JP2022104052A - Control device and control method - Google Patents

Abstract

To provide a control device and a control method capable of contributing to maintenance of the frequency of an electric power system by having a good followability to AFC signals.SOLUTION: A control target of a control device is a thermal power plant including a turbine bypass valve for adjusting the amount of steam that bypasses a steam turbine driven by steam from a boiler. The control device controls the turbine bypass valve on the basis of a turbine bypass valve opening degree command value and controls the boiler on the basis of a boiler input command value. The turbine bypass valve opening degree command value is generated on the basis of an AFC signal in an AFC response mode of the thermal power plant. The boiler input command value is generated by adding a positive bias value to a base input value based on a load command value for the thermal power plant in the AFC response mode.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a control device and a control method.

A thermal power plant that drives a steam turbine using steam generated by a boiler (steam generator) is known. This type of thermal power plant may have a turbine bypass valve on a bypass line configured to bypass the steam turbine with respect to the line for supplying steam from the boiler to the steam turbine. The turbine bypass valve typically contributes to shortening the start-up time by controlling the opening before starting the steam turbine, or opens when the steam pressure in the steam turbine rises excessively to open the steam pressure. It is used to suppress the rise of.

By the way, as such a thermal power plant, an electric power company operating a thermal power generation plant for generating power using the output of a steam turbine supplies the voltage and frequency of the generated power based on the Electricity Business Law. There is an obligation to strive to maintain the values specified in advance for the previous power system. The electric power company controls the boiler output based on the load command value provided by the central power supply command center according to the supply and demand conditions in the power system and the AFC (Automatic Frequency Control) signal corresponding to the relatively fast frequency fluctuation. Was supported by.

However, in a thermal power plant using a boiler with low responsiveness such as a coal boiler, it is difficult to obtain good followability to a component corresponding to a relatively fast frequency fluctuation such as an AFC signal. In response to such conventional problems, for example, in Patent Document 1, when the above-mentioned turbine bypass valve is kept in a fully closed state during normal operation and an AFC signal is received, an AFC signal is given to a load command value. It has been proposed to improve the followability to the AFC signal by generating the boiler input command value obtained by adding the above and controlling the opening degree of the turbine bypass valve in proportion to the AFC signal.

Japanese Unexamined Patent Publication No. 59-145309

In Patent Document 1, when the AFC signal is received, the AFC signal is added to the load command value to generate the boiler input command value. Therefore, the value is larger than the load command value while the AFC signal is positive. A boiler input command is obtained. On the other hand, when the AFC signal is negative, the boiler input signal is smaller than the load command value, and the adjustment allowance for controlling the opening of the turbine bypass valve corresponding to the AFC signal is small, so that the AFC signal changes significantly. It becomes difficult to deal with it. Further, in Patent Document 1, a boiler input signal is obtained by adding an AFC signal to a load command value, but as described above, it is not enough for the boiler input signal to be reflected in the amount of steam from the actual boiler. There is a time lag, and there is a possibility that coordination with the turbine bypass valve, whose opening is controlled in proportion to the AFC signal, cannot be performed well.

At least one embodiment of the present invention has been made in view of the above circumstances, and a control device and a control method capable of contributing to frequency maintenance of a power system by having good followability to an AFC signal can be provided. The purpose is to provide.

The control device according to at least one embodiment of the present invention is used to solve the above problems.
A control device for a thermal power plant including a boiler, a steam turbine driven by steam from the boiler, and a turbine bypass valve for adjusting the amount of steam bypassing the steam turbine.
In the AFC compatible mode of the thermal power plant, a turbine bypass valve opening command value generation unit for generating a turbine bypass valve opening command value of the turbine bypass valve based on the AFC signal, and a turbine bypass valve opening command value generation unit.
A turbine bypass valve control unit for controlling the turbine bypass valve based on the turbine bypass valve opening command value, and a turbine bypass valve control unit.
In the AFC compatible mode, a boiler input command value generator for generating a boiler input command value by adding a plus sign bias value to a base input value based on a load command value for the thermal power plant, and a boiler input command value generator.
A boiler control unit for controlling the boiler based on the boiler input command value, and
To prepare for.

The control method according to at least one embodiment of the present invention is to solve the above problems.
A method for controlling a thermal power plant including a boiler, a steam turbine driven by steam from the boiler, and a turbine bypass valve for adjusting the amount of steam bypassing the steam turbine.
In the AFC compatible mode of the thermal power plant, a step of generating a boiler input command value by adding a plus sign bias value to a base input value based on a load command value for the thermal power plant.
The process of controlling the boiler based on the boiler input command value and
In the AFC compatible mode, a step of generating a turbine bypass valve opening command value of the turbine bypass valve based on the AFC signal, and a step of generating the turbine bypass valve opening command value.
A process of controlling the turbine bypass valve based on the turbine bypass valve opening command value, and
To prepare for.

According to at least one embodiment of the present invention, it is possible to provide a control device and a control method capable of contributing to frequency maintenance of a power system by having good followability to an AFC signal.

It is a schematic block diagram of the thermal power plant which concerns on one Embodiment. It is a block diagram which shows the internal structure of the control device of FIG. It is a control logic diagram of the turbine bypass valve opening command value generation part of FIG. It is an example of the function which the function arithmetic unit of FIG. 3 has. It is a control logic diagram of the boiler input command value generation part of FIG. It is an example of the bias value obtained by the function arithmetic unit of FIG. It is a control logic diagram of the main steam valve opening command value generation part of FIG. It is a timing chart which shows the time change of various signals in the control device of FIG. It is a graph which shows the adjustment allowance of a plant in a load command value. It is an overall block diagram of the thermal power plant which concerns on other embodiment. It is a part of the control logic diagram of the turbine bypass valve opening command value generation unit provided in the control device of FIG. It is a graph which shows the relationship between the differential pressure and the gain in the function arithmetic unit of FIG.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure to this, and are merely explanatory examples. do not have.
For example, expressions that represent relative or absolute arrangements such as "in one direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a tolerance or a state of relative displacement at an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, an expression representing a shape such as a square shape or a cylindrical shape not only represents a shape such as a square shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or a chamfering within a range where the same effect can be obtained. It shall also represent the shape including the part and the like.
On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions excluding the existence of other components.

