JP6625848B2 - Steam control valve control device, power plant and steam control valve control method - Google Patents

Description

  Embodiments of the present invention relate to a steam control valve control device, a power plant, and a steam control valve control method.

  Generally, a power plant such as a thermal power plant includes a boiler, and a high-pressure turbine, a medium-pressure turbine, and a low-pressure turbine that are driven to rotate using steam supplied from the boiler. A generator is connected to the high-pressure turbine, the intermediate-pressure turbine, and the low-pressure turbine, and the generator is driven by the rotational driving force obtained by each turbine to generate power. Steam discharged from the low-pressure turbine is supplied to a condenser as turbine exhaust, and is condensed in the condenser to generate condensate. The generated condensate is supplied to a boiler and heated to generate steam.

  A steam control valve for controlling the flow rate of main steam supplied from the boiler is provided on the inlet side of the high-pressure turbine. The flow rate of the main steam is adjusted by the steam control valve, and turbine speed control and generator load control are performed. The steam control valve is composed of, for example, four valves (first to fourth valves), and the outlet of each valve is connected to a portion obtained by dividing the inlet nozzle of the high-pressure turbine into four parts. In this way, the main steam that has passed through each of the steam control valves is supplied to the corresponding portion of the inlet nozzle. During this time, the speed regulation operation of the high-pressure turbine is performed by adjusting the opening of each of the steam control valves.

  Generally, there are two speed control methods as a speed control operation method of a high-pressure turbine. One is a throttle speed control method (throttle governing), and the other is a nozzle speed control method (nozzle governing). Both approaches have advantages and disadvantages. For example, in the throttle governing method, since each valve is operated to have a uniform opening, the main steam can be supplied evenly to the inlet nozzle of the high-pressure turbine, and a temperature difference occurs at the inlet nozzle, resulting in heat. The generation of stress can be suppressed. However, in the throttle governing method, pressure loss occurs due to the restriction of the flow of the main steam during the partial load operation, and the plant efficiency may decrease. On the other hand, in the nozzle speed control method, since each valve is sequentially opened, it is possible to suppress a decrease in plant efficiency due to a flow pressure loss. However, in the nozzle speed control method, since main steam is partially supplied to the inlet nozzle, a temperature difference occurs in the inlet nozzle, and thermal stress may be generated. In consideration of such advantages and disadvantages, one of the speed control methods is selected according to load control and operating conditions required for the high-pressure turbine and the generator.

  FIG. 8 shows the opening / closing characteristics (lift curve) of the steam control valve in the nozzle speed control method. The horizontal axis in FIG. 8 shows the flow rate command value (turbine load) of the steam control valve according to the required flow rate of the high-pressure turbine, and the vertical axis shows the opening command value of the steam control valve. The lift curve is determined in consideration of the flow rate of the main steam to be supplied to the high-pressure turbine and the thermal stress of the high-pressure turbine, and the opening degree command value can be obtained from the lift curve as a value for the flow rate command value. . In this manner, the opening command value according to the lift curves La and Lb shown in FIG. 8 is given to each valve with respect to the flow command value, and the steam control valve is operated.

  In the example shown in FIG. 8, when the load is increased, such as when starting the turbine, the first to third valves are simultaneously opened according to the lift curve La from low load to about 90% of the rated load, and the same opening is performed. Increase in degrees. After the load exceeds 90%, the fourth valve is opened, and the opening of each valve is continuously increased. The opening degree of the fourth valve increases according to a lift curve Lb different from the lift curve La of the first to third valves. Operating the steam control valve by dividing the timing of opening each valve into two in this manner is called two admission. Operating the steam control valve by dividing the timing of opening each valve into three is called three admission. The two admissions and the three admissions are appropriately selected in consideration of the thermal stress generated in the nozzles and blades of the steam turbine.

JP 2005-291113 A JP 2001-263003 A

  When the degree of vacuum of the condenser is reduced due to a rise in the temperature of the cooling water or the like, the steam passing through the steam turbine cannot perform expansion work and may not be able to secure the rated load of the design value. Thus, the steam turbine is designed to output a maximum load obtained by adding a margin to the rated load of the design value. Along with this, the steam control valve is also designed so that it can flow at a flow rate larger than the rated flow rate at the design value, and a margin is added to the rated opening degree at the design value (75% opening degree shown in FIG. 8). It opens up to the maximum opening (100% opening). As a result, during the rated load operation, the opening degrees of the first to third valves that were opened earlier are smaller than the maximum opening degrees, and the steam control valve is operated as a throttle as a whole. For this reason, a pressure loss occurs due to the throttle operation, which has been a factor that can reduce the plant efficiency.

  The present invention has been made in view of the above points, and has a steam control valve control device, a power generation plant, and a steam control capable of reducing pressure loss of steam during rated load operation and improving plant efficiency. It is an object to provide a valve control method.

  The steam control valve control device according to the embodiment controls a steam control valve having a leading large opening valve, a leading small opening valve, and a trailing valve based on a flow rate command value corresponding to a turbine load. This steam control valve control device includes a first opening command section, a second opening command section, and a third opening command section. The first opening command unit gives an opening command to the preceding large opening valve according to the first opening / closing characteristic. The second opening degree command unit is a second opening / closing characteristic having the same opening degree as the opening degree of the first opening / closing characteristic when the flow rate command value is smaller than the first flow rate command value. An opening command is given to the preceding small opening valve according to the second opening / closing characteristic having an opening smaller than the opening of the first opening / closing characteristic when the flow rate is equal to or more than the flow command value. The third opening command section gives the 0% opening command to the following valve when the flow command value is smaller than the second flow command value larger than the first flow command value, and sets the flow command value to the second flow rate. When it is equal to or more than the command value, an opening command is given to the following valve according to the third opening / closing characteristic having an opening smaller than the opening of the second opening / closing characteristic.

  Further, the power plant according to the embodiment includes a steam generator, a high-pressure turbine that is rotationally driven by using steam supplied from the steam generator, and a steam control valve that controls a flow rate of steam supplied to the high-pressure turbine. And the above-described steam control valve control device for controlling the steam control valve.

