JP2000204906A - Overload preventing device for transmission line capacity in thermal power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue an optimum load operation by detecting the capacity-over of a transmission line to generate a transmission line run back, reducing a boiler load and a turbine master upper limit value, and reducing the pressure set bias value of a turbine bypass valve to perform the main steam pressure control in the turbine inlet. SOLUTION: When a transmission line run back signal is detected, a transmission line run-back signal 2 is generated in the same level as a boiler run-back signal 1, and transmitted to each signal switch 3, 9 through an OR gate 29 and to a signal switch 19 directly, respectively. The boiler load command to which a main steam pressure controller command 6 is added by an adder 7 is forcedly switched to a boiler load command corresponding to the transmission line allowable load generated in a signal generator 8 through the signal switches 30, 3 to quickly reduce the boiler load. On the other hand, in turbine master control, also, a generator load control command 10 is switched to a main steam pressure control command 11 by the signal switch 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the operation of thermal power plants in Japan and overseas with limited transmission line capacity.
Regarding thermal power plant automatic control equipment, especially by introducing a transmission line run-back function to the thermal power plant automatic control equipment, even if the capacity of the transmission line is exceeded, optimal load operation is automatically performed. The present invention relates to an overload prevention device for a transmission line capacity that can be continued.

[0002]

2. Description of the Related Art Conventionally, automatic control devices for thermal power plants include a boiler run-back function for preventing overload operation of auxiliary equipment, a method for reducing the degree of vacuum in a condenser or a decrease in main steam pressure. Although there is a turbine runback function for the purpose of protecting turbines, most of the automatic control devices actually used in transmission lines that transmit electricity generated from generators are considered in consideration of overload prevention. Absent.

[0003] For this reason, in a thermal power plant limited by the capacity of the transmission line, the operator has to manually monitor an abnormal situation while monitoring the operating condition one by one.
Particularly in overseas thermal power plants, there are many cases where the power system is unstable or a transmission line trouble occurs. In such a case, the operator is required to have instantaneous judgment ability and excessive labor, but it is difficult to safely and reliably perform operations requiring skill.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention introduces a transmission line run-back function into an automatic control device of a thermal power plant, so that even if the capacity of the transmission line is exceeded, the automatic It is an object of the present invention to provide a transmission line capacity overload prevention device capable of continuing optimal load operation.

[0005] Generally, runback is a method of rapidly reducing the load and protecting equipment in order to prevent overload operation.
Equipment (auxiliary equipment) related to plant operation during normal load operation
However, when the reduction allowable amount is exceeded for some reason, it refers to an operation of rapidly reducing the load to the allowable capacity of the target device. A thermal power plant has a boiler runback and a transmission line runback, and it is necessary to operate the transmission line so that the current during load operation does not exceed the rated capacity. When the power transmission capacity is exceeded during operation, the operation of suddenly reducing the load is called transmission line runback.Boiler runback is a condition in which an abnormality occurs in a boiler auxiliary during a load operation and a trip occurs. In this case, it refers to the operation of rapidly reducing the boiler load to the capacity of the remaining operating accessories.

[0006]

According to the first aspect of the present invention,
In an automatic controller for a thermal power plant that has introduced a transmission line runback function, a transmission line runback is generated based on a detection signal of a transmission line overcapacity, and the boiler load and turbine master upper limit value are adjusted to the transmission line allowable load. The method is characterized in that the operation is forcibly switched to a narrowing-down operation, and the pressure setting bias value of the turbine bypass valve is lowered to control the main steam pressure at the turbine inlet.

[0007] According to the invention, by introducing the transmission line run-back function to the automatic control device of the thermal power plant, even if the capacity of the transmission line is exceeded, the optimum load operation is automatically continued. Therefore, the turbine master command and the boiler load command are reduced to the allowable load of the transmission line, and the turbine bypass valve command controls the main steam pressure at the turbine inlet, thereby improving the reliability of the thermal power plant, and Operator labor can be reduced.

According to a second aspect of the present invention, there is provided an automatic control system for a thermal power plant in which a transmission line run-back function is introduced. The throttle control of the turbine valve is performed by forcibly switching from the governor control signal to a governor setting signal corresponding to the transmission line allowable load.

According to the present invention, since the processing is performed by making use of the good generator load response of the turbine governor control, it is possible to quickly narrow down to the transmission line allowable load in a short time.

