JP2020005336A - System stabilization method and system stabilizer - Google Patents

Abstract

To provide a system stabilization method and a system stabilizer, which adjust power demand supply balance of an isolated system with simpler processing to stabilize the system when isolated system separation takes place without depending on an inner system state.SOLUTION: In a system stabilization method for maintaining an isolated system when isolated system separation takes place in a power system 1A being a control object having a plurality of power generators and a plurality of loads, a total power generation amount is suppressed if a tidal current amount is a positive value and a total load amount is reduced by interrupting a part of the load in a previously determined interruption order to stabilize the power system of the control object if the tidal current amount is a negative value in accordance with the tidal current amount of a cooperative line 2 before the isolated system separation takes place when a tidal current toward an another power system 1B side from a power system 1A side of the control object is defined to be positive, and the isolated system separation takes place and divergence between the total power generation amount by a plurality of power generators 3A to 3D and the total load amount by a plurality of loads 4A to 4E is equal to or more than setting divergence which is previously set.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technology for stabilizing a power system to be controlled, which has become a single system, when the power system to be controlled becomes a single separated system due to external disturbance. The present invention is a technology that is particularly effective when the load of the power system to be controlled is a factory load.

As a technique for stabilizing the power system, there is a technique described in Patent Document 1, for example.
The system stabilization method described in Patent Literature 1 distinguishes a plurality of presumed accident cases of a single isolated system accident set in advance when a trouble occurs on the system, and performs load shedding according to the determined assumed accident case. Send a signal.

JP 2011-217495 A

In the method of system stabilization described in Patent Literature 1, a breaking load is selected so as to minimize the influence on an accident assumed in advance. In this method, depending on the state of the internal system, as the power system to be controlled becomes larger, the number of assumed accidents becomes enormous, and it is impossible to cope with unexpected accidents.
The present invention has been made by paying attention to the above points, and when independent system separation occurs without depending on the internal system state, the simple system (simplified judgment) can be used. To stabilize the grid by adjusting the supply and demand balance of

  The inventor has studied means for easily stabilizing the system without depending on the internal system state when a system trouble occurs. Then, the inventor pays attention to the power flow of the interconnection line connected to the power system to be controlled, and when a trouble occurs in the system, determines the amount of adjustment of the generator or load from the direction and amount of the power flow. By calculating and restricting the generator or load to be controlled to a required amount, it has been found that the system can be easily stabilized without depending on the internal system state.

  In order to solve the problem, according to one embodiment of the present invention, a power system to be controlled having a plurality of generators and a plurality of loads is isolated from trouble in a state where the power system is connected to another power system by a connection line. A system stabilization method for maintaining a single system consisting of the power system to be controlled in the case of system separation, wherein a power flow from the power system to be controlled to the other power system is defined as positive. When the single system separation occurs and the difference between the total power generation amount by the plurality of generators and the total load amount by the plurality of loads is equal to or larger than a preset difference, the single system separation is performed. According to the tidal current of the interconnection line, if the tidal current is a positive value, the total power generation is suppressed.If the tidal current is a negative value, a part of the load is cut off in a predetermined interruption order. By shutting off, the total load is reduced, To stabilize the target of the power system.

  Further, in another aspect of the present invention, a power system to be controlled having a plurality of generators and a plurality of loads has been separated into a single system due to a trouble from a state in which the power system is connected to another power system by a connection line. A system stabilizing device that operates in the case where the power system to be controlled is a single system composed of the power system to be controlled, and a power flow from the power system to be controlled to the other power system is defined as positive. An adjustment determining unit that determines whether a difference between a current total power generation amount by the plurality of generators and a current total load amount by the plurality of loads is equal to or greater than a preset difference ratio; and the plurality of loads. On the other hand, a load fluctuation order setting unit that sets a priority order in which the load is to be interrupted is set in advance by setting a higher priority order as the load fluctuation is larger based on the actual results. Power generation and total load Is greater than or equal to the set deviation, and when the power flow of the interconnection line immediately before the single system separation is a negative value, the load amount corresponding to the power flow immediately before the single system separation becomes A load reduction unit that interrupts a load in an interruption order that is a load interruption order setting unit, and a divergence between the total power generation amount and the total load amount that is in the single system separation state and is equal to or greater than a set divergence rate, A power generation suppressing unit configured to suppress the total power generation amount and stabilize the power system to be controlled when the tidal current of the interconnection line immediately before the single system is separated is a positive value.

