JP2017031859A - Combined cycle power plant and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combined cycle power plant and its control method capable of certainly tying or cutting-off steam by preventing the reliability reduction due to valve means.SOLUTION: A combined cycle power plant comprises: a plurality of steam generators; first passages connected to the plurality of steam generators; a confluent part for joining a plurality of the first passages so as to enable back flow; a steam turbine; cutoff valves respectively provided along the plurality of the first passages; second passages branched from the steam generator side of the cutoff valves and leading to the back wash of the steam turbine; turbine by-pass valves provided along the second passages; a control circuit of the turbine by-pass valves for controlling the steam pressure on the second steam generator side to the steam turbine inlet pressure so as to maintain the inlet pressure at a constant value in a state in which the steam from the first steam generator out of the plurality of steam generators is guided to the steam turbine via the confluent part; and a control circuit of the cutoff valves for opening the cutoff valves with the turbine by-pass valves maintained at a constant value, so as to tie the second steam generator side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a combined cycle power plant that joins steam from a plurality of sets of steam systems and guides them to a steam turbine, and a control method thereof, and more particularly, to a combined cycle power plant that has no valve means in a steam combined portion and a control thereof. Regarding the method.

  In recent years, combined cycle power plants combining gas turbines, exhaust heat recovery boilers, and steam turbines have been widely adopted. In such a combined cycle power plant, a generator is driven by a gas turbine to obtain electric power, and exhaust heat held by the exhaust heat of the gas turbine is recovered as steam in an exhaust heat recovery boiler, and the obtained steam is sent to the steam turbine. Take care and drive the generator to get power again. In addition, it is also possible to use a steam facility that uses steam for industrial use instead of the steam turbine.

  The combined cycle power plant is a facility that effectively converts fossil fuel energy from combustion energy to steam energy in order to achieve high efficiency. It is effective to unitize a combination of exhaust heat recovery boilers, and to make a large-capacity facility (multi-shaft combined cycle power plant) that joins steam from a plurality of units at a joining section and comes to a common steam turbine.

  Patent Documents 1, 2, and 3 show one configuration example of the above-described large-capacity combined cycle power generation facility, and appropriately include a control valve and a check valve on the upstream side or the downstream side of the junction, A turbine bypass system is provided from the upstream side of the junction to the condenser of the steam turbine. Patent Documents 1, 2, and 3 describe examples of a method for controlling steam conditions in a merging section when starting and stopping in a combined cycle power plant having such a configuration.

JP-A-57-179310 JP 2004-27938 A Japanese Patent Laid-Open No. 9-4416

  According to one configuration example of the large-capacity combined cycle power generation facility described above, a control valve and a check valve are appropriately provided on the upstream side or the downstream side of the merging portion, and steam of different conditions from a plurality of units at the time of starting and stopping is provided. Connecting and disconnecting are realized.

  For this reason, the conventional equipment is expensive because it is equipped with valve means such as a control valve and a check valve, and there is a problem of lowering reliability due to failure of the valve means, and further, connection and disconnection of steam under different conditions is realized. The problem is that the configuration of instrumentation and control means is complicated.

  Among these, when viewed from the viewpoint of failure of the valve means, the series of operations related to steam system connection and disconnection in the patent document can be realized by installing a check valve upstream of the junction and eliminating steam backflow. Yes.

  However, a check valve in a severe environment of high temperature and pressure has a cause of malfunction due to corrosion due to steam oxidation or the like, or malfunction of the valve sliding part due to flying objects. For this reason, at present, soundness is confirmed by performing and monitoring a check valve operation test by a plant operator.

  For example, if the check valve on the cut-off shaft side sticks when the steam system is cut off and loses its closing function, the generated steam from the continuous operation shaft side is cut off by the turbine bypass valve control operation of the cut-off shaft by the conventional operation described above. Will be discharged to the condenser through the turbine bypass valve on the side of the engine, resulting in insufficient boiling of steam into the steam turbine and reduced pressure boiling due to a sudden decrease in steam drum pressure on the operation continuation side, leading to a trip event due to fluctuations in the water level. there is a possibility. The same applies to the case where the check valve is fully opened even when it is connected, or when the connection is performed in a stick state with slight opening.

  In view of the above, an object of the present invention is to provide a combined cycle power plant and a control method therefor that prevent a decrease in reliability due to having valve means and enable reliable steam connection or disconnection. And

  From the above, in the present invention, a plurality of steam generators, a first passage connected to the plurality of steam generators, a merging portion that joins the plurality of first passages so as to be able to backflow, a steam turbine, A shut-off valve provided in each of the plurality of first passages, a second passage that branches from the steam generator side of the shut-off valve and reaches the wake of the steam turbine, and a turbine bypass provided in the second passage In a state where the steam from the first steam generator among the plurality of steam generators is led to the steam turbine through the junction, the steam pressure on the second steam generator side is changed to the steam turbine inlet pressure. A control circuit for the turbine bypass valve that maintains a constant value, and a control circuit for a shut-off valve that opens and closes the shut-off valve while the turbine bypass valve is maintained at a constant value. Connecting and disconnecting the steam generator side Ukoto is obtained by a combined cycle power plant according to claim.

  In addition, the present invention provides a plurality of steam generators, a first passage connected to the plurality of steam generators, a merging portion that joins the plurality of first passages so as to be able to reversely flow, a steam turbine, and a plurality of first A shut-off valve provided in each of the first passages, a second passage that branches from the steam generator side of the shut-off valve and reaches the wake of the steam turbine, and a turbine bypass valve provided in the second passage. A control method for a combined cycle power plant, wherein a steam from a first steam generator among a plurality of steam generators is led to a steam turbine through a junction, A control method for a combined cycle power plant characterized in that the shutoff valve is opened and closed to connect and disconnect at the junction with the opening of the turbine bypass valve held constant on the second steam generator side What A.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the reliability by having a valve means can be prevented, and the combined cycle power plant and its control method which make it possible to connect or disconnect steam reliably can be provided.