According to a third aspect of the present invention, in an automatic control apparatus for a thermal power plant having a transmission line run-back function, a transmission line run-back is generated based on a detection signal indicating that a transmission line has exceeded its capacity. It is characterized in that the operation is forcibly switched to an operation of reducing the boiler load to a load equivalent, and the supply of fuel to the burner is cut off or controlled in accordance with the boiler load.

According to this invention, in order to more stably control the combustion of the boiler as compared with the first invention, by incorporating the transmission line run-back signal into the automatic burner control, it is possible to further optimize the boiler load. The fuel can be cut off.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, the dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention, but are merely illustrative examples.

First Embodiment FIGS. 1 and 2 show an automatic control apparatus for a thermal power plant according to a first embodiment of the present invention, in which a transmission line run-back function as a basic form of the present invention is introduced. FIG. 1 is a basic flow chart, and FIG.
The outline block diagram of the boiler automatic control apparatus corresponding to 4) is shown. First, when the current of the transmission line becomes equal to or higher than the rating, an overcapacity (overcurrent) of the transmission line is detected (S1). At this time,
The transmission line runback signal is output to the automatic boiler control device (S4) (S2), and an alarm message is generated so that the operator can determine that the capacity is exceeded (S3).

The transmission line run-back signal is transmitted to the turbine automatic controller (FIG. 4) in the boiler automatic controller (S4).
It is output simultaneously to the burner automatic control device (FIG. 6). The automatic turbine control and automatic burner control will be described later.

In the automatic boiler control device (S4), the boiler master receives the runback signal and shifts to automatic standby, and lowers the boiler load command to a level corresponding to the allowable load of the transmission line (S5). At this time, the turbine master performing the generator output control shifts from the cooperative control to the turbine follow control, and limits the upper limit value of the controller to the transmission line allowable load (S7).

At the same time, the run-back signal is also sent to a turbine bypass valve provided in a turbine bypass system in which the excess main steam in the boiler bypasses the turbine and is sent directly to the condenser when the load suddenly decreases, forcing the bypass valve to operate. The automatic opening control is performed, in other words, the pressure setting bias value is reduced to control the main steam pressure at the turbine inlet to prevent the main steam pressure introduced to the turbine from rising in response to the sudden load decrease.
(S6)

FIG. 2 is a circuit block diagram corresponding to the boiler automatic control operation shown in FIG. In the figure, 21, 2
“Δ” indicated by 3, 26 is a deviation detector, 6, 10, 11,
“PI” shown by 16 is a proportional integrator, “Σ” shown by 7 is an adder, “fχ” shown by 5 is a function generator, 25 is an adder,
"SG" indicated by 8, 12, 14, 15, 24 is a corresponding signal generator, "T" indicated by 3, 9, 28, 30, 19 is a signal switcher, and 29 is an OR gate.

In such a configuration, when the transmission line run-back signal is detected in the automatic boiler control device, the same level as the conventional boiler run-back signal 1 is detected.
The transmission line runback 2 is generated and transmitted to the switches 3 and 9 through the OR gate 29 and directly to the switch 19 without passing through the OR gate 29, and predetermined signal switching described later is performed. That is, in the normal operation, the boiler master control obtains a deviation between the main steam pressure setting signal 22 and the actual main steam pressure 13 by the deviation device 23, and proportionally integrates the deviation signal by the proportional integrator 6. The obtained main steam pressure controller command is added by the adder 7 and the signal switch 3
The boiler load command is obtained by adding the main steam pressure controller command 6 in the adder 7 by the signal switch 3 when the transmission line run-back signal is detected. Then, the boiler load command generated by the signal generator 8 and corresponding to the transmission line allowable load 8 is forcibly switched via the switches 30 and 3 to rapidly narrow the boiler load.

On the other hand, in the normal operation of the turbine master control as well, the deviation between the generator load command signal 4 and the actual generator output 20 is determined by the deviation device 21, and the deviation signal is proportionally calculated by the proportional integrator 10. The generator load control command obtained by the integration is transferred to the turbine master command 3 via the signal switch 9.
However, when the transmission line run-back signal 2 is detected, the signal switch 9 switches from the generator load control command 10 to the main steam pressure control command 11.