  According to the aspect of the present invention, it is possible to adjust supply-demand balance and maintain a single system by a simple process for an accident that separates the system without setting a response to an enormous accident assumed case for the power system in the control target. Will be able to Also, according to the aspect of the present invention, depending on the direction of the interconnection flow, not only the load limitation but also the adjustment of the generator can maintain the single system and minimize the operation influence. .

It is a figure showing the example of the electric power system concerning the embodiment based on the present invention. It is a figure explaining a system stabilization device concerning an embodiment based on the present invention. It is a figure explaining the example of processing of a system stabilization method. FIG. 9 is a diagram for explaining Example 1. FIG. 9 is a diagram for explaining Example 2. FIG. 9 is a diagram for explaining Example 3. FIG. 14 is a diagram for explaining Example 4.

Next, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the system stabilizing device 5 of the present embodiment is configured such that a power system 1A to be controlled having a plurality of generators 3A to 3D and a plurality of loads 4A to 4E is connected to another power system 1B. When a single system is separated due to a trouble from the state of connection at 2, a simple system stabilization process for maintaining a single system consisting of the power system 1A to be controlled is performed.
Here, in this specification, a power flow (reverse power flow) from the power system 1A to be controlled to the other power system 1B is defined as positive.

  The power system 1A to be controlled is, for example, a power system provided in a manufacturing plant such as a steel manufacturing plant, and the power system 1A is connected to the power system 1B of the power company by the interconnection line 2. Then, when there is a surplus power generation amount in the power system 1A to be controlled, the surplus power generation is transmitted to the power system 1B of the power company, and when the power generation amount shortage occurs in the power system 1A to be controlled. , The shortage of power is transmitted from the power system 1B of the power company.

In FIG. 1, reference numerals 10A to 10J indicate circuit breakers, and reference numerals 11A to 11J indicate sensors (instrument transformers).
Circuit breakers 10 </ b> A to 10 </ b> J are activated by a signal from system stabilizer 5. The sensors 11A to 11J execute measurement at a predetermined sampling cycle.
Whether or not the single system has been separated may be determined, for example, based on whether or not the interconnection line 2 has been interrupted.
In addition, since the tidal current does not fluctuate greatly in a short period of time, it is not necessary to be an instantaneous value even if the tidal current is just before the isolation of the single system. The tide can be adopted.

<Configuration>
As shown in FIG. 2, the system stabilization device 5 includes a load shedding order setting unit 5A, a system information input unit 5B, an adjustment amount calculation unit 5C, an adjustment determination unit 5D, and a stabilization processing unit 5E. .
The load shedding order setting section 5A presets a cutoff order, which is an order of interruption, for a plurality of loads 4A to 4E such that the larger the load fluctuation, the higher the priority based on the results. The load change may be obtained, for example, by a change in a long-term span such as the past three months or six months.

The system information input unit 5B, based on the measurement values of the sensors 11A to 11J provided in the power system 1A, based on the tidal current flowing in the interconnecting line 2, the power generation amount of each generator, the load amount of each load, the bus voltage, the frequency, etc. Is acquired and stored at a preset sampling period.
The adjustment amount calculation unit 5C calculates an adjustment amount for maintaining the single separated system from the history of the power flow acquired by the system information input unit 5B. The amount of adjustment is a power value corresponding to the power flow immediately before the power system 1A to be controlled becomes the isolated system. For example, the amount of adjustment is a power value equal to the power flow immediately before. A value obtained by multiplying a power value equal to the immediately preceding power flow by a predetermined correction coefficient may be used as the adjustment amount.

