JPS59122712A - Load control device for complex cycle electric power plant - Google Patents

Abstract

PURPOSE:To secure safety and smooth operation in time of trouble happening, by installing both of a limit circuit outputting a load limit signal in time of trouble happening in a plant and a low value preferential circuit outputting a load limit signal in taking preference over an ordinary load signal. CONSTITUTION:A steam turbine is driven by such steam as produced in making full use of waste heat out of a gas turbine. At a maximum load control system, a function generator 30 outputs a maximum load setting signal commensurate to the details of the esisting variation element signal. An adder 37 finds the sum total of maximum load setting signals Pmax(1)-Pmax(n) as to all shafts A1-An, and the calculated value is given to a lower limiter 39. Doing like this, both of minimum load and maximum load, receiving the variation element signal, are always limited so as to become within the tolerance automatically according to the condition of a complex cycle plant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention refers to a combined cycle power plant including a gas turbine and a steam turbine, which is referred to as a combined cycle plant. ) related to a load control device. In particular, the present invention relates to an upper and lower limiter circuit that limits the maximum or minimum allowable load range of the combined cycle plant to an appropriate value depending on the plant itself or surrounding conditions.

[Technical background of the invention]

A combined cycle plant is a gas turbine that burns fuel to drive a generator to rotate.
This is a power generation plant that uses a method in which the exhaust heat is recovered by an exhaust heat recovery boiler to generate steam, and the generated steam drives a steam turbine and a generator. In this sense, it is also called a combined cycle or combined cycle plant. The overall power output of this combined cycle plant depends on the fuel supply valve of the gas turbine, so by controlling this fuel flow 1, the power output of the entire plant can be controlled. In general, combined cycle plants are broadly classified into single-shaft types and multi-shaft types, depending on whether the gas turbine and steam turbine are connected by the same shaft or separated into multiple shafts.

Load Control Next, the load control device for the above-mentioned combined cycle plant will be explained, but to simplify the explanation, an example of a single-shaft type combined cycle plant will be used (see FIG. 1). In FIG. 1, first, the output control of the gas turbine 9 is as follows. The speed setting signal from the speed setter 1 is given to the subtracter 2. On the other hand, rotation speed detection signals of the gas turbine 9 , the steam turbine 13 , and the generator 100 are fed back from the rotation speed detector 6 provided in the compressor 8 to the subtractor 2 . The subtracter 2 calculates the deviation between the speed setting value and the fed-back detection value, and outputs the deviation signal to the operational amplifier 3. The operational amplifier 3 performs a "proportional" or "proportional integral" calculation based on the manually input deviation signal, and sends the calculated value to the fuel adjustment valve 5 via the servo amplifier 4.
Control its opening. This opening adjustment controls the fuel flow rate supplied to the combustor 7 of the gas turbine 9, and as a result, the output of the gas turbine 9 is controlled to match the speed setting value.

Next, let us discuss the output control of the steam turbine 13. The steam enthalpy supplied from the exhaust heat recovery boiler 11 to the steam turbine 13 is determined by the enthalpy of the exhaust gas from the gas turbine 9, so by keeping the steam control valve 12 fully open or at a constant opening, the condenser 14 can be adjusted. ``Turbine output is uniquely determined by the relationship with the degree of vacuum.

From the above, in the combined cycle plant, the output to the power system is a value obtained by multiplying the sum of the outputs of the gas turbine 9 and the steam turbine 13 by the efficiency of the generator 10.

The load (generator output) is controlled by calculating the deviation between the load setting signal from the load setting device 16 and the actual load detection signal from the load detector 15 using a subtracter 17, and giving the calculated deviation signal to the speed setting device 1. This is done by controlling the setting device 1. As a result, it is possible to control the deviation so that it ultimately becomes zero (that is, the load becomes equal to the load setting value).

The following is an example of a comprehensive load control device when a combined cycle plant having the above characteristics is a multi-shaft type and is planned to function as one unit from the perspective of the power system. Shown in Figure 2.

