JPH0261221B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a cooperative control system for an electric power system, and particularly to a method for coordinating a nuclear power plant and a DC system when converting nuclear energy to electric power and transmitting electricity only by direct current. The present invention relates to a cooperative control system for power systems suitable for safely protecting nuclear power plants by taking the following measures.

[Prior art]

In response to the increasing demand for electricity, power systems are being expanded and strengthened, while power sources are becoming more remote and large-scale.
As grid operation becomes more complex, various problems are arising, including constraints on the location environment. In order to deal with these power system problems, a nuclear power plant is installed at a location far from the power demand area, and at this nuclear power plant, nuclear energy is exchanged into electricity, which is then converted to direct current and generated via power transmission lines. There is a method of operating a power system that has a configuration in which a DC system is installed that transmits power to a demand point, converts it back to AC power on the power receiving side, and supplies it to the AC system at the demand point, and controls this system using a control system. It is considered.

It goes without saying that the power system described above is configured to provide sufficient protection against accidents in nuclear power plants, DC systems, and AC systems in power demand areas. For example, even if an accident occurs in an AC system in a power demand area, nuclear power plants are now being scrammed. By the way, in the case of an accident in an AC system at a power demand point, the AC system control protection device can usually eliminate the accident within the main protection operation time (50 [mS] to 100 [mS]). However, the above power system is designed so that nuclear power plants are scrammed even in the event of such an instantaneous accident. however,
Considering the public nature of electricity, it is undesirable for nuclear power plants to be scrammed even in the event of such an instantaneous accident in the AC system.

[Purpose of the invention]

The present invention has been made in view of the above problems, and
The purpose is to provide a cooperative control system for power systems that allows stable operation of nuclear power plants.

[Summary of the invention]

In order to achieve the above object, the present invention coordinates the main protection operation time of the AC system against accidents in the AC system in power demand areas, and scrams the nuclear power plant only in the event of an accident that lasts for a certain period of time or longer. This is how it was done.

[Embodiments of the invention]

FIG. 1 is a system diagram showing an electric power system in which nuclear energy is converted into electric power and this is transmitted as direct current. To explain according to FIG. 1, 11 is the generator of the nuclear power plant 1, 21 to 24 are conversion transformers, 31 and 32 are AC/DC converters that convert AC to DC, and 33 and 34 are DC to AC converters. AC/DC converters 41 and 44 are AC/DC converters 31 to 34
A bypass switch that bypasses the DC side of the circuit (this can be anything that can be bypassed, and may be a bypass pair that bypasses by turning on the positive and negative arms of one phase of a three-phase bridge). ), 51 to 54 are DC reactors that smooth the current of the DC circuit, 61 to 64 are DC transmission lines, 71 and 72 are receiving power sources of AC system 2, 8
1 and 82 are reactive power compensators that compensate for reactive power for stable operation of the AC/DC converters 31 to 34;
90 is the generator 11 and DC system 3 of the nuclear power plant 1
91 is a control and protection device for the nuclear power generator, 92 and 93 are terminal control devices for the DC system 3, and 101 is for detecting the magnitude and rate of increase/decrease of the output current of the generator. This is a current detector for.

Therefore, the power system is configured as follows by each of the above-mentioned elements.

That is, the electric travel system includes a nuclear power plant 1 including a generator 11, and AC power outputted from the generator 11 of the power plant 1, which is boosted by transformers 21 and 22 and then converted by AC/DC converters 31 and 32. The direct current is converted to direct current, transmitted to the power demand point via the power transmission lines 61 to 64 including the direct current reactors 51 to 54, and converted back to alternating current by the AC/DC converters 33 and 34 installed at that point, and then DC system 3 that supplies AC system 2 in the power demand area including 71 and 72
and a control system 4 that receives a signal from a current detector 101 that detects the current output from the generator 11, and controls and protects the nuclear power plant and the DC system based on predetermined operation commands. There is.

