Power plant control device which uses a model, a learning signal, a correction signal, and a manipulation signal

A control device for a plant includes a manipulation signal generation section for generating the manipulation signal to the plant, a model adapted to simulate a characteristic of the plant, a learning section for generating an input signal of the model so that an output signal obtained by the model simulating the characteristic of the plant satisfies a predetermined target, a learning signal generation section for calculating a learning signal in accordance with a learning result in the learning section, a manipulation result evaluation section for calculating a first deviation as a deviation between a first measurement signal of the plant obtained as a result of application of a certain manipulation signal to the plant and a target value of the measurement signal, and a second deviation as a deviation between a second measurement signal of the plant obtained as a result of application of an updated manipulation signal to the plant and the target value, and a correction signal generation section for generating, when the second deviation calculated by the manipulation result evaluation section is greater than the first deviation, a correction signal of the manipulation signal to be generated by the manipulation signal generation section.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control device for a plant, and a control device for a thermal power plant adapted to control a thermal power plant equipped with a boiler.

Further, the present invention relates to a gas concentration estimation device and a gas concentration estimation method of a coal-burning boiler provided to the thermal power plant, and in particular to a gas concentration estimation device and a gas concentration estimation method of a coal-burning boiler adapted to estimate the concentrations of CO and NOx as gas components included in the exhaust gas emitted from the coal-burning boiler.

2. Description of the Related Art

In general, a control device for controlling a plant processes a measurement signal obtained from the plant as a controlled object, and calculates a manipulation signal to be applied to the controlled object to output as a control signal.

The control device for a plant is provided with an algorithm for calculating the manipulation signal so that the measurement signal of the plant satisfies the target value.

As a control algorithm used for the control of a plant, there is cited a proportional-and-integral (PI) control algorithm.

In the PI control, the manipulation signal to be applied to the controlled object is obtained by adding a value obtained by temporally integrating deviation of the measurement value of the plant from the target value thereof to a value obtained by multiplying the deviation by a proportional gain.

Since the control algorithm using the PI control can describe the input-output relationship with a block diagram and so on, the cause-and-effect relationship can easily be understood. Further, the PI control is a stable and safe control algorithm in plant control, and therefore, has a lot of records of application to actual equipment.

However, in the case in which the plant is operated in an unexpected condition such as a change in the operation mode of the plant or a change in the environment, some operation such as modification of the control logic is required in some cases.

Incidentally, adaptive control for automatically correcting and modifying the control method in accordance with a change in the operation mode of the plant or a change in the environment is also available.

As a plant control method using a learning algorithm as one of the adaptive control methods, there can be cited a technology described in JP-A-2000-35956, for example.

In the plant control method using the learning algorithm as the technology described in JP-A-2000-35956, the control device is provided with a model for estimating the characteristic of the controlled object, and a learning section for learning a method of generating a model input with which a model output achieves the target value thereof.

Further, as a learning algorithm, a document “Reinforcement Learning” (joint translator: Sadayoshi Mikami and Masaaki Minagawa, Morikita Publishing Co., Ltd., published: Dec. 20, 2000, paragraph 142-172 and 247-253) describes a method of providing a positive evaluation value when the measurement signal achieves the operation target value, and learning a method of generating a manipulation signal using an algorithm such as Actor-Critic, Q-learning, or Real-Time Dynamic Programming based on the evaluation value.

Further, in thermal power plans equipped with a coal-burning boiler, which uses coal as fuel, the concentrations of CO and NOx, which are environmental pollutants included in the exhaust gas emitted from the coal-burning boiler, are required to be suppressed to be lower than the respective regulation values.

The amounts of production of CO and NOx included in the exhaust gas of the coal-burning boiler correlate inversely with each other, and when burning coal in the coal-burning boiler, if the air (oxygen) for combustion is excessively supplied, the amount of production of NOx increases, and if the air supply is insufficient to the contrary, the amount of production of CO increases.

In recent coal-burning boilers, in order for reducing the amounts of production of both of CO and NOx and at the same time improving the combustion efficiency of the coal-burning boilers, there is adopted a two-stage combustion system in which the combustion air is fed in the coal-burning boiler in stages.

In the combustion control by the two-stage combustion system, an adjustment of the amount of combustion air supplied to the coal-burning boiler, selection of a combustion pattern of a burner provided to the coal-burning boiler, and so on are performed to create the optimum combustion condition of the coal-burning boiler.

Further, the adjustment (e.g., an adjustment of a control gain, planning of the burner combustion pattern) for optimizing the combustion control has previously been executed off-line.

It should be noted that the combustion conditions thus adjusted previously are optimized with respect to a typical operation mode, and nothing more than a rough operation plan.

Further, since the characteristic of the coal-burning boiler as a plant is varied by age deterioration, the optimum combustion conditions at the time when the operation of the coal-burning boiler starts are gradually shifted from the actual optimum combustion conditions across the ages.

On the other hand, it is required from an economic viewpoint to perform optimization (to maximizing the combustion efficiency while suppressing the concentrations of CO and NOx within allowable ranges) of the operation of coal-burning boilers in accordance with ever-changing operation conditions such as load requirement values and age deterioration.

In order for realizing the optimization of the operation of coal-burning boilers, it is required that the variation in the concentrations of CO and NOx in the exhaust gas responsive to a change in a control demand based on the present operation conditions can be simulated on-line.

Specifically, there is required a function of evaluating the combustion efficiency of the coal-burning boiler and amounts of emission of environmental-load materials in the case in which the control demand is changed with respect to the present operation conditions of the coal-burning boiler obtained from measurement data, and searching the optimum control point in view of the both points.

There are several methods for estimating the concentrations of CO and NOx in the exhaust gas emitted from coal-burning boilers, and a method of modeling the relationship between each of the operation conditions and variation trend of the gas concentrations using the data of actual equipment based on a learning algorithm such as a neural network is available.

For example, JP-A-2007-264796 discloses, with respect to creation of a continuous model for simulating the characteristic of a plant used for controlling a boiler, a control method of creating the continuous model based on process data of the boiler, creating the continuous model again using mechanically analyzed process data and operation data of the actual equipment, performing reinforcement learning using the continuous model thus created again to control the boiler, thereby reducing the environmental-load materials in the exhaust gas. Further, it is suggested that a neural network is used for creating the continuous model.

In the case of such a modeling method, by providing actual equipment data, estimation models of the CO concentration and the NOx concentration corresponding to the characteristic of the actual equipment can easily be created. In other words, since even after the operation of the coal-burning boiler is started, the estimation models suitable for the state can be created by using the data of the actual equipment in operation, such a modeling method is used frequently.

In applying the plant control technology using the learning algorithm described in JP-A-2000-35956 to the plant control, if the model for predicting the characteristic of the plant as a controlled object and the characteristic of the actual plant do not match each other, there is caused a difference between the predicted value of the model and the actual measurement value of the plant.

Therefore, even if the manipulation conditions are optimum in the predicted value of the model, the manipulation conditions are not optimum for the actual plant, and consequently, the plant cannot properly controlled with these manipulation conditions.

As a plant control method capable of avoiding the phenomenon described above, there can be cited a method of correcting the model using the measurement value of the actual plant so as to match the actual plant characteristic and the characteristic of the model with each other.

However, according to the method described above, it requires a long period of time to accumulate the measurement data of the actual plant necessary for correcting the model, moreover, the expected control performance is not exerted during the period for accumulating the data.

The technology for appropriately coping with the case in which the characteristics of model and the actual plant do not match each other is not at all described in JP-A-2000-35956.

An object of the present invention as an embodiment is to provide a control device for a plant and a control device for a thermal power plant each capable of preferably maintaining the control characteristic of the plant even in the case in which the characteristic of the model for predicting the characteristic of the plant as a controlled object is different from the characteristic of the actual plant.

The actual equipment data as the measurement value of the coal-burning boiler includes transitional states in changing the operation conditions such as the output. In this case, correlation between the measurement values corresponds to a temporary state, and therefore, shows a state different from the correlation after the state of the plant is settled with elapse of time.

In the case in which it is attempted to model the dynamic characteristic of the plant using the neural network suggested in JP-A-2007-264796, it is effective to perform the learning of the neural network using such actual equipment data.

However, in the case in which it is attempted to learn the static characteristic of the plant, an error is caused in modeling by using such actual equipment data including the transitional state to the learning. Further, in general, measurement values of the plant include a measurement error.

For example, although the temperature or the like can be measured with high accuracy, the flow rate or the like is apt to include a measurement error. Further, the age deterioration in sensors also cause a measurement error. Therefore, there are mixed data with high accuracy and data with low accuracy including a large error in the actual equipment data.

If the learning of the neural network is performed using the actual equipment data including such data with low accuracy mixed thereto, the model of the neural network thus constructed also has low accuracy.

As a result, in the case in which the estimation model of the concentrations of CO and NOx included in the exhaust gas emitted from the coal-burning boiler as a controlled object by learning the trend of the actual equipment data using the actual equipment data including the data with low accuracy mixed thereto, there arises a problem that the estimation accuracy of the model thus constructed becomes lowered.

An object of the present invention as another embodiment is to provide a gas concentration estimation device of a coal-burning boiler and a gas concentration estimation method each suppressing an estimation error of a neural-network model caused by a measurement error included in actual equipment data in the case in which the variation in the concentration of CO or the concentration of NOx in the exhaust gas is simulated using a neural network in combustion control of the coal-burning boiler, thereby making it possible to estimate the gas concentration with high accuracy.

