JPH039004A - Control method and device for power generating plant - Google Patents

Abstract

PURPOSE:To improve the stability of a power system, in a power generating plant where the steam introduced in a steam turbine is normally adjusted to a prescribed pressure by reversely interlocking the opening of a steam governing valve to that of a turbine by-pass valve according to the control signals determined from the output of a generator and so forth. CONSTITUTION:The subtraction 10 between a target generator output and an actual generator output is carried out for finding out an output deviation, so that a generator output control signal 14A is obtained according to the above deviation. Also subtraction 20 between a target generator frequency and an actual generator frequency is carried out for finding out a frequency deviation so that a frequency control signal 23A according to the above deviation. The addition 24 of these control signals 14A, 23A is carried out to obtain a target valve opening signal 25A, and the target signal 25A is distributed to respective target valve opening signals 28, 29 of steam governing valves 121, 122 and turbine by-pass valves 123, 124. The signal 28 is obtained by multiplying the signal 25A by a proper proportional gain KC through a proportional circuit 26, and the signal 29 is obtained by giving a negative gain -KB of opposite polarity to that of gain KC to the signal 25A.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a control method and apparatus for a power generation plant, and particularly to a control method and apparatus for a power generation plant in which steam introduced into a steam turbine is not controlled to a predetermined pressure. Regarding.

[Conventional technology]

There are various system configurations for power generation plants that generate steam from a boiler and guide it to a steam turbine to drive a generator and generate electricity. There are plants that do not implement this. This typical plant is a combine 1 to power generation plan 1- that uses a so-called gas turbine.In this plan 1-, the exhaust gas after doing work in the gas turbine has sufficient heat, so the exhaust heat A recovery boiler is used to recover maximum heat to generate steam, and the steam is introduced into a steam turbine without pressure regulation. Japanese Patent Publication No. 5783821
Figure 2 shows a conventional example of such a combined power generation plant, and its outline is shown in Figure 2.

In the figure, gas turbine 102. Air compressor 101
．． Steam Turbine] 042 The generator 103 is connected to one shaft, and the fuel burned in the combustor 105 turns into high-temperature gas and drives the entire gas turbine, that is, the shaft. The air necessary for combustion is supplied from an air compressor], 0.1,
In addition, the amount of fuel changes depending on the required output, etc.
Controlled by 0. After the thermal energy has been converted into rotational energy, the gas is sent to a boiler 110 for exhaust heat recovery, where it exchanges heat with feed water to generate steam, which drives the steam turpin 104.

The feed water is sent from the condenser 106 to the exhaust heat recovery boiler 110 by the condensate pump 107, and is then sent to the exhaust heat recovery boiler 110 from the low pressure 1 to the ram 108.
The steam generated in the high pressure drum 109 is driven to the low pressure stage of the steam turbine 104 via the low pressure steam control valve 122, and the steam generated in the high pressure drum 109 is driven to the high pressure stage of the steam turbine 1.04 via the high pressure steam control valve 121. It is supplied as commercial steam. The rotational energy of the gas turbine 102 and the steam turbine 104 thus obtained is converted into electrical energy by the generator 103 to obtain desired electric power. Note that 123 and 124 are a high pressure turbine bypass valve and a low pressure turbine bypass valve.

In this plant, the output control or frequency (speed) control of the generator ]-03 is performed by controlling the opening degree of the fuel control valve 120 and the steam control valves 121 and 122. On the other hand, the turbine bypass valves 123 and 124 are used to form a bypass path at the time of plant startup, or when the steam pressure becomes abnormally high (usually 1
0% high) is opened for plant protection.

A characteristic feature of this combined plant is that the purpose of the exhaust heat recovery boiler 110 and the steam turbine 104 is to recover the maximum amount of heat held in the gas turbine exhaust gas. There is no pressure control, and in this respect it is essentially different from variable pressure or constant pressure thermal power plants, which control the pressure to a predetermined value.

