JPH0454809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a load control device for a single-shaft combined cycle power generation plant, and more particularly to a load control device suitable for controlling train load change rate and train load upper and lower limits.

[Conventional technology]

Regarding load change rate control in combined cycle power plants, conventional equipment uses a function generator that outputs a signal indicating the limit of the load change rate of each axis, and a function generator that outputs a signal indicating the limit of the load change rate of each axis, as described in Japanese Patent Application Laid-Open No. 122710/1982. A load change rate limiter that adds the signal from the function generator to the load command signal of each axis, and a load change rate limiter on the plant side that adds the sum of the signals from the function generator of each axis to the load command signal of the entire plant. This makes it possible to set an appropriate load increase/decrease rate depending on the load condition.

[Problem that the invention seeks to solve]

However, this device does not take into consideration prevention of discontinuity in the output of the load change rate limiter when switching between automatic and manual load control for each axis.

Regarding governor free compensation, as described in Japanese Patent Application Laid-Open No. 122713/1982, conventional devices include a subtracter that subtracts the frequency bias signal from the load command signal of each axis, and a subtractor that subtracts the frequency bias signal from the load command signal of each axis. By providing an adder that adds to the command signal, the governor free portion can be used effectively.

However, with this device, the frequency bias signal is returned to the plant side as is, regardless of the upper and lower limit values on the shaft side, resulting in problems such as an increase in the deviation between the plant output command and the plant output, and unnecessary operation of the upper and lower limiters. It was hot.

[Purpose of the invention]

The purpose of the present invention is to prevent the output of the load change rate limiter on the plant side from becoming discontinuous when switching from automatic to manual or from manual to automatic for each shaft load control, and to prevent deviations between the plant output command and the plant output. It is an object of the present invention to provide a single-shaft type multi-cycle power plant load control device that can be made as small as possible and maintain good closed-loop load control on the plant side.

[Means for solving problems]

When switching the shaft load control from automatic to manual or from manual to automatic, the output of the rate of change limiter becomes discontinuous because the initial setting of the rate of change limiter when switching from automatic to manual is set to the actual output of the plant. It is for the purpose of doing.

The reason for using the actual output of the plant is to keep the deviation between the output command and the output of the plant as small as possible and to perform good closed-loop control on the plant side.

For example, if we consider a case where n axes are brought up to a predetermined load and then the load control is switched from manual to automatic one after another, the rate of change is initially set based on the actual output of the plant immediately before a certain axis is automatically turned on. The limiter value increases toward the rate limiter input (DPC or ALR setpoint) at a predetermined rate of change. At this time, the set values of the upper and lower limit limiters are determined by the values returned from each axis, but the output of the rate of change limiter is determined only by the DPC or ALR set value and the rate of change set value at that time. The set values of the upper and lower limiters are often exceeded. The actual plant output is controlled by the output of the upper and lower limit limiters, and in this state the deviation between the output of the rate of change limiter and the actual plant output increases. If the next axis is automatically turned on at this point, the rate of change limiter is initialized with the actual output of the plant, so the deviation from the value of the rate of change limiter immediately before the automatic turn-on appears as discontinuous.

This discontinuity, if its value is within the upper and lower limits, may result in a plant output command, and must be avoided at all costs.

As a countermeasure, it is sufficient to prevent the output of the rate of change limiter from exceeding the value of the upper and lower limit limiters. One possible method for this is to compare the output of the rate of change limiter with the set value of the upper and lower limit limiters using a monitor relay, and when the monitor operates, set the set value of the rate of change limiter to zero.

Furthermore, in order to avoid unnecessary operation of this monitor, minimize the deviation between the plant output command and the plant output, and improve load controllability, the AFC command and governor free compensation value are returned from the shaft side. The upper and lower limits shall be taken into consideration.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows the configuration of a single-shaft combined power generation plant.

In the figure, load command 2 from load control device 1
is connected to the gas turbine control device 4 and serves as a gas turbine fuel flow rate command 7 to control the control valve 10. The gas turbine 9 generates an output according to the given fuel flow rate using the generator 12. On the other hand, the high temperature gas turbine exhaust gas 11 is transferred to the exhaust heat recovery boiler 17.
and generates steam 15. This steam is transferred to the steam turbine 1 via the control valve 13 controlled by the control valve opening command 8 from the steam turbine control device 5.
8 and drives the generator 12 to generate output.

