JPS5922455B2 - Synchronous machine step-out prediction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a step-out prediction method for a synchronous machine that predicts step-out by detecting that the synchronous machine is in a dangerous state where there is a risk of step-out.

If a synchronous machine connected to an electric power system goes out of synchronization (out of synchronization), there is a risk that the entire system will fall into disorder.

Therefore, if the synchronous machine is in a dangerous state where it may lose synchronization, it is necessary to take measures such as performing field control to prevent the synchronization machine from going out of synchronization or separating the synchronous machine from the system. As a conventional synchronous machine step-out detection method,
A combination of power continuators and impedance relays is used.

As shown in Figure 1, if the horizontal axis is the resistance component R and the vertical axis is the reactance component X, then the vertical axis indicates that the power relay W passes through a predetermined set point a on the R axis The power relay W2 operates in the hatched area in the figure with the limit being a straight line parallel to , and the power relay W2 operates in the hatched area with the limit being a straight line parallel to the vertical axis passing through a predetermined set point -a on the R axis. , and the impedance relay Z is configured to operate in a region within a circle having a radius of a predetermined impedance z (=V flow value 7, which simply represents resistance and X represents reactance). There is. Therefore, when the synchronous machine goes out of step, the equivalent impedance seen from the relay installation point becomes the position Z during normal operation.
. When moving along the trajectory shown by curve 2 from the point, a step-out detection sequence circuit (not shown) operates due to the related operations of the power relays Wl, W2 and the impedance relay Z, and a step-out state is detected. . however,
This conventional method is a method for detecting synchronization after a synchronization machine has lost synchronization, and does not have a function of detecting synchronization in a dangerous state where synchronization may occur.

Further, as a conventional method having a shut-off measuring function, a shut-off measuring method using a stability limit control relay has been used.

For example, if we explain a synchronous generator, this means that the second
As shown in the figure, if the horizontal axis is active power P, the vertical axis is reactive power Q, the output limit curve of the synchronous generator is L, and the steady state stability limit curve is m, then curve g is the limit. A stability limit control relay or G that operates in the hatched area is provided, and the vector i coordinates of the synchronous generator output (=
When P+JQ) traces the trajectory shown by curve s from the point of abuse during normal operation, crosses stability limit curve g, and moves toward the out-of-step region, the excitation of the synchronous generator is strengthened by the operation of stability limit control relay G. to return the output vector coordinate W to the normal position,
It is configured to prevent transition to an out-of-step state. However, both the out-of-step measurement method using this stability limit control relay and the out-of-step detection method using a combination of a power relay and an impedance relay described above are based on the external electrical quantities of the synchronous machine (terminal voltage, output current, impedance,
output, reactive power, phase difference angle, etc.) is used as the detection input, and it is not based on the abnormal state of physical quantities inside the synchronous machine, so it is not possible to determine whether the detection result corresponds to the actual state of the synchronous machine. There are questionable drawbacks.

Therefore, as a result of various studies and tests, the inventors found that
As shown in Fig. 3, just before transition to step-out, the air gap magnetic flux fundamental wave component φ1 decreases rapidly, and the air gap magnetic flux harmonic component φ
K (however, K = 2, 3, 4,...) [Figure 3 shows the third harmonic component φ3] increases, and the function value of the fundamental component and the harmonic component We found that it is possible to predict step-out by detecting both the function value and the function value.

SUMMARY OF THE INVENTION Accordingly, a general object of the present invention is to provide a method for measuring out-of-step of a synchronous machine that can accurately predict that the synchronous machine is in a dangerous state in which there is a possibility of out-of-step.

In order to achieve this objective, the present invention separates and detects the air gap magnetic flux in a synchronous machine into a fundamental wave component and a harmonic component, and detects the relative change between a decrease in the fundamental wave component and an increase in the harmonic component. A feature of the present invention is that step-out is predicted by determining a predetermined function value and comparing the function value with a predetermined reference level.

In the above detonation measurement method, the air gap magnetic flux fundamental wave component φ1
It is possible to predict step-out by detecting that the ratio φ1/φ of φK and the air gap magnetic flux harmonic component φK has decreased below a predetermined reference level. Furthermore, the air gap magnetic flux waveform distortion rate γ=! 7; To 3F? It is also possible to predict step-out by detecting that K=2ra31●●●● has increased above a predetermined reference level.

Next, the detuning measurement method for a synchronous machine according to the present invention will be described in detail below with reference to accompanying drawings.

Figure 4 shows the control circuit of the synchronous generator, reference numeral 1.
0 indicates a synchronous generator, and the armature terminal of this synchronous generator 10 is connected to the power grid 14 via an impedance 12. Further, the armature terminal of the synchronous generator 10 is connected to the input terminal of the voltage deviation detector 16 via the voltage transformer 18, the reference voltage power supply V8 is connected to the voltage deviation detector 16, and the voltage deviation detector 16 The output terminal of is connected to the input terminal a of the addition calculator 20. Furthermore, an excitation system auxiliary device 22 such as a vibration suppressing stabilizer is connected to the input terminal b of the addition calculator 20. On the other hand, an air gap magnetic flux detection device 24 is installed inside the synchronous generator 10, and the output terminal of this air gap magnetic flux detection device 24 is connected to the fundamental wave analyzer 26, the third harmonic analyzer 28, the division calculator 30, and the signal level Connected to the input terminal of the detuning measuring device 36 consisting of a comparator 32 and an amplifier 34,
The output terminal of 6 is connected to the input terminal c of the adder 20.

The output terminal of the addition calculator 20 is connected to the input terminal of an automatic voltage regulator 38, and the output side of the automatic voltage regulator 38 is connected to the field winding 10a of the synchronous generator 10 via an excitation device 40.