In the following embodiment, the thermal power plant 1 will be described as an example of the thermal power plant to be controlled by the control device according to at least one embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a thermal power plant 1 according to an embodiment.

The thermal power plant 1 includes a boiler 2, a steam turbine 4, and a condenser 12. In the present embodiment, the case where the thermal power plant 1 includes a high-pressure side turbine 4A and a low-pressure side turbine 4B as the steam turbine 4 is illustrated, but the thermal power plant 1 may have a single steam turbine 4. Alternatively, it may have three or more steam turbines 4.

The boiler 2 is a steam generator capable of generating superheated steam by exchanging heat with water supply or steam by heat generated by burning fine fuel. The boiler 2 is, for example, a coal-fired (pulverized coal-fired) boiler in which pulverized coal obtained by crushing coal (carbon-containing solid fuel) is used as pulverized fuel and the pulverized fuel is burned by a burner.

In the present embodiment, a coal-fired boiler is exemplified as the boiler 2, but the boiler 2 uses a biomass fuel, a PC (Petroleum Coke) fuel generated during petroleum refining, and a solid fuel such as petroleum residue as the fuel. You may. Further, the boiler 2 can use not only solid fuel as fuel but also petroleum such as heavy oil, light oil and heavy oil, and liquid fuel such as factory effluent, and further, gaseous fuel (natural gas, natural gas, etc.) can be used as fuel. By-product gas, etc.) can also be used. Further, the boiler 2 may be a co-firing-fired boiler that uses a combination of these fuels.

The steam (superheated steam) generated in the boiler 2 is supplied to the steam turbine 4 via the main steam line 6. In the present embodiment, the steam from the boiler 2 is first supplied to the high-pressure side turbine 4A provided on the upstream side to drive the high-pressure side turbine 4A. The main steam line 6 connects between the boiler 2 and the high-pressure side turbine 4A. The main steam line 6 is provided with a main steam valve 8. The opening degree of the main steam valve 8 is controlled by the control device 100, so that the amount of steam supplied from the boiler 2 to the steam turbine 4 is variable.

The steam that has finished its work in the high-pressure side turbine 4A is supplied to the low-pressure side turbine 4B provided on the downstream side via the steam line 10 to drive the low-pressure side turbine 4B. The steam line 10 connects between the high pressure side turbine 4A and the low pressure side turbine 4B. The steam that has finished its work in the low-pressure turbine 4B is discharged to the condenser 12, so that condensate is generated.

Further, a bypass line 14 for connecting the upstream side of the main steam line 6 from the main steam valve 8 and the condenser 12 is provided. A turbine bypass valve 16 is provided in the bypass line 14, and by adjusting the opening degree of the turbine bypass valve 16, a part of the steam flowing through the main steam line 6 is bypassed by the steam turbine 4 to make a condenser. It can be discharged to 12.

The output shafts of the high-pressure side turbine 4A and the low-pressure side turbine 4B are connected to the rotating shafts of a generator (not shown), respectively. The generator generates electricity by being driven by the power from these steam turbines 4. The electric power generated by the generator is supplied to the electric power system (for example, a commercial system) via a transmission line (not shown).

The high-pressure side turbine 4A and the low-pressure side turbine 4B have a common output shaft, and the output shaft may be connected to a common generator. As a generator, the output shaft of the high-pressure side turbine 4A may be connected. A first generator to which the output shaft of the low-pressure turbine 4B is connected and a second generator to which the output shaft of the low-pressure turbine 4B is connected may be provided.

The control device 100 is a control unit of the thermal power generation plant 1, and is composed of, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. There is. As an example, a series of processes for realizing various functions are stored in a storage medium or the like in the form of a program, and the CPU reads this program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is installed in a ROM or other storage medium in advance, is provided in a state of being stored in a computer-readable storage medium, or is distributed via a wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

FIG. 2 is a block diagram showing an internal configuration of the control device 100 of FIG. The control device 100 includes a turbine bypass valve opening command value generation unit 110, a turbine bypass valve control unit 140, a boiler input command value generation unit 142, a boiler control unit 160, and a main steam valve opening command value generation unit 162. And a main steam valve control unit 174. The turbine bypass valve opening command value generation unit 110 creates the opening command value Stb of the turbine bypass valve 16, and the turbine bypass valve control unit 140 controls the opening degree of the turbine bypass valve 16 based on the opening command value Stb. do. The boiler input command value generation unit 142 generates a boiler input command value BID, and the boiler control unit 160 controls the boiler 2 based on the boiler input command value BID. The main steam valve opening command value generation unit 162 generates the main steam valve opening command value Jd for controlling the opening degree of the main steam valve 8, and the main steam valve control unit 174 generates the main steam valve opening command value. The main steam valve 8 is controlled based on Jd.

Subsequently, each configuration of the control device 100 shown in FIG. 2 will be described in detail. FIG. 3 is a control logic diagram of the turbine bypass valve opening command value generation unit 110 of FIG. The turbine bypass valve opening command value generation unit 110 is configured to generate the turbine bypass valve opening command value Stb of the turbine bypass valve 16, and the first opening command value calculation unit 112 and the second opening command value. It includes a calculation unit 120 and a third opening command value calculation unit 130.

