JP2918743B2 - Steam cycle controller - Google Patents

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 power plant combining a gas turbine and a steam turbine.

[0002]

2. Description of the Related Art From the viewpoint of effective use of energy resources and economic efficiency, various high-efficiency power generation plants are being promoted. Combined cycle power plants are one of them, and are playing a central role in thermal power plants.

FIG. 4 is a configuration diagram showing an example of the configuration of a combined cycle power plant. This power plant includes a gas turbine 1, an HRSG 2, a steam turbine 3, and a generator 4. This is a combined power plant that not only generates power with the gas turbine 1 but also guides the combustion exhaust gas to the HRSG 2, generates steam by recovering heat with the HRSG 2, drives the steam turbine 3, and generates power with the generator 4. . In the gas turbine 1, the combustion air is pressurized to burn fuel, and the gas turbine is turned to perform work. Thereafter, the high temperature combustion exhaust gas is led to HRSG2.

The HRSG 2 comprises, 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. These heat exchangers exchange heat with gas turbine exhaust gas to generate steam.

[0005] The steam generated by the high-pressure drum 16 is sent to the high-pressure superheater 5, where it becomes superheated steam and becomes high-pressure steam turbine 21.
And drives the high-pressure steam turbine 21 to generate electricity with the generator 4. The steam generated by the low-pressure drum 17 is supplied to the low-pressure superheater 9
Where it becomes 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, sent to the reheat steam turbine 22 and generated by the power generator 4.

The steam that has worked in the reheat steam turbine 22 is:
After being condensed in the condenser 12, the water is pumped by the water supply pump 13 and 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, the fuel is superheated 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 performs heat exchange with gas turbine exhaust gas to generate high-pressure steam. With the recent improvement of gas turbine performance, the exhaust gas temperature of the gas turbine has risen,
Since the heat can be recovered by the RSG, the 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 case of a combined cycle power plant, in the case of a combined power generation plant, under the rated conditions, the throttle valve is not fully opened as in the conventional plant and the valve is fully opened. The temperature) is satisfied, the plant condition is satisfied, and the starting condition is satisfied, so that the control valve 15 opens and closes at a constant rate of change.

[0009] The equipment includes a control valve full-open setting device 29 for setting the control valve fully open and fully closed position, a control valve full-close setting device 30, a deviation calculator 31 for calculating a deviation from the current set value, and a control valve open. The opening / closing switch 34 for switching the fully open / closed state of the valve, and the open / closed switch 34 for switching the fully open / closed state of the valve, and an opening signal from these deviation signals. It comprises an opening degree integrator 35 for calculation.

In the turbine bypass control, a set value bias calculator 37 for bypassing the pressure signal from the control valve inlet pressure detector 26, a set value deviation calculator 38 for calculating a deviation from a current set value, and a set value deviation calculator 38 The set value change rate limiter 39 for limiting the change rate of the set value, the set value integrator 41 for calculating the set value from the deviation signal, the set value upper / lower limiter 42 for limiting the set value upper and lower limits, the main steam at the time of startup Transmitter 43 for setting pressure,
A pressure setting device 44 at the time of start, a transfer device 45 which keeps a set value until the regulator valve is opened to a certain degree, a deviation calculator 46 which calculates a deviation between the set value and a pressure before the regulator valve, and a calculator which performs proportional integral differentiation with this signal.
47, function calculator 4 that performs function conversion on this control signal
8, and an opening detector 36 that detects the opening and closing of the control valve and turns on at a constant opening, thereby tracking the turbine bypass control to the main steam pressure. How these controls operate at startup will be described with reference to FIG. 6, taking the reheated air side as a representative. The same applies to the high pressure side.

On the gas turbine side, the speed of the gas turbine 1 is increased by start-up control until the rotation speed N reaches the rated rotation speed at startup, and when the rotation speed reaches the rated rotation speed, load control is started. Exhaust gas flow Q
1 and the exhaust gas temperature T also increase.

