JP2001227361A - Power generation control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide safety operation in a system accident of a gas turbine power generating plant. SOLUTION: When a large accident current flows, a deviation signal from a subtracter 16 and a signal from a system frequency detector 15 become tolerances or more in comparators 19, 21, 23, and 25, and signals of a function setter 17 and a function setter 28 are selected in switches 18 and 29 and transmitted to an adder 31. The respective function setting outputs are adapted to counterbalance when being added together, so that the output becomes '0' and is inputted in change rate limiters 32 and 33. The output '1' of a logical multiplier 30 is transmitted to the switch 34, and the signal from the change rate limiter 32 is selected and outputted to an existing control system. When the system frequency rapidly decreases or increases, the signals of the system frequency detector 15 become the tolerance or more in the comparators 23 and 25, and the signals from the function setter 27 and the change rate limiter 32 are selected in the switch 29 and outputted to the existing control system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation control device for a gas turbine power plant in the event of a system failure, assuming grid-connected operation.

[0002]

2. Description of the Related Art Prior art relating to fuel control in the event of a system accident includes a gas turbine control device (Japanese Patent Laid-Open No. 11-229903).
Publication). This technical content includes a high output detection circuit that outputs a control signal when the output change rate of the generator is equal to or more than a predetermined value, and a unit that records an operation state a predetermined time ago. It is characterized in that the operating end is held in the operating state before the accident and is held in the power generation output signal before the accident.

[0003]

However, in the above-mentioned prior art, since it is necessary to always store each control operation end control signal before a certain period of time, the computer in the control device needs a large storage capacity. Thus, there is a problem that the storage capacity required during normal operation decreases. Further, there is a problem described below as an event occurring in the gas turbine fuel control at the time of a system accident. (1) The control device determines that a large fault current flows from the generator toward the fault point and the output of the generator has increased, and outputs a signal to decrease the fuel amount. If the accident point is separated in this state, the supply load against the demand load will be insufficient, and the fuel will increase rapidly, causing abnormal combustion inside the combustor and possibly causing a trip due to abnormally high exhaust gas temperature. There is. (2) When the system frequency decreases, the control device determines that the rotation speed has decreased, and outputs a signal to increase the fuel amount. If the accident point is separated in this state, the fuel will be rapidly reduced this time, and abnormal combustion will occur inside the combustor, possibly leading to a trip due to loss of fire. (3) When the system frequency increases, the control device determines that the number of revolutions has increased, and outputs a signal to decrease the fuel amount. When the accident point is separated in this state, the fuel is rapidly increased, and abnormal combustion occurs inside the combustor, which may cause a trip due to abnormally high exhaust gas temperature.

[0004] It is an object of the present invention to provide a power generation control device that copes with system disturbance that realizes stable operation when a system accident occurs in a gas turbine power plant on the premise of system interconnection operation.

[0005]

Means for Solving the Problems To solve the above problems, a means for detecting a fault current generated at the time of a system fault, and a load based on a deviation between a target load value of a plant and a generator output affected by the fault current. Means are provided for setting a variation width, and means for setting a fuel control signal bias based on a deviation between a frequency target value and a system frequency affected by the fault current. Here, the means for setting the load change width is provided with a restriction means for suppressing the change width of the fuel amount control signal so as to maintain stable combustion of the combustor of the gas turbine when an excessive load deviation signal is generated. . Further, the means for setting the fuel control signal bias is provided with a restriction means for suppressing a variation width of the fuel amount control signal so as to maintain stable combustion of the combustor of the gas turbine when an excessive frequency deviation signal is generated. .

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a power generation control device according to an embodiment of the present invention, and shows an example of application to a gas turbine power plant. Power generation will be implemented as follows. After adjusting the flow rate by the compressor inlet guide vanes 1, the air becomes high pressure and high temperature by the compressor 2 and is supplied to the combustor 3. After the flow rate of the fuel is adjusted by the fuel amount adjusting valve 7, the fuel is supplied to the combustor 3. In the combustor 3, high-pressure and high-temperature combustion gas is generated by a combustion reaction and supplied to the turbine 4. After the combustion gas is expanded in the turbine 4 and converted into the driving force of the rotating shaft 10,
Released as haiku gas. The generator 5 is connected to the rotating shaft 10, and the generator 5 generates electricity. The generated power is
The power is converted to power suitable for power system interconnection via the transformer / interrupter 8 and then transmitted to the power system 9.

