JPH10271685A - Synchronous machine generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the high speed and high precision real-time detection of the fluctuating frequency and attenuation constant of a power system and improve the dynamic stability. SOLUTION: The active power change component ΔP of a synchronous machine is separated into a generator frequency change component Δf and its integration (∫ Δfdt) that are proportional to proportional constants K1 and K2. A means 10 which identifies the proportional constants is provided. The compensation output of a power system stabilizing means 12 is automatically adjusted in accordance with the identified proportional constants to stabilize power fluctuations. The proportional constants K1 and K2 are determined in such a manner that the square the deviation between the active power change component ΔPi and K1*Δfi+K2*∫Δfidt (error J) is obtained by least squares method and the proportional constants K1 and K2 which minimize the error J are determined from δJ/δK1=-and δJ/δK2=0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exciting device for a synchronous machine, and more particularly to a technique for improving the stability of a power system.

[0002]

2. Description of the Related Art A conventional exciting device for a synchronous machine has been disclosed in JP-A-61-280715 and JP-A-55-74400 for the purpose of improving power system stability. And stabilization using the generator frequency and the like as input signals. However, in the conventional method, only a design optimized for a fixed power fluctuation frequency can be performed. Therefore, when the system configuration and the power flow condition change significantly, sufficient stability cannot be secured.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a real-time high-speed oscillation frequency and attenuation constant of a power system.
An object of the present invention is to provide an exciting device for a synchronous machine that enables high-accuracy detection and is suitable for improving dynamic stability.

[0004]

Means for Solving the Problems To solve the above problems, means for calculating a deviation between a voltage of a synchronous machine and a set value, and a compensation output are calculated based on a change in active power and a change in frequency of the synchronous machine. An exciter for a synchronous machine having power system stabilization means for supplying an exciting current to the synchronous machine in accordance with an output obtained by adding a compensation output to the deviation, wherein the active power change (ΔP) is calculated by the frequency change A means for separating a component proportional to (Δf) and its integral (∫Δfdt) or a component proportional to the internal phase difference angle (Δδ), and a means for identifying the proportional constant, and a means for identifying the proportional constant. To automatically adjust the compensation output. Here, the proportional constant (K
1, K2), the active power change (Δ
Pi) and the square of the deviation between K1 * Δfi + K2 * ∫Δfidt (error J) is obtained by the least squares method, and ∂J / ∂K1 =
From 0, ∂J / ∂K2 = 0, the proportional constants (K1, K2) that minimize the error (J) are obtained. Here, the proportional constant (K
1, K2) determines the variables K1w, K2w, and Dw from the change in the active power (ΔPi), the change in the generator frequency (Δfi), and the internal phase difference angle (Δδi),
The proportional constants (K1, K2) are obtained by calculating K1 = K1w / Dw and K2 = K2w / Dw. When the absolute values of the active power change (ΔP) and the frequency change (Δf) are small, the active power change (ΔP) and the frequency change (Δf)
The proportional constants (K1, K2) are updated only when is greater than or equal to a certain value.

