JPH03215198A - Load controller for combined cycle plant - Google Patents

Abstract

PURPOSE:To improve following-up property for the AFC signal of the whole plant by setting a circuit means for applying lead signal according to the AFC signal, to input signal to a steam turbine controller. CONSTITUTION:A circuit means for applying lead signal according to frequency controlling signal(AFC signal) 3, to input signal to a steam turbine controller, is set. On the circuit means, when a plant load controller having composition so that objective load command 1 and the AFC signal 3 may be added to each other to be turned into power generation quantity command 5 is used, then the AFC signal 3 is directly used, and when the power generation quantity command 5 is directly transmitted from a central feed current command station, then by performing arithmetic on the power generation quantity command 5 with a differentiator 33, equivalent AFC signal is computed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a combined cycle plant, that is, a gas turbine power generation device that generates electricity using a gas turbine generator directly connected to a gas turbine, and an exhaust gas boiler in which the exhaust gas of the gas turbine is guided to an exhaust gas boiler. A power generation device (
The present invention relates to a load control device for a combined cycle power generation plant that combines a bottoming cycle (hereinafter referred to as a bottoming cycle).

Conventional technology Figure 3 shows a plant load control device that comprehensively controls the output of a combined cycle plant that uses one or more gas turbines, one steam turbine for the same number of exhaust gas boilers as the gas turbines, and one or more gas turbines. An example is shown below.

The target load command 1 of the plant, which is transmitted through the transmission line from the central power dispatch center, is transmitted from the central power dispatch center to the aforementioned transmission line after the load change rate is suppressed to within the allowable value by the load change rate setting device 2. A frequency control signal (hereinafter referred to as an AFC signal) 3 transmitted through a different transmission path is added by an adder 4 to obtain a power generation amount command 5. In addition, as another example, the target load command signal and the AFC signal may be added together and transmitted as the power generation amount command from the central power dispatch center.

The power generation amount command 5 is limited by a load upper/lower limit limiter 6 to within the allowable load upper/lower limits determined by the number of operating gas turbines and atmospheric temperature. The output of the upper and lower limit limiter 6 is subtracted by the power generation amount 7 of the steam turbine generator by a comparator 8, and becomes a gas turbine load request command 9. The gas turbine load request command 9 becomes an output command 11 for each gas turbine in the gas turbine load distribution limiter 10 based on the number and operating state of gas turbines in operation. The output command 11 for each gas turbine includes a rate of change limiter 12 and an output upper/lower limit limiter 13
Therefore, the rate of change in output and the upper and lower limits of the output are limited for each gas turbine, and become the input signal 14 of the gas turbine control device. This input signal 14 is used to adjust the output of the gas turbine generator by increasing or decreasing the flow rate of fuel supplied to the gas turbine.

On the other hand, in order to maximize the efficiency of the bottoming cycle, steam turbines are operated by opening the steam control valve fully and swallowing the entire amount of steam generated by the exhaust gas boiler. In reality, it is possible to keep it fully open by giving a full open signal to the steam control valve control signal, but if it remains fixed at fully open, the heat input to the exhaust gas boiler will suddenly decrease in the event of an emergency stop of the gas turbine. However, if the temperature of the steam generated from the exhaust gas boiler decreases, bad steam may flow into the steam generator bin and damage the turbine. Therefore, if the main steam pressure drops below the specified value, the steam The opening degree of the control valve is reduced to suppress the drop in main steam pressure. That is, as shown in FIG. 4, a main steam pressure setting value 16 is calculated by the main steam pressure setting device 15 in accordance with the power generation command 5. This main steam pressure set value 16 is compared with the actual main steam pressure 18 in a comparator 17, and the controller 19 performs corrective action based on this deviation, and the output of the controller 19 becomes the main steam pressure control signal 20.

In this control system, the main steam pressure setting value 16, which is the output of the main steam pressure setting device 15, is set to a value that is a certain width lower than the pressure determined by the static characteristics of the bottoming cycle. The actual main steam pressure 18 is smaller than the main steam pressure set value 16, and as a result of the corrective action of the controller 19, the main steam pressure control signal 20 becomes equivalent to the steam control valve fully open.

On the other hand, when the frequency of the power system increases excessively, the comparator 23 uses the steam turbine rotation speed 21 and the rated rotation speed 22 as a backup control signal to suppress the amount of steam inflow.
Load bias 25 is applied to signal 24 proportional to the deviation compared with
A steam turbine rotational speed control signal 27 obtained by adding the following in an adder 26 is used. The main steam pressure control signal 20 and the steam turbine rotation speed control signal 27 are selected by the low value selector 28 and are used as the steam control valve control signal 29. During normal operation, the low value selector 28 selects the main steam pressure control signal 27. 20 is selected.