The adjustment determination unit 5D determines whether the difference between the total amount of power generated by the plurality of generators 3A to 3D and the total amount of load by the loads 4A to 4E provided in the power system 1A to be controlled is equal to or greater than a preset difference. Determine whether or not.
For example, the determination is made based on whether or not the deviation rate represented by the following equation is equal to or greater than a preset deviation rate. The set deviation rate is, for example, 10%.
Deviation rate = | (total power generation-total load) / total load | × 100

When the adjustment determining unit 5D determines that the difference between the total power generation amount and the total load amount is less than the set deviation, the system stabilization process ends. The set divergence sets a divergence value that is a power generation amount or a load amount within a surplus power that can be absorbed solely by the power system 1A to be controlled. For example, the value of the setting deviation is set so as to be in a range that can be absorbed by correcting the frequency deviation in the power system.
When the adjustment determining unit 5D determines that the difference between the total power generation amount and the total load amount is equal to or larger than the set difference, the process proceeds to the stabilization processing unit 5E.
The stabilization processing unit 5E includes a processing separation unit 5Ea, a load reduction processing unit 5Eb, and a power generation suppression processing unit 5Ec.

  When the processing separation unit 5Ea determines that the power flow is a negative value from the power flow direction based on the information acquired by the system stabilization device 5, the process separation unit 5Ea shifts to the load reduction processing unit 5Eb. When it is determined that the power flow is a positive value, the process proceeds to the power generation suppression processing unit 5Ec. Immediately after becoming a single isolated system due to a trouble, a negative value of the tidal current immediately before it is synonymous with that the total load is greater than the total power generation, and a positive value of the tidal current immediately before is a total power generation. Synonymous with quantity being greater than total load.

The load reduction processing unit 5Eb sequentially selects loads to be interrupted from the plurality of loads 4A to 4E according to the interruption order set in the load interruption order setting unit 5A so that the interruption load amount corresponds to the adjustment amount. And shut off the selected load.
The power generation suppression processing unit 5Ec suppresses the total power generation amount and stabilizes the power system 1A to be controlled when the single system is separated and the difference between the total power generation amount and the total load amount is equal to or greater than a set deviation rate. Aim.

An example of a series of processes in the adjustment amount calculation unit 5C, the adjustment determination unit 5D, and the stabilization processing unit 5E in the system stabilization device 5 will be described with reference to a flow illustrated in FIG.
If it is determined that a system trouble has occurred and the system has become an isolated system, the process of step S100 is started.
In step S100, an adjustment amount required for system stabilization is calculated from the tidal current of the interconnection line 2. In step S100, for example, the tidal current immediately before the interconnection line 2 is cut off and becomes a single separated system is set as the adjustment amount. The magnitude of this adjustment amount is synonymous with the difference between the total power generation amount and the total load amount when a single separated system is used.

In step S110, a total power generation amount and a total load amount when the single separated system is formed are calculated. Either step S100 or step S110 may be operated first, or the processing may be executed simultaneously.
In step S120, it is determined whether the divergence rate between the total power generation amount and the total load amount is equal to or greater than a set divergence rate (for example, 10%). If the divergence rate between the total power generation amount and the total load amount is equal to or greater than the set divergence rate (10%), the process proceeds to step S130. On the other hand, if the deviation rate is less than the set deviation rate (10%), the stabilization processing ends.

In step S130, the total power generation amount and the total load amount are compared, and if it is determined that the total power generation amount is larger, the process proceeds to step S160. On the other hand, when it is determined that the total load is larger, the process proceeds to step S140.
Here, immediately after the system separation, the determination as to whether the total power generation amount is larger than the total load amount is synonymous with the determination as to whether the direction of the power flow is a positive value or a negative value. That is, step S130 is a step of determining whether the tidal component is a positive value or a negative value. However, after the processing of steps S150 and S180, etc., the total number of steps and the total amount of power generation are updated, and the number of steps is optimized. This is a process of comparing with the load amount.