SUMMARY OF THE INVENTION

A control device for a plant according to an embodiment of the present invention is adapted to calculate a manipulation signal for controlling a plant using a measurement signal obtained by measuring an operation state of the plant, includes manipulation signal generation means for generating the manipulation signal to be transmitted to the plant, a model adapted to simulate a characteristic of the plant, learning means for generating an input signal of the model so that an output signal obtained by the model simulating the characteristic of the plant satisfies a predetermined target, learning signal generation means for calculating a learning signal in accordance with a learning result in the learning means, manipulation result evaluation means for calculating a first deviation as a deviation between a first measurement signal of the plant obtained as a result of application of a certain manipulation signal to the plant and a target value of the measurement signal, and a second deviation as a deviation between a second measurement signal of the plant obtained as a result of application of an updated manipulation signal to the plant and the target value, and correction signal generation means for generating, when the second deviation calculated by the manipulation result evaluation means is greater than the first deviation, a correction signal of the manipulation signal to be generated by the manipulation signal generation means, and the correction signal generation means is configured to calculate the correction signal based on a characteristic variable of a model characteristic extracted from the model, and the manipulation signal generation means is configured to calculate the manipulation signal for controlling the plant using at least the learning signal calculated by the learning signal generation means and the correction signal calculated by the correction signal generation means.

A control device for a thermal power plant according to another embodiment of the invention is adapted to calculate a manipulation signal for controlling a thermal power plant using a measurement signal obtained by measuring an operation state of the thermal power plant, the measurement signal including at least one of the concentration of nitrogen oxide, the concentration of carbon monoxide, the concentration of carbon dioxide, the concentration of sulfur oxide, and the concentration of mercury in an exhaust gas emitted from a boiler of the thermal power plant, a flow rate of coal, a rotational frequency of a classification machine of a mill, and a generator output, the manipulation signal including at least one of opening of an air damper, an air flow rate, an air temperature, a fuel flow rate, and an exhaust gas recirculation flow rate of the boiler, and the control device includes manipulation signal generation means for generating the manipulation signal to be transmitted to the thermal power plant, a model adapted to simulate a characteristic of the thermal power plant, learning means for generating an input signal of the model so that an output signal obtained by the model simulating the characteristic of the plant satisfies a predetermined target, learning signal generation means for calculating a learning signal in accordance with a learning result in the learning means, manipulation result evaluation means for calculating a first deviation as a deviation between a first measurement signal of the thermal power plant obtained as a result of application of a certain manipulation signal to the thermal power plant and a target value of the measurement signal, and a second deviation as a deviation between a second measurement signal of the thermal power plant obtained as a result of application of an updated manipulation signal to the thermal power plant and the target value, and correction signal generation means for generating, when the second deviation calculated by the manipulation result evaluation means is greater than the first deviation, a correction signal of the manipulation signal to be generated by the manipulation signal generation means, and the model includes a plurality of models corresponding to each of a burner pattern, a load level, and a coal type of the boiler of the thermal power plant, the manipulation result evaluation means is provided with a function of figuring out the burner pattern based on the value of the measurement signal of a flow rate of the coal supplied to the mill of the boiler, a function of figuring out a load level based on one of an output demand and the value of the measurement signal of the generator output, and a function of figuring out the coal type based on the value of the measurement signal of the rotational frequency of the classification machine of the mill, and the learning signal generation means is configured to generate the learning signal in accordance with the result of learning using the models corresponding respectively to the conditions figured out by the manipulation result evaluation means, and the manipulation signal generation means is configured to calculate the manipulation signal for controlling the thermal power plant using at least the learning signal calculated by the learning signal generation means and the correction signal calculated by the correction signal generation means.

A gas concentration estimation device of a coal-burning boiler according to another embodiment of the present invention is adapted to estimate the concentration of the gas component included in an exhaust gas emitted from a coal-burning boiler using a neural network, includes a process database section adapted to store process data of a coal-burning boiler, a filtering processing section adapted to perform filtering processing for extracting data suitable for learning of a neural network from the process data stored in the process database section, a neural-network learning processing section adapted to perform learning processing of the neural network based on the data extracted by the filtering processing section and suitable for learning of the neural network, and a neural-network estimation processing section adapted to perform estimation processing of the CO concentration or the NOx concentration in the exhaust gas emitted from the coal-burning boiler based on the learning processing of the neural-network learning processing section.

According to the present invention as an embodiment, it is possible to realize a control device for a plant and a control device for a thermal power plant each capable of preferably maintaining the control characteristic of the plant even in the case in which the characteristic of the model for predicting the characteristic of the plant as a controlled object is different from the characteristic of the actual plant.

According to the present invention as another embodiment, it is possible to realize a gas concentration estimation device of a coal-burning boiler and a gas concentration estimation method each suppressing an estimation error of a neural-network model caused by a measurement error included in actual equipment data in the case in which the variation in the concentration of CO or the concentration of NOx in the exhaust gas is simulated using a neural network in combustion control of the coal-burning boiler, thereby making it possible to estimate the gas concentration with high accuracy.

DETAILED DESCRIPTION OF THE INVENTION

Then, a control device for a plant and a control device for a thermal power plant as embodiments of the present invention will be explained with reference to the accompanying drawings.

First Embodiment

FIG. 1is a control block diagram showing an overall configuration of a control device for a plant as a first embodiment of the invention.

InFIG. 1, in the present embodiment, a plant100is controlled by a control device200.

The control device200has a configuration provided with measurement signal conversion means300, manipulation result evaluation means400, reference signal generation means500, learning signal generation means600, learning means610, a model620, correction signal generation means700and manipulation signal generation means800as operational equipment.

Further, the control device200is provided with a measurement signal database230, a model construction database240, a learning information database250, a correction signal calculation database260, and a manipulation signal database270as databases.

Further, the control device200has an external input interface210and an external output interface220as interfaces with the outside.

Further, the control device200acquires a measurement signal1obtained by measuring various state variables of the plant100from the plant100via the external input interface210, and further, the control device200outputs, for example, a manipulation signal23for controlling a flow rate of an operating fluid supplied thereto to the plant100via the external output interface220.

The measurement signal1of the various state variables of the plant100acquired to the control device200from the plant100is stored in the measurement signal database230as the database provided to the control device200as a measurement signal2via the external input interface210.

A manipulation signal22generated by the manipulation signal generation means800as the operational equipment provided to the control device200is transmitted from the manipulation signal generation means800to the external output interface220, and at the same time, stored in the manipulation signal database270as the database provided to the control device200.

Further, in the manipulation result evaluation means400as the operational equipment provided to the control device200, flags12,13,14, and15are calculated using a measurement signal3stored in the measurement signal database.

The flags12,13,14, and15calculated by the manipulation result evaluation means400are transmitted respectively to the reference signal generation means500, the learning signal generation means600, the correction signal generation means700, and the manipulation signal generation means800as the operational equipment provided to the control device200.

The reference signal generation means500, the learning signal generation means600, the correction signal generation means700, and the manipulation signal generation means800determine whether or not the operations thereof should be executed (e.g., they do not execute their operations if the value of the flag is 0, while they execute their operations if the value of the flag is 1) based on the values of the flags12,13,14, and15thus transmitted, respectively.

It should be noted that the method of determining the values of the flags will be described later usingFIG. 3.

The manipulation signal generation means800as the operational equipment provided to the control device200calculates the manipulation signal22using a reference signal17generated by the reference signal generation means500, a learning signal16generated by the learning signal generation means600, and a correction signal18generated by the correction signal generation means700.

The reference signal generation means500as the operational equipment provided to the control device200calculates the reference signal17using a measurement signal4stored in the measurement signal database230.

The reference signal generation means500is composed of a proportional-and-integral control (PI control) circuit and so on, and is arranged to calculate the reference signal17based on a previously designed logic.

The learning signal calculation means600as the operational equipment provided to the control device200calculates a learning signal16using the measurement signal4stored in the measurement signal database230, a manipulation signal21stored in the manipulation signal database270, and learning information data11stored in the learning information database250.

The learning information data11stored in the learning information database250is generated using learning information data9from the learning means610and a model output7from the model620.

The model620as the operational equipment provided to the control device200has a function of simulating the control characteristic of the plant100using a statistical model and a physical model built inside thereof.

The manipulation signal23generated in the control device200is provided to the plant via the external output interface220, and the measurement signal1of the plant100as a control result is received by the control device200via the external input interface210.

The learning means610and the model620are made to operate in combination, thereby simulating these conditions, and these conditions are output as the model output7.

Specifically, a model input8generated by the learning means is provided to the model620, and the learning means610receives the model output7as the control result.

The model620calculates the model output7corresponding to the model input8input from the learning means610using model construction data6stored in the model construction database240, and then outputs the model output7.

The model620is built with the statistical model such as a neural network and the physical model of the plant100.

The model construction database240stores actual equipment data5generated by removing a noise included in the measurement signal4output from the measurement signal database230by the measurement signal conversion means300, and the model construction data6such as a model parameter required to build the model620.

The learning means610as the operational equipment provided to the control device200learns a method of generating the model input8with which the model output7calculated by the model620becomes a desired value.

The parameters used for learning such as a target value of the model output7are stored in the learning information database250, and the learning is performed by the learning means610using learning information data10thus stored therein.

As a method of implementing the learning means610, the reinforcement learning can be cited. In the reinforcement learning, the model input8is generated in a trial-and-error manner in the early stage thereof.