In FIG. 2, either the load command value of the combined cycle plant given from the central power supply station 18 or the station mode load command value given from the load setter 20 is selected by the switch 19 and manually inputted to the adder 21. Ru. on the other hand,
A frequency bias signal from a frequency individual bias generator 22 for compensating system frequency deviation is input to an adder 21, and both signals are added. The added signal is subtracted by the subtracter 23 from the output of the entire combined cycle plant (the sum of the combined cycle plant outputs from the first axis A□ to the nth axis An) given from the adder 24 to obtain a deviation.

Next, this deviation is input to the proportional integrator 25, which is an overall load controller, and the proportional integrator 25 issues a load target command for each axis based on the manual deviation value. Each axis 1~
An is provided with a subtracter 27, a generator output detector 26, and a proportional-integral calculator 28, respectively. Since the axes A1 to An are all the same, they are designated by the same reference numerals.

Now, when the load target command is given to the subtractor 27 of each axis A1 to An, each subtractor 27 is connected to the generator output detector 2 of each axis.
6 and outputs the deviation to the proportional-integral circuit. The proportional-integral calculator 28 outputs speed setting signals for each of the axes A1 to An based on the input deviation value. The following operation is the same as the control operation shown in FIG.
~A, respectively, and output control of the combined cycle plant is performed by the control device shown in FIG.

[Problems with background technology]

In the above-mentioned single-shaft type and hakama-shaft type combined cycle plants, the maximum or minimum load that the plant can take (hereinafter referred to as load tolerance range) depends on the plant itself or the surrounding conditions (hereinafter referred to as variable factors). It has the characteristic that it changes significantly. In particular, gas turbines are susceptible to atmospheric temperature and the like.

If a load command that exceeds the allowable load range is given from the combined cycle plant side as a load command to each axis Al-mu, the control deviation will increase and the load command will quickly return to within the allowable range. A problem occurs that impairs responsiveness. Therefore, in a combined cycle plant, it is necessary to constantly monitor the maximum load and minimum load that can be taken, and to issue a command after determining whether the load command itself is appropriate in comparison with the allowable range.

Here, the main variables in the allowable load range (maximum load) are determined by atmospheric temperature, maximum turbine inlet temperature, calorific value of fuel, condenser vacuum, and upper limit of operation or generator output. There is a maximum load, etc. In general, the higher the atmospheric temperature, the lower the maximum load l·ma, and even at the same atmospheric temperature, the higher the turbine population maximum temperature, the higher the fuel calorific value, the higher the maximum load. Note that gas turbines are distinguished by the names of base operation and peak operation depending on the target value of the maximum turbine inlet temperature. In the case of the degree of vacuum of the condenser, the higher the degree of vacuum, the larger the heat drop of the steam turbine can be taken, and therefore the maximum load can be taken correspondingly larger. Furthermore, the maximum load determined by the operation or the output upper limit of the generator is often determined uniformly regardless of the atmospheric temperature.

On the other hand, in the case of the lowest load within the allowable load range, it is determined by the minimum fuel flow, restrictions from the combustor, operational restrictions such as the amount of NOx generated, etc., and is usually set at the maximum value of these. be.

The relationship between the above variable factors and the maximum load is shown in FIGS. 3 and 4. Figure 3 shows an example where the horizontal axis is the atmospheric temperature and the vertical axis is the output (load), while Figure 4 shows the condenser vacuum degree on the horizontal axis in relation to the ratio of load change. be. In Figure 3, Pwax is the line indicating the maximum load, b is the upper limit during base operation, Ppl is the upper limit when fuel with low calorific value is used during repeater operation, and Pp2 is the fuel with high calorific value during peak operation. The upper limit and Pm1n indicate the minimum load when using .

Here, the reason why the maximum load value varies depending on the atmospheric temperature and the turbine population temperature as described above will be briefly explained as follows. This can be explained as follows based on the relationship between the thermal efficiency of the gas turbine plant and the turbine inlet temperature or atmospheric temperature. Generally, the combustion efficiency ηa of a gas turbine plant including a compressor 8, a combustor 7, and a gas turbine 9 is approximately determined by the equation (1). However, the combustion efficiency is assumed to be approximately 1.