Next, the control method will be described. The output of the power plant is controlled as follows. Generally, output control of a power plant is performed by a load command value (MWD: Mega Watt Dema) from a central power supply command center of a power company.
nd) and load control for adjusting the fuel amount to the gas turbine 4 so that the deviation between the output signal of the plant generator output detector 14 becomes 0. At that time, in order to synchronize the generated power with the signal of the system frequency detector 15 of the power system 9, governor control is performed so that the signal of the rotation speed detector 11 of the rotating shaft 10 is kept at an arbitrary speed. Furthermore,
In order to make the combustion temperature in the combustor 3 equal to or less than the allowable value of the material, the fuel control and the opening degree control of the compressor inlet guide blade 1 based on the signal of the exhaust temperature detector 13 are performed. Here, it is simpler to directly detect the combustion temperature, but the reliability is low when detecting the high-temperature gas temperature for a long time. Therefore, it is easy to obtain the combustion temperature uniquely from the relationship between the signal of the exhaust gas temperature detector 13 and the signal of the compressor discharge air pressure detector 12, and the method is highly reliable. Used for combustion temperature control. The control signal for the fuel amount adjusting valve 7 is generated by selecting a low value of each signal of the load control / governor control / exhaust gas temperature control.

[0010] Of the control methods, details of the control device 6 which is a feature of the present embodiment will be described with reference to FIG.
The MWD signal is output from the generator output detector 1 by the subtractor 16.
4 and transmitted to the function setting unit 17, the comparator 19 and the differentiator 20. In the function setting unit 17, a load bias with upper and lower limits is set with the output deviation as an argument. This bias set value is proportional to the output deviation, and upper and lower limits are set for, for example, ± 10% load. In the comparator 19, an allowable value of the output deviation corresponding to the system fault is set. If the output deviation value exceeds the allowable value, it is determined that the accuracy of the system fault occurrence is high, and the signal "1" is logically determined. The signal is transmitted to the summing device 22. The differentiator 20 calculates the rate of change of the output deviation and transmits it to the comparator 21. An allowable value of the output change rate corresponding to the system fault is set in the comparator 21,
If the rate of change exceeds the allowable value, it is determined that the probability of occurrence of a system fault is high, and a signal “1” is transmitted to the OR gate 22.
Output signals from the subtractor 16 and the function setting device 17 are transmitted to the switch 18, and the switching signal X 1
Is "1", the input value X1 is selected and transmitted to the adder 31. On the other hand, the signal from the system frequency detector 15 is
The signal is transmitted to the comparator 23, the differentiator 24, and the function setting device.
In the comparator 23, the frequency change width corresponding to the system fault is set as an allowable value. If the change width exceeds the allowable value, it is determined that the accuracy of the system fault occurrence is high, and the signal "1" is logically ANDed. To the vessel 26. The differentiator 24 calculates the rate of change of the frequency and transmits it to the comparator 25. An allowable value of the frequency change rate corresponding to the system fault is set in the comparator 25. If the change rate exceeds the allowable value, it is determined that the probability of the occurrence of the system fault is high, and the signal "1" is ANDed. 26. In the function setting unit 27, a load bias with upper and lower limits is set with the frequency change width as an argument. This bias set value is an inverse proportional function to the frequency change width, and upper and lower limits are provided for, for example, ± 10% load. Further, for example, the plant load ±
A dead zone is provided for the frequency change width equivalent to 5%. By setting the dead zone, an effect is obtained in which the fuel control system does not follow minute frequency fluctuations. The function setting device 27 and “0.
The signal from the constant setting device 26 to which "0" is set is transmitted to the switch 29. When the switching signal X1 from the AND device 26 is "1", the input value X1 is selected and transmitted to the adder 31. Here, the setting values of the function setting units 17 and 27 are characterized in that they are set to values that cancel each other out when the respective output signals are added. The change rate limiter 3
3 is set to a fuel amount change rate at which the combustor 3 in FIG. 1 can maintain stable combustion when the system is normal, that is, during normal load operation. In the change rate limiter 32, a limit fuel amount change rate at which no combustion abnormality occurs in the combustor 3 when a system abnormality occurs is set. The signals from the rate-of-change limiters 32 and 33 are transmitted to the switch 34, and the signal from the logical adder 22 and the signal from the logical product 26 are switched to "1" by the switching signal X1 via the logical product 30. When both the output deviation and the system frequency are abnormal, the input X1 is selected and transmitted to the existing control system. In the existing control system, the comparators 35 and 3
6, the output signal of the comparator 35 is set to "1" when the plant rises, and the output of the comparator 36 is set when the load drops.
Is transmitted to the analog memory 37 as "1". The plant load change rate value set in the constant setting device 38 is input to the analog memory 37, and is transmitted to the fuel control system as an opening signal of the fuel amount adjustment valve 7 in FIG. 1 according to the change rate.

The operation of this embodiment during operation will be described below. During normal operation, the operation is as follows. Subtractor 1
6 and the signal from the system frequency detector 15 are equal to or less than the allowable values in the comparators 19, 21, 23 and 25, the output signals of the OR gate 22 and the AND gate 26 become "0", At 18 and 29, the signals of the subtractor 16 and the constant setting unit 28 are selected and transmitted to the adder 31. The added signal is input to the change rate limiters 32 and 33. On the other hand, the signals from the logical adder 22 and the logical product 26 are output to "0" by the logical product 30 and transmitted to the switch 34 to select the signal from the change rate limiter 33 and output to the existing control system. I do.

