JPS6031173B2 - Power system stabilizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emergency power interchange device including an AC/DC converter, and particularly to a power system stabilization device that is designed to automatically restore power after emergency interchange due to an accident.

For power interchange between different frequency AC transmission systems, for example,
As shown in the figure, two AC power transmission systems A and B are interconnected by an AC/DC converter D consisting of forward and inverse converters.

By the way, in such a system, for example, when a power outage accident occurs in system A and the frequency of system A decreases, power is quickly transferred to system B via AC/DC converter D, which can rapidly exchange power. Power is sent from the power grid to the A system, and until the frequency adjustment power plant C of the A system, which has a time delay in operation, generates power to compensate for the power failure, the B
By sharing the power with the grid, we prevent the frequency of the A system from dropping and prevent the spread of accidents. Eventually, when the frequency adjustment power plant C starts operating, in consideration of the generated power,
The support power is reduced, and finally, the interchange power from the AC/DC converter D is returned to the value before the accident occurred. By the way, as an emergency support system using such an AC/DC converter, for example, the frequency of the fault system is detected, and when the frequency drops below a certain set value, the AC/DC converter is controlled to rapidly increase the interchange power in steps. A constant frequency deviation method, a frequency ratio control method that detects the frequency ratio of both AC systems and controls the interchange power, and the like have been proposed. However, with the constant frequency deviation method, after emergency support, the AC/DC converter's interchangeable power must be manually returned to the setting value before the accident, which does not allow smooth adjustment and may cause disturbances to the accident system again. This has the drawback of not only delaying frequency recovery but also causing frequency disturbance. In order to prevent this, a method shown in FIG. 2 has been proposed. Next, an automatic restoration method for subordinates will be explained using FIG. FIG. 2 explains the method of power interchange from the B system using the constant frequency deviation method and the automatic recovery method when the frequency of the A system drops due to an accident in the A system. Therefore, it is assumed that the method of power interchange from system A and the method of automatic restoration in response to an accident in system B include a device similar to that shown in FIG. 2. In Figure 2, a power failure accident occurred in the A system, and △Px in the diagram as shown in Figure 3 a.
Assuming that the supplied power is reduced by , the frequency of the A system decreases in accordance with the dropout amount ΔPx, as shown in FIG. 3b. After that, in Fig. 2, when the frequency N^ of the accident system drops below the frequency R^ that specifies the start of emergency power interchange, comparator CI operates and contacts CIA are closed.
The control amount of electricity △ is applied to the setting circuit Go of the AC/DC converter D in Fig. 1.
Pd, and as shown in FIG. 3(d), the accommodating power of the AC/DC converter ○ is increased stepwise by ΔPd, thereby providing emergency power accommodating power to the A system. At the same time, the contact CIB is closed, and the comparator CI is self-held so that the comparator C2 for detecting the arrival of the automatic recovery designated frequency is operable. Due to the effects of the emergency fin power accommodation and the increase in the regulating power plant output shown in FIG. 3c, the frequency of the A system returns toward the rated value as shown in FIG. 3b.
Then, when the frequency returns to the frequency Na^s that specifies the start of automatic recovery, comparator C2 operates and self-holds, closing contact C2A, and at a reduction rate determined from the transfer function of the fault system, etc. The control electrical quantity Kd is sent to the integrator 1/S so as to reduce the interchangeable power of the AC/DC converter. The output △P of the integrator 1/S is set by the setting circuit Go of the AC/DC converter D.
The emergency interchange power of the AC/DC converter is sent to t in Figure 3 d.
, Jiirochina^: Decrease from the point of Na^s. Then, the comparator C3 compares △Pd2 and the above-mentioned △Pd, and operates when the interchange power of the AC/DC converter D returns to the set value before the emergency interchange, and the comparator C1 , C2 and C3, contacts CIA, CIB and C2
Return A to the state before emergency accommodation. By the way, the rate of decrease in interchangeable power during automatic restoration is the controlled power amount K. The value of KD can be determined as follows. The factors that restore the frequency of the faulty system are the amount of emergency interchange power and the increase in the output of the regulating power plant, and the factor that prevents the restoration of the frequency is the decrease in interchange power. Therefore, the value of Ko may be determined in such a way that the effects of the factors that restore the frequency of the fault system overcome the factors that hinder restoration. In the above, we have described the case where the interchange power is reduced when the frequency of the faulty grid exceeds the specified value ``^s,'' but since the time required for automatic recovery can be predicted from the grid transmission characteristics etc., for example, There is also a method of using a time-limited relay to start automatic recovery operation after the above-mentioned predicted time after implementing emergency interchange.In addition, as a condition for emergency interchange, it is necessary to monitor not only the frequency drop of the faulty system but also the frequency of the healthy system. One of the conditions is that the system is in good condition and is healthy, and it also takes into account that the frequency difference between the healthy system and the faulty system exceeds a certain value as a condition for emergency accommodation. There are some things.
However, with conventional automatic restoration methods, it is necessary to correct the rate of decrease in emergency power interchange in response to increases in system capacity and changes in system transmission characteristics, but this cannot be done automatically. Not only is it not possible, but the automatic recovery starting point cannot be changed automatically. In other words, the reduction rate of emergency power interchange and the automatic recovery opening point must be manually changed depending on the changes in the grid, so even if automatic changes are made, the equipment for automatic changes will be complicated. is inconvenient.
In addition, since the reduction rate of the emergency power interchange amount is set to a certain value after the automatic restoration starts, the emergency power interchange amount will always be returned to zero. If an increase in output becomes impossible due to a problem, it is dangerous for the frequency of the fault system to drop again. The present invention has been developed in view of this current situation, and even if the system capacity increases, even if the system transmission characteristics change, or even if the size or location of the accident changes, it will still be possible to set the amount of emergency power interchange. Even if there is a problem with the power plant for change or adjustment, the emergency system will be automatically and The purpose is to obtain a power system stabilization device that restores power interchange.