The AFC signal from the central power dispatch center to the steam turbine is transmitted via the plant load control device as part of the load bias 25, but as mentioned above, during normal operation, the steam control valve 30 is Because it is under steam pressure control,
It does not follow AFC signals.

When the gas turbine output fluctuates following the AFC signal, the gas turbine exhaust gas temperature also fluctuates, and the amount of steam generated from the exhaust gas boiler fluctuates according to that fluctuation, and as a result, the steam turbine generator output also changes. , Due to the large heat capacity of the exhaust gas boiler, the response time delay is large < ,A
It is not possible to respond quickly to FC signals.

Problems to be Solved by the Invention As mentioned above, in the conventional steam turbine control valve control system, the steam turbine output cannot follow sudden load change commands such as AFC signals, and as a result, only the gas turbine I had no choice but to respond to the AFC signal. As a result, the range of load fluctuations in the gas turbine becomes large, and the fuel must be adjusted significantly, which causes large fluctuations in the gas temperature at the gas turbine inlet, which increases the thermal stress generated in the gas turbine. As a plant, good followability to AFC signals could not be expected.

The present invention has been made in view of the above points, and by moving the steam control valve of the steam turbine in advance in response to a signal, it effectively utilizes the heat storage effect resulting from the large heat capacity of the exhaust gas boiler, and It is an object of the present invention to provide a combined plant load control device that reduces the fluctuation width of an input signal to a control device, suppresses changes in the gas turbine inlet gas temperature of a gas turbine, and has excellent response to an AFC signal.

Means for Solving the Problems According to the present invention, load control of a combined plant is provided with means for causing an input signal to a gas turbine control device to follow a frequency control signal of a power system transmitted from a central power dispatch center. The apparatus includes circuit means for applying a preceding signal corresponding to the frequency control signal to the input signal to the steam turbine control device, and the AF as a whole plant
The tracking performance for the C signal is improved.

According to the circuit means described above, first, as shown in FIG. 3, a plant load control device is used which has a configuration in which a target load command 1 and an AFC signal 3 are added to obtain a power generation amount command 5. In this case, the direct AFC signal 3 is used, and if the power generation amount command 5 is directly transmitted from the central power dispatch center, the equivalent AF signal is obtained by performing a differential operation on the power generation amount command 5.
Calculate the C signal. If the deviation between the main steam pressure 18 and the main steam pressure set value l6 is within a certain range, this AFC signal is applied to the steam turbine steam control valve 30 to cause the steam turbine output to follow the AFC signal.

According to another embodiment, when the steam turbine rotation speed control signal 27 is within a specified value, the above-mentioned AFC signal or an equivalent AFC signal is superimposed on the steam turbine rotation speed control signal to control the steam turbine. Follows the AFC signal.

In the latter embodiment, the steam turbine control device has an effect on both the speed regulating function and the following function for the AFC signal, and it is possible to make the steam turbine follow even frequency fluctuations in the power system with a shorter period than the AFC signal. It is a feature.

On the other hand, in the former embodiment, the A
Although the steam turbine is made to follow the FC signal, it is not made to follow the short-cycle frequency fluctuations of the power system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to FIGS. 1 and 2. In addition, in Figures 1 and 2, the third
The same parts as those shown in the figures and FIG. 4 are given the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 shows a first embodiment of a plant load control device according to the present invention. The configuration of the control circuit means for proactively moving the governor of the steam turbine is as follows.

A function generator 31 that calculates a standard steam control valve opening command from the power generation command 5, a differentiator 33 that generates an equivalent AFC signal by differentially calculating the power generation command 5, and corresponds to the output of this differentiator 33. a function generator 34 that generates a steam control valve control signal, a rate of change limiter 35 that limits the rate of change of the steam control valve control signal that is the output signal of the function generator 34, a function generator 31, and a rate of change limiter An adder 36 that adds the outputs of each of the devices 35, and a switch 37 between the pressure control circuit and the frequency control circuit? .

If the AFC signal is transmitted from the central power dispatch center through a transmission path different from the plant target load command, the differentiator 3
It is also possible to delete 3 and input the AFC command signal directly to the function generator 34. The operation of this circuit means is as follows.

The function generator 31 is set so that the steam turbine steam control valve 3o is not fully open, but rather is in a somewhat closed state, in response to the rated power generation command 5.

