JPS5922456B2 - Synchronous machine step-out prediction method - Google Patents

Description

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

If a synchronous machine connected to an electric power system goes 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 relay and impedance relay is used.

As shown in Figure 1, if the horizontal axis is the resistance component R and the vertical axis is the reactance component The power relay W2 operates in a hatched area in the figure with parallel straight lines as the limit, and the power relay W2 operates in a 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 whose radius is a predetermined impedance z (=/d", T, which simply represents resistance and x represents reactance). Therefore, when the synchronous machine goes into an out-of-step state, the equivalent impedance seen from the relay installation point is at position Z during normal operation.
When moving from a point to a curved line, a step-out detection sequence circuit (not shown) is activated by the related operations of the power relays W, , W2 and the impedance relay Z, and a step-out condition is detected. Ru. However, this conventional method is a method for detecting synchronization after the synchronous 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 G that operates in the hatched area is provided, and the vector coordinate W of the synchronous generator output (=
P+JO迦5W during normal operation. When the trajectory shown by the curve s is drawn from the point and the stability limit curve g is crossed and the transition is to the out-of-step region, the excitation of the synchronous generator is strengthened by the operation of the stability limit control relay G and the output vector coordinate W is returned to normal. It is configured to return the motor to its original position and prevent it from shifting to an out-of-step state. However, 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 both rely 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 the air gap magnetic field energy W = However, φ (X, t) ... At the time t at the coordinate origin on the air gap circumference or at a point at a circumferential distance x. As shown in Fig. 3, we found that the magnetic flux decreases rapidly just before the transition to out-of-step, and the air gap magnetic field energy density [φ(X,
t)]2 function value, or the air gap magnetic field energy density [φ
(X, t)]2, the absolute value of the air gap magnetic field 1φ(X, t
) It was discovered that step-out can be predicted by detecting the function value of l.

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 object, the present invention is characterized in that the air gap magnetic field energy density of the synchronous machine is detected, and step-out is predicted by determining an abnormal decrease in the air gap magnetic field energy density.

In the aforementioned out-of-step measurement method for a synchronous machine, step-out can be predicted by detecting that the air gap magnetic field energy density has decreased below a predetermined reference level.

Next, the synchronous machine detuning measurement method according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 4 shows a control circuit for a synchronous generator, where reference numeral 10 indicates a synchronous generator, and an armature terminal of the synchronous generator 10 is connected to a 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 a voltage transformer 18, and the voltage deviation detector 1
6 is connected to the reference voltage power supply Vs, and the output terminal of the voltage deviation detector 16 is connected to the input terminal a of the addition calculator 20. Further, an excitation system auxiliary device 22 such as a vibration suppressing stabilizer is connected to the input terminal b of the summing calculator 20. On the other hand, an air gap magnetic flux detection device 24 is installed inside the synchronous generator 10,
The output terminal of this air gap magnetic flux detection device 24 is connected to the input terminal of a detuning measuring device 32 consisting of an air gap magnetic flux square integrator 26, a signal level comparator 28, and an amplifier 30. Connected to the input terminal c of the addition calculator 20.

The output terminal of the addition calculator 20 is connected to the input terminal of an automatic voltage regulator 34, and the output side of the automatic voltage regulator 34 is connected to the field winding 10a of the synchronous generator 10 via an excitation device 36. 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.
0, the output of the excitation system auxiliary device 22 is supplied to the input terminal b of the addition calculator 20 and added thereto, and the output of the addition calculator 20 is supplied to the input terminal a of the automatic voltage regulator 3.
4 input terminals. The automatic voltage regulator 34 supplies an output corresponding to the input to the excitation device 36, and the synchronous generator 1
An excitation current such that the terminal voltage of 0 becomes a value corresponding to a predetermined reference voltage V8 is supplied to the field winding 10a of the synchronous generator 10, and the synchronous generator 10 generates a voltage of a predetermined magnitude. It is operated in synchronization with the power grid 14. In this case, the air gap magnetic flux φ8 of the synchronous generator 10 is detected by the air gap magnetic flux detection device 24 installed in the synchronous generator 10, and is supplied to the air gap magnetic flux square integrator 26 of the detuning measuring device 32.

The air gap magnetic flux square integrator 26 calculates the air gap magnetic field energy W shown in equation (1) above from the supplied magnetic flux, and this calculated value W is supplied to the signal level comparator 28.
The signal level comparator 28 detects that the input signal is at a predetermined reference level R.
(See FIG. 3) The structure is such that the output becomes zero when the value is larger than that. Therefore, when the synchronous generator 10 is in a normal state, that is, when it is not in a dangerous state such as shifting to step-out, the output of the signal level comparator 28 is maintained at zero, and the input terminal of the adder 20 from the amplifier 30 is maintained. Since no input is supplied to c, the synchronous generator 10 is operated without any excitation current correction operation being performed. Now, due to some reason, the synchronous generator 10 is in a dangerous state where it may step out, and the air gap magnetic field energy W detected by the air gap magnetic flux square integrator 26 has been reduced to below the reference level R shown in FIG. 3. In this case, the output signal indicating that a dangerous condition has occurred at the output terminal of the signal level comparator 28 is amplified by the amplifier 30 and sent from the output terminal of the de-adjustment measuring device 32 to the input terminal of the addition calculator 20. c.

Therefore, the output of the force 1 calculation unit 20 increases, and the automatic voltage regulator 34 strengthens the excitation of the field winding 10a via the excitation device 36, thereby preventing the synchronous generator 10 from shifting to an out-of-step state. be done. In the example described above, step-out was predicted by detecting the magnitude of the air gap magnetic field energy W, but it was not possible to detect synchronization when the rate of decrease (-DW/Dt) of the air gap magnetic field energy W increased above a predetermined reference level. It is possible to detect and predict loss of synchronization.
In general, the air gap magnetic field energy density [φ(X, t)]2
or the function value of this air gap magnetic field energy density [φ(X
, t)] the absolute value of the air gap magnetic flux 1φ(X, t)l
It is also possible to predict out-of-step by detecting the function value of .

Although the above-described embodiments are directed to synchronous generators, the present invention can be similarly 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 that the in-phase machine is in a dangerous state in which there is a risk of step-out, and this has an extremely large effect in contributing to improving the control function of the synchronous machine. 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. FIG. 4 is a block diagram showing the configuration of a synchronous generator control circuit using the synchronous machine detuning measurement method according to the present invention. 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 ... Air gap magnetic flux 2
Multiplication integrator, 28...Signal level comparator, 30.
... Amplifier, 32 ... De-adjustment measuring device, 3
4..Voltage regulator, 36.. Excitation device.

Claims (1)

[Scope of Claims] 1. A step-out prediction method for a synchronous machine, characterized in that step-out is predicted by detecting the air-gap magnetic field energy density of the synchronous machine and determining an abnormal decrease in the air-gap magnetic field energy density. 2. The step-out prediction method for a synchronous machine according to claim 1, wherein the abnormal decrease is determined based on a decrease in the air gap magnetic field energy density below a predetermined reference level. 3. The step-out prediction method for a synchronous machine according to claim 1, wherein the abnormal decrease is determined by detecting that the rate of decrease in the air gap magnetic field energy density has increased to a predetermined reference level or higher.