JP7809841B2 - Nuclear power plant interconnection control system, modular nuclear power plant, and interconnection control method - Google Patents

Description

The present invention relates to a nuclear power plant cooperative control system, a modular nuclear power plant, and an interconnection control method, which are intended to achieve an output adjustment function at a plurality of nuclear power plants when an output fluctuation is required in a power supply system.

It is anticipated that future power grids will see the large-scale introduction of renewable energy. In particular, variable renewable energy sources (VRE) such as solar and wind power are, in principle, dependent on natural conditions for their power output, making it difficult to predict their power output in advance, and there are cases where the expected output differs significantly from the actual output. Even when such variable power sources are added, maintaining high power quality requires a power source that can act as a regulating power source to absorb fluctuations in power output caused by the variable power sources. Traditionally, the regulating power function has been performed by thermal power plants and hydroelectric power plants. Hydroelectric power plants are used as excellent energy storage facilities. Thermal power plants are used to take advantage of their excellent regulating capabilities.

Nuclear plants are another large-scale power source besides hydroelectric and thermal power plants, but because nuclear plants have a lower output adjustment capacity than other power sources, they have traditionally been operated as baseload plants. Adjusting the output of nuclear plants themselves has been considered, and they do have a certain degree of output adjustment functionality. However, because the output adjustments traditionally performed by hydroelectric and thermal power plants change quickly and over a wide range, there are concerns that adjusting output at nuclear plants in the same way as traditional hydroelectric and thermal power plants may result in them being unable to respond to sudden output adjustment requests and may shorten the lifespan of plant equipment (turbines, fuel, feed/condensate systems, etc.).

Patent document 1 discloses an output command device that commands the amount of power generated to multiple steam turbine power plants connected to a power system under its jurisdiction, the output command device receiving data on the total power generated by the power system, the total power demand of the power system, and the remaining turbine life of each of the multiple steam turbine power plants, and if the total power demand exceeds the total power generated, subtracting the total power generated from the total power demand to calculate the power shortage, calculating the amount of additional power to be allocated by each of the multiple steam turbine power plants to make up for the shortage based on the maximum rated output and remaining turbine life of each of the multiple steam turbine power plants, and commanding the multiple steam turbine power plants to increase the amount of additional power generated.

Japanese Patent Application Laid-Open No. 2021-116687

Patent Document 1 determines the proportion of output control depending on the turbine's remaining lifespan. In order to use a plant for a long period of time, it is undesirable to place a load on a plant with a short remaining lifespan, making this an effective invention in that respect. Meanwhile, whether or not each plant can respond to actual output fluctuations depends on the rate of change specific to each plant meeting the conditions. Furthermore, because operating methods change depending on the plant's operating conditions (for example, from the perspective of investment recovery), there are cases in which remaining lifespan alone is not enough to determine the appropriate ratio.

As the number of variable power sources connected to the power grid increases, plants such as hydroelectric and thermal power plants, which provide balancing power, will fluctuate their output to stabilize power quality. However, hydroelectric plants have relatively small power generation capacities, and as the trend toward decarbonization continues, new installations of thermal power plants are being curbed, so it is expected that the capacity of facilities connected to the grid will decrease.

On the other hand, nuclear power plants are attracting attention as a clean energy source and are now considered important in terms of energy security, with the development of new reactors also gaining momentum. Global increases in installed capacity are expected in the future. In such a situation, nuclear power plants could potentially replace thermal power plants. However, due to the power generation principles, nuclear power plants are not suited to output adjustments and are basically operated as baseload power sources. Therefore, there is a possibility that nuclear power plants will not be able to directly cover the output adjustment operations that have traditionally been performed by thermal power plants.

The present invention has been made to solve the above-mentioned problems, and has an object to provide a nuclear power plant interconnection control system, a modular nuclear power plant, and an interconnection control method that can reduce the output adjustment requirements for each nuclear power plant by having multiple plants share the output adjustment, thereby responding to output fluctuation requirements in the system and stabilizing power quality.

