TWI805125B - Control device for thermal power plant and control method for thermal power plant - Google Patents

Abstract

The control device controls a thermal power plant that includes a turbine bypass valve for adjusting the amount of steam bypassing a steam turbine driven by steam from a boiler. The control device controls the turbine bypass valve based on the turbine bypass valve opening degree command value, and controls the boiler based on the boiler input command value. The command value of the opening degree of the turbine bypass valve is generated according to the AFC signal in the AFC corresponding mode of the thermal power plant. The boiler input command value is generated by adding a positive sign deviation value to the basic input value based on the load command value for the thermal power plant in the AFC corresponding mode.

Description

Control device for thermal power plant and control method for thermal power plant

This disclosure relates to a control device and a control method.

This case claims priority based on Japanese Patent Application No. 2020-219036 filed with the Japan Patent Office on December 28, 2020, and its contents are incorporated herein.

A thermal power plant that uses steam generated in a boiler (steam generator) to drive a steam turbine is widely known. In such a thermal power plant, a turbine bypass valve is provided on a bypass line constituting a steam turbine bypass line for a line for supplying steam from a boiler to a steam turbine. The turbine bypass valve is typically used to control the opening degree before the start of the steam turbine, thereby helping to shorten the start-up time, or to perform the opening action when the steam pressure in the steam turbine rises excessively, thereby, Suppresses rise in vapor pressure.

By the way, as such a thermal power plant, an electric power company that operates a thermal power plant that uses the output of a steam turbine to generate electricity has made an effort to control the voltage and frequency of the generated power according to the Electric Power Business Act. The supply side is the obligation to maintain the power system at a predetermined value respectively. According to the load command value provided by the central power supply command post, or compared with the The AFC (Automatic Frequency Control) signal corresponding to the fast frequency change is used to control the output of the boiler, and the correspondence is made through this.

However, for example, in thermal power plants using boilers with low responsiveness such as coal boilers, it is difficult to obtain good followability to components corresponding to relatively fast frequency changes such as AFC signals. For such a conventional problem, for example, in Patent Document 1, it is proposed to maintain the above-mentioned turbine bypass valve in a fully closed state during normal operation, and when the AFC signal is received, the AFC signal is added to the load command value. The obtained boiler input command value is used to control the opening degree of the turbine bypass valve proportional to the AFC signal, thereby improving the followability to the AFC signal.

[Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Unexamined Patent Publication No. 59-145309

In the aforementioned Patent Document 1, when the AFC signal is received, the boiler input command value is generated by adding the AFC signal to the load command value, and a boiler input command larger than the load command value is obtained while the AFC signal is positive. On the other hand, when the AFC signal is negative, the boiler input signal is smaller than the load command value, and the adjustment margin for the opening degree control of the turbine bypass valve corresponding to the AFC signal is small, so It is difficult to respond to large changes in the AFC signal. Furthermore, in Patent Document 1, the boiler input signal is obtained by adding the AFC signal to the load command value. However, as mentioned above, there will be a lot of steam until the boiler input signal is reflected in the actual amount of steam from the boiler. The time lag is that there is a risk that the opening degree control proportional to the AFC signal cannot be well coordinated with the turbine bypass valve.

At least one embodiment of the present invention is created in view of the above-mentioned circumstances, and its purpose is to provide a control device and a control method, which can contribute to the frequency maintenance of the power system by having good followability to the AFC signal .

A control device according to at least one embodiment of the present invention is to solve the above-mentioned problems, A control device for a thermal power plant comprising: a boiler, a steam turbine driven by steam from the boiler, and a turbine for adjusting the amount of steam bypassing the steam turbine A bypass valve; characterized in that the control device has: The turbine bypass valve opening command value generation unit is used to generate the turbine bypass valve opening command value of the turbine bypass valve according to the AFC signal in the AFC corresponding mode of the thermal power plant; a turbine bypass valve control unit configured to control the turbine bypass valve according to an opening degree command value of the turbine bypass valve; The boiler input command value generation unit is used to generate a boiler input command by adding a positive sign deviation value to the basic input value based on the load command value of the thermal power plant in the aforementioned AFC corresponding mode value; and A boiler control unit for controlling the boiler based on the boiler input command value.

The control method according to at least one embodiment of the present invention is to solve the above-mentioned problems, A control method is a control method of a thermal power plant comprising: a boiler, a steam turbine driven by steam from the boiler, and a turbine for adjusting the amount of steam bypassing the steam turbine A bypass valve; characterized in that the control method has: In the AFC corresponding mode of the aforementioned thermal power plant, the process of generating a boiler input command value by adding a positive sign deviation value to the basic input value based on the load command value of the aforementioned thermal power plant; Control the process of the aforementioned boiler according to the input command value of the aforementioned boiler; In the aforementioned AFC corresponding mode, a process of generating a command value of the turbine bypass valve opening degree of the aforementioned turbine bypass valve according to the AFC signal; and The process of controlling the turbine bypass valve according to the turbine bypass valve opening degree command value.

According to at least one embodiment of the present invention, a control device and a control method can be provided, which can contribute to the frequency maintenance of the power system by having good followability to the AFC signal.

Hereinafter, several embodiments related to the present disclosure will be described with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of components described in the embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples. For example, expressions that represent relative or absolute configurations such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial", etc., are not only It strictly shows such an arrangement, and also shows a state of relative displacement due to tolerances, left and right angles or distances at which the same function can be obtained. For example, expressions that express the equal state of things such as "same", "equal" and "homogeneous" not only strictly express the equal state, but also indicate that there is a tolerance, or the difference between the left and right that can obtain the same function status. For example, an expression indicating a shape such as a square shape or a cylindrical shape does not only mean a shape such as a square shape or a cylindrical shape in a geometrically rigorous sense, but also includes within the range where the same effect can be obtained. Shapes such as concavo-convex or chamfered corners. On the other hand, the so-called "have", "have", "possess", "include" or "have" the expression of one constituent element is not meant to exclude the mutually exclusive expression of the existence of other constituent elements.