In the first opening command value calculation unit 112, the subtractor 114 calculates the differential pressure ΔPs between the detected value Ps of the main steam pressure in the main steam line 6 and the target main steam pressure Pst, and the difference is calculated by the PI controller 116. The first opening command value Stb1 corresponding to the pressure ΔPs is obtained. The target main steam pressure Pst is calculated by adding a predetermined bias value Psb to the main steam pressure set value Pss which is a reference value in the adder 118. The bias value Psb is a parameter added to the main steam pressure set value Pss in order to use it as a threshold value for determining an abnormal rise in the main steam pressure Ps. "1.0 MPa" can be selectively switched. The first opening command value Stb1 calculated in this way functions as an opening command value for controlling the opening of the turbine bypass valve 16 when the main steam pressure Ps in the main steam line 6 rises abnormally. ..

The second opening command value calculation unit 120 is configured to calculate the second opening command value Stb2, which is the opening command value Stb for controlling the opening degree of the turbine bypass valve 16 at the time of starting. In the second opening command value calculation unit 120, the detection value Ps of the steam pressure (main steam pressure) in the main steam line 6 is input to the function calculator 122, so that the opening of the turbine bypass valve 16 suitable for starting is started. Calculated so that control is enforced.

The first opening command value calculation unit 112 and the second opening command value calculation unit 120 described above are connected via the switch SW2. The switch SW2 can be switched based on whether or not the operation mode is the start mode. Specifically, when the operation mode is in the start mode, the switch SW2 selects the second opening command value calculation unit 120, and when the operation mode is not the start mode, the first opening command value calculation unit 112. Select.

The third opening degree command value calculation unit 130 is configured to calculate the third opening degree command value Stb3, and includes a base opening degree calculation unit 132 and a bias opening degree calculation unit 134. The third opening command value Stb3 is the addition of the bias opening Stb3bias calculated by the bias opening calculation unit 134 to the base opening Stb3base calculated by the base opening calculation unit 132 in the adder 136. Is sought after.

The base opening degree calculation unit 132 calculates the base opening degree Stb3base of the turbine bypass valve 16 based on the load command value L. The load command value L is provided, for example, from the central power supply command center, and is converted into steam flow rate Qs in the function calculator 138 in the base opening degree calculation unit 132. The subtractor 140 calculates the difference ΔQs between the steam flow rate Qs calculated by the function calculator 138 and the detected value Qsj of the steam flow rate at the outlet of the first bypass line. The difference ΔQs is input to the PI controller 142 to obtain the corresponding base opening degree Stb3base. A hold circuit 144 is provided on the output side of the PI controller 142 so that a constant base opening Stb1 is maintained in the AFC compatible mode (while receiving the AFC signal). ..

The bias opening degree calculation unit 134 calculates the bias opening degree Stb3bias based on the AFC signal. In the bias opening degree calculation unit 134, the AFC signal is converted into the bias opening degree Stb3bias by being input to the function calculator 146. FIG. 4 is an example of a function included in the function calculator 146 of FIG. In FIG. 4, the function is defined so that the bias opening Stb3bias decreases monotonically as the AFC signal increases (note that the range above and below the preset upper limit value and lower limit value of the AFC signal is defined. The bias opening Stb3bias is defined to be constant).

A switch SW3 is provided on the output side of the function calculator 146. The switch SW3 sets either the calculation result of the function calculator 146 as the bias opening Stb3bias or the preset default value "0%" based on whether or not the switch SW3 is in the AFC compatible mode in which the AFC signal is input. It is switchable. That is, in the AFC compatible mode, the calculation result of the function calculator 146 is used as the bias opening Stb3bias, and in the other operation modes, the bias opening Stb3bias becomes zero.

The base opening degree Stb3base and the bias opening degree Stb3bias calculated in this way are added to each other in the adder 136. A switch SW4 is provided on the output side of the adder 136, and the calculation result of the adder 136 is set as the third opening command value Stb3 based on whether or not the AFC signal is input in the AFC compatible mode. Any of the preset default values "0%" can be switched. That is, in the AFC compatible mode, the calculation result of the adder 136 is used as the third opening command value Stb3, and in the other operation modes, the third opening command value Stb3 becomes zero.

Then, in the turbine bypass valve opening command value generation unit 110, the higher value selector HS is configured to select the larger of the outputs from the switches SW2 and SW4 as the opening command value Stb. The opening command value Stb is input to the turbine bypass valve control unit 140 (see FIG. 2) and is used for opening degree control of the turbine bypass valve 16.

By controlling the turbine bypass valve 16 based on the turbine bypass valve opening command value Stb calculated in this way, the turbine bypass valve control unit 140 shortens the start-up time during the operation of a series of thermal power generation plants 1. Good responsiveness to the AFC signal can be obtained in the AFC-compatible mode while accurately avoiding an abnormal rise in the main steam pressure. That is, the second opening command value Stb2 is output as the turbine bypass valve opening command value Stb at the time of starting, so that the turbine bypass valve 16 suitable for starting is controlled. Further, in the normal time when the AFC signal is not received, the turbine bypass valve 16 is controlled based on the third opening command value Stb3 which is the base opening Stb3base because the bias opening Stb3bias based on the AFC signal is zero. When the main steam pressure Ps becomes abnormally increased due to being equal to or higher than the main steam pressure set value Pst, the turbine bypass valve 16 is controlled based on the first opening command value Stb1 to cause an abnormal increase in the main steam pressure Ps. It can be suppressed. Then, in the AFC-compatible mode for receiving the AFC signal, the turbine bypass valve 16 is controlled based on the third opening command value Stb3 in which the bias opening Stb3bias based on the AFC signal is added to the base opening Stb3base. As a result, even when there is a time lag until the boiler input signal is reflected in the amount of steam as in the boiler 2 as a coal-fired boiler, the opening degree of the turbine bypass valve 16 is controlled based on the AFC signal to generate the AFC signal. On the other hand, good followability can be obtained. In the AFC compatible mode, the boiler input command value BID is generated as described later, so that the adjustment allowance for the turbine bypass valve 16 can be obtained regardless of the size of the load command value L.