That is, the deviation signal obtained by the deviation unit 23 is proportionally integrated by the proportional integrator 11 and the main steam pressure control command 11
And the control command 11 is set as a turbine master command 34 via the signal switch 9. At this time, the main steam pressure control 11
At the same time, the controller upper limit signal 12 generated by the signal generator 12 is sent to the proportional integrator 11 via the switch 28, and the main steam pressure control command 11 is limited to the transmission line allowable load 8, and Perform load prevention.

During normal control operation, the turbine bypass control changes the pressure setting bias value (signal generator 14) added to the main steam pressure setting 13 via the switch 19 and the adder 25 to the transmission line run back. When the signal 2 is detected, a transmission line run-back function is provided to switch the signal switch 19 to the signal generator 15 side to rapidly decrease the pressure setting bias value 15 downward. The reason why the transmission line runback 2 and the boiler runback 1 are arranged in parallel by an OR gate is as follows.
In the case of transmission line runback, the boiler load must be rapidly reduced to almost the same level as that of the boiler runback, so that a similar function is required for the control circuit.

[Second Embodiment] FIG. 3 shows a flow of a transmission line run-back control of an automatic turbine control device as a second embodiment, and FIG. 4 shows a schematic block diagram of a turbine automatic control logic of this embodiment. . As shown in FIG. 3, the transmission line runback signal is also output to the turbine automatic control device (S11) in the boiler automatic control device (S4) at the same time.
The governor setting is narrowed down to the transmission line load by the turbine governor control (S12).

This operation will be described in more detail with reference to FIG. 4. In the figure, reference numerals 53 and 55 denote low value selection circuits, 42 denotes an adder,
Reference numeral 4 denotes a switch, and 57 denotes a signal generator for generating a signal corresponding to a power transmission allowable load. In such a configuration, in a normal operation, a turbine governor command 51 and a load limiter command 52 to which the speed control signal is added are generated by the adder 42 based on the turbine master command, and the two signals 51,
Numeral 52 denotes a low value selection circuit 53, and the lower value becomes a turbine valve command 54. In this embodiment, a low value selection circuit 55 is provided downstream of the load limiter command 52, and the switch 44 is provided. The transmission line allowable load-equivalent signal generated by the signal generator 57 via the signal generator 57 can be input to the low value selection circuit 55.

According to this configuration, the transmission line run-back 2
Occurs, the switch 44 is forcibly switched to the signal generator 57 side to limit to the command 57 corresponding to the permissible load of the transmission line via the low value selection circuits 55 and 53. Reduce the governor setting to the equivalent of the transmission line load and reduce the generator load. In this embodiment, the automatic boiler control unit of the first embodiment shown in FIGS. 1 and 2 is provided with automatic turbine control (forcible switching based on the low value selection circuits 55 and 53 based on the transmission line runback 2 signal) ( The content of the boiler automatic control unit is as shown in the embodiment of FIG.

In the first embodiment, the process is performed by the turbine automatic control device because the process is performed through the turbine master control (S18). However, in the present embodiment, the power generation by the turbine governor control (S19) is performed. Since the processing is performed taking advantage of the good machine load responsiveness, it is possible to rapidly narrow down to the transmission line allowable load in a short time.

[Third Embodiment] FIG. 5 shows the flow of the transmission line run-back control of the automatic burner control device as a third embodiment, and FIG. 6 shows a schematic block diagram of the burner automatic control logic of this embodiment. . As shown in FIG. 5, the transmission line run-back signal is simultaneously output to the automatic burner control device (S21) in the automatic boiler control device (S4), and is automatically adjusted in accordance with the boiler load narrowed down by the boiler master control. By optimally shutting off or supplying fuel to the burner (S22), optimal fuel control is performed up to the transmission line load. (S23)

This operation will be described in more detail with reference to FIG. 6. In FIG. 6, reference numeral 29 denotes an OR gate, 62 denotes an AND gate, and a coal burner is used as a burner. This circuit uses the OR gate 29 so that the transmission line run-back signal is extracted at the same level as the boiler run-back signal 1, and if the coal burner is operating (63), the coal burner run-back command (64) is allowed. And an AND gate 62 is used. When the coal burner run-back command 64 is permitted, an ignition torch forced ignition command 65, a first coal burner cutoff command 66, and if necessary, a second coal burner cutoff command 67 are generated. As shown in FIG. 5, the burner automatic control device (S
46) performs optimal combustion control after receiving the boiler master control unit signal (S47). (For example, if 50% burner shutoff is performed by boiler master control, 50%
Combustion (fuel oil, air flow rate, etc.)
Let CC do it. )