  More specifically, according to an embodiment of the present invention, a plurality of steam generators, steam turbines, and steam from each steam generator have a shut-off valve, and a check valve that prevents backflow is not installed. Combined cycle power generation comprising a first passage that leads to a confluence section in front of the steam turbine, and a second passage that bypasses the steam turbine from the upstream of the shutoff valve of the first passage through the turbine bypass valve from each steam generator When connecting and disconnecting steam systems in the plant, the steam back flow is suppressed, and sudden changes in the amount of generated power due to sudden changes in the amount of incoming steam and changes in the steam drum level of the exhaust heat recovery boiler due to sudden changes in steam pressure. It is possible to control the instability, implement a control operation that is the same as the conventional one with a check valve installed, avoid problems with the check valve stick, and reduce equipment. . Furthermore, there is an effect that the work burden of the operator such as daily check valve operation test and monitoring is eliminated.

The figure which shows the structure of the multi-shaft combined cycle power plant concerning this invention. The figure which shows the structure of the conventional typical multi-shaft type | mold combined cycle power plant. The control circuit diagram of the turbine bypass valve concerning the embodiment of the present invention. The figure which shows the specific circuit structure of the pressure setting part of FIG. The figure which shows the relationship between the gas turbine load and the turbine bypass valve regulation opening setting value which are set by the regulation opening setting part 103. FIG. The figure which shows the operation | movement outline | summary of the turbine bypass valve and the cutoff valve at the time of splicing operation. The figure which shows the operation | movement outline | summary of the turbine bypass valve and the cutoff valve at the time of disconnection operation. The figure which shows the operation | movement outline | summary of the isolation | separation shaft turbine bypass valve in Example 2. FIG. The figure which shows the structure of the multi-pressure, multi-shaft combined cycle power plant concerning this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIGS. 1 and 3 to 7.

  First, the configuration and control method of a typical conventional multi-shaft combined cycle power plant will be described with reference to FIG. A general multi-shaft combined cycle power plant is composed of one steam turbine, two or more gas turbines, and a steam generator (exhaust heat recovery boiler) associated therewith.

  In FIG. 2, for simplification of description, two gas turbines GT 1 and GT 2 and two accompanying steam generators SG 1 and SG 2 and each steam generator SG are installed for one steam turbine ST. Steam drums D1 and D2, first passages P11 and P12 that guide the steam generated from the steam drums D1 and D2 to the steam turbine ST, and steam generated from the first passages P11 and P12 via the turbine bypass valves VB1 and VB2 It consists of second passages P21 and P22 that bypass the turbine ST and lead to the condenser 8, and branch portions of the first passages P11 and P12 to the second passages P21 and P22 and a joining portion of each steam system before the steam turbine ST. 15 shows a plant configuration in which check valves VC1 and VC2 and shut-off valves VS1 and VS2 are installed.

  According to the configuration shown in the figure, the steam generated in the steam drums D1 and D2 installed in the steam generators SG1 and SG2 on the exhaust side of the gas turbines GT1 and GT2 passes through the first passages P11 and P12 and reverses. After joining the stop valves VC1 and VC2 and the shut-off valves VS1 and VS2, after joining at the steam joining section 15, the steam flows into the steam turbine ST. The inflowing steam is discharged after working in the steam turbine ST, and the discharged steam is condensed in the condenser 8 to become condensate.

  During normal operation, the shut-off valves VS1 and VS2 are both fully open, and the steam generated from the steam drums D1 and D2 of the steam generators SG1 and SG2 joins the steam through the first passages P11 and P12. After merging at the section 15, all are guided to the steam turbine ST. At this time, the turbine bypass valves VB1 and VB2 provided in the second passages P21 and P22 branched from the first passages P11 and P12 and connected to the condenser 8 are fully closed.

  In such a combined cycle power plant in which steam generated from a plurality of independent steam generators SG is joined to one steam turbine, guided to the steam turbine ST, and the steam turbine ST and the generator are driven, When starting / stopping and when the number of operating gas turbines and boilers on the steam generator SG side is increased or decreased for improving the plant operation efficiency, it is necessary to connect / disconnect the steam system at the steam confluence 15. When connecting and disconnecting this steam system, the plant system was prevented from becoming unstable, such as a sudden change in the amount of generated power due to a sudden change in the amount of incoming steam and a change in the steam drum level of the steam generator SG due to a sudden change in steam pressure. Safe and smooth control is very important.

  Here, in the multi-shaft combined cycle power plant shown in FIG. 2, the steam system joining operation when the gas turbine GT2 and the steam turbine ST additionally start the gas turbine GT2 during the normal operation is already performed. GT1 and the steam generator SG1 associated therewith will be described as an operating shaft, and the gas turbine GT2 and the steam generator SG2 associated therewith will be described as a connecting shaft.

  In this operation, first, the gas turbine GT2 serving as a connecting shaft is started. The steam generated from the steam drum D2 of the steam generator SG2 is controlled to a constant pressure by the turbine bypass valve VB2. At this time, the shutoff valve VS2 on the connecting shaft side is in a fully closed state. At this time, the control of the turbine bypass valve VB2 is performed by controlling the steam pressure on the operating shaft side already ventilated in the steam turbine so as to suppress the pressure fluctuation at the time of steam connection and the accompanying steam turbine load and instability of the plant system. (PI) and the following pressure setting value of the steam pressure on the operating shaft side, and the comparison calculation (PI) with the measured value of the pressure detector PS2 provided in the first passage P12 on the connecting shaft side The pressure is controlled to be the set pressure by pressure feedback control using an output signal of calculation (proportional + integral calculation).

  In addition, in order to prevent the steam system fluctuation | variation at the time of joining, the load of each gas turbine GT1, GT2 at the time of steam system connection operation has the same gas turbine exhaust gas temperature on each of the operation shaft and the connection shaft, and each steam generator SG1, It is carried out while maintaining the connected load condition so that the generated steam amount of SG2 is equivalent.

  Therefore, the operation shaft side during normal operation is kept in a standby state in the connected load during this period. The steam pressure on the connecting shaft side becomes the set pressure by the control of the turbine bypass VB2, and the connecting valve start command VS2 on the connecting shaft side that has been fully closed is opened. The turbine bypass valve VB2 continues the pressure control until the shut-off valve VS2 is fully opened, and gradually closes after the shut-off valve VS2 is fully opened. Finally, the connecting operation is completed by fully closing the connecting shaft side turbine bypass valve VB2.