In the following embodiments, a thermal power plant 1 will be described as an example of a 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 this embodiment, the thermal power plant 1 exemplifies a case where the steam turbine 4 includes a high-pressure turbine 4A and a low-pressure turbine 4B. However, the thermal power plant 1 may have a single steam turbine 4 or may have three steam turbines. Above the steam turbine 4.

Boiler 2 is a steam generator that exchanges heat generated by burning pulverized fuel with water or steam to generate superheated steam. The boiler 2 is, for example, a coal-fired (powdered coal-fired) boiler that uses pulverized coal (carbon-containing solid fuel) as a pulverized fuel and burns the pulverized fuel through a burner.

Also, in this embodiment, a coal-fired boiler is exemplified as the boiler 2, but the boiler 2 can also use biomass fuel, PC (Petroleum Coke) fuel generated during petroleum refining, or petroleum residues as fuel. other solid fuels. Moreover, the fuel of the boiler 2 series is not limited to solid fuel, and petroleum such as heavy oil, light oil, and heavy oil, or liquid fuel such as factory waste liquid can also be used, and further, gaseous fuel (natural gas, by-product gas, etc.). Furthermore, the boiler 2 may be a co-combustion boiler used in combination with these fuels.

The steam (superheated steam) generated by the boiler 2 is supplied to the steam turbine 4 through the main steam line 6 . In the present embodiment, the steam from the boiler 2 is first supplied to the high-pressure turbine 4A provided on the upstream side, and then the high-pressure turbine 4A is driven. The main steam line 6 is connected between the boiler 2 and the high-pressure side turbine 4A. A main steam valve 8 is provided on the main steam line 6 . The opening degree of the main steam valve 8 is controlled by the control device 100 , through which, the steam supply amount from the boiler 2 to the steam turbine 4 is variable.

The steam completed by the high-pressure turbine 4A passes through the steam line 10 and is supplied to the low-pressure turbine 4B provided on the downstream side, thereby driving the low-pressure turbine 4B. The steam line 10 is connected between the high-pressure side turbine 4A and the low-pressure side turbine 4B. The steam that has performed work in the low-pressure side turbine 4B is discharged to the condenser 12, whereby condensed water is generated.

Furthermore, a bypass line 14 connecting the upstream side of the main steam valve 8 in the main steam line 6 and the condenser 12 is provided. The bypass line 14 is provided with a turbine bypass valve 16 , and by adjusting the opening degree of the turbine bypass valve 16 , part of the steam flowing in the main steam line 6 can be bypassed by the steam turbine 4 and discharged to the condenser 12 .

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

Furthermore, 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 the generator, it may also be a first one having an output shaft connected to the high-pressure side turbine 4A. A generator, and a second generator connected to the output shaft of the low-pressure side turbine 4B.

The control device 100 is a control unit of the thermal power plant 1, and is composed of, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. Next, a series of processes for realizing various functions are memorized in the form of a program in a storage medium, etc. as an example, and the CPU reads the program into RAM, etc., and executes information processing and calculation processing. Through this, various Function. In addition, the program can also be applied to a type that is pre-installed in ROM or other storage media, or a type that provides a state stored in a computer-readable storage medium, or is caused by wired or wireless The type of delivery by means of communication, etc. The so-called computer-readable memory media include magnetic discs, optical magnetic discs, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

FIG. 2 is a block diagram showing the internal configuration of the control device 100 of FIG. 1 . The control device 100 includes: a turbine bypass valve opening degree command value generating unit 110, a turbine bypass valve control unit 140, a boiler input command value generating unit 142, a boiler control unit 160, a main steam valve opening degree command value generating unit 162, and Main steam valve control section 174 . The turbine bypass valve opening degree command value generator 110 generates an opening degree 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 degree command value Stb. The boiler input command value generator 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 degree command value generator 162 generates the main steam valve opening degree command value Jd for controlling the opening degree of the main steam valve 8, and the main steam valve control unit 174 controls the main steam valve opening degree command value Jd according to the main steam valve opening degree command value Jd. valve 8.

Next, 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 generator 110 shown in FIG. 2 . The turbine bypass valve opening degree command value generator 110 is configured to generate the turbine bypass valve opening degree command value Stb of the turbine bypass valve 16, and includes a first opening degree command value calculation unit 112, a second opening degree The command value calculation unit 120 and the third opening degree command value calculation unit 130 .

In the first opening degree command value calculation unit 112, the subtractor 114 calculates the difference ΔPs between the detection value Ps of the main steam pressure in the main steam line 6 and the target main steam pressure Pst, and obtains the difference ΔPs with the PI controller 116. The first opening degree command value Stb1 corresponding to the differential pressure ΔPs. The target main steam pressure Pst is connected to the adder 118, and is calculated by adding a predetermined deviation value Psb to the reference value, that is, the main steam pressure setting value Pss. The deviation value Psb is a parameter that is added to the main steam pressure setting value Pss in order to determine the threshold value for judging the abnormal rise of the main steam pressure Ps. In this embodiment, it can be selected and switched to "0MPa" by the switch SW1 Or "1.0MPa". Thus calculated first opening degree command value Stb1 functions as an opening degree command value for controlling the opening degree of the turbine bypass valve 16 when the main steam pressure Ps in the main steam line 6 rises abnormally.