The learning means610becomes to be able to generate the model input8with which the model output7calculated by the model620becomes the desired value as it proceeds with the learning thereafter.

As such a learning algorithm, the document “Reinforcement Learning” described above describes a method of providing a positive evaluation value when the measurement signal achieves the operation target value, and learning a method of generating a manipulation signal using an algorithm such as Actor-Critic, Q-learning, or Real-Time Dynamic Programming based on the evaluation value.

The learning means610can adopt various optimization methods such as evolutionary computation besides the reinforcement learning described above.

The information data9as the result of learning performed by the learning means610is stored in the learning information database250.

The correction signal generation means700as the operational equipment provided to the control device200calculates the correction signal18using the manipulation signal21stored in the manipulation signal database270, the measurement signal4stored in the measurement signal database230, learning information data19stored in the learning information database250, and correction signal calculation data20stored in the correction signal calculation database260.

The correction signal generation means700is configured to have at least one of a function of increasing the value of the manipulation signal, a function of decreasing the value of the manipulation signal, a function of keeping the value of the manipulation signal as it stands, a function of resetting the value of the manipulation signal, and a function of matching the value of the manipulation signal and a predetermined value.

Further, the correction signal generation means700is capable of extracting a characteristic variable of the model620to calculate the correction signal18. The operation of the correction signal generation means700will be described later in detail.

Further, the correction signal18generated by the correction signal generation means700is output to the manipulation signal generation means800so as to correct the manipulation signal22generated by the manipulation signal generation means800.

The manipulation signal generation means800calculates the manipulation signal22based on the correction signal18input from the correction signal generation means700to output the manipulation signal22from the control device200to the plant100via the external output interface220as the manipulation signal23for controlling, for example, burners of a boiler and an air flow rate of an air port.

Further, as shown inFIG. 1, in the vicinity of the control device200, there are disposed an external input device900composed mainly of a keyboard901and a mouse902, a maintenance tool910, and an image display device950.

Further, it is arranged that the operator of the plant100generates a maintenance tool input signal51using the external input device900composed mainly of the keyboard901and the mouse902to input the maintenance tool input signal51to the maintenance tool910, thereby making it possible to display information of the various databases disposed in the control device200on the image display device950.

The maintenance tool910is composed mainly of an external input interface920, a data transmission and reception processing section930, and an external output interface940.

The maintenance tool input signal51generated by the external input device900is acquired by the maintenance tool910via the external input interface920.

The data transmission and reception section930of the maintenance tool910is configured to acquire the database information50from the various databases disposed in the control device200in accordance with the information of a maintenance tool input signal52.

The data transmission and reception processing section930of the maintenance tool910transmits a maintenance tool output signal53obtained as a result of processing of the database information50to the external output interface940.

The external output interface940transmits an output signal54based on the maintenance tool output signal53to the image display device950so as to display the output signal54on the image display device950.

It should be noted that although in the control device200as the embodiment of the present invention described above, the measurement signal database230, the model construction database240, the learning information database250, the correction signal calculation database260, and the manipulation signal database270forming the databases provided to the control device200, the measurement signal conversion means300, the manipulation result evaluation means400, the reference signal generation means500, the learning signal generation means600, the learning means610, the model620, the correction signal generation means700, and the manipulation signal generation means800are disposed inside the control device200, it is also possible to dispose all or some of these constituents outside the control device200.

FIG. 2is a flowchart showing a control procedure in the control device for a plant as the first embodiment shown inFIG. 1.

InFIG. 2, the control device200of the plant100performs the control of the plant100using the steps1000,1010,1020,1030,1040,1050, and1060of the present flowchart in combination.

Further, as shown inFIG. 2, the control device200has three operation modes of A, B, and C.

Firstly, an initial mode is determined in the step1000of determining the initial mode, and specifically, the initial mode in the present embodiment is set to A.

Therefore, the process proceeds to the mode discrimination step to perform the mode discrimination. Then the process proceeds to the manipulation signal generation step1020if the operation mode is mode A, the manipulation signal generation step1030if the operation mode is mode B, or the manipulation signal generation step1040if the operation mode is mode C, respectively.

In each of the manipulation signal generation steps1020,1030, and1040to which the process proceeds in accordance with the discrimination result in the mode discrimination step1010, the manipulation signal generation means800provided to the control device200is made to operate to generate the manipulation signal22.

The manipulation result evaluation means400provided to the control device200operates to create the flags12,13, and15for making the reference signal generation means500, the learning signal generation means600, and the correction signal generation means700operate, respectively, according to needs using the measurement signal3stored in the measurement signal database.

In the case in which the mode A is set as the initial mode of the drive mode, and the process proceeds to the manipulation signal generation step1020, the manipulation signal22is calculated based on a formula 1 provided to the manipulation signal generation means800as an operational function using the reference signal17generated by the reference signal generation means500.

Here, So denotes the manipulation signal, and Sb denotes the reference signal.
So=Sb  (1)

Further, if the drive mode makes the transition to the mode B, and the process proceeds to the manipulation signal generation step1030, the manipulation signal22is calculated based on a formula 2 provided to the manipulation signal generation means800as an operational function using the reference signal17generated by the reference signal generation means500and the learning signal16generated by the learning signal generation means600.

Here, Sl denotes the learning signal.
So=Sb+Sl(2)

Further, if the drive mode makes the transition to the mode C, and the process proceeds to the manipulation signal generation step1040, the manipulation signal22is calculated based on a formula 3 provided to the manipulation signal generation means800as an operational function using the reference signal17generated by the reference signal generation means500, the learning signal16generated by the learning signal generation means600, and the correction signal18generated by the correction signal generation means700. Here, Sr denotes the correction signal.
So=Sb+Sl+Sr(3)

It should be noted that although the control device200of the present embodiment calculates the manipulation signal22using the formulas 1 through 3 provided to the manipulation signal generation means800as the operational functions, it is also possible to provide the control device200with a function of, for example, preventing the manipulation signal So from varying rapidly using a variation rate limiter, or a function of limiting the value of the manipulation signal within a predetermined range using an upper and lower limiter.

In the step1050of transmitting the manipulation signal to the plant and receiving the manipulation result to which the process proceeds via either one of the manipulation signal generation steps1020,1030, and1040to which the process proceeds based on the mode A, B, or C determined in the mode discrimination step, the manipulation signal22generated in either one of the manipulation signal generation steps1020,1030, and1040and transmitted from the manipulation signal generation means800is then transmitted to the plant100via the external output interface220as the manipulation signal23.

As a result of providing the manipulation signal23to the plant100, the measurement signal1as a state variable showing the operation state is then acquired from the plant100, and stored in the measurement signal database230of the control device200.

In the step1060of evaluating the manipulation result and determining the next mode to which the process proceeds via the step1050, the manipulation result evaluation means400provided to the control device200evaluates the manipulation result responsive to the manipulation of the plant100using the measurement signal3stored in the measurement signal database230, and determines the next mode.

As described above, the initial mode of the drive mode for controlling the plant100is the mode A set in the initial mode determination step1000.

Then, the drive mode makes the transition to the mode B for generating the manipulation signal using the learning result by the learning signal generation means600in combination therewith.

In the case in which the drive mode makes the transition to the mode B, the manipulation result evaluation means400calculates a first deviation E1as a deviation of the a measurement signal Sm1acquired as a result of applying a certain manipulation signal22a1to the plant from the target value Sa of the measurement signal Sm1, and a second deviation E2as a deviation of the second measurement signal Sm2acquired from the plant100as a result of applying an updated manipulation signal22a2to the plant100from the target value Sa of the measurement signal Sm2based on formulas 4 and 5 using a first measurement signal Sm1, a second measurement signal Sm2, and the target value Sa.

Here, E1denotes the first deviation, E2denotes the second deviation, Sm1denotes the first measurement signal, Sm2denotes the second measurement signal, and Sa denotes the target value of the measurement signals.

An average value of a certain period of time or an instantaneous value is user as the measurement signals Sm1, Sm2.

If the second deviation E2is larger than the first deviation E1, the drive mode makes the transition to the mode C, and if the second deviation E2is smaller than the first deviation E1, the drive mode becomes the mode B.

In other words, if the control characteristic becomes worse (the deviation of the measurement signal from the target value increases) as a result of application of the updated manipulation signal to the plant100, the drive mode makes the transition to the mode C, and the manipulation signal generation means800calculates the manipulation signal22using the correction signal18generated by the correction signal generation means700.

As described later, the correction signal generation means700generates the correction signal18so as to maintain the control characteristic in a preferable condition.

As a result, an advantage of improving the control performance of the plant can be obtained.

Further, in the manipulation signal generation step1040, it is possible to calculate the manipulation signal22using the deviations E1, E2calculated by the formulas 4 and 5 of the operational functions, or based on formulas 6 through 8, besides the method of calculating the manipulation signal22using the formula 3 provided to the manipulation signal generation means800as the operational function.

It should be noted that α and β denote weighting parameters, and ε denotes a predetermined design parameter.
So=Sb+α×Sl+β×Sr(6)
α←α−ε(E2−E1)  (7)
β←β−ε(E2−E1)  (8)

Here, the formula 6 means that the value of α is updated with the value obtained by subtracting ε(E2−E1) from the previous value of α.

By calculating the manipulation signal22using the formulas 6 through 8 provided to the manipulation signal generation means800as the operational functions, the larger the value of E2−E1is, the larger the value of β as the weighting parameter of the correction signal Sr becomes, and the more significant the influence of the value of the correction signal18generated by the correction signal generation means700on the manipulation signal22generated by the manipulation signal generation means800becomes.

