JPH05296402A - Steam cycle control device - Google Patents

Abstract

PURPOSE:To prevent disturbance on a drum water level by a method wherein a turbine bypassing valve has a function for controlling an outlet pressure of a regulation valve so as to control a differential pressure of the regulation valve. CONSTITUTION:A turbine bypassing valve 19 has a function for controlling a regulation valve with its outlet pressure being applied as a set value, a condition of differential pressure across the regulation valve is added to a steam condition 62 of an opened regulation valve and then a limitation of an opening or closing variation rate of the regulation valve is provided in reference to the differential pressure of the regulation valve 15. That is, when a complex power generating plant is energized, a secondary pressure at the regulation valve 15 is controlled under the turbine bypassing control so as to keep the outlet port pressure of the regulation valve 15 constant. A condition of differential pressure across the regulation valve is added to the steam condition 62 of an opened regulation valve and a limitation of a variation rate of a degree of opening of the regulation valve 15 is given as a function in reference to a condition of differential pressure of the regulation valve. With such an arrangement even in the case that the regulation valve 15 is opened in reference to a completion of the steam condition, the differential pressure across the regulation valve 15 is controlled, so that a flow rate of main steam and its pressure are well controlled and any disturbance can not be given to the drum water level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam cycle control device applied to a combined cycle power plant in which a gas turbine and a steam turbine are combined.

[0002]

2. Description of the Related Art Various improvements in efficiency have been promoted in power generation plants from the viewpoint of effective use of energy resources and economic efficiency. The combined power plant is one of them, and is playing a central role in the thermal power plant.

FIG. 4 is a block diagram showing an example of the structure of a combined power generation plant, which is composed of a gas turbine 1, an HRSG 2, a steam turbine 3 and a generator 4. This is a combined power generation plant that not only generates power by the gas turbine 1 but also guides the combustion exhaust gas to the HRSG 2 and generates heat by recovering heat by the HRSG 2 to drive the steam turbine 3 and generate power by the generator 4. .. In the gas turbine 1, the combustion air is pressurized to burn the fuel and rotate the gas turbine to perform work. After this, the high temperature combustion exhaust gas is guided to HRSG2.

The HRSG 2 is, for example, a high pressure superheater 5, a reheater 6, a high pressure evaporator 7, a high pressure steam drum 16, a high pressure economizer 8, a low pressure superheater 9, a low pressure evaporator 10, a low pressure steam drum 17,
It has a low-pressure economizer 11 and the like, and heat is exchanged with the gas turbine exhaust gas in these heat exchangers to generate steam.

The steam generated in the high-pressure drum 16 is sent to the high-pressure superheater 5, where it becomes superheated steam and the high-pressure steam turbine 21
The high pressure steam turbine 21 is driven to generate electric power by the generator 4. The steam generated in the low-pressure drum 17 is the low-pressure superheater 9
Sent to the low pressure superheated steam. The high-pressure steam turbine outlet steam is mixed with the low-pressure superheated steam, sent to the reheater 6 and reheated, and then sent to the reheat steam turbine 22 to be generated by the generator 4.

The steam that worked in the reheat steam turbine 22 is
After being condensed in the condenser 12, it is pressurized by the water supply pump 13 and is supplied to the high-pressure economizer 8 and the low-pressure economizer 11. In the low pressure economizer 11, after being heated to near the saturation temperature, the low pressure steam drum 17
Sent to. The low-pressure steam drum 17 supplies water to the low-pressure evaporator 10, and the low-pressure evaporator 10 exchanges heat with the gas turbine exhaust gas to generate low-pressure steam. In the high-pressure economizer 8, it is heated to near the saturation temperature and then sent to the high-pressure steam drum 16.
The high-pressure steam drum 16 supplies water to the high-pressure evaporator 7, and the high-pressure evaporator 7 exchanges heat with the gas turbine exhaust gas to generate high-pressure steam. Due to the recent improvement in the performance of gas turbines, the exhaust gas temperature of gas turbines has risen
Since RSG can recover heat, power generation efficiency is improved.

A conventional steam cycle control configuration of the combined cycle power plant will be described with reference to FIG. Here, the low pressure steam system will be described as a representative, but the same applies to the high pressure steam side. The steam cycle control will be described separately for control valve control and turbine bypass control.

