JPS5922453B2 - 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 relay and impedance relay is used.

This means that, 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 the hatched area in the figure with parallel straight lines as the limit, 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 has a predetermined impedance Z (■5/to 2+x
2, where X represents resistance and X represents reactance). Therefore, when the synchronous machine enters 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 along a trajectory shown by curve l, power relays W1, W2 and impedance relay Z
The step-out detection sequence circuit (
(not shown) operates to detect a step-out condition. 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 step-out measurement function, a step-out prediction 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+JQ) is W when operating normally. 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, both the out-of-step measurement method using a relay for stability limit control and the out-of-step detection method using a combination of a power relay and an impedance or 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 whether the detection result corresponds to the actual state of the synchronous machine or not. has some questionable drawbacks. Therefore, as a result of various studies and tests, the inventors found that the air gap magnetic flux of the synchronous machine (the figure shows the air gap magnetic flux fundamental wave component) suddenly decreases just before the step goes out, as shown in Figure 3. They discovered that it is possible to predict out-of-step by monitoring the level or rate of change of the air-gap magnetic flux and determining abnormal decreases from this.

Therefore, 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 where the machine may go out-of-step. According to the present invention, the step-out is achieved by detecting the air-gap magnetic flux of the synchronous machine and predicting the step-out by determining an abnormal decrease in its magnitude. In this step-out measurement method,
If the high frequency component contained in the detected air gap magnetic flux cannot be ignored, after removing the harmonic component, an abnormal decrease in the magnitude of the fundamental component may be determined.

The above-mentioned out-of-step measurement method places an air-gap magnetic flux detection device inside the synchronous machine, and sequentially transfers the output of this air-gap magnetic flux detection device to a waveform analyzer, a signal level comparator, and an amplifier. The amplifier may be arranged to generate a predetermined output signal when a condition that is likely to occur is reached.

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 the armature terminal of the synchronous generator 10 is connected to the power grid 14 via an impedance 12. The armature terminal of the 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 output terminal of the voltage deviation detector 16 is connected to the voltage deviation detector 16. 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 a waveform analyzer 26 such as a fundamental wave and a signal level comparator 28.
and an amplifier 30, and the output terminal of the detuning measuring device 32 is connected to the input terminal c of the addition calculator 20.

The output terminal of the summing amplifier 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 via an excitation device 36 to the field winding 10a of the synchronous generator 10.

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.
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 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 and connects it to the power system 14.
are operated in sync with the In this case, the synchronous generator 10
The air gap magnetic flux φ, is detected by the air gap magnetic flux detection device 24 installed in the synchronous generator 10 and supplied to the waveform analyzer 26 of the detuning measurement device 32.

In the waveform analyzer 26, the fundamental wave component φ, of the supplied magnetic flux φ8 is extracted, and this fundamental wave component φ1 is supplied to the signal level comparator 28. The signal level comparator 28 is configured such that its output becomes zero when the input signal is p greater than a predetermined reference level R (see FIG. 3). Therefore, when the synchronous generator 10 is in a normal state, that is, when it is not in a dangerous state where it will go out of synchronization, the signal level comparator 28 maintains a state of zero output, and the output from the amplifier 30 is
Since no input is supplied to the input terminal c of the synchronous generator 1
0 is operating without correcting the excitation current.
Now, due to some reason, the synchronous generator 10 is in a dangerous state where it may step out, and the magnetic flux fundamental wave component φ1 detected by the air gap magnetic flux detector 24 and extracted from the waveform analyzer 26 is shown in FIG. When the signal level has decreased below the reference level R, 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. 0 supplied to the input terminal c of the summing unit 20. Therefore, the output of the summing amplifier 20 increases, and the automatic voltage regulator 34
6, the excitation of the field winding 10a is strengthened, and the synchronous generator 1
0 transition to an out-of-step state is prevented.

Further, although the embodiments described above are directed to synchronous generators, the method of 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 the out-of-step of the synchronous machine by detecting an abnormal decrease in the level of the air gap magnetic flux, which has an extremely large effect on improving the control function of the synchronous machine.

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 the conventional out-of-step detection method for synchronous machines, Fig. 2 is an explanatory diagram showing the operation of the conventional out-of-step measurement method for synchronous machines, and Fig. 3 is an explanatory diagram showing the operation of the conventional out-of-step detection method for synchronous machines. FIG. 4 is a waveform diagram showing changes in the air gap magnetic flux fundamental wave component before and after step-out. FIG. 4 is a block connection diagram showing the configuration of a synchronous generator control circuit using the step-out measurement method for a synchronous machine 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 ... Waveform analyzer, 28 ... Signal level comparator, 30 ...
・Amplifier, 32... De-adjustment measuring device, 34...
...Compulsive voltage regulator, 36... Excitation device.

Claims (1)

[Claims] 1. A step-out prediction method for a synchronous machine, which is characterized by predicting step-out by detecting the air-gap magnetic flux of the synchronous machine and determining an abnormal decrease in its magnitude.