JP2022168384A - generator excitation system - Google Patents

Abstract

To provide a generator excitation system capable of effectively reducing variations in output power of a generator accompanying variations in a system voltage in a case where an output voltage of the generator is operated under constant control.SOLUTION: With a generator excitation system, a generator 1 is connected to a system via a transformer 2. An automatic voltage regulator 7 is provided that generates a field current command for keeping an output voltage of the generator 1 constant based on a deviation signal between an output voltage of the generator 1 detected by a first meter transformer 3 located between the generator 1 and the transformer 2 and a set voltage preset by a voltage setter 6. The automatic voltage regulator 7 calculates a fluctuating value of a system voltage detected by a second meter transformer 5 located between the transformer 2 and a system 3, and corrects the deviation signal by the fluctuating value to suppress output power fluctuations of the generator 1 by varying the field current command based on the deviation signal after correction.SELECTED DRAWING: Figure 1

Description

The present application relates to generator excitation systems.

Conventionally, a generator excitation system equipped with an automatic voltage regulator (hereinafter referred to as AVR) that suppresses fluctuations in the output power of a generator causes fluctuations in the transmission system in which the generators are paralleled during AVR control. When it occurs, the response time of the excitation device is increased, or the stability contribution to the transient fluctuation is achieved by increasing the top voltage of the field system, or the PSS (Power System Stabilizer) effective for dynamic steady-state stability is used. ) to the AVR contributes to system stabilization measures (see, for example, Patent Document 1 below).

JP-A-2002-34298

In a conventional AVR, if the synchronous impedance of the generator has a value ten times that of the impedance of the transformer, and the output voltage of the generator is operated under constant control with the AVR, the system voltage will be reduced by about ±0.1%. A variation of ±1% occurs in the output power of the generator with respect to the variation of . For this reason, there are problems such as the torsional vibration of the generator shaft or the adverse effect of the output control of the generator.

The present application discloses a technique for solving the above problems, and when the output voltage of the generator is operated under constant control, the fluctuation of the output power of the generator due to the fluctuation of the system voltage is effectively controlled. It is an object of the present invention to provide a generator excitation system capable of reducing the

The generator excitation system disclosed herein comprises:
A generator is connected to the grid through a transformer, and the output voltage of the generator detected by a first voltage transformer located between the generator and the transformer, and the voltage setter in advance An automatic voltage regulator that generates a field current command that keeps the output voltage of the generator constant based on a deviation signal from a set voltage, wherein the automatic voltage regulator is provided between the transformer and the system. A variation value of the system voltage detected by the second instrument transformer positioned between is calculated, the deviation signal is corrected by the variation value, and the field current command is changed based on the corrected deviation signal. He is trying to suppress the output electric power fluctuation of the said generator by this.

According to the generator excitation system disclosed in the present application, when the output voltage of the generator is operated under constant control, it is possible to effectively reduce fluctuations in the output power of the generator due to fluctuations in the system voltage. Torsional vibration and adverse effects on output voltage control can be suppressed.

1 is a block diagram showing a schematic configuration of a generator excitation system according to Embodiment 1 of the present application; FIG.

Embodiment 1.
FIG. 1 is a block diagram showing a schematic configuration of a generator excitation system according to Embodiment 1. FIG.
The generator excitation system in the first embodiment is a power generation facility in which a generator 1 is connected to a grid 3 via a transformer 2, and an automatic voltage regulator (AVR) 7 connects the generator 1 and a transformer. The output voltage Vg of the generator 1 is detected from the first instrument transformer 4 located between the transformer 2, and the system voltage Vs is detected from the second instrument transformer 5 located between the transformer 2 and the system 3. do. The AVR 7 outputs a field current command I* for increasing/decreasing the field current If to an exciter 8 (abbreviated as EXC in FIG. 1). Since the exciter 8 adjusts the field current If of the generator 1 by increasing/decreasing it according to the field current command I*, the generator 1 changes its output according to the change in the field current If. Voltage Vg is controlled.

Here, in a power generation facility where the synchronous impedance Xg of the generator 1 is ten times the impedance Xm of the transformer 2 (Xg = 10 x Xm), the constant control of the output voltage Vg of the generator 1 by the AVR 7 Below, when a fluctuation value ΔVs of ±0.1% occurs with respect to the system voltage Vs (ΔVs = ±0.1%), the output power P of the generator 1 accordingly has a ±1% Fluctuation occurs, which becomes a factor that impairs the stabilization of the system 3.

Therefore, in the present application, fluctuations in the output power P of the generator 1 are suppressed in the following manner. The principle for suppressing fluctuations in the output power P of the generator 1 will be described below.

