JP3507838B2 - Power fundamental wave phase detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a fluctuation in the phase of current or voltage of a power fundamental wave at high speed by using a Fourier transform method.

[0002]

Conventionally, low-speed power control using a protection relay has been widely used in the fields of power plant control devices, substation control / measurement devices, etc. Or, the detection response for the fluctuation of the voltage phase was rarely required to the limit. Further, conventionally, in order to extract a fundamental wave, a method of detecting a phase variation using an asynchronous integration type analog or digital filter circuit and a low-speed sampling circuit with a fixed sampling interval has been mainstream. Therefore, there is a time delay of several cycles of the fundamental wave in the response to the phase fluctuation,
Also, the calculation cycle is usually about once per AC cycle, depending on the processing capacity of the CPU. However, in recent years,
There is a growing demand for real-time control that applies modern control theory in order to quickly recover and stabilize power systems after an accident occurs, and in the event of an accident, the situation is dynamically measured to enable real-time and highly accurate control. It has come to be demanded. Therefore, an object of the present invention is to detect a fluctuation in the phase of the current or voltage of the power fundamental wave at high speed.

[0003]

In order to solve the So the problems SUMMARY OF THE INVENTION The invention of Claim 1 includes a trigger generating that occur to trigger a wavelength interval of the power fundamental wave of current or voltage at a timing of N equal parts Means and the electric power input to the A / D converter.
Force fundamental wave current or voltage value at the trigger timing
The means for sampling and the phase n (n
Is an integer (1 to N) corresponding to sin (2nπ /
N) and cos (2nπ / N) values in the order
Stored ring type sin term constant table and cos term
Constant table and sample obtained for each sampling
Sin (2nπ / N) corresponding to the phase n of the ringing value and
Read the value of cos (2nπ / N) from both constant tables
Multiplying means that takes in and multiplies with each sampling value
And N data addresses, and the multiplying means
The product obtained by
Parameter file and both constant tables and
And advance the reading position of both ring files by one address
.Pointer to circulate and obtained by the multiplying means
Each product is added in turn and each ring file
The value written one wavelength before is read and subtracted
By doing so, the integrated value of each immediately preceding 1 wavelength section is calculated.
Those with the means, and means for outputting a value obtained by multiplying the 2 / N for both the integral value as a coefficient B of the coefficient A and cos terms of sin term power fundamental wave of current or voltage, the to
Is. It is possible to monitor the fluctuation of the phase from the ratio of these two coefficients.

[0004]

The invention according to claim 2 is the electric power source according to claim 1.
In the present wave phase detection device , from the outputted coefficient A of the sin term and coefficient B of the cos term, arctan (A / B)
To obtain the phase angle of the power fundamental wave by
Of the generated phase angle is detected and the trigger of the trigger generation means is triggered.
A PLL calculator that keeps the timing of occurrences in line with phase fluctuations
Ru der those with a stage, a.

ClaimsThreeThe invention of claim 1Described power base
Main phase detectorThe power output from the generator at
While inputting the fundamental wave to the A / D converter,
The signal of the encoder connected to the data
Find phase angleMeans and detect the variation of the obtained phase angle
The trigger generation timing of the trigger generation means.
And a PLL calculation unit that follows the movement.
It

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention. Since the present invention is mainly realized by software using a Fourier transform method, each process is shown as a concrete block. is there. In the figure,
Reference numeral 1 denotes an A / D converter, which is supplied with a current or voltage consisting of a sine wave of 50 Hz or 60 Hz as a power fundamental wave and is sampled at a trigger input timing.

This trigger is output from the programmable timer 19, which is a trigger generating means, at an interval ts obtained by dividing one wavelength of the fundamental wave into N equal parts, and at a timing that always follows the phase of the fundamental wave. The values sampled by the A / D converter 1 are input to the multipliers 2 and 3. In the multipliers 2 and 3, the sampling value corresponds to the phase s
The values of in (2nπ / N) and cos (2nπ / N) are si
The n-term constant table 4 and the cos-term constant table 5 are read and multiplied.