The second opening degree command value calculation unit 120 is configured to calculate an opening degree command value Stb for controlling the opening degree of the turbine bypass valve 16 during startup, that is, a second opening degree command value Stb2. In the second opening degree command value calculation unit 120, calculation is performed so that the detected value Ps of the steam pressure (main steam pressure) in the main steam line 6 is input to the function calculator 122 to implement turbine bypass suitable for startup. The opening degree control of the valve 16.

The first opening degree command value calculation part 112 and the second opening degree command value calculation part 120 mentioned above are connected through the switch SW2. The switch SW2 can be switched according to whether or not the operation mode is the activation mode. Specifically, the switch SW2 selects the second opening degree command value calculation unit 120 when the operation mode is the activation mode, and selects the first opening degree command value calculation unit 112 when the operation mode is not the activation mode.

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 deviation opening degree calculation unit 134 . The 3rd opening degree command value Stb3 is in the adder 136, and the base opening degree Stb3base calculated in the base opening degree calculation part 132 is added to the deviation opening degree Stb3bias calculated in the deviation opening degree calculation part 134, whereby, Find out.

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 post, and is converted into the steam flow rate Qs in the basic opening degree calculation unit 132 and the function calculator 138 . The subtractor 140 calculates a 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. Furthermore, a holding circuit 144 is provided on the output port side of the PI controller 142 to maintain a constant basic opening degree Stb1 in the AFC corresponding mode (period of receiving the AFC signal).

The bias opening calculation unit 134 calculates the bias opening Stb3bias of the AFC signal. In the deviation opening calculation part 134 , the AFC signal is input to the function calculator 146 and transformed into the deviation opening Stb3bias. FIG. 4 is an example of the functions of the function calculator 146 in FIG. 3 . In Fig. 4, the function is increased according to the AFC signal, and the deviation from the opening degree Stb3bias is specified as monotonically decreasing (also, with respect to the range above the upper limit and below the lower limit of the preset AFC signal, the deviation from the opening degree Stb3bias is specified as constant).

A switch SW3 is provided on the output port side of the function calculator 146 . The switch SW3 can switch between the calculation result of the function calculator 146 as the deviation opening degree Stb3bias or the pre-set preset value "0%" according to whether it is in the AFC corresponding mode of the input AFC signal. That is, the calculation result of the function calculator 146 is used as the deviation opening degree Stb3bias in the AFC compatible mode, and the deviation opening degree Stb3bias is zero in other operation modes.

The base opening degree Stb3base and the deviation opening degree Stb3bias thus calculated are mutually added by the adder 136 . A switch SW4 is provided on the output port side of the adder 136. According to whether it is in the AFC corresponding mode of the input AFC signal, it can be switched that the third opening degree command value Stb3 is the calculation result of the adder 136, or it can be set in advance. Any one of the default value "0%". That is, the calculation result of the adder 136 is used as the third opening degree command value Stb3 in the AFC compatible mode, and the third opening degree command value Stb3 is zero in other operation modes.

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

The turbine bypass valve control unit 140 controls the turbine bypass valve 16 based on the turbine bypass valve opening degree command value Stb calculated in this way, so that the shortening of the start-up time or The main steam pressure rises abnormally, and in the AFC corresponding mode, a good response to the AFC signal can be obtained. That is, the second opening degree command value Stb2 is output as the turbine bypass valve opening degree command value Stb at startup, whereby the control of the turbine bypass valve 16 applicable at startup is performed. Moreover, when the AFC signal is not received normally, the deviation opening degree Stb3bias based on the AFC signal is zero, and then the turbine bypass valve 16 is controlled based on the base opening degree Stb3base, that is, the third opening degree command value Stb3, and When the main steam pressure Ps rises abnormally above the main steam pressure set value Pst, the turbine bypass valve 16 is controlled based on the first opening degree command value Stb1, thereby suppressing the abnormal rise of the main steam pressure Ps. Next, in the AFC corresponding mode receiving the AFC signal, the turbine bypass valve 16 is controlled based on the third opening degree command value Stb3 obtained by adding the deviation opening degree Stb3bias based on the AFC signal to the base opening degree Stb3base. After this, also when the input signal of the boiler 2 such as a coal-fired boiler is delayed until the amount of steam is reflected, the opening degree of the turbine bypass valve 16 is controlled according to the AFC signal, so that a good response to the AFC signal can be obtained. following. Furthermore, in the AFC support mode, the adjustment margin of the turbine bypass valve 16 can be obtained regardless of the magnitude of the load command value L by generating the boiler input command value BID as described later.

Next, FIG. 5 is a control logic diagram of the boiler input command value generator 142 shown in FIG. 2 . In boiler input command value generator 142 , first, load command value L is input to change rate limiter 144 . The change rate limiter 144 limits the rate of change of the load command value L that changes every moment to a predetermined value or less, and outputs it as a first command value D1. The frequency control signal Df is added to the first command value D1 by the adder 146, and thus the second command value D2 (MWD) is obtained. The frequency control signal Df contributes to the stabilization of the power system by adding the load corresponding to the variation of the system frequency to the first command value D1 (generator output command). In Fig. 5, the system frequency is input to the function calculator 147, the load portion corresponding to the system frequency is calculated, and the output is input to the rate-of-change limiter 149, whereby the result of limiting the rate of change is added as the frequency control signal Df to the first command value D1.

In the circuit of FIG. 5, one side of adding the frequency control signal Df to the first command value D1 constitutes not adding the AFC signal. This is to increase the boiler input command value BID by adding the bias value Dbias described later, and thereby maintain the turbine bypass valve 16 at an appropriate opening degree in order to respond to the increase or decrease of the turbine intake flow rate. Therefore, there is no need to increase or decrease the boiler input command value BID by adding the AFC signal.