[0010] When a large fault current flows from the generator toward the fault point, the following operation is performed. The deviation signal from the subtractor 16 and the signal from the system frequency detector 15 exceed the allowable value in the comparators 19, 21, 23, and 25, and the output signals of the OR gate 22 and the AND gate 26 become "1". , Switches 18 and 29, function setter 1
7 and the signal of the function setting unit 28 are selected and transmitted to the adder 31. Since each function setting output is set in advance so as to cancel out when added, the output becomes “0” and is input to the change rate limiters 32 and 33. Logical adder 22, Logical product 2
The signal from 6 is output as "1" by the logical AND unit 30, is transmitted to the switch 34, selects the signal from the change rate limiter 32, and outputs it to the existing control system.

When the system frequency rapidly decreases or increases, the following operation is performed. The signal from the system frequency detector 15 exceeds the allowable value in the comparators 23 and 25,
The output signal of the AND device 26 becomes “1”, and the switch 29 selects the signal of the function setting device 27 and transmits it to the adder 31. On the other hand, the signal from the subtractor 16 becomes equal to or less than the allowable value in the comparators 19 and 21, the output signal of the OR gate 22 becomes “0”, and the switch 18 selects the signal from the subtractor 16 and sends it to the adder 31. introduce. The added signal is input to the change rate limiters 32 and 33. The signals from the logical adder 22 and the logical ANDer 26 are output “1” by the logical ANDer 30, transmitted to the switch 34, select the signal from the rate-of-change limiter 32, and output it to the existing control system. .

[0012]

As described above, according to the present invention,
The following effects can be obtained without constantly storing the control operation end control signals before a certain time. (1) Even when a large fault current flows from the generator toward the fault point, operation according to the demand load can be performed, and occurrence of abnormal combustion inside the combustor can be suppressed. (2) When the system frequency is lowered, it is possible to suppress a rapid decrease in fuel and suppress occurrence of abnormal combustion inside the combustor. (3) When the system frequency increases, it is possible to suppress a rapid increase in fuel and suppress occurrence of abnormal combustion inside the combustor.

[Brief description of the drawings]

FIG. 1 is a power generation control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the contents of a new part of the control device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Guide vane at compressor inlet, 2 ... Compressor, 3 ... Combustor, 4 ...
Turbine, 5: Generator, 6: Control device, 7: Fuel amount adjusting valve, 8: Transformation / shutoff facility, 9: Power system, 10: Rotary shaft, 11: Rotation speed detector, 12: Compressor discharge air pressure Detector, 13: Exhaust gas temperature detector, 14: Generator output detector, 15: System frequency detector, 16: Subtractor, 17: Function setting device, 18: Switch, 19: Comparator, 20: Differentiator, 21: comparator, 22: OR, 23: comparator, 2
4 differentiator, 25 comparator, 26 logical product, 27 function setting device, 28 constant setting device, 29 switch, 30
AND, 31 ... Adder, 32 ... Change rate limiter, 33 ...
Rate-of-change limiter, 34 switch, 35 comparator, 36
Comparator, 37: Analog memory, 38: Constant setting device

Claims (5)

[Claims] 1. A power generation control device for adjusting an amount of fuel supplied so that an output load and a frequency of a gas turbine power plant become predetermined target values. Means for setting the load change width based on the deviation between the generator output affected by the fault current and the fuel control based on the deviation between the target frequency and the system frequency affected by the fault current Means for setting a signal bias. 2. The fault current detecting means according to claim 1, wherein the fault current detecting means detects a fault in the system from an absolute value and a change rate of a deviation signal between the load target value and a generator output affected by the fault current. A power generation control device including a function of determining and a function of determining a system abnormality from an absolute value and a change rate of a deviation signal between the frequency target value and a system frequency affected by the fault current. . 3. The method according to claim 1, wherein the means for setting the load change width includes a fuel amount control signal for maintaining a stable combustion of the combustor of the gas turbine when an excessive load deviation signal is generated. A power generation control device characterized by comprising a restriction means for suppressing a change width. 4. The gas turbine according to claim 1, wherein the means for setting the fuel control signal bias is capable of maintaining stable combustion of the combustor of the gas turbine when an excessive frequency deviation signal is generated out of an allowable range. The power generation control device according to claim 1, further comprising a restricting means for suppressing a change width of the fuel amount control signal, and a dead zone for suppressing a change in the fuel amount control signal due to a minute system frequency fluctuation. 5. The system according to claim 1, wherein when the fault current is detected by the fault current detecting means as a system fault, the sum of the signals generated by the means for setting the load change width and the means for setting the fuel control signal bias is provided. A power generation control device, wherein the power generation control device is adjusted in advance so that is zero.