[Problem to be solved by the invention]

Fig. 2 shows a type in which one generator 103 is driven by a gas turbine 102 and a steam turbine 104, and is generally called a single-shaft type, but in contrast, a type in which one turbine generator is driven by multiple gas turbine exhaust gases. The type is called the multi-axis type.

In either case, the contribution ratio of the gas turbine output to the steam turbine output to the total power generation output is usually about 3:7 or 4:6. Therefore, when only the fuel control valve 120 is controlled for the purpose of stabilizing the frequency of the power system or controlling the generator output, only 30 to 40% of the total power generation output can contribute to emergency output/frequency control. It happens. In other words, if the amount of fuel is controlled, the amount of gas turbine exhaust gas will change, the amount of steam generated by the waste heat recovery boiler will change, and as a result, the steam turbine output will also change, but the power generator in this process There is a delay time of several minutes or more in the output/frequency response, so it is necessary to urgently output/frequency respond.
When trying to control the frequency, a sufficient effect cannot be obtained. In order to contribute 100% to the emergency output/frequency control, the steam control valves 121 and 122 must also be operated by the output/frequency control signals. In addition to the control valve 120, a steam control valve 121 is also operated.

However, according to the study conducted by the present inventors, in the above-mentioned power plants that do not have a steam pressure control function, even if the steam control valve is operated by the output/frequency control signal, the steam turbine will not be able to control the output/frequency of the power system. It turned out that I couldn't contribute enough.

It is generally understood that the amount of steam F flowing into the steam turbine is determined by the product of the difference between the pressures Pi and P2 before and after the steam control valve and the valve opening A, and that the power generation output is proportional to the amount of steam. The steam control valve in most power plants is used in a critical state, so the prepressure P1 and valve opening degree A of the steam control valve are
The amount of steam is determined by the product of This relationship is (1)
, expressed by equation (2).

F=A(Pt-P2)...(
1) F = AP I
...(2) The steam flow rate F in the combined power generation plant shown in Figure 2 is as shown in equation (2), and since the pressure P1 in front of the steam control valve is not controlled constant, the output/frequency control is It responds to the application of a signal as follows. In other words, for example, if the frequency increases due to an oversupply of power in the power system, even if the steam control valve is throttled to reduce the power generation output and lower the frequency, the front pressure P1 will increase.
As a result, the steam flow rate cannot be reduced as desired. Conversely, when the steam control valve is opened to increase the steam flow rate and restore the frequency, the steam flow rate cannot be increased due to a drop in the prepressure P1. On the other hand, it goes without saying that if the prepressure is kept constant, the opening degree of the steam control valve and the steam flow rate will increase or decrease proportionally, and good control can be achieved.

In this way, conventional power plants that do not have steam pressure control functions cannot fully demonstrate their output and frequency adjustment functions, but as power plants grow larger, they can contribute to improving the stability of the power system and can respond quickly. It is desired that

In view of the above, it is an object of the present invention to provide a power plant control method and apparatus that can sufficiently contribute to improving the stability of the power system and achieving high-speed response.

[Means to solve the problem]

In the present invention, when the steam control valve is controlled by an output or frequency control signal, the turbine bypass valve is linked to open and close in the opposite direction using the output or frequency control signal, thereby suppressing steam pressure fluctuations when the steam control valve is opened and closed. .

[Effect]

By opening and closing the turbine bypass valve in the opposite direction, fluctuations in steam pressure are suppressed, and the flow rate of steam flowing into the steam turbine can be determined approximately in proportion to the opening degree of the steam control valve.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention, in which a fuel control valve 120 of a gas turbine 102, a steam turbine 104, a fuel control valve 120 of a gas turbine 102, a steam turbine 104, and a
It controls artificial steam control valves 121 and 122 and turbine bypass valves 123 and 124.

Among these, the generator output control section is configured as follows. The difference (output deviation) between the generator target output and the generator actual output is calculated by the first subtractor 10, and steam turbine output control and gas turbine output control (not shown) are executed based on this deviation.

