JP3887777B2 - Governor-free control method and control apparatus for gas turbine power generation equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a governor-free control method and a governor-free control apparatus for a multi-shaft combined gas turbine power generation facility that is premised on grid-connected operation, and more particularly to compensate for system frequency fluctuations and The present invention relates to a control method and apparatus for adjusting a fuel amount command signal while keeping an operation state stable.
[0002]
[Prior art]
Conventionally, grid interconnection operation in a thermal power generation facility is performed as follows. In pulverized coal-fired power generation, since the boiler has a large heat capacity, governor-free operation is performed by adjusting the steam turbine supply steam amount according to system frequency fluctuations, which is equivalent to the boiler of gas turbine power generation equipment Since the combustor is a machine that recovers power by expanding high-temperature and high-pressure combustion gas obtained by the combustion reaction in a short time, the system frequency is adjusted by controlling the amount of fuel input.
[0003]
Furthermore, in the pulverized coal slag and gas turbine power generation equipment, since the turbine rotating shaft and the generator are connected, the load on the power generation equipment also varies according to the variation in the system frequency. For example, when the system frequency decreases, the rotational speed also decreases. In order to maintain the specified rotational speed, it is necessary to increase the amount of supplied fuel in the gas turbine power generation facility. Conversely, when the system frequency increases, the rotational speed increases and the amount of supplied fuel needs to be reduced. When the fluctuation frequency of the system frequency is as large as several minutes, frequency control operation (AFC: Automatic Frequency Contro1) is performed. During governor-free operation, the frequency is several Hz. The load cannot be tracked instantaneously due to delay or combustion reaction delay. In particular, in the case of a multi-shaft combined power generation facility, a generator is often connected to each of a plurality of target gas turbines, and system frequency fluctuations directly affect the gas turbine rotation speed. It becomes.
[0004]
A conventional governor control method will be described. The deviation between the actual MW signal (MW) indicating the actual output at the power generation facility and the output command value MWD (Mega Watt Demand) signal (MW) from the central power supply command station is calculated by the first subtractor. A load increase / decrease command is output so that the load deviation is zero by an analog memory having the obtained deviation as an input. In this analog memory, a change rate at which the corresponding power generation facility can stably follow the load is set in advance. The output of the analog memory is converted from the load deviation signal (MW) to the rotational speed signal (% SPD) of the gas turbine by the first gain setting device and then transmitted to the second subtracter. The actual rotation speed signal (rpm) is converted into a speed signal (% SPD) by the second gain setting device, and the deviation from the rated rotation speed (100%) set in the first constant setting device is set to the third. After being calculated by the subtractor, it is transmitted to the second subtractor 7. The output of the second subtractor is converted from the speed signal (% SPD) to the fuel amount command signal (FFD) by the third gain setting device that sets the settling rate of the power generation equipment, and then the first addition The fuel command signal at the no-load rated speed set in the second constant setter is added. The output signal of the first adder is input to the low value selector. To this low value selector, a load limiter control signal 22 obtained by adding the equivalent of several percent to 10% load to the governor control signal from the adder 9, and an exhaust temperature control signal adjusted by the exhaust temperature of the gas turbine equipment. Are selected, and the lowest value of the three signals is selected to control the gas turbine fuel related valve as the governor control command signal 24. Here, for example, when the actual MW signal or the rotation speed signal suddenly changes and the fuel command value suddenly increases, the load limiter control signal is generated by the above-mentioned addition signal corresponding to several to 10% load. The purpose is to suppress the input. Also, the exhaust temperature control signal suppresses excessive fuel injection when the exhaust temperature exceeds a preset exhaust temperature value in response to a sudden increase in exhaust temperature that occurs when abnormal combustion occurs in the combustor of the gas turbine. It is intended.
[0005]
On the other hand, recent gas turbine combustors are equipped with low N0x combustors using premixed combustion. Premixed combustion is designed to operate a fuel-air ratio defined by a mass ratio of fuel and combustion air at about 2 to 3% in order to reduce heat N0x generated by combustion. Therefore, when the stable combustion range is narrower than that of normal diffusion combustion and the governor-free operation is performed in a gas turbine power generation facility equipped with a low N0x combustor, a dynamic balance between the combustion air amount and the fuel, That is, it is necessary to keep the fluctuation of the fuel-air ratio in the process of changing the fuel amount or the combustion air amount within an allowable range. In the conventional control method described above, the system has not been made to keep the fuel-air ratio in the process of changing the fuel amount or the combustion air amount within the allowable range.