FIG. 3is a setting screen of information to be stored in a correction signal calculation database260in the control device200as the embodiment of the control device for a plant shown inFIG. 1.

Further, the correction signal generation means700of the control device200calculates the correction signal18using the information stored in the correction signal calculation database260, which is a variety of kinds of information set on the screen shown inFIG. 3.

By using the screen shown inFIG. 3, the operator of the plant100can arbitrarily set which one of the following functions is used for every manipulation terminal, namely a function of increasing the value of the manipulation signal, a function of decreasing the value of the manipulation signal, a function of keeping the value of the manipulation signal as it stands, a function of resetting the value of the manipulation signal, a function of matching the value of the manipulation signal and a predetermined value, and a function of calculating the value of the manipulation signal based on the model characteristic variable.

Further, it is also possible to set the manipulation range of the manipulating variable for every manipulation terminal.

As the model characteristic variables, there can be cited model parameters stored in the model construction database240of the control device200, deviation peak information of the model output characteristic curve, and so on.

FIGS. 4A through 4F,5A, and5B are diagrams for explaining respective operations of the correction signal generation means700provided to the control device200as the embodiment of the control device for a plant shown inFIG. 1.

FIGS. 4A through 4Deach have the horizontal axis representing the manipulating variable applied to the model or the actual equipment, and the vertical axis representing the controlled variable of the model or the actual equipment, and show an example illustrating the model characteristic and the learning result of the model620in the control device200of the present embodiment.

It should be noted thatFIGS. 4A through 4Dshow diagrams assuming the case in which the learning means610of the control device200searches the manipulation condition in which the controlled variable of the model becomes the minimum in the present embodiment.

InFIG. 4A, α1in the horizontal axis represents the present manipulating variable, and β1represents the manipulating variable after the learning (searching) has been executed.

As shown inFIG. 4A, by changing the manipulating variable from α1to the manipulating variable β1after the learning (searching) has been executed, the controlled variable illustrated by the model characteristic curve is reduced on the model620.

Therefore, if the model characteristic and the plant characteristic of the plant as the actual equipment match each other, by updating the manipulating variable from α1to β1, the controlled variable of the plant100corresponding to the manipulating variable should be reduced.

However, in the case in which the model characteristic and the plant characteristic of the actual equipment do not match each other because of the model error, there is a possibility that the controlled variable of the plant100increases to the contrary if the plant100is manipulated using the learning result.

FIG. 4Bshows an example in which the model characteristic curve rises to increase the controlled variable of the plant100as a result of updating the manipulating variable from α1to β1, the value after the learning has been performed.

Incidentally, the degradation in the control characteristic caused by the model error can be suppressed by correcting the model using the newly obtained measurement signal1of the plant100to decrease the model error, and then relearning the manipulation method to the corrected model620by the learning means610of the control device200taking the corrected model620as an object.

However, in the case in which this method is used, it often takes a long period of time to accumulate a number of data of the measurement signal1for correcting the model620, and during the period of time for accumulating the data, the expected control performance cannot be exerted.

In particular in the case it is not allowed to operate the plant in a condition with an improper control characteristic for a long period of time, it is difficult to adopt the method described above.

In view of the above circumstances, the correction signal generation means700provided to the control device200of the present embodiment is for solving the problem of the method described above.

Specifically, in the control device200of the present embodiment, if the controlled variable of the plant100as the controlled object increases when the manipulating variable to the model620is updated from α1to β1, the drive mode of the control device200is switched from the mode A as the initial mode to the mode C (seeFIG. 2).

In the mode C thus switched to, the correction signal generation means700provided to the control device200generates the correction signal18for maintaining the preferable control characteristic, and the manipulation signal generation means800generates the manipulation signal22to be a command signal to the plant100as the controlled object based on the correction signal18.

The correction signal generation means700as a function of generating the correction signal18using the model characteristic curve shown inFIG. 4A.

Specifically, the correction signal generation means700calculates the number of deviation peaks of the model characteristic curve based on the model characteristic curve, and calculates the correction signal18based on the number of the deviation peaks.

Then, if the number of the deviation peaks of the model characteristic curve is an even number, the manipulating variable is decreased, and if it is an odd number, the manipulating variable is increased.

The reason that the method described above decreases the controlled variable and make the model characteristic come closer to a desired characteristic will hereinafter be explained with reference toFIGS. 4A through 4F.

Firstly, the case in which the number of the deviation peaks of the model characteristic curve existing between the values α1and β1of the manipulating variable is an even number as shown inFIG. 4Awill be explained.

In an example of the model characteristic shown inFIG. 4A, the number of deviation peaks is 0, which is an even number.

In this case, if the deviation peak in the actual equipment characteristic illustrated with the solid line as an actual equipment characteristic curve is located between the values α1and β1of the manipulating variable as shown inFIG. 4B, the controlled variable corresponding to the manipulating variable of β1becomes larger than the controlled variable corresponding to the manipulating variable of α1.

Further, if the deviation peak in the actual equipment characteristic illustrated with the solid line as the actual equipment characteristic curve is located at a position corresponding to a value larger than β1, the situation shown inFIG. 4Cappears, the controlled variable corresponding to the manipulating variable of β1becomes smaller than the controlled variable corresponding to the manipulating variable of α1.

Here, in the case in which the actual equipment characteristic has the deviation peak between the values α1and β1of the manipulating variable as shown inFIG. 4B, the controlled variable can be reduced by reducing the manipulating variable.

In other words, if the number of deviation peaks of the model characteristic curve illustrated with the broken line is an even number, the controlled variable of the plant100can be reduced by reducing the manipulating variable so as to come closer to the value α1.

Then, the case in which a model having a different model characteristic curve is used as the model620, and the number of the deviation peaks of the model characteristic curve existing between the values α2and β2of the manipulating variable is an odd number as shown inFIGS. 4D through 4Fwill be explained.

In an example shown inFIG. 4D, the number of deviation peaks is 1, which is an odd number.

In this case, as shown inFIG. 4E, if the position of the deviation peak in the actual equipment characteristic curve illustrated with the solid line is shifted from the deviation peak of the model characteristic curve illustrated with the broken line towards the value β2of the manipulating variable, the controlled variable corresponding to the manipulating variable of β2becomes larger than the controlled variable corresponding to the manipulating variable of α2.

Further, in contrast, if the position of the deviation peak in the actual equipment characteristic curve is shifted from the deviation peak of the model characteristic towards the value α2of the manipulating variable, the actual equipment characteristic curve becomes as illustrated with the solid line inFIG. 4F, the controlled variable corresponding to the manipulating variable of β2becomes smaller than the controlled variable corresponding to the manipulating variable of α2.

According to this fact, in the case in which the actual equipment characteristic is represented by the actual equipment characteristic curve shown inFIG. 4E, the controlled variable corresponding to the manipulating variable can be reduced by increasing the manipulating variable.

In other words, if the number of deviation peaks of the model characteristic curve is an odd number, the controlled variable of the plant100can be reduced by increasing the manipulating variable.

It should be noted that inFIGS. 4A through 4F, the case in which the number of the deviation peaks of the model characteristic curve is an even number shown inFIGS. 4A through 4Cis described on the left as a pattern1, and the case in which the number of the deviation peaks of the model characteristic curve is an even number shown inFIGS. 4D through 4Fis described on the right as a pattern2.

Therefore, the correction signal generation means700is arranged to generate the correction signal18for increasing or decreasing the manipulating variable using the information of the number of deviation peaks of the model characteristic curve described above to output the correction signal to the manipulation signal generation means800.

Further, by displaying the graphs emphasizing the positions of the deviation peaks of the model characteristic curve as shown inFIGS. 4A and 4Dand the number of deviation peaks of the model characteristic curve on the image display device950of the maintenance tool910attached to the control device200shown inFIG. 1, it becomes possible for the operator of the plant100to understand the grounds for generation of the correction signal18generated by the correction signal generation means700, and to evaluate the validity of the correction signal18.

FIGS. 5A and 5Bare diagrams for explaining the operation of learning the most appropriate manipulation method directed to the plant100by the correction signal generation means700in the control device200of the present embodiment.

The search range for learning is determined by the learning means610and the model620of the control device200combined with each other.

The learning means610sets the predetermined range of threshold value as the range of trial-and-error centering around the manipulation condition with which the deviation between the model output and the target value becomes minimum as in the model characteristic in the case of controlling the plant100illustrated with the solid line inFIG. 5Awith the horizontal axis representing the manipulating variable and the vertical axis representing the controlled variable.

Further, the correction signal generation means700sets the search range of the manipulating variable in which the manipulation signal is varied within the range of trial-and-error determined by the learning means, and calculates the manipulation signal so that the deviation between the measurement signal of the plant100and the target value of the measurement signal becomes the minimum.

Then, the learning result by the learning means610is stored in the learning information database250in a form shown inFIG. 5B, for example.

FIG. 5Bmeans that the correction signal generation means700generates the correction signal18for reducing the manipulating variable if the controlled variable is larger than γ1, or generates the correction signal18for increasing the manipulating variable if the controlled variable is smaller than γ1.

By displaying the graph of the correction signal shown inFIG. 5Bon the image display device950, it becomes possible for the operator of the plant100to understand the grounds for generation of the correction signal18, and to evaluate the validity of the correction signal18.

FIG. 6is a diagram for explaining the interface for changing the range of trial-and-error, in which the manipulation signal is varied, performed by the correction signal generation means700provided to the control device200of the present embodiment.

