JPH07208113A - 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 which is corrected on the basis of a GT load control amount by atmosphere temperature and a unit load command signal as a boiler load command signal. CONSTITUTION:In a gas turbine (GT), when atmosphere temperature is raised, maximum output is reduced, and a property of GT exhaust gas is also changed. A unit load increase/decrease command signal is inputted from an outside to a memory 1, and an operating range is restricted by an upper/lower limit setting apparatus 2. The ratio between GT output in each atmosphere temperature and maximum output in a lowest atmosphere temperature is restricted by a function generator 4, and a GT load command signal is generated by a multiplicating apparatus 5. In a subtracter 6, a boiler load command signal for correcting the restricting amount of GT output is generated from the unit load command signal and a GT load command signal. It is thus possible to supplement a GT output reducing amount which is restricted at the atmosphere temperature in the range of output which is outputted by a boiler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load distribution control method for an exhaust gas reheat combined cycle plant equipped with a gas turbine and a boiler that burns fuel with the exhaust gas of the gas turbine.

[0002]

2. Description of the Related Art A gas turbine rotates a generator, the exhaust of the gas turbine is fed into a boiler, and the residual oxygen in the exhaust burns fuel to generate steam, which drives the steam turbine. In an exhaust gas reheat combined cycle power plant that rotates a different generator from
Conventionally, the operator manually sets the gas turbine load command and the boiler load command for the unit load command,
It was doing load distribution.

[0003]

Gas turbine (hereinafter referred to as G
The maximum output decreases when the atmospheric temperature rises, and the characteristics of 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 the entire operating range depending on the difference in atmospheric temperature. Therefore, even if the distribution ratio of the GT output and the boiler output is specified at a certain atmospheric temperature, if the atmospheric temperature fluctuates, the distribution ratio may be out of the specified range in the entire operating range.

[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 defined by the unit load command signal, then corrected based on the GT load control amount by the atmospheric temperature, and this is used as the GT load command signal, and the unit load command signal and the GT load command signal are combined. The present invention proposes a load distribution control method for a complex plant, which uses the difference as a boiler load command signal.

[0005]

In the present invention, the GT load is first defined by the unit load command signal, and then is limited based on the GT load control amount by the atmospheric temperature, and this is used as the GT load command signal. Is corrected in all operating areas. Therefore, the unit load command can be distributed so that the GT exhaust gas becomes excessive and bypasses the boiler, or conversely, the GT exhaust gas becomes too small to limit the boiler output, so that the efficiency is always high.

Further, since the difference between the unit load command signal and the GT load command signal is used as the boiler load command signal, 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 increase / decrease command signal from the outside is input to the memory (1), and the operation range is limited by the upper / lower limit setting unit (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 function generator (4) defines the ratio between the GT output at each atmospheric temperature and the maximum output at the minimum atmospheric temperature, and the multiplier (5) creates the GT load command signal. The subtracter (6) creates a boiler load command signal in which the GT output limit amount is corrected from the unit load command signal and the GT load command signal. (7)
Is an upper limit setting device that defines the upper limit of the boiler output.

In FIG. 1, with respect to the unit load command signal which is the output of the upper / lower limit setting device (2), the output of the function generator (4) is "1" when the ambient temperature is the lowest, and GT
The output of the multiplier (5) which is a load command signal and the output of the function generator (3) are equal. Then, the distribution ratio of the boiler load command signal and the GT load command signal, which is the output of the subtracter (6) obtained by subtracting the output of the multiplier (5) from the output of the upper and lower limit setting device (2), is calculated by the function generator (3 ) Will be the ratio specified in.

On the other hand, when the unit load command signal output from the upper / lower limit setting device (2) has the same value and the ambient temperature is high, G
When the T maximum output is small, the ratio to be corrected is calculated in the function generator (4), and the GT load command signal which is the output of the multiplier (5) is reduced by the correction amount. Since the difference between the unit load signal and the GT load command signal becomes the boiler load command signal, the amount of decrease in GT output due to the rise in atmospheric temperature is eventually corrected by the boiler output within the upper limit of the boiler output.

FIG. 2 shows an example of GT output characteristics at the minimum atmospheric temperature and GT output characteristics (load command) at an arbitrary atmospheric temperature.

In the present embodiment, the GT load command signal is corrected in the entire operating range by the correction of the ratio of the atmospheric temperature to the specified value of the GT load, whereby the GT exhaust gas becomes excessive and the boiler is bypassed, or the reverse operation is performed. Therefore, the unit load command can be distributed so as to be always efficient without causing the output to be too small and limiting the boiler output. Further, by using the difference between the unit load command signal and the GT load command signal as the boiler load command signal, the GT output limited by the atmospheric temperature can be increased within the range of the output that the boiler can output.

[0012]

In the method of the present invention, the GT load is limited with respect to the atmospheric temperature, and this limitation is corrected on the boiler side. Therefore, optimum load distribution can always be performed with respect to the unit load command, and GT, It is possible to issue 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 output characteristic of the present invention.

[Explanation of symbols]

 (1) Memory (2) Upper and lower limit setters (3), (4) Function generator (5) Multiplier (6) Subtractor (7) Upper limit setter

Claims (1)

[Claims] 1. In an exhaust gas reheat type combined plant equipped with 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 by the atmospheric temperature. It is corrected based on the gas turbine load control amount, and this is used as a gas turbine load command signal, and the difference between the unit load command signal and the gas turbine load command signal is used as a boiler load command signal. Load distribution control method for complex plant.