JPH041175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas temperature control device for a gas turbine, and more particularly, to a gas turbine exhaust temperature control device suitable for suppressing the rate of change in exhaust gas temperature at startup of a gas turbine to below a certain value. Regarding.

FIG. 1 shows an example of the equipment configuration of a gas turbine power plant. In the figure, 1 is a compressor, 2 is a combustor, 3 is a turbine, 4 is a generator, 5 is a breaker,
6 is a system, 7 is a fuel adjustment valve, and 8 is a fuel control device.

The air compressed by the compressor 1 is mixed with fuel supplied through the fuel adjustment valve 7 in the combustor 2, and is heated by combustion to become a high-temperature gas. This gas is sent to turbine 3 to perform work.
The generator 4 is driven to generate electric power. The generated power is transmitted to the power grid 6 via the power cutter 5.

The fuel adjustment valve 7 controls the amount of fuel flowing into the combustor 2 based on the output signal of the fuel control device 8 .

FIG. 2 shows a block diagram of the fuel control device 8.
As can be easily seen from this figure, the fuel control system of the gas turbine consists of a startup control system 9, a speed/load control system 10, an acceleration control system 11, and a temperature control system 1.
It can be divided into 2.

The startup control system 9 controls the flow rate of fuel flowing into the combustor 2 in accordance with a predetermined startup program signal at the time of starting the gas turbine, and starts the gas turbine 3 up to the rated speed.

The speed/load control system 10 controls the speed and load after the gas turbine 3 reaches its rated speed.

The acceleration control system 11 controls the turbine acceleration at startup so that it does not exceed a predetermined value.

The temperature control system 12 is provided to manage the life of the high-temperature section of the turbine 3, and at startup, the exhaust temperature is adjusted to a pre-calculated and set temperature set value as a function of time based on the planned temperature increase rate. As a target, control is performed so as not to exceed this value, and on the other hand, during load exercise, control is performed so as not to exceed a predetermined value (usually a fixed value).

The switching gate 13 connects the four control systems 9 and 1 described above.
From among the fuel control signals generated at 0, 11, and 12, the minimum fuel signal is selected depending on the operating state of the turbine.

By the way, the conventional temperature setting of the temperature control system 12 at the time of starting the gas turbine was a program signal as shown in FIG. In the figure, the horizontal axis shows time and the vertical axis shows the exhaust temperature set value.

As can be seen from Figure 3, after the gas turbine ignites,
After the warm-up time has elapsed, the exhaust temperature set value range is increased at a constant rate, and after reaching the rated speed at time T1, this is held at a predetermined fixed value.

The reason for suppressing the rate of temperature rise in this way is to suppress thermal stress due to thermal expansion of the turbine metal. In other words, thermal stress is generated by the difference in thermal expansion between the high-temperature and low-temperature parts of the turbine metal, so in order to suppress thermal stress below a specified value, the temperature rise rate must be kept below a predetermined value. Must be.

In conventional control systems, when the temperature is controlled by acceleration control at startup, once the temperature drops for some reason, when the control switches from that state to temperature control again, the temperature change rate is The disadvantage was that the temperature rise rate could exceed the specified temperature increase rate.

This situation is shown in FIG. In this figure, the horizontal axis is time and the vertical axis is exhaust temperature. Further, the solid line shows an exhaust temperature setting curve, and the dotted line shows an example of a change in the actual exhaust temperature Tx. It is clear from the figure that
Also, as mentioned above, the exhaust temperature set point increases according to the program (in this example, with a constant slope a ₁ ) as a function of time, independent of the actual exhaust temperature.

As can be seen from FIG. 4, until the turbine reaches the rated speed at time T1, actual fuel control is performed by temperature control as in the time periods indicated by symbols t1 and t2, and This may be performed by acceleration control as in the time periods indicated by symbols t3 and t4.

Then, when the output of the acceleration control system 11 is selected as the fuel control signal and actual fuel control is performed by acceleration control, if the acceleration becomes excessive due to a decrease in load, etc. When the fuel control signal becomes smaller, the supplied fuel decreases. As a result, the acceleration decreases and approaches the set value, and the actual exhaust gas temperature may drop below the set value.

In such a state, when the load increases again and the output of the acceleration control system 11 becomes larger than that of the temperature control system 12, the output of the temperature control system 12 is selected by the switching gate 13. Therefore, the output of the temperature control system 12 becomes the fuel control signal. In other words, acceleration control is switched to temperature control.