Continuing, the second command value D2 output from the adder 146 is further added to the main steam pressure control signal Ds by the adder 148 to obtain the third command value D3. The main steam pressure control signal Ds is connected to the subtractor 150 to calculate the pressure difference between the target main steam pressure Pst calculated by inputting the second command value D2 to the function calculator 152 and the detected value Ps of the main steam pressure in the main steam pipeline 6 ΔPs is obtained by inputting the pressure difference ΔPs into the PI controller 154 .

Furthermore, the adder 156 adds the bias value Dbias to the base value based on the load command value L for the thermal power plant 1, that is, the third command value D3, thereby generating the boiler input command value BID. The bias value Dbias can be switched by the switch SW6. In the AFC corresponding mode, a value with a positive sign obtained by the function calculator 158 is selected, and in other operation modes, "0%" is selected.

Here, FIG. 6 is an example of the bias value Dbias obtained by the function calculator 158 in FIG. 5 . In the example of FIG. 6 , the bias value Dbias is set so as not to depend 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 generator 142 is equal to or less than a predetermined value. is roughly constant. This value is, for example, set to correspond to the maximum reduction of the reference value of the AFC signal. Thus, in the AFC compatible mode, since the constant bypass value does not change even when the load command value L changes, the adjustment margin of the turbine bypass valve 16 can be ensured in a wide load range. That is, also in the case that the AFC signal is negative in the AFC corresponding mode, a fixed value with a positive sign, that is, the deviation value Dbias is added to generate the boiler input command value BID, thereby ensuring that the ratio has nothing to do with the positive or negative of the AFC signal. For a boiler output with a large load command value L, followability can be improved by controlling the opening degree of the turbine bypass valve 16 corresponding to the AFC signal.

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

The boiler input command value BID thus calculated 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.

Next, FIG. 7 is a control logic diagram of the main steam valve opening degree command value generator 162 in FIG. 2 . In the main steam valve opening command value generator 162, the AFC signal is converted into a fourth command value D4 in the function calculator 164. The switch SW7 selects the fourth command value D4 in the AFC corresponding mode and inputs it to the rate-of-change limiter 166, and adds the result to the aforementioned first command value D1 (referring to FIG. 5 ) in the adder 168. Through this, the The fifth command value D5. In this way, by adding the output signal from the rate-of-change limiter 166 to the first command value D1, the fluctuation width of the main steam pressure during the operation of the turbine bypass valve 16 can be reduced, and it can be seen that the influence on the AFC signal The improvement of the responsiveness of the generator output. The fifth command value D5 is calculated by the subtractor 170 and the deviation ΔP from the output detection value P of the generator (not shown) connected to the steam turbine 4, and the PI controller 172 generates the opening degree of the main steam valve corresponding to the deviation ΔP Command value Jd. Furthermore, in other operation modes, the switcher SW7 selects the preset value "0%", and the fifth command value D5 becomes the first command value D1 itself.

In this way, the main steam valve opening degree command value Jd generated by the main steam valve opening degree command value generation unit 162 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 degree command value Jd. After this, the opening degree of the main steam valve 8 is coordinated and controlled according to the opening degree command value Jd of the main steam valve taking into account the AFC signal, together with the opening degree of the turbine bypass valve 16 which also considers the AFC signal, which can improve the AFC Signal followability.

Continuing, the content of control of the thermal power plant 1 by the control device 100 having the above-mentioned configuration will be described. FIG. 8 is a time sequence flow chart showing time changes of various signals in the control device 100 of FIG. 2 . In FIG. 8 , in the initial state where the control device 100 controls the thermal power plant 1 in the normal mode, after time t0, when the AFC signal is received and shifted to the AFC corresponding mode, (a) the AFC signal, (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 degree command value Jd, (h) turbine bypass valve opening degree command value Stb, (i) generator output P, (j) main steam pressure deviation ΔPs (= detection value of main steam pressure Ps - target main steam pressure Pst ) time changes.

(a) The AFC signal generally has a complex waveform centered on the reference value (0%). However, in this embodiment, for the sake of easy understanding and description, an AFC signal that changes step by step with the passage of time is exemplified (specifically, (a) The AFC signal changes step by step at "+3%" at time t0~t1, at "+5%" at time t1~t2, and at "+1%" at time t2~t3). Furthermore, (a) the control device 100 receives a central power supply command or the like for easy understanding of the response to the AFC signal; (b) the load command value L is constant (50%).

(c) The 5th command value D5 is the calculated value obtained by inputting the 4th command value D4 based on the AFC signal to the rate-of-change limiter 166 by selecting the function calculator 164 side by the switch SW7 in the AFC corresponding mode. , is obtained by adding the first command value D1 in the adder 168 . Thus, the fifth command value D5 has a waveform in which (a) the AFC signal that changes with time is added to the constant (50%) (b) load command value L.

(d) The second command value D2 is obtained by adding the frequency control signal Df to 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, revealing the second command value D2 having a constant value (50%) like the (b) load command value L.

(e) The 3rd command value D3 is for (d) the 2nd command value D2, add the main steam pressure control signal Ds in the adder 148, through the (d) 2nd command value with a fixed value (50%) Adding the time-varying main steam pressure control signal Ds to the command value D2 represents a behavior that changes around the second command value D2.