Using various kinds of information displayed on the screen shown inFIG. 6, the search range of the manipulating variable explained with reference toFIGS. 5A and 5Bcan be set manually as shown in the screen shown inFIG. 6as a search range based on the manual correction in comparison with the search range based on the threshold value.

As a result, by the operator of the plant100having a good knowledge thereof setting the search range ofFIGS. 5A through 5F, there can be obtained an advantage of operating the plant100safe even during the search operation of the optimum manipulation conditions.

According to the embodiment of the present invention described above, a control device for a plant capable of preferably maintaining the control characteristic of the plant even in the case in which the characteristic of the model for predicting the characteristic of the plant as a controlled object is different from the characteristic of the actual plant.

Second Embodiment

Then, a control device for a thermal power plant as a second embodiment of the present invention will be explained with reference to the accompanying drawings.

FIG. 7is a control block diagram showing an overall configuration of a control device for a thermal power plant as a second embodiment of the invention.

Further,FIGS. 8A and 8Bdescribed later show a schematic configuration of a thermal power plant equipped with a boiler using coal as the fuel as a thermal power plant to be the controlled object of the control device for a thermal power plant as the second embodiment of the present invention shown inFIG. 7.

Since the control device for a thermal power plant as the second embodiment shown inFIG. 7has a basic configuration common to the control device for a plant as the first embodiment shown inFIG. 1, the explanation for the constituents common thereto will be omitted, and only the constitutions different therefrom will hereinafter be explained.

In the control device for a thermal power plant shown inFIG. 7, the thermal power plant100aequipped with a boiler101using coal as the fuel is controlled by the control device200.

The control device200of the present embodiment acquires the measurement signal1as a result of measuring various state variables of the thermal power plant100asuch as the oxygen concentration or the carbon monoxide concentration of the combustion gas at the exit of the boiler101, and further, the control device200outputs the manipulation signal23for controlling, for example, a burner102of the boiler101and the air flow rate of the air port103to the thermal power plant100adescribed above via the external output interface220.

By performing control taking at least one of opening of an air damper, an air flow rate, a fuel flow rate, and an exhaust gas recirculation flow rate of the boiler101provided to the thermal power plant100aas an object using the control device200of the present embodiment, it becomes possible to control at least one of the concentration of nitrogen oxide, the concentration of carbon monoxide, the concentration of carbon dioxide, the concentration of sulfur oxide, and the concentration of mercury included in the exhaust gas emitted from the thermal power plant100ato a desired value.

The model620forming the control device200in the present embodiment is configured to input the model construction data6stored in the model construction database240such as the opening of an air damper, the air flow rate, the air temperature, the fuel flow rate, and the exhaust gas recirculation flow rate and execute predicting calculation to output the values of the concentration of nitrogen oxide, the concentration of carbon monoxide, the concentration of carbon dioxide, the concentration of sulfur oxide, and the concentration of mercury at that moment.

The control device for a thermal power plant as the second embodiment shown inFIG. 7is different from the control device for a plant as the first embodiment shown inFIG. 1in that there is provided a plurality of learning means610and models620to the control device200of the second embodiment shown inFIG. 7.

The control device200of the present embodiment is provided with a plurality of learning means610and models620as described above, thereby coping with switching of the operation conditions of the thermal power plant100a.

In the thermal power plant100a, when executing the operation of changing a burner pattern, a load level, or a coal type, the plant characteristic is changed dramatically.

As a method of keeping the operation condition of the thermal power plant100ain a preferable state even in the case in which the plant characteristic has dramatically been changed, the control device200of the present embodiment is configured to be provided with a model switching means630, in which a plurality of models620corresponding respectively to various types of operation conditions is prepared, and further a plurality of learning means610adapted to learn manipulation methods directed to the respective models620prepared corresponding respectively to the various types of operation conditions is also disposed.

Further, the number of the types of the learning information data9obtained by the respective learning means610prepared directed to the models620provided for the respective operation conditions in the present embodiment corresponds to the number of types of the models620.

Further, the learning results obtained by the learning in the respective learning means610are stored in the learning information database250.

Further, determination of which learning result is used when the leaning signal generation means600generates the learning signal16, namely discrimination of the present operation condition of the plant, is performed by the manipulation result evaluation means400.

FIGS. 8A and 8Bshow a schematic configuration of a thermal power plant equipped with a boiler using coal as the fuel to be the controlled object of the control device for a thermal power plant as the second embodiment of the present invention shown inFIG. 7.

Firstly, a configuration of electric power generation of the thermal power plant100aequipped with the boiler101will be explained with reference toFIG. 8A.

InFIG. 8A, the coal to be the fuel is pulverized by the mill into pulverized coal and fed into the boiler101together with primary air for carrying the coal and secondary air for combustion control via the burners102provided to the boiler101, and is burnt as the fuel inside a furnace of the boiler101.

The fuel coal and the primary air is introduced to the burner102via a pipe134, and the secondary air is introduced there via a pipe141.

Further, after air for two-stage combustion is fed into the boiler101via after-air ports103provided to the boiler101. The after air is introduced to the after-air ports103from a pipe142.

A hot combustion gas generated by burning the fuel coal inside the furnace of the boiler101flows in the furnace of the boiler101along a path indicated by the arrow towards a downstream side, passes through a heat exchanger106provided to the boiler101to be heat-exchanged, and then is emitted from the boiler101as a combustion exhaust gas to flow down to an air heater104disposed outside the boiler101.

After the combustion exhaust gas passes through the air heater104, harmful materials included in the combustion exhaust gas are removed by a gas treatment device, not shown, and then, the combustion exhaust gas is vented to the air from a stack.

Water supply circulating the boiler101is introduced in the boiler101via a water supply pump105from a condenser, not shown, provided to a turbine108, and heated by the combustion exhaust gas flowing down inside the furnace of the boiler101in the heat exchanger provided to the furnace of the boiler101to be a high-temperature and pressure steam.

It should be noted that although in the present embodiment, the drawing is made assuming that the number of the heat exchangers106is one, it is also possible to dispose a plurality of heat exchangers.

The high-temperature and pressure steam generated in the heat exchanger106is introduced into the steam turbine108via a turbine governor valve107to drive the steam turbine108with the energy the steam have, and rotates the generator109coupled to the steam turbine108to generate electric power.

Then, channels of the primary and the secondary air fed into the furnace of the boiler101from the burners102provided to the furnace of the boiler101, and the after air fed into the furnace of the boiler101from the after-air ports103provided to the furnace of the boiler101will be explained.

The primary air is introduced from a fan120to a pipe130, branched in midstream into a pipe132passing through the air heater104and a pipe bypassing the air heater104, and flows down the pipes132and131. Then the primary air flows into each other again at a pipe133, and is guided into the mill110.

The air passing through the air heater104is heated by the combustion exhaust gas emitted from the furnace of the boiler101.

The coal (the pulverized coal) generated by the mill110is carried using the primary air to the burner102via the pipe133.

It is arranged that the secondary air and the after air are introduced into a pipe from a fan121, heated while flowing down the pipe140passing through the air heater104, then, branched at the downstream side of the pipe140into a pipe141for the secondary air and a pipe142for the after air, and introduced respectively into the burners102and the after-air ports103provided to the furnace of the boiler101.

The control device200of the thermal power plant100aequipped with the boiler as the present embodiment has a function of controlling an amount of air fed from the burners102into the boiler101and an amount of air fed from the after-air ports103into the boiler101in order for reducing the concentrations of NOx and CO in the exhaust gas of the boiler.

The thermal power plant100ais provided with a variety of kinds of measurement equipment for detecting the operation conditions of the thermal power plant100a, and the measurement signals of the plant acquired from the measurement equipment are transmitted to the control device200as the measurement signal1.

As the a variety of types of measurement equipment for detecting the operation conditions of the thermal power plant100a, there are illustrated inFIG. 8A, for example, a flow meter150, a thermometer151, a pressure meter152, a power generation output meter153, and a concentration meter154for measuring the concentration of O2, the concentration of CO, or both of the concentrations of O2and CO.

The low meter150measures the flow rate of the water supply supplied from the water supply pump105to the boiler101. Further, the thermometer151and the pressure meter152respectively measure the temperature and the pressure of the steam generated by the heat-exchange with the combustion exhaust gas flowing down the boiler101in the heat exchanger106provided to the boiler101and supplied to the steam turbine108.

The electric energy generated by the generator109rotated by the steam turbine108driven by the steam generated by the heat exchanger106is measured by the power generation output meter153.

Further, the information regarding the concentrations of the components (e.g., CO, NOx) included in the combustion exhaust gas flowing down the boiler101is measured by the a concentration meter154for measuring the concentration of O2, the concentration of CO, or both of the concentrations of O2and CO disposed on the channel at the exit of the boiler on the downstream side of the boiler101.

It should be noted that although the thermal power plant100ais generally provided with a number of pieces of measurement equipment besides those shown inFIG. 8A, illustration thereof will be omitted here.

FIG. 8Bis a partial enlarged view showing the air heater104disposed on the downstream side of the boiler101forming the thermal power plant100a, and the pipes provided to the air heater104.

As shown inFIG. 8B, the pipe141for the secondary air and the pipe142for the after air branched from the pipe140disposed inside the air heater104on the downstream side thereof, the pipe132disposed inside the air heater104, and the pipe131bypassing the air heater104are provided respectively with the dampers162,163,161, and160.