Subsequently, FIG. 5 is a control logic diagram of the boiler input command value generation unit 142 of FIG. In the boiler input command value generation unit 142, the load command value L is first input to the rate of change limiter 144. In the rate of change limiter 144, the rate of change of the load command value L, which changes from moment to moment, is limited to be equal to or less than a predetermined value, and is output as the first command value D1. The second command value D2 (MWD) is obtained by adding the frequency control signal Df to the first command value D1 by the adder 146. The frequency control signal Df contributes to the stabilization of the power system by adding the load corresponding to the fluctuation of the system frequency to the first command value D1 (generator output command). In FIG. 5, the frequency control signal is the result of limiting the rate of change by inputting the system frequency to the function calculator 147, calculating the load corresponding to the system frequency, and inputting the output to the rate of change limiter 149. It is added to the first command value D1 as Df.

In the circuit of FIG. 5, the frequency control signal Df is added to the first command value D1, but the AFC signal is not added. This is because the turbine bypass valve 16 is maintained at an appropriate opening so as to cope with the increase / decrease in the turbine swallowing flow rate by increasing the boiler input command value BID by adding the bias value Dbias described later, so that the AFC signal is used. This is because it is not necessary to increase or decrease the boiler input command value BID by adding.

Subsequently, the main steam pressure control signal Ds is further added to the second command value D2 output from the adder 146 to obtain the third command value D3. The main steam pressure control signal Ds is the target main steam pressure Pst calculated by inputting the second command value D2 to the function calculator 152 in the subtractor 150, and the detected main steam pressure Ps in the main steam line 6. The pressure difference ΔPs is calculated, and the pressure difference ΔPs is input to the PI controller 154 to obtain the pressure difference.

Further, in the adder 156, the boiler input command value BID is generated by adding the bias value Dbias to the third command value D3 which is the base value based on the load command value L for the thermal power plant 1. The bias value Dbias can be switched by the switch SW6, a plus sign value obtained by the function calculator 158 is selected in the AFC compatible mode, and "0%" is selected in the other operation modes.

Here, FIG. 6 is an example of the bias value Dbias obtained by the function calculator 158 of FIG. In the example of FIG. 6, the bias value Dbias is abbreviated without depending on the load command value L in the range where the load command value L (second command value D2) input to the boiler input command value generation unit 142 is equal to or less than a predetermined value. It is set to be constant. The value is set, for example, corresponding to the maximum reduction value with respect to the reference value of the AFC signal. As a result, in the AFC compatible mode, the constant bypass value does not change even when the load command value L changes, so that the adjustment allowance of the turbine bypass valve 16 can be secured in a wide load range. That is, even when the AFC signal is negative in the AFC compatible mode, the load command regardless of whether the AFC signal is positive or negative is generated by adding the bias value Dbias which is a constant value having a positive sign to generate the boiler input command value BID. A boiler output larger than the value L can be secured, and followability can be improved by controlling the opening degree of the turbine bypass valve 16 corresponding to the AFC signal.

The bias value Dbias is set so as to decrease as the load command value L approaches the upper limit value (100%) of the load command value L in the range where the load command value L is larger than a predetermined value. In the example shown in FIG. 6, in the range of the load command value L from 95% to the upper limit value (100%), the bias value Dias is set to monotonically decrease as the load command value L increases.

The boiler input command value BID calculated in this way is input to the boiler control unit 160 (see FIG. 2). The boiler control unit 160 controls the boiler 2 based on the boiler input command value BID.

Subsequently, FIG. 7 is a control logic diagram of the main steam valve opening command value generation unit 162 of FIG. In the main steam valve opening command value generation unit 162, the AFC signal is converted into the fourth command value D4 by the function calculator 164. The switch SW7 inputs the fourth command value D4 to the rate of change limiter 166 by selecting the fourth command value D4 in the AFC compatible mode, and adds the result to the above-mentioned first command value D1 (see FIG. 5) in the adder 168. As a result, the fifth command value D5 is obtained. By adding the output signal from the rate of change limiter 166 to the first command value D1 in this way, the fluctuation range of the main steam pressure during operation of the turbine bypass valve 16 can be reduced, and the generator output with respect to the AFC signal can be reduced. The responsiveness of the is expected to improve. For the fifth command value D5, the deviation ΔP from the output detection value P of the generator (not shown) connected to the steam turbine 4 in the subtractor 170 is calculated, and the main steam valve corresponding to the deviation ΔP in the PI controller 172. The opening command value Jd is generated.
In other operation modes, the switch SW7 selects the default value "0%", and the fifth command value D5 becomes the first command value D1 itself.

The main steam valve opening command value Jd generated by the main steam valve opening command value generation unit 162 in this way is given to the main steam valve control unit 174. The main steam valve control unit 174 controls the opening degree of the main steam valve 8 based on the main steam valve opening command value Jd. As a result, the opening degree of the main steam valve 8 is coordinated and controlled together with the opening degree of the turbine bypass valve 16 also considering the AFC signal based on the main steam valve opening command value Jd considering the AFC signal, and follows the AFC signal. The sex can be improved.

Subsequently, the control contents of the thermal power plant 1 by the control device 100 having the above configuration will be described. FIG. 8 is a timing chart showing time changes of various signals in the control device 100 of FIG. FIG. 8 shows (a) AFC signal in the case where the control device 100 shifts to the AFC compatible mode by receiving the AFC signal after the time t0 in the initial state in which the thermal power generation plant 1 is controlled in the normal mode. , (B) Load command value L, (c) Fifth command value D5, (d) Second command value D2, (e) Third command value D3, (f) Boiler input command value BID, (g) Main steam Valve opening command value Jd, (h) Turbine bypass valve opening command value Stb, (i) Generator output P, (j) Main steam pressure deviation ΔPs (= Main steam pressure detection value Ps-Target main steam pressure Pst ) Changes over time are shown.