Although the third embodiment combines the automatic boiler control (S4) of the first embodiment with the automatic burner control (S46), it is also possible to configure the automatic burner automatic control alone. This embodiment incorporates a transmission line runback signal into the automatic burner control of FIG. 5 in order to more stably control the combustion of the boiler as compared with the first embodiment, so that the optimum fuel suitable for the boiler load can be obtained. Blocking can be performed.

[0029]

As described above, according to the present invention, even in a thermal power plant in which the capacity of the transmission line is limited, the operator can automatically monitor the plant when an abnormal situation occurs without monitoring the operation status. It is possible to bring the generator load to a safe state. In addition, in thermal power plants overseas, the power system is often unstable or transmission line troubles occur in many cases, requiring instantaneous judgment ability and excessive labor for operators. Since the overload of the transmission line capacity can be detected and the load can be controlled to a value corresponding to the capacity, the burden on the operator can be reduced.

Further, in the thermal power plant, first, reliability is required. In the present invention, automatic control in step with boiler control / turbine control can be realized for the problem related to transmission line overload. As a result, safe operation of the plant is achieved and reliability is improved. Further, when the transmission line run-back function of the present invention is introduced, an automatic control device constituted by software logic is only required to add logic, so that the cost is low.

According to the second aspect of the present invention, since the processing is performed by taking advantage of the good generator load response of the turbine governor control, it is possible to rapidly narrow down to the transmission line allowable load in a short time. Can be.

According to the third aspect of the present invention, in order to control the combustion of the boiler more stably as compared with the first aspect of the present invention, the transmission line run-back signal is taken into the automatic burner control.
Further, it is possible to perform the optimal fuel cutoff corresponding to the boiler load.

[Brief description of the drawings]

FIG. 1 and FIG. 2 show an automatic control device for a thermal power plant according to a first embodiment of the present invention in which a transmission line run-back function as a basic form of the present invention is introduced, and FIG. The figure is shown.

FIG. 2 is a schematic block diagram of a boiler automatic control device corresponding to (S4) of FIG.

FIG. 3 is a flowchart illustrating a flow of transmission line run-back control of the automatic turbine control device as a second embodiment of the present invention.

4 shows a schematic block diagram of the turbine automatic control logic of the embodiment of FIG.

FIG. 5 is a flowchart showing the flow of transmission line run-back control of an automatic burner control device as a third embodiment of the present invention.

6 shows a schematic block diagram of the burner automatic control logic of the embodiment of FIG.

[Explanation of symbols]

 5 Function Generator 6, 10, 11, 16 Proportional Integrator 7 Adder 8, 12, 14, 15, 24 Signal Generator 3, 9, 19, 28, 30 Signal Switcher 21, 23, 26 Deviation Detector 25 Adder 29 OR gate

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (3)

[Claims] 1. An automatic control device for a thermal power plant that incorporates a transmission line run-back function, wherein a transmission line run-back is generated based on a detection signal of an excess capacity of a transmission line,
While forcibly switching to an operation to narrow down the boiler load and turbine master upper limit to the permissible load of the transmission line,
An overload prevention device for a transmission line capacity in a thermal power plant, wherein a pressure setting bias value of a turbine bypass valve is reduced to control main steam pressure at a turbine inlet. 2. An automatic control device for a thermal power plant having a transmission line run-back function, wherein a transmission line run-back is generated based on a detection signal of an excess capacity of a transmission line,
An apparatus for preventing overload of a transmission line capacity in a thermal power plant, wherein throttling control of a turbine valve is performed by forcibly switching from a normal turbine governor control signal to a governor setting signal corresponding to a transmission line allowable load. 3. An automatic control device for a thermal power plant that incorporates a transmission line run-back function, wherein a transmission line run-back is generated based on a detection signal of an excess capacity of a transmission line,
In addition to forcibly switching to an operation to reduce the boiler load to the permissible load of the transmission line, shutting off or controlling the supply of fuel to the burner in accordance with the boiler load is performed. Load protection device.