However, as can be seen from Figure 4, the exhaust temperature set value is set as a function of time, so
It is possible that the actual exhaust gas temperature Tx at the time of switching is low and the temperature deviation from the exhaust temperature set value becomes very large. Then, exhaust temperature control is performed based on the temperature deviation, and the actual exhaust temperature Tx
The rate of change of is typically not monitored. Therefore, the actual temperature change rate a2 of the exhaust gas temperature Tx at this time is greater than the predetermined temperature gradient a1.

An object of the present invention is to improve the above-mentioned drawbacks, and to improve the actual performance even when fuel control is switched to temperature control while the exhaust temperature has fallen below its set value during acceleration control at gas turbine startup. An object of the present invention is to provide a gas turbine exhaust gas temperature control device that can control the temperature change rate of a gas turbine so that it does not exceed a specified value.

In order to achieve the above object, the present invention controls the rate of change of the exhaust temperature itself until the gas turbine reaches the rated speed, and then controls the absolute value of the exhaust temperature after the gas turbine reaches the rated speed. I have to.

The present invention will be explained in detail below with reference to the drawings.

FIG. 5 is a block diagram of one embodiment of the present invention. In the figure, 14 and 17 are velocity type proportional integral calculators, 15 is a differentiator, 16 is a transfer switch, 18 is an analog switch, 19 is an integrator,
20 and 21 are subtracters.

As one input to the subtractor 20, a temperature change rate set value at gas turbine start-up is provided. The above-mentioned temperature change rate set value at gas turbine startup defines the temperature change rate itself, and is, for example, 25
It is a value like °C/Sec.

The actual exhaust gas temperature Tx is usually the average value or median of the values detected by a plurality of thermocouples, and the differentiator 15 determines the actual temperature change rate. The control deviation of this temperature change rate is determined by the subtractor 20, and is subjected to a proportional integral calculation by the speed type proportional integral calculating unit 14.

Until the gas turbine reaches the rated speed, the analog switch 18 selects the output of the speed type proportional integral calculator 14 and supplies it to the integrator 19 under the control of the signal 14HS. The output of the integrator 19 is supplied as a fuel control signal from the temperature control system 12 to a switching gate 13 for minimum signal selection.

Therefore, until the gas turbine reaches the rated speed at time T1, the fuel control signal from the temperature control system 12 is selected as the actual fuel control signal by the switching gate 13, and the temperature control mode is entered. At this time, fuel control is performed so that the rate of change in exhaust gas temperature Tx does not exceed the set value.

As a result, even when switching from acceleration control to temperature control in the process of warming up or speeding up the gas turbine, the rate of temperature change will not exceed the set value.

Temperature control after the gas turbine reaches rated speed is performed based on the absolute value of the exhaust temperature. That is, either the peak temperature set value or the base temperature set value is switched and selected by the transfer switch 16 to become the set value of the exhaust temperature. The set value is input to the subtracter 21 together with the actual exhaust gas temperature Tx, and is used for the same fuel control as described above.

The base and peak temperature set values are determined in consideration of the lifespan of the high temperature section of the gas turbine, and are usually a function of compressor outlet air pressure or fuel flow rate. Gas turbines are usually
Operates at base temperature setting.

On the other hand, if for some reason a higher output is required despite the increased lifetime consumption of the high temperature section of the gas turbine, the operator may decide to set a higher peak temperature. can be switched to In this case, the control deviation of the exhaust temperature is also
Proportional and integral calculations are performed by the velocity type proportional and integral calculation unit 17.

When the gas turbine reaches its rated speed, the analog switch 18 uses its signal 14HS to
The output of the velocity type proportional integral calculator is switched from the 14 side to the 17 side, that is, from temperature change rate calculation to temperature absolute value calculation. The output of the analog switch 18 passes through an integrator 19 and becomes a fuel control signal for the temperature control system.

Since the amount switched by the analog switch 18 is the output of the velocity type proportional integrator 14 or 17, as described above, the output of the integrator 19 is switched smoothly without a bump, as will be described later.

In the present invention, even if the output of the speed type proportional integrator is switched from the 14 side to the 17 side at the rated speed signal 14HS, no problem occurs for the following reason.