Now, the steam cooled in the condenser 19 becomes feed water 16 and is returned to the exhaust heat recovery boiler 17. This water supply flow rate is adjusted by a regulating valve 14 controlled by a water supply command from an exhaust heat recovery boiler control device 13.

The heat source in a combined power generation plant is the gas turbine only, and load control is achieved by controlling only the fuel flow rate of the gas turbine. The steam turbine operates in a so-called variable pressure operation, and the control valve 13 is kept fully open during normal operation.

FIG. 3 shows the control system of the load control device.

In the figure, load command 11 from the central power supply station
(hereinafter referred to as DPC) is matched with the series output 22 via a rate of change limiter 12 and an upper/lower limit limiter 16. The set value 13 of the change rate limiter is the sum of the change rates from the first axis to the nth axis. The adder 14 performs addition for this purpose. Similarly, the set value 18 of the upper and lower limit limiters is the sum of the upper and lower limit set values from the first axis to the nth axis.

The deviation 23 passes through an integrator 24 and becomes a load command 25 for each axis. This load command is passed through the rate of change limiter 28 and the upper/lower limit controller 32 to the output 3 of each axis.
4 and its deviation 36 is connected to the governor operating device 37.

If the load command 33 is larger than each shaft output 34, the output 38 from the governor operating device becomes a governor raising command and is sent to the governor setting device 39 of the gas turbine control device 4.
Increase the settings. Conversely, if the output of each axis is greater, the output 38 from the governor operating device becomes a governor lowering command.

The governor setting value becomes the fuel flow rate command 7, which controls the output of each axis.

The load control device can be divided into two parts: a common control section and each axis control section. In the figure, the parts surrounded by dashed lines are the respective shaft parts, and the rest are the common control parts.

The role of the common control unit is to distribute the DPC from the central power supply station as a load command to each axis, thereby unifying the multiple installed axes and operating them as if they were a single power plant.

Each shaft section plays the role of controlling the output of the shaft based on the load command given by the common control section. It is planned that the common control unit will be able to separate the load from the common control unit and control the load on the individual shaft as needed, such as when starting or stopping. This is the reason why the rate of change and upper and lower limit values are set for each shaft section, returned to common control, and used for power plant load control.

FIG. 4 explains how to return the rate of change and shaft output to the common control section.

When the load control of each axis is automatic, that is, the output of the axis is controlled based on the load command from the common control unit, the switch 263 changes the output at a predetermined rate of change (for example, 5
%/min) 261 to the common control unit Change rate 2
62. When each axis load control is manual, the zero change rate 265 is returned to the change rate 262.

The operation of the switch 401 is opposite to the above, and when each axis load control is automatic, the return axis output is set to zero 402.
In the case of manual operation, the actual output is the return shaft output.

FIG. 5 shows the contents of the rate of change limiter in the common section.

The deviation 127 of the added value 132 of the shaft output when the load control of the DPC and the shaft control section is in manual state is the changeover 1
26 to the rate of change limiter 129. The rate of change is given as the output of the adder 14, but since the return rate of change for axes with manual load control is zero, it is the sum of the load change rates of axes with automatic load control. The output 130 of the rate of change limiter is again added to the added value 132 in an adder 131 and becomes the input 15 to the upper and lower limit limiters.

When switching the load control of each axis from automatic to manual or from manual to automatic, it is necessary to instantaneously initialize the rate of change limiter 129. As mentioned above, if the load control of each axis is manual, that axis is regarded as an uncontrollable axis, and the plant side stops adding the return change rate of the relevant axis, and the shaft output of the relevant axis is reduced. This is directly added to the output of the rate of change limiter 129, and this operation prevents the deviation between the output command value and the actual output from increasing and allows smooth load control on the plant side.

This initial value setting is performed by the switch 126. That is, at the moment when the control of a certain axis is switched from automatic to manual or from manual to automatic, the switch 126 connects the deviation 133 to the input 128 of the rate of change limiter 129 instead of the deviation 126 described above. The deviation 133 is the value obtained by subtracting the sum 59 of the AFC and governor free compensation of each axis from the plant output and the sum 135 of the shaft output 132 of the load control manual shaft.