Further, by manipulating these dampers160through163, the areas of the pipes131,132,141, and142through which the air passes are varied, and the rate of the airflow passing through each of the pipes131,132,141, and142is controlled individually.

Further, using the manipulation signal18generated by the control device200for controlling the thermal power plant100aand output to the thermal power plant100a, devices such as the water supply pump105, the mill110, and the air dampers160,161,162, and163are manipulated.

It should be noted that in the control device for the thermal power plant as the present embodiment, the devices for controlling the state variables of the thermal power plant such as the water supply pump105, the mill110, and the air dampers160,161,162, and163are referred to as manipulation terminals, and the command signals necessary to control the manipulation terminals are referred to as manipulation signals.

Further, it is also possible to add a function capable of moving the discharge angle of the air for combustion and so on or the fuel such as the pulverized coal to left, right, up, and down when feeding the air and the fuel into the boiler101to the burners102and the after-air ports103, and to include the command signals for controlling the attachment angles of the burners102and the after-air ports103in the manipulation signals18described above.

Then, the discrimination method of the plant operation conditions by the manipulation result evaluation means400provided to the control device200of the present embodiment will be explained with reference toFIG. 9A through 9C.

InFIGS. 9A through 9C, the manipulation result evaluation means400has a function of figuring out the burner pattern of the boiler based on the value of the measurement signal of flow rate of the coal supplied to the mill110, a function of figuring out the load level based on the output demand or the value of the measurement signal of the output of the generator109, and a function of figuring out the coal type based on the value of the measurement signal of a rotational frequency of a mill classification machine.

FIG. 9Ais a diagram for explaining the function of figuring out the burner pattern of the boiler101by the manipulation result evaluation means400.

At time t1on the horizontal axis representing time, as shown on the vertical axis representing coal flow rate, mills A, B, and D forming the mill110supply the coal, and supply of the coal from mill C starts from a boundary of time t2(e.g., at time t3, the coal is supplied from all of the mills A, B, C, and D).

As illustrated in the schematic diagram of the boiler shown in the right of theFIG. 9A, each of the mills A, B, C, and D supplies five burners disposed along the horizontal direction on the furnace front or the furnace rear of the boiler101with the coal.

The manipulation result evaluation means400can figure out the burner pattern from the amounts of coal supplied respectively from the mills A, B, C, and D shown inFIG. 9A, which are detected as the measurement signal3of the thermal power plant100avia the measurement signal database230, and a correspondence between the mills A, B, C, and D and the five burners provided to the boiler101.

By figuring out the burner pattern described above, it becomes possible to figure out the combustion condition inside the furnace of the boiler101.

FIG. 9Bis a diagram for explaining the function of figuring out the load level of the thermal power plant100aby the manipulation result evaluation means400.

The generator output is obtained by measuring the amount of power generation of the generator109by the power generation output meter shown inFIG. 8A, andFIG. 9Bshows that at time t4on the horizontal axis representing time, the amount of the generator output of the thermal power plant100arepresented by the vertical axis is M4, and at time t5, the amount of the generator output is M5.

As described above, the load level of the thermal power plant100acan be figured out based on the value of the measurement signal of the generator output measured by the power generation output meter153.

FIG. 9Cis a diagram for explaining a first coal type discrimination method used for the fuel of the boiler101of the thermal power plant100aby the manipulation result evaluation means400.

Regarding the mill classification machine for supplying the boiler101with the pulverized coal obtained by pulverizing the fuel coal provided to the mill110of the thermal power plant shown inFIG. 8A,FIG. 9Cshows that at time t6on the horizontal axis representing time, the rotational frequency represented by the vertical axis is R6, and at time t7, the rotational frequency is R7.

The rotational frequency is controlled so that the grain size of the pulverized coal as the fuel supplied to the boiler101from the mill110becomes a target value.

Since the hardness of coal is different between the coal types, the rotational frequency of the classification machine when the grain size of the pulverized coal matches the target value should be different between the coal types.

Therefore, the coal type of the coal supplied to the boiler101can be discriminated based on the rotational frequency of the classification machine.

The learning signal generation means600of the control device200generates the learning signal16under the following procedure.

Firstly, the manipulation result evaluation means400generates the flag13corresponding to the plant operation conditions determined by the function of figuring out the burner pattern based on the measurement signal3of the thermal power plant100aobtained via the measurement signal database230, the function of figuring out the load level based thereon, and the function of figuring out the coal type based thereon, and outputs the flag13to the learning signal generation means600.

The model620, using the model620corresponding to the plant operation conditions determined by the manipulation result evaluation means400, makes the leaning means610corresponding to this model620generate the learning information data9obtained by learning and output it to the learning signal generation means600as the learning information data11via the learning information database250.

The learning signal generation means600is configured to generate the learning signal16by calculation based on the flag13and the learning information data11, and to output the learning signal16to the manipulation signal generation means800.

FIGS. 10A and 10Bare diagrams for explaining a second coal type discrimination method in the manipulation result evaluation means400provided to the control device200of the present embodiment.

InFIG. 10A, the manipulation result evaluation means400calculates the weight between the plurality of models620prepared correspondingly to the various operation conditions in the model switching means630based on information of coal composition, the correction signal generation means700looks up the weight value of the model620thus calculated and the learning result of the learning means610to generate the correction signal18using a formula 9 provided to the correction signal generation means700as an operational function.

Here, i satisfies 1≦i≦n, n denotes the number of coal types, di denotes the distance between the ith coal and the actual sample value, and Si denotes the value of the learning signal generated along the learning result using the ith coal model.

The formula 9 means that the value obtained by adding all of the values (Si/di) within the range of 1≦i≦n is divided by the value obtained by adding all of the values (1/di) within the range of 1≦i≦n.
So=Σ(Si/di)/Σ(1/di)  (9)

It should be noted that the distance di is obtained using the calculation algorithm of Euclidean distance and Mahalanobis distance.

In the drawing of a first component and a second component shown inFIG. 10A, the actual sample value as the object of the coal type discrimination has heavier weight of a sample value of a coal type A than weight of a sample value of a coal type B by taking the inverses of the distance d1from the sample value of the coal type A and the distance d2from the sample value of the coal type B as the weight thereof in view of the relationship between the distances d1, d2.

Therefore, by executing calculation on the models620with the respective weight values attached thereto, the manipulation result evaluation means400can determines the coal type of the actual sample.

Further, as illustrated in the schematic diagram of the boiler shown in the left ofFIG. 10B, in the case in which the coal containing more sulfur content than a threshold value is used as the fuel of the boiler101, the correction signal generation means700generates the correction signal18so as to increase the values of the flow rates of the air supplied from the burners and the air ports on the furnace wall of the boiler101, and outputs the correction signal18to the manipulation signal generation means800.

The manipulation signal generation means800generates the manipulation signal22based on the correction signal18, and outputs the manipulation signal22via the external output interface220as the manipulation signal23to the thermal power plant100afor performing the control.

It should be noted that the graph of the air flow rate shown in the right ofFIG. 10Bschematically shows the state of the flow rates of air supplied from the burners and air ports on the furnace wall illustrated in the schematic diagrams of the boiler shown in the left ofFIG. 10B.

In particular in the case of using the coal with much sulfur content as the fuel, it becomes important to control the air flow rate so as to prevent the corrosion of the furnace wall of the boiler101.

Further, as shown inFIG. 10B, in the case of using the coal with much sulfur content as the fuel of the boiler101, the control device200of the present embodiment can prevent the corrosion of the furnace wall along the furnace wall from the burners102and the air ports103disposed on the furnace wall of the boiler101by generating the correction signal18in the correction signal generation means700so as to increase the air flow rate on the furnace wall of the boiler101.

FIGS. 11A through 11Dare explanatory diagrams for explaining the operation of the control device200in the control device for a thermal power plant as the second embodiment of the present invention shown inFIGS. 7,8A, and8B.

FIG. 11Ais a diagram showing an example of the characteristic of the model620provided to the control device200of the present embodiment, and the learning means610provided corresponding to the model620learns the manipulation condition with which the concentration of CO is minimized using the model620as an object.

For example, by using the reinforcement learning when implementing the learning means610in the control device200, and setting it so that the lower the CO concentration is, the greater the reward becomes, it is possible to learn the manipulation method of achieving the manipulation condition (the manipulation condition y shown inFIG. 11A) with which the CO concentration becomes the minimum.

As showing the relationship between the manipulation condition represented by the horizontal axis and the CO concentration represented by the vertical axis inFIG. 11A, the variation in the CO concentration with respect to the variation in the manipulation condition is large in the vicinity of the manipulating condition y.

In the case in which the air flow rate is the manipulation condition, since the flow rate of the air fed into the boiler101varies temporally, even if the manipulation signal is matched with the manipulation condition y, there is a possibility that the flow rate of the air actually fed into the boiler varies to increase the CO concentration.

In order for avoiding such a phenomenon, the control device200of the present embodiment can adopt the method described below when operating the learning means610.

Specifically, the reinforcement learning is adopted when implementing the learning means610in the control device200, and the reward obtained by adding a first reward, which becomes the greater when the CO concentration is the lower, and a second reward, which takes a negative value when a formula 10 provided to the learning means610as an operational function is satisfied, is used.