Next, the system of the present invention will be explained along with the operation of the circuit configured as described above.

The generator terminal voltage generated by the synchronous generator 10 is supplied to the voltage deviation detector 16 via the voltage transformer 18 and compared with a predetermined reference voltage V8.
At the same time, the output of the excitation system auxiliary device 22 is supplied to the input terminal b of the addition calculator 20 and added thereto.
8 input terminals. The automatic voltage regulator 38 supplies an output corresponding to the input to the excitation device 40, and the synchronous generator 1
An excitation current such that the terminal voltage of 0 becomes a predetermined reference voltage 8 is supplied to the field winding 10a of the synchronous generator 10, and the synchronous generator 10 generates a voltage of a predetermined magnitude and connects it to the power system 14. are operated in sync with the In this case, the air gap magnetic flux φ, of the synchronous generator 10 is detected by the air gap magnetic flux detection device 24 installed in the synchronous generator 10, and the fundamental wave analyzer 26 and the third harmonic analyzer 28 of the detuning measuring device 36 is supplied to

The fundamental wave analyzer 26 and the third harmonic analyzer 28 extract the fundamental wave component φ1 and the third harmonic component φ3 of the supplied magnetic flux, and these two components φ1 and φ3 are respectively supplied to the division calculator 30. Then, the ratio φ1/φ3 of both components is calculated, and the output of this calculation is supplied to the signal level comparator 32. The ratio φ1/φ3 between the fundamental wave component φ1 and the third harmonic component φ3 of the air gap magnetic flux near the time when the synchronous machine moves out of synchronization has the characteristics shown in FIG. It is configured to generate an output when the magnitude of the signal decreases below the reference level R of FIG.

Therefore, when the synchronous generator 10 is in a normal state, that is, when it is not in a dangerous state that would cause it to step out, the signal level comparator 32 maintains a state of zero output, and the input terminal of the adder 20 is output from the amplifier 34. Since no input is supplied to C, the synchronous generator 10 is operating without any excitation current correction operation.For some reason, the synchronous generator 10 is in a dangerous state where it may step out. When the ratio φ1/φ3 of the fundamental wave component φ1 and the third harmonic component φ3 of the air gap magnetic flux decreases below the reference level R shown in FIG. An output signal indicating a dangerous state is amplified by the amplifier 34 and sent from the output terminal of the de-adjustment measuring device 36 to the input terminal C of the addition calculator 20.
supplied to

Therefore, the output of the addition calculator 20 increases, the automatic voltage regulator 38 strengthens the excitation of the field winding 10a via the excitation device 40, and the synchronous generator 10 is prevented from going out of step. . Also, if the rate of decrease (-dφ1/Dt) of the air gap magnetic flux fundamental wave component φ1 increases to a predetermined reference level or higher, or the rate of increase dφK/D of the air gap magnetic flux harmonic component φK
Detecting that t has increased above a predetermined reference level,
Step-out can be predicted in the same manner as in the above embodiment.

Furthermore, the air gap magnetic flux waveform distortion rate γ=7y; Honey? It is also possible to predict step-out similarly to the above-described embodiment by detecting that K=2 la 3111 has increased above a predetermined reference level.

Furthermore, although the above-described embodiments were directed to synchronous generators, the present invention can be applied to synchronous machines in general, such as synchronous motors and synchronous phase modifiers.

According to the method of the present invention, it is possible to accurately predict the out-of-step of the synchronous machine by detecting an abnormal state of the air gap magnetic flux of the synchronous machine, and the effect of contributing to improving the control function of the synchronous machine is extremely large.

Furthermore, the method of the present invention can be applied to detecting changes in the state of a synchronous machine other than step-out.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the operation of a conventional out-of-step detection method for a synchronous machine, Fig. 2 is an explanatory diagram showing the operation of a conventional out-of-step measurement method for a synchronous machine, and Fig. 3 is an explanatory diagram showing the operation of a conventional out-of-step detection method for a synchronous machine. 4 is a waveform diagram showing changes in the fundamental wave component of the air gap magnetic flux and the third harmonic component of the air gap magnetic flux in FIG. , FIG. 5 is a characteristic curve diagram showing a change in the ratio of the air gap magnetic flux fundamental wave component to the air gap magnetic flux third harmonic component before and after the synchronous machine loses synchronization. 10...Synchronous generator, 10a...Field winding, 12...Impedance, 14...
...Power system, 16... Voltage deviation detector, 18
... Voltage transformer, 20 ... Addition calculator, 22 ... Excitation system auxiliary device, 24 ...
... Air gap magnetic flux detection device, 26 ... Fundamental wave analyzer, 28 ... Third harmonic analyzer, 30 ...
・Division calculator, 32...Signal level comparator, 3
4... Amplifier, 36... De-adjustment measuring device, 38... Voltage regulator, 40... Excitation device.

Claims (1)

[Claims] 1. A predetermined function that detects the air gap magnetic flux in a synchronous machine by separating it into a fundamental wave component and a harmonic component, and expresses a relative change between a decrease in the fundamental wave component and an increase in the harmonic component. A step-out prediction method for a synchronous machine characterized by predicting step-out by calculating a function value and comparing the function value with a predetermined reference level. 2 As the predetermined function value, the ratio φ1/of the fundamental wave component φ1 and the harmonic component φK (K=2, 3, 4, ...)
2. A method for predicting synchronized machine synchronization as set forth in claim 1, wherein synchronization is predicted by using φK and detecting that this value has decreased below a predetermined reference level. 3 Using the air gap magnetic flux waveform distortion rate as the predetermined function value,
2. The method for predicting synchronization of a synchronous machine according to claim 1, wherein the synchronization machine predicts synchronization by detecting that this increase exceeds a predetermined reference level.