The actual fluctuation curve of the exhaust gas temperature Tx at the time of startup of a typical gas turbine is as shown by the dotted line in FIG. As shown in this figure, the exhaust temperature
As the speed of the gas turbine increases, Tx once reaches a peak value before time T1 when the rated speed is reached, and then decreases. This is because compressor air flow increases as speed increases and efficiency improves. In this way, at a time before the turbine reaches rated speed, the actual exhaust temperature
As Tx falls, its rate of temperature change decreases and becomes negative. Therefore, the output of the velocity type proportional integrator 14 increases, and the integrator 19 tends to become saturated in the direction of increasing fuel. Of course, at this time, this signal is not selected by the switching gate 13 (see FIG. 2) located after the integrator 19.

At this time, the output of the speed type proportional integral calculator 17 on the temperature control system side is also transferred to the transfer switch 1.
Since the actual exhaust gas temperature Tx is lower than the set value selected in step 6, a signal is issued to increase the temperature. That is, in any case, the output of the exhaust temperature control system at the rated speed is not a signal of such low value as to be selected by the switching gate 13.

Therefore, even if the operating mode of the exhaust temperature control system is switched from temperature change rate control to temperature absolute value control when the rated speed is reached, there will be no effect on the gas turbine.

FIG. 7 shows the control function block used in this embodiment, its inputs and outputs, and the contents of its calculations will be described below.

(1) Differential Y=(d/dt)X (2) Integral Y=Y+X (3) Velocity type proportional integral Y=C ₁ (X _o −X _o-1 )+(Ts/T)X Here, C ₁ is _proportional gain _Ts is sampling period _T is integration _time When SW=1...Y switches from X ₂ to X ₁ at a predetermined rate of change.

(5) Analog switch When 14HS=0...Outputs Y=X ₂ When 14HS=1...Outputs Y=X ₁ As is clear from the above explanation, according to the present invention, the heating at the time of starting the gas turbine is The rate of temperature change during the engine and speed-up process can always be kept below a predetermined value.

In other embodiments of the invention, analog switch 18 may be replaced with a low value priority circuit. This embodiment is applicable when exhaust temperature change rate control is required even after the turbine reaches its rated speed. That is, by using the low value priority circuit, both the temperature change rate control and the constant exhaust temperature control can be operated at all times, and the gas turbine can be controlled in a control mode that outputs a lower fuel control signal.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the overall configuration of a gas turbine power plant, Fig. 2 is a schematic block diagram of the gas turbine fuel control system, Fig. 3 is a diagram showing an example of temperature control settings using conventional program control, Fig. 4 is a diagram for explaining the problems of conventional program signal control, Fig. 5 is a block diagram showing an embodiment of the present invention, Fig. 6 is a diagram showing an example of starting characteristics of a gas turbine, and Fig. 7 FIG. 2 is a diagram for explaining a control function block used in the present invention. 1...Compressor, 2...Combustor, 3...Gas turbine, 4...Generator, 5...Shield breaker, 6...System bus, 7...Fuel adjustment valve, 8...Fuel control Device, 9...Start control system, 10...Speed/load control system, 11...Acceleration control system, 12...Temperature control system, 13...Switching gate, 14...Speed type proportional integrator, 15... Differentiator, 16...transfer
Switch, 17... Speed type proportional integrator, 18...
Analog switch, 19...integrator.

Claims (1)

[Scope of Claims] 1. Control signals from a startup control system, a speed/load control system, an acceleration control system, a temperature control system, and each of the above control systems are input, and the optimum signal according to the turbine operating state is input. A gas turbine exhaust temperature control device comprising: a switching gate for selecting and outputting as a fuel control signal, the temperature control system comprising: exhaust temperature change rate setting means for setting a reference value for an exhaust temperature change rate; a rate-of-change detection means for detecting an actual rate of change in exhaust gas temperature; a rate-of-change deviation detection means for detecting a deviation of the actual rate of change in the exhaust gas temperature from a set value for the rate of change in the exhaust temperature; an exhaust temperature change rate control system that calculates a first fuel control signal; an exhaust temperature setting unit that sets a reference value for the exhaust temperature; and a temperature deviation detection unit that detects a deviation of the exhaust temperature from the exhaust temperature set value. an exhaust temperature absolute value control system that calculates a second fuel control signal based on the temperature deviation; and selecting one of the first and second fuel control signals and using it as a control signal for the temperature control system. 1. A gas turbine exhaust temperature control device comprising: switching means for outputting an output. 2. The gas turbine exhaust according to claim 1, wherein the switching means switches from the first fuel control signal to the second fuel control signal when the turbine reaches the rated speed. Temperature control device. 3. The gas turbine exhaust temperature control device according to claim 1, wherein the switching means is a low value priority circuit.