JPS58160516A - Control device for gas turbine exhaust temperature - Google Patents

Abstract

PURPOSE:To restrain thermal stress due to the thermal expansion of turbine metals, by directly controlling the change rate of exhaust temperature until the speed of a gas turbine reaches a rated speed so that the change rate of exhaust temperature upon starting is surely maintained below a set value. CONSTITUTION:A set value of the change rate of temperature which is delivered to an arithmetic unit 20 is compared with an actual exhaust temperature Tx obtained from a differentiator 15, in a subtractor 20 upon the starting of a turbine, and therefore, an integration operating unit 14 carries out proportional integration for delivering a fuel control signal to the turbine through a switch 18 and an integrator 19. Accordingly, when the speed of the turbine reaches a rated speed, either a peak temperature set value or a base temperature set value, which are selected and changed-over by a switch 16, is compared with the exhaust temperature Tx at 21, and is compared and integrated at 17. Thus, the fuel control signal is delivered to the turbine through the switch 18 and the integrator 19 by means of a change-over switch 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust temperature control device for a gas turbine.
The present invention relates to a gas turbine exhaust gas temperature control device suitable for suppressing the rate of change in exhaust gas temperature at a constant value or less when starting a gas turbine.

FIG. 1 Iζ shows an example of the construction of a gas turbine power plant. In the figure, l is the compressor, 2 is the combustor, 3 is the turbine, 4 is the generator, 5 is the breaker', 6 is the system, and 7 is the fuel tank.
I41iII valve regulator, 8 is a fuel control device.

The air compressed by compression 41 is burned l! At step 2, the gas is mixed with the fuel supplied through the fuel regulating valve 7 and heated by combustion to become a high-temperature gas. This gas is sent to the turbine 3 to perform work and drive the generator 4 to generate electric power. The generated power passes through 5 circuit breakers and is transferred to grid 6.
Power is transmitted to

The fuel adjustment valve 7 controls the fuel noise produced by the combustor 2Kf1 by the output signal of the fuel control device 8. FIG. 2 shows a block diagram of the fuel control button 1.

As you can see from this figure, the fuel control system of the gas turbine is divided into two main parts: the startup control system 9, and the load/load control system 1.
0. Acceleration control 411. It is divided into a temperature control system 12.

The start-up control system 9 controls the amount of fuel fsflt flowing into the combustion iI2 in accordance with a predetermined tin program signal at the time of starting the gas turbine 3 to start up the gas turbine 3 to the rated speed.

The continuous t/load control system IO controls the speed and load after the gas turbine 3 becomes rated and stabilized.

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 controls the temperature change rate so that it does not exceed a predetermined value at startup, while during load operation,
This controls the combustion temperature so that it does not exceed a predetermined value.

The switching gate 13 has the above-mentioned four control systems 9, 10° 11
, 12, a suitable signal is selected depending on the operating state of the turbine.

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

As can be seen from FIG. 3, after the gas turbine has been ignited and a warm-up time has elapsed, the exhaust AT setting value is increased at a constant rate of change.

The reason for suppressing the rate of temperature change 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 keep the thermal stress below the specified value, the temperature increase rate must be kept below the predetermined value. Must be.

Conventional control systems have the disadvantage that, when the temperature is once controlled by acceleration control at startup, the temperature change rate may exceed the predetermined temperature change rate when returning to temperature control. Ta.

Figure 4 shows the condition of Jin. In this figure, the horizontal axis is time and the vertical axis is exhaust temperature. Moreover, the solid line shows an exhaust gas temperature setting curve, and the dotted line shows an example of an actual change in exhaust gas temperature.

As previously mentioned, the exhaust temperature setpoint increases programmatically as a function of time.

Therefore, after the exhaust gas temperature tlTx once falls below the set value, the rate of change when TI rises again is not controlled at all. Therefore, the actual temperature change rate a1 of the exhaust gas temperature Tx at this time is greater than the predetermined temperature change rate a1.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas turbine exhaust gas temperature control device that can overcome the above-mentioned drawbacks and can control the temperature change rate at the time of gas turbine startup so that it is always below a predetermined value.

In order to achieve the above object, the present invention controls the rate of change in 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 described in detail below with reference to the drawings.

FIG. 5 is a block diagram of one embodiment of the present invention.

In the figure, 14.17 is a velocity type proportional integral calculator, 15
is a differentiator, 16 is a transfer switch, 18 is an analog switch, 19 is an integrator, and 20.21 is a subtracter.

As a single input to the subtractor 20, a temperature change rate set value at gas turbine start-up is supplied. The temperature change rate set value at the time of starting the gas turbine defines the temperature change rate itself, and is, for example, a value such as 25'C/8ec.

The actual exhaust gas temperature Tx is usually the average value or median of the values detected by a plurality of thermocouples, and the actual temperature change rate is determined by differentiation @15.

The control deviation of this temperature change rate is obtained by subtraction 1120, and proportional integral calculation is performed by the speed type proportional integral calculation unit 14.

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 setting value or the base temperature setting value is switched and selected by the transfer switch 16 to become the exhaust temperature setting value.

The set value is input to the subtracter 21 along with the actual exhaust gas temperature Tx.
It is used for the same type of fuel 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 typically operated at a base temperature setting.