In the combined power plant, the throttle valve control does not perform throttling control as in the conventional plant and the throttle valve is operated in the fully open state under the rated condition. Therefore, the regulator valve is controlled by the following control valve open condition 62 {steam condition (pressure, flow rate, Temperature), the plant condition is satisfied, and the starting condition is satisfied}, the control valve 15 is opened and closed at a constant change rate.

[0009] The equipment includes a control valve full open setter 29 for setting the fully open and closed position of the control valve, a control valve fully closed setter 30, a deviation calculator 31 for calculating a deviation from the current set value, and a control valve open. Control valve full-open change rate limiter 32 for restricting the rate change rate, control valve full-close change rate limiter 33, full open / close switch 34 for switching between full open and full close of the valve, and an opening signal from these deviation signals. It is composed of an opening degree integrator 35 for calculating.

In the turbine bypass control, a set value bias calculator 37 for bypassing the pressure signal from the regulator valve inlet pressure detector 26, a set value deviation calculator 38 for calculating a deviation from the current set value, and a set value Change rate limiter 39 that limits the change rate of the set value, set value integrator 41 that calculates the set value from this deviation signal, set value upper and lower limit limiter 42 that limits the upper and lower limits of the set value, main steam at startup Transmitter 43, which sets the pressure
Start-up pressure setter 44, transfer unit 45 that keeps the set value until the control valve opens to a certain opening degree, deviation calculator 46 that calculates the deviation between the set value and the pressure on the front side of the control valve, calculator that proportionally integrates and differentiates this signal
47 、 Function calculator 4 that performs function conversion on this control signal
8 and an opening detector 36 for detecting the opening / closing of the control valve and turning it on at a constant opening to track the turbine bypass control to the main steam pressure. How these controls operate at startup will be described with reference to FIG. 6 by taking the reheated air side as a representative. The same applies to the high pressure side.

On the gas turbine side, the gas turbine 1 is accelerated by start control until the number of revolutions N reaches the rated number of revolutions at start-up, and load control is started when the number of revolutions reaches the rated number of revolutions. Exhaust gas flow rate Q
1 and the exhaust gas temperature T also rise.

Due to the starting characteristics of the combined cycle power plant, the gas turbine 1 can be started early, but the steam cycle side is HRSG.
The start-up is delayed due to the delay due to the heat capacity of 2 and the transmission delay due to the duct and piping. Therefore, in order to match the gas turbine 1 and the steam turbine 3, it is necessary to operate the steam turbine control valve 15 and the turbine bypass valve 19 at the time of startup.

At the time of start-up, the single shot 61 is turned on when the start-up condition is satisfied, the main steam pressure at this time is sent by the transfer device 43, and the pressure set value is held as the setting calculator. Further, since the regulator valve 15 is not open, the opening detector is turned on, and the transfer device 45 operates to set this value as the pressure set value at the time of startup. Heat generation from the exhaust gas of the gas turbine 1 starts steam generation and pressure increase. Since the main steam pressure P1 has not reached this pressure set value, the control output calculated by the deviation calculator 46 and the proportional-plus-integral differentiator 47 becomes negative, the turbine bypass valve remains fully closed, and the pressure is set to the gas turbine 1.
It rises according to the heat input from.

When the high-pressure main steam pressure P1 reaches this pressure setting value, in the high-pressure turbine bypass pressure control, the control output calculated by the deviation calculator 46 and the proportional-plus-integral-differentiator 47 becomes positive, and the turbine bypass valve 19 is opened to open the pressure. Is held at the set value. Steam pressure, temperature, and flow rate increase, and control valve opening conditions
When 62 is established, the switching device 34 becomes the control valve full-open setting device 29 side and the control valve 15 starts to open at a constant change rate determined by the change rate limiter 32, and steam starts to flow to the steam turbine side. When the regulator valve 15 is opened, the opening switch 36 operates and the tracking circuit side 37-39 is selected. The tracking circuit takes in the regulator valve inlet pressure at this time, biases it with the bias calculator 37, and limits the rate of change of the pressure set value.Therefore, the deviation calculator 38 calculates the deviation between the set value and the main steam pressure.
The pressure setting value is obtained by the upper and lower limiter 39 and the integrator 41 which uses the deviation signal as a setting signal. In this way, the main steam pressure set value is tracked to the main steam pressure and gradually raised to the rated pressure.