Due to the startup characteristics of the combined cycle power plant, the gas turbine 1 can be started up quickly, but the HRSG on the steam cycle side
The startup is delayed due to the delay due to the heat capacity of No. 2 and the transmission delay by the duct and the 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 startup, the single shot 61 is turned on when the startup conditions are satisfied, and the main steam pressure at this time is sent by the transmitter 43, and the set pressure value is held by the setting calculator. Also, since the control valve 15 is not open, the opening detector is turned on, and when the transmitter 45 operates and starts up, this value is used as the pressure set value. Due to the heat input from the exhaust gas of the gas turbine 1, steam generation and pressure rise start. 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 integral differentiator 47 becomes negative, the turbine bypass valve remains fully closed, and the pressure becomes
Rises according to the heat input from

When the high-pressure main steam pressure P1 reaches this pressure set value, in the high-pressure turbine bypass pressure control, the control outputs calculated by the deviation calculator 46 and the proportional-integral differentiator 47 become positive, and the turbine bypass valve 19 is opened, and the pressure is increased. Is kept at the set value. Steam pressure, temperature, and flow rate increase and control valve open condition
When the condition 62 is established, the switching device 34 is set to the control valve full-open setting device 29 side, and the control valve 15 starts to open at a constant rate of change determined by the change rate limiter 32, and starts to flow steam to the steam turbine side. When the control valve 15 is opened, the opening switch 36 is activated, and is switched to the tracking circuit side 37-39. The tracking circuit takes in the control valve inlet pressure at this time, applies a bias by the bias calculator 37, and limits the rate of change of the pressure set value. Therefore, a deviation calculator 38 for calculating a deviation between the set value and the main steam pressure.
And the upper and lower limiter 39 and the integrator 41 that uses the deviation signal as a setting signal to obtain a pressure set value. In this way, the main steam pressure set value is tracked to the main steam pressure, and is gradually increased 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, P1 is the high-pressure main steam pressure, H1 is the high-pressure drum water level, and Q1 is the high-pressure drum water level. High-pressure bypass flow rate, θ2 is the reheat steam control valve opening, H2 is the low-pressure drum water level, P2 is the 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 control of the turbine bypass valve are not properly coordinated, the following problems have been encountered.

When the control valve 15 starts to open under the turbine bypass steam condition, the pressure difference before and after the control valve 15 is large. Therefore, even if the control valve 15 is slightly opened, a large amount of steam flows in and the water level of the drum 17 suddenly increases. fluctuate. In particular, at the time of start-up, since the differential pressure of the control valve 15 is large and the amount of steam inflow is large, the water level of the drum 17 rises rapidly.
And may damage the steam turbine 22.
The same applies to the high-pressure steam side, but particularly, the reheat-side steam pressure depends on the high-pressure side steam pressure. In particular, a combined cycle power plant is suitable for performing load adjustment because of its small single unit capacity and short startup time, and the startup and shutdown are frequently performed. Therefore, it is important to solve this problem. The present invention has been made in view of such a point,
It is an object of the present invention to obtain a control device which controls the main steam flow rate and pressure of a steam turbine well and does not cause disturbance to a drum water level.

[0018]