In order to improve the dynamic stability of the synchronous machine, it is necessary to know the operating state of the synchronous machine including the power system. The change ΔP of the synchronous machine active power is directly related to the dynamic stability. In order to improve the stability, the fluctuation frequency and damping constant of ΔP during operation and the phase relation between each physical quantity are real-time. You need to know. Therefore, the present invention provides a method of changing the active power ΔP
The power stabilizing means (PSS) is divided into proportional components K1 and K2, which are components proportional to the variation Δf of the generator frequency and its integral ∫Δfdt, and based on the detected values of K1 and K2.
Is automatically adjusted to improve the stability of the synchronous machine. As a first means for detecting K1 and K2,
First, the active power Pi and the generator frequency fi are differentiated, and the active power change ΔPi, the generator frequency change Δfi,
Further, the integral ∫Δfdt is obtained (here, the subscript i indicates the value at the sampling time i). Next, ΔP
The square J of the deviation between i and K1 * Δfi + K2 * ∫Δfidt is obtained by the least square method, and ∂J / ∂K1 = 0, ∂J / ∂K
From 2 = 0, K1 and K2 that minimize the error J are obtained. K
1. As a second means for detecting K2, first, the obtained active power change ΔPi and the generator frequency change Δf
i, coefficients A11, A12, A2 from internal phase difference angle Δδi
1, A22, B1, and B2 are obtained, and intermediate outputs Dw, K1w, and K2w are obtained from these coefficients. Next, K1
= K1w / Dw, K2 = K2w / Dw
1. Detect K2. As described above, ΔPi is set to ΔPi ≒ K
1Δfi + K2∫Δfidt or ΔPi ≒ K1Δ
fi + K2Δδi, the state of ΔPi is identified, from which the power fluctuation frequency of the synchronous machine, the attenuation time constant, the phase difference between the control signals, etc., required for the adaptive control of the power system stabilizing means (PSS). Information can be identified in real time.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an excitation device for a synchronous machine according to an embodiment of the present invention. In FIG. 1, 1 is a synchronous machine, 2
Is an instrument transformer (PT), 3 is an instrument current transformer (CT),
4 is a signal detection circuit, 5 is an AVR voltage set value, 6 is a subtraction circuit, 7 is an addition circuit, and 8 is a gate pulse generator (GP
G), 9 is an integrating circuit, 10 is a K1, K2 detecting circuit, 11
Is the K1 set value, and 12 is the power system stabilizer (PSS
(P)), 13 is a transformer for excitation (EXTR), 14 is a thyristor circuit (THY), and 15 is a field breaker (FCB)
Represents In this embodiment, the terminal voltage of the generator 1 is applied to the signal transformer 4 via the instrument transformer 2 and the armature current via the instrument transformer 3. The signal detector 4 outputs a generator voltage Vg, an active power change ΔP, and a frequency change Δf required for the excitation control. The Vg and the AVR voltage set value V
The deviation of kg is obtained, and this deviation is output to the adding circuit 7.
Further, the integrator 9 outputs a time integration value ΔΔfdt of Δf. Next, ΔP, Δf, ∫Δ are applied to the K1 and K2 detection circuits.
fdt, and K1 and K2 detection circuits convert ΔP to Δf
And proportional coefficients K1 and K2 when linearly approximated by ∫Δfdt. K1 is compared with a K1 set value K1ref11, and the power system stabilizing device (P
SS) The parameter P of 12 is controlled. The same applies to the proportional coefficient K2. The compensation output of the power system stabilizer (PSS) 12 obtained based on the parameter P is output to the addition circuit 7. The compensation output of the power system stabilizing device (PSS) 12 is added to the difference between Vg and Vkg, and a gate pulse is generated by the gate pulse generating device 8, and the thyristor circuit 1
Turn 4 on and off. ON of this thyristor circuit 14,
When turned off, an exciting current is supplied from the exciting transformer 13 to the field winding of the generator 1 via the field breaker 15. As described above, in the present embodiment, the components that are proportional to ΔP and Δf and ∫Δfdt, that is, the proportional coefficients K1 and K2 are obtained, compared with the set values, and the power stabilizing device (PSS) 12 The stability of the synchronous machine is improved by automatically adjusting the parameter (P).

FIG. 2 shows details of the K1 and K2 detection circuits. The active power Pi and the generator frequency fi are detected by using the generator voltage and the armature current detected by PT2 and CT3, and these signals are further differentiated by the imperfect differentiating circuit 16 with respect to the temporal changes ΔPi and Δfi. Ask for. Next, the integrator 9 detects a time integration value ∫Δfidt of Δfi. Using these signals, the J detection circuit 17 calculates ΔP
An error J when i is linearly approximated by Δfi and ∫Δfidt is obtained by the least square method of the equation (1).

J = Σ (ΔPi−K1 * Δfi−K2 * ∫Δfidt) ² (1) Subsequently, the J minimizing circuit 18 calculates ∂J / ∂K1 = 0,
From ∂J / ∂K2 = 0, K1 and K2 that minimize the error J are obtained. The subscripts of ΔPi and Δfi indicate values at the time i sampling. Specific calculation method (2)
To (7).