  Further, the steam control valve control method according to the embodiment controls a steam control valve having a leading large opening valve, a leading small opening valve, and a trailing valve based on a flow rate command value corresponding to a turbine load. In this steam control valve control method, when the load increases, first, the leading large opening valve and the leading small opening valve are opened, and the opening of the leading large opening valve is increased until the flow command value becomes the first flow command value. At the same time, the opening of the preceding small opening valve is increased so as to be the same as the opening of the preceding large opening valve. Subsequently, when the flow command value becomes the first flow command value, the opening of the preceding small opening valve is made smaller than the opening of the preceding large opening valve, and the opening of the preceding small opening valve becomes The opening of the leading large opening valve and the opening of the leading small opening valve are increased while maintaining a relationship smaller than the opening of the large opening valve. Next, when the flow command value becomes the second flow command value larger than the first flow command value, the following valve is opened, and the opening of the following valve is smaller than the opening of the preceding small opening valve. While maintaining the relationship, the opening degree of the leading small opening valve and the opening degree of the following valve are increased.

  ADVANTAGE OF THE INVENTION According to this invention, the pressure loss of the steam during rated load operation can be reduced, and plant efficiency can be improved.

FIG. 1 is a schematic system diagram showing the entire configuration of the power plant according to the first embodiment. FIG. 2 is a conceptual diagram for explaining an example of the configuration of the steam control valve of FIG. FIG. 3 is a diagram showing a lift curve of the steam control valve of FIG. FIG. 4 is a block diagram illustrating an example of a configuration of a steam control valve control device that controls the steam control valve of FIG. 3. FIG. 5 is a diagram illustrating a lift curve of the steam control valve according to the second embodiment. FIG. 6 is a diagram illustrating a lift curve of the steam control valve according to the third embodiment. FIG. 7 is a block diagram illustrating an example of a configuration of a steam control valve control device that controls the steam control valve of FIG. 6. FIG. 8 is a diagram showing a lift curve of a general steam control valve.

  Hereinafter, a steam control valve control device, a power plant, and a steam control valve control method according to an embodiment of the present invention will be described with reference to the drawings.

(First Embodiment)
The steam control valve control device, the power plant, and the steam control valve control method according to the first embodiment will be described with reference to FIGS. 1 to 4. First, a thermal power plant as an example of a power plant will be described with reference to FIG.

  As shown in FIG. 1, the thermal power plant 1 includes a boiler 2, a steam turbine unit 3, and a condenser 4.

  The boiler 2 includes a steam generator 5 that heats the condensate supplied from the condenser 4 to generate steam, and a reheater 6 that superheats main steam S1 that has completed expansion work in a high-pressure turbine 7 described below. ,have. The boiler 2 mixes the supplied fuel with air, burns the fuel to generate combustion gas, and generates steam from condensate in the steam generator 5 using heat of the generated combustion gas. At 6 the steam is superheated.

  The steam turbine section 3 has a high-pressure turbine 7, an intermediate-pressure turbine 8, and a low-pressure turbine 9. The turbine rotors (not shown) of the high-pressure turbine 7, the intermediate-pressure turbine 8, and the low-pressure turbine 9 are connected to each other.

  The steam generated in the steam generator 5 is supplied to the high-pressure turbine 7 via the main steam system 10 as main steam S1. The high-pressure turbine 7 is rotationally driven using main steam S1 supplied from the steam generator 5. That is, the main steam S1 supplied to the high-pressure turbine 7 performs expansion work, and the high-pressure turbine 7 obtains a rotational driving force. After the expansion work, the main steam S1 is supplied to the reheater 6 through the low-temperature reheat system 12 having the check valve 11.

  The steam superheated in the reheater 6 is supplied to the intermediate pressure turbine 8 via the reheat steam system 13 as reheat steam S2. The reheat steam S2 supplied to the intermediate pressure turbine 8 performs expansion work, and the intermediate pressure turbine 8 obtains a rotational driving force. The reheated steam S2 that has completed the expansion work is supplied to the low-pressure turbine 9 to further perform expansion work, and thereafter, is supplied to the condenser 4 as turbine exhaust.

  The turbine exhaust gas supplied to the condenser 4 is condensed and condensed. The condenser 4 and the steam generator 5 of the boiler 2 are connected by a condensate water supply system 14, and the condensate water supply system 14 has a water supply pump 15. Thus, the condensate in the condenser 4 is pressurized by the water supply pump 15 and supplied to the steam generator 5 of the boiler 2.

  In this way, the high-pressure turbine 7, the intermediate-pressure turbine 8, and the low-pressure turbine 9 obtain rotational driving force, and the generator 16 (see FIG. 2) is driven to generate electric power.

  The above-described main steam system 10 has a main steam stop valve 20 and a steam control valve 21 provided downstream of the main steam stop valve 20. Among them, the main steam stop valve 20 is mainly for stopping the flow of the main steam S1 in an emergency such as when the load is cut off, and the steam control valve 21 is mainly used for stopping the main steam S1 supplied to the high-pressure turbine 7. This is for adjusting (controlling) the flow rate. A high-pressure turbine bypass system 22 branches from a portion of the main steam system 10 upstream of the main steam stop valve 20. The high-pressure turbine bypass system 22 has a high-pressure turbine bypass valve 23 and joins the low-temperature reheat system 12. In this way, the main steam S1 can be supplied to the low-temperature reheating system 12 without being supplied to the high-pressure turbine 7. For example, when the pressure or temperature of the main steam S1 does not reach a predetermined value at the time of load increase such as when starting the turbine, or when the flow rate of the main steam S1 becomes excessive in an emergency such as when the load is cut off, the high-pressure turbine The operation of opening the bypass valve 23 and supplying the surplus main steam S1 to the low-temperature reheating system 12 is performed.