  In this connection operation, for example, the pressure detector PS3 provided on the steam turbine ST inlet side for detecting the steam pressure on the operation shaft side and the measurement by the pressure detector PS2 provided on the first passage P12 on the connection shaft side are performed. If an attempt is made to join the steam while the steam pressure on the connecting shaft side is lower than the operating shaft side steam pressure due to an error, there is a possibility that a steam reverse flow from the operating shaft side to the connecting shaft side occurs. For this reason, check valves VC1 and VC22 are conventionally installed at the branching portion from the first passages P11 and P12 to the second passages P21 and P22 having the turbine bypass valves VB1 and VB2 and the steam confluence portion before the turbine inlet. In the connecting operation, the backflow of steam from the operation shaft side to the connecting shaft side is prevented.

  Next, in the conventional multi-shaft combined cycle power plant shown in FIG. 2, the steam system disconnection operation when the gas turbine GT1, the gas turbine GT2, and the steam turbine ST stop the gas turbine GT2 during normal operation is performed by the gas turbine GT1. The steam generator SG1 associated therewith will be described as an operating shaft, and the gas turbine GT2 and the steam generator SG2 associated therewith will be described as a separate shaft.

  In this case, first, the gas turbine load of the operation shaft and the separation shaft is lowered to the separation load condition determined from the viewpoint of the operation efficiency and the separation operation time, and then the separation operation is performed.

  Specifically, after reaching the separation load, the turbine bypass valve VB2 on the separation shaft side is gradually opened, and the amount of steam generated from the steam generator SG2 flows into the full condenser 8, and then the cutoff is performed. The valve VS2 is closed. At this time, the control of the turbine bypass valve VB2 of the separation shaft is performed by gradually opening the steam detector SG2 to the opening degree that bypasses the entire amount of steam generated from the steam drum D2 of the steam generator SG2, and the pressure detector PS3 installed at the steam turbine inlet. When the pressure measurement value (steam generator SG2 outlet pressure) of the pressure detector PS2 installed in the first passage P12 at the outlet of the steam generator SG2 becomes lower than the pressure measurement value (steam turbine inlet pressure), the separation shaft side Assuming that all the generated steam has been bypassed, set the program pressure setting value so that it is lower than the steam pressure on the operating shaft side or the follow-up pressure setting value lower than the steam pressure on the operating shaft side. Shifts to pressure feedback control based on the output signal of the comparison calculation (PI calculation (proportional + integral calculation)). At the same time, the cutoff valve VS2 of the separating shaft is closed.

  Thus, if the pressure at the outlet of the steam generator SG of the separating shaft becomes lower than the pressure at the inlet of the steam turbine, all the steam generated by the steam generator SG is flowing to the condenser by the turbine bypass. Thus, since the shut-off valve is closed, it can be separated without changing the amount of steam flowing into the steam turbine. Eventually, the shutoff valve on the separation shaft is fully closed, so that the steam system disconnecting operation is completed, and then the gas turbine is stopped on the disconnecting shaft. In addition, since the check valves VC1 and VC2 are installed in each of the first passages P11 and P12, the steam backflow from the operation shaft side to the separation shaft side does not occur during the steam system separation operation.

  FIG. 1 shows a configuration of a multi-shaft combined cycle power plant according to the present invention. As is apparent from the comparison between FIG. 2 of the prior art and FIG. 1 of the present invention, in the present invention, the first branch passages P11 and P12 are introduced to the second passages P21 and P22 and the steam turbine ST. The check valves VC1 and VC2 between the steam merging portions 15 of the respective steam systems are not installed and are excluded.

  A control method of a combined cycle power plant that can be started and stopped even in the configuration of the multi-shaft combined cycle power plant shown in FIG. 1 will be described below.

  Here, for example, the gas turbine GT1 is in operation and the shut-off valve VS1 installed in the first passage P11 is fully opened, and the generated steam from the steam drum D1 of the steam generator SG1 is sent to the steam turbine ST via the first passage P11. In the state where the steam turbine ST is operated, the gas turbine GT2 is started, and the generated steam from the steam drum D2 of the steam generator SG2 is kept with the shut-off valve VS2 installed in the first passage P12 being fully closed. Through the second passage P22 branched from the first passage P12, the steam generated from the steam drum D2 of the steam generator SG2 is completely discharged from the state where the steam turbine ST is bypassed and introduced into the full condenser 8. Regarding the connection control method for the steam system to be introduced into the ST, the gas turbine GT1 already in communication with the steam turbine ST and the steam generation associated therewith. Driving shaft vessel SG1, described as axial narrowing connecting steam generator SG2 associated with the gas turbine GT2 and it.

  In the control method of the present invention, first, in this case, the gas turbine GT2 serving as the connecting shaft is started. The shutoff valve VS2 on the connecting shaft side remains in a fully closed state, and the steam generated from the steam drum D2 of the steam generator SG2 is controlled to a constant pressure by the turbine bypass valve VB2.

  The control of the turbine bypass valve VB2 of the connecting shaft before this connecting operation will be described with reference to FIGS. FIG. 3 is a diagram illustrating a control circuit for the turbine bypass valve according to the first embodiment of the present invention, and FIG. 4 is a diagram illustrating a specific internal circuit configuration of the pressure setting unit in FIG. 3.

  The turbine bypass valve control circuit in FIG. 3 is a circuit diagram for controlling the turbine bypass valve VB2 by detecting the steam pressure from the first passage P12 on the connecting shaft side by the pressure detector PS2. That is, FIG. 3 assumes a case where the gas turbine GT1 and the associated steam generator SG1 communicating with the steam turbine ST are used as the operation shaft, and the gas turbine GT2 and the associated steam generator SG2 are used as the connecting shaft. However, in the opposite case, a circuit diagram for detecting the steam pressure from the first passage P11 on the connecting shaft side by the pressure detector PS1 and controlling the turbine bypass valve VB1 is provided.