In order to achieve the above object, the present invention provides a nuclear power plant interconnection control system comprising a plurality of nuclear power plants and a control device that issues control commands to the plurality of nuclear power plants, the control device having a memory unit that stores maximum power output change rates of the plurality of nuclear power plants, and when adjusting the power output required by the system, issues a command to the plurality of nuclear power plants to share the load based on the ratio of the maximum power output change rates of the plurality of nuclear power plants, and the plurality of nuclear power plants monitor a reactor pressure signal from the reactor and a turbine speed signal of a turbine connected to a generator, while controlling the in-reactor flow rate with a reactor power command for an internal pump and controlling the turbine steam flow rate with a flow rate command for a control valve . Other aspects of the present invention will be described in the embodiments described below.

According to the present invention, by dividing the output adjustment among multiple plants, the output adjustment requirements for each nuclear plant can be reduced, output fluctuation requirements for the grid can be met, and power quality can be stabilized.

FIG. 1 is a diagram showing a general method of adjusting output of a nuclear power plant. FIG. 2 is a diagram showing an assumed curve of a future power supply configuration according to an embodiment. FIG. 10 is a diagram illustrating a case where an instruction is given at the maximum output change rate of each plant according to the embodiment. FIG. 10 is a diagram showing a case where instructions are given using various parameters in addition to the maximum output change rate of each plant according to the embodiment. FIG. 10 is a diagram illustrating a case where a representative plant issues instructions to a plurality of plants according to the embodiment. FIG. 1 is a diagram illustrating an example of a modular plant according to an embodiment.

The following describes in detail an embodiment of the present invention using drawings and other materials. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications are possible by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the present invention, parts having the same function are given the same reference numerals, and repeated explanations may be omitted.

Figure 1 shows a typical method of adjusting power output at a nuclear power plant. When a power output command 1 is sent to the control device 6 from the plant control device 202 to the nuclear power plant 13, the reactor pressure signal 2 from the reactor 7 and the turbine speed signal 3 of the turbine 10 connected to the generator 11 are monitored, while the reactor flow rate is controlled by a reactor power output command 4 to the internal pump 8, and the turbine steam flow rate is controlled by a flow command 5 to the first control valve 9a. The second control valve 9b plays a role in releasing steam that is not sent to the turbine 10 directly to the condenser 12, and the first control valve 9a and second control valve 9b are operated as a set. Power output adjustment is achieved through these operations.

Figure 2 shows an assumed curve for the future power supply configuration according to the embodiment. As shown in Figure 2, the output of the variable power supply, that is, variable power supply output 101, rises, and output adjustment is required in a period 103, in which the adjustable power supply output needs to be lowered as shown in curve 102. If it is necessary to realize a curve like the adjustable power supply output 102 in Figure 2, it is of course necessary to satisfy the output change rate of this curve.

Figure 3 is a diagram showing the case where instructions are given at the maximum output change rate of each plant according to the embodiment. Figure 3 shows the overall configuration of the nuclear plant interconnection control system 300 according to this embodiment. Note that this configuration is an example of an embodiment that focuses only on the parameter of the maximum output change rate to make the configuration easier to understand. The plant indication device 202 calculates the adjustment power required within the area based on the supply and demand situation 200 and the supply and demand plan 201. Note that the required adjustment power may be calculated by a separate facility and given directly to the plant indication device 202. Furthermore, the input signal may be something that can be calculated from the supply and demand situation 200 and the supply and demand plan 201, such as frequency deviation.

Each nuclear power plant has an achievable power change rate. Here, we assume three plants, and the maximum power change rate of plant A PA is fa (maximum power change rate fa), the maximum power change rate of plant B PB is fb (maximum power change rate fb), and the maximum power change rate of plant C PC is fc (maximum power change rate fc). The plant indicator 202 distributes proportionally according to these maximum power change rates.

In other words, the nuclear plant interconnection control system 300 has multiple nuclear plants (e.g., plant A PA, plant B PB, plant C PC) and a control device (e.g., plant instruction device 202) that issues control commands to the multiple nuclear plants, and the control device has a memory unit that stores the maximum output change rates of the multiple nuclear plants, and when adjusting the output required in the system, can issue commands to the multiple nuclear plants to share the load based on the ratio of the maximum output change rates of the multiple nuclear plants.

For example, if the rate of change of the adjustment power required on the grid side is fgrid, the command for the rate of change of output to plant A PA is given by fgrid x fa/(fa + fb + fc). Similarly, the command for the rate of change of output to plant B PB is given by fgrid x fb/(fa + fb + fc). The command for the rate of change of output to plant C PC is given by fgrid x fc/(fa + fb + fc).

