JPH0256017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a braking resistor control method that repeatedly controls closing and opening of a braking resistor to improve the stability of an electric power system.

Technical background of the invention In recent years, along with the expansion of electric power systems and the increase in the capacity of power generation units, large-capacity and long-distance power transmission has become necessary due to technical and social factors such as difficulty in obtaining power supply locations and difficulty in securing power transmission routes. Along with this, the issue of stable operation of power systems has become a focus of attention.
Various measures have been proposed to improve the stability of this power system, and here we will discuss one method that involves introducing a braking resistor into the power system.

Generally, when a system failure such as a short circuit or ground fault occurs in the power system, the generator output decreases instantaneously. However, the mechanical input torque to the generators in the power system remains unchanged immediately after a fault occurs and cannot be controlled rapidly. Therefore, the decrease in the generator output is absorbed as mechanical kinetic energy of the generator rotor, and if left as is, it may lead to a step-out phenomenon.

Therefore, in such cases, it is recommended to install a braking resistor at or near the generator terminal and input it to the power grid immediately after a failure occurs to absorb and consume power equivalent to the acceleration energy to the generator rotor. For example, the generator does not go out of step and the stability of the power system can be ensured.

On the other hand, in this case, in the conventional control method, the braking resistor is turned on only once immediately after the occurrence of a failure, and contributes to the transient stability of the first wave of phase difference angle fluctuation; Once this is achieved, the system fluctuations will gradually subside due to various braking effects such as the AVR of the generators within the power system.

Problems with the Background Art Naturally, if the system is connected to an external system through interconnection lines with relatively weak power transmission capacity (long-distance lines, few lines, etc.), long periods of system fluctuations may occur. There is a tendency for components to be excited and their convergence to be slow. Therefore, in the conventional control method as described above, although the transient stability of the first wave of phase difference angle oscillation due to the occurrence of a system failure is ensured, the long-period system oscillation does not converge for a long time after that, and the power system This is not desirable in terms of stable operation.

Purpose of the Invention The present invention has been made in view of the above-mentioned circumstances, and its purpose is to improve the transient stability of the first wave of phase difference angle fluctuation in response to a major failure in the power system, as well as to improve the transient stability of the second wave.
An object of the present invention is to provide a control method for a braking resistor that can quickly converge frequency fluctuations in a system after a wave.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a device that secures the stability of the power system by inserting a braking resistor into the power system when a serious failure that threatens the stability of the power system occurs. The present invention is characterized in that when the serious failure occurs, the braking resistor is repeatedly controlled to close and open in response to fluctuations in the rotational speed of a rotating machine operated within the power system.

In addition, in the above, the braking resistor capacity when securing transient stability of the first wave is different from the braking resistor capacity when suppressing system frequency fluctuations from the second wave onwards, that is, the braking resistor capacity is variable. It is characterized by being made possible.

Embodiment of the Invention Hereinafter, an embodiment of the present invention shown in the drawings will be described. FIG. 1 shows an example of the configuration of a braking resistor control method according to the present invention. In the figure 1
is the power system, 2 is the bus bar where the braking resistor is installed,
3 is a braking resistor, and 4 is a braking resistor that is connected to and disconnected from the bus bar 2 by closing and opening the arm and breaker 3. In addition, 5 is a current transformer that detects the current of the line connected to the bus 2, 6 is a transformer that detects the voltage of the bus 2, and 7 is the input of the current and voltage detected by the current transformer 5 and transformer 6. This is a power converter that combines electric power and outputs a voltage proportional to the combined electric power.

On the other hand, 9 is a turbine generator which is a typical rotating machine connected to and operated by the power system 1, 10 is a gear such as a turning gear attached to the rotating shaft of the turbine generator 9, and 11 is the rotation of the gear 10. 12 is an electromagnetic pickup for detecting the number of revolutions; 12 is a measuring device that receives the output signal 11a of the electromagnetic pickup 11 and outputs two types of rotational speed signals; the details will be described later; 13
14 is a transmitter that transmits the output signal from the measuring device 12; 14 is a receiver that receives the transmission signal from the transmitter 13; 16 is the output pressure 7a of the power converter 7 and the rotation speed signal 14a from the receiver 14; This is a braking resistor control device which takes as an input signal and outputs a closing/opening command 16a for the disconnector 3 based on this, the details of which will be described later.