  In the control example of the turbine bypass valve VB2, as shown in FIG. 3, the pressure measurement value of the pressure detector PS3 installed at the inlet of the steam turbine ST is introduced into the pressure setting unit 100. The detailed configuration and operation of the pressure setting unit 100 will be described in detail with reference to FIG. 4. In short, a pressure setting value corresponding to the steam pressure on the already operating shaft side is obtained and set as a target value. On the other hand, the steam pressure obtained from the first passage P12 on the connecting shaft side via the pressure detector PS2 is introduced into the turbine bypass valve control circuit as a feedback value with respect to the target value.

  FIG. 4 shows a specific circuit configuration of the pressure setting unit 100 of FIG. 3. In short, the pressure measurement value of the pressure detector PS3 is set to the first value P01 set via the setting device 200, and the pressure detection. A target value given by the pressure setting unit 100 by switching one of the second values P02 obtained by adding the predetermined bias value given by the signal generator 203 to the pressure measurement value of the device PS3 by the adder 202 by the switch 201 It is what. At the beginning of activation, the first value P01 is set as a target value, and then switched to the second value P02.

  The target value (output of the pressure setting unit 100) and the feedback value (output of the pressure detector PS2) are compared by the comparison calculator 101 and the deviation signal is introduced into the feedback control unit 102. An operation amount signal S2 obtained and output by proportional integral control (PI control) in the feedback control unit 102 is given to the turbine bypass valve VB2 as an opening degree command S4 of the turbine bypass valve VB2, and steam is generated on the connecting shaft side. While discharging the total amount of steam generated from the steam drum D2 of the container SG2 to the condenser 8, the pressure of the connecting shaft steam system is controlled to be equal to and constant with the operating shaft side steam pressure. In the period until the pressure of the connecting shaft steam system is equal to and constant with the operating shaft side steam pressure, the switching unit 105 and the valve solution holding unit 104 in the feedback control unit 102 do not function, and feedback control is performed. The output S2 of the part 102 is directly supplied to the turbine bypass valve VB2 as the output S4 of the turbine bypass valve control circuit.

  The above-described operation until the connecting shaft vapor pressure reaches the set pressure is the same as the conventional one, and the present invention is characterized by the connecting operation performed after reaching the set pressure. In the control of the turbine bypass valve VB2 of the connecting shaft during the connecting operation, as shown in FIG. 3, first, the valve opening holding command signal S1 is given to the valve opening holding unit 104, and the output of the pressure feedback control unit 102 is output. By shutting off S2 and holding the current valve opening operation amount signal S2, the opening of the turbine bypass valve VB2 is held (locked) at that position so as not to operate from the current position. In this case, the valve opening degree holding command signal S1 is generated when the connecting shaft steam pressure reaches the set pressure by a circuit (not shown).

  Thereafter, an opening operation command is given to the shutoff valve VS2 on the connecting shaft side, and the shutoff valve VS2 starts to open. At this time, when the steam pressure on the connecting shaft side is higher than the steam pressure on the operating shaft side due to the measurement error of each pressure detector PS2, PS3 or the calculation error of the output value (set value) in the pressure setting unit 100 In the process of opening the shutoff valve VS2 installed in the first passage P12 on the connecting shaft side, the steam on the connecting shaft side flows into the steam turbine ST in a small amount, and between the first passage PS11 to the steam turbine ST on the operating shaft. However, since the opening degree of the turbine bypass valve VB2 on the connecting shaft side is in a fixed state, the amount of increase in the pressure is equal to the pressure measurement error or the calculation error of the pressure setting unit 100. The influence on the steam turbine ST and the steam drum D1 on the operation shaft side can be made extremely small.

  On the other hand, when the steam pressure on the connecting shaft side is lower than the steam pressure on the operating shaft side due to the above-mentioned error, the operation is performed in the process of opening the shut-off valve VS2 installed in the first passage P12 on the connecting shaft side. The steam on the shaft side flows backward to the connecting shaft side, resulting in a drop in steam pressure between the first passage P11 to the steam turbine ST on the operating shaft side, but the opening degree of the turbine bypass valve VB2 on the connecting shaft side is a fixed opening degree. Therefore, as in the case of the above-mentioned pressure increase, the pressure drop amount is equivalent to the pressure measurement error or the calculation error of the pressure setting unit 100, so the influence on the steam turbine ST and the steam drum D1 on the operation shaft side is limited. Can be very few.

  In addition, when there is a concern about the influence due to various circumstances on the plant operation and power transmission system side, it can be easily dealt with by adjusting the opening operation speed of the shutoff valve VS2 of the connecting shaft.

  Subsequently, after the shutoff valve VS2 on the connecting shaft side is fully opened, the set value of the turbine bypass valve VB2 is switched. This operation is performed by setting the output value (first value P01) of the pressure setting unit 100 in FIG. 4 to the set value (second value P02) obtained by adding the bias value to the measured value of the pressure detector PS2 by the adder 202. This is realized by switching with the switch 201. Further, the opening degree output holding of the valve opening degree holding unit 104 in FIG. 3 is released, and the process again proceeds to the control of the pressure feedback control 102, and the turbine bypass valve VB2 is fully closed by the pressure control.

  FIG. 6 shows an outline of the operation of the turbine bypass valve and the shutoff valve during the splicing operation. In FIG. 6, the horizontal axis represents elapsed time, and the vertical axis represents the opening degrees of the connecting shaft turbine bypass valve and the shutoff valve. Moreover, the turbine bypass valve control form of Example 1 by the said description is described in the upper part of the figure as a supplement.

  In the elapsed time of the horizontal axis, t1 is the shut-off valve opening operation start time (connection start time), and therefore the control state before time t1 is the operation period of the connection shaft turbine bypass valve VB2 by the pressure control of the feedback control unit 102. It can be said. As shown in the figure, during this period, the opening degree of the turbine bypass valve VB2 is adjusted appropriately to be an indefinite opening degree.