  The reheat steam system 13 has a reheat steam stop valve 24 and a reheat steam control valve 25 (intercept valve) provided downstream of the reheat steam stop valve 24. Of these, the reheat steam stop valve 24 is mainly for stopping the flow of the reheat steam S2 in an emergency, and the reheat steam control valve 25 is mainly for controlling the reheat steam supplied to the intermediate pressure turbine 8. This is for adjusting (controlling) the flow rate of S2. A low-pressure turbine bypass system 26 branches from a portion of the reheat steam system 13 upstream of the reheat steam stop valve 24. The low-pressure turbine bypass system 26 has a low-pressure turbine bypass valve 27 and is connected to the condenser 4. In this way, the reheat steam S2 can be supplied to the condenser 4 without being supplied to the intermediate-pressure turbine 8 and the low-pressure turbine 9. For example, similarly to the high-pressure turbine bypass valve 23, when the pressure or temperature of the main steam S1 does not reach a predetermined value when the load is increased, or when the flow rate of the main steam S1 becomes excessive in an emergency such as when the load is cut off. Then, an operation is performed in which the low-pressure turbine bypass valve 27 is opened and the surplus reheat steam S2 is supplied to the condenser 4.

  The steam control valve control device 30 in the present embodiment is for controlling the steam control valve 21 of the main steam system 10 described above. More specifically, the steam control valve control device 30 controls the steam control valve 21 based on a flow rate command value of the steam control valve 21 according to the turbine load of the steam turbine unit 3. The flow command value is given from a plant control device (not shown) of the thermal power plant 1 shown in FIG. 1 to the steam control valve control device 30. Hereinafter, the steam control valve 21 controlled by the steam control valve control device 30 will be described in more detail.

  As shown in FIG. 2, the steam control valve 21 according to the present embodiment has a leading large opening valve, a leading small opening valve, and a trailing valve. Among these, the leading large opening valve includes a first leading large opening valve and a second leading large opening valve. In the present embodiment described below, the first leading large opening valve is a first valve 21a, the second leading large opening valve is a second valve 21b, the leading small opening valve is a third valve 21c, and the following valve is used. The valve is a fourth valve 21d. The first valve 21a, the second valve 21b, the third valve 21c, and the fourth valve 21d are controlled by the steam control valve control device 30 according to the present embodiment.

  As shown in FIG. 2, the outlets of the valves 21a to 21d are connected to the inlet nozzles 7a of the high-pressure turbine 7 divided into four parts. As a result, the main steam S1 that has passed through each of the valves 21a to 21d is supplied to a corresponding portion of the inlet nozzle 7a. Thus, the main steam S1 is supplied to the inlet nozzle 7a, the main steam S1 performs expansion work in the high-pressure turbine 7, and the high-pressure turbine 7 is configured to obtain a rotational driving force.

  The opening degrees of the first to fourth valves 21a to 21d of the steam control valve 21 are adjusted according to the opening / closing characteristics as shown in FIG. More specifically, the opening of the first valve 21a and the opening of the second valve 21b are adjusted according to the first lift curve L1 (first opening / closing characteristic) according to the flow rate command value. The opening degree of the third valve 21c is adjusted according to the second lift curve L2 (second opening / closing characteristic) according to the flow rate command value, and the opening degree of the fourth valve 21d is adjusted according to the flow rate command value. (Third opening / closing characteristics). The fourth valve 21d is closed while the flow command value is smaller than a second flow command value Q2 described later. Further, each of the lift curves L1 to L3 is set such that when the control valve opening degree command value becomes 75% as the flow rate command value increases, the subsequent opening degree command value is maintained at 75%. . Here, the 75% opening means the rated opening of each of the valves 21a to 21d. The 100% opening described later means the maximum opening of each of the valves 21a to 21d.

  The second lift curve L2 has the same opening as the opening of the first lift curve L1 when the flow command value is smaller than the first flow command value Q1, and the flow command value is equal to or more than the first flow command value Q1. , The opening degree is smaller than the opening degree of the first lift curve L1. That is, the second lift curve L2 has such a characteristic that the second lift curve L2 branches off from the first lift curve L1 at the point where the flow rate command value becomes the first flow rate command value Q1. The third lift curve L3 has such a characteristic that the fourth valve 21d is opened at an opening smaller than the opening of the second lift curve L2 when the flow command value is equal to or larger than the second flow command value Q2. ing. Thus, the steam control valve 21 according to the present embodiment is operated with two admissions. If the flow command value during the rated load operation is a rated flow command value Qr, the above-described second flow command value Q2 is smaller than the rated flow command value Qr.

  In the present embodiment, as shown in FIG. 3, when the flow rate command value is equal to or greater than a third flow rate command value Q3 which is larger than the first flow rate command value Q1 and smaller than the second flow rate command value Q2, The opening of the first valve 21a and the opening of the second valve 21b may deviate from the first lift curve L1 and may be set to 100% opening. Note that the first lift curve L1 in the range equal to or more than the third flow rate command value Q3 according to the present embodiment is indicated by a thick broken line in FIG.

  Next, the configuration of the steam control valve control device 30 that controls the steam control valve 21 having the above-described opening and closing characteristics will be described with reference to FIG.

  As shown in FIG. 4, the steam control valve control device 30 includes a first opening degree command unit 31 that gives an opening degree command to the first valve 21a and the second valve 21b according to the first lift curve L1, and a second lift curve L2. And a third opening command section 33 for giving an opening command to the fourth valve 21d according to the third lift curve L3.

  The first opening command unit 31 converts a flow command value to create an opening command value to be provided to the first valve 21a, and a first conversion function generator 34 that converts the flow command value to a second valve. And a second conversion function generator 35 for creating an opening degree command value to be given to the opening 21b.

  The first lift function L1 shown in FIG. 3 is stored in the first conversion function generator 34 in advance. The first lift curve L1 shows the relationship between the flow command value given to the steam control valve control device 30 and the opening command values of the first valve 21a and the second valve 21b. When the flow rate command value is given to the steam control valve control device 30, the first conversion function generator 34 determines an opening degree command value corresponding to the flow rate command value from the first lift curve L1.