(A) The AFC signal generally has a complicated waveform centered on a reference value (0%), but in the present embodiment, in order to make the explanation easy to understand, the AFC signal changes stepwise with the passage of time. (Specifically, (a) the AFC signal is "+ 3%" at times t0 to t1, "+ 5%" at times t1 to t2, and "+ 1%" at times t2 to t3. fluctuate). Further, in order to explain (a) the responsiveness to the AFC signal in an easy-to-understand manner, (b) the load command value L received by the control device 100 from the central power supply command or the like is assumed to be constant (50%).

(C) The fifth command value D5 is calculated by inputting the fourth command value D4 based on the AFC signal to the rate of change limiter 166 by selecting the function calculator 164 side in the switch SW7 in the AFC compatible mode. It is obtained by adding the first command value D1 to the value in the adder 168. As a result, the fifth command value D5 has a waveform in which (a) an AFC signal that changes with time is added to (b) a load command value L that is constant (50%).

(D) The second command value D2 is obtained by adding the frequency control signal Df in the adder 146 to the (b) load command value L whose rate of change is limited by the rate of change limiter 144. In the present embodiment, the frequency control signal Df is set to zero, and (b) the second command value D2 having a constant value (50%) similar to the load command value L is shown.

(E) The third command value D3 is obtained by adding the main steam pressure control signal Ds in the adder 148 to (d) the second command value D2, and has a constant value (50%) (d). ) By adding the main steam pressure control signal Ds that fluctuates with time to the second command value D2, the behavior that fluctuates around the second command value D2 is shown.

(F) The boiler input command value BID is obtained by adding the bias value Dbias in the adder 156 to (e) the third command value D3. In the AFC compatible mode, a constant value (5%) set by the function calculator 158 is added as the bias value Dbias. A constant value is added to the boiler input command value BID at the timing when the AFC mode is set (before the time t0 when the AFC signal is input). The AFC signal is input after the boiler load has been increased to a certain value. As a result, (f) the boiler input command value BID shows behavior that fluctuates around a value obtained by adding a bias value Dbias (5%) to a second command value D2 (50%). Here, the AFC mode may be set automatically by setting a time in advance, in addition to being determined by the operator.

(G) The main steam valve opening command value Jd is calculated in the PI controller 172 based on (c) the deviation ΔP between the fifth command value D5 and (i) the generator output P, and is used as the boiler input command value BID. The temporal change reflecting the tendency of the first command value D1 is shown for the corresponding waveform.

(H) The turbine bypass valve opening command value Stb is obtained by adding (a) the bias opening Stb3bias based on the AFC signal to a constant base opening Stb3base after the time t0 when the AFC signal is input. Therefore, (a) a stepwise time change corresponding to the AFC signal is shown.

(I) The generator output P shows an increasing / decreasing tendency corresponding to (a) AFC signal while fluctuating with time. This indicates that the power generation control of the thermal power plant 1 is performed so as to correspond to the AFC signal, and good followability to the AFC signal is obtained.

(J) The main steam pressure deviation ΔPs is the differential pressure between the steam pressure Ps and the target main steam pressure Pst in the main steam line 6 as described above, and fluctuates with time according to the load of the high-pressure side turbine 4A. ing. The main steam pressure deviation ΔPs fluctuates with time and increases or decreases in response to the AFC signal.

FIG. 9 is a graph showing the load adjustment allowance of the plant at the load command value L. In FIG. 9, in order to compare the effects of the bias value Dbias in an easy-to-understand manner, as a comparative example, the load adjustment allowance of the boiler input command value BID when the bias value Dbias is fixed to 0% is shown by a broken line. According to this comparative example, the boiler input command value BID with the bias value Dbias set to 0% has only the adjustment allowance according to the load command value L as described above with reference to FIG. 5, and therefore the load command value L. The load adjustment allowance decreases as the value decreases. On the other hand, in the present embodiment, a constant value having a positive sign is added as the bias value Dbias to obtain the boiler input command value BID. Therefore, as shown by the solid line in FIG. 9, the turbine bypass valve 16 is used in combination. Therefore, regardless of the magnitude of the load command value L, a constant load adjustment allowance can be obtained up to the low load side.

In the above comparative example, the turbine bypass valve 16 is not opened and closed, and the load is adjusted by increasing or decreasing the boiler input command value BID. As shown by the broken line in FIG. 9, the load adjustment allowance in the low load band is narrower than that in the high load band. On the other hand, in the present embodiment, the load adjustment allowance is set to the high load band by opening and closing the turbine bypass valve 16 after adding and fixing the bias value Dbias to the boiler input command value BID. Can be maintained at the same level as. That is, as compared with the comparative example, the load adjustment allowance in the low load band can be expanded. This is established by increasing the boiler input command value BID by the amount of adding the bias value Dbias, increasing the evaporation amount in advance, and using the evaporation amount as a buffer for the load adjustment allowance. In other words, it can be said that the operation control is "priority for load adjustment fee". With such control, even when the boiler 2 is operated in a load zone lower than 100% load, it is possible to cope with the problem of securing the load adjusting force due to an increase in renewable energy and the like.

Subsequently, the control device 100'that targets the thermal power plant 1'according to another embodiment will be described. FIG. 10 is an overall configuration diagram of a thermal power plant 1 ′ according to another embodiment. In the present embodiment, in addition to the first bypass line 14 corresponding to the bypass line 14 of the embodiment shown in FIG. 1, a second bypass line 15 is provided. The first bypass line 14 communicates the upstream side and the downstream side of the main steam line 6, and the first bypass line 14 is provided with a first turbine bypass valve 16. The opening degree of the first turbine bypass valve 16 can be controlled by the control device 100', and a part of the steam flowing through the main steam line 6 is sent to the high-pressure side turbine via the first bypass line 14 according to the opening degree. It can be supplied to the steam line 10 by bypassing 4A.