[0006]
[Problems to be solved by the invention]
The present invention relates to a multi-shaft combined gas turbine power generation facility that operates in a grid-connected manner, particularly a gas turbine generator equipped with a low N0x combustor that performs premixed combustion, so as to compensate for fluctuations in the system frequency. An object of the present invention is to control the fuel supply amount so that the stable operation condition of the gas turbine, in particular, the fuel-air ratio of the low N0x combustor satisfies an allowable value.
[0007]
[Means for Solving the Problems]
As mentioned earlier, when the system frequency fluctuates and the fuel amount is changed according to the fluctuation, if the system frequency fluctuates rapidly, the change in the supply amount of combustion air will cause the change in the fuel amount. May not be able to follow. This is because the speed of the operation of adjusting the supply amount of combustion air and the speed of change of the supply amount of combustion air accompanying the operation of the fuel amount adjustment valve are faster than the speed of change of the fuel supply amount accompanying the operation of the fuel amount adjustment valve. Because it is slow.
[0008]
In order to achieve the above object, the inventors have conducted various studies, and as a result, the fuel and air caused by the time difference between the change in the fuel supply amount when the system frequency fluctuates and the change in the supply amount of combustion air associated therewith. In order to avoid the fluctuation of the ratio, when the system frequency is inputted, it has been conceived to reduce the sensitivity to the fluctuation of the system frequency serving as an input for adjusting the fuel supply amount, thereby suppressing the time difference.
[0009]
That is, the means of the present invention for achieving the above object adjusts the fuel amount command signal so that the deviation between the power generation amount command signal of the gas turbine power generation facility and the actual power generation amount signal of the power generation facility is zero, In a governor-free control method for a gas turbine power generation facility that adjusts the power generation amount command signal using a frequency signal as an input, the rate of change of the input system frequency signal is limited so as to reduce sensitivity to fluctuations in the system frequency, The power generation amount command signal is adjusted by a signal whose rate of change is limited.
[0010]
In the means, system frequency fluctuation suppression filter means for removing small fluctuations having a period equal to or less than a desired period included in the input system frequency signal may be provided.
[0011]
Further, it is desirable that the inputted system frequency signal is used for adjusting the power generation amount command signal after passing through a first-order lag element in which a dead time is set.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 shows a control system diagram of governor control when the present invention is applied to governor control of a multi-shaft combined gas turbine power generation facility. A portion surrounded by a broken line in FIG. 1 is a portion according to the present invention, and a portion outside the broken line frame indicates a conventional governor control system.
[0013]
The illustrated control device includes a first subtractor 4 to which an actual MW signal 1 indicating the actual power generation amount of the power generation facility is input to one input side, and an analog memory connected to the output side of the first subtractor 4. 5, a first gain setter 6 to which the output of the analog memory 5 is input, a second subtractor 7 having the output of the first gain setter 6 as one input, and a second subtractor 7 A third gain setting unit 8 that receives the output of the third gain setting unit 8, an adder 9 that receives the output of the third gain setting unit 8, a constant setting unit 10 connected to the adder 9, A low value selector 11 connected to the output side, an adder 12 to which an MWD (Mega Watt Demand) signal 2 is input, an input side to the output side of the adder 12, and an output side to the first subtractor 4, the rate of change setting unit 13 connected to the other input side, and the system frequency fluctuation suppression filter to which the system frequency signal 3 is input. A dead band setting device 17 connected to the output side of the filter means 16, the system frequency fluctuation suppression filter means (hereinafter referred to as fluctuation suppression filter means) 16, and a change rate setting device connected to the output side of the dead band setting device 17. 18, a first-order lag element 15 whose input side is connected to the output side of the change rate setting device 18 and whose output side is connected to the adder 12, and the suppression connected to the change rate setting device 13 and the change rate setting device 18 One input side is connected to the output side of the rate setting unit 14, the second gain setting unit 19 to which the rotation speed signal 25 is inputted, and the second gain setting unit 19, and the output side is connected to the second side. A third subtracter 20 connected to the other input side of the subtractor 7 and a constant setting unit 21 connected to the other input side of the third subtracter 20 are configured.
[0014]
In addition to the output of the adder 9, the low value selector 11 includes a load limiter control signal 22 obtained by adding the equivalent of several percent to 10% load to the governor control signal from the adder 9, and gas turbine equipment The exhaust gas temperature control signal 23 adjusted by the exhaust gas temperature is input.
[0015]
1 includes an adder 12, a change rate setting device 13, a suppression rate setting device 14, a first-order lag element 15, a system frequency fluctuation suppression filter means 16, a dead zone setting device 17, and a change rate setting device 18. A speed adjustment suppression bias unit is configured.
[0016]
Next, the operation of the control device having the above configuration will be described. First, the actual MW signal 1 (MW) indicating the actual output at the power generation facility is corrected using the system frequency signal 3 for the MWD signal 2 (MW) of the output command value from the central power supply command station (this correction) The first subtracter 4 calculates the deviation subtracted from the contents of (1), which will be described later), and outputs a load increase / decrease command so that the analog memory 5 sets the load deviation to zero. The analog memory 5 is preset with a rate of change that allows the corresponding power generation equipment to follow the load stably. The analog memory 5 output is converted from a load deviation signal (MW) to a gas turbine rotational speed signal (% SPD) by a first gain setting device 6 and then transmitted to a second subtractor 7. .
[0017]
The actual rotational speed signal 25 (rpm) is converted into a speed signal (% SPD) by the second gain setting device 19, and the deviation from the rated rotational speed (100%) set in the constant setting device 21 is changed to the third. Is then transmitted to the second subtracter 7. The subtracter 7 subtracts the output of the third subtracter 20 from the output of the first gain setting device 6 and outputs the obtained deviation to the third gain setting device 8. The third gain setting unit 8 is set with the power generation equipment settling rate. After the input deviation (speed signal (% SPD)) is converted into the fuel amount command signal (FFD), it is sent to the adder 9. Output. The adder 9 adds the fuel command signal at the no-load rated speed set in the constant setter 10 to the input fuel amount command signal (FFD), and then transmits the fuel command signal to the low value selector 11.
[0018]
As described above, the low value selector 11 is supplied with the load limiter control signal 22 obtained by adding several percent to 10% of the load corresponding to the governor control signal from the adder 9 and the exhaust temperature of the gas turbine equipment. The adjusted exhaust gas temperature control signal 23 is inputted, the lowest value of the three signals is selected, and the gas turbine fuel related valve is controlled as the governor control command signal 24. Here, for example, when the actual MW signal 1 or the rotation speed signal 25 changes suddenly and the fuel command value increases rapidly, the load limiter control signal 22 is based on the addition signal corresponding to the aforementioned several percent to ten percent load. The purpose is to suppress excessive injection of fuel. The exhaust temperature control signal suppresses excessive fuel injection when the exhaust gas temperature exceeds a preset exhaust temperature value in response to a sudden rise in exhaust temperature that occurs when abnormal combustion occurs in the combustor of the gas turbine. It is intended.
[0019]
Next, a procedure for correcting the MWD signal 2 (MW) of the output command value from the central power supply command station using the system frequency signal 3 will be described. This correction is performed by the configuration within the broken line frame in FIG. 1, that is, the speed adjustment suppression bias means.
[0020]
The system frequency signal 3 is transmitted to the dead band setter 17 after removing minute (for example, about 0.01 to 0.03 Hz) frequency fluctuation components by the fluctuation suppression filter means 16. The dead zone setting device 17 suppresses wear due to minute operation of a target gas turbine power generation facility, for example, a fuel amount adjusting valve, a combustion air amount adjusting device or the like, or deterioration of a spring, and the like. A value suitable for reducing the remaining lifetime consumption is set. The output signal of the dead zone setter 17 is transmitted to the first-order lag element 15 via the rate-of-change setter 18 and is delayed by passing through the first-order lag element 15, and then biased to the MWD signal 2 by the adder 12. It is added as a signal.
[0021]
In the first-order lag element 15, a fuel command signal supplied to the gas turbine power generation facility, which is adjusted by increasing / decreasing the output deviation signal calculated by the first subtractor 4, is a stable operating condition of the facility. A time constant suitable to follow the load while maintaining the above is set. The output signal of the adder 12 is transmitted to the first subtracter 4 via the change rate setting unit 13. In the two change rate setting devices 13 and 18, a change rate value suitable for the operation state amount of the target gas turbine power generation facility to be within the stable allowable range is set manually by the suppression rate setting device 14. .
[0022]
The contents of the fluctuation suppression filter means 16 in FIG. 1 will be described below with reference to FIG. The system frequency signal 3 is converted into a rotation speed signal (% SPD) by the gain setting unit 26 and transmitted to the primary delay element 27, the switch 32 and the subtractor 28. The rotational speed signal, that is, the frequency signal, is converted into a small and gentle fluctuation by a time constant preset in the first-order lag element 27, and is then transmitted to the switch 32 and the subtractor 28. The The subtractor 28 subtracts the output signal of the gain setting unit 26 from the output signal of the first-order lag element 27 and outputs the calculation result to the comparator 30 via the absolute value calculator 29. The comparator 30 outputs a signal 0 when the input from the absolute value calculator 29 is less than or equal to a preset allowable set value of frequency fluctuation, and outputs 1 when the opposite is true. This output is input as a switching signal to the switch 32 via the dead time setting device 31.
[0023]
In the switch 32, when the signal from the dead time setter 31 is “0”, the input signal from the first-order lag element 27 is used, and when the signal is “1”, the signal from the gain setter 26 is used as the speed. Output as command signal 33 (% SPD). This speed command signal 33 (% SPD) is input to the dead zone setting device 17.
[0024]
By the above method, the following effects can be obtained.
[0025]
The function within the broken line frame in FIG. 1 is referred to as a speed adjustment suppression bias function. Fig. 3 shows the effect of the speed adjustment suppression bias function when the system frequency is increased, and Fig. 4 shows the effect of the speed adjustment suppression bias function when the system frequency is decreased. It shows about ratio.
[0026]
When the frequency is increased, the effect as shown in FIG. 3 is obtained. When the system frequency rises, the fuel amount command value to the gas turbine in the governor control system becomes a decrease signal, and this decrease signal operates at a rate of change set in advance in the rate of change setting unit 13. By this operation, the change in the fuel amount command value is delayed with respect to the target load, and the time difference from the change in the supply amount of combustion air is shortened. As a result, the premixed fuel-air ratio can change within the stable operation range of the low N0x combustor shown in the lower part of FIG.
[0027]
When the frequency drops, the effect as shown in FIG. 4 is obtained. When the system frequency decreases, the fuel amount command value to the gas turbine in the governor control system becomes an increase signal, and this increase signal operates at a change rate preset in the change rate setting unit 13. By this operation, the change in the fuel amount command value is delayed with respect to the target load, and the time difference from the change in the supply amount of combustion air is shortened. As a result, the premixed fuel-air ratio can change within the stable operation range of the low N0x combustor shown in the lower part of FIG.
[0028]
In the above process, as shown in the middle of FIG. 3 and FIG. 4, a slight deviation from the target load occurs. For example, in the case of the target multi-shaft combined power generation facility Therefore, by distributing the load deviation to a plurality of gas turbines, the load deviation in the entire power generation facility can be suppressed.
[0029]
Next, the effect of the fluctuation suppressing filter means will be described with reference to FIG. Normally, as shown in the upper diagram of FIG. 5, the input value of the system frequency signal 3 includes a slight fluctuation component in addition to a swell component having a large system frequency. When the signal including this minute fluctuation component is used as it is and used as the speed adjustment bias signal, the opening signal of the fuel amount control valve of the power generation equipment, particularly the gas turbine, and the combustion air amount adjusting means, etc. Since a minute operation component is also added to the control operation end operation signal, the movable parts such as the fuel amount regulating valve and the combustion air amount adjusting means are frequently operated with a small amount, and the remaining life consumption rate is increased. Therefore, the fluctuation suppression filter means filters the input system frequency fluctuation signal so as to obtain the waveform shown in the lower diagram of FIG. By this filtering, the control operation end operation signal is suppressed from instructing a minute operation, and the remaining life consumption rate of the movable part can be reduced.
[0030]
According to the present embodiment, the MWD signal 2 (MW) of the output command value from the central power supply command station is corrected using the system frequency signal 3, and the rate of change in the system frequency used for the correction is suppressed. The time difference between the change in the amount of fuel and the change in the amount of combustion air is reduced, and the fuel-air ratio is kept stable even in the process of changing the fuel amount according to the fluctuation of the MWD signal 2 and the system frequency. It becomes possible to maintain the range. Further, since the minute fluctuation component of the system frequency signal used for the correction is removed, the fine movement of the movable part of the fuel amount adjusting valve of the gas turbine and the combustion air amount adjusting means is reduced, and the life of these devices is extended. There is an effect.
[0031]
In the above embodiment, for example, when the speed adjustment suppression bias is operated during the load change operation of the plant, when the load fluctuates discontinuously due to the operation of the dead zone setter 17 in FIG. The set value of the dead zone setter 17 is set to a slope value (bias change rate) that does not exceed the speed regulation rate that is continuously instructed in advance to the target plant. By setting the set value of the dead band setting device 17 to the above-described value, it is possible to prevent the load from fluctuating discontinuously, and there is an effect of realizing smooth load followability.