  The second conversion function generator 35 is configured similarly to the first conversion function generator 34. That is, the first lift curve L1 shown in FIG. 3 is stored in the second conversion function generator 35 in advance, and the opening command value is obtained from the first lift curve L1.

  The first opening degree command unit 31 opens the first valve 21a and the second valve 21b 100% when the flow rate command value is equal to or more than the third flow rate command value Q3 both when the load is increased and when the load is decreased. It is configured to give a degree.

  That is, the first opening command unit 31 determines the bias based on the flow rate command value and determines whether or not to add a bias to the opening command value. And a bias function generator 37 for generating. The bias determining unit 36 determines whether the flow command value received by the steam control valve control device 30 is equal to or more than the third flow command value Q3, and determines whether the flow command value is equal to or more than the third flow command value Q3. If it is determined that there is, a bias command for generating a bias is given to the bias function generator 37. The bias function generator 37 generates a bias when a bias command is given from the bias determination unit 36.

  The first opening command section 31 includes a first adder 38 that adds the bias generated by the bias function generator 37 to the opening command value created by the first conversion function generator 34, and a bias function generator 37. And a second adder 39 that adds the bias generated in step (2) to the opening command value created by the second conversion function generator 35. As a result, the bias generated by the bias function generator 37 is added to the opening command value created by the first conversion function generator 34, and the opening command value given to the first valve 21a becomes 100% open. Degree command value. Similarly, the bias generated by the bias function generator 37 is added to the opening command value created by the second conversion function generator 35, and the opening command value given to the second valve 21b is 100% opening. It becomes.

  The opening command value created as described above is given to the first valve 21a and the second valve 21b, respectively. More specifically, when the flow rate command value is smaller than the third flow rate command value Q3, the opening degree command value created by the first conversion function generator 35 is given to the first valve 21a, and the second valve The opening command value created by the second conversion function generator 36 is given to 21b. The valve body (not shown) of the first valve 21a is driven based on the given opening command value, and the opening of the first valve 21a is adjusted to the opening indicated by the opening command value. Similarly, the opening of the second valve 21b becomes the opening indicated by the opening command value. When the flow rate command value is equal to or greater than the third flow rate command value Q3, a 100% opening command value is given to the first valve 21a and the second valve 2b, respectively, and the opening degree of the first valve 21a and the second valve The opening of 21b becomes 100% opening.

  The second opening command unit 32 has a third conversion function generator 40 that converts the flow command value and creates an opening command value to be given to the third valve 21c. The third lift function L2 shown in FIG. 3 is stored in the third conversion function generator 40 in advance. The second lift curve L2 indicates the relationship between the flow rate command value given to the steam control valve control device 30 and the opening command value of the third valve 21c. When the flow rate command value is given to the steam control valve controller 30, the third conversion function generator 40 obtains an opening degree command value corresponding to the flow rate command value from the second lift curve L2.

  When the flow rate command value is equal to or more than the second flow rate command value Q2, the third opening degree command unit 33 converts the flow rate command value and generates an opening degree command value to be given to the fourth valve 21d. It has a function generator 41. The third lift curve L3 shown in FIG. 3 is stored in the fourth conversion function generator 41 in advance. The third lift curve L3 indicates the relationship between the flow rate command value given to the steam control valve controller 30 and the opening command value of the fourth valve 21d. When the flow rate command value is given to the steam control valve controller 30, the fourth conversion function generator 41 obtains an opening degree command value corresponding to the flow rate command value from the third lift curve L3. Further, the third opening command section 33 gives a 0% opening command value to the fourth valve 21d when the flow command value is smaller than the second flow command value Q2. In this case, the fourth valve 21d is closed.

  Next, the operation of the present embodiment having such a configuration, that is, a steam control valve control method will be described.

  Here, first, the transition of the opening degree of the first valve 21a to the fourth valve 21d of the steam control valve 21 when the load is increased, such as when the turbine is started, will be described. In this case, the flow command value given to the steam control valve 21 increases.

  First, as shown in FIG. 3, the first valve 21a, the second valve 21b, and the third valve 21c are simultaneously opened. Then, as the flow command value increases, the opening of the first valve 21a and the opening of the second valve 21b increase according to the first lift curve L1 until the flow command value becomes the first flow command value Q1. To go. Similarly, the opening of the third valve 21c increases according to the second lift curve L2 until the flow command value becomes the first flow command value Q1. During this time, the opening of the third valve 21c increases so as to be the same as the opening of the first valve 21a and the opening of the second valve 21b. Thus, the flow rate of the main steam S1 passing through the steam control valve 21 is secured. On the other hand, during this time, the fourth valve 21d is closed. The flow rate of the steam passing through the steam control valve 21 during this time is adjusted by regulating the throttle, that is, adjusting the opening of the first valve 21a, the opening of the second valve 21b, and the opening of the third valve 21c. You.

  Subsequently, when the flow command value becomes the first flow command value Q1, the opening of the third valve 21c becomes smaller than the opening of the first valve 21a and the opening of the second valve 21b. Then, as the flow command value increases, the opening of the first valve 21a is maintained while maintaining the relationship in which the opening of the third valve 21c is smaller than the opening of the first valve 21a and the opening of the second valve 21b. The opening of the second valve 21b increases according to the first lift curve L1, and the opening of the third valve 21c increases according to the second lift curve L2. During this time, the opening of the first valve 21a and the opening of the second valve 21b are the same. On the other hand, during this time, the fourth valve 21d is still closed. The flow rate of the steam passing through the steam control valve 21 during this time is adjusted by regulating the throttle, that is, adjusting the opening of the first valve 21a, the opening of the second valve 21b, and the opening of the third valve 21c. You.

  Next, when the flow command value becomes the third flow command value Q3, a 100% opening command is given to the first valve 21a and the second valve 21b. Thus, the opening of the first valve 21a and the opening of the second valve 21b become 100%. While the flow command value is equal to or more than the third flow command value Q3, the opening of the first valve 21a and the opening of the second valve 21b are maintained at 100%. During this time, the flow rate of the steam passing through the steam control valve 21 is adjusted by regulating the throttle, that is, adjusting the opening of the third valve 21c.