The deviation is multiplied by a coefficient of steam turbine output burden (ratio of the steam turbine output to the target output) by a proportional calculator 11, and is further multiplied by a proportional integral calculation via a rate of change limiter 12. The calculation is performed by one calculation unit 13. In addition, 14 is a turbine steam control valve 121, which is based on the generator output control signal 13A calculated as follows.
122 is a switch for appropriately excluding control of the turbine bypass valves 123 and 124 and implementing other control as necessary.

The system frequency control section is configured as follows. A second subtractor 20 calculates the difference (frequency deviation) between the generator target frequency and the actual frequency, and a function generator 21 calculates a generator output compensation amount corresponding to the frequency deviation. Next, similarly to the output control circuit, the coefficient of the compensation burden due to the steam turbine is multiplied by the second calculator 22 that performs proportional calculation, and the result is sent as the frequency control signal 23A via the switch 23 for excluding control. Output.

The output signals 14A and 23A from each of these control sections are added by an adder 24, and are limited by an upper and lower limit limiter 25 to within responsive upper and lower limits to obtain a valve opening target signal 25A.

This signal 25A is then used as the valve opening target signal 28 for the steam control valves 121, 122 and the turbine bypass valves 123, 12.
Of these, the signal 28 may be the signal 25A multiplied by an appropriate proportional gain Kc in the proportional circuit 26, for example, as shown in FIG. 3(a).
If the signal 25A is a variable control signal in the range of +10 (V) to 10 (V) as shown in the figure, the steam control valve will be fully open when the voltage is +10 (V), fully open when the voltage is +10 (V), and 0. (
The opening degree is controlled so that the opening degree becomes 50 (%) at the time of v).

On the other hand, the turbine bypass valves 1, 23 and 124 are controlled by a signal 29 obtained by applying a negative gain (-KB) to the signal 25 in a proportional circuit 27.

Here, the negative gain (-KB) means a gain of opposite polarity to the gain Kc of the proportional circuit 26, and the ratio of the absolute value of the gain is determined by the ratio of the valve capacities of the steam control valve and the turbine bypass valve. It will be done. In Figure 3(b), K B = K
5- shows the turbine bypass valve opening with respect to the valve opening target signal 25A when 25A is 10 (V) (fully open at 71, -10 (
V), it is fully opened.

Each valve responds to the valve opening target signal 25A as described above, but the valve opening target signal 25A itself indicates that the generator output matches the target value and the generator frequency matches the target value. The first arithmetic unit 13 and the second arithmetic unit 22 have been modified so that the voltage is 10 (V) during stable operation.

The above control device controls the fourth output when the generator output or frequency changes.
Respond as shown. Figure (a) shows a stable operating state (generator target output = actual output, generator target frequency = actual frequency,
In the valve opening target signal 25A-10 (V), when the target output increases or the actual output decreases and a positive deviation signal is applied to the first computing unit 13 (in the figure, it indicates an increase in the target output). ), and as the output of the first computing unit 13 increases, the target valve opening signal 25A becomes a signal of +10 (V) or more. As is clear from the temperature characteristics, steam control valves 121 and 122 are fully open.
Turbine bypass valves 123°6 124 remain fully open. In this case, the generator output is directly increased by increasing the fuel supplied to the gas turbine fuel control valve 120 based on the generator output deviation signal, and as a result, the input of the exhaust heat recovery boiler is increased. The increase in heat indirectly increases the generator output.

The figure (b) shows a case where the target output decreases or the actual output increases and a negative deviation signal is applied to the first computing unit 13 in a stable operating state (the figure shows a decrease in the target output). It shows each part signal and the degree of opening reduction, and the first arithmetic unit 1
3, the target valve opening signal 25A becomes +1.
Since the signal is below 0 (V), the steam control valve 121.1
22 is driven in the closing direction, and the turbine bypass valve 12
3°124 is driven in the opening direction. Since these opening and closing operations are performed in conjunction with each other, the steam turbine inlet pressure P1
decreases rapidly, and therefore, as is clear from equation (2), it is possible to rapidly and stably reduce the generator output.