(Equation 2)

(Equation 3) A condition for minimizing J is obtained.

(Equation 4)

(Equation 5) Considering K1 and K2 as variables,

(Equation 6) here,

(Equation 7) far.

FIG. 3 shows details of the K1 and K2 detection circuits shown in FIG. FIG. 3 shows ΔPi, Δfi, ∫Δfidt
, A low-pass filter 21 having the same frequency characteristic is added to the detection signal to remove the influence of waveform distortion such as detection circuit noise and system disturbance, and then input to the J detection circuit. In the K1 and K2 detection circuits in FIG. 3, signals such as ΔPi and Δfi are delayed because the low-pass filter 21 is added. However, since the low-pass filters 21 have the same frequency characteristics, ΔPi, Δfi, and ∫Δf
The relation between idts is maintained at a constant ratio, and the proportional coefficients K1 and K2 for minimizing J are not much affected by the low-pass filter 21. Therefore, by adding the low-pass filter 21, it is possible to eliminate the influence of noise and waveform distortion without delaying the signal detection of K1 and K2. Note that the internal phase difference angle Δδi may be used instead of ∫Δfidt.

FIG. 4 shows a K1 and K2 detection circuit having a response substantially equal to that of the K1 and K2 detection circuits shown in FIG. 3 and being more resistant to the effects of noise and waveform distortion. 4 includes coefficients A11, A12, A21, A having an arithmetic circuit 20 and a low-pass filter circuit 21.
22, B1, B2 detection circuit 19, Dw, K1w, K2
It comprises a K1 and K2 operation circuit having a w operation circuit 22, a low-pass filter circuit 23 and a division circuit 24. First,
For simplicity, it is assumed that Δδi = ∫Δfid. Arithmetic circuit 20
In Δfi and Δδi, the coefficient A which is the sum of
11, A12, A21, A22, B1, B2 ((7)
Equation). These are input to a low-pass filter 21 having the same frequency characteristics, and the effects of noise and waveform distortion of the input signal are removed. Up to this point, the method is the same as that of FIG.
Outputs A11, A12,..., B of the low-pass filter 21
Instead of directly detecting K1 and K2 using 1, B2, the intermediate outputs Dw, K1w and K2w are calculated once.

## EQU8 ## Dw = A11.A22-A12.A21 K1w = A22.B1-A12.B2 (8) K2w = -A21.B1 + A11.B2 Variations in the calculation result of these Dw, K1w and K2w through the low-pass filter 23. After further removal of the components, K1 = K1
K1 and K2 are detected based on w / Dw and K2 = K2w / Dw. Here, A11, A12, A
Although the determinant was used when it was regarded as a matrix having the components 21 and A22 as components, any variable can be used as long as the variable can be separated so that the denominator and the numerator change similarly. According to the numerical simulation, since Dw, K1w, and K2w respond at substantially the same ratio, even if the low-pass filter 23 is used, there is almost no delay in detecting K1 and K2.

The above described K1, K in FIGS. 2, 3, and 4
K1 and K required for stabilization of power system by two detection circuits
2 can be identified, but when the amount of change in the signals ΔPi, Δfi, and Δδi used to identify K1 and K2 is small, the numerical calculation becomes unstable. For this reason,
Coefficients A11, A12,... For calculating K1, K2
It is necessary to monitor the absolute values of B1 and B2.

First, FIG. 5 shows coefficients A11, A12,.
4 shows a circuit for monitoring the absolute values of B1 and B2. FIG. 5 shows the coefficient A
, B1, and B2 detect an AND condition in which the absolute values are all equal to or greater than a constant value ε, and only when this condition is satisfied, that is, when IDENTON = 1, update calculation of K1 and K2 is performed. I do. By this means, K1 and K2 can be identified without numerical instability.

FIG. 6 shows coefficients A11, A12, A13, A
22 shows a monitoring circuit for the absolute value of the determinant Dw of No. FIG.
Only when the absolute value of Dw, which is the denominator of the division operation, is equal to or larger than the fixed value ε (in FIG. 4, since Dw is the denominator, Dw = 0
), K1 and K2 are updated. By this means, K1 and K2 can be identified without becoming numerically unstable even in the circuit of FIG.