(f) The boiler input command value BID is obtained by adding the bias value Dbias in the adder 156 to the (e) third command value D3. In the AFC corresponding mode, add the fixed value (5%) set in the function calculator 158 as the deviation value Dbias. Furthermore, at the timing when the AFC mode is set (before the time t0 when the AFC signal is input), a fixed value is added to the boiler input command value BID. After the boiler load increases to the fixed value, input the AFC signal. Thus, (f) boiler input command value BID shows the behavior which fluctuates around the value which added the bias value Dbias (5%) to the 2nd command value D2 (50%). Here, the setting of the AFC mode may not only be determined and set by the operator, but also may be automatically set at a predetermined time.

(g) The command value Jd of the opening degree of the main steam valve is determined by the PI controller 172, and is calculated according to the deviation ΔP between (c) the fifth command value D5 and (i) the output P of the generator, which corresponds to the boiler input command value BID The waveform shows temporal changes reflecting the tendency of the first command value D1.

(h) The opening degree command value Stb of the turbine bypass valve is calculated based on (a) AFC signal deviation opening degree Stb3bias added to the constant basic opening degree Stb3base after the time t0 of inputting the AFC signal. (a) The phased time change corresponding to the AFC signal.

(i) The generator output P changes over time, showing a tendency to increase or decrease corresponding to (a) the AFC signal. This shows that the power generation control of the thermal power plant 1 is performed in response to the AFC signal, and good followability to the AFC signal is obtained.

(j) The main steam pressure deviation ΔPs is, as mentioned above, the differential pressure between the steam pressure Ps in the main steam line 6 and the target main steam pressure Pst, which changes temporally according to the load of the high-pressure side turbine 4A. The main steam pressure deviation ΔPs changes with time, corresponding to the increase or decrease of the AFC signal.

FIG. 9 is a graph showing a load adjustment margin of a plant in a load command value L. FIG. In FIG. 9 , in order to easily understand the effect of comparing the bias value Dbias, as a comparative example, the load adjustment margin of the boiler input command value BID when the bias value Dbias is fixed at 0% is indicated by a dotted line. According to this comparative example, the boiler input command value BID at which the deviation value Dbias is 0% is merely an adjustment margin corresponding to the load command value L as described above with reference to FIG. 5 , and decreases as the load command value L becomes lower. load regulation margin. On the other hand, in this embodiment, since the boiler input command value BID is obtained by adding a fixed value having a positive sign as the deviation value Dbias, as shown by the solid line in FIG. In this way, a constant load adjustment margin can be obtained up to the low load side regardless of the magnitude of the load command value L.

In the comparative example described above, the turbine bypass valve 16 is not opened and closed, and the load adjustment is performed by increasing or decreasing the boiler input command value BID. As indicated by the dotted line in FIG. 9 , the load adjustment margin in the low load range is narrower than that in the high load range. On the other hand, in the present embodiment, after the boiler input command value BID is fixed by adding the bias value Dbias, by opening and closing the turbine bypass valve 16, it is possible to maintain the load adjustment margin at the low load range. High load belts are equal. That is, compared with the comparative example, the load adjustment margin in the low load band can be enlarged. That is, the boiler input command value BID becomes larger only by adding the deviation value Dbias, and it is true to increase the evaporation amount in advance and use this evaporation amount as a buffer for the load adjustment margin. That is, operation control called "load adjustment margin priority". Through such control, even when the boiler 2 is operated under a load band lower than 100% load, it is possible to cope with the problem of securing the load adjustment force due to the increase of renewable energy and the like.

Next, the control device 100' having the thermal power plant 1' according to another embodiment as a control object will be described. FIG. 10 is an overall configuration diagram of a thermal power plant 1′ according to another embodiment. In this embodiment, a second bypass line 15 is provided in addition to the first bypass line 14 corresponding to the bypass line 14 of the embodiment shown in FIG. 1 . The first bypass line 14 communicates with the upstream side and the downstream side of the main steam line 6 , and a first turbine bypass valve 16 is provided on the first bypass line 14 . The opening degree of the first turbine bypass valve 16 can be controlled by the control device 100′. With its opening degree, a part of the steam flowing in the main steam pipeline 6 can pass through the first bypass pipeline 14 and pass through the high pressure side. The turbine 4A is supplied to the steam line 10 .

Furthermore, a second bypass line 15 is provided between the upstream side of the low-pressure side turbine 4B in the steam line 10 and the condenser 12 . A second turbine bypass valve 17 is provided in the second bypass line 15 . The opening degree of the second turbine bypass valve 17 can be controlled by the control device 100, and in accordance with the opening degree, a part of the steam flowing in the steam pipeline 10 can pass through the second bypass pipeline 15 and bypass the low-pressure side turbine 4B. And it is supplied to the condenser 12.

The control device 100' has the same configuration as the control device 100 of the above-mentioned embodiment (see FIG. 2 ). The turbine bypass valve opening degree command value generator 110 in the control device 100′ generates the turbine bypass valve opening degree command value Stb corresponding to the first turbine bypass valve 16 . The opening degree of the second turbine bypass valve 17 is appropriately controlled to adjust the reheat steam pressure (inlet pressure of the low-pressure side turbine 4B) to a predetermined value when the thermal power plant 1′ is started or in normal operation. Furthermore, typically, the opening degree target value of the second turbine bypass valve 17 is different between the start-up time and the normal operation time of the thermal power plant 1′, and is appropriately set respectively.

FIG. 11 is a part of a control logic diagram of a turbine bypass valve opening degree command value generator 110′ included in the control device 100′ of FIG. 10 . The turbine bypass valve opening degree command value generating unit 110′ has basically the same control logic as that in FIG. 134' and the deviation opening degree correction part 200 (also, the other configuration of the turbine bypass valve opening degree command value generating part 110' is the same as that of the turbine bypass valve opening degree command value generating part 110 shown in FIG. 3 . , so it is omitted in Figure 11).

