JPS5922454B2 - 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 (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 there is a risk of it going out of synchronization, it is necessary to perform field control to prevent the synchronous machine from going out of synchronization, or to isolate the synchronous machine from the system. As a conventional synchronous machine step-out detection method,
By combining a power relay and an impedance relay,
method 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 (=~'T7 represents resistance and X represents reactance). Therefore, when the synchronous machine goes out of synch, the equivalent impedance seen from the relay installation point becomes the position Z during normal operation.
. When moving from a point along a trajectory shown by curve l, a step-out detection sequence circuit (not shown) operates due to the related operations of power relays W, , W2 and impedance relay Z, and a step-out state is detected. Ru. 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, in the case of a synchronous generator, as shown in Figure 2, the horizontal axis represents active power P, the vertical axis represents reactive power Q, and the output limit curve of the synchronous generator is L. When the stability limit curve is defined as m, a stability limit control relay G that operates in the hatched area with curve g as the limit is provided, and the vector coordinate W (=P
+JQ) is W 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 in the direction of 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 normalized. It is configured to return the motor to a normal position and prevent it from shifting 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.) as the input for detection, and because it is not based on abnormal states of physical quantities inside the synchronous machine, the detection results correspond to the actual state of the synchronous machine. There is a difficulty in doubting whether this is the case. Therefore, as a result of various studies and tests, the inventors found that the frequency of the armature current increases just before the transition to step-out, as shown in Figure 3, and it is possible to detect the frequency of the armature current. We found that it is possible to predict loss of synchronization.

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 detects the frequency of the armature current of a synchronous machine and predicts a step-out when the frequency increases to a predetermined reference level or higher. Features.

In addition, in the above-mentioned detuning measurement method, a current transformer is connected to the conductor wire connected to the synchronous machine's electric wire, and the output containing the frequency component of this current transformer is passed through a current frequency analyzer, a signal level comparator, and a signal level comparator. The signals may be sequentially transferred to amplifiers, and the amplifiers may be configured to generate a predetermined output signal when a condition in which the synchronous machine is likely to lose synchronization 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. Reference numeral 10 indicates a synchronous generator, and the armature terminal of this synchronous generator 10 is connected to a power system 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,
A reference voltage power supply V8 is connected to the voltage deviation detector 16, and an output terminal of the voltage deviation detector 16 is connected to an 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, a current transformer 2 is connected to the output conductor of the synchronous generator 10.
4 is connected, and the secondary terminal of this current transformer 24 is connected to the input terminal of a detuning measuring device 32 consisting of a current frequency analyzer 26, a signal level comparator 28, and an amplifier 30. The output terminal is 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.
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 that makes the terminal voltage i become a predetermined reference voltage V is supplied to the field winding 10a of the synchronous generator 10, and the synchronous generator 10 generates a voltage of a predetermined magnitude to generate electric power. System 1
It is operated in synchronization with 4. In this case, synchronous generator 1
The zero armature current is detected by the current transformer 24 and supplied to the current frequency analyzer 26 of the detent measuring device 32.

The current frequency analyzer 26 extracts the frequency f of the supplied armature current, and this frequency f is supplied to the signal level comparator 28. The signal level comparator 28 is configured so that the output becomes zero when the input signal is lower 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 that would cause it to step out, the signal level comparator 28 maintains a state of zero output, and the input terminal of the adder 20 is output from the amplifier 30. Since no input is supplied to c, the synchronous generator 10 is operated without any excitation current correction operation being performed. now,
If the synchronous generator 10 is in a dangerous state where it may step out for some reason and the armature current frequency f increases above the reference level R shown in FIG. 3, the output of the signal level comparator 28 An output signal indicating that the terminal is in a dangerous state is amplified by the amplifier 30 and is supplied from the output terminal of the de-adjustment measuring device 32 to the input terminal c of the adder 20. Therefore, the output of the summing amplifier 20 increases, and the automatic voltage regulator 34 increases the field winding 10a through the excitation device 36.
The excitation of the synchronous generator 10 is strengthened to prevent the synchronous generator 10 from going out of step. Although the above embodiment was aimed at a synchronous generator,
The method of the present invention can be applied to all synchronous machines such as synchronous motors and synchronous phase modifiers.

According to the method of the present invention, step-out of the synchronous machine can be accurately predicted by detecting the armature current frequency of the synchronous machine, and the effect of contributing to improvement of the synchronous machine control function 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 Description of the Drawings] 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 4 is a waveform diagram showing changes in the armature current frequency before and after the synchronous machine loses synchronization, and FIG. 4 is a block connection diagram showing the configuration of a synchronous generator control circuit using the synchronous machine out-of-step measurement method according to the present invention. 10...Synchronous generator, 10a...Field winding, 12...Impedance, 14...
...Power system, 16...Power deviation detector, 18
... Voltage transformer, 20 ... Addition calculator, 22 ... Excitation system auxiliary device, 24 ...
...Current transformer, 26...Current frequency analyzer, 2
8... Signal level comparator, 30... Amplifier, 32... De-tuning measuring device, 34...
Mountain motion voltage regulator, 36...excitation device.

Claims (1)

[Claims] 1. A step-out prediction method for a synchronous machine, which is characterized by detecting the frequency of an armature current of a synchronous machine and predicting a step-out when the detected frequency increases to a predetermined reference level or higher.