The output power P of the generator 1 is the generator back voltage Vb which is the internal induced voltage of the generator 1, the system voltage Vs, the phase difference angle δ between the generator 1 and the system 3, the impedance Xm of the transformer 2, the generator Using a synchronous impedance Xg of 1 gives:

P=Vb·Vs·sin δ/(Xm+Xg) (1)

In addition, an approximate relationship represented by the following equation (2) is established among the generator back voltage Vb, the output voltage Vg of the generator 1, and the system voltage Vs.

Xg・ΔVs+Xm・ΔVb=(Xg+Xm)・ΔVg (2)

Further, under the constant control of the output voltage Vg of the generator 1 by the AVR 7, the control is performed with the fluctuation value ΔVg=0 as a target.

ΔVb=(Xg/Xm)・ΔVs (3)

From the relationships of the above equations (1), (2), and (3), if the fluctuation value of the output power P of the generator 1 is ΔP, ΔP is given by the following equation (4).

ΔP≈(ΔVs+ΔVb)·sin δ/(Xm+Xg)
∝(Xm+Xg)・ΔVs/Xm (4)

Therefore, in order to suppress the fluctuation value ΔP of the output power P of the generator 1, when the voltage fluctuation occurs in the system 3, the system voltage fluctuation value ΔVs is canceled by the background voltage fluctuation value ΔVb of the generator 1 by the AVR 7. You should do it like this. That is, control is performed to adjust the generator back voltage Vb by the field current If of the generator 1 so that ΔVb=−ΔVs. Thus, as can be seen from the equation (4), the fluctuation of the output power P of the generator 1 can be suppressed to ΔP≈0.

Next, the operation of the generator excitation system of the first embodiment will be explained.
When no voltage fluctuation occurs in the system 3 (ΔVs≈0), the output voltage Vg of the generator 1 detected by the first instrument transformer 4 located between the generator 1 and the transformer 2 is It is compared with the voltage set value 90R set by the voltage setter 6, and outputs a deviation signal ΔVd indicating the difference between the output voltage Vg and the voltage set value 90R.

At this time, if the deviation signal ΔVd is negative, that is, if Vg<90R, the AVR 7 issues a field current command I* to the exciter 8 so as to increase the field current If. Conversely, if the deviation signal ΔVd is positive, that is, if Vg>90R, the AVR 7 issues a field current command I* to the exciter 8 so as to reduce the field current If. As a result, the output voltage Vg of the generator 1 is controlled to be constant.

On the other hand, when a voltage fluctuation occurs in the system 3, the AVR 7 detects a system voltage fluctuation value Vs detected by the second instrument transformer 5 located between the transformer 2 and the system 3. ΔVs is calculated. Subsequently, the AVR 7 corrects the deviation signal ΔVd between the output voltage Vg of the generator 1 and the voltage set value 90R based on the system voltage fluctuation value ΔVs. That is, assuming that the deviation signal after correction is ΔVdc, the following equation (5) is obtained.

ΔVdc=ΔVd−ΔVs (5)

Then, the AVR 7 changes the field current command I* given from the AVR 7 to the exciter 8 based on the corrected deviation signal ΔVdc within the allowable voltage range of the generator 1 . Accordingly, the field current If of the generator 1 output from the exciter 8 is adjusted so that ΔVb=-ΔVs. As a result, as shown in the above-described formula (4), fluctuations in the output power P of the generator 1 due to fluctuations in the system voltage Vs under constant control of the output voltage Vg of the generator 1 can be suppressed to ΔP≈0. can be done.

As described above, in the generator excitation system of the first embodiment, when the system voltage Vs fluctuates under constant control of the output voltage of the generator 1 in the AVR 7, the field of the generator 1 is controlled by the AVR 7. Since the voltage Vb behind the generator can be adjusted by the magnetic current If, fluctuations in the output power P of the generator 1 can be suppressed, and the shaft torsional vibration of the generator 1 and adverse effects on output voltage control can be reduced. be able to.

It should be noted that although the present application has described exemplary embodiments, the various features, aspects, and functions described in the embodiments are not limited to application of particular embodiments, but alone. , or in various combinations applicable to the embodiments.

Therefore, countless modifications not illustrated are envisioned within the scope of the technology disclosed in the present application. For example, the modification, addition, or omission of at least one component shall be included.

1 generator, 2 transformer, 3 system, 4 first instrument transformer, 5 second instrument transformer, 6 voltage setter, 7 automatic voltage regulator (AVR), 8 exciter (EXC).

Claims (1)

A generator is connected to the grid through a transformer, and the output voltage of the generator detected by a first voltage transformer located between the generator and the transformer, and the voltage setter in advance An automatic voltage regulator that generates a field current command that keeps the output voltage of the generator constant based on a deviation signal from a set voltage, wherein the automatic voltage regulator is provided between the transformer and the system. A variation value of the system voltage detected by the second instrument transformer positioned between is calculated, the deviation signal is corrected by the variation value, and the field current command is changed based on the corrected deviation signal. A generator excitation system that suppresses output power fluctuations of the generator.

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