The reason why the actual output of the plant is used here is that it is the most suitable value for the purpose of setting the initial value of the rate of change limiter described above.

Furthermore, the reason why AFC, governor free compensation value, and shaft output are subtracted is because these are all added on the exit side of the rate of change limiter.

FIG. 1 will be explained first from the shaft side (within the dashed line). Note that descriptions that overlap with those in FIGS. 2 to 5 will be omitted.

The AFC signal 50 for each axis and the governor free compensation signal 31 are added by an adder 52, and its output 53 is connected to an adder 55. The purpose of this is to first enable the AFC command and governor free compensation for each axis, and the output 56 of the adder 55 becomes the sum of the shaft side output command 29, the AFC command value, and the governor free compensation value.

In order to match the load control on the plant side, it is necessary to return the AFC command value and governor free compensation value on the shaft side to the plant side, but the values that are valid on the shaft side, that is, the AFC command value and the governor Instead of returning the total free compensation value as it is, the difference 54 between the output 33 of the upper and lower limit limiter 32 on the shaft side and the output command 29 on the shaft side is calculated by a subtracter 57 and returned.

As a result, it becomes easier to match the plant output command with the plant output, improving load controllability on the plant side.

Further, unnecessary operation of the upper and lower limit limiters on the plant side can be prevented by the AFC command value returned from the shaft side to the plant side and governor free compensation.

Next, the plant side will be explained.

An adder 131 adds the output 130 of the rate of change limiter 12 and the shaft output 132 of the load control manual shaft, and outputs the sum 59 of the AFC command value and governor free compensation value returned from the shaft side to the output 15. are added by an adder 63. The output 60 of the adder 63 becomes the plant output command value 20 via the upper and lower limit limiter 16. Monitor relay 61 is adder 131
The output 15 of the output 15 is compared with the set value 18 of the upper and lower limit limiter, and if the output 15 becomes larger than the upper limit set value, the increasing rate of change of the rate of change limiter 12 is set to zero, and the output 15 is set to the lower limit set value. If it becomes smaller, the rate of change on the down side is set to zero.

That is, when the monitor relay 61 operates, the output 62 of the monitor relay switches the switch 63 to the a side and changes the rate of change set value 6 to the rate of change limiter 12.
4 is changed from the normal setting value of 13 to zero. At this point, the rate of change limiter becomes an output hold state and maintains this state until the monitor relay 61 is deactivated.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to eliminate discontinuity in the rate of change limiter when switching load control from automatic to manual or from manual to automatic.

Further, according to the present invention, unnecessary operation of the rate of change limiter can be prevented and load control characteristics on the plant side can be improved.

[Brief explanation of the drawing]

Figure 1 is a control system diagram of the load control device, Figure 2 is a diagram showing the configuration of a single-shaft combined cycle power plant, Figure 3 is a control system diagram of the load control device, and Figure 4 is load control automatic←→manual switching. FIG. 5 is a diagram showing the operation of the rate of change limiter. 61... Monitor relay, 63... Switching device, 5
7...Subtractor.

Claims (1)

[Claims] 1 A first rate of change limiter 12, a first adder 131 that adds the output of each axis to the output of the first rate of change limiter, and a first adder 131 that adds the output of each axis to the output of the first rate of change limiter, and a
A second adder 63 that adds the AFC command and the governor free compensation value, a first upper and lower limit limiter 16 for the output of the second adder, and an output of the first upper and lower limit limiter and a plant output. Subtractor 21 that matches
and a regulator 24 that performs closed-loop control based on the output of the subtracter, and a monitor 61 that compares the output of the first adder 131 and the set value of the first upper/lower limit limiter 16; A first load control device includes a switch 63 that switches the set value of the first rate of change limiter 12 to a normal set value by the operation of a monitor, and a second load control device that controls the rate of change of the output of the regulator 24. a rate-of-change limiter 28, an adder 55 that adds the AFC command and governor free compensation to the output of the second rate-of-change limiter, and a second upper and lower limit that limits the output of the adder. a subtracter 57 that outputs the deviation between the output of the second upper and lower limit limiter 32 and the output of the second rate of change limiter 28;
and a second load control device that connects the output of the subtracter to a second adder 63 of the first load control device.