The product obtained by the multiplier 2 is written to the address corresponding to the phase n of the ring file 6 and is input to the addition point 8. At the same time, the integrated value up to the previous time is input to the addition point 8 via the delay element 13. Further, the value read from the immediately preceding address of the ring file 6 at the time of the previous sampling and held in the delay element 11 is input to the addition point 8 and subtracted. That is,
Here, the N sampling values are always integrated, and the latest sin wave component for one wavelength is integrated. The obtained integral value of the sin wave component is sent to the multiplier 15 and multiplied by 2 / N to obtain the coefficient A of the sin term. The coefficient A is the imaginary of the fundamental wave vector.
The phase calculation unit 17 outputs the output to the outside.
Sent to.

The product obtained by the multiplier 3 is written to the address corresponding to the phase n of the ring file 7 and is input to the addition point 9. At the same time, the integrated value up to the previous time is input to the addition point 9 via the delay element 14. Further, the value read from the immediately preceding address of the ring file 7 at the time of the previous sampling and held in the delay element 12 is input to the addition point 9 and subtracted. That is,
Here, the N sampling values are always integrated, and the latest cosine wave component for one wavelength is integrated. The obtained integrated value of the cos wave component is sent to the multiplier 16 and is multiplied by 2 / N to obtain the coefficient B of the cos term. The coefficient B is externally output as a Real output of the fundamental wave vector and is also sent to the phase calculation unit 17.

The phase calculator 17 calculates the coefficients A and c of the sin term.
The ratio of the coefficient B of the os term is calculated, and the arctan (A
/ B) to obtain the PLL as phase data of the power fundamental wave.
It is sent to the calculation unit 18. The PLL calculation unit 18 performs the phase control calculation by the PLL calculation so that the reference phase is always zero (the position where the reference matches the AC zero-cross point), and sends the calculation result to the programmable timer 19. The programmable timer 19 generates a trigger at intervals ts based on the calculation result and sends it to the A / D converter 1 and the pointer counter 21.

The pointer counter 21 is incremented by a trigger to rotate the sin term constant table 4, the cos term constant table 5, and the ring files 6 and 7 clockwise by one pitch. Thereby, in synchronization with the input AC fundamental wave, a value corresponding to the sampling phase is read from the file and the table, and a series of processes is repeated to continuously calculate the fundamental wave phase data.

FIG. 2 is a block diagram showing a second embodiment of the present invention. Since this embodiment has some parts in common with the first embodiment shown in FIG. 1, the common parts are designated by the same reference numerals. Will be omitted, and different parts will be described. This embodiment is installed in a power plant and directly detects the rotation of the rotor of the generator to detect the phase of the fundamental wave. That is, in FIG. 2, the preset encoder 23 and the speed encoder 24 are directly connected to the rotor 22 of the generator, and the preset encoder 23 and the speed encoder 24 are input to the take-out counter 27 as detection signals of the pickups (position sensors) 25 and 26.

The counter 27 sends a rotation phase signal obtained by dividing one rotation of the rotor 22 into a plurality of times to the phase comparison unit 28. The phase comparison unit 28 compares the rotation phase signal of the counter 27 with the increment timing of the pointer counter 21, and sends the result to the PLL calculation unit 18. Thereby,
Here, the sampling timing is determined based on the rotating magnetic field of the generator, for example, the phase of the N pole.

With this configuration, the following effects can be obtained in both of the above-described embodiments. (1) The response time can be shortened. Specifically, compared to the conventional method, the average response time is about half of one AC cycle. (2) The fundamental wave electricity quantity can be continuously calculated in a cycle shorter than one AC cycle. The highest is A /
It is also possible to continuously calculate the calculation result for each D sampling (1 / N cycle).

In addition, the following synergistic effects are obtained. (3) The load on the CPU is reduced. Specifically, compared to a general Fourier calculation method such as oversampling FFT, if the accuracy is the same, a calculation amount of a fraction is sufficient. (4) By adopting the variable sampling method, the frequency follow-up characteristic is improved, and the accuracy is not deteriorated compared to the conventional method even with wide voltage frequency fluctuations such as generator voltage.