The following explains using specific numerical values. The maximum output change rate of plant A PA is 50 MW/h, the maximum output change rate of plant B PB is 40 MW/h, and the maximum output change rate of plant C PC is 30 MW/h, and the grid demand is 100 MW/h.

In the case of these specifications, Plant A will be instructed to output 100 MW/h x 50 MW/h / (50 MW/h + 40 MW/h + 30 MW/h) = 42 MW/h. Note that these specifications are hypothetical to simplify the explanation and will differ from the actual specifications.

This control balances the differences in the rate of change for each plant with the proportion of the rate of change that each plant actually bears, making it possible to reduce the rate of output change compared to implementing control output for only one plant. Furthermore, if a plant cannot be used due to a scheduled inspection or other reason, or if a constant output is desired, the rate of change for that plant is set to "0" and the plant is treated as an exempt plant from output adjustments, and no output adjustments are implemented.

Furthermore, even if output adjustments are made by multiple plants, if the required adjustment capacity cannot be secured on the grid side, cooperative control will be performed within the range in which adjustment capacity can be secured. For example, if the capacity that can be provided by a plant is 100% and the grid demand is 110%, the command signal to each plant will be multiplied by (plant capacity 100% / grid demand 110%) (as a result, the command to plant A PA will be (plant capacity 100% / grid demand 110%) x fgrid x fa / (fa + fb + fc).

Figure 4 is a diagram showing the case where instructions are given using various parameters in addition to the maximum output change rate of each plant in the embodiment. In actual operation, in addition to the maximum output change rate, there are also depreciation degrees Ga, Gb, and Gc as shown in Figure 4, from the perspective of plant operation and electrical requirements on the system side. When adjusting output using a control valve (CV valve), there are CV valve deterioration degrees Ba, Bb, and Bc. When adjusting output based on the deterioration degree of the feedwater/condensate system, the deterioration degrees Ca, Cb, and Cc of the feedwater/condensate system are considered as parameters.

The depreciation rates Ga, Gb, and Gc are coefficients determined according to the depreciation status, and are set to 0 at the time of construction, 1 once depreciation is complete, and an intermediate value if depreciation is in progress. The CV valve deterioration rates Ba, Bb, and Bc are coefficients determined by the degree of CV valve deterioration, and are set to 1 for new products, increase as deterioration progresses, and take the value of 0 when the valve is completely unusable. The feedwater and condensate system deterioration rates Ca, Cb, and Cc are set to 1 for new products, increase as deterioration progresses, and take the value of 0 when the valve is completely unusable. Here, for simplicity, the range of change for each coefficient is set to 0 to 1, but the range of these coefficients and how they change will be considered and determined according to the actual plant conditions.

For example, if the depreciation rate is considered as an additional parameter, the command for the output change rate to plant A PA is given by fgrid x fa x Ga/(fa x Ga + fb x Gb + fc x Gc). Similarly, the command for the output change rate to plant B PB is given by fgrid x fb x Gb/(fa x Ga + fb x Gb + fc x Gc). The command for the output change rate to plant C PC is given by fgrid x fc x Gc/(fa x Ga + fb x Gb + fc x Gc).

This allows plants that have completed depreciation to be prioritized for output adjustment. Also, if you do not want to adjust the output of a plant that has not completed depreciation, you can exclude that plant by setting the coefficient G = 0.

The other coefficients, CV valve deterioration levels Ba, Bb, and Bc, and feed/condensate system deterioration levels Ca, Cb, and Cc, can also be integrated into the maximum output change rate in the same way. In other words, if deterioration has progressed to the point where output adjustment is not desired at the plant, the plant can be excluded by setting coefficients B = 0 and C = 0.

In addition, each coefficient can be used independently. That is, when adjusting the output required by the system, the plant indicator 202 can use one of the following conditions for sharing among multiple nuclear power plants, instead of the maximum output change rate: the degree of depreciation of each plant, the degree of deterioration of the control valve, or the degree of deterioration of the feedwater/condensate system.

The above control is assumed to be performed by a central power supply control center, but similar functions may also be provided to individual plants.

Figure 5 is a diagram showing the case where instructions are given to multiple plants in a representative plant according to the embodiment. For example, as shown in Figure 5, it is possible to consolidate the function of giving instructions to adjust the output of other plants PB and PC in plant A PA.

The control of this invention is intended to enable coordination between plants, but it can also be applied to modular plants if similar functions are desired.