In FIG. 6, T is the exhaust gas temperature, N is the gas turbine speed, Qg is the exhaust gas flow rate, θ1 is the high pressure control valve opening degree, P1 is the high pressure main steam pressure, H1 is the high pressure drum water level, and Q1 is High-pressure bypass flow rate, θ2 is reheat steam control valve opening, H2 is low-pressure drum water level, P2 is low-pressure main steam pressure, P
3 is the reheat main steam pressure, and Q2 is the reheat turbine bypass flow rate.

[0016]

However, since the control of the control valve and the turbine bypass valve is not well coordinated, there are the following problems.

Since the differential pressure across the regulator valve 15 is large when the regulator valve 15 starts to open under turbine bypass steam conditions, even if the regulator valve 15 is slightly opened, a large amount of steam will flow in and the water level of the drum 17 will suddenly increase. fluctuate. Especially at the time of startup, the regulator 15 has a large differential pressure and a large amount of steam inflow.
Can flow out and damage the steam turbine 22.
The same applies to the high-pressure steam side, but in particular, the reheat-side steam pressure depends on the high-pressure side steam pressure, so the differential pressure becomes large and this effect becomes large. In particular, a combined cycle power plant is suitable for load adjustment due to its small unit capacity and short start-up time, and it is important to solve this problem because it is frequently started and stopped. In view of such a point, the present invention is
It is an object of the present invention to obtain a control device that controls well the main steam flow rate and pressure of a steam turbine and does not disturb the drum water level.

[0018]

The steam cycle control device of the present invention is a steam generator for a combined cycle power plant in which steam is generated by an exhaust heat recovery boiler with exhaust gas that has finished working in a gas turbine to drive the steam turbine. When the opening condition of the steam control valve that controls the steam flowing into the turbine is satisfied, the control valve drive means that opens and closes the steam control valve, and the degree of opening of the turbine bypass valve that bypasses the steam turbine and leads to the condenser Turbine bypass valve drive means that opens and closes the turbine bypass valve to a set value that is set based on the inlet pressure of the regulator valve, and steam control as the opening set value of the turbine bypass valve that is provided in the turbine bypass valve drive means. An opening set value compensator that also takes the outlet pressure of the valve into account, and a differential pressure that takes into account the differential pressure between the inlet pressure and the outlet pressure of the steam control valve to the opening condition of the steam control valve. And Ken setting means, and a closing rate of change difference pressure function calculating means provided to limit the opening rate of change of the steam control valve based on the differential pressure between the inlet pressure and the outlet pressure of the steam control valve.

Further, the steam control valve is opened to control the steam flowing into the steam turbine of the combined cycle power plant in which the exhaust heat recovery boiler generates steam in the exhaust heat recovery boiler to drive the steam turbine. The opening degree of the control valve drive means that opens and closes the steam control valve when the conditions are satisfied and the opening degree of the turbine bypass valve that bypasses the steam turbine and guides the steam to the condenser are determined based on the inlet pressure of the steam control valve. Turbine bypass valve drive means for opening and closing the turbine bypass valve to a set value, a limiter provided in the turbine bypass valve drive means for inputting the steam control valve outlet pressure and limiting the upper and lower limits, and a turbine bypass valve drive A calculator for calculating the opening degree of the turbine bypass valve based on the deviation between the output of the restrictor and the inlet pressure of the steam control valve, and the turbine bypass valve. The opening degree for opening and closing the turbine bypass valve, which is provided in the valve driving means and selects the opening degree command calculated by the calculator at the time of startup, and normally becomes the set value determined based on the inlet pressure of the steam control valve. And a switch for selecting a command.

[0020]

According to the present invention, in the steam cycle controller of the combined cycle power plant, the turbine bypass valve is provided with a function of controlling the outlet pressure of the regulator valve to be the set value, and the differential pressure condition before and after the regulator valve is added to the condition for opening the regulator valve to adjust the pressure. It is characterized in that it is provided to limit the rate of change in opening / closing of the control valve depending on the valve differential pressure.