[0017]

As described above, according to the invention of claim 1, every time the power fundamental wave is sampled, a discrete Fourier series expansion is performed on the fundamental wave in the immediately preceding one-wavelength section to obtain si.
By obtaining the coefficient A of the n term and the coefficient B of the cos term,
It is possible to detect the fluctuation of the phase of the power fundamental wave in real time.

[0018]Also, Ring type sin for integral operation
Equipped with term constant table and cos term constant table
Then, the multiplication of the sampled value with the sin and cos terms is easy.
Be simple.further, The multiplication result in a ring file
Write it down and add the multiplication result this time to the previous integration value.
And the multiplication result one wavelength before from the ring file
By reading and subtracting that value from the integrated value this time
Simpler integration calculation and fasterCan be
It

According to the invention of claim 2 , the obtained sin
From the coefficient A of the term and the coefficient B of the cos term, arctan (A /
By calculating B), the phase angle of the power fundamental wave is obtained, and the fluctuation of the phase angle is detected, so that the trigger generation timing can be made to follow the phase fluctuation for each sampling.

According to the third aspect of the invention, the phase angle of the power fundamental wave is obtained from the signal of the encoder connected to the rotor of the generator, and the variation of the phase angle is detected to determine the trigger generation timing. It is possible to follow changes. In this case, more responsive follow-up becomes possible.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols] 1 A / D converter 4 sin term constant table 5 cos term constant table 6,7 ring file 11-14 Delay element 15,16 Multiplier 17 Phase calculator 18 PLL arithmetic unit 19 programmable timer 21 Pointer counter 22 rotor 23 Preset encoder 24 speed encoder 25,26 Pickup (position sensor) 27 counter 28 Phase comparator

Continuation of the front page (56) Reference JP-A-5-164793 (JP, A) JP-A-59-114674 (JP, A) JP-A-8-220155 (JP, A) JP-A-3-216562 (JP , A) JP-A-63-101767 (JP, A) JP-A-55-129761 (JP, A) Jitsukaihei 5-77785 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G01R 23/16 G01R 25/00 G06F 17/14

Claims (3)

(57) [Claims] 1. A trigger generating means for generating a trigger at the timing of equally dividing one wavelength section of the current or voltage of the power fundamental wave into N equal parts, and the value of the current or voltage of the power fundamental wave input to the A / D converter. To sample at the timing of the trigger and the phase n of the sampling value (n is an integer from 1 to N)
Corresponding sin (2nπ / N) and cos (2nπ / N
N type) ring type sin terms that store the values of
The number table and the cos term constant table, and the phase n of the sampling value obtained for each sampling
Corresponding sin (2nπ / N) and cos (2nπ / N
The value of N) is read from both constant tables, and
And a sampling means for multiplying the sampling value, and N data addresses are both provided.
A pair of rings in which the obtained products are written in order.
File and both constant table and both ring file based on trigger
Poi that advances / circulates the read position of the file by 1 address
And the products obtained by the multiplying means are sequentially added.
Write with each ring file one wavelength before
By reading out the subtracted value and subtracting it,
Means for calculating the integral value in the previous one wavelength section, and the values obtained by multiplying both integral values by 2 / N are output as the coefficient A of the sin term and the coefficient B of the cos term of the current or voltage of the power fundamental wave. An electric power fundamental wave phase detection device comprising: 2. The power fundamental wave phase detector according to claim 1, wherein the output is a coefficient A of the sin term and a coefficient B of the cos term output.
, Arctan (A / B) to calculate the phase of the power fundamental wave
The means for obtaining the angle and the variation of the obtained phase angle are detected and the trigger generator means
PLL performance that allows the timing of riga to follow the fluctuation of the phase
An electric power fundamental wave phase detection device comprising: an arithmetic unit. 3. A power fundamental wave phase detecting apparatus according to claim 1 Symbol placement, the power fundamental wave output from the generator to the A / D converter input
And an encoder connected to the rotor of the generator
Means for obtaining the phase angle of the power fundamental wave from the signal , and PLL calculating means for detecting the obtained phase angle variation and causing the trigger generation timing of the trigger generating means to follow the phase variation. Power fundamental wave phase detector.