In step S140, the load to be interrupted is determined in the order of the interrupt priority set in the load interrupting order setting unit 5A so that the load is equal to or greater than the adjustment amount obtained in step S100, and the determined load is determined. And outputs a cutoff signal to the circuit breaker corresponding to. After that, it moves to step S150.
In step S140, for example, in the priority order set in the load shedding order setting unit 5A, subtraction of the load amount from the adjustment initial value equal to the above adjustment amount is performed. Repeat until over. Then, a cutoff signal is output to the circuit breaker of the load obtained by subtracting the load amount from the adjustment initial value.

In step S150, the load amount before the interruption of the load interrupted in step S140 is subtracted from the total load amount to update the total load amount. Thereafter, the process proceeds to step S120.
In order to cut off from a load having a relatively large fluctuation, the total load may be recalculated in step S150 by adding the load of the operating load other than the cut off load again.
The default value of the total load is the total load calculated in step S110.

On the other hand, when it is determined in step S130 that the total power generation amount is larger, the process proceeds to step S160. In step S160, if the ratio of the adjustment amount to the total load is less than a preset threshold value (for example, 0.2), the process proceeds to step S170. If the ratio of the adjustment amount to the total load amount is equal to or greater than a preset threshold, the process proceeds to step S190.
In step S160, the determination may be made based on whether the ratio of the adjustment amount to the total power generation amount is less than a preset threshold value (for example, 0.2).

In step S170, the adjustment amount is divided into the outputs of the plurality of operating generators, and signals for suppressing the outputs of the plurality of generators are output. After that, it moves to step S180.
In the above scheme, the amount of power generated by each generator may be reduced by the same amount by simply dividing the adjustment amount by the number of power generation units. Proportionation is preferable because fluctuation is suppressed to a small value. That is, it is preferable to set the suppression amount of each generator by weighting each power generation amount.
In step S180, after performing the update process of reducing the total power generation amount by the power generation amount suppressed in step S170, the process proceeds to step S120.

On the other hand, in step S190, the generator with the output close to the adjustment is selected by comparing the adjustment with the output of each generator. Then, a cutoff signal is output to the circuit breaker corresponding to the selected generator, and the process proceeds to step S200. In step S200, the total power generation amount is reduced by the power generation amount of the generator shut off in step S190, and after updating the total power generation amount, the process proceeds to step S120.
Here, step S100 corresponds to the adjustment amount calculation unit 5C, step S120 corresponds to the adjustment determination unit 5D, step S140 corresponds to the load reduction processing unit 5Eb, and steps S170 and S190 correspond to the power generation suppression processing unit 5Ec.

<Example of stabilization processing>
A processing example of the stabilization processing will be described with reference to FIGS.
4 to 7 show the power flow, the amount of power generated by each of the generators 3A to 3D, and the amount of load of each of the loads 4A to 4E.
Each example is an example in which there are four operating generators and five operating factory loads.
(Example 1)
Example 1 is a diagram for explaining a processing example in which the output of the generator is adjusted and stabilized as shown in FIG.
In Example 1, as shown in FIG. 4A, the total load, which is the total value of the plurality of factory loads, is 700 [MW], and the total power generation, which is the total value of the outputs of the plurality of generators 3A to 3D. Is 800 [MW], and 100 [MW] is set to the state of reverse power flow to the power company through the interconnection line 2.
If the interconnection line 2 is cut off in this state, a surplus of 100 [MW] is generated in the power generation amount. Example 1 is a case where it is determined that the ratio of the surplus to the total load is less than the predetermined threshold (0.2), and by the processing of step S170, as shown in FIG. This is an example in which the amount of power generation suppression is calculated such that the larger the output, the greater the output, in accordance with the output of 3D, and then the power generation is suppressed.

(Example 2)
Example 2 is also a diagram for explaining a processing example in which the output of the generator is adjusted and stabilized as shown in FIG. However, this is an example of a case where the power flow (adjustment amount) is larger than that of Example 1 (the processing in step S190), and is an example that involves shutting down the generator as stabilization by adjusting the generator.
Example 2 is a case where it is determined that the surplus of power generation is 200 [MW] due to being a single system due to a trouble, and the ratio of the surplus to the total load is 20% or more. This is an example in which a generator with an output close to the adjustment amount is shut off to achieve early stabilization. That is, in Example 2, since the ratio of the surplus to the total load due to the trouble is large, from the viewpoint of early supply-demand balance adjustment, power generation is suppressed by selecting and shutting down the target generator.
In this example 2, it is determined that the adjustment amount is equal to the output of the generator 3B, and the generator 3B is shut off (FIG. 5B).