Figure 6 is a diagram showing an example of a modular plant according to an embodiment. In a typical nuclear power plant, one reactor, containment vessel, etc. are connected to a dedicated turbine system, but in a modular plant, multiple modules (reactors, containment vessels, etc.) are arranged in parallel and connected to independent turbine systems. The modular plant 501 is composed of multiple modules 502, each of which is composed of equipment equivalent to that of the nuclear power plant 13 in Figure 1. As a power plant, it is controlled as a single plant by a modular plant overall control device 504, which issues instruction signals 503 to each module depending on the operating status. Since the modular plant 501 has these characteristics and can be controlled on an individual module basis, it is also possible to implement the control of the present invention for each module.

The nuclear power plant interconnection control system, modular nuclear power plant, interconnection control device, and interconnection control method of the present embodiment have the following features.
(1) The nuclear power plant interconnection control system 300 includes a plurality of nuclear power plants (e.g., plant A PA, plant B PB, and plant C PC) and a control device (e.g., plant instruction device 202) that issues control commands to the plurality of nuclear power plants. The control device has a memory unit that stores the maximum power change rates of the plurality of nuclear power plants, and when adjusting the power required by the system, issues a command to the plurality of nuclear power plants to share the power adjustment based on the ratio of the maximum power change rates of the plurality of nuclear power plants. In this way, by sharing the power adjustment among the plurality of nuclear power plants, it is possible to reduce the burden on each nuclear power plant for power adjustment and meet system requirements. Furthermore, by suppressing excessive fluctuations within the plants, it is possible to suppress a reduction in the lifespan of the plants.

(2) In (1) above, when adjusting the output required by the system, the control device can use, in addition to the maximum output change rate, any one of the following conditions for sharing among multiple nuclear plants: the degree of depreciation of each plant, the degree of deterioration of the control valve, or the degree of deterioration of the feed/condensate system (see Figure 4).

(3) The nuclear power plant interconnection control system 300 has multiple nuclear power plants and a control device that issues control commands to the multiple nuclear power plants. The control device has a memory unit that stores the depreciation degree, the deterioration degree of the control valves, and the deterioration degree of the water supply and condensate systems of the multiple nuclear power plants. When adjusting the output required by the system, the control device can issue a command to have the multiple nuclear power plants share the load based on the ratio of any one of the depreciation degree, the deterioration degree of the control valves, and the deterioration degree of the water supply and condensate systems of the multiple nuclear power plants (see Figure 4).

(4) A modular nuclear power plant having multiple reactor modules (e.g., module 502), including a control device (e.g., modular plant overall control device 504) that issues control commands to the multiple reactor modules. The control device has a memory unit that stores the maximum power change rates of the multiple reactor modules, and when adjusting the power required by the system, issues commands to the multiple reactor modules to share the load based on the ratio of the maximum power change rates of the multiple reactor modules. In this way, by sharing the power adjustment load among the multiple reactor modules, it is possible to reduce the burden associated with power adjustment on each reactor module and meet system requirements. Furthermore, by suppressing excessive fluctuations within each reactor module, it is possible to suppress a decrease in the lifespan of each reactor module.

(5) In (4) above, when adjusting the output required by the system, the control device can use, in addition to the maximum output change rate, any one of the following conditions for sharing among multiple reactor modules: the degree of depreciation of each reactor module, the degree of deterioration of the control valve, or the degree of deterioration of the feed/condensate system.

(6) A modular nuclear power plant having multiple reactor modules, comprising a control device that issues control commands to the multiple reactor modules, and the control device has a memory unit that stores the degree of depreciation of the multiple reactor modules, the degree of deterioration of the control valves, and the degree of deterioration of the water supply and condensate systems, and when adjusting the output required by the system, can issue commands to have the multiple reactor modules share the load based on the ratio of any one of the degree of depreciation of the multiple reactor modules, the degree of deterioration of the control valves, and the degree of deterioration of the water supply and condensate systems.

(7) A grid-connection control device (e.g., plant instruction device 202) that connects multiple nuclear plants and issues control commands, the grid-connection control device having a memory unit that stores the maximum output change rates of the multiple nuclear plants, and when adjusting the output required in the system, can issue commands to have the multiple nuclear plants share the load based on the ratio of the maximum output change rates of the multiple nuclear plants.