  Subsequently, when the flow command value becomes the second flow command value Q2, the fourth valve 21d is opened. As a result, the steam control valve 21 according to the present embodiment is operated with two admissions, and nozzle speed control is performed. Then, as the flow command value increases, the opening of the fourth valve 21d and the opening of the third valve 21c and the opening of the fourth valve 21d are maintained while maintaining a relationship smaller than the opening of the third valve 21c. The degree increases according to the third lift curve L3. During this time, as described above, the opening of the first valve 21a and the opening of the second valve 21b are maintained at 100%. Thus, pressure loss due to the restriction of the main steam S1 passing through the first valve 21a and the second valve 21b can be reduced. The flow rate of the main steam S1 passing through the steam control valve 21 during this time is adjusted by regulating the throttle, that is, adjusting the opening of the third valve 21c and the opening of the fourth valve 21d. Since the opening of 21d is smaller than the opening of the third valve 21c, the opening of the fourth valve 21d tends to be affected more than the opening of the third valve 21c.

  Thereafter, the flow command value reaches the rated flow command value Qr corresponding to the rated load, and the overall opening of the steam control valve 21 becomes the rated opening. In this case, the rated load operation of the steam control valve 21 is performed. At this time, since the opening of the first valve 21a and the opening of the second valve 21b are 100%, the pressure loss due to the restriction of the main steam S1 passing through the first valve 21a and the second valve 21b is reduced. Can be reduced. The third valve 21c has an opening slightly smaller than the 100% opening, but has an opening larger than the fourth valve 21d, and is formed by restricting the main steam S1 passing through the third valve 21c. Pressure loss can also be reduced.

  When the load of the steam control valve 21 that is performing the rated load operation is reduced, for example, when the load of the steam control valve 21 is reduced, such as when the turbine is stopped, the opening degree of the first to fourth valves 21a to 21d of the steam control valve 21 is determined. Since the transition follows the transition of the opening degree of the first valve 21a to the fourth valve 21d when the load increases, the detailed description is omitted here.

  As described above, according to the present embodiment, when the flow command value is equal to or greater than the first flow command value Q1, the opening of the third valve 21c is changed to the opening of the first valve 21a and the opening of the second valve 21b. An opening command is given to the first valve 21a, the second valve 21b, and the third valve 21c of the steam control valve 21 so as to be smaller. Thus, during the rated load operation, the opening of the first valve 21a and the opening of the second valve 21b can be made larger than the opening of the third valve 21c, and the first valve 21a and the second valve 21b Pressure loss due to the restriction of the main steam S1 passing through the main steam S1. Therefore, the pressure loss of the main steam S1 passing through the steam control valve 21 during the rated load operation can be reduced, and the plant efficiency of the thermal power plant 1 can be improved.

  Further, according to the present embodiment, when the flow rate command value is equal to or more than the third flow rate command value Q3, a 100% opening command is given to the first valve 21a and the second valve 21b of the steam control valve 21. . As a result, the opening of the first valve 21a and the opening of the second valve 21b can be made 100%, and the pressure loss due to the restriction of the main steam S1 passing through the first valve 21a and the second valve 21b. Can be further reduced. Therefore, the pressure loss of the steam passing through the steam control valve 21 during the rated load operation can be further reduced.

  In the above-described embodiment, the first opening degree command unit 31 has the first conversion function generator 34 and the second conversion function generator 35, and is separately provided for the first valve 21a and the second valve 21b. The example in which the opening command is given to the CPU has been described. However, the present invention is not limited to this. If an opening command can be given to the first valve 21a and the second valve 21b, the first opening command unit 31 outputs the first command from one of the conversion function generators. An opening command may be given to the valve 21a and the second valve 21b.

  Further, in the above-described embodiment, the preceding large opening valve has the first valve 21a and the second valve 21b that follow the first lift curve L1, and the steam control valve 21 operated with two admissions is taken as an example. explained. However, it is not limited to this. For example, the second valve 21b is opened following the first valve 21a and the third valve 21c and opened before the fourth valve 21d when the turbine is started, without following the first lift curve L1. You may make it operate in a mission.

  Further, the variable pressure operation may be applied to the steam control valve 21 according to the present embodiment described above. Here, the variable pressure operation is an operation for reducing the pressure of the main steam S1 generated from the steam generator 5 at the time of the partial load operation so as to match the turbine load and improving the reduction of the plant thermal efficiency. When the variable pressure operation is applied, for example, in a desired range (for example, a load range of 30% to 90%) of the flow rate command value in a range between the first flow rate command value Q1 and the third flow rate command value Q3, Preferably, a variable pressure operation is performed.

  Further, in the above-described embodiment, the thermal power plant 1 has been described as an example of the power plant. However, the present invention is not limited to this, and the power plant may be, for example, a nuclear power plant, and the present embodiment can be applied to any power plant in which a steam turbine is installed.

(Second embodiment)
Next, a steam control valve control device, a power generation plant, and a steam control valve control method according to the second embodiment will be described with reference to FIG.

  In the second embodiment shown in FIG. 5, when the load drops, a 100% opening command is given to the preceding large opening valve until the flow command value that is equal to or more than the third flow command value becomes the fourth flow command value. It is mainly different in that the 100% opening command of the preceding large opening valve is released when the flow command value becomes less than the fourth flow command value, and the other configuration is different from the first embodiment shown in FIGS. This is almost the same as the embodiment. In FIG. 5, the same parts as those in the first embodiment shown in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description is omitted.

  In the present embodiment, as shown in FIG. 5, when the load drops, the flow command value that is equal to or more than the third flow command value Q3 becomes the fourth flow command value Q4 that is smaller than the third flow command value Q3. The opening of the first valve 21a and the opening of the second valve 21b of the steam control valve 21 become 100%. When the flow rate command value is less than the fourth flow rate command value Q4, the opening degree of the first valve 21a and the opening degree of the second valve 21b are the opening degrees according to the first lift curve L1. Note that the fourth flow rate command value Q4 is a flow rate command value larger than the first flow rate command value Q1.