It should be noted that in the formula 10, CO(I) denotes an estimated value (a model output) of the CO concentration with the manipulation condition of I, Δ denotes a minute value, and Ω denotes a predetermined threshold value.
ABS(CO(I)−CO(I+Δ))/Δ>Ω  (10)

By adopting the reward described above to the learning means610, it is possible to learn the manipulation method achieving the manipulation condition (the manipulation condition x shown inFIG. 11A) with which the CO concentration becomes the minimum under the condition with a low rate of variation in the CO concentration.

This makes a contribution to a safe operation in the case of controlling the thermal power plant100a.

FIG. 11Bshows an embodiment (a control circuit) of the manipulation signal generation means800provided to the control device200in the present embodiment having the thermal power plant100aas the controlled object.

As shown in the control circuit ofFIG. 11B, in order for making the oxygen concentration at the exit of the boiler become a desired value, the control circuit forming the manipulation signal generation means800generates the manipulation signal related to the air flow rate by adding the output signal of a PI controller having the deviation between the measurement value of the oxygen concentration and the target value thereof as the input and the setting value of the air flow rate to each other.

Further, the manipulation signal generation means800determines the total air flow rate to be fed into the boiler101by calculation based on the manipulation signal of the air flow rate thus generated, and outputs the result as the manipulation signal.

Further, the correction signal18generated by the correction signal generation means700and input to the manipulation signal generation means800is reflected so as to input to the positions indicated as the correction signal a and the correction signal b in the control circuit forming the manipulation signal generation means800shown inFIG. 11B, for example.

Specifically, the correction signal a and the correction signal b are input respectively as the correction signal a for correcting the target value of the oxygen concentration and the correction signal b for correcting the air flow rate manipulation signal.

Further,FIG. 11Cshows an example of a method of generating the correction signal18in the correction signal generation means700provided to the control device200in the present embodiment.

As shown inFIG. 11C, the correction signal generation means700generates the correction signal18based on features of errors between the model characteristics of the models620and the actual equipment data of the thermal power plant100aas the controlled object.

Specifically, the correction signal generation means700estimates causes of the errors based on the features of the errors between the model characteristics of the models620and the actual equipment data of the thermal power plant100a, and generates the correction signal18based on the causes of the errors.

As the causes of the errors, there can be cited those caused by the momentum control of the air fed into the furnace of the boiler101from the after-air ports103provided to the furnace wall of the boiler101.

Therefore, the momentum control of the air fed into the furnace from the after-air ports103will be described.

FIG. 11Dis a schematic structural diagram of the after-air port provided to the furnace wall of the boiler101in the present embodiment.

InFIG. 11D, the air supplied to the after-airport103is supplied into the furnace via a nozzle181,182of the after-air port103.

The distribution of the air supplied from the nozzle181,182into the furnace can be changed by respectively operating the air dampers163a,163bforming a part of the air damper163shown inFIG. 8B.

Specifically, inFIG. 11D, when the position of the air damper163B moves rightward, the channel in the air damper163bis narrowed, and therefore, the flow rate of the air supplied from the nozzle182into the furnace is reduced.

In the thermal power plant100a, the flow rate, the flow velocity, and momentum of the air fed into the furnace from the after-air port are controlled by operating the air dampers163a,163bof the after-air port as described above.

The opening of each of the air dampers163a,163bof the after-air port103is manually manipulated to be a setting value.

Further, there is a possibility of causing an error between the air flow rate of the setting value and the air flow rate obtained as a manipulation result in the target air flow rate and the flow rate of the air actually fed into the boiler101.

Therefore, the model620of the control device200is configured to predict the carbon monoxide concentration and so on in the combustion exhaust gas emitted from the boiler101in the present setting values based on the setting values of the opening of the air dampers163a,163b.

Therefore, as described above, in the case in which an error is caused between the setting value of the flow rate of the air fed into the boiler101and the air flow rate obtained as the manipulation result, there is a possibility that the predicted value of the model620and the measurement value as the state variable of the thermal power plant100ado not match each other.

Therefore, the control device200of the present embodiment is configured that in the case in which the predicted value of the model and the measurement value from the thermal power plant100ado not match each other, the correction signal generation means700generates the correction signal18for correcting the opening of the air dampers163a,163bof the after-air port103so as to eliminate the error between the setting value of the flow rate of the air fed into the boiler101and the air flow rate obtained as the manipulation result, and input the correction signal18to the manipulation signal generation means800, and the manipulation signal generation means800then generates the manipulation signal22.

Further, it is also possible to display the value of the manipulation signal18on the image display device950shown inFIG. 7as a manipulation guidance value to be learned by the operator of the thermal power plant100a.

As described above, by controlling the opening of the air dampers163a,163bof the after-air port103using the control device200of the present embodiment, it is possible to control the concentration of nitrogen oxide, carbon monoxide, carbon dioxide, sulfur oxide, or mercury contained in the combustion exhaust gas emitted from the boiler to a desired value.

It should be noted that although the case in which the control device200controls the flow rate, the flow speed, the momentum, and so on of the air fed into the furnace from the after-air port103provided to the furnace wall of the boiler101is described in the present embodiment, it is also possible to apply the control device200to the control of the flow rate, the flow speed, the momentum, and so on of the air fed into the furnace from the burners102provided to the furnace wall of the boiler101.

According to the embodiment of the present invention described above, a control device for a thermal power plant capable of preferably maintaining the control characteristic of the plant even in the case in which the characteristic of the model for predicting the characteristic of the plant as a controlled object is different from the characteristic of the actual plant.

Third Embodiment

A gas concentration estimation device of another embodiment is directed to a coal-burning boiler provided to a thermal power plant, and a gas concentration estimation device adapted to perform an estimation process of the gas concentrations of CO and NOx included in an exhaust gas emitted from the coal-burning boiler using a neural network.

Regarding the materials of CO and NOx included in the exhaust gas emitted from the coal-burning boiler, there are provided limit values in the concentration in the exhaust gas based on the environmental restriction.

The gas concentration estimation device of a coal-burning boiler as the present embodiment is for estimating the concentration of CO and the concentration of NOx in the exhaust gas with respect to various operation conditions of the thermal power plant equipped with a coal-burning boiler.

A control system of a thermal power plant equipped with the coal-burning boiler of the present embodiment is for satisfying the environmental restriction on the exhaust gas, and at the same time, for planning the operation condition of the coal-burning boiler for maximizing the efficiency of the boiler based on the estimation values of the CO concentration and the NOx concentration corresponding to the various operation conditions (e.g., combustion flow rate and air flow rate) obtained from the gas concentration estimation device described above.

The gas concentration estimation device and a method thereof of the coal-burning boiler as the present embodiment will hereinafter be explained with reference to the accompanying drawings.

FIG. 12is a schematic diagram showing a configuration of a gas concentration estimation device of a coal-burning boiler as an embodiment of the invention.

The combustion control of the coal-burning boiler2004as a plant shown inFIG. 12is performed by a control system2002. Further, as a gas concentration estimation device2001of the coal burning boiler2004shown inFIG. 12, there is provided a gas concentration estimation device2001adapted to estimate the CO concentration and the NOx concentration in the exhaust gas emitted from the coal-burning boiler2004.

The gas concentration estimation device2001is provided with a process database (a process DB)2011for acquiring process data to be actual equipment data of the coal-burning boiler2004online via the control system2002and then storing the process data thus acquired in a time-series manner, a filtering processing section2012adapted to perform the filtering process for extracting data suitable for learning of a neural network from the process data stored in the process DB in a time-series manner, and a filtering processing result storage section2013for storing the result of the filtering processing by the filtering processing section2012.

Further, the gas concentration estimation device2001described above is further provided with a neural-network learning processing section2014for performing the neural-network learning processing for estimating the CO concentration, the NOx concentration, or both of the CO concentration and the NOx concentration in the exhaust gas emitted from the coal-burning boiler2004based on the data suitable for the neural-network learning thus extracted by the filtering processing and stored in the filtering processing result storage section2013, and a learning result storage section2015for storing coupling coefficients obtained in the learning processing by the neural-network learning processing section2014.

Further, the gas concentration estimation device2001is further provided with a neural-network estimation processing section2016for performing the estimation processing of the CO concentration, the NOx concentration, or both of the CO concentration and the NOx concentration in the exhaust gas emitted from the coal-burning boiler2004described above based on the learning processing of the neural-network learning processing section2014.

In the present embodiment of the invention, the coal-burning boiler2004as the controlled object is provided with the control system for performing the combustion control of the boiler, and it is configured that the control system2002sets the operation condition of the coal-burning boiler2004to the gas concentration estimation device2001, and the gas concentration estimation device2001calculates the estimation values of the CO concentration and the NOx concentration in the operation condition.

The gas concentration estimation device2001uses the process data of the coal-burning boiler2004acquired via the control system2002when estimating the CO concentration and the NOx concentration of the coal-burning boiler2004.

The process data of the coal-burning boiler2004acquired from the control system2002are stored to the process DB2011provided to the gas concentration estimation device2001and then stored therein in a time-series manner as described above.

Further, in the gas concentration estimation device2001, then the filtering processing section2012obtains the process data of the coal-burning boiler2004stored in the process DB2011in a time-series manner, and performs the filtering processing for extracting only the process data suitable for the neural-network learning.

In the filtering processing of the present embodiment, the data to be an error of the model is eliminated out of the process data of the actual equipment of the coal-burning boiler2004used for building the model, and then the learning of the model is performed. The filtering of the data to be a cause of an error is performed as described below.

In general, there is a plurality of types of data used as input of the model. Firstly, attention is focused on one input signal out of these data, and a plurality of combinations of data is extracted, the data having approximately the same input signal values except the datum of the input signal on which attention is focused.