(Example 3)
Example 3 is a diagram for explaining a processing example in which the load is adjusted and stabilized as shown in FIG.
Example 3 is a case where the output of each generator is low and the power generation amount is insufficient by 100 [MW] when the interconnection line 2 is cut off. In the third example, prioritization is performed in advance so as to limit the load from a load with a high load variation rate, and the load is interrupted from a load with a large variation.
Here, the numbers described at the bottom of FIG. 5 indicate the order of load shedding.
In the third example, the stabilization is achieved by interrupting the first load 4B (FIG. 6B).

(Example 4)
Example 4 is also a diagram for explaining a processing example of adjusting and stabilizing the load as shown in FIG. However, Example 4 is an example in which a surplus is generated in the power generation amount by limiting the load.
That is, this is a case where the loads 4B and 4C of the first and second ranks are cut off because the power generation amount is short of 150 [MW] when the interconnection line is cut off. In this case, as shown in Example 1, the generator is suppressed for the surplus of the power generation amount in the system capacity (full load amount) to be controlled after the load limitation (FIG. 7B). ).
In Example 4, after the loads 4B and 4C are cut off in Step S140, the total load is updated in Step S150, and it is determined that continuous stabilization processing is necessary in Step S120, and power generation is suppressed in Step S170. This is an example of performing.

<Action and others>
In the present embodiment, a system trouble occurs when the power system 1A to be controlled set in the manufacturing factory and the power system of the power company (the other power system 1B) are connected by the interconnection line 2. This is a system stabilization technique in a case where the interconnection line 2 is electrically disconnected and the power system 1A to be controlled becomes an isolated system. The other power system 1B connected to the power system 1A to be controlled by the interconnection line 2 may be a power system of another factory.

In the system stabilization technique according to the present embodiment, the adjustment amount is calculated from the interconnection flow just before the system trouble occurs (for example, 5 minutes before), and the control target is determined from the direction of the interconnection flow of the interconnection 2 immediately before. A restriction target is selected from the generators and factory loads existing in the power system 1A, and the control target power system is stabilized.
In other words, in the present embodiment, when a trouble occurs in the system, the stabilization is achieved without depending on the state of the internal system by focusing on the power flow of the interconnection line to be controlled.

  For example, when it is determined that the amount of power generation should be suppressed based on the interconnection flow due to the occurrence of a system trouble, that is, when the generator must be adjusted, if the amount of adjustment is small, the frequency deviation is small, so the control target Based on the number and output of generators connected to the system, the amount of suppression of each generator is calculated to stabilize the system. On the other hand, in the case where it is determined that the amount of power generation is suppressed from the interconnection flow and the amount of adjustment is large, if the method is the same as the case where the power flow is small, the correction of the frequency deviation cannot catch up and it is difficult to maintain a single system Therefore, from the viewpoint of early supply-demand balance adjustment, stabilization will be achieved by shutting down the generator.

In the case where the load has to be adjusted based on the interconnection flow, in the present embodiment, the cutoff order is set in consideration of the respective fluctuation rates of the loads 4A to 4E, and the load is adjusted according to the adjustment amount according to the order. The system will be stabilized by successively shutting down the load until the reduction.
Here, as for the factory load, the factory load having a large load variation rate is usually low in importance. Thus, by determining the order from the load variation in advance, the load reduction for stabilization can be achieved. Can be done quickly. If a load having a large fluctuation is left, there is a possibility that a trouble may occur and the whole factory load may be stopped. Further, the load amount of the load having a large fluctuation rate causes a large fluctuation of the total load amount during the system stabilization processing.