FIG. 2 shows a block diagram of an example of the configuration of the measuring device 12. As shown in FIG. In the figure, 102 is a pulse transmitter that converts the output signal 14a of the receiver 14 shown in FIG. a ripple removal circuit for obtaining the rotation speed ω of the generator 9;
Reference numeral 104 indicates an incomplete differentiation circuit for approximately differentiating the output of the ripple removal circuit 103 to detect a change in rotational speed Δω, and reference numerals 105 and 107 indicate comparators, respectively. Here, the comparators 105 and 107 compare the rotational speed change Δω with the set values Kω ₁ and Kω ₂ , respectively, and output the output signals 105a and 107a only when they are greater than or equal to the set values Kω ₁ and Kω ₂ . Each occurs separately.
That is, the measuring device 12 includes a device that detects the rotational speed change Δω of the turbine generator 9 and a comparator that compares the change Δω with two set values Kω ₁ and Kω ₂ .

Figures 3a and 3b show the control equipment 16 in Figure 1.
This is a block diagram showing an example of the configuration. In the figure, 201 is a starting circuit that starts a series of controls for closing and opening the braking resistor 4. In this startup circuit 201, 202 is the output voltage 7 of the power converter 7.
An incomplete differentiator circuit 203 receives a as an input and detects the power change amount (-ΔP), and 203 compares the magnitude of the output signal of the incomplete differentiator circuit 202 with a set value _Kp , and when it is greater than or equal to the set value Kp. A comparator 204 that only generates an output signal is a hold circuit that holds the output signal of the comparator 203 for a predetermined period of time. Further, 206 is an AND circuit which inputs the output of the starting circuit 201, that is, the output signal of the hold circuit 204, and the signal 105a received via the receiver 14, and the AND output 206a is the output signal of the braking resistor 4. This is a command, and the output signal 16a of the control device 16 turns on the sender and disconnector 3. Further, 209 is a hold circuit that holds the AND output 206a, which is the input command, for a certain period of time, and 210 is the output signal of this hold circuit 209 and the signal 10 received via the receiver 14.
7a as an input, and its AND output 210a is a command to open the braking resistor 4, and the output signal 16a of the control device 16 is used to open the sender and disconnector 3.

Note that the set value K _p mentioned above serves as a criterion for determining a serious failure in the system. Further, a typical turbine generator means a turbine generator that exhibits a rotational speed fluctuation that most closely approximates the frequency fluctuation of the entire system, and this can be easily selected by performing stability analysis.

Next, the operation of the braking resistor control system of the present invention based on the above configuration will be explained.

Now, if a system failure such as a ground fault or short circuit occurs in the power system 1, the current and voltage are detected by the current transformer 5 and the transformer 6, and the output voltage 7a of the power converter 7 that uses these as inputs suddenly increases. do. Then, this power change amount (-ΔP) is applied to the starting circuit 201 in the control device 16.
is detected by the incomplete differentiation circuit 202. If this power change (-ΔD) is the comparator 20
₃ , it is determined that a serious failure that threatens the stability of the power system has occurred, and the comparator 203
Activate the hold circuit 204 by the output of
The starting conditions for closing/opening control of the braking resistor 4 are established.

On the other hand, the rotational speed of the turbine generator 9 increases with the occurrence of such a serious failure. In this case, the output 1 of the electromagnetic pickup 11 is proportional to this rotational speed.
1a is a pulse oscillator 102 and a ripple removal circuit 1
03, the incomplete differentiation circuit 104 detects the change Δω, which is detected by each comparator 105,
Added to 107. If this amount of change Δω reaches the set value Kω ₁ or more of the comparator 105, the output of the comparator 105 is generated, and this is transmitted to the transmitter 1.
3 and received by the receiver 14 and input into the control device 16. As a result, the AND circuit 206 is operated together with the output of the starting circuit 201, and the control device 16 closes the breaker 3 by the closing command 206a and incorporates the braking resistor 4 into the system. By incorporating this braking resistor 4 into the system, the electrical output of the generator in the power system 1 increases and the speed is reduced. As a result, the rotational speed of the turbine generator 9, which had once increased, decreases. Thereafter, when this rotational speed change Δω reaches the set value Kω ₂ of the comparator 107 or less, an output signal of the comparator 107 is generated, which is transmitted by the transmitter 13 and received by the receiver 14, and is sent to the control device. 16. As a result, the AND circuit 210 is operated together with the closing command signal 206a held by the hold circuit 209, and the control device 16 opens the shield breaker 3 with the opening command 210a, thereby disconnecting the braking resistor 4 from the system. Through the above-described actions, the transient stability of the first wave of phase difference angle fluctuations caused by the occurrence of a failure in the power system 1 is ensured.