On the other hand, if for some reason a larger output is required despite the increased lifetime consumption of the hot section of the gas turbine, the operator may decide to increase the peak temperature setting at a higher temperature setting. You can switch to settings. In this case, the control deviation of the exhaust gas temperature is also subjected to proportional integral calculation by the velocity type proportional integral calculation 17.

When the analog switch 1841 and the gas turbine reach the rated speed, the signal 14H8 causes the output of the speed type proportional integral calculator to switch from the 14 side to the 17 side, that is, from speed change rate calculation to temperature absolute value calculation. The output of the analog switch 1B passes through an integrator 19' and becomes a fuel control signal from the temperature control system.

The amount to be changed by the analog switch 18 is as stated above.
Since it is the output of velocity type proportional integral @14 or 4117,
The output of the integrator 119 switches smoothly without a bump.

Also, even if the output of the speed type proportional integrator is switched from 1411 to 17@ with the rating 1 & signal 141 (8), the problem is 4
The reason why this is not the case is as follows.

A typical gas turbine startup curve is shown by the dotted line in FIG. As shown in this figure, the exhaust temperature gTx
once reaches a peak value as the speed of the gas turbine increases, and then decreases. The stiffness is due to the fact that as the compressor air flow rate increases as the speed increases, the efficiency improves.

Thus, at the rated speed of the turbine, as the actual exhaust temperature Tx decreases, the 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 be 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.

Also, at this time, the speed type proportional integral calculation 41 on the temperature control system side
Since the actual temperature TI is lower than the set value selected by the transfer switch 16, the output of the switch 7 also outputs a signal in the direction of increasing the temperature. In other words, in any case, the output of the exhaust temperature control system at the rated speed is
The signal is not low enough to be selected by 3.

Therefore, when the rated speed is reached, even if the operation mode of the exhaust temperature side @ thread is switched from temperature change rate control to temperature absolute value control, no change will be made to the gas turbine.

Figure 7 shows the book l! The control function block used in the example,
The inputs and outputs are shown, and the contents of the calculations are described below.

(1) Differentiation (2) Integration YgY+x (3) Velocity type proportional integration Here, C1 is the proportional gain T is the sampling period T is the integration time 4 is the current input Xn-1 is the input of l sampling - (4) When the transfer switch SW is O, -Y changes from Xi to X2, and when 5W-1, Y changes from X2 to Xl at a predetermined rate of change.

(5) When analog switch 5W-O is on...When Y-X2 is output 5W-1...Y-XI is output As is clear from the above explanation, according to the present invention, when starting the gas turbine The temperature change rate can always be kept below a predetermined value, and the control device can perform bumpless switching with a simple configuration.

In other embodiments of the invention, analog switch 18 may be replaced with a low value priority circuit.

This embodiment is also applicable to cases where the exhaust gas temperature does not decrease even when the rated speed is reached.

That is, the gas turbine can be controlled in a control mode that outputs a low fuel control signal out of either temperature change rate control or constant exhaust temperature control.

[Brief explanation of the drawing]

Is1 diagram (j) A block diagram showing the overall configuration of the gas turbine power plant; Figure 2 is a schematic block diagram of the fuel control system of the gas turbine; Fig. 4 is a diagram for explaining the problems of conventional program signal control, Fig. 5s is a block diagram showing an embodiment of the present invention, Fig. ia6 is a diagram showing an example of starting characteristics of a gas turbine, and Fig. 7 is a diagram showing an example of starting characteristics of a gas turbine. The figure is a diagram for explaining the control function blocks used in the present invention. l... Compressor, 2... Fuel ms, a... Gas turbine, 4... Generator, 5... ... Breaker, 6... System bus, 7... Fuel adjustment valve, 8... Fuel control device, 9
...Start control system, 10...Speed f/load control system, 11
...Acceleration control system, 12...@degree control system, 13...
・Switching gate, 14... Speed type proportional integrator, 15...
・Differentiator, 16...Transfer switch, 17・
...Velocity type proportional integrator, 18...Analog switch,
19...Integrator agent attorney Hiraki Michihito 6 people eNIkrr,, JBλ Yami Sai 4 Figure off diagram

Claims (1)

[Scope of Claims] (11) Control signal sounds are input from the startup control system, the speed/load control system, the acceleration control system, the temperature control system, and each of the control systems, and the optimal A gas turbine exhaust temperature control system comprising a switching gate that selects a signal and outputs it as a fuel control signal, the temperature control system changing the actual rate of change of the exhaust temperature to a set value of the rate of change of the exhaust temperature. The exhaust temperature change rate control system calculates the IEI fuel control signal based on the deviation from the actual exhaust temperature, and compares it with the set value at the time of loading, and calculates the second fuel control signal based on the deviation. Gas turbine exhaust temperature control characterized by comprising: an exhaust temperature control system that performs calculations; and a switching means that selects one of the first and second fuel control signals and outputs it as a control signal for the temperature control system. (2) The switching means switches from the first fuel control signal to the second fuel control signal when the turbine reaches the rated speed. The gas turbine exhaust temperature control device according to item 1. (3) The patented exhaust gas temperature control device, characterized in that the switching means is a low value priority @path.