A block diagram showing one embodiment of the present invention is shown in FIG.

In FIG. 4, Na^, NaR^, Na^s, △Pd. ,△
Pd2, CI, CIA, CIB, C3, G〇 are the same as those in Figure 2, and AI is the difference between the frequency of the fault system and the frequency that specifies automatic restoration after emergency power interchange. is detected, and the frequency of the accident system becomes the specified frequency〆^
This is a function generator that outputs an output when the value becomes larger than s, and the details are shown in FIG. The operation will be explained based on FIGS. 4, 5, and 6. In Fig. 4, if a power supply failure occurs in the A system and the supplied power decreases by △Px in the figure as shown in Fig. 5 a, then the frequency of the A system decreases as shown in Fig. 5 b.
decreases according to the falling amount ΔPx. After that, when the frequency of the accident system in Fig. 4 drops below the frequency 〆R^ that specifies the start of emergency power interchange, the comparator CI operates to close the contact CIA, and the control electric nose is connected to the setting circuit Go of the AC/DC converter D. ΔPd, and as shown in FIG. 5d, the interchange power of the AC/DC converter D is increased stepwise by ΔPd, thereby providing emergency power accommodation to the A system. At the same time, contact CIB also closes and self-holds outside the comparator. Due to the effects of the emergency power interchange and the increase in the output of the regulating power plant as shown in Figure 5c, the frequency of the A system returns toward the rated value, as shown in Figure 5b. When the frequency returns to the frequency ^s that specifies the start of automatic recovery, the function generator AI starts outputting △Pd2, and as shown in Figure 5e, in response to the return of the frequency 〆^ of the A system, The controlled quantity of electricity △Pd2 is made to change. That is, the frequency for specifying the start of automatic restoration is 〆^s, the amount of control electricity corresponding to the emergency power interchange amount △Pd is △Pd, and the frequency na^ of system A is the frequency na^.
If the emergency power interchange amount △Pd is automatically restored to zero when it is restored to P, then after the emergency power interchange, 〆^
When S na^s △Pd2=0> 1 [1'〆^=
When 〆^P, the function generator AI should be configured so that △Pd2=△Pd, 1 [21.