  In the elapsed time on the horizontal axis, t2 is the time when the shut-off valve is fully opened. Therefore, the control state between time t1 and time t2 is connected, and it can be said that the opening degree holding period of the shaft turbine bypass valve VB2. In this period, the shutoff valve VS2 is released over time while the opening of the turbine bypass valve VB2 is kept constant. As illustrated, during this period, the opening of the turbine bypass valve VB2 is a fixed opening.

  In the elapsed time on the horizontal axis, t3 is the time point when the turbine bypass valve VB2 is fully closed (connection completion time point). Therefore, the control state from time t2 to time t3 is the turbine bypass valve VB2 based on pressure control of the feedback control unit 102. It can be said that the gradual closing period. In this period, the opening degree of the turbine bypass valve VB2 is gradually and constantly closed while the shutoff valve VS2 is fully opened.

  In the present invention, the position of the turbine bypass valve opening, in which the amount of steam generated from the connecting shaft side is completely bypassed from the start of the shutoff valve opening operation on the connecting shaft side to the fully open state in this way, is maintained. (Lock), a check valve between the branching portion branching from each of the first passages P11 and P12 to the second passages P21 and P22 and the steam joining portion 15 of each steam system introduced into the steam turbine ST. Even in a plant configuration in which the system is not installed, the steam pressure when the steam system is connected and the change in steam flow into the steam turbine are not affected by the operation, and the connection between the conventional steam system and a check valve is installed. Operation is possible.

  Next, in the plant configuration of the present invention shown in FIG. 1, the gas turbines GT1 and GT2 are in operation and the shut-off valves VS1 and VS2 installed in the first passages P11 and P12 are fully opened, and the second passages P21 and P21, The turbine bypass valves VB1 and VB2 installed at P22 are fully closed, and the steam generated from the steam drums D1 and D2 of the steam generators SG1 and SG2 is introduced into the steam turbine ST to operate the steam turbine ST. From the state, the generated steam from the steam drum D2 of the steam generator SG2 attached to the gas turbine GT2 is fully closed with the shutoff valve VS2 installed in the first passage P12, and the second passage P12 and the turbine bypass installed in the second passage P12. Regarding the disconnection control method for the steam system to be introduced into the full condenser 8 via the valve VB2, the gas turbine connected to the steam turbine ST after disconnection GT1 and operating shaft steam generator SG1 associated therewith, described as axis detach the steam generator SG2 associated with the gas turbine GT2 and it.

  FIG. 7 is a diagram showing an outline of operations of the turbine bypass valve and the shutoff valve during the separation operation. In FIG. 7, the state before the start of the detachment operation is shown at time t4, and the state at time t4 is the same as the time t3 in FIG. That is, the turbine bypass valve VB2 is fully closed and the cutoff valve VS2 is fully open.

  The fully closed state of the turbine bypass valve VB2 is a set value in which the pressure setter 100 adds a bias value to the measured value of the pressure detector PS3 by the adder 202 in the turbine bypass valve control circuit shown in FIGS. This is realized by giving (second value P02).

  According to FIG. 7, the horizontal axis represents the elapsed time, and the vertical axis represents the opening degrees of the separation shaft turbine bypass valve VB2 and the cutoff valve VS2. Further, in the upper part of FIG. 7, the turbine bypass valve control mode of the first embodiment according to the above description is described as a supplement.

  In the elapsed time of the horizontal axis, t4 is the turbine bypass valve VB2 opening command time point, t5 is the turbine bypass valve VB2 specified opening arrival time point, and the control state from time t4 to time t5 is the specified opening setting unit. This is a gradual opening period (specified opening operation period) of the turbine bypass valve VB2 according to the output value of 103. In this period, the opening degree of the turbine bypass valve VB2 is gradually and constantly opened while the shutoff valve VS2 is fully opened. Note that the time point t5 is also the time point when the turbine bypass valve VB2 reaches the specified opening and the closing operation of the shutoff valve VS2 is started (the separation start time point).

  In the elapsed time of the horizontal axis, t6 is the shut-off valve fully closed time (separation completion time), and the control state from time t5 to time t6 is disconnected and is the opening holding period of the shaft turbine bypass valve VB2. In this period, the shutoff valve VS2 is closed over time while the opening of the turbine bypass valve VB2 is kept constant. As illustrated, during this period, the opening of the turbine bypass valve VB2 is a fixed opening.

  In the elapsed time of the horizontal axis, t6 is the shut-off valve closing time (separation completion time), and the control state after time t6 is the operating period of the separation shaft turbine bypass valve VB2 by pressure control of the feedback control unit 102.

  As is clear from the operation waveforms of the turbine bypass valve and the shut-off valve at the time of the disconnecting operation shown in FIG. 7 in comparison with the operation waveforms of the turbine bypass valve and the shut-off valve at the time of the disconnecting operation of FIG. It is clear that the separation operation was performed by the process processing in the reverse procedure.

  This separation processing is realized by the following processing of the turbine bypass valve control circuit shown in FIGS. First, control of the gradual opening period (specified opening operation period) t4-t5 of the turbine bypass valve VB2 will be described. At this time, the turbine bypass valve VB2 of the separation shaft that has been fully closed during operation is controlled.

  Specifically, before the time t4, the opening input value S2 (command signal in the fully closed state) from the pressure feedback control unit 102 selected by the switch 105 in FIG. Switching to the output value S3 of the setting unit 103 is performed. The output value S3 of the specified opening setting unit 103 is a signal representing a required opening for bypassing the generated steam from the steam drum D2 of the steam generator SG2 of the separation shaft to the full condenser 8 at a constant rate. Slowly open.

  Here, the output value of the specified opening setting unit 103 will be described with reference to FIG. FIG. 5 is a diagram showing the relationship between the gas turbine load set by the specified opening setting unit 103 and the turbine bypass valve specified opening setting value. In FIG. 5, the horizontal axis represents the gas turbine load of the separation shaft, and the vertical axis represents the turbine bypass valve opening. According to this relationship, the larger the decoupling shaft side gas turbine load is, the larger turbine bypass valve opening degree is output. Further, in the characteristics of FIG. 5, a plurality of characteristics are set with the gas turbine load on the operation shaft side as a parameter. According to this relationship, even if the separation shaft side gas turbine load is the same, a smaller turbine bypass valve opening degree is output as the operation shaft side gas turbine load is larger.