(8) A grid control method for interconnecting multiple nuclear power plants and issuing control commands, which stores the maximum output change rates of the multiple nuclear power plants, and when adjusting the output required by the system, can issue commands to have the multiple nuclear power plants share the load based on the ratio of the maximum output change rates of the multiple nuclear power plants.

(9) The nuclear power plant interconnection control system 300 has multiple nuclear power plants (e.g., plant A PA, plant B PB, and plant C PC) and a control device (e.g., plant instruction device 202) that issues control commands to the multiple nuclear power plants. The control device has a memory unit that stores the status of the multiple nuclear power plants, and when adjusting the output required by the system, can issue commands to the multiple nuclear power plants to share the load depending on the status of the multiple nuclear power plants. Examples of the status of the nuclear power plants include the maximum output change rate of the nuclear power plants, the degree of depreciation, the degree of deterioration of the control valves, and the degree of deterioration of the feedwater and condensate systems.

REFERENCE SIGNS LIST 1 Power output command 2 Reactor pressure signal 3 Turbine speed signal 4 Reactor power output command 5 Flow rate command 6 Control device 7 Reactor 8 Internal pump 9a First control valve 9b Second control valve 10 Turbine 11 Generator 12 Condenser 13 Nuclear power plant 101 Variable power output 102 Adjustable power output 103 Period during which output adjustment is required 200 Supply and demand situation 201 Supply and demand plan 202 Plant instruction device (control device)
300 Nuclear power plant interconnection control system 501 Modular plant 502 Module (nuclear reactor module)
503 Indication signal 504 Modular plant total control device (control device)
fa, fb, fc Maximum power change rate Ga, Gb, Gc Degree of depreciation Ba, Bb, Bc Degree of CV valve deterioration Ca, Cb, Cc Degree of deterioration of feedwater and condensate system PA Plant A PB Plant B PC Plant C

Claims (5)

a plurality of nuclear power plants;
a control device that issues control commands to the plurality of nuclear plants,
the control device has a storage unit that stores maximum output change rates of the plurality of nuclear power plants, and when adjusting the output required by the system, issues a command to the plurality of nuclear power plants to share the output based on a ratio of the maximum output change rates of the plurality of nuclear power plants;
The plurality of nuclear power plants monitor a reactor pressure signal from the reactor and a turbine speed signal of a turbine connected to a generator, and control the flow rate in the reactor by a reactor power command of an internal pump, and control the turbine steam flow rate by a flow rate command of a control valve.
A nuclear power plant interconnection control system characterized by: 2. The nuclear power plant interconnection control system according to claim 1, wherein the control device, when adjusting the output required by the system, uses, in addition to the maximum output change rate, any one of the following as a condition for dividing the load among the plurality of nuclear power plants: a degree of depreciation of each plant, a degree of deterioration of a control valve, or a degree of deterioration of a feed/condensate system. 1. A modular nuclear power plant having a plurality of reactor modules,
a control device that issues control commands to the plurality of reactor modules;
The control device has a memory unit that stores the maximum power change rates of the plurality of reactor modules, and when adjusting the power required by the system, issues a command to have the plurality of reactor modules share the power based on the ratio of the maximum power change rates of the plurality of reactor modules;
The plurality of reactor modules monitor a reactor pressure signal from the reactor and a turbine speed signal from a turbine connected to a generator, and control the flow rate in the reactor by a reactor power command of an internal pump, and control the turbine steam flow rate by a flow rate command of a control valve.
A modular nuclear power plant characterized by: 4. The modular nuclear plant according to claim 3, wherein the control device, when adjusting the output required in the system, uses, in addition to the maximum output change rate, any one of the following as a condition for sharing among the plurality of reactor modules : a degree of depreciation of each reactor module, a degree of deterioration of a control valve, and a degree of deterioration of a feedwater/condensate system. 1. A grid control method for interconnecting a plurality of nuclear power plants and issuing control commands, comprising:
a maximum power change rate of the plurality of nuclear power plants is stored;
When adjusting the output required by the system, issuing a command to have the plurality of nuclear power plants share the output based on a ratio of the maximum output change rates of the plurality of nuclear power plants;
The plurality of nuclear power plants monitor a reactor pressure signal from the reactor and a turbine speed signal of a turbine connected to a generator, and control the flow rate in the reactor by a reactor power command of an internal pump, and control the turbine steam flow rate by a flow rate command of a control valve.
A grid connection control method characterized by: