase sine wave signal which is an original signal, and a division for obtaining the sine wave signal having a constant amplitude value by dividing the original signal by the output of the amplitude value calculating means. And a calculating means for calculating a frequency based on an output signal of the divider. 7. A direct-axis transient transient reactance xd ″ of a synchronous machine.
Is provided for each phase for detecting the frequency by detecting the back voltage E ″ of each of the three phases and the back voltage of each phase detected by the back voltage detecting means. The frequency detecting means according to claim 6, an average value calculating means for calculating an average value of the frequencies detected by the frequency detecting means provided for each of these phases, an arithmetic output of the average value calculating means and each of the above. An absolute value of the deviation from the frequency detection means is obtained, and an abnormality judgment is made depending on whether each of these deviation values is within a predetermined value or not, and an arithmetic means that uses the average value of the frequencies detected only in the normal phase as the detection frequency. And a frequency detecting device.