More specifically, the control system 4 includes a central control device 90, a control protection device 91, and DC terminal control devices 92 and 93. still,
Although not shown, in each AC system and DC system 3,
A control protection device is provided for each, and these control and protection devices control and protect the devices.

In order to operate such an electric power system stably, a coordinated operation is performed in which the output of the generator 11 and the transmitted power of the DC system 3 are combined at all times. However, if we consider the case where a ground fault occurs in the AC system 2 on the power receiving side, for example at point F in the figure, if the AC voltage in the normal DC system 3 drops to 50% or less, the converter 3
The DC side of the converters 33 and 34 is connected to the bypass switch 43 because the commutation operation of the converters 3 and 34 cannot be performed satisfactorily or because the voltage applied to the converters 33 and 34 becomes unknown in the event of an accident in the AC system 2.
and 44 or shorted by a bypass pair. Therefore, the DC voltage becomes close to zero voltage, and the reactive power required by the AC/DC converters 31 and 32 at the power transmission end increases.

Accidents in AC system 2 occur between 50 [mS] and 100 [mS].
Therefore, the converters 31 and 32 are not stopped. Therefore, constant current control operation is being carried out at the transmission end as before the accident. In this case, if the compensation capacity of the reactive power compensator 81 at the transmission end is small, the shortage of reactive power required by the converters 31 and 32 will be obtained from the nuclear power generator 11, but if the compensation capacity is large, it will be necessary. Most of the reactive power will be received from the reactive power compensator, and the output current of the generator will be small.

FIG. 2 is a time chart shown to explain the above-mentioned operation. In FIG. 2, the horizontal axis shows time t, and the vertical axis shows waveforms at various parts. In the figure, an AC accident occurs at time t ₁ , and
This shows the case where the fault is removed at t ₂ , and in the waveform of the output current Ig from the generator 11, the solid line shows the case where the capacity of the reactive power compensator 81 is large, and the broken line shows the case where the capacity is small.

In order to protect the nuclear power plant 1 from such accidents, the generator 11 of the nuclear power plant 1 has a power load unbalance relay (hereinafter referred to as
(simply referred to as PLU-Ry).

The operation of this PLU-Ry will be explained with reference to the logic diagram shown in FIG. PLU-Ry200 is
Output setting value I _P of generator 11 and magnitude of output current I _g
Conditions where the difference exceeds 60% (｜I _P −I _g ｜>60%)
The signal S ₁ emitted by the generator 11 and the condition that the temporal change in the output current of the generator 11 exceeds a certain value (|I _g /dt>a),
For example, the AND circuit 201 performs an AND operation with the signal S ₂ emitted under the condition of 40 [%]/10 [mS], outputs the protection signal S _S , and uses this signal to scram the nuclear power plant. Make it. However, in the case of the above-mentioned AC system 2 accident, the control protection device (not shown) of the AC system 2 normally causes a
Since the accident can be eliminated within [mS], it is not desirable for PLU-Ry to operate at this time. However, if the capacity of the reactive power compensator 81 is large, it may work. On the other hand, if the capacity of the reactive power compensator 81 is small, the PLU-Ry will not operate immediately after an accident occurs, but the protection (main protection) by the control protection device (not shown) of the AC system 2 will fail. However, if the fault cannot be removed, the entire DC system 3 will be stopped. As a result, in this case, the PLU-Ry malfunctions and the nuclear power plant cannot be protected by the PLU-Ry. In this case, the mechanical system of the nuclear power generator 11 is protected.

The present invention has been devised to prevent such malfunctions of the PLU-Ry, and will be described below with reference to FIG. 4 and the subsequent drawings.

FIG. 4 is a circuit diagram showing an embodiment of a control system used in the power system cooperative control system according to the present invention. FIG. 4 shows how to prevent malfunction of the power load unbalance relay 200 in the event of an accident in the AC system 2.
The protection signal S _S from the AND circuit ₂₀₁ of the power load unbalance relay shown in _FIG . A protection circuit 300 that locks the protection signal S _S for a time period T ₁ as long as T ₁ and outputs a signal when the signal S ₁ is present even after the elapse of the time period T 1 and a temporal transformation element of the current of the generator 11 . Protection circuit 301 that holds signal _S2
is added.