If the steam regulator valve 30 is throttled in this way, a throttle pressure loss will occur and the efficiency of the bottoming cycle will decrease slightly, but on the other hand, the pressure accumulation effect of the exhaust gas boiler will increase, and if the steam regulator valve 30 is suddenly opened, It becomes possible to temporarily increase the flow rate of steam flowing into the steam turbine, and the ability to follow the AFC signal is improved. Therefore, the function generator 31
should be set in consideration of the balance between a decrease in bottoming cycle efficiency and an increase in pressure accumulation effect.

An equivalent AFC signal can be calculated by differentially calculating the power generation amount command 5 using the differential calculator 33. From this equivalent AFC signal, the function generator 34 calculates a signal equivalent to the opening command of the steam control valve corresponding to the AFC signal,
Further, the rate of change limiter 35 suppresses the rate of change to within a rate that can be followed by the control valve.

By using the signal obtained by adding the output of the function generator 31 and the output of the rate of change limiter 35 by the adder 36 as the main steam pressure control signal 20, it is possible to adjust the output of the steam turbine according to the AFC signal. becomes.

When the output of the adder 36 is directly input to the low value selector 2B,
Since the main steam pressure will be in an uncontrolled state, a circuit is added that performs a pullback operation if the deviation between the main steam pressure and the main steam pressure setting exceeds an allowable value. That is, when the main steam pressure deviation, which is the output of the comparator 17, exceeds the allowable value, the switch 37 is switched back to the main steam pressure controller 19 side to prevent the pressure deviation from expanding beyond the allowable value. .

A second embodiment is shown in FIG. Components with the same reference numerals as in FIG. 1 have the same functions. In this example, an AFC signal is applied to the steam turbine rotation speed control signal, and as in the first embodiment,
In addition to making the steam turbine output follow the AFC signal transmitted from the central power dispatch center, it is also possible to adjust for shorter-cycle frequency fluctuations in the power system (so-called governor-free operation), which are detected as changes in the rotation speed of the steam turbine. It is said that In this example, if the main steam pressure deviation does not exceed the allowable value, the steam turbine rotation speed control signal 2 is given priority.
A dead zone 38 is provided in the main steam pressure deviation so that the side 7 is selected as the steam control valve control signal 29, so that the controller 19 does not take corrective action for deviations within the permissible value.

Effects of the Invention According to the present invention, AFC can be applied not only to gas turbines but also to steam turbine control valves that conventionally maintain a fully open state and do not follow the AFC signal.
By having a circuit means for following the signal, the followability of the entire plant to the AFC signal is improved, and
When achieving the same AFC followability in the entire plant, the fluctuation range required of the gas turbine is relatively smaller due to the steam turbine tracking, and the fluctuation range of the gas turbine inlet gas temperature of the gas turbine, as well as the gas This has the effect of reducing the fluctuation range of thermal stress generated in the turbine, and extending the life of the gas turbine.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the load control device for a combined cycle plant according to the present invention, FIG. 2 is a block diagram showing a second embodiment of the device according to the present invention, and FIG. 3 is a block diagram showing a second embodiment of the load control device for a combined cycle plant according to the present invention. FIG. 4 is a block diagram showing a conventional steam turbine control device. 1. Plant target load command, 2. Load change rate setter, 3. Frequency control signal (AFC signal), 4. Adder, 5. Power generation amount command, 6. Upper and lower limit limiter. 7...
Steam turbine generator power generation amount, 8... Comparator, 9... Gas turbine load request command, 10... Gas turbine load distribution limiter, l1... Output command for each gas turbine, 12...
- Rate of change limiter, 13... Output upper and lower limit limiter, 14...
Input signals to the gas turbine control device, ] 5. Main steam pressure setter, 16. Main steam pressure set value, 17. Comparator, 18. Main steam pressure, 19. Controller, 20.
・Main steam pressure control signal, 21...Steam turbine rotation speed,
22... Rated speed, 23... Comparator, 24... Signal proportional to deviation, 25... Load bias, 26... Adder, 27... Steam turbine rotation speed control signal, 28... Low value selection. device, 29...steam control valve control signal, 30...steam control valve, 31...function generator, 33...differentiator, 34...
Function generator, 35... Rate of change limiter, 36... Adder,
Fig. 1 Fig. 2 Fig. 3 Fig. ``Risk''.

Claims (1)

[Claims] In a combined cycle power generation plant that combines a gas turbine power generation device and a steam turbine power generation device, means for causing an input signal to the gas turbine control device to follow a frequency control signal of a power system transmitted from a central power dispatch center. A load control device for a combined cycle plant, comprising circuit means for applying a preceding signal corresponding to the frequency control signal to an input signal to a steam turbine control device.