Next, even after the transient stability of the first wave of phase difference angle fluctuation is ensured, frequency fluctuation remains in the system, but in this configuration, the rotation speed change Δω of the representative generator 9 in the system is detected. Therefore, even after the second wave, this increase in rotation speed that approximately approximates the grid frequency is the set value.
If Kω is greater than ₁ , the output signal of the starting circuit 201 is held for a certain period of time, so the AND circuit 20
6 is activated again and the braking resistor 4 is reincorporated into the system. After that, when the rotation speed decreases and the change Δω becomes less than the set value Kω ₂ , the AND circuit 210
is activated, and the braking resistor 4 is disconnected from the system again. Thereafter, the rotational speed change Δω of the turbine generator 9
The closing/opening control of the braking resistor 4 is repeated many times in the same way until the value Kω1 becomes less than the set value _Kω1 .
The frequency fluctuations after the second wave are forcibly converged. Incidentally, FIG. 4 shows the relationship between the frequency fluctuation Δω and the period during which the braking resistor 4 is incorporated.

As mentioned above, the starting circuit 201 is based on the detection of the rotational speed change Δω of the representative generator 9 in the system.
This provides the necessary conditions for starting a series of closing and opening controls for the braking resistor 4. That is, starting circuit 2
As long as there is no output from 01, the closing/opening control of the braking resistor 4 will not be performed, no matter how the frequency of the bus 2 voltage changes.

In this way, when a serious failure that threatens the stability of the power system 1 occurs, the braking resistor 4 is repeatedly connected to and released from the system in accordance with the rotational speed fluctuation Δω of the representative generator 9 in the system. This is what I decided to do.

Therefore, the following effects can be obtained.

(a) The braking resistor 4 is applied to the power system upon detection of a serious failure occurring in the power system 1, which prevents the generator from accelerating out of synch and suppresses the first wave of phase difference angle oscillation. Transient stability can be improved.

(b) Since the braking resistor 4 is repeatedly controlled to be connected to and released from the system in accordance with the rotational speed change Δω of the representative generator 9, which approximates the change in the frequency of the system, the phase difference angle fluctuation is reduced. After securing the transient stability of the first wave, it is possible to forcibly converge the system frequency fluctuations from the second wave onwards at an early stage.

(c) Detect the rotational speed change Δω of a typical generator 9 and compare it with the set value, and the result (binary signal)
Since only the rotation speed is transmitted to the control device 16, there are no problems such as transmission and reception of a large amount of information or a decrease in reliability due to noise contamination, which is the case when continuous signals of rotational speed changes are transmitted as they are. It is extremely reliable.

Next, another embodiment of the present invention will be described with reference to FIGS. 5 and 6. Note that the same parts as in FIGS. 1 and 3 are given the same reference numerals, and their explanations will be omitted.

In other words, first connect the edges and disconnectors in Figure 5 to 3-1, 3-
2. The braking resistor is divided into two parts 4-1 and 4-2 and installed on the bus bar 2, and the divided braking resistor 3- 1 and 3-2 are constructed so that closing/opening control can be performed independently.

Further, FIG. 6 shows an example of the configuration of the control device 16 in FIG. 5, and a portion B surrounded by a dotted line is different from that in FIG. 3. Further, 206a-1 and 210a-1 in the portion A surrounded by the dotted line correspond to 206a and 210a in FIG. 3, respectively. That is, in addition to the functions of the control device 16 shown in FIG. 3, it constitutes a function of generating another closing command 206a-2 and opening command 210a-2. This is done by issuing the closing command 206a-2 on condition that there is an output from the comparator 203, and at the same time starting the on-delay timer circuit 211, and after the set time of the on-delay timer circuit 211 has elapsed from the closing point, the opening command 210a-2 is issued. 2. Further, in this case, the closing/opening commands 206a-1, 210a-1 indicated by the dotted line A are output to the output signal 16a-1 of the control device 16 in FIG.
-1 to close/release the dotted line part B to close/release command 2
06a-2 and 210a-2 are the same output signal 16
As a-2, the shingle breaker 3-2 is turned on and off.