  FIG. 5 shows the valve opening determined by the ratio of the gas turbine load between the operation shaft and the separation shaft based on the gas turbine load on the operation shaft and the separation shaft. In addition, here, for simplification of explanation, a conceptual diagram is shown in which the gas turbine load of the operation shaft as a parameter is large, medium, and small.

  In the relational diagram shown in FIG. 5, for example, when the separation operation is started with the gas turbine load (middle) of the operation shaft, the valve opening degree becomes the open direction as the gas turbine load of the separation shaft increases, while the gas turbine load of the separation shaft Is constant, the greater the gas turbine load on the operating shaft, the closer the valve opening becomes.

  Thereby, the gradual opening signal output value S3 from the specified opening setting unit 103 is given to the turbine bypass valve VB2, and the turbine bypass valve VB2 is controlled in the opening direction by the slow operation by the gradual opening signal. Is a specified opening degree derived from the relationship of FIG.

  After the gradual opening signal output value S3 from the specified opening setting unit 103 reaches the required opening (specified opening) calculated by the specified opening setting unit 103, or when the actual valve opening value is introduced After the actual opening reaches the required opening, the valve opening holding command signal S1 is given to the valve opening holding unit 104, the output of the specified opening setting unit 103 is shut off, and the current valve opening operation amount signal is displayed. By holding, the position of the turbine bypass valve VB2 is held (locked) so as not to operate from the current position. This state is the time when the shut-off valve closing operation starts and the time when separation starts at time t5 in FIG.

  Thereafter, in a state where the opening is maintained between time t5 and time t6, a closing operation command is given to the shutoff valve VS2, and the shutoff valve VS2 is started to close. Until the shutoff valve VS2 is fully closed until the shut-off valve VS2 is fully closed, the turbine bypass valve VB2 of the separation shaft is maintained at a predetermined opening degree that can bypass all the generated steam from the steam generator SG2 of the separation shaft, so that it does not operate. Has been.

  For this reason, as explained at the time of the connecting operation described above, the detector measurement error or the calculation error in the specified opening setting unit 103 is separated by the reverse flow from the merging unit 15 to the separated steam system, or the inflow to the merging unit 15 is continued. Although the event may occur, it is very small and the driving effect on the driving axis is very small.

  At time t6, the cutoff valve VS2 on the separation shaft side is fully closed. Thereafter, the turbine bypass valve VB2 sets the output value (first value P01) of the setting device 200 of the pressure setting unit 100 as a set value, cancels the opening output holding of the valve opening holding unit 104, and operates the valve opening operation. The amount is again switched to the signal from the feedback control unit 102 by the switch 105, and the operation proceeds to the gas turbine stop operation.

  In this way, the opening degree of the turbine bypass valve VB2 that bypasses all the generated steam amount from the separation shaft side is maintained at that position from the start of the closing operation VS2 on the separation shaft side t5 until the full closure t6. Thus, a plant in which a check valve is not installed between the branch portion branching from each of the first passages P11 and P12 to the second passages P21 and P22 and the joining portion 15 of each steam system introduced into the steam turbine ST. Even in the configuration, it is possible to eliminate the influence on the operation due to the change of the steam pressure at the time of the steam system disconnection and the steam inflow to the steam turbine, and the steam system can be separated from the conventional system with a check valve installed.

  In the second embodiment, a method for suppressing the backflow from the merging portion 15 to the separation shaft in the separation operation will be described.

  The control state of the separation shaft turbine bypass valve VB2 before time t4 in FIG. 7 of the first embodiment is that the control setting value of the separation shaft turbine bypass valve VB2 is the pressure detection of the output value of the pressure setting unit 100 shown in FIG. The bias value 203 is added to the measured value of the device PS3 by the adder 202. As a result, the turbine bypass valve VB2 is set to a fully closed state by pressure feedback control by setting it higher than the operating shaft side steam pressure, but in this embodiment, in this state, that is, all of the generated steam from the separated shaft side. While being introduced into the steam turbine, the separation shaft VS2 of the separation shaft is closed at the start of the separation operation.

  In this operation, while the shutoff valve VS2 is closed, the steam pressure on the separating shaft side increases, but the turbine bypass valve VB2 has the set pressure (the output value of the pressure setting unit 100 (the first value) Start opening to control to a value of P01)). The separation operation is completed when the cutoff valve VS2 on the separation shaft side is fully closed, and the operation proceeds to a gas turbine stop operation.

  FIG. 8 shows a schematic operation diagram of the separated shaft turbine bypass valve in the second embodiment. In FIG. 8, the horizontal axis and the vertical axis are the same as those in FIG. 7, and the turbine bypass valve control mode is described as a supplement at the top of the figure.

  In this separation operation, the shutoff valve VS2 is closed before the turbine bypass valve VB2 opening operation of the separation shaft in a state where the steam pressures of the respective steam systems of the operation shaft and the separation shaft are balanced. Even in the plant configuration in which the check valve between the branching portion branched from the first passages P11 and P12 to the second passages p21 and P22 and the joining portion 15 of each steam system introduced into the steam turbine ST is not installed, Separation operation is always performed in a state where steam is continuously supplied from the separated steam system to the merging section 15, and the operation can be performed while preventing the steam backflow from the merging section 15 to the shaft side when the steam system is separated.

  In addition, if there are concerns about the impact on operation due to changes in steam pressure or steam flow into the steam turbine due to various circumstances on the plant operation or power transmission system side, the closing operation speed of the shutoff valve VS2 of the separation shaft should be adjusted. Can be easily handled.

  As an embodiment of the present invention, when the gas turbine GT2 is additionally operated while the steam generated from the steam drum D1 of the gas turbine GT1 and the accompanying steam generator SG1 is fully introduced into the steam turbine ST, the gas turbine GT2 is additionally started. However, the same operation can be applied to normal plant startup.