Further, a second bypass line 15 is provided between the upstream side of the low pressure side turbine 4B and the condenser 12 of the steam line 10. The second bypass line 15 is provided with a second turbine bypass valve 17. The opening degree of the second turbine bypass valve 17 can be controlled by the control device 100, and a part of the steam flowing through the steam line 10 is passed through the second bypass line 15 to the low pressure side turbine 4B according to the opening degree. It can be bypassed and supplied to the condenser 12.

The control device 100'has a common configuration (see FIG. 2) with the control device 100 according to the above-described embodiment. The turbine bypass valve opening command value generation unit 110 of the control device 100'creates a turbine bypass valve opening command value Stb corresponding to the first turbine bypass valve 16.
The opening degree of the second turbine bypass valve 17 is appropriately controlled in order to adjust the reheat steam pressure (inlet pressure of the low-pressure side turbine 4B) to a specified value at the time of starting the thermal power plant 1'or during normal operation. .. The opening target value of the second turbine bypass valve 17 is typically different between when the thermal power plant 1'is started and when it is in normal operation, and is appropriately set.

FIG. 11 is a part of a control logic diagram of the turbine bypass valve opening command value generation unit 110 ′ included in the control device 100 ′ of FIG. The turbine bypass valve opening command value generation unit 110'has basically the same control logic as that of FIG. 3, but in FIG. 11, the bias opening degree of the turbine bypass valve opening command value generation unit 110' Only the calculation unit 134'and the bias opening correction unit 200 are shown (note that other configurations of the turbine bypass valve opening command value generation unit 110' show the turbine bypass valve opening command value generation unit 110'. Since it is the same as 110, it is omitted in FIG. 11).

The bias opening degree correction unit 200 corrects the bias opening degree Stb3bias based on the load of the high-pressure side turbine 4A. In the present embodiment, the bias opening correction unit 200 has a differential pressure ΔP between the main steam pressure Ps in the main steam line 6 and the steam pressure Pse in the steam line 10 as a parameter for evaluating the load of the high-pressure side turbine 4A. ´ is obtained by the subtractor 202, and the differential pressure ΔP ′ is input to the function calculator 204 to calculate the gain G for correcting the bias opening Stb3bias.

FIG. 12 is a graph showing the relationship between the differential pressure ΔP'and the gain G in the function calculator 204 of FIG. In this example, the gain G is specified to decrease monotonically as the differential pressure ΔP'for evaluating the load of the high-pressure side turbine 4A increases. The gain G calculated in this way is used in the correction unit 206 to correct the bias opening Stb3bias by multiplying the output of the function calculator 146 based on the AFC signal.

The influence of the bias value Stb3bias on the third opening command value Stb3 becomes smaller on the lower load side, but in the present embodiment, the high voltage side with respect to the bias opening Stb3bias included in the third opening command value Stb3. A gain G that increases as the load of the turbine 4A decreases is set. As a result, the effect of the bias value Stb3bias at the third opening command value Stb3 can be effectively obtained even on the low load side, and good followability to the AFC signal can be obtained in a wide load range.

As described above, according to the above embodiment, it is possible to provide a control device and a control method capable of maintaining the power generation frequency with good followability to the AFC signal.

The contents described in each of the above embodiments are grasped as follows, for example.

(1) The control device according to one aspect is
A boiler (for example, the boiler 2 of the above embodiment), a steam turbine driven by steam from the boiler (for example, the steam turbine 4 of the above embodiment), and a turbine bypass for adjusting the amount of steam bypassing the steam turbine. A control device (for example, control devices 100, 100'of the above embodiment) of a thermal power plant (for example, the thermal power generation plants 1, 1'of the above embodiment) including a valve (for example, the turbine bypass valve 16 of the above embodiment). hand,
In the AFC compatible mode of the thermal power plant, the turbine bypass valve opening for generating the turbine bypass valve opening command value (for example, the turbine bypass valve opening command value Stb of the above embodiment) of the turbine bypass valve based on the AFC signal. Degree command value generation unit (for example, turbine bypass valve opening command value generation unit 110 of the above embodiment) and
A turbine bypass valve control unit (for example, the turbine bypass valve control unit 140 of the above embodiment) for controlling the turbine bypass valve based on the turbine bypass valve opening command value, and the turbine bypass valve control unit 140.
In the AFC compatible mode, a bias value (for example, a positive sign bias value) with respect to a base input value (for example, the second command value D2 of the above embodiment) based on a load command value (for example, the load command value L of the above embodiment) for the thermal power plant. For example, a boiler input command value generation unit for generating a boiler input command value (for example, the boiler input command value BID of the above embodiment) by adding the bias value Dbias of the above embodiment (for example, the boiler input command of the above embodiment). Value generator 142) and
A boiler control unit for controlling the boiler based on the boiler input command value (for example, the boiler control unit 160 of the above embodiment) and
To prepare for.

According to the aspect (1) above, in the AFC compatible mode, the opening degree of the turbine bypass valve is controlled based on the opening degree command value generated based on the AFC signal, which is good for the AFC signal. Followability can be obtained. On the other hand, the boiler input command value is generated by adding a plus sign bias value to the base input value based on the load command value. Thereby, when the turbine bypass valve is controlled by the opening command value based on the AFC signal, the opening adjustment allowance of the turbine bypass valve can be secured regardless of the positive / negative sign of the AFC signal.

(2) In another aspect, in the above aspect (1),
The bias value is constant regardless of the load command value in the range where the load command value is equal to or less than a predetermined value.

According to the aspect (2) above, the bias value added to the base input value when generating the boiler input command value is set to be constant regardless of the load command value. As a result, the bypass value does not change even when the load command value changes, so that the adjustment allowance for the turbine bypass valve can be secured in a wide load range.

