JPH0379901A - Control of boiler output in emergency - Google Patents

Abstract

PURPOSE:To stabilize the operation of a boiler by opening suddenly a turbine bypass valve when the pressure of main steam rises beyond a control range and at the same time suppressing a change in the input to a boiler by adding the flow rate value in the turbine bypass to actual amount of power generation. CONSTITUTION:A the time of the sole operation of the system, etc. when the unit load drops a good deal, the pressure of main steam rises generator 12 bypass a proportional, integration device 11 by 100% opening signal of a signal generator 4d, and then it passes a switching relay 3d and opens suddenly a turbine bypass valve 13. On the other hand, the standard of boiler input is in non-cooperative control mode so that it becomes an actual amount of power generation, but the turbine bypass valve 13 is open, and the amount of steam passing the turbine bypass valve is added to the actual amount of power genera tion by an adder 2e. When, after the transfer of load variation is completed, the pressure of main steam of the boiler becomes gradually settled, and the deviation becomes small, the switching relay 3d and variation rate limiter 7b operate, and the flow rate in the turbine bypass to which the amount of actual power generation has been added is subtracted by a subtractor 1d.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a boiler output adjustment method in an emergency in a boiler-turbine cooperative control device that controls the outputs of the boiler and turbine using the same command signal. The present invention can be applied to a boiler output control device that performs isolated operation within a power plant, a boiler output control device that performs grid frequency fluctuation operation, a boiler output control device that performs grid isolated operation, etc.

(Prior art) The conventional boiler output 9A section method calculates the main steam pressure from a value determined by the power generation command or the actual power generation amount, inputs it to a proportional calculator and an integrator, and calculates the residual value. The power generation amount command (fuel amount command) is determined by the value of .

Water supply amount command, air amount command) were revised and boiler input commands were created. FIG. 2 is a system diagram showing an example of such a conventional boiler output adjustment method.

First, the functions of the constituent elements will be explained. (la), (I
b) is a subtractor that calculates $ from two inputs, (2a),
(2 inputs), (2c) (2d> is an adder that adds two inputs, (3a), (3b).

(3c) is a switching relay that selects input a while the input condition is satisfied. (4a) and (4b) are signal generation 'in,
(5) is an integrator, and (6) is a proportional calculator. (7a
) is a rate-of-change limiter that outputs a fixed rate of change until it becomes equal to the input when the input changes significantly, (
8) is a function generator that programs the output in response to the input signal. (9) is a low selector that selects and outputs the lower one of two inputs, and 0ω is a high selector that selects and outputs the higher one of two inputs.

Next, the interaction of each component will be explained. From ff1ffi
If the command and the actual power generation amount match, and furthermore, the actual main pressure and the set main steam pressure match, the boiler output and input match. The power generation command is input to the function generator (8), and then becomes the output of the rate of change limiter (7a).
This becomes the boiler main steam setting value. The deviation between this main steam pressure set value and the actual main steam pressure is obtained by the subtractor (1a). This deviation is calculated by the proportional calculator (6) and the integrator (5).
The result is calculated in the adder (2a), (
Emitted in 2b)? It is added to the Ii quantity command to become the combustion quantity command, water supply quantity command, and air quantity command of the boiler request input.

If the power generation command is larger than normal, the main turbine
The governor operates rapidly and greatly, but as a result of this operation, a difference (main steam pressure deviation) occurs between the main steam pressure set value and the actual main steam pressure. This main steam pressure deviation is detected by the signal generator (4a)
Or a value exceeding the value x1 or x2 determined in (4b) becomes the output of the adder (2c) or (2d) and is input to the low selector (9) or high 'JA selector 00). ,
It is compared with the power generation amount deviation which is the output of the subtractor (1b), and if it is larger than the power generation amount deviation, it becomes the output to the main turbine governor. That is, the main turbine governor operates to modify the main steam pressure.

In this way, conventionally, while compensating for the delay in boiler output relative to boiler input using the main turbine governor,
I was trying to maintain a stable boiler output.

In addition, when the unit is not operating normally, such as due to fluctuations in the power system frequency, isolated operation within the station when only the power load is within the power plant, or isolated operation when only the local load is present, the boiler and turbine are controlled separately in non-cooperative control mode. In , the base of the boiler output is the actual power generation amount, and the switching relay (3b)
The actual power generation wall is selected by

[Problem to be solved by the invention]

The conventional method can be used without any problem if the maximum variation range of the power generation command is 3 to 4% of the rated load. However, if the power grid frequency changes significantly for some reason, if the power generation unit is disconnected from the entire power grid and operates with only a local load, or if the power plant is operated with a single load, etc. The power generation unit had come to an emergency stop due to limit values such as , main steam pressure, fuel ml, etc.

The cause of high main steam pressure is high power generation load (1
When the load rapidly decreases from 00X rated output to 25% load, the main turbine governor rapidly opens to a low degree (fully closes for about 1 to 2 seconds), and the boiler output becomes surplus. One example of this is that the main steam pressure increases rapidly. A turbine bypass valve is provided at the turbine inlet to absorb this pressure increase. However, this turbine bypass valve only had the function of a safety valve, opening when main steam pressure rose and closing when it fell.

When the power grid frequency changes or when the grid is operating independently, the power generation command, which is the required load, does not hold, and the main turbine operates according to the grid frequency, and the boiler must operate using only the main steam pressure as an indicator. No. This operation is generally called boiler follow operation. In such cases, using only the conventional main steam pressure correction circuit, it takes 2 to 3 minutes from the time the boiler input changes until the output appears, and it cannot keep up with the operation of the rapidly operating main turbine governor. The boiler power after 3 minutes results in the main turbine power being changed. That is, the outputs of both the boiler and the turbine do not match, resulting in an unstable situation, and in some cases, the power generation unit may come to an emergency stop.

