JP2960212B2 - Load control device for combined cycle power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load control device for a combined cycle power plant comprising a plurality of gas turbines and one or more steam turbines.

[0002]

2. Description of the Related Art In general, a combined cycle power plant includes a plurality of gas turbines and one or a plurality of steam turbines.

FIG. 3 shows an example of the configuration of such a combined cycle power plant and its load control device.

The high-temperature exhaust gas from the gas turbine 1 passes through an exhaust path 2 and is guided to an exhaust heat recovery boiler 3. And
The heat of the exhaust gas generates steam in the exhaust heat recovery boiler 3, supplies the steam to the steam turbine 5 through the steam pipe 4, and rotates the generator 6. The gas turbine 1
, The generator 6 and the steam turbine 5 are coaxially connected, and the generator 6 is driven by both the gas turbine 1 and the steam turbine 5. That is, the load on the generator 6 is the sum of the load on the gas turbine 1 and the load on the steam turbine 5. The load of the gas turbine 1 is controlled by a fuel control valve 7 to a combustor 8.
It is controlled by adjusting the fuel sent to. On the other hand, the load on the steam turbine 5 is determined by the temperature and amount of the exhaust gas from the gas turbine 1.

The load control of the combined cycle power plant constructed as described above is performed, for example, as follows.

As shown in FIG. 3, the load control device comprises a master control unit 9 and a sub-loop control unit 10 at two levels.

The master control unit 9 includes a master load setting unit 13
The deviation of the total load signal 15 which is the sum of the master target load signal 14 and the generator load signal 11 of each combined cycle power generation unit is output to the master load controller 16 and the sub-loop daily load signal 12 is output. By outputting to the sub-loop control unit 10, control is performed so that the value of the total load signal 15 matches the value of the master target load setting signal 14.

A sub-loop control unit 10 provided for each combined cycle power generation unit inputs a deviation between a sub-loop target load signal 12 from the master control unit 9 and a generator load signal 11 to a sub-loop load controller 17. ,
By outputting the fuel control valve operation command 18 to the fuel control valve 7, control is performed to match the value of the generator load signal 11 with the value of the sub-loop target load signal 12.

Under the control of the master control unit 9 and the plurality of sub-loop control units 10, the total load signal 15
Is controlled to the value of the master target load signal 14.

[0010]

As described above, in the combined cycle power plant, the load on the steam turbine 5 varies depending on the temperature and the amount of exhaust gas from the gas turbine 1. Since the delay of the process is large, much time is required from when the load on the gas turbine 1 increases to when the load on the steam turbine 5 increases. Therefore, the conventional load control described above has a problem that the following inconvenience occurs.

FIG. 4 shows the total load signal 15, the load 30 of the gas turbine 1, and the steam turbine 5 when the value of the master target load signal 14 is increased in the system of FIG.
3 shows how the value of the load 31 changes. Hereinafter, the rated load of the gas turbine 1 will be simplified to 50 MW, and the rated load of the steam turbine 5, that is, the load when the gas turbine 1 performs the continuous rated load operation will be simplified to 50 MW.

The master target load signal 14 is changed from 0 MW to 225
When it is increased to MW, the total load signal 15 rises following the master target load signal 14 until time a by the gas turbine 1 having a fast response.

At time a, the load 30 of the gas turbine 1 is
Reaches the rated value of 50 MW. Therefore, after time a, the load 30 of the gas turbine 1 becomes constant at 50 MW.

On the other hand, the load 3 of the steam turbine 5 having a slow response
1 continues to rise slowly after time a.

The rise of the total load signal 15 after the time a depends on the load 31 of the steam turbine 5. Therefore, after time a, the total load signal 15 cannot follow the master target load signal 14. As a result, the deviation between the master target load signal 14 in the master control unit 9 and the total load signal 15 increases to the positive side. Incidentally, the master load controller 16 incorporates an integral element. Therefore, the sub-loop target load signal 12 keeps increasing due to the integration operation.

For this reason, in FIG. 4, after the total load signal 15 reaches the master target load signal 14 at time b, the master target load signal 14 and the total load signal 15
Is a negative value, but the value of the sub-loop target load signal 12 becomes 50 MW due to the integration operation of the master load controller 16.
Therefore, the load value 30 of the gas turbine 1 does not decrease after time b. Therefore, the total load signal 1
5 continues to increase due to the increase in the load value 31 of the steam turbine 5.