  In this case, the first opening degree command unit 31 of the steam control valve control device 30 determines that the flow rate command value is greater than or equal to the third flow rate command value Q3 in the process of shifting to less than the fourth flow rate command value Q4. A 100% opening command is given to the first valve 21a and the second valve 21b until the fourth flow command value Q4 is reached, and when the flow command value becomes less than the fourth flow command value Q4, the first valve 21a and the second The 100% opening command of the two valves 21b is released.

  That is, the bias judging section 36 of the first opening degree command section 31 determines that the flow rate command value given to the steam control valve control device 30 is changed from the flow rate command value equal to or more than the third flow rate value Q3 to less than the fourth flow rate command value Q4. It is determined whether or not the flow rate decreases, and whether or not the flow rate command value is equal to or greater than the fourth flow rate command value Q4. Then, the bias determining unit 36 determines that the flow command value decreases from the flow command value equal to or more than the third flow command value Q3 to less than the fourth flow command value Q4, and the flow command value is changed to the fourth flow command value. When it is determined that the value is equal to or more than the value Q4, a bias command for generating a bias is given to the bias function generator 37. On the other hand, when determining that the flow rate command value has become less than the fourth flow rate command value Q4, the bias determination unit 36 cancels the bias command to the bias function generator 37. In this case, since the bias function generator 37 does not generate a bias, the bias is not added to the opening degree command value created by the first conversion function generator 34, and the first valve 21a and the second valve 21b are not added. Given to.

  As shown in FIG. 5, when the load drops such as when the turbine is stopped, for example, when the load of the steam control valve 21 that has been performing the rated load operation is reduced, the flow command value given to the steam control valve 21. Decreases. Until the flow command value becomes the fourth flow command value Q4, a 100% opening command is given to the first valve 21a and the second valve 21b. That is, even when the flow command value is less than the third flow command value Q3, the 100% opening command is issued to the first valve 21a and the second valve 21b while the flow command value is equal to or more than the fourth flow command value Q4. Given. Thus, the opening of the first valve 21a and the opening of the second valve 21b are maintained at 100%.

  When the flow command value becomes less than the fourth flow command value Q4, the 100% opening commands of the first valve 21a and the second valve 21b are released. Thus, the opening of the first valve 21a and the opening of the second valve 21b are reduced to the opening according to the first lift curve L1, and return to the first lift curve L1. Thereafter, as the flow command value decreases, the opening of the first valve 21a and the opening of the second valve 21b decrease according to the first lift curve L1.

  As described above, according to the present embodiment, even when the flow rate command value is less than the third flow rate command value Q3 at the time of load reduction, the opening degree of the first valve 21a and the opening degree of the second valve 21b are reduced. Is set to 100%, and when it becomes less than the fourth flow rate command value Q4, the opening of the first valve 21a and the opening of the second valve 21b can be returned to the opening according to the first lift curve L1. As a result, the timing at which the opening of the first valve 21a and the opening of the second valve 21b are set to 100% (throwing up), and the opening of the first valve 21a and the opening of the second valve 21b are set to 100% The timing of returning from the opening to the opening according to the first lift curve L1 (pushing down) can be shifted, and hysteresis can be provided. Therefore, even when the flow rate command value fluctuates reciprocally due to frequency fluctuation or the like in the vicinity of the third flow rate command value Q3, the opening degree of the first valve 21a and the opening degree of the second valve 21b are determined by the first lift curve L1 Can be prevented from reciprocating between the opening degree according to (1) and the 100% opening degree. As a result, the flow rate of the main steam S1 supplied to the high-pressure turbine 7 can be prevented from fluctuating, and the supply of the main steam S1 can be stabilized.

  The variable pressure operation may be applied to the steam control valve 21 according to the present embodiment described above. In this case, for example, the variable pressure operation is performed in a desired range (for example, a load range of 30% to 90%) in the range between the fourth flow rate command value Q4 and the third flow rate command value Q3. It is preferred that

(Third embodiment)
Next, a steam control valve control device, a power generation plant, and a steam control valve control method according to the third embodiment will be described with reference to FIGS. 6 and 7.

  In the third embodiment shown in FIGS. 6 and 7, when the flow rate command value is equal to or more than the fourth flow rate command value and equal to or less than the third flow rate command value when the load drops, the opening degree of the second opening / closing characteristic is higher than the opening degree The main difference is that a branch opening command is given to the preceding small opening valve in accordance with the branch opening / closing characteristic having a small opening, and the other configuration is substantially the same as that of the second embodiment shown in FIG. In FIGS. 6 and 7, the same parts as those in the second embodiment shown in FIG. 5 are denoted by the same reference numerals, and detailed description is omitted.

  In the present embodiment, as shown in FIG. 6, when the flow rate command value is equal to or more than the fourth flow rate command value Q4 and is equal to or less than the third flow rate command value Q3 at the time of load drop, according to the branch curve L4 (branch opening / closing characteristic). A branch opening command is given to the third valve 21c. The branch curve L4 has an opening smaller than the opening of the second lift curve L2, and has a characteristic of branching from the second lift curve L2. In the branch curve L4 shown in FIG. 6, the opening command value gradually decreases as the flow command value decreases. Then, when the flow command value is less than the fourth flow command value Q4, the opening of the third valve 21c is the opening according to the second lift curve L2.

  In this case, the second opening degree command section 32 of the steam control valve control device 30 determines that the flow rate command value is equal to or less than the third flow rate command value Q3 in the process of shifting to the flow rate command value less than the fourth flow rate command value Q4. While the flow rate is equal to or higher than the fourth flow rate command value Q4 and equal to or lower than the third flow rate command value Q3, a branch opening command is given to the third valve 21c according to the branch curve L4. The second opening command unit 32 cancels the branch opening command for the third valve 21c when the flow command value becomes smaller than the fourth flow command value Q4.