SUMMARY OF THE INVENTION A steam cycle control device according to the present invention is a steam generator for a combined cycle power plant in which exhaust gas after work in a gas turbine generates steam in an exhaust heat recovery boiler to drive the steam turbine. The opening and closing of the steam control valve that opens and closes the steam control valve when the open condition of the steam control valve that controls the steam flowing into the turbine is satisfied, and the opening degree of the turbine bypass valve that guides the steam turbine to the condenser by the steam. Turbine bypass valve driving means for opening and closing the turbine bypass valve so as to have a set value determined based on the inlet pressure of the control valve, and steam control as an opening set value of the turbine bypass valve provided in the turbine bypass valve driving means. Opening set value compensation means that also takes into account the outlet pressure of the valve, and a differential pressure that takes into account the differential pressure between the inlet pressure and the outlet pressure of the steam control valve in 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 for controlling the steam flowing into the steam turbine of the combined cycle power plant in which steam is generated by the exhaust heat recovery boiler from the exhaust gas having completed the work in the gas turbine and drives the steam turbine. The opening degree of the control valve drive means for opening and closing the steam control valve when the condition is satisfied and the opening degree of the turbine bypass valve for guiding the steam to the condenser bypassing the steam turbine are determined based on the inlet pressure of the steam control valve. Turbine bypass valve driving means for opening and closing the turbine bypass valve so as to reach a set value; a limiter provided in the turbine bypass valve driving means for inputting a steam control valve outlet pressure to limit the upper and lower limits; Means 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; The opening degree, which is provided in the valve driving means, selects the opening degree command calculated by the calculator at the time of startup, and normally drives the opening and closing of the turbine bypass valve so as to have a set value determined based on the inlet pressure of the steam control valve during normal operation. And a switch for selecting a command.

[0020]

According to the present invention, in a steam cycle control system of a combined cycle power plant, a function is provided for controlling a turbine bypass valve with a regulator valve outlet pressure as a set value. The present invention is characterized in that the rate of change of the opening and closing of the control valve is limited by the valve differential pressure.

That is, the secondary pressure of the control valve is controlled by the turbine bypass control at the start of the combined cycle power plant to keep the control valve outlet pressure constant, and the control valve opening condition is added to the control valve differential pressure condition and the control valve is opened. The rate change rate limit is given as a function by the control valve differential pressure condition, so even when the control valve is opened due to the establishment of the steam condition, the control valve control differential pressure controls the steam cycle main steam flow rate and pressure. Good control, no disturbance to drum water level.

[0022]

An embodiment of the present invention will be described below with reference to FIG. In the figure, the same parts as those in FIG. 5 are denoted by the same reference numerals, and 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 pressure at the control valve outlet, a bias setting device 50 for bypassing the pressure at the control valve outlet, and a current pressure set value for limiting the rate of change are used. A deviation calculator 51 for performing a deviation calculation, a change rate limiter 54 for performing a change rate limit,
A switching unit 40 for controlling the control pressure before and after the control valve, which is a conventional control, a condition setting unit 54 for the control valve opening condition when the control valve opening condition is satisfied, and a control valve for controlling the control valve according to the control valve differential pressure. Function generators 55 and 56 that limit the rate of change of switching
It is composed of FIG. 2 shows a characteristic diagram of the present invention.

According to the present invention, the low-pressure main steam pressure is set to the opening / closing valve outlet side by the switching device 40 at the time of start-up, and the minimum pressure set value is set in advance when the start-up condition is satisfied. Is set to this minimum pressure. During startup, steam generation and pressure rise begin due to heat input from the exhaust gas of the gas turbine. Since the low-pressure main steam pressure has not reached this pressure set value, the deviation calculator 46 is used.
The control output calculated by the proportional-integral differentiator 47 becomes negative, and the pressure increases with the heat input from the gas turbine 1 while the turbine bypass valve remains fully closed.

On the high pressure side, since the high pressure control valve 14 is opened, the control valve outlet pressure gradually increases. When the control valve outlet pressure exceeds the minimum pressure set value, the set value of the 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 set value, in the reheat turbine bypass pressure control, the control output obtained by the deviation calculation and the proportional integral differentiation calculation becomes positive, the turbine bypass valve is opened, and the pressure is adjusted by the control valve outlet pressure. Keep at a certain set value. When the steam pressure, the temperature, and the 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 rate of change determined by a function based on the control valve differential pressure. At this time, the rate of change of the opening and closing of the control valve is a rate of change based on the differential pressure of the control valve. Therefore, when the differential pressure is large, the rate of change is low, and when the differential pressure is small, the rate of change is large. Start flowing.