Regarding the plurality of combinations of data, a trend of the data with respect to the variation of the input signal on which attention is focused is examined. On this occasion, if there is any data deviating from the trend, the data is eliminated from the learning data under the judgment that the data becomes the cause of an error in the modeling. The processing described above is executed for every data type used as the input signal.

Then, the specific content of the filtering processing in the filtering processing section2012will be explained.

The filtering processing section2012obtains the input signals used as the inputs of the neural network and the measurement values corresponding to the CO concentration and the NOx concentration as the estimation objects out of the process data of the coal-burning boiler2004stored in the process DB2011.

As the input signals of the neural network, there can be cited, for example, the primary air flow rate (primary air fan power or the like if the primary air flow rate is not measured) for combustion supplied to the coal-burning boiler2004, the secondary air flow rate therefor, the load of the coal-burning boiler, and a flow rate of a coal feeder for supplying the fuel coal.

Attention is focused on one of these input signals, as a first step, and the filtering processing section2012performs grouping of the process data stored in the process DB2011.

For example, in the case in which attention is focused on the signal of the coal feeder flow rate as the one of the signals in the first step, with respect to the signal values other than the coal feeder flow rate, the data having the difference within a predetermined threshold value range are defined as the same group.

In other words, in the case in which the signals other than the coal feeder flow rate are used as the input signals, the filtering processing section2012corrects and groups the data each having the signals of the primary air flow rate, the secondary air flow rate, and the boiler load showing approximately the same values within a predetermined value range although the value of the signal of the coal feeder flow rate is different.

Then, with respect to each of the groups thus grouped as described above, the filtering processing section2012graphs the relationship between the coal feeder flow rate as the input signal and the CO concentration and the NOx concentration as the object of the gas concentration to be estimated.FIGS. 13A and 13Bshow the concept of this processing.

FIGS. 13A and 13Bshow the graphing processing performed by the filtering processing section2012, and show the characteristic graphs obtained by plotting the data belonging to the same group assigning the coal feeder flow rate as the input signal to the horizontal axis and the NOx concentration as the object of the gas concentration to be estimated to the vertical axis.

Since the values of the signals other than the signal of the coal feeder flow rate are approximately the same values within the predetermined threshold value range as described above, it can be assumed that the signals other than the signal of the coal feeder flow rate are in the same conditions. In this case, the characteristic graphs show the dependency of the data on the coal feeder flow rate, namely the degree of relationship of influence exerted on the NOx concentration, and in the case shown inFIG. 13A, the degree of the relationship described above is large.

Subsequently, the filtering processing section2012executes function fitting on the data plotted of theFIGS. 13A and 13B.

The curved function2100illustrated inFIG. 13Ashows the fitting function obtained by the fitting processing.

Subsequently, the filtering processing section2012calculates the error between the fitting function2100and each of the data plotted on the graph.

Further, in the calculation by the filtering processing section2012, the data having the error exceeding a predetermined threshold value is judged to be the data including a large amount of error since the dependency on the coal feeder flow rate is different from those of the other data, and is eliminated from the data used for the modeling processing for learning the neural-network model in the neural-network learning processing section2014described later.

For example, in the case shown inFIG. 13A, if the error ΔE of the data2101exceeds a predetermined threshold value with respect to the curved function2100, it is judged that the error ΔE included in the data2101is large, and the data2101is eliminated from the data to be used in the modeling processing.

Subsequently, as is the case shown inFIG. 13B, the fitting processing is executed again on the data not eliminated in the fitting processing by the filtering processing section2012.

In the example ofFIG. 13B, there is shown a situation in which the fitting processing is executed after eliminating the data2101, and the curved fitting function2102is newly obtained.

Subsequently, the filtering processing section2012calculates the error between the new fitting function2102and each of the data plotted on the graph. Further, if there is any data with the error exceeding the predetermined threshold value, the data causing the error exceeding the predetermined threshold value is eliminated, and the fitting processing is executed again.

Further, if there is no data with the error exceeding the predetermined threshold value, the processing to this group is terminated. The same processing is executed on the other groups.

The processing explained above is executed with respect to each of the signals (the first air flow rate, the second air flow rate, and the boiler load besides the coal feeder flow rate in the example described above) set as the input signal to the neural-network model.

According to the filtering processing by the filtering processing section2012described above, the data having a large error and therefore becoming the cause of error in the model can be eliminated.

The result of the filtering processing by the filtering processing section2012is stored in the filtering processing result storage section2013.

Subsequently, the neural-network learning processing section2014performs the learning processing of the neural network for estimating the CO concentration and the NOx concentration based on the data, on which the filtering processing has already executed, stored in the filtering processing result storage section2013.

FIG. 14shows a configuration example of the neural network in the neural-network learning processing section2014.

In the configuration example of the neural network forming the neural-network learning processing section2014shown inFIG. 14, the coal feeder flow rate, the primary air flow rate, the secondary air flow rate, and the boiler load as the process data of the coal-burning boiler2004are provided to the neural network as the input signals therefor, and the CO concentration and the NOx concentration in the exhaust gas emitted from the coal-burning boiler2004are set as the output signal of the neural network.

By the learning processing in the neural network forming the neural-network learning processing section2014, the coupling coefficients representing the relationship between the input values and the output values on the neural network can be obtained.

The coupling coefficients obtained by the learning processing by the neural network in the neural-network learning processing section2014are stored in the learning result storage section2015.

The explanations described above is the content of the learning processing building the neural-network model for estimating the gas concentration (the CO concentration, the NOx concentration, or both of the CO concentration and the NOx concentration) in the exhaust gas emitted from the coal-burning boiler2004.

In the learning processing in the neural-network learning processing section2014, if the measurement data of the coal-burning boiler2004in various operation conditions are stored in the process DB2011, the real-time processing is not required.

Further, it is also possible that the learning processing described above is previously performed prior to executing the process for estimating the gas concentration (the CO concentration and the NOx concentration) in the neural-network estimation processing section2016described later, to prepare the neural-network model.

Then, the operation of the neural-network estimation processing section2016for estimating the concentration of the gas (the CO concentration, the NOx concentration, or both of the CO concentration and the NOx concentration) included in the exhaust gas of the coal-burning boiler2004using the neural-network model built by the learning processing of the neural-network learning processing section2014will be explained.

The control system2002of the thermal power plant2004equipped with the coal-burning boiler shown inFIG. 12performs optimization of the combustion control of the coal-burning boiler2004in order for reducing the CO concentration, the NOx concentration, or both of the CO concentration and the NOx concentration as the concentration of the gas included in the exhaust gas of the coal-burning boiler2004and on which the environmental regulation values are set.

In the process of optimizing the combustion control, an operation condition setting section2003provided to the control system2002changes the process value corresponding to the control condition out of the process values set to the input of the neural network based on the command signal from the control system2002.

For example, in the case of analyzing the trend of variation of the CO concentration or the NOx concentration in accordance with variation of the primary air flow rate, the operation condition setting section2003operates so as to change only the value of the primary air flow rate out of the input signals of the neural network and set the values of the other input signals (e.g., the coal feeder flow rate, the secondary air flow rate, and the boiler load) as they stands.

In this case, the control system2002determines the optimum control method of the boiler combustion in the coal-burning boiler based on the estimation values (in the example described above, the trend of variation in accordance with the primary air flow rate as the input signal can be found out) of the CO concentration or the NOx concentration obtained by the estimation processing of the neural-network estimation processing section2016.

As the optimum control method of the boiler combustion, it is possible, for example, to perform combustion control of the boiler while controlling the combustion air flow rate or changing the combustion patterns of the boiler.

It is arranged that the result of the processing by the neural-network estimation processing section2016is displayed on the display device2005shown inFIG. 12so that the result can be confirmed.

FIGS. 15A and 15Bshows an example of display on the display device2005provided to the present embodiment shown inFIG. 12. The display example of the display device2005illustrated inFIG. 15Ashows the data2101eliminated by the filtering processing of the filtering processing section2012.

Further, in the display example of the display device2005shown inFIG. 15B, the estimated value of the neural-network model corresponding to the NOx concentration obtained by the learning processing of the neural-network estimation processing section2016of the present embodiment is illustrated with the dot line, and further, the trend of the estimation value of the NOx concentration corresponding to elapse of time is also displayed.

Further, in the display example shown inFIG. 15B, both of the actual measurement value of the NOx concentration illustrated with the solid line and the trend of the estimation value by the neural-network model illustrated with the dot line are displayed in a form of comparing the both values with each other.

According to the present embodiment described hereinabove, it become possible to perform the estimation processing of the CO concentration, the NOx concentration, or both of the CO concentration and the NOx concentration in the exhaust gas for optimizing the combustion control of the boiler by the control system with high accuracy.

Therefore, according to the embodiment of the present invention, there can be provided a gas concentration estimation device of a coal-burning boiler and a gas concentration estimation method each suppressing an estimation error of a neural-network model caused by a measurement error included in actual equipment data in the case in which the variation in the concentration of CO or the concentration of NOx in the exhaust gas is simulated using a neural network in combustion control of the coal-burning boiler, thereby making it possible to estimate the gas concentration with high accuracy.

The present invention as an embodiment can be applied to a control device for a plant and to a control device for a thermal power plant equipped with a boiler.

The present invention as another embodiment can be applied to a gas concentration estimation device and a gas concentration estimation method of estimating the concentration of CO or NOx as a gas component included in the exhaust gas emitted from a coal-burning boiler.