(3) In another aspect, in the above aspect (2),
The bias value is set corresponding to the maximum reduction value with respect to the reference value of the AFC signal.

According to the aspect (3) above, a constant bias value is set corresponding to the maximum decrease value with respect to the reference value of the AFC signal regardless of the load command value. As a result, it is possible to always secure the adjustment allowance of the turbine bypass valve for the AFC signal that changes from moment to moment, and good followability to the AFC signal can be obtained.

(4) In another aspect, in any one of the above (1) to (3),
The opening command value generation unit sets the base opening of the turbine bias valve (for example, the base opening Stb3base of the above embodiment) at the time of transition to the AFC compatible mode to the bias opening based on the AFC signal (for example, the above). The bias opening degree Stb3bias) of the embodiment is added to generate the opening degree command value.

According to the aspect (4) above, the opening degree control value of the turbine bias valve is generated by adding the bias opening degree to the base opening degree. The base opening is the opening of the turbine bias valve when the thermal power plant shifts from the normal mode to the AFC signal compatible mode, and the bias value based on the AFC signal that changes from moment to moment is added to this. Generated. By controlling the opening degree of the turbine bypass valve based on such an opening degree control value, good followability to the AFC signal can be obtained.

(5) In another aspect, in the above aspect (4),
The base opening degree is an intermediate opening degree between the fully open state and the fully closed state.

According to the aspect (5) above, in the AFC compatible mode, the base opening degree, which is the reference for the opening degree control of the turbine bypass valve, is set to the intermediate opening degree. As a result, when the opening degree of the turbine bypass valve is changed based on the AFC signal, the adjustment allowance of the turbine bypass valve is secured regardless of the sign of the AFC signal, and good followability to the AFC signal can be obtained. ..

(6) In another aspect, in any one of the above (1) to (5),
The thermal power plant further includes a main steam valve (for example, the main steam valve 8 of the above embodiment) for adjusting the amount of main steam supplied from the boiler to the steam turbine.
The control device is
A steam valve opening command value generator (for example, the main steam valve opening of the above embodiment) for generating a steam valve opening command value (for example, the main steam valve opening command value Jd of the above embodiment) based on the AFC signal. Degree command value generation unit 162) and
A main steam valve control unit for controlling the main steam valve based on the steam valve opening command value (for example, the main steam valve control unit 174 of the above embodiment) and
Further prepare.

According to the aspect (6) above, the opening degree of the main steam valve is controlled based on the main steam valve opening command value generated based on the AFC signal. As a result, the main steam valve operates in cooperation with the turbine bypass valve whose opening degree is similarly controlled based on the AFC signal, so that the followability to the AFC signal can be improved.

(7) In another aspect, in any one of the above (1) to (6),
Further, a bias opening degree correction unit (for example, the bias opening degree correction unit 200 of the above embodiment) for correcting the bias opening degree based on the load of the steam turbine is further provided.

According to the aspect (7) above, by correcting the bias opening degree based on the load of the steam turbine, it is possible to improve the followability to the AFC signal due to the bias opening degree in a wide load range of the steam turbine.

(8) In another aspect, in the above aspect (7),
The bias opening correction unit corrects the bias opening degree so that the correction amount increases as the load decreases.

According to the aspect (8) above, the correction amount of the bias opening degree is set so as to increase as the load of the steam turbine decreases. As a result, it is possible to effectively improve the followability of the AFC signal due to the bias opening even on the low load side where the effect of the bias opening tends to be relatively small.

(9) In another aspect, in the above aspect (7) or (8),
The bias opening correction unit is a differential pressure (for example, the above-described embodiment) between the supply steam pressure of the steam turbine (for example, the main steam pressure Ps of the above-described embodiment) and the exhaust steam pressure (for example, the turbine exhaust pressure Pse of the above-mentioned embodiment). The load is obtained based on the differential pressure ΔP ′).

According to the above aspect (9), the load of the steam turbine is appropriately applied by the difference pressure between the vapor pressure supplied to the steam turbine and the vapor pressure discharged from the steam turbine without adding a new sensor or the like. Can be evaluated.

(10) In another aspect, in any one of the above (1) to (9),
The turbine bypass valve is provided in a bypass line that communicates the upstream side and the downstream side of the steam turbine.

According to the above aspect (10), by providing a turbine bypass valve in the bypass line connecting the upstream side and the downstream side of the steam turbine, for example, by adjusting the opening degree at the start of the thermal power plant, the steam turbine By supplying steam to the downstream side, various configurations (reheater, etc.) on the downstream side of the steam turbine can be suitably protected.

(11) In another aspect, in any one of the above (1) to (9),
The turbine bypass valve is provided in a bypass line that communicates the upstream side of the steam turbine and the condenser provided on the downstream side of the steam turbine.

According to the aspect (11) above, when the turbine bypass valve is controlled by the opening command value based on the AFC signal by simpler control, the opening degree of the turbine bypass valve is controlled regardless of the positive or negative sign of the AFC signal. The adjustment allowance can be secured (for example, the bias opening correction unit in (9) above can be omitted).

(12) The control method according to one aspect is
A boiler (for example, the boiler 2 of the above embodiment), a steam turbine driven by steam from the boiler (for example, the steam turbine 4 of the above embodiment), and a turbine bypass for adjusting the amount of steam bypassing the steam turbine. A method for controlling a thermal power plant (for example, the thermal power generation plants 1, 1'of the above embodiment) including a valve (for example, the turbine bypass valve 16 of the above embodiment).
In the AFC compatible mode of the thermal power plant, a positive sign is given to the base input value (for example, the second command value D2 of the above embodiment) based on the load command value (for example, the load command value L of the above embodiment) for the thermal power plant. A step of generating a boiler input command value (for example, the boiler input command value BID of the above embodiment) by adding a bias value (for example, the bias value Dbias of the above embodiment).
The process of controlling the boiler based on the boiler input command value and
In the AFC compatible mode, a step of generating a turbine bypass valve opening command value (for example, the turbine bypass valve opening command value Stb of the above embodiment) of the turbine bypass valve based on the AFC signal.
A process of controlling the turbine bypass valve based on the turbine bypass valve opening command value, and
To prepare for.