Thereafter, at time c, the value of the sub-loop target load signal 12 decreases and reaches 50 MW. As a result, the load 30 of the gas turbine 1 starts to decrease, and the total load signal 1
5 is controlled to the value of the master target load signal 14. That is, after the load 30 of the gas turbine 1 reaches the rated value,
Despite the load control being disabled, the master load controller 16
Performs load control, an overshoot of the total load signal 15 shown in FIG. 4 occurs.

The present invention has been made in view of such conventional circumstances, and can prevent the occurrence of overshoot and undershoot when the total load rises and falls, thereby achieving better control than in the past. It is intended to provide a load control device for a combined cycle power plant that can perform the following.

[0019]

That is, a load control device for a combined cycle power plant according to the present invention provides a master target load signal which is a target load signal of all the total loads of a gas turbine and a steam turbine of a combined cycle power plant. A sub-loop control unit that outputs an operation command for a fuel control valve provided in each of the gas turbines, based on a deviation between a master load setter to be output, the master target load signal, and a total load signal indicating the total load. A master load controller for outputting a sub-loop target load signal, and a plurality of upper limit load detectors each receiving a load signal of each of the gas turbines and detecting whether or not the load value is an upper limit value at which the gas turbine can output. And the outputs of all of the upper limit load detectors, and the loads of all of the gas turbines become the upper limit values. And when and, the master load setter and outputs the upper limit command, a master load control upper limit logic to limit the increase in the value of the sub-loop target load signal, respectively inputted to the load signal of the gas turbine A plurality of lower load detectors for detecting whether or not the load value is a lower limit value capable of outputting the gas turbine; and manually outputting the outputs of all the lower load detectors so that the loads of all the gas turbines are lower. And a master load control lower limit logic for outputting a lower limit command to the master load setter when the value is a value to limit a decrease in the value of the sub-loop target load signal.

[0020]

In the load control device for a combined cycle power plant according to the present invention having the above-described structure, whether or not the load value has reached the upper limit value or the lower limit value for each gas turbine is determined by the upper limit load detector and the lower limit load detector. Is detected.

When the loads of all the gas turbines are at the upper limit value or the lower limit value, the upper limit command and the lower limit command are output from the master load control upper limit logic and the master load control lower limit logic, respectively. The sub-loop target load signal is controlled so as not to increase or decrease from the current value.

Therefore, when the load of all gas turbines is at the upper limit, the sub-loop target load signal is limited to the current value at the upper limit, so that overshooting when the total load rises can be prevented. When the load of the gas turbine is at the lower limit, the sub-loop target load signal is limited to the lower limit to the current value, so that undershoot at the time of a decrease in the total load can be prevented.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of a load control device for a combined cycle power plant according to the present invention will be described below with reference to an embodiment with reference to the drawings.

FIG. 1 shows a main configuration of a load control device of a combined cycle power plant according to an embodiment of the present invention. In FIG. 1, reference numeral 9a denotes a master control unit. The master control unit 9a corresponds to the master control unit 9 in the conventional load control device shown in FIG. 3, and the same parts as those in FIG. 3 are denoted by the same reference numerals.

The master control unit 9a includes a master load setting unit 13 and a master load controller 16. The master load setter 13 outputs a master target signal 14, and a deviation between the master target load signal 14 and a total load signal 15 which is the sum of the generator load signals 11 of the combined cycle power generation units is determined by the master load controller. 1
It is human-powered to 6. Then, the master load controller 16 outputs the sub-loop target load signal 12 according to these deviations.

The sub-loop target load signal 12 is shown in FIG.
Are input to the respective sub-loop control units 10, and as described above, the opening of the fuel control valve 7 is controlled by these sub-loop control units 10.

The master controller 9a further includes an upper limit load detector 40, a master load control upper limit limiting logic 41,
Further, a lower limit load detector 42 and a master load control lower limit restriction logic 43 are provided.

The load signal 44 of the gas turbine 1 of each combined cycle power generation unit is input to the upper limit load detector 40 and the lower limit load detector 42, respectively. And the upper limit load detector 40 and the lower limit load detector 42
It is detected whether or not the load of the gas turbine 1 is at the upper limit value at which the output can be performed and whether the load is at the lower limit value.