The deviation opening degree correction unit 200 corrects the deviation opening degree Stb3bias according to the load of the high-pressure side turbine 4A. In this embodiment, the deviation opening correction unit 200 is used as a parameter for evaluating the load of the high-pressure side turbine 4A, and the subtractor 202 is used to obtain the main steam pressure Ps in the main steam line 6 and the steam pressure in the steam line 10. The differential pressure ΔP′ of Pse is input to the function calculator 204 to calculate the gain G for correcting the deviation from the opening degree 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. 11 . In this example, it is specified that the gain G decreases monotonically as the differential pressure ΔP′ for evaluating the load of the high-pressure side turbine 4A increases. The gain G thus calculated is multiplied by the output of the function calculator 146 based on the AFC signal in the correction unit 206 to correct the deviation from the opening degree Stb3bias.

The influence on the deviation value Stb3bias of the third opening degree command value Stb3 becomes smaller as the load becomes lower. However, in this embodiment, the deviation opening degree Stb3bias included in the third opening degree command value Stb3 is set as Gain G that becomes larger as the load on the high-pressure side turbine 4A becomes smaller. Through this, the effect of the bias value Stb3bias in the third opening degree command value Stb3 can be effectively obtained also 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 content described in each of the above-mentioned embodiments can be grasped as follows, for example.

(1) Regarding the control device of one of the states, It is a control device (such as the control device 100, 100' of the above-mentioned embodiment) of a thermal power plant (such as the thermal power plant 1, 1' of the above-mentioned embodiment), and the thermal power plant is equipped with: a boiler (such as the boiler of the above-mentioned embodiment boiler 2), a steam turbine driven by steam from the aforementioned boiler (such as the steam turbine 4 of the above-mentioned embodiment), and a turbine bypass valve for adjusting the amount of steam bypassing the aforementioned steam turbine (such as the steam turbine of the above-mentioned embodiment turbine bypass valve 16); it is characterized in that the control device has: The turbine bypass valve opening degree command value generator (for example, the turbine bypass valve opening degree command value generator 110 in the above-mentioned embodiment) is used to, in the AFC corresponding mode of the aforementioned thermal power plant, generate The turbine bypass valve opening degree command value of the aforementioned turbine bypass valve (such as the turbine bypass valve opening degree command value Stb in the above-mentioned embodiment); A turbine bypass valve control unit (such as the turbine bypass valve control unit 140 in the above-mentioned embodiment), which is configured to control the aforementioned turbine bypass valve according to the aforementioned turbine bypass valve opening degree command value; The boiler input command value generating unit (such as the boiler input command value generating unit 142 of the above-mentioned embodiment) is used to, in the aforementioned AFC corresponding mode, load command value based on the aforementioned thermal power plant (such as the above-mentioned embodiment) The basic input value (such as the second command value D2 of the above-mentioned embodiment) of the load command value L) is added with a positive sign deviation value (such as the deviation value Dbias of the above-mentioned embodiment), and through this, the boiler input command value (such as the above-mentioned The boiler input command value BID of the embodiment); and The boiler control unit (for example, the boiler control unit 160 in the above-mentioned embodiment) is used to control the boiler based on the boiler input command value.

According to the above (1), in the AFC corresponding mode, the opening degree of the turbine bypass valve is controlled according to the opening degree command value generated based on the AFC signal, thereby achieving good followability to the AFC signal. On the other hand, the boiler input command value is generated by adding a positive-signed deviation value to the basic input value based on the load command value. Thereby, when the turbine bypass valve is controlled by the opening degree command value based on the AFC signal, the opening degree adjustment margin of the turbine bypass valve can be ensured irrespective of the sign of the AFC signal.

(2) In another state, in the state of (1) above, The deviation value is constant regardless of the load command value in the range of the load command value or less.

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

(3) In another state, in the state of (2) above, The aforementioned offset value is set to correspond to the maximum reduction of the reference value of the aforementioned AFC signal.

According to the aspect of (3) above, the offset value which is constant regardless of the load command value is set so as to correspond to the maximum reduction value of the reference value of the AFC signal. Through this, the adjustment margin of the turbine bypass valve can be constantly ensured for the AFC signal that changes every moment, and a good followability to the AFC signal can be obtained.

(4) In another state, in any of the above (1) to (3), The aforementioned opening degree command value generation unit is composed of the base opening degree of the aforementioned turbine bypass valve (such as the basic opening degree Stb3base of the above-mentioned embodiment) when shifting to the aforementioned AFC corresponding mode, plus the deviation opening based on the aforementioned AFC signal degree (for example, the deviation opening degree Stb3bias in the above-mentioned embodiment), through which, the aforementioned opening degree command value is generated.

According to the aspect of (4) above, the opening degree control value of the turbine bypass valve is generated by adding the deviation opening degree to the base opening degree. The basic opening degree is used to maintain the opening degree of the turbine bypass valve when the thermal power plant is transferred from the normal mode to the AFC signal corresponding mode, and it is generated by adding the deviation value based on the AFC signal that changes every moment . 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 state, in the state of (4) above, The aforementioned basic opening degree is an intermediate opening degree between the fully open state and the fully closed state.

According to the aspect of (5) above, in the AFC compatible mode, the base opening degree used as the reference for the opening degree control of the turbine bypass valve is set to the intermediate opening degree. Accordingly, when changing the opening degree of the turbine bypass valve according to the AFC signal, the adjustment margin of the turbine bypass valve can be ensured regardless of the sign of the AFC signal, and good followability to the AFC signal can be obtained.