  As an embodiment of the present invention, the steam generated from the steam drums D1 and D2 of the gas turbines GT1 and GT2 and the steam generators SG1 and SG2 accompanying the gas turbines GT1 and GT2 is introduced into the steam turbine ST and is in operation. The steam system disconnecting operation example when stopping the gas turbine GT2 has been described, but the same operation can be applied when stopping a normal plant.

  In Example 1, since the focus was on explaining the basic concept of the present invention, the configuration of the multi-shaft combined cycle power plant was described as a simple single pressure type. On the other hand, the exhaust heat recovery boiler in an actual multi-shaft combined cycle power plant is configured to give a plurality of steam pressures such as high pressure, medium pressure, and low pressure, and the steam turbine is also a high pressure turbine, medium pressure turbine, and low pressure. It may be configured to have a turbine or the like. Furthermore, in starting and stopping in these multi-stage pressure turbines, various methods such as a method performed by switching main steam and a method performed by switching intermediate pressure steam are conceivable.

  FIG. 9 shows an example of the configuration of a multi-stage multi-shaft combined cycle power plant with multi-stage pressure. In the illustrated example, the steam generators (exhaust heat recovery boilers) SG1 and SG2 include high-pressure drums D1H and D2H and low-pressure drums D1L and D2L, and the steam turbine ST includes a high-pressure steam turbine STH and a low-pressure steam turbine STL. As is apparent from these promises of symbol assignment, symbol H is shown for the high pressure portion and symbol L is shown for the low pressure portion. Since the basic configuration is the same as that described with reference to FIG. 1, the detailed description is omitted, and only newly added portions are described. 45 and 46 are low-temperature reheat steam pipes, and each high-pressure turbine bypass pipe P21H. , P22H, high pressure turbine bypass valves VB1H and VB2H are connected to low-temperature reheat steam pipes 45 and 46, respectively.

  What is characteristic here is that the high-pressure and low-pressure merging portions 15H and 15L are not provided with a check valve, and in this respect, the same configuration as that of the present invention in FIG. 1 is adopted. Accordingly, the first and second embodiments can be applied when connecting or disconnecting.

  As described above, in FIG. 1, the configuration of the steam generator (exhaust heat recovery boiler) at a single pressure is taken as an example of the plant configuration, but in the third embodiment of the present invention, the steam generation facility SG <b> 1 as shown in FIG. 9. , Pipes P11H and P12H for leading the steam generated from SG2 to the steam turbine STH, and high-pressure turbine bypass pipes P21H and P22H that branch from the pipe, bypass the steam turbine STH, and discharge to the low-temperature reheat steam pipes 45 and 46, and installed therein The high pressure turbine bypass valves VB1H and VB2H to be controlled are controlled. Also, pipes P11L and P12L that lead the steam generated from the steam generation facilities SG1 and SG2 to the steam turbine STL, turbine bypass systems P21L and P22L that branch from the pipe, bypass the steam turbine STL, and discharge to the condenser 8 and the like. The low pressure turbine bypass valves VB1L and VB2L to be installed are controlled. As described above, the high pressure steam generators D1H and D2H, the low pressure steam generators D1L and D2L, the high pressure steam turbine STH and the low pressure steam turbine STL are provided, and the generated steam from the high pressure steam generators D1H and D2H is supplied to the high pressure turbine. A high pressure turbine bypass system and a low pressure that bypass the high pressure steam turbine STH and lead to high pressure steam turbine exhaust side steam pipes (low temperature reheat steam pipes) 45 and 46 via the bypass pipes P11H and P12H and the high pressure turbine bypass valves VB1H and VB2H. The steam generated from the steam generators D1L and D2L is configured by a low pressure turbine bypass system that bypasses the low pressure steam turbine STL to the condenser 8 via the low pressure turbine bypass pipes P21L and P22L and the low pressure turbine bypass valves VB1L and VB2L. Of reheat type double pressure steam generator (exhaust heat recovery boiler) It can be applied in the configuration of the formation and the reheating type of triple pressure above the steam generator (heat recovery steam).

  In the above description of the present invention, a multi-shaft combined cycle power plant including two gas turbines, two accompanying steam generators (exhaust heat recovery boilers), and a steam turbine for introducing the generated steam is taken as an example. However, a turbine bypass valve provided in a turbine bypass system that discharges generated steam to a condenser (or other steam equipment or outside) by bypassing the steam turbine from a steam piping system connecting a plurality of steam generators and the steam turbine It can be applied to a combined cycle power plant having

  In addition, by bypassing the steam turbine from the steam piping system connecting the steam generator and the steam generator of the conventional thermal power plant or the combined power generation facility of the combustion facility and the steam turbine, the generated steam is condensed into the condenser (or other steam facility or It can be applied to a power plant having a turbine bypass valve provided in a turbine bypass system that discharges to the outside and its control.

  Furthermore, the steam generated by bypassing the steam turbine from the steam piping system connecting the steam generators of the boiling water reactor, the pressurized water reactor and the fast breeder reactor of the nuclear power plant to the steam turbine (or It can be applied to a power plant having a turbine bypass valve provided in a turbine bypass system that discharges to other steam equipment or the outside and control thereof.

  In the embodiment of the present invention, the specified opening operation of the turbine bypass valve at the time of the disconnection operation is set to the specified opening with the output of the specified opening setting unit based on each gas turbine load as the valve operation amount. In cases other than fuel input, exhaust temperature, and gas turbine equipment, the specified opening based on various process values that can estimate and calculate the steam generator operating load, the fuel input, or the generated steam from the operating shaft and the disconnected shaft. It can also be a degree.

  In the embodiment of the present invention, the control set value at the time of pressure feedback control of the turbine bypass valve is set by the setter output based on the steam turbine inlet pressure, but the gas turbine fuel input amount on the operation shaft side, the exhaust temperature, In the case of other than the gas turbine equipment, a set value based on various other process values that can estimate and calculate the steam generator operating load, the fuel input amount, or the steam pressure at the confluence of the turbine inlet may be used.

  Although the present invention has been described with reference to the illustrated embodiment, it is needless to say that the present invention is not limited to the embodiment, and various modifications may be made to the specific structure within the scope of the present invention.