Next, FIG. 7 shows a method for obtaining the oscillation frequency of the active power of the synchronous machine using K1 and K2 thus obtained. The motion of the synchronous machine can be approximated by a secondary vibration system. Here, the change Δω in the shaft speed of the synchronous machine is equal to the change Δf in the generator frequency, and the internal phase difference angle Δ
δ is equal to the integral of Δf ∫Δfdt. Therefore,

9: ΔP ≒ K1Δf + K2∫Δfdt That is, the secondary vibration system of FIG. 7 is obtained from ΔP ≒ K1Δω + K2Δδ (9). From FIG. 7, the power fluctuation frequency ωs and the attenuation time constants α, α1, and α2 are (10) to (1)
5) It can be identified using the equation.

(Equation 10)

[Equation 11]

(Equation 12)

(Equation 13)

[Equation 14]

(Equation 15)

In the above embodiment,

ΔPi = K1Δfi + K2∫Δfidt (16) However, when the power system can be expressed as the one-generator-infinity system shown in FIG. 9, the internal phase difference angle Δδ is obtained from the vector diagram of FIG. You can ask. In FIG. 9, Eq is the voltage behind the q-axis of the synchronous machine, VG is the terminal voltage of the synchronous machine, VB is the infinite bus voltage, Xq is the q-axis synchronous reactance of the synchronous machine, Xe is the system reactance, P is the active power, Q Represents reactive power, and in FIG. 8, δ is a phase difference angle between VB and Eq,
δq the phase difference angle of the VG and Eq, the [delta] _B represents the phase angle of the VG and VB. The vector relation is

[Equation 17]

(Equation 18) from now on,

[Equation 19]

(Equation 20) Therefore,

Δ = δq−δ _B (21) Using this δ,

## EQU22 ## By approximating ΔP ΔK1Δfi + K2Δδi (22), K1 and K2 can be obtained. Here, the subscript i of Δδi indicates the i-th data of Δδ.

In the ideal secondary vibration system shown in FIG.

ΔP = K1Δf + K2Δδ (23) However, ΔPm (mechanical torque change) in FIG. 7 has a slower response than the electric torque change ΔP, so it can be considered that ΔPm = 0. Although the equation of motion of a synchronous machine operating in conjunction with a general power system does not exactly match the ideal secondary vibration system as shown in FIG. 7, the model of FIG. 7 can be approximately applied. Therefore, the active power ΔP

(24) By identifying K1 and K2 from the measured data ΔP, Δf, and Δδ as ΔP ≒ K1Δf + K2Δδ (24), the power oscillation frequency ωs and the attenuation time constants α, α1, and α2, which are indexes of power system stability, are identified. Information necessary for the stability improvement control can be detected.

According to the present invention, ΔP, Δ
K1 and K2 are identified online using f, Δδ, and the like. FIG. 10 shows a K1 and K2 detection circuit using Δδi. In FIG. 10, since Pi, fi, and δi are all electrically detectable, the differential circuit 16 may be one stage (two stages in FIGS. 2 and 3), and the integrating circuit 9 is unnecessary (FIG. 2). Δi is used instead of に Δfdt in FIG. 3)
And the circuit configuration can be simplified.

Next, when power fluctuation between the systems becomes a problem, the power fluctuation frequency of the synchronous machine is set to a plurality of modes. in this case,