  That is, the second opening command unit 32 determines whether the opening command value follows the branch curve L4 branched from the second lift curve L2, based on the flow command value, and a branch determination unit 42, And a branch function generator 43 that converts a flow rate command value based on the determination of the branch determination unit 42 to create a branch opening command value to be given to the third valve 21c. The branch determination unit 42 determines whether the flow command value given to the steam control valve control device 30 is equal to or more than the fourth flow command value Q4 and equal to or less than the third flow command value Q3. However, when it is determined that the value is equal to or more than the fourth flow rate command value Q4 and equal to or less than the third flow rate command value Q3, a branch command is given to the branch function generator 43. The branch function generator 43 stores a branch curve L4 shown in FIG. 6 in advance. The branch curve L4 indicates the relationship between the flow command value given to the steam control valve control device 30 and the opening command value of the third valve 21c. When a flow rate command value is given to the steam control valve controller 30, the branch function generator 43 obtains a branch opening command value corresponding to the flow rate command value from the branch curve L4.

  The second opening command section 32 generates the opening command value generated by the third conversion function generator 40 by the branch function generator 43 when the branch opening command value is generated by the branch function generator. And a function switch 44 for switching to the set branch opening command value. Thereby, the branch opening command value is given to the third valve 21c. In this way, when the flow rate command value is equal to or more than the fourth flow rate command value Q4 and equal to or less than the third flow rate command value Q3, the branch opening degree command is given to the third valve 21c.

  On the other hand, the second opening command unit 32 cancels the branch opening command of the third valve 21c when the flow command value becomes smaller than the fourth flow command value Q4. More specifically, when determining that the flow command value is less than the fourth flow command value Q4, the branch determination unit 42 cancels the branch command to the branch function generator 43. In this case, since the branch function generator 43 does not create the branch opening command value, the opening command value created by the third conversion function generator 40 is not switched to the branch opening command value and the third valve 21c.

  It is preferable that the second opening command section 32 cancels the branch opening command of the third valve 21c after a lapse of a predetermined time from when the flow command value becomes the fourth flow command value Q4. For example, the branch determination section 42 of the second opening degree command section 32 may have a return timer 45, and the return timer 45 determines that a predetermined time has elapsed since the flow rate command value became the fourth flow rate command value Q4. The branch command may be canceled later. In this case, the branch opening command by the second opening command unit 32 can be released after a predetermined time has elapsed (for example, about several seconds to 10 seconds) after the flow rate command value became the fourth flow rate command value Q4. Thereby, the timing at which the opening of the third valve 21c increases and the timing at which the opening of the first valve 21a and the opening of the second valve 21b decrease can be shifted, and the gas passes through the steam control valve 21. Temporarily increasing the flow rate of the main steam S1 can be suppressed.

  As shown in FIG. 6, when the load drops such as when the turbine is stopped, for example, when the load of the steam control valve 21 that has been performing the rated load operation is reduced, the flow command value given to the steam control valve 21. Decreases. While the flow rate command value is equal to or greater than the fourth flow rate command value Q4 and equal to or less than the third flow rate command value Q3, a branch opening degree command is given to the third valve 21c. Specifically, when the flow rate command value decreases and reaches the third flow rate command value Q3, a branch opening command according to the branch curve L4 is given to the third valve 21c. Thus, an opening command value smaller than the opening of the second lift curve L2 is given to the third valve 21c, and the opening of the third valve 21c becomes smaller than the opening when the load increases. This branch opening degree command is continued until the flow rate command value becomes the fourth flow rate command value Q4.

  When the flow command value becomes less than the fourth flow command value Q4, the branch opening command of the third valve 21c is released. In this case, as described above, the branch opening degree command of the third valve 21c may be canceled after a predetermined time has elapsed since the flow rate command value became the fourth flow rate command value Q4. When the branch opening command is released, the opening of the third valve 21c increases to the opening according to the second lift curve L2, and returns to the second lift curve L2. Thereafter, as the flow command value decreases, the opening of the third valve 21c decreases according to the second lift curve L2.

  As described above, according to the present embodiment, when the flow rate command value is equal to or more than the fourth flow rate command value Q4 and equal to or less than the third flow rate command value Q3 at the time of load reduction, the opening degree is smaller than the opening degree of the second lift curve L2. A branch opening command is given to the third valve 21c according to the branch curve L4 having a degree. Thus, the opening of the third valve 21c during this time can be reduced. Since the opening degree of the first valve 21a and the opening degree of the second valve 21b are 100%, the flow rate of the main steam S1 passing through the steam control valve 21 may be excessive. By reducing the opening of 21c, it is possible to suppress the flow rate of the main steam S1 passing through the steam control valve 21 from becoming excessive.

  Further, according to the present embodiment, at the time of load reduction, if the flow rate command value becomes less than the fourth flow rate command value Q4, the branch opening degree command for the third valve 21c is released. Thus, the opening of the third valve 21c can be returned to the opening according to the second lift curve L2. For this reason, the opening of the third valve 21c is adjusted to the second opening in accordance with the timing of returning the opening of the first valve 21a and the opening of the second valve 21b from the 100% opening to the opening according to the first lift curve L1. The opening can be returned to the opening according to the lift curve L2. In particular, according to the present embodiment, the return timer 45 cancels the branch opening degree command of the third valve 21c after a predetermined time has elapsed since the flow rate command value became the fourth flow rate command value Q4. Thus, by adjusting the setting of the return timer 45, load fluctuation can be effectively suppressed, and the supply of the main steam S1 can be stabilized.

    According to the embodiment described above, the pressure loss of steam during the rated load operation can be reduced, and the plant efficiency can be improved.

    While some embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents. Naturally, these embodiments can also be partially and appropriately combined within the scope of the present invention.