GT1, GT2: Gas turbine SG1, SG2: Steam generator (exhaust heat recovery boiler)
D1, D2: Steam drum ST: Steam turbine 8: Condenser P11, P12: First passage (main steam pipe)
VC1, VC2: check valve VS1, VS2: shutoff valve 15: steam confluence P21, P22: second passage (turbine bypass pipe)
VB1, VB2: Turbine bypass valves PS1, PS2, PS3: Pressure detectors D1H, D2H: High-pressure steam drum D1L, D2L: Low-pressure steam drum STH: High-pressure steam turbine STL: Low-pressure steam turbine P11H, P12H: High-pressure main steam pipe 15H: High-pressure steam junction P21H, P22H: High-pressure turbine bypass pipe VB1H, VB2H: High-pressure turbine bypass valve 45, 46: Low-temperature reheat steam pipe P11L, P12L: High-temperature reheat steam pipe 15L: Low-pressure steam junction P21L, P22L: Low-pressure turbine Bypass pipes VB1L, VB2L: Low-pressure turbine bypass valve 100: Pressure setting unit 101: Comparison calculator 102: Feedback control unit (PI calculator)
103: prescribed opening setting unit 104: valve opening holding unit 105, 201: switching device 200: setting device 202: adder 203: signal generator (bias value)

Claims (12)

  A plurality of steam generators, a first passage connected to the plurality of steam generators, a merging section that joins the plurality of first passages so as to be able to flow backward, a steam turbine, and the plurality of first A shut-off valve provided in each of the passages, a second passage that branches from the steam generator side of the shut-off valve and reaches the wake of the steam turbine, a turbine bypass valve provided in the second passage, In the state where the steam from the first steam generator among the plurality of steam generators is guided to the steam turbine via the junction, the steam pressure on the second steam generator side is set to the steam turbine. A control circuit for the turbine bypass valve that maintains a constant value after controlling to the inlet pressure, and a control circuit for the shut-off valve that opens the shut-off valve in a state where the turbine bypass valve is maintained at a constant value. , Connecting the second steam generator side Combined cycle power plant and performing. The combined cycle power plant according to claim 1,
The combined circuit power plant according to claim 1, wherein the turbine bypass valve control circuit shifts the turbine bypass valve to a fully closed state after the shutoff valve is opened. The combined cycle power plant according to claim 1 or 2,
In the turbine bypass valve control circuit, the steam from the first steam generator and the second steam generator among the plurality of steam generators is led to the steam turbine through the junction. The turbine bypass valve is shifted in the opening direction for the second steam generator side, and when the specified opening is reached, the turbine bypass valve is fixed at the specified opening,
The control circuit for the shutoff valve performs the disconnection on the second steam generator side by closing the shutoff valve during a period in which the turbine bypass valve is fixed at a specified opening. Combined cycle power plant. The combined cycle power plant according to claim 3,
The turbine bypass valve control circuit releases the process of fixing the turbine bypass valve at a specified opening after the shut-off valve is fully closed. The combined cycle power plant according to claim 3 or 4, wherein the steam generator is configured to obtain steam using exhaust heat of a gas turbine.
The specified opening is determined using a gas turbine load of the first steam generator and a gas turbine load of the second steam generator. The combined cycle power plant according to claim 1 or 2,
In the turbine bypass valve control circuit, the steam from the first steam generator and the second steam generator among the plurality of steam generators is led to the steam turbine through the junction. The control setting value of the turbine bypass valve on the second steam generator side is equal to or higher than the operating pressure at the junction before the steam turbine, and the steam from the second steam generator side is kept in a fully closed state by control. The steam is introduced into the turbine,
The combined cycle power plant is characterized in that the control circuit of the shut-off valve performs disconnection on the second steam generator side by closing the shut-off valve in a state where the steam is introduced. A plurality of steam generators, a first passage connected to the plurality of steam generators, a merging section that joins the plurality of first passages so as to be able to flow backward, a steam turbine, and the plurality of first A shut-off valve provided in each of the passages, a second passage that branches from the steam generator side of the shut-off valve and reaches the downstream of the steam turbine, and a turbine bypass valve provided in the second passage. A combined cycle power plant control method comprising:
In the state where the steam from the first steam generator among the plurality of steam generators is led to the steam turbine through the junction, the second steam generator side of the plurality of steam generators The combined cycle power plant control method is characterized in that connection is performed by opening the shut-off valve in a state in which the opening degree of the turbine bypass valve is kept constant and merging steam in the merging portion. . A method for controlling a combined cycle power plant according to claim 7,
The combined cycle power plant control method, wherein the turbine bypass valve is fully closed after the shutoff valve is opened. A method for controlling a combined cycle power plant according to claim 7 or claim 8, comprising:
In the state where the steam from the first steam generator and the second steam generator among the plurality of steam generators is led to the steam turbine through the junction, the second steam generator side The turbine bypass valve is shifted in the opening direction, and when the specified opening is reached, the turbine bypass valve is fixed at the specified opening, and the shut-off valve is closed during the fixed period to perform separation. A control method for a combined cycle power plant. The combined cycle power plant control method according to claim 9, wherein the steam generator is configured to obtain steam using exhaust heat of a gas turbine,
The control method for a combined cycle power plant, wherein the specified opening is determined using a gas turbine load of the first steam generator and a gas turbine load of the second steam generator. 9. The combined cycle power plant control method according to claim 7, wherein the steam generator is configured to obtain steam by using exhaust heat of a gas turbine,
The control method for a combined cycle power plant, wherein the specified opening is determined using a gas turbine load of the first steam generator and a gas turbine load of the second steam generator. A method for controlling a combined cycle power plant according to claim 7 or claim 8, comprising:
In the state where the steam from the first steam generator and the second steam generator among the plurality of steam generators is led to the steam turbine through the junction, the second steam generator side The control setting value of the turbine bypass valve is set to be equal to or higher than the operating pressure at the merging portion before the steam turbine, and the steam is introduced into the steam turbine from the second steam generator side while being fully closed by the control, A control method for a combined cycle power plant, characterized in that the second steam generator side is disconnected by closing the shut-off valve in a state where steam is introduced.

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