Further, referring to FIG. 4, 200 is a power load unbalance relay, 302 is a timer with a timer time _T1 for locking the output of the AND circuit 201, and 303 is a timer for detecting temporal changes in the nuclear power generator current. A timer 305 has a timer time T ₂ to reset the flip-flop 304 for detecting and holding the element signal S ₂ . 305 is the output of the timer 302 and the power generation which is another element of the power load unbalance relay. A signal where the difference between the machine output command and the generator current exceeds the specified value
An AND circuit 306 which takes the AND of _S1 and the output of the AND circuit 305 and the flip-flop 3
This is an AND circuit that performs AND with 04. The protection circuit 300 includes a timer 302 and an AND circuit 305. Furthermore, the protection circuit 301 is composed of a timer 303 and a flip-flop 304.

The operation of the embodiment configured as described above will be explained with reference to the time chart shown in FIG. FIG. 5 is a diagram showing the operation shown in FIG. 4 in the same accident as shown in FIG. 2. Therefore, the horizontal axis shows time t, and the vertical axis shows the waveform of each part.

When an accident occurs in the receiving AC system 2 at time t ₁ , the output current I _g of the generator 11 decreases, and at time t ₀
The AND condition of PLU-Ry 200 is satisfied and the protection signal S ₀ is output. This output causes timer 30
2 and 303 operate, and timer 302 starts after T ₁ .
The timer 303 returns to its state (returns to its original state) after _T2 . FIG. 5 shows the output waveforms of timer 302 and flip-flop 304 in the above state. Here, if the time limit T ₁ is set to be longer than the main protection operation time T ₀ (e.g. 80 [mS]) of the AC system 2, after T ₁ , if the main protection of the AC system 2 has been successful, the power will be generated. The output current I _g of the generator 11 is close to the generator output command I _p , and the AND circuit 3
Since signal 05 does not satisfy the conditions, no output signal is output.

On the other hand, the time limit _T2 is set to be larger than the time limit _T1 , but since the output signal of the AND circuit 305 is not output after the elapse of the time limit _T1 , the AND circuit 306 is also not output, and the signal is not output as described in the explanation of FIG. No inconvenience will occur. Furthermore, if the main protection of the AC system 2 is unsuccessful, with the timer 302 restored,
Since signal S ₁ is “1”, AND circuit 3
An output signal is output from 05, and an AND condition with the output signal from flip-flop 304 is formed in AND circuit 306, so that a protection signal S _SH is output, and the scram of nuclear power plant 1 can be ensured.

In addition, although the case where the reactive power compensation capacity 81 is large is explained above, if this is small, the PLU-
Ry200 will never work, so there is no problem. Therefore, unnecessary scramming of nuclear power due to malfunction of PLU-Ry 200 can be prevented.

FIG. 6 is a block diagram showing another embodiment of the invention. In this embodiment, in order to prevent the power load unbalance relay from malfunctioning when the main protection operation of the AC system 2 fails, a signal from the block of the entire DC system 2 is added to the circuit shown in FIG. It was added. To explain only what is different from FIG. 4, reference numeral 307 is an OR circuit that ORs the protection signal output of the circuit of FIG. 4 and the DC system block signal.

