JP2012167571A - Uniaxial combined cycle power generation plant, and method of operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue operation by ensuring a necessary cooling steam flow rate of a low-pressure steam turbine in extremely-low fuel operation of a gas turbine in a uniaxial combined cycle power generation plant.SOLUTION: A gas turbine 1, a high-pressure steam turbine 3a, a low-pressure steam turbine 3c and an electric power generator 4 are coaxially connected: high-pressure steam and low-pressure steam are generated in an exhaust heat recovery boiler 7 by using exhaust gas of a combustion gas of the gas turbine 1 as a heat source; the high-pressure steam turbine 3a is made to work by supplying the high-pressure steam through a high-pressure regulator valve 17; and the low-pressure steam turbine 3c is made to work by supplying the low-pressure steam through a low-pressure regulator valve 22. In extremely-low fuel operation, control for fully closing the high-pressure regulator valve 17 is performed, and a pressure setting value of the low-pressure regulator valve 22 is controlled to be lowered.

Description

  The present invention relates to a single-shaft combined cycle power plant in which a gas turbine, a steam turbine, and a generator are connected to a single shaft, and an operation method thereof.

  In a single-shaft combined cycle power plant, the low pressure from the low-pressure steam system to the low-pressure section of the steam turbine during ultra-low fuel operation of the gas turbine, including full-speed no-load (FSNL) operation after the generator load is interrupted When the amount of steam is insufficient, cooling steam is supplied to the steam turbine low-pressure section from a separate steam source in the cooling steam system.

  By the way, the steam generated from the two-pressure exhaust heat recovery boiler is composed of two pressures of high pressure steam generated from the high pressure drum and low pressure steam generated from the low pressure drum. Among these, the low pressure steam generated from the low pressure drum is supplied to the low pressure steam turbine via the low pressure control valve. On the other hand, the high-pressure steam generated from the high-pressure drum performs work in the high-pressure steam turbine through the high-pressure control valve, and then merges with the low-pressure steam from the low-pressure control valve and is supplied to the low-pressure steam turbine. These high-pressure steam and low-pressure steam are, of course, for generating power by driving the steam turbine, but at the same time, they are ventilated in the low-pressure steam turbine, so that the windage loss of the low-pressure steam turbine (in the steam turbine casing) It also serves as cooling steam for the low-pressure steam turbine to prevent heating due to power loss due to air stirring.

  As a supplement, since the amount of high-pressure steam and low-pressure steam generated at the initial start-up of the single-shaft combined cycle power plant is not sufficient, the start-up boiler is started and started up before starting the plant. Steam is generated, and this auxiliary steam is used for cooling steam of a low-pressure steam turbine.

  That is, an operation is performed in which the auxiliary steam at the initial startup of the plant is supplied to the low-pressure steam turbine in parallel with the high-pressure steam or the low-pressure steam. Furthermore, as the start-up process of the plant progresses, the amount of high-pressure steam and low-pressure steam generated increases, and these are sufficient as cooling steam for the low-pressure steam turbine. The supply of auxiliary steam is shut off, and only high-pressure steam and low-pressure steam are supplied to the low-pressure steam turbine. In this way, the cooling steam is supplied to the low-pressure steam turbine of the single-shaft combined cycle power plant at the time of startup, and normal operation is performed.

  Now, urgently opening the breaker of the generator due to an electrical accident or the like is called load breaking. After the occurrence of such a load interruption of the generator, the gas turbine is set to a no-load rated speed operation, and after recovery from an electrical accident, an operation for quickly increasing the reload is performed. In the process of shifting from normal operation to no-load rated speed operation, the amount of fuel supplied to the gas turbine decreases rapidly because of no-load operation. In the steam turbine, the high-pressure regulator is fully closed and the low-pressure regulator is overspeed. To prevent this, the valve is opened once in order to ensure the cooling steam of the low-pressure steam turbine after being fully closed.

  By the way, the reason for closing the high pressure regulator in the no-load rated speed operation is that the torque generated by the gas turbine is relatively increased by reducing the generated torque of the steam turbine by closing the high pressure regulator. This is because the combustion state can be further stabilized by increasing the fuel flow rate.

Japanese Patent Laid-Open No. 11-117715

However, in the no-load rated speed operation, however, the low-pressure steam turbine has insufficient cooling steam for the following reasons. That is,
i) Since the high-pressure control valve is closed, there is no supply of high-pressure steam to the high-pressure steam turbine, and only low-pressure steam is supplied to the low-pressure steam turbine. In this case, the high-pressure steam generated from the high-pressure drum is sent to the condenser via the bypass valve.

  ii) Since the gas turbine has a small amount of fuel, the amount of heat of the exhaust gas from the gas turbine is low, and therefore the amount of low-pressure steam generated from the exhaust heat recovery boiler is also small.

  iii) Since the load interruption occurs due to a sudden accident, it is impossible to start up the operation of the start-up boiler in advance and secure auxiliary steam, unlike during the start-up.

  Therefore, if the cooling steam of the low-pressure steam turbine is insufficient during the no-load rated speed operation as described above, the exhaust temperature of the low-pressure steam turbine rises due to the windage loss of the low-pressure steam turbine, and the no-load rated speed operation can be continued. As a result, the single-shaft combined cycle power plant must be stopped.

  The present invention relates to a single-shaft combined cycle power plant capable of ensuring a necessary cooling steam flow rate of a low-pressure steam turbine during a very low fuel operation of a gas turbine including a no-load rated speed operation and an operation method thereof. The purpose is to provide.

  In order to achieve the above object, a single-shaft combined cycle power plant according to the present invention is coaxially connected to a gas turbine and connected with high pressure steam from a high pressure drum of an exhaust heat recovery boiler via a high pressure control valve. The high-pressure steam turbine driven and the low-pressure steam from the low-pressure drum that generates low-pressure steam having a pressure lower than that of the high-pressure drum is supplied via a low-pressure control valve. A low-pressure turbine steam supply system that supplies steam that is combined with the high-pressure steam that has been combined as low-pressure turbine steam, is coaxially disposed and coupled to the gas turbine and the high-pressure steam turbine, and is driven by the low-pressure turbine steam Before including no-load rated speed operation after load interruption of low-pressure steam turbine and generator connected coaxially with the gas turbine At very low fuel operation of the gas turbine, the high pressure control valve performs control fully closed, characterized in that it comprises a control means for controlling to reduce the pressure setting value of the low-pressure control valve.

  The single-shaft combined cycle power plant according to the present invention is connected to a gas turbine in a coaxial manner, and is driven by high pressure steam supplied from a high pressure drum of an exhaust heat recovery boiler via a high pressure control valve. A low-pressure steam from a low-pressure drum that generates low-pressure steam having a pressure lower than that of the high-pressure drum, and the low-pressure steam and the high-pressure steam that has worked in the high-pressure steam turbine; A low-pressure turbine steam supply system that supplies steam that has been combined as low-pressure turbine steam, a low-pressure steam turbine that is coaxially arranged and coupled to the gas turbine and the high-pressure steam turbine, and is driven by the low-pressure turbine steam, A high-pressure bypass system that bypasses high-pressure steam and is equipped with a high-pressure turbine bypass valve, and is arranged coaxially with the gas turbine And performing control to fully close the high-pressure control valve during extremely low fuel operation of the gas turbine including no-load rated speed operation after load disconnection of the generator coupled to each other, and pressure setting value of the high-pressure turbine bypass valve And a control means for controlling to raise.