When approximating ΔP ≒ K1Δf + K2Δδ (25), these modes are averaged values for K1 and K2, and the actual fluctuation cannot be correctly expressed. Practically about 1.0Hz generated between nearby synchronous machines
(0.5-1.5Hz) local oscillation and about 0.3H
What is necessary is to consider the fluctuation between systems (z (0.1 to 0.3 Hz)). For this signal separation, a bandpass filter may be prepared for local oscillation and intersystem oscillation, and two sets of circuits (FIG. 11) that divide the passing frequency into local and intersystem oscillation frequencies may be prepared. In FIG. 11, Pi, fi
Are input to the band-pass filter 26, and ΔP
i, Δfi, Δδi through the integrator 9 are J, K1, K2
Input to the detection circuit 10. The power fluctuation frequency detection circuit 27 detects the fluctuation frequency fs based on the detected K1 and K2. The first-order lag circuit time constants T1 and T2 are tuned so that the center frequency fo of the band-pass filter 26 matches the detected oscillation frequency fs. That is, for example, it is assumed that the primary delay circuit time constants T1 and T2 in FIG. 11 are tuned to a local oscillation of 1 Hz (T1 = 2
π × 2.0, T2 = 2π × 0.667). In this case, even if an inter-system frequency of 0.1 to 0.3 Hz is applied to the circuit of FIG. 11, these signals are attenuated by the band-pass filter 26. It can be a value reflecting 5 to 1.5 Hz. Further, by tuning the first-order lag circuit time constants T1 and T2 so that the center frequency fo of the band-pass filter 26 of FIG. 11 matches the detected oscillation frequency fs, the local oscillation frequency can be detected more accurately. . The center frequency fo of the bandpass filter 26 in FIG.

Fo = (1 / 2π) (1 / √T1T2) (26) Therefore, if the bandwidth of T1 and T2, for example, T1 = K ² T2 (K ≧ 1),

Fo = (1 / 2π) (1 / T1) (1 / K) (27) T1 is adjusted so that fo becomes equal to fs.
Therefore, by automatically tuning fo to be equal to fs, K1 and K2 in the target area can be accurately obtained even when local oscillation and intersystem oscillation are included.

FIG. 12 shows the frequency characteristics of one stage of the band-pass filter used in FIG. 1 / T1 and 1 / T2 are the broken line frequencies on the low frequency and high frequency sides, and ωo =
At 1 / √T1T2 or fo = (1 / 2π) ωo, the gain is maximum and the phase change is zero.

[0019]

As described above, according to the present invention,
The power system fluctuation information such as the active power and the generator frequency is used as an input signal, and the active power is decomposed into the proportional components of the generator frequency and the time integral of the generator frequency, and the identified proportional coefficient K
1, K2, the fluctuation frequency and the damping constant of the power system can be detected at high speed and with high accuracy in real time, and the system stability can be remarkably improved regardless of the operation state of the power system. Further, when the absolute values of the active power change and the frequency change are small, the proportional constants K1 and K2 are updated only when the active power change and the frequency change are equal to or more than a certain value. K1, K2 without becoming
Can be identified. Further, by adding a low-pass filter to the K1 and K2 detection circuits, the effects of noise and waveform distortion can be eliminated. Further, when there are a plurality of power modes, a band-pass filter for separating these modes is provided, and the center frequency of the band-pass filter is automatically tuned so as to match the power fluctuation frequency, thereby achieving a desired power. The proportional constants (K1, K2) of the oscillation frequency can be accurately obtained.

[Brief description of the drawings]

FIG. 1 shows an excitation device for a synchronous machine according to an embodiment of the present invention.

FIG. 2 is a detailed diagram of a K1 and K2 detection circuit of the present invention.

FIG. 3 is a detailed diagram of a K1 and K2 detection circuit of the present invention.

FIG. 4 is a detailed diagram of a K1 and K2 detection circuit of the present invention.

FIG. 5 shows coefficients A11, A12,..., B1, B2 of the present invention.
Monitoring circuit for absolute value of

FIG. 6 shows coefficients A11, A12, A13, and A22.
Monitoring circuit for the absolute value of the determinant Dw

FIG. 7: ideal secondary vibration system

FIG. 8 is a vector diagram of a synchronous machine.

FIG. 9: One-machine infinity system diagram

FIG. 10 is a K1, K2 detection circuit using Δδ as an input according to the present invention.

FIG. 11 shows a K1 and K2 identification circuit for automatically tuning to a power fluctuation frequency according to the present invention.