That is, at the time of starting the combined cycle power plant, the secondary pressure of the regulator valve is controlled by the turbine bypass control to keep the outlet pressure of the regulator valve constant, and the differential pressure condition of the regulator valve is added to the opening condition of the regulator valve to open the regulator valve. Since the rate change rate limit is given as a function of the control valve differential pressure condition, even if the control valve opens when the steam condition is satisfied, the control valve differential pressure is controlled. Good control, no disturbance to drum water level.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 5, those parts which are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a detailed description thereof will be omitted. In FIG. 1, the reheat steam side will be described as a representative, but the same applies to the high pressure side.

In the turbine bypass control, a pressure detector 49 for detecting the regulator valve outlet pressure, a bias setter 50 for bypassing the regulator valve outlet pressure, and a current pressure set value for limiting the rate of change are provided. A deviation calculator 51 for calculating the deviation, a change rate limiter 54 for limiting the change rate,
Switch 40 with the control signal for controlling the pressure before or after the conventional control, which is the conventional control, in conditioner control, the condition setter 54 depending on whether the control valve opening condition meets the control valve differential pressure condition, and the control valve depending on the control valve differential pressure. Function generators 55 and 56 that limit the switching rate of switching
It consists of and. FIG. 2 shows a characteristic diagram of the present invention.

In the present invention, the low-pressure main steam pressure is set to the outlet side of the regulator valve by the switch 40 when the opening detector 36 is turned on at the time of start-up. This is the minimum pressure because the setting is made. At startup, heat generation from the exhaust gas of the gas turbine causes steam generation and pressure increase. Since the low-pressure main steam pressure has not reached this pressure setting value, the deviation calculator 46
And the control output calculated by the proportional-plus-integral-differentiator 47 becomes negative, the turbine bypass valve remains fully closed, and the pressure rises according to the heat input from the gas turbine 1.

On the high pressure side, the high pressure regulator valve 14 opens, so the regulator valve outlet pressure gradually rises. When the control valve outlet pressure exceeds the minimum pressure setting value, the set value for reheat turbine bypass control is set to a value biased to the control valve outlet pressure.

When the low-pressure main steam pressure reaches this pressure setting value, in the reheat turbine bypass pressure control, the control output obtained by the deviation calculation and the proportional-plus-integral-derivative calculation becomes positive, the turbine bypass valve is opened, and the pressure is adjusted by the regulator valve outlet pressure. Hold at a set value. When the steam pressure, temperature, and flow rate increase, the control valve opening condition is satisfied, and the control valve differential pressure condition is satisfied, the reheat control valve starts to open at a rate of change determined by a function of the control valve differential pressure. At this time, the rate of change of the control valve opening / closing changes according to the differential pressure of the control valve.Therefore, if the pressure difference is large, the rate of change is low.If the pressure difference is small, the rate of change is large. Start to run.

When the control valve 15 is opened, the opening switch 36 is activated to switch to the tracking circuit side 37-39. The tracking circuit takes in the regulator valve inlet pressure at this time,
The bias calculator 37 applies a bias to limit the rate of change of the pressure set value, so the deviation calculator 38 for calculating the deviation between the set value and the main steam pressure, the upper and lower limit limiter 39, and this deviation signal are set signals. The pressure is set by the integrator 41. In this way, the main steam pressure set value is tracked to the main steam pressure and gradually raised to the rated pressure.

As described above, since the reheat turbine bypass control controls the control valve outlet pressure, even if the control valve starts to open under turbine bypass steam conditions, the control valve differential pressure is controlled and the control valve is opened. However, a large amount of steam does not flow in, and the drum water level does not change suddenly. Further, the rate of change in opening and closing the regulator valve is also a rate of change determined by a function based on the differential pressure of the regulator valve, so there is no sudden opening. In this way, since the control of the control valve and the turbine bypass valve can be coordinated well, the problems in the conventional control can be solved. Another embodiment of the present invention will be described below with reference to FIG. Here, the reheat steam side will be described as a representative, but the same applies to the high pressure side.