(6) In another state, in any one of the above (1) to (5), The aforementioned thermal power plant is further equipped with: a main steam valve (such as the main steam valve 8 of the above-mentioned embodiment) for adjusting the amount of main steam supplied from the aforementioned boiler to the aforementioned steam turbine; The aforementioned control device further has: The steam valve opening degree command value generating unit (such as the main steam valve opening degree command value generating unit 162 in the above-mentioned embodiment) is used to generate the steam valve opening degree command value (such as the main steam valve opening degree command value in the above-mentioned embodiment) according to the aforementioned AFC signal. steam valve opening command value Jd); and The main steam valve control unit (such as the main steam valve control unit 174 in the above-mentioned embodiment) is used to control the aforementioned main steam valve according to the aforementioned steam valve opening degree command value.

According to the above (6), the opening degree of the main steam valve is controlled according to the command value of the opening degree of the main steam valve, and the command value of the opening degree of the main steam valve is generated according to the AFC signal. After this, the main steam valve is coordinated with the turbine bypass valve that also controls the opening degree according to the AFC signal, thereby improving the followability of the AFC signal.

(7) In another state, in any of the above (1) to (6), It further includes: a deviation opening degree correction unit (for example, the deviation opening degree correction unit 200 of the above-mentioned embodiment) for correcting the deviation opening degree according to the load of the steam turbine.

According to the aspect of (7) above, by correcting the deviation of the opening degree according to the load of the steam turbine, the followability of the AFC signal due to the deviation of the opening degree can be improved in a wide load range of the steam turbine.

(8) In another state, in the state of (7) above, The deviation opening degree correcting unit corrects the deviation opening degree such that a correction amount increases as the load decreases.

According to the aspect of (8) above, the correction amount of the deviation opening degree is set to increase as the load of the steam turbine decreases. As a result, the followability of the AFC signal due to the deviation from the opening degree can be effectively improved on the low load side where the effect due to the deviation from the opening degree is relatively easy to decrease.

(9) In another state, in the state of (7) or (8) above, The above-mentioned deviation opening correction unit is based on the difference between the supply steam pressure of the steam turbine (such as the main steam pressure Ps in the above-mentioned embodiment) and the exhaust steam pressure (such as the turbine exhaust pressure Pse in the above-mentioned embodiment) (such as the above-mentioned The aforementioned load is obtained from the differential pressure ΔP′) of the embodiment.

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

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

According to the aspect of (10) above, the turbine bypass valve is installed in the bypass line connecting the upstream side and the downstream side of the steam turbine, for example, the opening degree is adjusted when the thermal power plant is started. The steam is sent to the downstream side of the steam turbine, and various components (reheater, etc.) located on the downstream side of the steam turbine can be properly protected.

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

According to the aspect of (11) above, with simpler control, when the turbine bypass valve is controlled based on the opening degree command value of the AFC signal, the turbine bypass valve can be ensured irrespective of the sign of the AFC signal. Opening degree adjustment margin (for example, the deviation opening degree correction part in (9) above can be set as unnecessary).

(12) Regarding the control method of one of the states, It is a control method of a thermal power plant (for example, the thermal power plants 1 and 1′ in the above-mentioned embodiment), the thermal power plant has: a boiler (for example, the boiler 2 in the above-mentioned embodiment), which is controlled by steam from the aforementioned boiler A driven steam turbine (such as the steam turbine 4 of the above-mentioned embodiment), and a turbine bypass valve (such as the turbine bypass valve 16 of the above-mentioned embodiment) for adjusting the amount of steam bypassing the aforementioned steam turbine; it is characterized in that the The control method has: In the AFC correspondence mode of the aforementioned thermal power plant, a basic input value (for example, the second command value D2 of the above-mentioned embodiment) based on a load command value (for example, the load command value L of the above-mentioned embodiment) for the aforementioned thermal power plant is added. The deviation value of the upper positive sign (such as the deviation value Dbias of the above-mentioned embodiment), through which, the process of generating the boiler input command value (such as the boiler input command value BID of the above-mentioned embodiment); Control the process of the aforementioned boiler according to the input command value of the aforementioned boiler; In the aforementioned AFC corresponding mode, a process of generating a turbine bypass valve opening degree command value of the aforementioned turbine bypass valve (such as the turbine bypass valve opening degree command value Stb in the above-mentioned embodiment) according to the AFC signal; and The process of controlling the turbine bypass valve according to the turbine bypass valve opening degree command value.

According to the above (12), in the AFC corresponding mode, the opening degree of the turbine bypass valve is controlled according to the opening degree command value generated based on the AFC signal, thereby obtaining good followability to the AFC signal. On the other hand, the boiler input command value is generated by adding a positive-signed deviation value to the basic input value based on the load command value. Thereby, when the turbine bypass valve is controlled by the opening degree command value based on the AFC signal, the opening degree adjustment margin of the turbine bypass valve can be ensured irrespective of the sign of the AFC signal.

(13) In another state, in the state of (12) above, By controlling the boiler with the boiler input command value, the turbine bypass valve is controlled based on the opening degree command value after the load of the boiler increases more than the load command value.

According to the aspect of (13) above, the load via the boiler increases more than the load command value, and the opening degree control of the turbine bypass valve is performed after the opening degree adjustment margin of the turbine bypass valve is ensured. As a result, when the opening degree of the turbine bypass valve is controlled based on the AFC signal, the opening degree can be adjusted corresponding to the AFC signal irrespective of whether the AFC signal is positive or negative, and good followability to the AFC signal can be obtained.