That is, in this embodiment, when applying the braking resistor when a system failure occurs, the braking resistor is set to 4-1, 4-2.
The schedule control is such that one side is turned on when the start condition is satisfied (that is, there is an output from the comparator 203) and opened after a certain period of time, and the other side is set as a representative In response to the change Δω in the rotational speed of the target generator 9,
The feature is that the opening is repeatedly controlled.

Therefore, according to this embodiment, full capacity braking resistors 4-1 and 4-2 are applied to ensure the transient stability of the first wave of phase difference angle fluctuation, but the system frequency of the subsequent second wave is When converging the oscillation, it becomes possible to apply the braking resistor 4-1 with a certain capacity. In other words, this method is extremely convenient when the full capacity of the braking resistor is not necessarily required for convergence of system frequency fluctuations.

Note that the present invention is not limited to the above-described embodiments.

(1) As a physical quantity to determine the magnitude of a system failure,
The voltage drop amount ΔV of the bus 2 may be introduced instead of the line active power change ΔP. In other words, in this case, the current transformer 5 and power converter 7 in FIG. 1 or FIG. do it.

(2) Instead of the above configuration as the condition for the starting circuit, it may be configured such that the output of the accident detection relay on the main trunk line is directly introduced as the condition.

(3) In the second embodiment above, the braking resistor is installed in two parts, one of which is opened after a certain period of time after being turned on, and the other of which is used to change the rotation speed of the rotating machine operated within the power system. The capacity of the braking resistor incorporated into the system can be varied by repeatedly performing closing/opening control according to the situation. A second seam disconnector is installed so that a tap can be taken out from the container and a part of it can be shorted, and each seam disconnector is connected to the first.
The capacitance of the braking resistor incorporated into the system may be varied by controlling it in accordance with the application to the wave, second wave, and subsequent waves.

(4) If there are a plurality of generators whose rotational speed is detected, and an AND condition of the signals from the plurality of generators is introduced for the rotational speed signal 14a, which is the input of the control device 16, it is possible to detect the rotational speed of a single generator. It is possible to prevent erroneous control of the braking resistance when relying only on the rotational speed signal.

Effects of the Invention As explained above, according to the present invention, it is possible to improve the transient stability of the first wave of phase difference angle fluctuations in response to a serious power system failure, and to converge the frequency fluctuations of the power system from the second wave onward very quickly. A highly reliable braking resistor control method can be provided.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a block diagram showing the configuration of the measuring device in FIG. 1, FIGS. 3a and 3b are block diagrams showing the configuration of the control device in FIG. 1, and FIG. FIGS. 5 and 6 are configuration diagrams showing other embodiments of the present invention. 1... Power system, 2... Bus bar, 3, 3-1, 3
-2...Shield disconnector, 4, 4-1, 4-2...Braking resistor, 5...Current transformer, 6...Transformer, 7...Power converter, 9...Turbine generator , 10...Gear, 11...Electromagnetic pickup, 12...Measuring device, 13...Transmitter, 14...Receiver, 16...
Control device, 102...Pulse transmitter, 103...
Ripple removal circuit, 104, 202... Incomplete differentiation circuit, 105, 107... Comparator, 204, 2
09...Hold circuit, 206, 210...AND circuit, 211...On-delay timer circuit.

Claims (1)

[Scope of Claims] 1. In an apparatus for detecting the occurrence of a serious failure that threatens the stability of an electric power system and injecting a braking resistor into the electric power system to ensure the stability of the electric power system, the power system means for detecting the rotational speed of a rotating machine operated within the rotating machine; means for comparing the rotational speed detected by the means with a set value; and means for transmitting the comparison result as binary information; A control method for a braking resistor, comprising means for detecting a serious failure occurring in the electric power system, and controlling closing and opening of the braking resistor in response to fluctuations in the rotational speed of the rotating machine. 2. When a major failure occurs in the power system that threatens its stability, a braking resistor is inserted into the power system to ensure the stability of the power system, and when a rotating machine operated in the power system is means for detecting the rotational speed; and means for comparing the rotational speed detected by the means with a set value;
means for transmitting the comparison result as binary information;
and means for detecting a serious failure that has occurred in the power system, and is characterized in that the braking resistor is controlled to close and open while varying the braking resistor capacity in accordance with fluctuations in the rotational speed of the rotating machine. Braking resistor control method. 3 The braking resistor was installed in two parts, one of which was controlled to open after a certain period of time had passed after closing, and the other to be controlled to close and open according to fluctuations in the frequency of the power system. A braking resistor control method according to claim 2.