A limiter 63 for limiting the upper and lower limits of the outlet pressure of the regulator valve
Is provided with a deviation calculator 53 for calculating a deviation from the pressure at the inlet and outlet of the regulator valve, and a differential pressure setting device for setting the difference pressure.
57 and the deviation calculator 58 perform deviation calculation, and provide a calculator 59 that performs proportional-plus-integral-derivative calculation on this deviation signal. The function calculator 64 is applied to this signal for matching with the conventional inlet pressure control, and it is started. It is composed of a switching device 60 that sometimes performs differential pressure control and normally performs pressure control.

At the time of startup, heat generation from the exhaust gas of the gas turbine causes steam generation and pressure increase. This control is the differential pressure control of the regulating valve at startup, but the secondary pressure of the regulating valve is set to the minimum pressure set value determined by the transmitter 43, the pressure setter 44, and the transmitter 45 when the starting condition is satisfied. It is restricted by. Since the low-pressure main steam pressure has not reached this pressure setting value, the control output calculated by the deviation calculator 58 and the proportional-plus-integral differentiator 59 becomes negative, the turbine bypass valve remains fully closed, and the pressure from the gas turbine is Increases with heat input.

Since the high pressure control valve opens, the control valve outlet pressure gradually rises. When the outlet pressure of the regulator valve exceeds the minimum pressure set value, the differential pressure of the reheat turbine bypass control starts to go positive. When the low pressure main steam pressure reaches this pressure setting value,
In the reheat turbine bypass differential pressure control, the deviation calculator 58
And the control output calculated by the proportional-plus-integral-differentiator 59 becomes positive, the turbine bypass valve is opened, and the differential pressure of the regulating valve is held at the set value. When the steam pressure, temperature, and flow rate increase and the control valve opening condition is satisfied and the control valve differential pressure condition is satisfied, the reheat control valve starts to open at a constant rate of change, and steam starts to flow to the low-pressure steam turbine side. When the regulator valve 15 is opened, the opening switch 36 operates and the tracking circuit side 37-39 is selected. The tracking circuit takes in the regulator inlet pressure at this time and applies a bias with the bias calculator 37 to limit the rate of change of the pressure set value.Therefore, the deviation calculator 38 and the deviation calculator 38, which calculates the deviation between the set value and the main steam pressure, are used. The lower limit limiter 39 and the integrator 41 using this deviation signal as a setting signal provide a pressure set value.
In this way, the main steam pressure set value is tracked to the main steam pressure and gradually raised to the rated pressure.

Since the reheat turbine bypass control controls the control valve differential pressure in this way, the control valve differential pressure is controlled even if the control valve starts to open under turbine bypass steam conditions.
Even if the regulator valve is opened, a large amount of steam does not flow in,
The drum water level does not change suddenly. In this way, since the control of the control valve and the turbine bypass valve can be coordinated well, the problems in the conventional control can be solved.

[0033]

As described above, according to the present invention,
A function to control the outlet pressure of the control valve to the turbine bypass valve in the steam cycle control device of the combined cycle power plant, a differential pressure condition before and after the control valve is set for the control valve opening condition, and a control valve differential pressure condition is set for the control valve opening / closing change rate limit. Since the valve differential pressure is controlled, it is possible to properly control the steam flow rate and pressure of the steam cycle main steam at the time of starting the complex power generation plant and at the time of load increase, and prevent large fluctuations in the water level of the drum.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the operation of the present invention.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram of the combined cycle power plant.

FIG. 5 is a block diagram showing a conventional example.

FIG. 6 is a characteristic diagram showing the operation of a conventional example.