Note that the negative generator output deviation signal is also applied to a control valve (not shown) of the gas turbine fuel control valve 120, causing it to operate to reduce the amount of fuel.

FIG. 2C shows a case where the actual generator frequency decreases and a positive deviation signal is applied to the second arithmetic unit 22 in a stable operating state. In this case, it is clear that the frequency can be recovered by increasing the generator output, and the signals of each part and the valve opening are controlled in the same way as in the case (a) above, so detailed explanation will be omitted.

(d) in the same figure shows a case where the generator actual frequency increases and a negative deviation signal is applied to the second computing unit 22 in a stable operating state, and as in the case (b) above, each part signal Since it is clear that the frequency can be recovered if the generator output is reduced by controlling the valve opening and the valve opening, a detailed explanation will be omitted here.

The present invention operates as described above and can control the generator output and frequency to predetermined values, but the method (b) allows the generator output and frequency to be urgently and stably controlled.

This is notable in case (d). Figure 5 shows (
As a specific example of d), it shows the response of the generator actual frequency when a part of the power transmission system is cut off and the generator shifts to so-called grid islanding operation.
In a case where the overspeed 1-rip level was exceeded in an extremely short period of time and the plant had to be shut down, as in a), according to the present invention, the plant stoppage is prevented by a sudden decrease in the generator output. be able to.

According to the above explanation, the steam control valves 121 and 122 and the turbine bypass valve 1
It is clear that the proportional circuits 23 and 124 operate in opposite directions, such that when one opens, the other closes, and in this sense, the proportional circuits 26 and 27 are a pair of signal converters for reverse linked operation. It can be said. Therefore signal converter 2
The angle of 6°27 can be realized not only by a proportional circuit but also by a well-known electrical or mechanical biasing means.

Furthermore, according to FIGS. 1 and 4, in the present invention, when the experimental values of the generator output or generator frequency are smaller than their target values, the steam control valves 121, 19, 122 and the turbine bypass valve 123, 124 is the gas turbine 102 because it is fully open and maintained in the fully open state.
When only the fuel flow control valve 121 and the turbine bypass valve 1 are controlled, and the actual detected value of the generator output or generator frequency is larger than their target value, the steam control valve 121°1.22 and the turbine bypass valve 1 are controlled.
23 and 124 will be controlled.

Furthermore, when the steam regulator valve is at an intermediate opening, the turbine bypass valve regulates the pressure when operating the steam regulator; however, in this case, there is little need to regulate the pressure to a constant value; If the valve cylinder pressure can be suppressed when the pressure fluctuates, the generator output can be changed at high speed. From this, it can be said that the present invention operates the steam turbine according to the steam pressure determined on the boiler side (without pressure regulation) in normal operating conditions, and regulates the pressure to suppress pressure fluctuations when operating the steam control valve. .

Incidentally, in FIG. 1, numerals 5 and 6 are signal switching devices, and as shown in FIG. 6, each valve can be controlled by various control signals. In other words, the steam control valve 121°0-122 is operated by a signal from the program control unit 1 at the time of starting and stopping, instead of the target opening signal 28 shown in FIG.
The turbine bypass valves 123 and 124 can also be operated by a signal from the steam control valve inlet pressure control section 2 instead of the target opening degree signal 29 shown in FIG. 1 as appropriate.

Hereinafter, we will introduce the modifications and application examples 2 and 3 in Section 2 of ``Practicing the Present Invention''. This can be dealt with by creating a difference in the response of the gas turbine fuel control valve and the response of the steam turbine steam control valve (turbine bypass valve) to frequency changes, as shown in Figure 7. This can be achieved by providing a difference between the functions of the steam turbine function generator 21 in FIG. 1 and the gas turbine function generator (not shown).