However, when the τ-si equation (1) is differentiated by τ, the following is obtained. Since the right-hand side of equation (2) is always positive, eηa
/δτ) 0, i.e. η. is a monotonically increasing function of τ.

This means that if the atmospheric temperature is constant, increasing the maximum turbine inlet temperature will increase η.

This means that the amount increases. Conversely, when the turbine population temperature is constant, as the atmospheric temperature increases, τ decreases, and Hiro decreases. Thus, it can be seen that the thermal efficiency of a gas turbine plant depends on various conditions such as the turbine inlet temperature and the atmospheric temperature.

[Purpose of the invention]

The present invention is a load control device for a single-shaft type or multiple-shaft type combined cycle plant, and is capable of keeping load commands within the maximum and minimum load tolerance values possible for a combined cycle plant even when various variable factors fluctuate. It is an object of the present invention to provide a load control device that enables smooth control.

[Summary of the invention]

In order to achieve the above object, a load control device according to the present invention receives a variable element signal that considers variation in the maximum or - minimum allowable load range of a combined cycle plant, and loads the combined cycle plant corresponding to the variable element signal. The present invention is characterized in that it includes a function generator that generates a limit signal that limits an allowable range, and an upper and lower limit limiter that applies this function generated signal to a load command signal.

[Embodiments of the invention]

Hereinafter, embodiments of a load control device for a combined cycle plant according to the present invention will be described with reference to the drawings. FIG. 5 shows an example of a load control device for a multi-shaft combined cycle plant. The parts in FIG. 5 that overlap with those in FIG. 2 are given the same reference numerals and will be described below.

The load limiting circuit according to the present invention can be roughly divided into a maximum load control system and a minimum load control system. First, in the minimum load control system,
The minimum load setting signal "m1n(x) to Pm1n(n)" for each axis A1 to A is set by the minimum load setter 29 to the adder 38 and each axis A1 to An via the switch 23, respectively. is applied to the lower limit limiter 42.

The switch 33 is used to manually set the minimum load, and in the case of manual setting, the switch 33 is operated to output a multi-wave signal via the integrator 36. The adder 38 supports all axes A1 to A.
Minimum load setting signal Pm1n(1)~”m1 for n
The sum of n(n) is determined, and the calculated value is given to a lower limit limiter 40 provided in the overall load control system.

That is, the sum of the minimum load setters "rPmird 1) to Prn1n(n) for each -4h A 1-An is the load command signal of the general load control system (shoes, general load setter 20
At the same time, each minimum load setting signal Pmin(t)-Pmi II(n) is applied individually to the load command signal (output from the overall load controller section) for each axis M1 to Mn. Load setting signal Pm1n(1) to P
m1n(b) is given.

On the other hand, in the maximum load control system, variable element signals (fuel type signal A1, operation distinction signal B for peak operation or base operation, atmospheric temperature signal C, etc.) are input to the function generation signal 3θ. Each variable element signal A, B, O is supplied to the function generator 3o in advance.
A corresponding output value is set as a function of , and therefore a maximum load setting signal corresponding to the content of the current variable element signal is output. This output is given to the multiplier 32, but it is corrected by the output from the function generator 31, which outputs the maximum and load changes in response to signals from other variable elements (condenser temperature), and is then corrected by the output from the function generator 31, which outputs the maximum load setting signal. Pma4x)～Pm
It is applied as ax(n) via a switch 34 to an adder 37 and an upper limit limiter 41 provided for each of the axes 1 to An. The switch 34, like the switch 33, is used when manually setting the maximum or load. The boost signal in the case of manual setting is provided via an integrator 35. The adder 37 calculates the sum of the maximum load setting signals "max(t) to Pmax(n) for all axes A1 to An, and the calculated value is given to the lower limiter 39. That is, each axis A
1 to A, the maximum load setting signal Pmax(t) to P
The sum of max(n) is the load command signal (
At the same time, it is added to the output from the general load setting device 20,
Each maximum load setting signal Pmax(x) to Pmax(n) is individually given to the load command (output from the general load controller 25) for each axis A1 to An.