[Explanation of symbols]

 1 ... Gas turbine device 2 ... HRSG 3 ... Steam turbine 4 ... Generator 5 ... High pressure superheater 6 ... Reheater 7 ... High pressure evaporator 8 ... High pressure economizer 9 ... Low pressure superheater 10 ... Low pressure evaporator 11 ... Low pressure Economizer 12 ... Condenser 13 ... Water pump 14 ... High pressure regulator 15 ... Reheat regulator 16 ... High pressure drum 17 ... Low pressure drum 18 ... High pressure turbine bypass valve 19 ... Reheat turbine bypass valve 20 ... Steam cycle controller 21 ... High pressure steam turbine 22 ... Reheat steam turbine 23 ... High pressure main steam pressure detector 24 ... High pressure main steam temperature detector 25 ... High pressure main steam flow detector 26 ... Low pressure main steam pressure detector 27 ... Low pressure main steam temperature detector Unit 28… Low-pressure main steam flow detector 29… Adjustment valve fully open setter 30… Adjustment valve fully closed setter 31… Deviation calculator 32… Adjustment valve fully open change rate limiter 33… Adjustment valve fully closed change rate limiter 34… Full open / close switch 35 ... Opening integrator 36 ... Opening detector 37 ... Set value Calculator 38 ... Setpoint deviation calculator 39 ... Setpoint change rate limiter 40 ... Setpoint changer 41 ... Setpoint integrator 42 ... Setpoint upper / lower limiter 43 ... Transfer 44 ... Pressure setter 45 ... Transfer Unit 46 ... Set value deviation calculator 47 ... Proportional integral derivative calculator 48 ... Function calculator 49 ... Adjustment valve outlet pressure detector 50 ... Adjustment valve outlet pressure bias setter 51 ... Adjustment valve outlet pressure deviation calculator 52 ... Adjustment valve Outlet pressure change rate limiter 53 ... Adjustable valve differential pressure calculator 54 ... Adjustable valve differential pressure condition setter 55 ... Adjustable valve open / close change rate adjustable valve differential function calculator 56 ... Adjustable valve close change rate adjustable valve differential pressure Function Calculator 57… Adjustable valve differential pressure set value setter 58… Adjustable valve differential pressure deviation calculator 59… Adjustable valve differential pressure proportional integral derivative calculator 60… Adjustable valve pressure / differential pressure control switching device 61… Start condition satisfied single Shot 62… Adjustment valve open steam condition 63… Upper and lower limit limiter for outlet pressure of the adjustment valve 64… Adjustment valve differential pressure control signal function calculation vessel

Claims (2)

[Claims] 1. A steam control valve for controlling steam that flows into the steam turbine of a combined cycle power plant in which steam is generated in an exhaust heat recovery boiler to drive the steam turbine with exhaust gas that has finished working in the gas turbine. Based on the inlet pressure of the steam control valve, the opening degree of the turbine bypass valve that bypasses the steam turbine and guides steam to the condenser by opening and closing the steam control valve when the opening condition is satisfied In a steam cycle control device including a turbine bypass valve drive means for driving the turbine bypass valve to open and close so as to have a set value, an opening set value of the turbine bypass valve provided in the turbine bypass valve drive means As the opening set value compensating means that also considers the outlet pressure of the steam control valve, and the differential pressure between the inlet pressure and the outlet pressure of the steam control valve A differential pressure condition setting means that takes into account the opening condition of the steam control valve, and an opening / closing change rate difference that limits the opening / closing change rate of the steam control valve based on the differential pressure between the inlet pressure and the outlet pressure of the steam control valve. A steam cycle control device comprising a pressure function calculating means. 2. A steam control valve for controlling steam flowing into the steam turbine of a combined cycle power plant in which steam is generated in an exhaust heat recovery boiler by driving exhaust gas that has finished working in the gas turbine to drive the steam turbine. Based on the inlet pressure of the steam control valve, the opening degree of the turbine bypass valve that bypasses the steam turbine and guides steam to the condenser by opening and closing the steam control valve when the opening condition is satisfied In a steam cycle control device including a turbine bypass valve drive means for driving the turbine bypass valve to open and close so as to reach a set value, a steam control valve outlet pressure provided in the turbine bypass valve drive is input. A limiter for limiting the upper and lower limits of the difference between the output of the limiter provided in the turbine bypass valve drive means and the inlet pressure of the steam control valve. Based on the above, a calculator for calculating the turbine bypass valve opening degree, and an opening command calculated by the calculator provided at the turbine bypass valve drive means at the time of start-up is selected to normally set the inlet pressure of the steam control valve. A steam cycle control device comprising: a switching device that selects an opening degree command for opening and closing the turbine bypass valve so that the turbine bypass valve opens and closes to a set value determined based on the steam cycle control device.