1: Thermal power plant, 2: Boiler, 5: Steam generator, 7: High pressure turbine, 21: Steam control valve, 21a: First valve, 21b: Second valve, 21c: Third valve, 21d: Fourth valve , 30: steam control valve controller, 31: first opening command section, 32: second opening command section, 33: third opening command section, L1: first lift curve, L2: second lift curve, L3: third lift curve, L4: branch curve, Q1: first flow rate command value, Q2: second flow rate command value, Q3: third flow rate command value, Q4: fourth flow rate command value, S1: main steam

Claims (12)

A steam control valve control device that controls a steam control valve having a leading large opening valve, a leading small opening valve, and a trailing valve based on a flow rate command value corresponding to a turbine load,
A first opening command section for giving an opening command to the preceding large opening valve in accordance with a first opening / closing characteristic;
A second opening / closing characteristic having the same opening as the opening of the first opening / closing characteristic when the flow rate command value is smaller than the first flow rate command value, wherein the flow rate command value is equal to or greater than the first flow rate command value; A second opening command unit that gives an opening command to the preceding small opening valve according to a second opening characteristic having an opening smaller than the opening of the first opening characteristic when
When the flow rate command value is smaller than a second flow rate command value larger than the first flow rate command value, a 0% opening command is given to the subsequent valve, and the flow rate command value is equal to or greater than the second flow rate command value. And a third opening command section that gives an opening command to the subsequent valve according to a third opening / closing characteristic having an opening smaller than the opening of the second opening / closing characteristic ,
At a third flow rate command value larger than the first flow rate command value and smaller than the second flow rate command value, the opening degree of the first opening / closing characteristic is smaller than 100% opening degree,
Said first opening command unit, the flow rate command value, when the pre-SL is a third flow rate command value or more, to provide a 100% opening command to the preceding large opening valve deviates from the first opening-closing characteristic A steam control valve control device. The first opening degree command section is configured such that, in the process in which the flow rate command value that is equal to or more than the third flow rate command value shifts to less than a fourth flow rate command value that is smaller than the third flow rate command value, the flow rate command value The 100% opening command is given to the preceding large opening valve until the fourth flow command value is reached, and when the flow command value becomes smaller than the fourth flow command value, the 100% opening command of the preceding large opening valve is set. The steam control valve control device according to claim 1 , wherein the% opening degree command is canceled. The second opening command section may be configured such that, in the process, while the flow command value is equal to or more than the fourth flow command value and equal to or less than the third flow command value, the opening degree is smaller than the opening degree of the second opening / closing characteristic. 3. The steam control valve control device according to claim 2 , wherein a branch opening command is given to the preceding small opening valve in accordance with the branch opening / closing characteristic having: The second opening command unit, in the process, when the flow command value is less than the fourth flow command value, cancels the branch opening command of the preceding small opening valve, wherein The steam control valve control device according to claim 3 , wherein The second opening command unit, in the process, cancels the branch opening command of the preceding small opening valve after a lapse of a predetermined time after the flow command value becomes the fourth flow command value. The steam control valve control device according to claim 4 , wherein The leading large opening valve includes a first leading large opening valve and a second leading large opening valve,
Said first opening command unit, any one of claims 1 to 5, characterized in that providing the opening command to the first prior large opening valve and the second leading large opening valve in accordance with the first opening-closing characteristic The steam control valve control device according to the paragraph. A steam generator,
A high-pressure turbine that is rotationally driven using steam supplied from the steam generator,
A steam control valve for controlling a flow rate of steam supplied to the high-pressure turbine,
Power plant, characterized in that and a steam control valve control apparatus according to any one of claims 1 to 6 for controlling the steam control valve. A steam control valve control method for controlling a steam control valve having a leading large opening valve, a leading small opening valve and a trailing valve based on a flow rate command value according to a turbine load,
When the load increases,
The leading large opening valve and the leading small opening valve are opened, and the opening of the leading large opening valve is increased in accordance with a first opening / closing characteristic until the flow rate command value becomes the first flow rate command value. Increasing the opening of the preceding small opening valve according to the second opening / closing characteristic so as to be the same as the opening of the leading large opening valve;
When the flow rate command value becomes the first flow rate command value, the opening of the leading small opening valve is made smaller than the opening of the leading large opening valve, and the opening of the leading small opening valve is reduced. Increases the opening degree of the leading large opening valve in accordance with the first opening / closing characteristic while maintaining a relationship smaller than the opening degree of the leading large opening valve, and maintains the leading small opening degree in accordance with the second opening / closing characteristic. A process of increasing the opening of the valve,
When the flow rate command value becomes a second flow rate command value larger than the first flow rate command value, the trailing valve is opened, and the opening of the trailing valve is smaller than the opening of the leading small opening valve. Increasing the opening of the preceding small opening valve in accordance with the second opening / closing characteristic and increasing the opening of the trailing valve in accordance with the third opening / closing characteristic while maintaining a small relationship. Prepare ,
At a third flow rate command value larger than the first flow rate command value and smaller than the second flow rate command value, the opening degree of the first opening / closing characteristic is smaller than 100% opening degree,
During load increase during and load drop, the flow rate command value, when the pre-SL is a third flow command value, 100% that the opening command is given to the preceding large opening valve deviates from the first opening-closing characteristic Characteristic steam control valve control method. At the time of load reduction, the 100% opening command is given to the preceding large opening valve until the flow command value becomes a fourth flow command value smaller than the third flow command value, and the flow command value is changed to the fourth flow command value. 9. The control method according to claim 8 , wherein the 100% opening command of the preceding large opening valve is canceled when the flow rate becomes less than four flow command values. At the time of load drop, while the flow rate command value is equal to or more than the fourth flow rate command value and equal to or less than the third flow rate command value, the leading small opening degree valve is set to have a smaller opening degree than the leading small opening degree valve when the load is increased. 10. The steam control valve control method according to claim 9 , wherein a branch opening command for decreasing the opening while maintaining a small relationship is given. The steam according to claim 10 , wherein the branch opening command of the preceding small opening valve is canceled when the flow command value becomes smaller than the fourth flow command value at the time of load reduction. Control valve control method. 13. The load control device according to claim 11 , wherein the branch opening command of the preceding small opening valve is released after a lapse of a predetermined time from when the flow rate command value becomes less than the fourth flow rate command value. Steam control valve control method.

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