According to the aspect (12) above, in the AFC compatible mode, the opening degree of the turbine bypass valve is controlled based on the opening degree command value generated based on the AFC signal, which is good for the AFC signal. Followability can be obtained. On the other hand, the boiler input command value is generated by adding a plus sign bias value to the base input value based on the load command value. Thereby, when the turbine bypass valve is controlled by the opening command value based on the AFC signal, the opening adjustment allowance of the turbine bypass valve can be secured regardless of the positive / negative sign of the AFC signal.

(13) In another aspect, in the above aspect (12),
Since the boiler is controlled by the boiler input command value, the load of the boiler is increased from the load command value, and then the turbine bypass valve is controlled based on the opening command value.

According to the aspect (13) above, the opening control of the turbine bypass valve is performed after the opening adjustment allowance of the turbine bypass valve is secured by increasing the load of the boiler from the load command value. As a result, when the opening degree of the turbine bypass valve is controlled based on the AFC signal, the opening degree corresponding to the AFC signal can be adjusted regardless of whether the AFC signal is positive or negative, and good followability to the AFC signal can be obtained. can get.

1 Thermal power plant 2 Boiler 4 Steam turbine 4A High pressure side turbine 4B Low pressure side turbine 6 Main steam line 8 Main steam valve 10 Steam line 12 Condenser 14 Bypass line (1st bypass line)
15 2nd bypass line 16 Turbine bypass valve (1st turbine bypass valve)
17 2nd turbine bypass valve 100 Control device 110 Turbine bypass valve opening command value generation unit 112 1st opening command value calculation unit 120 2nd opening command value calculation unit 130 3rd opening command value calculation unit 132 Base opening Calculation unit 134 Bias opening calculation unit 140 Turbine bypass valve control unit 142 Boiler input command value generation unit 144 Hold circuit 160 Boiler control unit 162 Main steam valve opening command value generation unit 174 Main steam valve control unit 200 Bias opening correction unit 206 Correction section

Claims (13)

A control device for a thermal power plant including a boiler, a steam turbine driven by steam from the boiler, and a turbine bypass valve for adjusting the amount of steam bypassing the steam turbine.
In the AFC compatible mode of the thermal power plant, a turbine bypass valve opening command value generation unit for generating a turbine bypass valve opening command value of the turbine bypass valve based on the AFC signal, and a turbine bypass valve opening command value generation unit.
A turbine bypass valve control unit for controlling the turbine bypass valve based on the turbine bypass valve opening command value, and a turbine bypass valve control unit.
In the AFC compatible mode, a boiler input command value generator for generating a boiler input command value by adding a plus sign bias value to a base input value based on a load command value for the thermal power plant, and a boiler input command value generator.
A boiler control unit for controlling the boiler based on the boiler input command value, and
A control device. The control device according to claim 1, wherein the bias value is constant regardless of the load command value within a range in which the load command value is equal to or less than a predetermined value. The control device according to claim 2, wherein the bias value is set corresponding to a maximum reduction value with respect to a reference value of the AFC signal. The turbine bypass valve opening command value generation unit opens the turbine bypass valve by adding the bias opening based on the AFC signal to the base opening of the turbine bias valve at the time of transition to the AFC compatible mode. The control device according to any one of claims 1 to 3, which is configured to generate a degree command value. The control device according to claim 4, wherein the base opening degree is an intermediate opening degree between a fully open state and a fully closed state. The thermal power plant further comprises a main steam valve for adjusting the amount of main steam supplied from the boiler to the steam turbine.
The control device is
A main steam valve opening command value generation unit for generating a main steam valve opening command value based on the AFC signal, and a main steam valve opening command value generation unit.
A main steam valve control unit for controlling the main steam valve based on the main steam valve opening command value, and
The control device according to any one of claims 1 to 5, further comprising. The control device according to any one of claims 1 to 6, further comprising a bias opening degree correction unit for correcting the bias opening degree based on the load of the steam turbine. The control device according to claim 7, wherein the bias opening degree correction unit corrects the bias opening degree so that the correction amount increases as the load decreases. The control device according to claim 7 or 8, wherein the bias opening correction unit obtains the load based on the differential pressure between the supply vapor pressure and the exhaust vapor pressure of the steam turbine. The control device according to any one of claims 1 to 9, wherein the turbine bypass valve is provided in a bypass line communicating the upstream side and the downstream side of the steam turbine. The control according to any one of claims 1 to 9, wherein the turbine bypass valve is provided in a bypass line connecting an upstream side of the steam turbine and a condenser provided on the downstream side of the steam turbine. Device. A method for controlling a thermal power plant including a boiler, a steam turbine driven by steam from the boiler, and a turbine bypass valve for adjusting the amount of steam bypassing the steam turbine.
In the AFC compatible mode of the thermal power plant, a step of generating a boiler input command value by adding a plus sign bias value to a base input value based on a load command value for the thermal power plant.
The process of controlling the boiler based on the boiler input command value and
In the AFC compatible mode, a step of generating a turbine bypass valve opening command value of the turbine bypass valve based on the AFC signal, and a step of generating the turbine bypass valve opening command value.
A process of controlling the turbine bypass valve based on the turbine bypass valve opening command value, and
A control method. A claim that the turbine bypass valve is controlled based on the turbine bypass valve opening command value after the load of the boiler is increased from the load command value by controlling the boiler by the boiler input command value. 12. The control method according to 12.

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