  Furthermore, the single-shaft combined cycle power plant according to the present invention is arranged to be coaxially connected to the gas turbine, and is driven by being supplied with high-pressure steam from a high-pressure drum of an exhaust heat recovery boiler via a high-pressure control valve. A steam turbine, a low-pressure steam turbine that is coaxially disposed and coupled to the gas turbine and the high-pressure steam turbine, and is driven by low-pressure steam; a high-pressure bypass that bypasses the high-pressure steam and is provided with a high-pressure turbine bypass valve High pressure reheat steam is generated by combining the medium pressure steam from the system and the intermediate pressure drum that generates intermediate pressure steam at a pressure lower than the high pressure steam and higher than the low pressure steam with the exhaust steam from the high pressure steam turbine. A low-temperature reheat system for supplying to the reheater, and the high-temperature steam from the reheater, arranged coaxially with the high-pressure steam turbine and the low-pressure steam turbine. An intermediate pressure steam turbine that is driven by supplying hot steam via an intermediate pressure control valve, and the high-temperature reheat steam that has been decompressed by working in the intermediate pressure steam turbine and the low-pressure steam are joined together A low-pressure turbine steam supply system that drives the low-pressure steam turbine, an intermediate-pressure bypass system that bypasses the intermediate-pressure steam and is provided with an intermediate-pressure turbine bypass valve, and is coaxially disposed and coupled. At the time of extremely low fuel operation of the gas turbine including no-load rated speed operation after load interruption of the generator, control is performed to fully close the high-pressure control valve and the intermediate-pressure control valve, and the intermediate-pressure turbine bypass valve And a control means for controlling the pressure set value to increase.

  A method for operating a single-shaft combined cycle power plant according to the present invention includes a gas turbine, a high-pressure steam turbine, a low-pressure steam turbine, and a generator arranged coaxially and coupled to each other, sending combustion gas to the gas turbine, and driving the gas turbine. The exhaust gas of the combustion gas is used as a heat source to generate high-pressure steam in the exhaust heat recovery boiler, and low-pressure steam having a pressure lower than that of the high-pressure steam is generated, and the high-pressure steam is supplied via a high-pressure control valve. In a method for operating a single-shaft combined cycle power plant that performs work in a turbine and supplies the low-pressure steam through a low-pressure control valve to perform work in the low-pressure steam turbine, the no-load rated speed after the load of the generator is interrupted A fully-closed control step for performing control to fully close the high-pressure control valve during extremely low fuel operation of the gas turbine including operation, and pressure of the low-pressure control valve And having a pressure setpoint control step of controlling so as to lower the value, the.

  The operation method of the single-shaft combined cycle power plant according to the present invention includes a gas turbine, a high-pressure steam turbine, a low-pressure steam turbine, and a generator that are coaxially arranged and coupled, and a combustion gas is sent to the gas turbine for driving. , Generating high-pressure steam in the exhaust heat recovery boiler using the exhaust gas of the combustion gas as a heat source, generating low-pressure steam having a lower pressure than the high-pressure steam, supplying the high-pressure steam via a high-pressure control valve, and In a method for operating a single shaft combined cycle power plant that performs work in a high-pressure steam turbine and supplies the low-pressure steam via a low-pressure control valve to perform work in the low-pressure steam turbine, no load is applied after the generator is unloaded. A fully-closed control step for performing control to fully close the high-pressure control valve during ultra-low fuel operation of the gas turbine including rated speed operation; and A pressure setpoint control step of controlling so as to increase the pressure setting of the high pressure turbine bypass valve interposed in the high pressure bypass line to bypass, and having a.

  Furthermore, the operation method of the single shaft combined cycle power plant according to the present invention includes a gas turbine, a high-pressure steam turbine, an intermediate-pressure steam turbine, a low-pressure steam turbine, and a generator arranged coaxially and coupled to each other, and combustion gas is connected to the gas turbine. The high-pressure steam is generated in the exhaust heat recovery boiler using the exhaust gas of the combustion gas as a heat source, and the medium-pressure steam having a pressure lower than the high-pressure steam and the low-pressure steam having a pressure lower than the medium-pressure steam are generated. The intermediate pressure steam is combined with the exhaust steam from the high pressure steam turbine, supplied to a reheater that generates high-temperature reheat steam, and is passed through the intermediate pressure control valve in the intermediate pressure steam turbine. A method for operating a single-shaft combined cycle power plant that combines the high-pressure reheat steam that has been decompressed by work and the low-pressure steam to perform work in the low-pressure steam turbine. A fully-closed control step for performing control to fully close the high-pressure control valve and the intermediate pressure control valve during extremely low fuel operation of the gas turbine including no-load rated speed operation after load interruption of the generator; A pressure set value control step for controlling so as to increase the pressure set value of the intermediate pressure turbine bypass valve interposed in the intermediate pressure bypass system for bypassing the intermediate pressure steam.

  According to the present invention, since it is possible to ensure the necessary cooling steam flow rate of the low-pressure steam turbine at the time of extremely low fuel operation of the gas turbine including no-load rated speed operation, it becomes possible to continue a suitable operation. .

1 is a system diagram showing a first embodiment of a single-shaft combined cycle power plant according to the present invention. It is a block diagram which shows the control apparatus of the low pressure regulating valve in 1st Embodiment. It is a figure which shows an example of the function set to the function generator of 1st Embodiment. It is a control block diagram which shows 2nd Embodiment of the single shaft type combined cycle power plant which concerns on this invention. It is a distribution diagram showing a 3rd embodiment of the single axis type combined cycle power plant concerning the present invention. It is a block diagram which shows the control apparatus of the intermediate pressure turbine bypass valve in 3rd Embodiment. It is a systematic diagram which shows 4th Embodiment of the single shaft type combined cycle power plant which concerns on this invention.

  Below, each embodiment of the uniaxial combined cycle power plant concerning the present invention is described with reference to drawings.

(First embodiment)
(Power plant configuration)
FIG. 1 is a system diagram showing a first embodiment of a single-shaft combined cycle power plant according to the present invention.

  As shown in FIG. 1, in the single-shaft combined cycle plant of the present embodiment, the gas turbine 1, the compressor 2, the high-pressure steam turbine 3 a, the low-pressure steam turbine 3 c, and the generator 4 constitute a prime mover unit 100, respectively. The rotating shafts are arranged coaxially and coupled. The gas turbine 1 is supplied with the combustion gas burned in the combustor 5 and is driven by the combustion gas to discharge the exhaust gas. The compressor 2 sucks the atmosphere through the inlet guide vanes 6 to increase the pressure, and supplies the high-pressure air to the combustor 5 for generating combustion gas. The high-pressure steam turbine 3a is supplied with high-pressure steam from a high-pressure main steam pipe 16, while the low-pressure steam turbine 3c is supplied with low-pressure steam from a low-pressure main steam pipe 21 serving as a low-pressure turbine steam supply system. The low-pressure steam turbine 3c drives the generator 4 together with the gas turbine 1 and the high-pressure steam turbine 3a to generate electric power. The rotational speed of the output shaft of the generator 4 is detected by a rotational speed detector 38.