[0032]
【The invention's effect】
According to the present invention, as described above, in the fuel amount control corresponding to the frequency fluctuation, the control with reduced speed adjustment sensitivity is performed so that the dynamic fuel-air ratio of the low N0x combustor satisfies the allowable value. As a result, it is possible to follow the frequency fluctuation due to a system fault or the like without impairing the operation performance of the power generation facility, which contributes to system stabilization.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a control device according to an embodiment of the present invention.
FIG. 2 is a block diagram showing the contents of fluctuation suppression filter means 16 shown in FIG.
FIG. 3 is a conceptual diagram showing an effect of speed adjustment suppression bias means when the system frequency is increased in the embodiment shown in FIG.
4 is a conceptual diagram showing an effect of speed adjustment suppression bias means when the system frequency is lowered in the embodiment shown in FIG.
FIG. 5 is a conceptual diagram showing the effect of the fluctuation suppressing filter means in the embodiment shown in FIG.
[Explanation of symbols]
1 Real MW signal (MW)
2 MWD signal (MW)
3 System frequency signal 4 1st subtractor 5 Analog memory 6 1st gain setter 7 2nd subtractor 8 3rd gain setter 9 Adder 10 Constant setter,
11 Low value selector 12 Adder 13 Change rate setter 14 Suppression rate setter 15 First order lag element 16 Fluctuation suppression filter means 17 Dead band setter 18 Change rate setter 19 Second gain setter 20 Third subtractor 21 Constant setter 22 Load limiter control signal 23 Exhaust temperature control signal 24 Governor control command signal 25 Speed signal (rpm)
26 Gain setter 27 Primary delay element 28 Subtractor 29 Absolute value calculator 30 Comparator 31 Dead time setter 32 Switch 33 Speed command signal (% SPD)

Claims (7)

The fuel amount command signal is adjusted so that the deviation between the power generation amount command signal of the gas turbine power generation facility and the actual power generation amount signal of the power generation facility is zero, and the power generation amount command signal is adjusted with the system frequency signal as an input. In a governor-free control method for a gas turbine power generation facility, a rate of change of the input system frequency signal is limited so as to reduce sensitivity to changes in system frequency, and the power generation amount command signal is generated by a signal with the rate of change limited. A governor-free control method for a gas turbine power generation facility, characterized in that   The gas turbine power generation facility governor-free control method according to claim 1, further comprising a step of removing a small fluctuation of a cycle equal to or less than a desired cycle contained in an input system frequency signal. A governor-free control method for a turbine power generation facility.   3. The governor-free control method for a gas turbine power generation facility according to claim 1 or 2, wherein the input system frequency signal is used for adjusting the power generation amount command signal after passing through a first-order lag element in which a dead time is set. A governor-free control method for a gas turbine power generation facility. The fuel amount command signal is adjusted so that the deviation between the power generation amount command signal of the gas turbine power generation facility and the actual power generation amount signal of the power generation facility is zero, and the power generation amount command signal is adjusted with the system frequency signal as an input. In a governor-free control device for a gas turbine power generation facility, the rate of change of the input system frequency signal is limited so as to reduce the sensitivity to changes in the system frequency, and the power generation amount command signal is generated by a signal with the rate of change limited. A governor-free control device for gas turbine power generation equipment, characterized in that a speed adjustment suppression bias means for adjusting the pressure is provided.   5. A governor-free control device for a gas turbine power generation facility according to claim 4, further comprising system frequency fluctuation suppression filter means for removing small fluctuations having a period equal to or less than a desired period contained in the inputted system frequency signal. A governor-free control device for gas turbine power generation equipment.   6. The governor-free control method for a gas turbine power generation facility according to claim 4 or 5, wherein the speed adjustment suppression bias means sets a dead time during which the input system frequency signal passes after the rate of change is limited. A governor-free control device for a gas turbine power generation facility, characterized by comprising a first-order lag element.   5. The governor-free control device for a gas turbine power generation facility according to claim 4, wherein the speed adjustment suppression bias means includes a dead band setter having a system frequency as an argument, and the dead band setter includes the gas turbine power generation unit. A governor-free control device for a gas turbine power generation facility, wherein a bias change rate that does not exceed a speed regulation rate preset in the facility is set.

Images