JPS5922457B2 - 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 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 is configured to operate in a region within a circle whose radius is a predetermined impedance z (■ 4!/ 2 + x2, where only resistance is represented and X is reactance). has been done. 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, a step-out detection sequence circuit (not shown) operates due to the related operations of power relays W1, W2 and impedance relay Z, and a step-out state is detected. . However, this conventional method detects synchronization after the synchronous machine has lost synchronization, and does not have the function of measuring synchronization in a dangerous situation where there is a risk of synchronization. As a method having a condition measurement function, a de-conditioning measurement method using a stability limit control relay is 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 (=
When P+JQ) traces the trajectory shown by curve s from the towing point during normal operation and 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,
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 Since the external electrical quantities of the synchronous machine (terminal voltage, output current, impedance, output, reactive power, phase difference angle, etc.) are used as the detection input, it is not based on abnormal states of physical quantities that may occur inside the synchronous machine. , there is a drawback in that it is doubtful whether the detection results correspond to the actual state of the synchronous machine.Therefore, the inventors conducted various studies and tests, and found that the torque derived from the air gap magnetic flux of the synchronous machine is As shown in Figure 3, we found that the torque decreases dramatically just before transition to out-of-step, and found that it is possible to predict out-of-step in a synchronous machine by detecting the function value of the torque derived from the air gap magnetic flux.

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 step-out is predicted by determining that the torque derived from the air gap magnetic flux of the synchronous machine has abnormally decreased.

In the method for measuring out-of-step of a synchronous machine, it is possible to predict out-of-step by detecting that the torque guided by the air gap magnetic flux 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.

Figure 4 shows the control circuit of the synchronous generator, reference numeral 1.
0 indicates a synchronous generator, and the armature terminal of the 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 voltage deviation detector 1.
6 via a voltage transformer 18, a 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 input terminal a of the addition calculator 20. . In addition, an excitation system auxiliary device 22 such as a vibration suppression stabilizer is connected to the input terminal b of the addition calculator 20, and the output terminal of the addition calculator 20 is connected to the input terminal of the automatic voltage regulator 24. The output side of the voltage regulator 24 is connected via an excitation device 26 to the field winding 10a of the synchronous generator 10. An excitation current detector 28 is connected to the excitation circuit of the synchronous generator 10, and an air gap magnetic flux detector 30} and a field position detector 32 are installed inside the synchronous generator 10.

The output terminal of the exciting current detector 28 is connected to the field flux calculator 34.
is connected to the input terminal of the field flux calculator 34 through the input terminal a of the detuning measuring device 44, which includes an armature reaction flux analyzer 36, a torque analyzer 38, a signal level comparator 40, and an amplifier 42. .

The output terminal of the field flux calculator 34 is connected to the input terminal a1 of the armature reaction flux analyzer 36, and the output terminals of the air gap flux detector 30 and the field position detector 32 are connected to the detuning measuring device. 44 to input terminals B, } and C1 of the armature reaction flux analyzer 36. Further, the output terminals of the field flux calculator 34} and the armature reaction flux analyzer 36 are connected to the input terminals P1} and P2 of the torque analyzer 38, and the output terminal of the torque analyzer 38 is used for signal level comparison. The output terminal d of the detuning measuring device 44 is connected to the input terminal c of the adder 20 via the amplifier 40 and the amplifier 42.

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, and the output power of the addition calculator 20 is applied to the perturbation voltage regulator 2.
4 input terminals. The automatic voltage regulator 24 supplies an output corresponding to the input to the excitation device 26, 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 field flux calculator 34 calculates each instantaneous field flux φ based on the electromagnetic current 1f supplied from the exciting current detector 28.
f is determined and the determined output is supplied to the input terminal a1 of the armature reaction flux analyzer 36. Also detected by the air gap magnetic flux detector 30? The air gap magnetic flux φ is supplied to the input terminal B of the armature reaction flux analyzer 36, and the position of the field magnetic pole at each instant detected by the field position detector 32 is input to the armature reaction flux analyzer 36. 36 input terminal C1.

Generally, the following relationship φa'=φ, -φf exists between the air gap magnetic flux φ8, the field magnetic flux φf, and the armature reaction magnetic flux φa'.
...There is (1).

In the armature reaction flux analyzer 36, input terminals C,
Based on the position of the field poles at each instant supplied to
1) The calculation shown in the formula is performed, and the phase difference α with the field magnetic flux φf is
The armature reaction magnetic flux φ3 is detected. The field flux φf calculated by the field flux calculator 34 and the armature reaction magnetic flux φ detected by the armature action flux analyzer are supplied to input terminals Pl and P2 of the torque analyzer 38, respectively. Ru. Generally, the torque T generated by the air gap magnetic flux in a synchronous machine can be expressed by the following equation.

'9τ No However, x... Circumferential distance from the coordinate origin on the circumference of the gap α... Phase difference between field magnetic flux φf and armature reaction magnetic flux φ3 In the torque analyzer 38, for example, The torque for one pole pitch is calculated, and the torque T is calculated from the field flux φf for one pole pitch and the armature reaction magnetic flux φ3 for one pole pitch supplied to the input terminals P2 and P1 according to the above equation (2). The detected output signal is supplied to a signal level comparator 40.

The signal level comparator 40 detects that the input signal is at a predetermined reference level R.
(See Fig. 3) The configuration 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 where it will go out of synchronization,
Since the output of the signal level comparator 40 is maintained at zero and no input is supplied from the amplifier 42 to the human power terminal c of the addition calculator 20, the synchronous generator 10 is operated without correcting the excitation current. There is. Now, due to some reason, the synchronous generator 10 is in a dangerous state where it may lose synchronization.
When the torque detection signal supplied to the signal level comparator 40 decreases below the reference level R shown in FIG. The signal is amplified by the amplifier 42 and supplied from the output terminal of the detuning measuring device 44 to the input terminal c of the addition calculator 20.

Therefore, the output of the adder 20 increases, the automatic voltage regulator 24 strengthens the excitation of the field winding 10a via the excitation device 26, and the synchronous generator 10 is prevented from going out of synchronization. . In the above-described embodiments, the magnitude of the torque T derived from the air gap magnetic flux was detected, but in general, step-out can be predicted by detecting the function value of the torque T derived from the air gap magnetic flux. For example, Decrease rate of torque T derived from air gap magnetic flux (
-DT/Dt) increases above a predetermined reference level, it is possible to predict out-of-step as in the embodiment described above.

Although the above-described embodiments 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 a synchronous machine by detecting the function value of the torque derived from the air gap magnetic flux, and the effect of contributing to the 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 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 a detuning 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 ...
... Urging voltage regulator, 26... Excitation device, 28
...Exciting current detector, 30...Air gap magnetic flux detector, 32...Field position detector, 34...
... Field magnetic flux calculator, 36 ... Armature reaction magnetic flux analyzer, 38 ... Torque analyzer, 40.
... Signal level comparator, 42 ... Amplifier, 44 ... De-tuning measuring device.

Claims (1)

[Scope of Claims] 1. A step-out prediction method for a synchronous machine, characterized in that step-out is predicted by determining that the torque derived from the air-gap magnetic flux of the synchronous machine has decreased abnormally. 2. The step-out prediction method for a synchronous machine according to claim 1, wherein the abnormal decrease is determined based on the fact that the torque derived from the air gap magnetic flux has decreased 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 based on an increase in the rate of decrease in the torque derived from the air gap magnetic flux to a predetermined reference level or higher. .