  An exhaust gas side inlet end of the exhaust heat recovery boiler 7 is connected to an outlet end of the gas turbine 1, and the exhaust heat recovery boiler 7 is supplied with exhaust gas from the gas turbine 1 to generate steam. Specifically, the exhaust heat recovery boiler 7 includes a high pressure superheater 10 connected to a high pressure drum 13 that generates high pressure steam, and a low pressure superheater 12 connected to a low pressure drum 15 that generates low pressure steam. The steam generated therefrom is supplied to the high-pressure steam turbine 3a and the low-pressure steam turbine 3c, respectively. In the following description, the high-pressure steam turbine 3a and the low-pressure steam turbine 3c are collectively referred to as the steam turbine 3. The low pressure steam pressure generated in the low pressure drum 15 is detected by the detector 39.

  The high-pressure main steam pipe 16 has a detector 57 and a high-pressure control valve 17 that detect high-pressure steam pressure, the low-pressure main steam pipe 21 has a low-pressure steam isolation valve 35, a detector 56 that detects low-pressure steam pressure, and a low-pressure steam flow rate. This is a pipeline structure provided with a detector 40 for detecting the pressure and the low-pressure adjusting valve 22. In the high-pressure main steam pipe 16, a high-pressure turbine bypass system 81 is branched upstream of the detector 57, and the high-pressure turbine bypass valve 50 is interposed in the high-pressure turbine bypass system 81. Similarly, in the low-pressure main steam pipe 21, a low-pressure turbine bypass system 83 is branched on the upstream side of the detector 56, and a low-pressure turbine bypass valve 52 is interposed in the low-pressure turbine bypass system 83. These high-pressure turbine bypass system 81 and low-pressure turbine bypass system 83 are each connected to the condenser 30.

  The outlet end of the low-pressure steam turbine 3 c is connected to the exhaust heat recovery boiler 7 via the condenser 30 and the feed water pump 28. The low pressure turbine exhaust pressure of the low pressure steam turbine 3 c is detected by the detector 55. Circulating water is supplied to the condenser 30 by driving the circulating water pump 29. The circulating water uses high-pressure steam and low-pressure steam supplied from the high-pressure turbine bypass system 81 and the low-pressure turbine bypass system 83 as condensate, respectively.

  The startup boiler 27 is connected to the auxiliary steam supply pipe 24, one end of the auxiliary steam system 60 is connected to the auxiliary steam supply pipe 24, and the other end is connected to the low-pressure main steam pipe 21. The auxiliary steam system 60 is provided with a control valve 34 and a detector 41 for detecting the auxiliary steam flow rate.

  The control device 70 receives detection signals of a detector 56 that detects low-pressure steam pressure, a detector 40 that detects low-pressure steam flow, and a detector 55 that detects low-pressure turbine exhaust pressure. From 70, opening control signals of the high pressure adjusting valve 17 and the low pressure adjusting valve 22 are output.

(Operation of power plant)
Next, the operation of the uniaxial combined cycle power plant of this embodiment will be described.

  Before startup, the condenser 30 is evacuated by a vacuum pump (not shown), and when the specified vacuum degree is reached, the motor unit 100 is driven to rotate by a starting motor (not shown). The compressor 2 enters the parallel operation.

  Before starting the plant, the start-up boiler 27 is started and started to generate auxiliary steam, and this auxiliary steam is supplied to the auxiliary steam system 60 through the auxiliary steam supply pipe 24, and the flow rate is controlled by the control valve 34. Is adjusted and supplied to the low-pressure main steam pipe 21.

  That is, the startup boiler 27 is installed separately from the exhaust heat recovery boiler 7 for the purpose of supplying auxiliary steam during startup when no steam is generated. The auxiliary steam generated in the start-up boiler 27 is supplied to the low-pressure main steam pipe 21 via the auxiliary steam supply pipe 24 and the control valve 34 interposed in the auxiliary steam system 60 as described above. To be supplied to the steam turbine 3. Thus, at the initial stage of startup, the amount of high-pressure steam and low-pressure steam generated from the exhaust heat recovery boiler 7 is not sufficient, so auxiliary steam from the startup boiler 27 is used as low-pressure turbine cooling steam.

  Furthermore, since the generation amount of high-pressure steam and low-pressure steam increases as the start-up process proceeds, these are sufficient as low-pressure steam turbine cooling steam. Therefore, the start-up boiler 27 is stopped for economical operation, and the auxiliary steam Supply is interrupted and only high-pressure steam and low-pressure steam are supplied to the low-pressure steam turbine 3c.

  The compressor 2 sucks the atmosphere through the inlet guide vanes 6 to increase the pressure, and supplies the high-pressure air to the combustor 5 for generating combustion gas. Fuel is added to the combustor 5 together with high-pressure air, and high-temperature combustion gas is generated. This high-temperature combustion gas is supplied to the gas turbine 1 and performs expansion work in the gas turbine 1.

  Exhaust gas discharged from the gas turbine 1 is introduced into the exhaust heat recovery boiler 7 as a heat source for generating steam, and feed water or steam that circulates through the high-pressure superheater 10, the low-pressure superheater 12, an evaporator of each pressure (not shown), and the like. After exchanging heat with it, it is dissipated into the atmosphere through a chimney.

  The high-pressure steam generated in the high-pressure drum 13 is superheated by the high-pressure superheater 10, and after working in the high-pressure steam turbine 3 a from the high-pressure main steam pipe 16 through the high-pressure control valve 17, It merges with the low pressure steam and is introduced into the low pressure steam turbine 3c. In the present embodiment, the low pressure steam merges in the middle stage of the high pressure steam turbine 3a (in the vicinity of the exhaust part).

  On the other hand, the low-pressure steam generated in the low-pressure drum 15 is superheated by the low-pressure superheater 12, and the low-pressure steam isolation valve 35 is opened when the temperature condition and pressure condition become appropriate. By being supplied to the low-pressure steam turbine 3c together with the high-pressure steam that is guided to the control valve 22 and worked as described above, the generator 4 is driven together with the gas turbine 1 and the high-pressure steam turbine 3a to generate electric power.

  By the way, as described above, after the load interruption of the generator 4 is generated, the gas turbine 1 is set to the no-load rated speed operation, and after the electric system accident is restored, the operation for quickly increasing the reload is performed. In the process of shifting from normal operation to no-load rated speed operation, the amount of fuel supplied to the gas turbine 1 rapidly decreases because of no-load operation. In the steam turbine 3, the high-pressure control valve 17 is fully closed and the low-pressure control valve is closed. In order to prevent overspeed, the valve 22 is once fully closed and then opened to secure low-pressure turbine cooling steam.

  Therefore, when the load is interrupted, the high pressure control valve 17 is closed. Therefore, the high pressure steam generated in the high pressure drum 13 is released to the condenser 30 by opening the high pressure turbine bypass valve 50, and the high pressure steam pressure is increased. Is preventing. Similarly, since the low-pressure adjusting valve 22 is closed, the low-pressure steam generated in the low-pressure drum 15 is released to the condenser 30 by opening the low-pressure turbine bypass valve 52 to prevent an increase in the low-pressure steam pressure. Yes.

  Thus, the condenser 30 is supplied with the high-pressure steam and the low-pressure steam, and the steam is condensed by the circulating water supplied from the circulating water pump 29, and the condensed water is discharged by the water supply pump 28 from the exhaust heat recovery boiler. 7 is supplied.

(Configuration of control device)
Next, the control of the low pressure regulating valve 22 in this embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing the control device 70 of the low pressure regulating valve 22 of FIG.

  In FIG. 2, a steam enthalpy necessary for cooling the low-pressure steam turbine 3c is set in the setting device 101. The function generator 102 uses a steam enthalpy signal necessary for cooling the low-pressure steam turbine 3c from the setting device 101 and a low-pressure turbine exhaust pressure signal a detected by the detector 55, for example, by linear interpolation. A low-pressure turbine cooling steam flow signal b is obtained. The comparator 103 compares the low-pressure turbine cooling steam flow signal b with the low-pressure adjusting valve passage steam flow signal c detected by the detector 40.

  In addition to the output signal of the comparator 103, the AND circuit 104 includes a low pressure regulating valve loading permission command signal d (valid opening permission command for the low pressure regulating valve 22) generally calculated by other logic, and a NOT circuit 105. And a high-pressure adjusting valve loading signal e (an index indicating that the high-pressure adjusting valve 17 is opened) is input.

  In the setting device 107, a rate of change (negative value) when the pressure set value j of the low-pressure adjusting valve 22 is decreased is set in advance. In the setting device 108, a rate of change (positive value) when the pressure set value j of the low pressure adjusting valve 22 is increased is set in advance, and is output as a negative rate of change g. A zero value is set in the setting device 109 in advance. The switch 110 outputs a negative change rate g from the setter 108 when the high-pressure adjusting valve loading signal e is on, and a zero signal from the setter 109 when it is off.

  The switch 106 outputs the negative change rate f input from the setting unit 107 when the output of the AND circuit 104 is on, and outputs the negative change rate g or zero input from the switch 110 when the output is off. Output. The adder 111 adds the value of the signal i from the switch 106 to the value of the output signal of the change rate limiter 114.

  The upper limit limiter 112 is a low pressure determined by the maximum working pressure of the steam pipe from the low pressure drum 15 to the low pressure regulating valve 22, the set value of the safety valve installed on the steam pipe, or the alarm set value for the steam pipe pressure. An upper limit limit value for the pressure setting value j of the adjusting valve 22 is set in advance, and the value of the signal from the adder 111 is compared with the pressure setting value j.

  The lower limit limiter 113 is preset with a lower limit limit value for the pressure setting value j of the low pressure adjusting valve 22 determined in operation or by mechanical characteristics / restrictions of the low pressure drum 15. And the pressure set value j are compared.

  In the change rate limiter 114, mechanical restrictions (change rate) such as the influence on the water level due to the pressure change of the low pressure drum 15 with respect to the change rate of the pressure set value j of the low pressure adjusting valve 22 are set in advance. The rate of change is limited for the signal from the lower limit limiter 113.

  The subtractor 115 subtracts the pressure set value j from the change rate limiter 114 and the low-pressure steam pressure signal k detected by the detector 56. The PID computing unit 116 outputs the opening degree command value m to the low pressure regulating valve 22 so that the deviation signal l obtained from the subtractor 115 becomes zero.

(Operation of control device)
As shown in FIG. 2, a steam enthalpy necessary for cooling the low-pressure steam turbine 3 c is set in the setting device 101. This steam enthalpy signal and the low-pressure turbine exhaust pressure signal a detected by the detector 55 are set. Is input to the function generator 102, and the function generator 102 obtains a low-pressure turbine cooling steam flow signal b necessary for the current operation.

  Specifically, an example of a function set in the function generator 102 is shown in FIG. The horizontal axis in FIG. 3 indicates the low-pressure turbine cooling steam enthalpy necessary for cooling the low-pressure steam turbine 3c, and the vertical axis indicates the low-pressure turbine cooling steam required flow rate. As shown in FIG. 3, the required low-pressure turbine cooling steam curve varies depending on the low-pressure turbine exhaust pressure condition, and the function generator 102 cools the low-pressure steam turbine 3c from the setting device 101 as shown in FIG. The necessary low-pressure turbine cooling steam flow signal b is obtained by linear interpolation or the like from the steam enthalpy signal and the low-pressure turbine exhaust pressure signal a.

  The low-pressure steam flow rate passing through the low-pressure control valve 22 is detected by the detector 40, and this low-pressure steam flow rate is input to the comparator 103 as a low-pressure control valve passing steam flow signal c. The comparator 103 compares the low-pressure turbine cooling steam flow signal b with the low-pressure adjusting valve passing steam flow signal c, and the value of the low-pressure adjusting valve passing steam flow signal c is smaller than the value of the low-pressure turbine cooling steam flow signal b. In this case, the output signal is turned on and output to the AND circuit 104.

  In addition to the output signal of the comparator 103, the AND circuit 104 is supplied with a low pressure regulating valve loading permission command signal d (valid opening permission command for the low pressure regulating valve 22) that is generally calculated by other logic. At the same time, a high-pressure adjusting valve loading signal e (an index indicating that the high-pressure adjusting valve 17 is open) is input via the NOT circuit 105. The AND circuit 104 performs an AND process on the output signal of the comparator 103, the low pressure regulating valve loading permission command signal d, and the output signal of the NOT circuit 105, and outputs the output to the switch 106.

  The setter 107 is set in advance with a rate of change (negative value) when the pressure set value j of the low pressure adjusting valve 22 is lowered, and the output is output to the switch 106 as a negative rate of change f.

  On the other hand, the setter 108 is set in advance with a rate of change (positive value) when the pressure set value j of the low pressure adjusting valve 22 is increased, and is output to the switch 110 as a negative rate of change g. . A zero value is set in advance in the setting device 109 and is output to the switching device 110. The switch 110 outputs a negative change rate g from the setter 108 to the switch 106 when the high-pressure adjusting valve loading signal e is on, and a zero signal from the setter 109 when it is off.

  The switch 106 outputs the negative change rate f from the setting unit 107 when the output of the AND circuit 104 is on, and adds the negative change rate g or zero from the switch 110 when the output is off. To 111. The adder 111 adds the value of the signal i from the switch 106 to the value of the output signal of the change rate limiter 114 and outputs the value to the upper limit limiter 112.

  The upper limiter 112 is determined by the maximum working pressure of the steam pipe from the low pressure drum 15 to the low pressure regulating valve 22, the set value of the safety valve installed on the steam pipe, or the alarm set value for the steam pipe pressure. The upper limit value for the pressure setting value j of the low pressure adjusting valve 22 is set in advance, the value of the signal from the adder 111 is compared with the pressure setting value j, and the smaller value is sent to the lower limit limiter 113. Output. In this lower limit limiter 113, a lower limit limit value for the pressure set value j of the low pressure adjusting valve 22 determined in operation or by mechanical characteristics / restrictions of the low pressure drum 15 is set in advance. Is compared with the pressure set value j, and the larger value is output to the change rate limiter 114. This rate-of-change limiter 114 is preset with mechanical restrictions (rate of change) such as the influence of the pressure change of the low-pressure drum 15 on the water level with respect to the rate of change of the pressure setting value j of the low-pressure adjusting valve 22. Then, the rate of change is limited with respect to the signal from the lower limit limiter 113, and the pressure set value j of the low pressure adjusting valve 22 is obtained.

  Next, the low pressure steam pressure on the inlet side of the low pressure control valve 22 is detected by the detector 56 and input to the subtractor 115 as the low pressure steam pressure signal k. The subtractor 115 performs subtraction between the pressure set value j output from the change rate limiter 114 and the value of the low-pressure steam pressure signal k, and outputs a deviation signal l to the PID calculator 116. The PID calculator 116 outputs the opening degree command value m to the low pressure adjusting valve 22 so that the deviation signal l becomes zero.

  Therefore, in this control device 70, the low pressure regulating valve 22 after the occurrence of load interruption may be opened, and sufficient cooling steam is supplied to the low pressure steam turbine 3c via the high pressure regulating valve 17 and the high pressure steam turbine 3a. If the low-pressure steam flow rate passing through the low-pressure control valve 22 is less than the required low-pressure turbine cooling steam flow rate under the condition where the pressure is not supplied, the pressure set value j of the low-pressure control valve 22 is reduced to reduce the low-pressure control value. Control is performed so that the opening degree of the valve 22 is increased.

  Further, under the condition that sufficient cooling steam is supplied to the low pressure steam turbine 3c via the high pressure control valve 17 and the high pressure steam turbine 3a, the pressure set value j of the low pressure control valve 22 is increased, Control to reduce the opening.

  That is, in the present embodiment, the amount of steam generated from the low-pressure drum 15 is increased by reducing the pressure set value j of the low-pressure adjusting valve 22, and the amount of cooling steam of the low-pressure steam turbine 3c is ensured.

(Effect of 1st Embodiment)
As described above, according to the present embodiment, when the low-pressure adjusting valve 22 is opened after the load is shut off, the opening of the low-pressure adjusting valve 22 is controlled so as to ensure the necessary low-pressure steam turbine cooling steam flow rate. It is possible to prevent overheating due to windage of the steam turbine 3c.

(Second Embodiment)
(Configuration of control device)
FIG. 4 is a control block diagram showing a second embodiment of the single-shaft combined cycle power plant according to the present invention. In addition, since the structure and effect | action of the single shaft type combined cycle power plant of this embodiment are the same as that of the said 1st Embodiment shown in FIG. 1, the description is abbreviate | omitted. Further, in the control block diagram of the present embodiment shown in FIG. 4, the same reference numerals are given to components having the same functions as those in the first embodiment shown in FIG. I will explain only.

  As shown in FIG. 4, a rate of change (positive value) when the pressure set value n of the high-pressure turbine bypass valve 50 is raised is set in the setting device 207 in advance. On the other hand, the setting device 208 is set in advance with a change rate (negative value) when the pressure set value n of the high-pressure turbine bypass valve 50 is lowered.

  The upper limit limiter 212 is determined by the maximum working pressure of the steam pipe from the high pressure drum 13 to the high pressure control valve 17, the set value of the safety valve installed on the steam pipe, or the alarm set value for the steam pipe pressure. An upper limit limit value for the pressure set value of the high-pressure turbine bypass valve 50 is set in advance, and the value of the signal from the adder 111 is compared with the pressure set value n.

  The lower limit limiter 213 is preset with a lower limit limit value for the pressure set value n of the high pressure turbine bypass valve 50 determined in operation or by mechanical characteristics and constraints of the high pressure drum 13. And the pressure set value n are compared.

  In the change rate limiter 214, a mechanical restriction (change rate) such as a high pressure drum with respect to the change rate of the set value of the high pressure turbine bypass valve 50 is set in advance, and the change rate with respect to the signal from the lower limit limiter 213 is set. Make restrictions.

(Operation of control device)
As shown in FIG. 4, in the control device 70, the setting device 207 is set in advance with a rate of change (positive value) when the pressure set value n of the high-pressure turbine bypass valve 50 is increased, and the output is A positive change rate g is output to the switch 106. On the other hand, the setting device 208 is set in advance with a rate of change (negative value) when the pressure set value n of the high-pressure turbine bypass valve 50 is lowered, and is output to the switch 110 as a negative rate of change f. The

  The upper limiter 212 is determined by the maximum working pressure of the steam pipe from the high pressure drum 13 to the high pressure regulating valve 17, the set value of the safety valve installed on the steam pipe, or the alarm set value for the steam pipe pressure. The upper limit limit value for the pressure set value n of the high-pressure turbine bypass valve 50 is set in advance, the value of the signal from the adder 111 is compared with the pressure set value n, and the smaller value is set as the lower limit limiter. To 213. The lower limit limiter 213 is preset with a lower limit limit value for the pressure set value n of the high pressure turbine bypass valve 50 determined in operation or by mechanical characteristics and constraints of the high pressure drum 13. Is compared with the pressure set value n, and the larger value is output to the change rate limiter 214.

  This rate-of-change limiter 214 is preset with mechanical constraints (rate of change) such as the influence on the water level due to the pressure change of the high-pressure drum 13 with respect to the rate of change of the pressure set value n of the high-pressure turbine bypass valve 50. The rate of change is limited with respect to the signal from the lower limit limiter 213, and the pressure set value n of the high pressure turbine bypass valve 50 is obtained.

  Next, the low pressure steam pressure on the inlet side of the high pressure control valve 17 is detected by the detector 57 and input to the subtractor 115 as the high pressure steam pressure signal o. The subtractor 115 performs subtraction between the pressure set value n output from the change rate limiter 214 and the value of the high-pressure steam pressure signal o, and outputs a deviation signal l to the PID calculator 116. The PID calculator 116 outputs the opening command value p to the high-pressure turbine bypass valve 50 so that the deviation signal l becomes zero.

  Therefore, in this control device 70, the low pressure regulating valve 22 after the occurrence of load interruption may be opened, and sufficient cooling steam is supplied to the low pressure steam turbine 3c via the high pressure regulating valve 17 and the high pressure steam turbine 3a. If the low-pressure steam flow rate passing through the low-pressure control valve 22 is less than the required low-pressure turbine cooling steam flow rate under the condition where the pressure is not supplied, the pressure set value n of the high-pressure turbine bypass valve 50 is increased to increase the high pressure Control is performed so that the opening degree of the turbine bypass valve 50 is reduced. Further, under the condition that sufficient cooling steam is supplied to the low-pressure steam turbine 3c via the high-pressure control valve 17 and the high-pressure steam turbine 3a, the pressure set value n of the high-pressure turbine bypass valve 50 is lowered, and the high-pressure turbine bypass valve It controls so that the opening degree of 50 becomes large.

  That is, in the case of the two-pressure type exhaust heat recovery boiler 7 as in the present embodiment, the pressure set value n of the high pressure turbine bypass valve 50 is increased to change the heat collection balance in the exhaust heat recovery boiler 7 from the high pressure system to the low pressure system. The amount of steam from the low-pressure drum 15 is increased by reducing the amount of heat exchange in the high-pressure system and increasing the amount of heat exchange in the low-pressure system, and necessary cooling supplied to the low-pressure steam turbine 3c. The amount of steam is secured.

(Effect of 2nd Embodiment)
Thus, according to this embodiment, when the low-pressure turbine cooling steam flow rate is insufficient, the amount of steam generated from the high-pressure drum 13 is reduced by increasing the pressure set value n of the high-pressure turbine bypass valve 50, that is, The amount of heat exchange with the exhaust gas of the gas turbine 1 in the exhaust heat recovery boiler 7 in the high-pressure steam system is reduced. As a result, the amount of heat exchange in the low-pressure steam system is increased, the amount of steam generated from the low-pressure drum 15 can be increased, and the necessary amount of cooling steam supplied to the low-pressure steam turbine 3c is secured. It is possible to prevent overheating due to windage of the low-pressure steam turbine 3c.

(Third embodiment)
(Power plant configuration)
FIG. 5 is a system diagram showing a third embodiment of the single-shaft combined cycle power plant according to the present invention. FIG. 6 is a block diagram showing a control device 71 for the intermediate pressure turbine bypass valve 51 of FIG. 5 and 6, the same components as those of the first embodiment shown in FIGS. 1 and 2 are denoted by the same reference numerals, description thereof is omitted, and only different configurations and operations are described.

  While the first embodiment is a single-shaft combined cycle power plant configured with a high-pressure and low-pressure two-pressure steam system, this embodiment shown in FIG. 5 is a high-pressure, medium-pressure, and low-pressure three-pressure steam. This is a single-shaft combined cycle power plant configured by the system.

  As shown in FIG. 5, in the uniaxial combined cycle power plant of this embodiment, the exhaust heat recovery boiler 7 includes an intermediate pressure drum 14 that generates intermediate pressure steam that is lower in pressure than high pressure steam and higher in pressure than low pressure steam. The intermediate pressure superheater 11 connected to the intermediate pressure drum 14 and the reheater 9 for generating high-temperature reheat steam are further provided.

  Moreover, this embodiment arrange | positions coaxially with the low temperature reheat system 18 which combines the exhaust steam from the high pressure steam turbine 3a with medium pressure steam, and supplies it to the reheater 9, and the high pressure steam turbine 3a and the low pressure steam turbine 3c. And an intermediate pressure steam turbine 3b driven by the high-temperature reheat steam supplied from the reheater 9 via the high-temperature reheat steam pipe 61. The high-temperature reheat steam pipe 61 is provided with a reheat control valve 20 and a detector 58 that detects a low-pressure steam pressure on the inlet side of the reheat control valve 20.

  In the high temperature reheat steam pipe 61, an intermediate pressure turbine bypass system 82 is branched upstream of the detector 58, and the intermediate pressure turbine bypass valve 51 is interposed in the intermediate pressure turbine bypass system 82. The intermediate pressure turbine bypass system 82 is connected to the condenser 30 in the same manner as the high pressure turbine bypass system 81 and the low pressure turbine bypass system 83 described above.

  Further, the low-pressure turbine steam supply system 62 is configured to join the high-pressure reheat steam and the low-pressure steam, which are decompressed by work in the intermediate-pressure steam turbine 3b, to form the low-pressure turbine steam of the low-pressure steam turbine 3c. Yes.

  The control device 71 includes detection signals of a detector 40 for detecting the low-pressure steam flow rate, a detector 55 for detecting the low-pressure turbine exhaust pressure, and a detector 58 for detecting the low-pressure steam pressure on the inlet side of the reheat control valve 20. On the other hand, the control device 71 outputs opening control signals for the high-pressure control valve 17, the reheat control valve 20, and the intermediate-pressure turbine bypass valve 51.

  Therefore, when the load is interrupted, the high pressure control valve 17 and the reheat control valve 20 are closed. Therefore, the intermediate pressure steam generated in the intermediate pressure drum 14 is opened by opening the intermediate pressure turbine bypass valve 51. It escapes to the condenser 30 via the bypass system 82. And the control apparatus 71 controls the opening degree so that the pressure setting value of the intermediate pressure turbine bypass valve 51 is increased, so that the generated flow rate of the low pressure steam is increased.

(Configuration of control device)
As shown in FIG. 6, in the control device 71, a rate of change (positive value) when the set value q of the intermediate pressure turbine bypass valve 51 is raised is set in advance in the setter 307. On the other hand, in the setting device 308, a rate of change (negative value) when the set value q of the intermediate pressure turbine bypass valve 50 is lowered is set in advance, and is output to the switcher 110 as a negative rate of change f.

  The upper limit restrictor 312 includes a maximum working pressure of the steam pipe from the intermediate pressure drum 14 to the low temperature reheat system 18, a set value of a safety valve (not shown) installed on the steam pipe, or an alarm set value for the steam pipe pressure. The upper limit value for the set value of the intermediate pressure turbine bypass valve 51 determined by the above is preset.

  The lower limit limiter 313 is preset with a lower limit limit value for the set value of the intermediate pressure turbine bypass valve 51 that is determined in terms of operation or mechanical characteristics / restrictions of the intermediate pressure drum 14. The change rate limiter 314 is preset with mechanical constraints (change rate) such as the intermediate pressure drum 14 with respect to the change rate of the set value of the high-pressure turbine bypass valve 50, and the signal from the lower limit limiter 313 is included in the change rate limiter 314. The rate of change is limited.

(Operation of control device)
As shown in FIG. 6, in the control device 71, the setting device 307 is set in advance with a rate of change (a positive value) when the pressure setting value q of the intermediate pressure turbine bypass valve 51 is increased, and its output. Is output to the switch 106 as a positive change rate g. On the other hand, the setting device 308 is set in advance with a rate of change (negative value) when the pressure setting value q of the intermediate pressure turbine bypass valve 50 is lowered, and is output to the switch 110 as a negative rate of change f. Is done.

  The upper limiter 312 has a maximum working pressure of the steam pipe from the intermediate pressure drum 14 to the low temperature reheat system 18, a set value of a safety valve (not shown) installed on the steam pipe, or an alarm setting for the steam pipe pressure. An upper limit value with respect to the pressure setting value q of the intermediate pressure turbine bypass valve 51 determined by the value or the like is set in advance, the value of the signal from the adder 111 is compared with the pressure setting value q, and the value is small Is output to the lower limiter 313. The lower limit limiter 313 is preset with a lower limit limit value for the pressure setting value q of the intermediate pressure turbine bypass valve 51 determined in operation or by mechanical characteristics and restrictions of the intermediate pressure drum 14. The value of the signal from the device 312 is compared with the pressure set value n, and the larger value is output to the change rate limiter 314.

  This rate-of-change limiter 314 is preset with mechanical constraints (rate of change) such as the influence on the water level due to the pressure change of the intermediate pressure drum 14 with respect to the rate of change of the pressure setting value q of the high-pressure turbine bypass valve 50. The rate of change is limited with respect to the signal from the lower limit limiter 313, and the pressure set value q of the intermediate pressure turbine bypass valve 51 is obtained.

  Next, the low pressure steam pressure on the inlet side of the reheat control valve 20 is detected by the detector 58 and input to the subtractor 115 as an intermediate pressure steam pressure signal r. The subtractor 115 performs subtraction between the pressure set value q output from the change rate limiter 314 and the value of the intermediate pressure steam pressure signal r, and outputs a deviation signal l to the PID calculator 116. The PID calculator 116 outputs the opening command value s to the intermediate pressure turbine bypass valve 51 so that the deviation signal l becomes zero.

  Therefore, in this control device 71, it is a condition that the low pressure regulating valve 22 after the occurrence of load interruption may be opened, and sufficient cooling steam is supplied to the low pressure steam turbine 3c via the high pressure regulating valve 17 and the high pressure steam turbine 3a. When the low-pressure steam flow rate that passes through the low-pressure control valve 22 is less than the required low-pressure turbine cooling steam flow rate under the non-supplied condition, the pressure set value q of the intermediate-pressure turbine bypass valve 51 is increased, Control is performed so that the opening degree of the intermediate pressure turbine bypass valve 51 is reduced.

  Further, under the condition that sufficient cooling steam is supplied to the low-pressure steam turbine 3c via the high-pressure control valve 17 and the high-pressure steam turbine 3a, the pressure set value q of the intermediate-pressure turbine bypass valve 51 is lowered, and the intermediate-pressure turbine Control is performed so that the opening degree of the bypass valve 51 is increased.

  That is, in the case of the three-pressure type exhaust heat recovery boiler 7 as in the present embodiment, the pressure set value q of the intermediate pressure turbine bypass valve 51 is increased, and the heat collection balance in the exhaust heat recovery boiler 7 is adjusted to the intermediate pressure steam system. To the low pressure steam system, the amount of heat exchange in the low pressure steam system is increased, the amount of steam from the low pressure drum 15 is increased, and the low pressure steam turbine 3c is increased. The amount of cooling steam supplied to the is ensured.

(Effect of the third embodiment)
Thus, according to the present embodiment, when the low-pressure turbine cooling steam flow rate is insufficient, the amount of steam generated from the intermediate-pressure drum 14 is reduced by increasing the pressure setting value q of the intermediate-pressure turbine bypass valve 51. That is, the amount of heat exchange with the exhaust gas of the gas turbine 1 in the exhaust heat recovery boiler 7 in the intermediate pressure steam system is reduced. As a result, the amount of heat exchange in the low-pressure steam system is increased, the amount of steam generated from the low-pressure drum 15 can be increased, and the necessary amount of cooling steam supplied to the low-pressure steam turbine 3c is secured. It is possible to prevent overheating due to windage of the low-pressure steam turbine 3c.

(Fourth embodiment)
FIG. 7 is a system diagram showing a fourth embodiment of the single-shaft combined cycle power plant according to the present invention. The fourth embodiment is a modification of the third embodiment shown in FIGS. 5 and 6. In FIG. 7, the same components as those in FIG. Only the different configurations and operations will be described.

  In the single-shaft combined cycle power plant shown in FIG. 5, the gas turbine 1 is an air cooling system that uses air as a cooling medium in the high-temperature portion, whereas the gas turbine 1 of the single-shaft combined cycle power plant according to the present embodiment. Adopts a steam cooling method using steam as a cooling medium in the high temperature part.

  As shown in FIG. 7, in the single-shaft combined cycle power plant of this embodiment, a cooling steam system 45 for cooling the high temperature part of the gas turbine 1 is interposed between the low temperature reheat system 18 and the reheater 9. Is intervening. The steam of the cooling steam system 45 is guided to the gas turbine 1 by a steam forward pipe (not shown), and after cooling the high temperature portion, the steam is led to a steam return pipe (not shown) and returned to the cooling steam system 45. Yes.

  The steam that has cooled the high-temperature portion of the gas turbine 1 is introduced into the low-temperature reheat system 18 through the pipe 46 and the check valve 47.

  Thus, according to the present embodiment, the cooling steam system 45 for cooling the high temperature part of the gas turbine 1 is interposed between the low temperature reheating system 18 and the reheater 9, so that the high temperature part Despite the use of steam as the cooling medium, the same effects as in the third embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Gas turbine, 2 ... Compressor, 3 ... Steam turbine, 3a ... High pressure steam turbine, 3b ... Medium pressure steam turbine, 3c ... Low pressure steam turbine, 4 ... Generator, 5 ... Combustor, 6 ... Inlet guide blade, 7 ... Waste heat recovery boiler, 9 ... Reheater, 10 ... High pressure superheater, 11 ... Medium pressure superheater, 12 ... Low pressure superheater, 13 ... High pressure drum, 14 ... Medium pressure drum, 15 ... Low pressure drum, 16 ... High pressure main steam pipe, 17 ... High pressure control valve, 18 ... Low temperature reheat system, 20 ... Reheat control valve, 21 ... Low pressure main steam pipe, 22 ... Low pressure control valve, 24 ... Auxiliary steam supply pipe, 27 ... Startup boiler 28 ... Feed water pump, 29 ... Circulating water pump, 30 ... Condenser, 34 ... Control valve, 35 ... Low pressure steam isolation valve, 38 ... Revolution detector, 39 ... Detector, 40 ... Detector, 41 ... Detector 45 ... Cooling steam system 46 ... Piping 47 ... Check valve 5 DESCRIPTION OF SYMBOLS ... High pressure turbine bypass valve, 51 ... Medium pressure turbine bypass valve, 52 ... Low pressure turbine bypass valve, 55 ... Detector, 56 ... Detector, 57 ... Detector, 58 ... Detector, 61 ... High temperature reheat steam pipe, 62 DESCRIPTION OF SYMBOLS ... Low pressure turbine steam supply system, 70 ... Control device, 71 ... Control device, 81 ... High pressure turbine bypass system, 82 ... Medium pressure turbine bypass system, 83 ... Low pressure turbine bypass, 100 ... Prime motor part, 101 ... Setter, 102 ... Function generator 103 ... Comparator 104 ... AND circuit 105 ... NOT circuit 106 ... Switcher 107 ... Setter 108 ... Setter 109 ... Setter 110 ... Switcher 111 ... Adder 112 ... upper limit limiter, 113 ... lower limit limiter, 114 ... change rate limiter, 115 ... subtractor, 116 ... PID calculator, 207 ... setter, 208 ... setter, 212 ... on Limiter, 213 ... lower limiter, 214 ... change rate limiter, 307 ... setter, 308 ... setter, 312 ... upper limiter, 313 ... lower limiter, 314 ... change rate limiter.

Claims (6)

A high-pressure steam turbine that is arranged coaxially with the gas turbine and is driven by being supplied with high-pressure steam from a high-pressure drum of an exhaust heat recovery boiler via a high-pressure control valve;
The low-pressure steam from the low-pressure drum that generates low-pressure steam having a pressure lower than that of the high-pressure drum is supplied via a low-pressure control valve, and the low-pressure steam and the high-pressure steam that has worked in the high-pressure steam turbine are merged. A low pressure turbine steam supply system for supplying steam as low pressure turbine steam;
A low-pressure steam turbine disposed coaxially and coupled to the gas turbine and the high-pressure steam turbine and driven by the low-pressure turbine steam;
During the extremely low fuel operation of the gas turbine, including no-load rated speed operation after load interruption of the generator that is arranged coaxially with the gas turbine, the high pressure regulator is controlled to be fully closed, and Control means for controlling the pressure setting value of the low pressure regulating valve to be lowered;
A single-shaft combined cycle power plant comprising: A high-pressure steam turbine that is arranged coaxially with the gas turbine and is driven by being supplied with high-pressure steam from a high-pressure drum of an exhaust heat recovery boiler via a high-pressure control valve;
The low-pressure steam from the low-pressure drum that generates low-pressure steam having a pressure lower than that of the high-pressure drum is supplied via a low-pressure control valve, and the low-pressure steam and the high-pressure steam that has worked in the high-pressure steam turbine are merged. A low pressure turbine steam supply system for supplying steam as low pressure turbine steam;
A low-pressure steam turbine disposed coaxially and coupled to the gas turbine and the high-pressure steam turbine and driven by the low-pressure turbine steam;
A high-pressure bypass system bypassing the high-pressure steam and interposing a high-pressure turbine bypass valve;
During the extremely low fuel operation of the gas turbine, including no-load rated speed operation after load interruption of the generator that is arranged coaxially with the gas turbine, the high pressure regulator is controlled to be fully closed, and Control means for controlling the pressure setting value of the high-pressure turbine bypass valve to increase;
A single-shaft combined cycle power plant comprising: A high-pressure steam turbine that is arranged coaxially with the gas turbine and is driven by being supplied with high-pressure steam from a high-pressure drum of an exhaust heat recovery boiler via a high-pressure control valve;
A low-pressure steam turbine that is coaxially disposed and coupled to the gas turbine and the high-pressure steam turbine and is driven by low-pressure steam;
A high-pressure bypass system bypassing the high-pressure steam and interposing a high-pressure turbine bypass valve;
Reheating to generate high-temperature reheat steam by combining medium-pressure steam from an intermediate-pressure drum that generates intermediate-pressure steam at a pressure lower than that of the high-pressure steam and higher than that of low-pressure steam with exhaust steam from the high-pressure steam turbine. A low-temperature reheat system to supply
An intermediate pressure steam turbine that is arranged coaxially with the high pressure steam turbine and the low pressure steam turbine and is driven by being supplied with high temperature reheat steam from the reheater via an intermediate pressure control valve;
A low-pressure turbine steam supply system for driving the low-pressure steam turbine by joining the high-temperature reheat steam and the low-pressure steam, which are decompressed by working in the intermediate-pressure steam turbine;
An intermediate pressure bypass system that bypasses the intermediate pressure steam and is provided with an intermediate pressure turbine bypass valve;
The high pressure regulating valve and the intermediate pressure control valve are fully closed during extremely low fuel operation of the gas turbine, including no-load rated speed operation after load interruption of a generator arranged coaxially with the gas turbine. Control means for performing control and controlling so as to increase the pressure set value of the intermediate pressure turbine bypass valve;
A single-shaft combined cycle power plant comprising: A gas turbine, a high-pressure steam turbine, a low-pressure steam turbine, and a generator are coaxially arranged and connected, and combustion gas is sent to the gas turbine to drive it, and the exhaust gas of the combustion gas is used as a heat source for high pressure in the exhaust heat recovery boiler. Generating low-pressure steam having a pressure lower than that of the high-pressure steam, supplying the high-pressure steam via a high-pressure control valve to work on the high-pressure steam turbine, and generating the low-pressure steam via the low-pressure control valve. In the operation method of the single-shaft combined cycle power plant in which the low-pressure steam turbine supplies the work and supplies the work,
A fully-closed control step for performing control to fully close the high-pressure control valve during extremely low fuel operation of the gas turbine including no-load rated speed operation after load interruption of the generator;
A pressure set value control step for controlling the pressure set value of the low pressure adjusting valve to decrease;
A method for operating a single-shaft combined cycle power plant, comprising: A gas turbine, a high-pressure steam turbine, a low-pressure steam turbine, and a generator are coaxially arranged and connected, and combustion gas is sent to the gas turbine to drive it, and the exhaust gas of the combustion gas is used as a heat source for high pressure in the exhaust heat recovery boiler. Generating low-pressure steam having a pressure lower than that of the high-pressure steam, supplying the high-pressure steam via a high-pressure control valve to work on the high-pressure steam turbine, and generating the low-pressure steam via the low-pressure control valve. In the operation method of the single-shaft combined cycle power plant in which the low-pressure steam turbine supplies the work and supplies the work,
A fully-closed control step for performing control to fully close the high-pressure control valve during extremely low fuel operation of the gas turbine including no-load rated speed operation after load interruption of the generator;
A pressure set value control step for controlling the pressure set value of the high pressure turbine bypass valve interposed in the high pressure bypass system to bypass the high pressure steam; and
A method for operating a single-shaft combined cycle power plant, comprising: A gas turbine, a high-pressure steam turbine, an intermediate-pressure steam turbine, a low-pressure steam turbine, and a generator are arranged coaxially and connected to each other, and a combustion gas is sent to the gas turbine for driving, and the exhaust gas of the combustion gas is used as a heat source to exhaust heat. The recovery boiler generates high-pressure steam, and generates low-pressure steam having a pressure lower than that of the high-pressure steam and low-pressure steam having a pressure lower than that of the high-pressure steam, and the intermediate-pressure steam is discharged from the high-pressure steam turbine. The high-temperature reheat steam and the low-pressure steam, which are supplied to a reheater that generates high-temperature reheat steam and is reduced in pressure by working in the intermediate-pressure steam turbine via an intermediate pressure control valve. In a method for operating a single-shaft combined cycle power plant in which the low-pressure steam turbines are combined to perform work,
A fully-closed control step for performing control to fully close the high-pressure control valve and the intermediate pressure control valve during extremely low fuel operation of the gas turbine including no-load rated speed operation after load interruption of the generator;
A pressure setting value control step for controlling the pressure setting value of the intermediate pressure turbine bypass valve interposed in the intermediate pressure bypass system for bypassing the intermediate pressure steam; and
A method for operating a single-shaft combined cycle power plant, comprising:

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