JPH07208114A - Load distribution control method for compound plant - Google Patents

Abstract

PURPOSE:To enable optimal load distribution in relation to a unit load command at all times by setting a difference between a GT load command signal on the basis of a GT load restricting amount and GT load upper limit amount by atmosphere temperature and a unit load command signal as a boiler load command signal. CONSTITUTION:A unit load command is inputted from an outside into a memory 1, an operating range is restricted by an upper/lower limit setting apparatus 2. A distribution ratio between gas turbine (GT) output and boiler output in each atmosphere temperature is restricted by a function generator 4 so as to increase a unit efficiency in the restricting range of a boiler as larger as possible. A signal which is generated by a multiplication apparatus 5 and a signal which is regulated maximum output of GT in each atmosphere temperature by a function generator 6 are compared and selected with each other by a selector 7 so as to form a final GT load command signal. A boiler load command signal for correcting the regulating amount of GT output is generated from a unit load command signal and a final GT load command signal in a subtracter 6. It is thus possible to enable optimal load distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a gas turbine (hereinafter referred to as G
T) and a boiler for combusting fuel with exhaust gas of the same GT, and a load distribution control method for an exhaust gas reheat combined cycle power plant.

[0002]

2. Description of the Related Art The GT is used to rotate a generator, the exhaust gas from the GT is fed into a boiler, the residual oxygen in the exhaust gas is burned to generate steam, and a steam turbine is driven to operate the steam turbine. In an exhaust gas reheat combined cycle power generation plant in which another generator is rotated, conventionally, an operator manually sets a GT load command and a boiler load command for a unit load command to perform load distribution.

[0003]

The GT is characterized in that the maximum output decreases as the atmospheric temperature rises, and the properties of the GT exhaust gas also change. On the other hand, since the boiler burns fuel with GT exhaust gas to obtain an output, the output ratio of the GT and the boiler may be different in all operating regions depending on the difference in atmospheric temperature. Therefore, even if the distribution ratio of GT output and boiler output is specified at a certain atmospheric temperature, if the atmospheric temperature changes,
There is a possibility that the distribution ratio will be out of regulation in all operating areas.

[0004]

In order to solve the above-mentioned conventional problems, the present inventor has proposed in an exhaust gas reheat type combined plant equipped with a GT and a boiler for combusting a fuel with the exhaust gas of the GT. The load is first specified by the unit load command signal, then corrected based on the GT load limit amount by the atmospheric temperature, and further by this signal and the atmospheric temperature.
A GT load command signal is selected by comparing and selecting a signal limited based on the T load upper limit amount, and a difference between the unit load command signal and the GT load command signal is used as a boiler load command signal. It proposes a load distribution control method for a complex plant.

[0005]

In the present invention, the GT load is first defined by the unit load command signal and then corrected based on the GT load limit amount due to the atmospheric temperature. Therefore, the GT load command signal is corrected in the entire operating range. . Furthermore, since this correction signal is compared and selected with the signal that specifies the GT maximum load according to the atmospheric temperature and used as the final GT load command signal, GT exhaust gas becomes excessive and bypasses the boiler, or conversely, it becomes too small. Therefore, the unit load can always be distributed with high efficiency in the entire load band without limiting the boiler output.

Further, the difference between the unit load command signal and the GT load command signal is used as the boiler load command signal, so that the GT output decrease limited by the atmospheric temperature is compensated for within the range of the output that the boiler can output. be able to.

[0007]

FIG. 1 shows an example of a control circuit for carrying out the method of the present invention. In this figure, a unit load command is input to the memory (1) from the outside, and the operating range is limited by the upper and lower limit setting device (2). The GT load command is defined by the function generator (3) based on the output of the upper and lower limit setting device (2). On the other hand, the distribution ratio between the GT output and the boiler output at each atmospheric temperature was defined by the function generator (4) and created by the multiplier (5) so that the unit efficiency was as large as possible within the limit range of the boiler. The signal and the signal in which the maximum output of GT at each atmospheric temperature is defined by the function generator (6) are compared and selected by the selector (7) to be the final GT load command signal. In the subtractor (8),
A boiler load command signal in which the GT output limit amount is corrected is created from the unit load command signal and the final GT load command signal. (9) is an upper limit setting device that defines the upper limit of the boiler output.