  As described above, according to the present embodiment, simple processing (simple determination) can be performed for an accident that separates the system without setting the response to the huge accident assumed case for the power system 1A to be controlled. ) Makes it possible to balance supply and demand and maintain a single system. Further, according to the present embodiment, depending on the direction of the interconnection flow, not only the load limitation but also the adjustment of the generator can maintain the single system, thereby minimizing the influence of the operation.

1A Control target power system 1B Other power system 2 Interconnection lines 3A to 3D Generators 4A to 4E Load 5 System stabilization device 5A Load shedding order setting unit 5B System information input unit 5C Adjustment amount calculation unit 5D Adjustment determination unit 5E Stabilization processing unit 5Ea Processing separation unit 5Eb Load reduction processing unit 5Ec Power generation suppression processing units 10A to 10J Circuit breakers 11A to 11J Sensors

Claims (7)

When a power system to be controlled having a plurality of generators and a plurality of loads is separated from a single system due to a trouble from a state in which the power system is connected to another power system via a connection line, the power system to be controlled is A system stabilization method for maintaining a single system
The power flow from the power system side to be controlled to the other power system side is defined as positive,
When the single system separation occurs, and the difference between the total power generation amount by the plurality of generators and the total load amount by the plurality of loads is equal to or greater than a preset difference,
According to the power flow of the interconnection line before the single system separation, the total power generation is suppressed if the power flow is a positive value, and a predetermined cutoff is performed if the power flow is a negative value. A system stabilization method characterized in that the total load is reduced by interrupting a part of the load in order to stabilize the power system to be controlled.   The suppression of the total power generation amount is realized by dividing the adjustment amount according to the power flow into outputs of a plurality of generators, respectively, and suppressing the outputs of the plurality of generators. 2. The system stabilization method according to claim 1, wherein:   The suppression of the total power generation amount includes shutting down a generator having an output close to the adjustment amount when a ratio of the adjustment amount corresponding to the tidal current to the total load amount exceeds a preset threshold. The system stabilization method according to claim 1 or 2, wherein the method is realized by: For the plurality of loads, the higher the fluctuation of the load based on the results, the higher the priority is, so that the interruption order, which is the order of interruption, is set in advance,
4. The method according to claim 1, wherein the reduction of the total load is realized by interrupting the load in the set interruption order by the adjustment amount corresponding to the power flow. 5. System stabilization method described in 1).   If the difference between the current total power generation amount and the current total load amount is equal to or greater than the set deviation and the current total power generation amount is larger than the current total load amount due to the load interruption, the total power generation 5. The system stabilization method according to claim 4, wherein the amount of power generation is suppressed so that the difference between the total power generation amount and the total load amount is less than the set difference. The power system to be controlled having a plurality of generators and a plurality of loads is operated when a single system is separated due to a trouble from a state in which the power system is connected to another power system by a connection line, and A system stabilizing device for maintaining a single system consisting of a power system,
The power flow from the power system side to be controlled to the other power system side is defined as positive,
An adjustment determination unit that determines whether the difference between the current total power generation amount by the plurality of generators and the current total load amount by the plurality of loads is equal to or greater than a preset deviation ratio,
For a plurality of the loads, a load fluctuation order setting unit that presets a breaking order, which is a breaking order, such that a higher load variation based on an actual result has a higher priority,
In the case of the single system separation state and the difference between the total power generation amount and the total load amount is equal to or larger than a set difference, and when the power flow component of the interconnection line immediately before the single system separation is a negative value, A load reduction processing unit that cuts off the load in the cutoff order set by the load shedding order setting unit, by a load amount corresponding to the power flow just before the single system is separated;
In the case where the single system is separated and the difference between the total power generation amount and the total load amount is equal to or greater than a set deviation ratio, and the power flow component of the interconnection line immediately before the single system separation is a positive value, A power generation suppression processing unit that suppresses the total power generation amount to stabilize the power system to be controlled,
A system stabilizing device comprising:   When the power generation amount to be suppressed by power generation suppression is larger than a preset value with respect to the total load, the power generation suppression processing unit shuts down a generator close to the power generation amount to be suppressed by power generation suppression, The system stabilization device according to claim 6, wherein power generation suppression is performed.

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