The operation of the embodiment configured in this way is to output a protection signal when there is either the output signal of the AND circuit 306 or the DC entire system block signal S _B. FIG. 7 shows the operation of this circuit when the main protection of the AC system 2 fails in the same accident as shown in FIG. 2. At t ₀ , the protection signal S _S is output from the AND circuit 201, and the timers 302 and 303
works. The state is restored after the time limit T ₁ and time limit T ₂ respectively, but if the reactive power compensation capacity 81 of the AC system 2 is small, the AND circuit 305 does not output an output, so the AND circuit 306 cannot obtain an output. If the system remains as it is in Figure 4, it will malfunction, but by adding the OR circuit 307, the output scram signal S ₀ can be obtained at time t ₃ when the DC all-system block signal (stop signal) S _B is issued. Nuclear power plant 1 can be protected as a scram. Note that when the reactive power compensation capacity is large, the AND circuits 305 and 306 operate when _T1 has passed from _t0 , so the OR circuit 30
The scram signal S ₀ is output from 7, and there is no problem.

As described above, the above embodiment can prevent malfunctions and malfunctions of the power load unbalance relay 200 for nuclear power protection, so the system can be made highly reliable.

〔Effect of the invention〕

As described above, according to the present invention, since the nuclear power plant and the DC system are coordinated, there is an effect that the nuclear power plant can be operated stably.

[Brief explanation of drawings]

Figure 1 is a system diagram showing the entire power system that is the object of the present invention, Figure 2 is a time chart showing operating waveforms at the time of an AC power failure on the receiving side, and Figure 3 is the principle configuration of the power load unbalance relay. FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. 5 is a circuit diagram showing an embodiment of the present invention.
The figure is a time chart showing operation waveforms when the embodiment shown in Fig. 4 is applied to a power system, Fig. 6 is a circuit diagram showing another embodiment of the present invention, and Fig. 7 is an implementation example shown in Fig. 6. It is a time chart showing operation waveforms when the example is applied to a power system. 11... Nuclear power generator, 31 to 34... AC/DC converter, 200... Power load unbalance relay, 300 and 301... Protection circuit.

Claims (1)

[Scope of Claims] 1. An electronic power plant that converts nuclear energy into electric power, converts the electric power into DC, transmits it via a power transmission line, and converts it back to AC on the receiving side to create an AC system. In an electric power system having a DC system that supplies the nuclear power plant and a control system that controls and protects the nuclear power plant and the DC system, the control system is configured such that the difference between the power generation output command and the current drawn from the nuclear power generator is a specified value. A power that outputs a protection signal under the logical product condition of a first signal that is emitted when the time rate of change of the current extracted from the nuclear power generator exceeds a predetermined value. The load unbalance relay and the protection signal from this power load unbalance relay are taken in, and the first
a first protection circuit that takes in a signal and locks the protection signal for a fixed time period _T1 , and outputs a signal when the first signal is present even after the elapse of the time period; and a second protection circuit that is maintained only for a time period _T2 , and scrams the nuclear power generator when signals are output from the first and second protection circuits after a certain time period _T1 has elapsed. A cooperative control method for power systems characterized by: 2. The power system cooperative control system according to claim 1, wherein the first protection circuit has a fixed period T ₁ equal to or longer than the main protection operation time T ₀ of the AC system. cooperative control method. 3. An electronic power plant that converts nuclear energy into electricity, a DC system that converts that electricity into DC, transmits it via power transmission lines, converts it back to AC on the receiving side, and supplies it to the AC system, In the electric power system having the nuclear power plant and a control system that controls and protects the DC system, the control system is configured to issue an alarm when the difference between the power generation output command and the current drawn from the nuclear power plant exceeds a specified value. a power load unbalance relay that outputs a protection signal under the AND condition of a first signal issued when the time rate of change of the current extracted from the nuclear power plant exceeds a predetermined value; In addition to taking in the protection signal from this power load unbalance relay,
a first protection circuit that takes in a signal and locks the protection signal for a fixed time period _T1 , and outputs a signal when the first signal is present even after the elapse of the time period; a second protection circuit that is held only for a time period _T2 , and a scram signal and the DC signal that are output when the signals from the first and second protection circuits are being output after a certain time period _T1 has elapsed. A power system cooperative control method characterized by taking the logical sum of block signals to protect the entire system and scramming the nuclear power generator depending on which signal is received.