The detection signal 4 of these upper limit load detectors 40
5 and the detection signal 46 of the lower limit load detector 42 are input to the master load control upper limit logic 41 and the master load control lower limit logic 43, respectively. Then, the master load control upper limit restriction logic 41 outputs an upper limit restriction command 47 to the master load controller 16 when the loads of all the gas turbines 1 are at the upper limit values that can be output by each gas turbine. Similarly, the master load control lower limit limiting logic 43
Outputs a lower limit command 48 to the master load controller 16 when the loads of all the gas turbines 1 are at the lower limit values that can be output by each gas turbine.

[0030] Then, the master load controller 16, Sable above current value when the upper limit command 47 is input
Fixed so that the value of the loop target load signal 12 does not increase,
Further, when the lower limit command 48 is manually input, the sub-loop target load signal 12 is fixed so as not to be reduced below the current value.

Next, the characteristics when the load control device of the combined cycle power plant according to the present embodiment having the above-described configuration controls under the same conditions as those shown in FIG. 4 will be described with reference to FIG. I do.

As shown in FIG.
4 is increased from 0 MW to 225 MW, first, the total load signal 15 follows the master target load signal 14 by the fast-response gas turbine 1 in the same manner as before until the time a.

At time a, the load on all gas turbines 1 reaches the upper limit of 50 MW. Therefore, after time a, the load 30 of the gas turbine 1 becomes constant. Therefore, time a
The subsequent rise of the total load signal 15 depends on the rising speed of the load 31 of the steam turbine 5 having a slow response, and the total load signal 15 cannot follow the master target load signal 14. As a result, the deviation between the master target load signal 14 in the master controller 9a and the total load signal 15 increases to the positive side.

Here, in the conventional control device, the sub-loop target load signal 12 continues to increase in accordance with this deviation.
On the other hand, in the present embodiment, since the upper limit command 47 is input to the master load controller 16 at time a, the sub-loop target load signal 12 is fixed to the value at time a.

For this reason, at time b, when the master target load signal 14 and the total load signal 15 coincide with each other, and the deviation thereof becomes negative, the sub-loop target load signal 12 immediately decreases, and as a result, the fuel control valve Operation command 18
Therefore, the load 30 of the gas turbine 1 also decreases immediately, and the overshoot of the total load control signal 15 as shown in FIG. 4 can be prevented.

As described above, according to the present embodiment, it is possible to prevent an overshoot of the total load when the load of all the gas turbines reaches the upper limit value when the total load increases. In addition, when the total load falls, the undershoot of the total load when the load of all the gas turbines reaches the lower limit value can be similarly prevented.

[0037]

As described above, according to the load control device for a combined cycle power plant of the present invention, it is possible to prevent the occurrence of overshoot and undershoot when the total load rises and falls.
It is possible to perform better control than before.

[Brief description of the drawings]

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

FIG. 2 is a graph showing load control characteristics in the embodiment of FIG.

FIG. 3 is a block diagram showing an example of a conventional load control device.

FIG. 4 is a graph showing load control characteristics in a conventional device.

[Explanation of symbols]

9a Master control unit 11 Generator load signal 12 Sub-loop target load signal 13 Master load setter 14 Master target load signal 15 Total load signal 16 Master load controller 40 Upper limit load detector 41 Master load control upper limit restriction logic 42 Lower limit load detector 43 Master load control lower limit logic 44 Gas turbine load signal 45 Detection signal 46 Detection signal 47 Upper limit command 48 Lower limit command

Claims (1)

(57) [Claims] 1. A master load setter for outputting a master target load signal that is a target load signal of all the total loads of a gas turbine and a steam turbine of a combined cycle power plant; A master load controller that outputs a sub-loop target load signal to a sub loop control unit that outputs an operation command for a fuel control valve provided in each of the gas turbines, based on a deviation from the total load signal. A load signal of each of the gas turbines is input, and a plurality of upper limit load detectors for detecting whether or not the load value is an output upper limit value of the gas turbine, and outputs of all the upper limit load detectors are input. When the loads of all the gas turbines are at the upper limit value, an upper limit restriction command is output to the master load setter, and the sub-loop target A master load control upper limit logic to limit the increase in the value of the load signal, respectively inputted to the load signal of the gas turbine, the load value of a plurality of detecting whether or not the output possible lower limit of the gas turbine Lower limit load detector, manually output the output of all the lower limit load detector, when the load of all the gas turbine is at the lower limit, output a lower limit limit command to the master load setter, A load control device for a combined cycle power plant, comprising: a master load control lower limit limiting logic for limiting a decrease in the value of the sub-loop target load signal.