In FIG. 1, in the case of the lowest atmospheric temperature, the output of the function generator (4) is "1", and the function generator (for the unit load command signal which is the output of the upper and lower limit setting device (2) ( The output of 3) and the output of the multiplier (5) are equal. Further, since the maximum output value of GT at the lowest atmospheric temperature is output from the function generator (6), the output of the multiplier (5) is output as it is as the final GT load command signal by the selector (7). Then, the distribution ratio between the boiler load command signal, which is the output of the subtracter (8) obtained by subtracting the output of the selector (7) from the output of the upper and lower limit setting device (2), and the GT load command signal is the function generator. The ratio is defined in (3).

On the other hand, the unit load command signal output from the upper / lower limit setting device (2) has the same value, and the ambient temperature is high and the GT is high.
When the maximum output is small, it is corrected by the output of the function generator (4), and the output of the multiplier (5) is reduced by the correction amount. Further, since the maximum output value at the atmospheric temperature is defined by the function generator (6), the maximum GT load command at each atmospheric temperature can be obtained, and a higher GT load command can be obtained even in the operating load band. . Further, since the difference between the unit load signal and the GT load command signal becomes the boiler load command signal, as a result, the decrease amount of the GT output due to the atmospheric temperature is increased and corrected by the boiler output within the upper limit of the boiler output.

An example of the GT load characteristic at the lowest atmospheric temperature and the GT load characteristic at an arbitrary atmospheric temperature is shown in FIG.

FIG. 3 shows another example of a control circuit for implementing the method of the present invention. In this figure, a unit load command is input to the memory (11) from the outside, and the upper and lower limit setting device (12) is set.
Limits the operating area. And based on that output,
The function generator (13) defines the GT load command. on the other hand,
Distribution of GT output and boiler output at each atmospheric temperature
The signal generated by the function generator (14) and generated by the subtractor (15) and the maximum output of GT at each atmospheric temperature are determined by the function generator (16) so that the unit efficiency is as large as possible. To the selector (1
It is compared and selected in 7) and is used as the final GT load command signal. Further, a boiler load command signal in which the GT output limit amount is corrected is created by the subtracter (18) from the unit load command signal and the final GT load signal. (19) is an upper limit setting device.

The difference between the first circuit example described with reference to FIG. 1 and the second circuit example shown in FIG. 3 is as follows. That is, in the first circuit example, the setting of the function generator (4) is given in proportion to the setting of the function generator (3), but in the second circuit example, the setting of the function generator (14) is performed. It is given by the deviation from the setting of the function generator (13). As a result, the distribution of GT output and boiler output can be changed within the limit range of the boiler.
The unit efficiency can be maximized. FIG. 4 shows an example of the GT load characteristic at the minimum atmospheric temperature and the GT load characteristic at an arbitrary atmospheric temperature in the case of the second circuit example.

[0013]

According to the method of the present invention, the GT load is restricted with respect to the atmospheric temperature, and this restriction is corrected on the boiler side. Therefore, optimum load distribution can always be performed with respect to the unit load command, and GT It can be a load command to the boiler.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a control circuit for implementing the method of the present invention.

FIG. 2 is a diagram illustrating a GT load characteristic in the control circuit of FIG.

FIG. 3 is a diagram showing another example of a control circuit for implementing the method of the present invention.

4 is a diagram illustrating a GT load characteristic in the control circuit of FIG.

[Explanation of symbols]

 (1) Memory (2) Upper and lower limit setter (3) (4) (6) Function generator (5) Multiplier (7) Selector (8) Subtractor (9) Upper limit setter (11) Memory (12) ) Upper and lower limit setting device (13) (14) (16) Function generator (15) Subtractor (17) Selector (18) Subtractor (19) Upper limit setting device

Claims (1)

[Claims] 1. In an exhaust gas reheat type combined plant comprising a gas turbine and a boiler that burns fuel with the exhaust gas of the gas turbine, the gas turbine load is first specified by a unit load command signal, and then the gas due to atmospheric temperature is used. The signal is corrected based on the turbine load limit amount, and this signal is compared and selected with a signal limited based on the gas turbine load upper limit amount specified by the atmospheric temperature to form a gas turbine load command signal, and the unit load A load distribution control method for a complex plant, wherein a difference between a command signal and the gas turbine load command signal is used as a boiler load command signal.