[Means for Solving the Problems] In order to solve the above-mentioned conventional problems, the present invention provides boiler-turbine cooperative control that has a function of adjusting the boiler input according to the deviation of the main steam pressure. When the steam pressure rises above the specified value, the turbine bypass valve is rapidly opened and then controlled to a constant value, and the turbine bypass exhaust flow rate is added to the power generation amount that is the boiler input command, and then the main steam pressure returns to the specified value. This paper proposes a boiler output adjustment method in an emergency, which is characterized by forcibly gradually reducing the turbine bypass amount and bringing the main steam pressure to a value determined by the actual power generation amount. .

[Function] In the present invention, in the case of a unit operation in which the load on the boiler must be reduced to a tight bag, such as when transitioning to system isolated operation, the turbine bypass valve, which only has the function of an on/off safety valve, is replaced with a turbine bypass valve of the boiler. The boiler is stabilized by operating in coordination with the output and at the same time determining the input to the boiler in consideration of the air flow of the turbine bypass.

[Example] FIG. 1 is a system diagram showing an example of the method of the present invention. In this embodiment, in addition to the conventional boiler output gI ffff system explained with reference to FIG. An adjustment system that adds meteors has been added. Therefore, in order to avoid redundancy, the same parts in FIG. 1 as in FIG. 2 are given the same reference numerals and detailed explanations will be omitted.

In FIG. 2, the functions of each added component are as shown below. (lc), (ld) are (la
).

Similar to (1b), a subtractor that calculates fIi on two inputs, (
2e) is (2a), (2b), (2c),
Similar to (2d), an adder that adds two inputs, (3d
), (3e) is (3a), (3b), (3
Similar to c), the switching relay selects input a while the input condition is satisfied, (4c) and (4d) are (4a) and (4b).
It is also a signal generator. (7b) is similar to (7a),
This is a rate-of-change limiter that outputs an output at a predetermined rate of change when the input changes significantly until it becomes equal to the input. (1
1) is a proportional/integrator, 021 is a 1-pulse generator that generates 1 pulse upon receiving the signal from the signal generator (4d), and Q
3) is a turbine bypass valve.

In such a system, correction of the boiler input due to the main steam pressure deviation during normal load changes is performed in the same manner as the conventional method explained with reference to FIG. 2 above.

When the unit load decreases significantly, such as when the system is operating independently, the main steam pressure increases significantly. At this time, when the value exceeds the value determined by the signal generator (4c), the turbine bypass valve 03) is opened by the proportional/integrator (11), but in order to open rapidly, if the value exceeds the predetermined value. (
Setting Hanyu α), the pulse output from the I pulse generator (+2) by the 100χ opening signal of signal generation 2H (dd) bypasses the proportional/integrator (II) and is activated by the switching relay (
3d) and rapidly open the turbine bypass valve 03). After one pulse generator time elapses, the proportional/integrator (If
) becomes the input to the turbine bypass valve 03).

On the other hand, the reference for boiler input is the actual power generation amount because it is in non-cooperative control mode, but the turbine bypass valve 03) is open and the steam passing through the turbine bypass valve 'rRm
is added to the actual power generation amount by an adder (2e). After the load change transition is completed, when the main steam pressure of the boiler gradually settles and its deviation becomes smaller, the switching relay (3d) and rate of change limiter (7b) operate and the pressure is added to the actual power generation amount. The turbine bypass flow rate that is present is subtracted by a subtractor (ld).

The switching relay (3e) of the main turbine governor is switched to the (b-c) side so that correction of the main steam pressure by the turbine does not operate in such an emergency.

[Effects of the Invention] In the method of the present invention, in order to prevent boiler trips due to high boiler main steam pressure when there is a large and rapid change in engine output, the turbine bypass valve is opened rapidly and at the same time a turbine bypass meteor is generated. In addition to increasing power generation, it also suppresses changes in boiler input. This specifically provides the following effects.

1) Since the input value of the boiler does not decrease, the boiler feed water does not become low.

2) Similarly, due to a decrease in boiler input value, conventionally
As a result of the boiler output decreasing appearing after 3 minutes, a situation occurred where an increase in the boiler input was required, and after another 2 to 3 minutes, the boiler output became surplus and the situation became a situation where a boiler input range was required. That is, conventionally, the boiler was unstable, but the present invention can eliminate the cause of this instability.

3) The parameters of the main steam pressure correction circuit proportional calculator and integrator can be set to the same value during normal operation and under emergency operation such as when the system is alone.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the method of the present invention, and FIG. 2 is a system diagram showing an example of a conventional boiler output adjustment method. (la), (lb), (lc), (Id)
・= Subtractor (2a), (2b), (2c)
, (2d), (2e) - adder (3a),
(3b), (3c), (3d), (3e
)-switching relay (4a), (4b), (4c)
, (4d) - Signal generator (5)... Integrator, (
6)... Proportional calculator (7a), (7b)... Change rate limiter, (8)... Function generation 2L (9)... Low selector, 0 ■... High selector (II)...proportional/integrator, 02)...l pulse generator 0...turbine bypass valve.

Claims (1)

[Claims] In boiler-turbine cooperative control, which has the function of adjusting boiler input based on deviations in main steam pressure, when the main steam pressure rises beyond the control range, the turbine bypass valve is rapidly opened and then controlled at a constant value. The turbine bypass steam flow rate is added to the power generation amount that is the boiler input command, and then when the main steam pressure reaches the specified value, the turbine bypass amount is forcibly gradually reduced to reduce the main steam pressure to the actual power generation. A boiler output adjustment method in an emergency, characterized by adjusting the output to a value determined by the amount.