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 pipeline 12: Condenser 14: Bypass pipeline (1st bypass pipeline) 15: The second bypass pipeline 16: Turbine bypass valve (1st turbine bypass valve) 17: 2nd turbine bypass valve 100: Control device 110: Turbine bypass valve opening command value generating unit 112: The first opening degree command value calculation unit 120: The second opening degree command value calculation unit 130: The third opening degree command value calculation unit 132: Basic opening degree calculation department 134: Deviating from opening degree calculation department 140: Turbine bypass valve control unit 142: Boiler input command value generator 144: Hold circuit 160: boiler control department 162: Main steam valve opening command value generating unit 174: Main steam valve control department 200: Deviation opening degree correction department 206: Correction Department

[ Fig. 1 ] is a schematic configuration diagram of a thermal power plant according to an embodiment. [FIG. 2] It is a block diagram which shows the internal structure of the control apparatus of FIG. 1. [FIG. [FIG. 3] It is a control logic diagram of the turbine bypass valve opening degree command value generation part of FIG. 2. [FIG. [ Fig. 4 ] is an example of functions included in the function calculator of Fig. 3 . [FIG. 5] It is a control logic diagram of the boiler input command value generation part of FIG. 2. [FIG. [ FIG. 6 ] is one example of the deviation value obtained by the function calculator in FIG. 5 . [FIG. 7] It is a control logic diagram of the main steam valve opening degree command value generation part of FIG. 2. [FIG. [FIG. 8] It is a sequence flow chart which shows the temporal change of various signals in the control apparatus of FIG. 2. [FIG. [FIG. 9] It is a graph which shows the adjustment margin of a plant in a load command value. [ Fig. 10 ] is an overall configuration diagram of a thermal power plant according to another embodiment. [ Fig. 11] Fig. 11 is a part of a control logic diagram of a turbine bypass valve opening degree command value generator included in the control device of Fig. 10 . [ Fig. 12 ] is a graph showing the relationship between differential pressure and gain in the functional calculator of Fig. 11 .

2: Boiler

8: Main steam valve

16: Turbine bypass valve (1st turbine bypass valve)

100: Control device

110: Turbine bypass valve opening command value generating unit

140: Turbine bypass valve control unit

142: Boiler input command value generator

160: boiler control department

162: Main steam valve opening command value generating unit

174: Main steam valve control department

Claims (13)

A control device for a thermal power plant comprising: 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; its features The control device of the thermal power plant is provided with: a turbine bypass valve opening command value generation unit, which is used to generate the turbine bypass valve of the turbine bypass valve according to the AFC signal in the AFC corresponding mode of the thermal power plant. an opening degree command value of the bypass valve; a turbine bypass valve control unit for controlling the turbine bypass valve according to the turbine bypass valve opening degree command value; a boiler input command value generation unit for, In the aforementioned AFC correspondence mode, a positive-signed offset value is added to the basic input value based on the load command value of the aforementioned thermal power plant, thereby generating a boiler input command value; and the boiler control unit is used for, The boiler is controlled based on the boiler input command value. The control device for a thermal power plant according to claim 1, wherein the deviation value is constant regardless of the load command value in a range of the load command value or less. A control device for a thermal power plant as claimed in claim 2, wherein the aforementioned deviation value is set to be the same as the reference value for the aforementioned AFC signal corresponding to the maximum reduction value. The control device for a thermal power plant according to any one of Claims 1 to 3, wherein the aforementioned turbine bypass valve opening command value generating unit is configured to switch to the aforementioned AFC corresponding mode of the aforementioned turbine bypass valve The base opening degree is added to the deviation opening degree based on the aforementioned AFC signal to generate the aforementioned turbine bypass valve opening degree command value. The control device for a thermal power plant as claimed in claim 4, wherein the aforementioned basic opening degree is an intermediate opening degree between the fully open state and the fully closed state. The control device for a thermal power plant according to any one of claims 1 to 3, wherein the thermal power plant further includes: a main steam valve for adjusting the amount of main steam supplied from the boiler to the steam turbine; the control device It is further equipped with: a main steam valve opening degree command value generating unit, which is used to generate a main steam valve opening degree command value according to the aforementioned AFC signal; and a main steam valve control unit, which is used to generate a main steam valve opening degree command value according to the aforementioned main steam valve opening degree command value to control the aforementioned main steam valve. The control device for a thermal power plant according to claim 4, further comprising: a deviation opening degree correction unit for correcting the deviation opening degree according to the load of the steam turbine. The control device for a thermal power plant according to claim 7, wherein the deviation opening degree correction unit corrects the deviation opening degree so that the correction amount becomes larger as the load becomes smaller. The control device for a thermal power plant according to claim 7, wherein the deviation opening correction unit obtains the load based on a difference between a supply steam pressure and an exhaust steam pressure of the steam turbine. The control device for a thermal power plant according to any one of claims 1 to 3, wherein the turbine bypass valve is provided in a bypass line connecting the upstream side and the downstream side of the steam turbine. The control device for a thermal power plant according to any one of claims 1 to 3, wherein the turbine bypass valve is provided on a bypass line connecting the upstream side of the steam turbine and the condenser provided on the downstream side of the steam turbine . A method for controlling a thermal power plant, the thermal power plant comprising: 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; its features The control method includes: in the AFC corresponding mode of the thermal power plant, adding a positive-signed deviation value to the basic input value based on the load command value of the thermal power plant, thereby generating the boiler input command value The process of controlling the process of the aforementioned boiler according to the input command value of the aforementioned boiler; In the aforementioned AFC corresponding mode, a process of generating a turbine bypass valve opening command value of the turbine bypass valve according to the AFC signal; and a process of controlling the turbine bypass valve according to the turbine bypass valve opening command value. The control method of a thermal power plant according to claim 12, wherein, in such a manner that the boiler is controlled by the input command value of the boiler, after the load of the boiler increases more than the load command value, the turbine bypass valve is opened according to The degree command value controls the aforementioned turbine bypass valve.

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