In addition, the above-mentioned switch 14 allows the output control circuit to be used/
Selection of exclusion: The switch 23 allows selection of use/exclusion of the frequency control circuit. Use only one side 2 Use both 2
It is possible to switch between using both and operating both depending on the need.

In addition, this figure shows an example in which there is one steam control valve and one turbine bypass valve, but in the case of a mixed pressure turbine as shown in Fig. 2, the circuit shown in Fig. 1 can be applied, This is possible by providing two types of circuits, one for high pressure and one for low pressure.Furthermore, a selection circuit may be provided to control only the valve on the side of high pressure/low pressure that greatly contributes to the output, for example.

In order to further improve controllability, it is also possible to add the following functions.

(1) If the turbine bypass valve is fully open during output control, the output increase signal is locked (increase blocked).

(2) Although it will sacrifice efficiency to some extent, the turbine bypass valve is maintained at a constant opening state and the steam turbine output is adjusted. This makes it possible to adjust the output in both directions, even in the normal load operating range.

According to the embodiment of the present invention, the steam turbine output, which was conventionally regulated indirectly by adjusting the output of the gas turbine, is directly controlled. For example, as shown in FIG. Conventionally, when only the gas turbine output is reduced, the wave number is prevented from exceeding the turbine overspeed 1 to rip level, resulting in the characteristics shown in Figure (b).
This has the effect of greatly improving plant operability.

〔Effect of the invention〕

According to the present invention, the output of both the gas turbine and the steam turbine can be adjusted in coordination, and the process can maintain stability even in the face of sudden changes in output.
This has the effect of significantly improving plant operability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a control circuit according to the present invention, FIG. 2 is a diagram showing an example of a power generation plan 1 to which the present invention can be applied,
3 is a diagram showing the proportional cane of the proportional circuit 26,273 in FIG. 1, FIG. 4 and a diagram explaining the operation of the circuit in FIG. (Fig. 7 is a diagram showing the response of the fuel flow control valve and the steam control valve to frequency changes. 25A - Valve opening target signal, 102 Gas turbine,
]]03 generator, ]]04 steam turbine, 120 combustion flow rate adjustment JT, ]]21 high pressure steam control valve, 122...low pressure steam control valve, 123...high pressure turbine bypass valve,]
-24 Low pressure turbine bypass valve.

Claims (1)