FIG. 12 is a band-pass filter frequency characteristic diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Synchronous machine, 2 ... Instrument transformer, 3 ... Instrument current transformer, 4
... Signal detection circuit, 5 ... AVR voltage setting device, 6 ... Subtraction circuit, 7 ... Addition circuit, 8 ... Gate pulse generator, 9 ... Integration circuit, 10 ... K1, K2 detection circuit, 11 ... K1 set value circuit, 12 ... power system stabilizer, 13 ... transformer for excitation, 14 ... thyristor circuit, 15 ... field cutoff (FCB:
Field Circuit Breaker), 16 ... Imperfect differentiation circuit, 17
... J detection circuit, 18 ... K1, K2 detection circuit, 19 ... A1
1,..., B1, B2 detection circuit, 20... A11F,.
1, B2 arithmetic circuit, 21 ... low-pass filter circuit, 22
.., Dω, K1ω, K2ω arithmetic circuits, 23, low-pass filter circuits, 24, division circuits, 25, K1, K2 arithmetic circuits, 26, band-pass filters, 27, power fluctuation frequency detection circuits

Claims (9)

[Claims] 1. A system for calculating a deviation between a voltage of a synchronous machine and a set value, and a power system stabilizing unit for calculating a compensation output based on an active power change and a frequency change of the synchronous machine. In an exciting device for a synchronous machine that supplies an exciting current to a synchronous machine in accordance with an output obtained by adding a compensation output, the active power change (ΔP) is converted into the frequency change (Δf).
And means for separating the components into proportional constants (K1, K2) proportional to the integral (∫Δfdt) and means for identifying the proportional constant, and the compensation output is automatically adjusted based on the identified proportional constant. An exciting device for a synchronous machine characterized by the above-mentioned. 2. The method according to claim 1, wherein the means for identifying the proportionality constant includes the active power change (ΔPi) and K1 * Δ
The square (error J) of the deviation of fi + K2 * ∫Δfidt is obtained by the least squares method, and ∂J / ∂K1 = 0, ∂J / ∂K2
= 0 and the proportional constant (K1, K
Exciter for a synchronous machine, characterized in that 2) is obtained. And means for calculating a deviation between a voltage of the synchronous machine and a set value, and a power system stabilizing means for calculating a compensation output based on an active power change and a frequency change of the synchronous machine. In an exciting device for a synchronous machine that supplies an exciting current to a synchronous machine in accordance with an output obtained by adding a compensation output, the active power change (ΔP) is converted into the frequency change (Δf).
And the proportional constant of the component proportional to the internal phase difference angle (Δδ) (K
1, K2), and a means for identifying the proportional constant, wherein the compensation output is automatically adjusted based on the identified proportional constant. 4. The method according to claim 3, wherein the means for identifying the proportionality constant includes variables K1w and K2w based on the change in the active power (ΔPi), the change in the generator frequency (Δfi), and the internal phase difference angle (Δδi). , Dw, and K1 = K1w / D
w, K2 = K2w / Dw, the proportional constant (K1,
K2). 5. The method according to claim 1, wherein when the absolute value of the change in active power (ΔP) and the change in frequency (Δf) is small, the change in active power (ΔF)
P) and the exciter for a synchronous machine, wherein the proportionality constants (K1, K2) are updated only when the frequency change (Δf) is a certain value or more. 6. The synchronization according to claim 1, wherein a noise removing filter for removing noise of the active power change (ΔP) and the frequency change (Δf) is provided. Machine excitation device. 7. A synchronous machine according to claim 1, further comprising means for identifying a fluctuation frequency and an attenuation constant of active power of the synchronous machine using the obtained proportional constants (K1, K2). Exciter for synchronous machine. 8. A system according to claim 1, further comprising a band-pass filter for separating a plurality of power modes when the plurality of power modes are present, and for converting a signal after the mode separation into an active power variation. (ΔP) and a frequency change (Δf). 9. The apparatus according to claim 8, further comprising means for automatically following the center frequency of the band-pass filter so as to coincide with the fluctuation frequency of the active power, wherein a proportional constant (K1, K2) of a target power fluctuation frequency is provided. An exciter for a synchronous machine characterized by identifying: