JPH0211807A - Low pressure turbine bypass controller - Google Patents

Abstract

PURPOSE:To prolong the service life of a turbine by installing an aimed value setting device for setting the aimed value of the reheating steam pressure for the aimed initial load of a thermal power plant in each starting mode, control logic for designating the starting mode and a signal selector for outputting each aimed value according to the starting mode. CONSTITUTION:In the hot mode, the deviation from a reheating steam pressure P1 is detected by a deviation detector 107 from a signal selecting logic 10 and a signal selector 104, having an output signal (alpha) supplied from a signal generator 101 in an aimed value setting circuit 110 as aimed value, and a low pressure turbine bypass control signal (opening degree signal) 109 is obtained by a PI calculator 108, and the opening degree of a low pressure turbine bypass valve 10 is adjusted. Therefore, the pressure P1 is increased, having the output signal (alpha) as aimed value, until the load becomes equal to an aimed initial load, and when the aimed initial load is reached, the pressure is increased, having the first stage steam pressure P2 as aimed value. Therefore, the overheat of a high pressure turbine 3 is prevented. In the cold mode, an output signal (beta) is selected by a signal generator 102.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for controlling the start-up of a steam turbine of a thermal power plant, and in particular, the present invention relates to a control device for controlling the start-up of a steam turbine of a thermal power plant. The present invention relates to a low pressure turbine bypass control device that optimally controls a low pressure turbine bypass valve.

[Conventional technology]

A conventional low pressure turbine bypass control device is disclosed in, for example, Japanese Patent Laid-Open No. 16210/1983.

FIG. 6 is a schematic diagram showing a steam system of a thermal power plant controlled by the low pressure turbine bypass control device.

Steam generated from the boiler 2 is guided to the high pressure turbine 3. A reheater 13 is installed in a high-pressure turbine bypass pipe branched from a steam pipe that leads steam to the high-pressure turbine 3, and a check valve 16
to reheat.

One steam pipe branching downstream of the reheater 13 is sequentially connected to the condenser 6 via the intermediate pressure turbine 4 and the low pressure turbine 5, and the other branching steam pipe, the low pressure turbine bypass pipe, is connected to the steam flow rate. Low pressure turbine bypass valve 10 as a control valve
It is connected to the condenser 6 via.

The low-pressure turbine bypass control device 1 controls the reheat steam pressure at the outlet side of the reheater 13 in order to prevent the high-pressure turbine 3 from being overheated due to an increase in the first-stage rear lid air pressure P2, which is the internal steam pressure of the high-pressure turbine 3. P□ and the first-stage rear lid air pressure P2 are measured, and the opening degree of the low-pressure turbine bypass valve 10 is controlled so that the reheat steam pressure P1 matches the first-stage rear lid air pressure P2. In such a low pressure turbine bypass control device 1, during load operation of a thermal power plant, the first stage rear cover air pressure P2
The opening degree of the low-pressure turbine bypass valve 10 is adjusted so that the reheat steam pressure P matches the first stage rear lid air pressure P2. On the other hand, at the time of starting a thermal power plant, the reheat steam pressure P
The opening degree of the low pressure turbine bypass valve 10 is adjusted so that the Note that the check valve 16 is provided to prevent steam from flowing back from the reheater 13 side to the high-pressure turbine 3 side when the first stage post-steam pressure P2 is lower than the reheating steam pressure P. .

[Problem to be solved by the invention]

As a result of the inventor's detailed study of the functions of conventional low-pressure turbine bypass control devices, it was found that when a thermal power plant (hereinafter simply referred to as a plant) is started up, regardless of the startup mode that differs depending on whether the amount of steam generated by the boiler is high or low, in other words, the plant It was found that because the target value of reheat steam pressure was set constant regardless of the target initial load of the turbine, depending on the startup mode, the inside of the turbine could overheat. The control method will be explained using FIGS. 4 and 5.

FIG. 5 is a diagram showing the circuit configuration of the steam system of the plant explained in FIG. 6 and the conventional low-pressure turbine bypass control device. Here, since the steam system of the plant has been described above, it will be omitted, and only the low-pressure turbine bypass control device will be explained.

Functionally, the low-pressure turbine bypass control device 100 includes a circuit that sets a target value of reheat steam pressure, and an arithmetic circuit that processes the target value and the detected value of the steam pressure of the plant. In FIG. 5, the circuit for setting the target value of the reheat steam pressure consists of a signal generator 101, and the arithmetic circuit for processing the target value and the detected value of the steam pressure is an arithmetic circuit 112. Function generator 105 to be explained. High value priority circuit 106. Deviation detector 107
and a PI calculator 108.

During load operation of the plant, the function generator 105
Input the post-stage lid air pressure P2, find the first post-degradation steam pressure target value, find the deviation between the first post-depletion steam pressure target value and the reheat steam pressure Pyu using the deviation detector 1.7, and calculate the deviation. According to the low pressure turbine bypass control signal 109 obtained by the PI calculator using
The opening degree of the low-pressure turbine bypass valve 10 is adjusted so that it matches 2. However, at the time of plant startup, the flow rate of steam generated from the boiler is small, so the first stage rear cover air pressure P2 is
Pressure has not increased enough to meet the target initial load required to start the plant. Therefore, until the target initial load is obtained, the signal generator [-〇] serves as the target value setting circuit.
Define the target value for reheat steam pressure P work. If the target initial load is achieved, the high value priority circuit 106 selects the first stage rear lid air pressure P2 as the target value of the reheat steam pressure P1.

In this conventional technology, the target value of the reheat steam pressure P at the time of plant startup is specified by the signal generator 10 as a constant value regardless of the target initial load of the plant. Since the target initial loads are different, a problem occurs as shown in FIG. 4 below. That is, when the start-up mode of the plant is, for example, a hot mode in which the flow rate of steam generated by the boiler is large, the target initial load is set to a, and a corresponding target value α of the reheat steam pressure P is set in the signal generator 101. Until the load reaches a, the opening degree of the low-pressure turbine bypass valve 10 is adjusted so that the reheat steam pressure P1 matches the output α of the signal generator 101. When the load becomes a, the reheat steam pressure P.

The target value of is switched to the first-stage rear cover air pressure P2 from the output of the signal generator 101, but at this time, there is no deviation between the reheat steam pressure P and the first-stage post-death steam pressure P2, and the high pressure No overheating within the turbine 3 occurs. However, when the startup mode of Plan 1~ is, for example, a cold mode in which the flow rate of steam generated by the boiler is low, the target initial load is lower than in the hot mode due to various conditions of the boiler, for example, the temperature of the boiler equipment is lower. is low and b roars. However, since the output of the signal generator 101 remains at α, the load becomes b.
At the time when , a deviation of ΔP occurs between the reheating steam pressure P and the eyelid value α. Therefore, the low-pressure turbine bypass control device 1 reduces the opening degree of the low-pressure turbine bypass valve 1o so that ΔP becomes ○, increases the reheat steam pressure P more than necessary for the initial load amount, and accordingly As a result, the first stage rear cover pressure P2 also increases, which causes overheating in the high pressure turbine bypass 3, which poses a problem in that the high pressure turbine 3 is adversely affected by thermal stress or the like.

An object of the present invention is to solve the above problems, set a target value of reheat steam pressure commensurate with the target initial load of the plant, which varies depending on the startup mode at the time of plant startup, and control the low-pressure turbine bypass valve. An object of the present invention is to provide a low pressure turbine bypass control device.

[Means to solve the problem]

The above object includes a boiler, a high-pressure turbine and a low-pressure turbine driven by the steam of the boiler, and a reheater is provided in a high-pressure turbine bypass pipe branched from a steam pipe that leads steam from the boiler to the high-pressure turbine. , introducing the steam discharged from the high pressure turbine to the reheater via a check valve, one branch steam pipe branching downstream of the reheater is connected to a condenser via a low pressure turbine, The other branched steam pipe, the low pressure turbine bypass pipe, is a low pressure turbine bypass control device that controls the thermal power plant connected to the condenser via a steam flow rate control valve, and is configured to control the target initial load at the time of startup of the thermal power plant. a target value setting circuit that sets a target value of the reheat steam pressure on the outlet side of the reheater; and a target value setting circuit that sets a target value of the reheat steam pressure on the outlet side of the reheater; A low-pressure turbine bypass control device comprising: a calculation circuit that calculates the opening degree of the steam flow rate control valve and outputs an opening signal based on the detected value of the reheat steam pressure and the steam pressure in the high-pressure turbine; The target value setting circuit includes a signal generator that sets a target value of the reheat steam pressure for a target initial load of the thermal power plant that is determined for each startup mode depending on whether the amount of steam generated by the boiler is high or low; a signal selection logic that outputs a designated signal specifying one of the startup modes; and a signal selector that inputs the designated signal and selects and outputs a target value of the designated startup mode from the target value setting circuit. This is achieved by a low-pressure turbine bypass control device characterized by comprising:

Further, it is sufficiently effective if the startup mode is set to two types: a hot mode when the amount of steam generated by the boiler is large and a cold mode when the amount of steam generated by the boiler is small.

[Effect]

By configuring the turbine bypass control device of the present invention as described above, in the target value setting device, the signal generator outputs the reheat steam pressure for each target initial load at the time of plant startup determined for each startup mode. The selection logic outputs a specified signal specifying the startup mode, and the signal selector inputs the specified signal and the target value setting circuit selects the target value of the signal generator corresponding to the specified signal. is selected and output, and the arithmetic circuit inputs the target value and the detected value of the reheat steam pressure, calculates the deviation between these values, and outputs an opening signal. Thus, at startup, the steam flow rate control valve operates in the direction in which the deviation becomes zero based on the opening degree signal, and the reheat steam pressure increases to reach the target value and balance with the target initial load at the time of plant startup.

In addition, when the starting mote is in the real mode, the target value of the reheat steam pressure is set high and the reheat steam pressure is balanced at a high value, and when the starting mote is in the cold mode, the reheat steam pressure is set high. The target value is set low, and the reheat steam pressure is balanced at a low value.

By the way, in the case of cold mode, if the target value is set to a high value for hot mode, when the reheat steam pressure reaches the target value, the reheat steam pressure will be equal to the target initial load of the thermal power plant corresponding to cold mode. There is an unbalance, that is, the reheating pressure is too high, so the steam flowing into the high pressure turbine is blocked by the check valve and does not flow towards the reheater.
Too much steam flows into the high pressure turbine, causing it to overheat.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a diagram schematically showing a low-pressure turbine bypass control device according to an embodiment and a steam system of a thermal power plant controlled by the low-pressure turbine bypass control device. The operation of the steam system of a thermal power plant and the low-pressure turbine bypass control device during load operation of a thermal power plant is the same as that explained with reference to FIG. 6 in the prior art section, so it will be omitted here to avoid duplication. The target value setting circuit 110 regarding the operation of the low-pressure turbine bypass control device at the time of startup of a thermal power plant, which is different from the conventional technology, will be mainly explained.

At the time of startup of the thermal power plant, that is, until the load of the thermal power plant reaches the target value initial load, the target value setting circuit 110 determines the target value of the reheat steam pressure. The present target value setting circuit 110 does not output only one target value for reheat steam pressure as in the conventional case, but outputs a target value for reheat steam pressure that matches the startup mode of the plant. For example, the startup mode of the plant is set to a hot mode in which the amount of steam generated by the boiler is large and a cold mode in which the amount of steam generated by the boiler is small. In FIG. 1, when in the hot mode, the low pressure turbine bypass control device 1 uses the signal selection logic 103 and the signal selector 104 to set the output signal α from the signal generator 101 in the target value setting circuit as the target value, and set the output signal α from the signal generator 101 in the target value setting circuit as the target value. Detector 1
07, the deviation from the reheat steam pressure P1 is detected, and the PI calculator 108 obtains a low pressure turbine bypass control signal 109, which is an opening signal, and adjusts the opening of the low pressure turbine bypass valve 10, which is a steam flow rate control valve. As a result, as shown in FIG. 2, until the load reaches the target initial load a, the reheat steam pressure P increases with the output signal α from the target value setting circuit 110 as the target, and the When the load a is reached, the reheating steam pressure P□ is balanced at a value α commensurate with the target initial load.

After that, the reheat steam pressure P□ increases with the first stage steam pressure P2 as the target. Therefore, the first stage steam pressure P2 does not increase more than necessary, so the inside of the high-pressure turbine 3 is not heated more than necessary. Also, when in cold mode,
Turbine bypass control bag W1 is signal selection logic 103
And the signal selector 104 selects the output signal β from the signal generator 102 in the target value setting circuit. Using the output signal β as a target value, a deviation detector 107 detects the deviation from the reheat steam pressure P, a PI calculator 108 obtains a low pressure turbine bypass control signal 109, and adjusts the opening degree of the low pressure turbine bypass valve 10. do.

As a result, until the load reaches the target initial load as shown in FIG.
The reheat steam pressure P1 increases with the target as the target initial load, and when the load reaches the target initial load, the reheat steam pressure P1 balances at a value β commensurate with the target initial load. After that, the reheat steam pressure P1 increases with the first stage steam pressure P2 as the target.

Therefore, the first stage steam pressure P2 does not increase more than necessary, so the inside of the high-pressure turbine does not heat up more than necessary.

From the above, even if the target initial load is different, the reheat steam pressure and the first stage steam pressure will not be increased more than necessary.
Since the inside of the high-pressure turbine is not heated more than necessary, the turbine is not adversely affected.

In this embodiment, the target value is switched between real mode and cold mode in the target value selection circuit 110, but it is also possible to change the target value continuously by providing this function with a rate of change limiter. .

For example, as shown in FIG.
A rate-of-change limiter 111 is provided to define the rate of change when switching. When starting up the plant, the output value of the signal generator 101 is selected as the target value for the reheat steam pressure, but because the flow rate of steam generated from the boiler is small, the first stage rear cover pressure is such that it is difficult to increase the pressure to that extent. If so, the target value of the reheat steam pressure is switched to the output of the signal generator 102. At this time, the target value of the reheat steam pressure is set by the signal generator 1 by the rate of change limiter 111.
From the output value of 01, the output value of the signal generator 102 changes at a prescribed rate of change. In this changing process, the first
When the stage steam pressure P2 and the reheat steam pressure P1 match,
The target value of the reheat steam pressure is switched to the first stage steam pressure.

〔Effect of the invention〕

According to the present invention, a low-pressure turbine bypass control device includes a target value setting device that sets a target value of reheat steam pressure for a target initial load of a thermal power plant for each startup mode, a control logic that specifies a startup mode, and a control logic that specifies a startup mode. The reheating steam pressure is controlled according to the target initial load of the thermal power plant, which varies depending on the start-up mode, without supplying excessive steam to each turbine. The turbine is not affected by adverse effects such as generated thermal stress, and the life of the turbine can be extended. Furthermore, since excess steam that causes overheating of the high-pressure turbine is not supplied, the startup time of the thermal power plant can be shortened, so that efficient operation of the thermal power plant can be realized.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the circuit configuration of a low-pressure turbine bypass control device according to an embodiment of the present invention and the related steam system of a thermal power plant, and FIG. A diagram showing the relationship between heat and steam pressure, FIG. 3 is a diagram showing the circuit configuration of a low-pressure turbine bypass control device according to another embodiment of the present invention and a schematic diagram of the steam system of a related thermal power plant, and FIG. Figure 5 is a diagram showing the relationship between the target initial load of a thermal power plant and reheat steam pressure; Figure 5 is a diagram showing the circuit configuration of a conventional low-pressure turbine bypass control device and a schematic diagram of the related steam system of the thermal power plant; Figure 6 is fire power bran 1
It is a schematic diagram showing the steam system of ~. 1. Low pressure turbine bypass control device, 2. Boiler,
3 - high pressure turbine, 4 intermediate pressure turbine, 5 low pressure turbine, 6... condenser, 10 steam flow rate control valve (low pressure turbine bypass valve), 13... reheater, 16 check valve, 101, 102 ・Target value setter, 103...Signal selection logic, 104 Signal selector, 109 - Opening signal (low pressure turbine bypass control signal), 110 - Target value setting circuit, 112 Arithmetic circuit.

Claims (1)

[Claims] 1. A boiler, a high-pressure turbine and a low-pressure turbine driven by the steam of the boiler, and a steam pipe that guides steam from the boiler to the high-pressure turbine is recirculated to a high-pressure turbine bypass pipe branched from the steam pipe. A heater is provided, the steam discharged from the high pressure turbine is guided to the reheater via a check valve, and one branch steam pipe branching downstream of the reheater is connected to the condenser via the low pressure turbine. The low-pressure turbine bypass pipe connected to the other branch steam pipe is a low-pressure turbine bypass control device for controlling the thermal power plant connected to the condenser via the steam flow rate control valve, and the low-pressure turbine bypass pipe is connected to a target value setting circuit that sets a target value of reheat steam pressure on the outlet side of the reheater with respect to a target initial load of the reheater; a low-pressure turbine bypass having a calculation circuit that calculates the opening degree of the steam flow rate control valve and outputs an opening signal based on the detected value of the reheat steam pressure and the steam pressure in the high-pressure turbine during plant load operation; In the control device, the target value setting circuit generates a signal for setting the target value of the reheat steam pressure for each target initial load of the thermal power plant determined for each startup mode determined depending on whether the amount of steam generated by the boiler is high or low. a signal selection logic that outputs a designated signal specifying one of the startup modes; and a signal selection logic that inputs the designated signal and selects and outputs a target value of the designated startup mode from the target value setting circuit. 1. A low-pressure turbine bypass control device comprising: a signal selector for controlling a low pressure turbine; 2. The low-pressure turbine bypass control device according to claim 1, wherein the startup mode is a hot mode when the amount of steam generated by the boiler is large and a cold mode when it is small.