When the control valve 15 is opened, the opening degree switch 36 is activated, and is switched to the tracking circuit side 37-39. The tracking circuit takes in the control valve inlet pressure at this time,
In order to apply a bias by the bias calculator 37 and limit the rate of change of the pressure set value, a deviation calculator 38 for calculating a deviation between the set value and the main steam pressure, an upper / lower limiter 39, and this deviation signal as a set signal. 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 is gradually increased 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. Also, a large amount of steam does not flow in, and the drum water level does not fluctuate rapidly. Also, the rate of change at which the control valve opens and closes does not suddenly open because the rate of change is determined by a function based on the control valve differential pressure. As described above, the control of the control valve and the turbine bypass valve can be coordinated well, and the problem with the conventional control is eliminated. The following describes another embodiment of the present invention with reference to FIG. Here also, the description will be made on the reheat steam side as a representative, but the same applies on the high pressure side.

Limiter 63 for limiting upper and lower limits of the control valve outlet pressure
And a deviation calculator 53 for calculating a deviation from the control valve inlet pressure, and a differential pressure setting device for setting the differential pressure.
A deviation calculator 57 and a deviation calculator 58 perform a deviation calculation, and a calculator 59 for performing a proportional-integral-differentiation calculation on the deviation signal is provided. It is constituted by a switching device 60 that sometimes performs differential pressure control and normally performs pressure control.

During startup, steam generation and pressure rise begin due to the heat input from the exhaust gas of the gas turbine. At the time of startup, this control is a control valve differential pressure control. Is restricted by Since the low-pressure main steam pressure has not reached this pressure set value, the control output calculated by the deviation calculator 58 and the proportional-integral differentiator 59 becomes negative, the turbine bypass valve remains fully closed, and the pressure from the gas turbine is reduced. It rises with heat input.

Since the high-pressure control valve opens, the control valve outlet pressure gradually increases. When the control valve outlet pressure exceeds the minimum pressure set value, the differential pressure of the reheat turbine bypass control starts to become positive. When the low-pressure main steam pressure reaches this pressure set value,
In the reheat turbine bypass differential pressure control, the deviation calculator 58
The control output calculated by the proportional-integral differentiator 59 becomes positive, the turbine bypass valve is opened, and the control valve differential pressure is maintained at the set value. When the steam pressure, the temperature, and the 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 constant rate of change, and the steam starts flowing to the low-pressure steam turbine side. When the control valve 15 is opened, the opening switch 36 is activated, and is switched to the tracking circuit side 37-39. The tracking circuit takes in the control valve inlet pressure at this time, applies a bias by the bias calculator 37, and limits the rate of change of the pressure set value. The lower limiter 39 and the integrator 41 that uses this deviation signal as a setting signal make the pressure set value.
In this way, the main steam pressure set value is tracked to the main steam pressure, and is gradually increased to the rated pressure.

As described above, since the reheat turbine bypass control controls the differential valve differential pressure, the differential valve differential pressure is controlled even when the control valve starts to open under turbine bypass steam conditions.
Even if the control valve is opened, a large amount of steam does not flow in,
There is no sudden change in the drum water level. As described above, the control of the control valve and the turbine bypass valve can be coordinated well, and the problem with the conventional control is eliminated.

[0033]

As described above, in the present invention,
In the steam cycle control system of the combined cycle power plant, the function to control the outlet pressure of the regulator valve in the turbine bypass valve, the differential pressure condition before and after the regulator valve for the opening condition of the regulator valve, and the differential pressure condition for the regulating valve opening / closing rate limit are set. Since the valve differential pressure is controlled, the flow rate and pressure of the main steam in the steam cycle can be controlled well when the combined cycle power plant is started and when the load is increased, and large fluctuations in the water level of the drum can be prevented.

[Brief description of the 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 a combined cycle power plant.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gas turbine apparatus 2 ... HRSG 3 ... Steam turbine 4 ... Generator 5 ... High pressure super heater 6 ... Reheater 7 ... High pressure evaporator 8 ... High pressure economizer 9 ... Low pressure super heater 10 ... Low pressure evaporator 11 ... Low pressure Energy saving device 12… Condenser 13… Water pump 14… High pressure control valve 15… Reheat control valve 16… High pressure drum 17… Low pressure drum 18… High pressure turbine bypass valve 19… Reheat turbine bypass valve 20… Steam cycle control device 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 detection Unit 28… Low-pressure main steam flow detector 29… Control valve fully open setting device 30… Control valve fully closed setting device 31… Deviation calculator 32… Control valve full-open change rate limiter 33… Control valve full-close change rate limiter 34… Full open / close switch 35… Opening degree integrator 36… Opening degree detector 37… Set value Calculator 38… Set value deviation calculator 39… Set value change rate limiter 40… Set value switcher 41… Set ground integrator 42… Set value upper and lower limit limiter 43… Transmitter 44… Pressure setter 45… Transfer Unit 46… Set value deviation calculator 47… Proportional integral derivative calculator 48… Function calculator 49… Regulator valve outlet pressure detector 50… Regulator valve outlet pressure bias setter 51… Regulator valve outlet pressure deviation calculator 52… Regulator Outlet pressure change rate limiter 53 ... Deceleration valve differential pressure calculator 54 ... Deceleration valve differential pressure condition setting device 55 ... Deceleration valve differential pressure function calculator for deceleration valve opening change rate 56 ... Deceleration valve differential pressure for decrement valve closing change rate Function calculator 57… Regulating valve differential pressure set value setting device 58… Regulator valve differential pressure deviation calculator 59… Regulator valve differential pressure proportional integral derivative calculator 60… Regulator valve pressure / differential pressure control switch 61… Start-up condition single Shot 62: Control valve open steam condition 63: Upper and lower limiter for control valve outlet pressure 64 ... Control valve differential pressure control signal function calculation vessel

Claims (2)

(57) [Claims] 1. A steam control valve for controlling steam flowing into a steam turbine of a combined cycle power plant in which steam is generated by an exhaust heat recovery boiler using exhaust gas having completed work in a gas turbine and the steam turbine is driven. When the open condition is satisfied, the opening degree of the control valve drive unit that opens and closes the steam control valve and the turbine bypass valve that guides steam to the condenser by bypassing the steam turbine is based on the inlet pressure of the steam control valve. A turbine bypass valve driving means for driving the turbine bypass valve to open and close so that the turbine bypass valve opens and closes to a predetermined set value. The opening degree set value compensating means also taking into account 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 is 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 a differential pressure between an inlet pressure and an outlet pressure of the steam control valve. A steam cycle control device comprising 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 by an exhaust heat recovery boiler using exhaust gas having completed work in the gas turbine and drives the steam turbine. When the open condition is satisfied, the opening degree of the control valve drive unit that opens and closes the steam control valve and the turbine bypass valve that guides steam to the condenser by bypassing the steam turbine is based on the inlet pressure of the steam control valve. A turbine bypass valve driving means for opening and closing the turbine bypass valve so as to open and close the turbine bypass valve so as to have a predetermined set value, wherein the steam control valve outlet pressure provided in the turbine bypass valve drive is inputted. And a deviation between an output of the restrictor and an inlet pressure of the steam control valve provided in the turbine bypass valve driving means. A computing unit that computes the opening degree of the turbine bypass valve based on the opening degree command that is provided in the turbine bypass valve driving means and that is operated by the computing unit at startup and that is normally used to adjust the inlet pressure of the steam control valve. A switching device for selecting an opening command for opening and closing the turbine bypass valve so as to have a set value determined based on the steam cycle control device.