As described above, the minimum load and maximum load are automatically limited to be within the permissible range according to the situation of the combined cycle plant in response to the variable element signal.

Although the minimum load is set using the setting device 29, a function generator that generates a predetermined minimum load value by inputting a variable element signal that causes a change in the minimum load range may also be used.

Further, in the above embodiments, the case where the present invention is applied to a multi-shaft combined cycle plant has been described, but it goes without saying that the same concept can be applied to a single-shaft type plant.

〔Effect of the invention〕

As described above, according to the present invention, the load command is automatically limited to the current maximum and minimum load based on the conditions under which the combined cycle plant is placed, and the load command is always kept within the safe tolerance range. Therefore, an increase in control deviation can be prevented and smooth control can be achieved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the configuration of a load control device for a conventional combined cycle plant (single-shaft type), and Figure 2 is a block diagram showing an example of the configuration of a general load control device for a conventional combined cycle plant (multi-shaft type). The block diagram shown in Figure 3 shows the variable elements (atmospheric temperature) and plant output (load).
Figure 4 is an explanatory diagram showing the correlation between the variable element (condenser vacuum degree) and load change, and Figure 5 is an explanatory diagram showing the correlation between the variable element (condenser vacuum degree) and the load change. FIG. 1 is a block diagram showing an embodiment of a comprehensive load control device. 1... Speed setter 2... Subtractor 3... Operational amplifier 4... Servo amplifier 5... Fuel adjustment valve 6... Rotation speed detector 7... Gas turbine combustor 8. ...Compressor 9...Gas turbine 10...Generator 11...Exhaust heat recovery boiler
12...Steam control valve 13...Steam turbine 1
4... Condenser 15... Load detector 16...
・Load setter 17...Subtractor 20...Comprehensive load setter 5...Comprehensive load controller 29...Minimum load setter 30...Function generator 31...Function generator 32...・Multiplier 3
7... Adder 38... Adder 39...
・Upper limit limiter 40...Lower limit limiter 41...
Upper limit limiter 42...Lower limit limiter. Applicant's agent Kiyoshi Inomata Figure 1 Figure 14 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a load control device for a combined cycle generator [7' runt] that drives a steam turbine with steam generated using exhaust heat of a gas turbine, - the maximum or minimum of the combined cycle power generation lights; a function generator that receives a variable element signal that causes variation in an allowable load range and generates a limiting signal that limits the allowable load range of the combined cycle power plant corresponding to the variable element signal; A load control device for a combined cycle power plant, comprising an upper and lower limit limiter for applying a load command signal to the cycle power plant. . 2. The device according to claim 1, wherein the combined cycle power generation plant is a single-shaft type in which a gas turbine, a steam turbine, and a generator are connected together on the same shaft. Plant load control device. 3. In the device according to claim 1, the combined cycle power generation plant is a multi-shaft plant in which a combination of a gas turbine and a generator, and a combination of a steam turbine and a generator are connected by different shafts. A load control device for a combined cycle power generation plant characterized by: 4. The device according to claim 3, characterized in that the combined cycle power generation plant is controlled by a general load control device so as to function as one unit when viewed from the power system. Plant load control device. 5. In the device according to claim 3 or 4, when the combined cycle power plant is of a multi-shaft type,
1. A load control device for a multi-valley cycle power generation plant, characterized in that a limit signal is given to a general load command signal for the entire plant and a load command signal for each axis. 6. In the apparatus according to claim 1, 2, 3, 4, or 5, the variable element signal includes at least atmospheric temperature, condenser vacuum, gas turbine fuel type, and operation mode. A load control device for a combined cycle power plant, characterized by having content related to.