That is, as shown in FIG. 6, which shows the characteristics of the function generator AI, when the frequency na^ of the A system is lower than the frequency 〆^s, △P ground.
, the function generator AI may be configured so that the forehead slope Q=〆＾tei≧etc^S·{3'. By doing so, A
As the frequency N^ of the system returns toward the rated frequency 〆^o, the output △Pd2 of the function generator AI approaches the controlled electricity quantity △Pd, and the frequency N^ returns to the frequency 〆^P. , when the output △Pd2 of AI becomes equal to the controlled electricity amount △Pd, that is, the interchangeable power of the AC/DC converter D becomes,
When the setting value returns to the value before the emergency accommodation, comparator C3 operates and comparator CI and contacts CIA and CI of CI
Return B to the state before the emergency accommodation. It goes without saying that one of the conditions for emergency accommodation is that the frequency of the healthy system is being monitored and is healthy, rather than the frequency drop of the faulty system. Furthermore, as a condition for emergency accommodation, the fact that the frequency difference between the healthy system and the faulty system exceeds a certain value may be taken into consideration. The above has been described in the case of an accident in the A system, but the same equipment as shown in Figure 4 may be provided for an accident in the B system, and emergency power interchange and automatic restoration from the A system to the B system may be provided. The four functions of emergency power interchange from the B system to the A system and automatic restoration may be performed by one device. As described above, if the automatic recovery method of the present invention is used, even if the system capacity increases, even if the system transmission characteristics change, the size or location of the accident changes, or even if the power plant for adjustment Even if frequency correction is delayed or impossible due to trouble, the emergency power interchange amount will be automatically restored in response to the return of the frequency of the faulty system in a manner that does not cause disturbance to the frequency of the faulty system. This can be easily achieved. 0 The present invention is not limited to the above-mentioned embodiments, but may be modified as follows.

In FIG. 6, the force increase characteristic of the function generator AI in FIG. 4 is shown to have a linear relationship with the frequency N^, but it may also be in a quadratic form, as shown in FIG. 7, for example.

In other words, as the frequency of the accident system A exceeds the automatic recovery start frequency and is restored, the slope Q may be made steeper so that the emergency power interchange amount is earlier reduced to a smaller value. 'o}
When the setting of the emergency power accommodating amount is changed, or when the emergency power accommodating amount changes depending on the state of the accident, the characteristics of the function generator AI shown in FIG. 4 may be changed.

However, depending on the case of the accident, f^s in Figure 6
, f^P change, it is sufficient to change the characteristics of the function generator AI shown in FIG. 4.

By automatically reducing the amount of emergency power interchange only for those children who have responded to the restoration of frequency 〆^ of accident system A, the amount of emergency power accommodating is finally returned to zero so as not to cause disturbance of frequency 〆^. Then, it is possible to return the interchangeable power supply of the AC/DC converter D shown in FIG. 1 to the setting value before the emergency interchange, in preparation for a subsequent grid failure.

Furthermore, if the start-up of the regulating power plant is delayed after emergency power interchange, or if it becomes impossible to start up due to an inopportune situation, the recovery of the frequency of the faulty system will be delayed, but the effect of emergency power interchange will continue to be maintained. By doing so, it is possible to continue to promote the recovery of the frequency of the accident system.

[Brief explanation of the drawing]

Figure 1 is a power system diagram, Figure 2 is a diagram showing the conventional emergency interchange power restoration method, Figure 3 is a diagram explaining the operation of the subordinate emergency interchange power restoration method, and Figure 4 is The emergency interchange power restoration method of the present invention, FIG. 5 is a diagram for explaining the operation of the emergency interchange power recovery method of the present invention, FIG. 6 is a characteristic diagram of the function generator AI of the present invention, and FIG. is the function generator A of the present invention
It is a characteristic diagram of a modified example of I. A, B... Power system, C... Frequency adjustment power plant, D... AC/DC converter, C1, C2
, C3...1 comparator, CIA, CIB,...
...CI contact, C2A--C2 contact, Ki--
---Integrator, KD... Decrease rate, Go...
... Setting circuit of D, N^... Actual frequency of A,
NaR^...Specifies the start of emergency power interchange, frequency of A, Na^s...Specifies the start of automatic recovery,
A frequency, △Pd. , △Pd2... Controlled electricity amount, △P
x...Power supply dropout amount, △Pd...Emergency power interchange amount, AI...Function generator, Q...
・AI gain, f^o... Rated frequency of A. Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1 In a system where two AC systems are interconnected using an AC/DC converter, and when an accident such as a power outage occurs in one system, power is transferred from the healthy system through the AC/DC converter. From the moment the frequency of the fault system recovers to the specified frequency that starts automatic restoration of emergency interchange power, a control signal is sent to the AC/DC converter according to the difference between the actual frequency of the fault system and the specified frequency that starts automatic restoration. A power system stabilizing device characterized in that the power is applied to a setting circuit to automatically restore the interchangeable power of both systems to the set value before the accident.