[Scope of Claims] 1. A steam turbine that introduces steam generated in a boiler, a steam control valve provided at the inlet of the steam turbine, a turbine bypass valve that bypasses the steam introduced into the steam turbine, and the steam In a power generation plant, the steam introduced into the steam turbine is not always adjusted to a predetermined pressure, and the steam introduced into the steam turbine is not always adjusted to a predetermined pressure. A method of operating a power generation plant characterized by operating the opening degrees of a steam control valve and a turbine bypass valve in reverse linkage. 2. A gas turbine, a fuel flow control valve for adjusting the amount of fuel input to the gas turbine, a boiler that uses the gas turbine exhaust gas as a heat source, a steam turbine that introduces the steam generated in the boiler, and an inlet of the steam turbine. In a power generation plant comprising a steam control valve provided in a steam turbine, a turbine bypass valve for bypassing steam introduced into the steam turbine, and a generator driven by the steam turbine and a gas turbine, the generator output or When the actual detected value of the generator frequency is smaller than those target values, only the fuel flow control valve of the gas turbine is controlled, and when the actual detected value of the generator output or generator frequency is larger than those target values, A method of operating a power generation plant characterized by controlling a steam control valve and a turbine bypass valve. 3. A steam turbine that introduces the steam generated in the boiler, a steam control valve provided at the inlet of the steam turbine, a turbine bypass valve that bypasses the steam introduced into the steam turbine, and power generation driven by the steam turbine. In a power generation plant where the steam introduced into the steam turbine is not always adjusted to a predetermined pressure, when the steam control valve is at an intermediate opening degree, the pre-valve pressure of the steam control valve is adjusted to the turbine pressure. A method of operating a power generation plant characterized by regulating pressure using a bypass valve. 4. A steam turbine that introduces the steam generated in the boiler, a steam control valve provided at the inlet of the steam turbine, a turbine bypass valve that bypasses the steam introduced into the steam turbine, and power generation driven by the steam turbine. In a power generation plant where the steam introduced into the steam turbine is not always adjusted to a predetermined pressure, when reducing the generator output from a constant generator output state,
A method for operating a power generation plant, comprising closing the steam control valve from a fully open state and opening a turbine bypass valve from a fully closed state. 5. A steam turbine that introduces the steam generated in the boiler, a steam control valve provided at the inlet of the steam turbine, a turbine bypass valve that bypasses the steam introduced into the steam turbine, and power generation driven by the steam turbine. A power generation plant consisting of a subtracter for determining the deviation between the generator output target value and the actual output, a computing unit for obtaining an output according to the output of the subtracter, and the above-mentioned steam controlled by the output of the computing unit. a regulator valve, a signal converter that performs signal conversion on the output of the arithmetic unit, and the turbine bypass valve controlled by the output of the signal converter, and the signal converter reverses the steam regulator valve and the turbine bypass valve. A control device for a power generation plant characterized by interlocking operation. 6. A steam turbine that introduces the steam generated in the boiler, a steam control valve provided at the inlet of the steam turbine, a turbine bypass valve that bypasses the steam introduced into the steam turbine, and power generation driven by the steam turbine. A power generation plant consisting of a subtracter for determining the deviation between the generator frequency target value and the actual frequency, a computing unit for obtaining an output according to the output of the subtracter, and the above-mentioned steam controlled by the output of the computing unit. a regulator valve, a signal converter that performs signal conversion on the output of the arithmetic unit, and the turbine bypass valve controlled by the output of the signal converter, and the signal converter reverses the steam regulator valve and the turbine bypass valve. A control device for a power generation plant characterized by interlocking operation. 7. A steam turbine that introduces the steam generated in the boiler, a steam control valve provided at the inlet of the steam turbine, a turbine bypass valve that bypasses the steam introduced into the steam turbine, and power generation driven by the steam turbine. A power generation plant consisting of a generator, a first subtractor that calculates the deviation between the generator frequency target value and the actual frequency, a first calculator that obtains an output according to the output of the first subtracter, and a generator. a second subtracter that obtains a deviation between the frequency target value and the actual frequency; a second arithmetic unit that obtains an output according to the second subtracter output; a first arithmetic unit output and a second arithmetic unit output; an adder that calculates the sum of A control device for a power generation plant, comprising: a control device for a power generation plant, wherein the signal converter causes a steam control valve and a turbine bypass valve to operate in reverse synchronization with each other. 8. A gas turbine, a fuel flow control valve for adjusting the amount of fuel input to the gas turbine, a boiler that uses the gas turbine exhaust gas as a heat source, a steam turbine that introduces the steam generated in the boiler, and an inlet of the steam turbine. In a power generation plant comprising a steam control valve provided in the steam turbine, a turbine bypass valve for bypassing steam introduced into the steam turbine, and a generator driven by the steam turbine and the gas turbine, a generator frequency target is provided. a first subtractor that obtains an output corresponding to the output of the first subtractor; a second calculator that obtains a deviation between the generator frequency target value and the actual frequency; a subtracter, a second arithmetic unit that obtains an output according to the output of the second subtracter, an adder that obtains the sum of the output of the first arithmetic unit and the output of the second arithmetic unit, and is controlled by the output of the adder. the steam control valve, the signal converter that performs signal conversion on the output of the adder, the turbine bypass valve that is controlled by the output of the signal converter, the first subtracter output and the second subtracter output. 1. A control device for a power generation plant, comprising: a fuel flow control valve for a gas turbine controlled by a gas turbine; and a control device for a power generation plant, wherein the signal converter causes a steam control valve and a turbine bypass valve to operate in reverse synchronization with each other.