JPH0559903A - Automatic run back device - Google Patents

Abstract

PURPOSE:To enhance controllability of a governing valve and a control characteristic of a run back device by providing a control command output means for inputting a drive signal into a plant on the basis of a control command, and a turbine bypass regulating valve for controlling a steam line interposed between a boiler and the governing valve on the basis of the drive signal. CONSTITUTION:An input scanner 291 reads therein a process amount (a) a plant steam amount from a plant 20. A control operation judging means 293 judges on the basis of the process amount (a) whether a turbine bypass regulating valve 26 is to be controlled or not. The control operation judging means 293 informs a control command output means 294 a drive difference of the turbine bypass regulating valve 26, which is predicted by a process amount predictor 292. The control command output means 294 controls the turbine bypass regulating valve 26 on the basis the drive difference of the turbine bypass regulating valve 26. The turbine bypass regulating valve 26 is controlled in the above described manner, and consequently, a pressure difference between a boiler and a governing valve can be controlled to be constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load runback device for a power plant having a regulator valve.

[0002]

2. Description of the Related Art When a specific device in a power plant becomes abnormal and cannot be operated at full load, there is a possibility of causing an emergency stop of the plant. Therefore, in order to prevent this, a runback device has been conventionally used.

FIG. 9 is a schematic system diagram of a conventional power generation plant, and a conventional system diagram will be described based on this.

The steam generated in the boiler 1 is sent to the turbine 4 through the main shutoff valve 2 and the regulator valve 3, and the turbine 4
The generator 5 directly connected to is connected to the system, and the output of the generator 5 is sent to the system through the current transformer 8, the main transformer 10, and the circuit breaker 11.

The output current of the generator 5 is monitored by the current transformer 8 and the current detector 9 connected to it.

The generator stator cooling water is sent to the generator 5 by the stator cooling water pump 6, cools the stator, and then is sent to the heat exchanger 7 to remove the exhaust heat at the time of cooling the stator. It is discharged to the outside and sent again to the generator 5 by the stator cooling water pump 6. In this way, the generator stator is cooled.

Reference numeral 12 is a pressure switch (PS) for detecting the generator inlet pressure of the stator cooling water, which is turned on when it exceeds a specified value and turned off below. Further, 13 is a temperature switch (TS), which detects the generator outlet temperature of the stator cooling water, and turns on when the temperature exceeds a set value, and turns off below. The specified values and set values of these switches 12 and 13 are set to values necessary for protecting the generator, respectively, and the pressure switch 12 sets these values to P (for example, 0.9 Kg / c).
m ² ) and the temperature switch 13 is T (for example, 95 ° C.).

The current detector 9 is regulated to a current value I1 (for example, a rating of 30%) corresponding to the self-cooling capacity of the generator 5, and outputs an ON signal when I1 or more and an OFF signal when I1 or less.

FIG. 10 is a block diagram showing a conventional example.

That is, the pressure switch 12 is below P or the temperature switch 13 is above T, and the generator load current 14
Is a condition of I1 or more, the runback command signal A is adjusted 3
Control valve 15 to run back the regulating valve 3 at a predetermined constant load drop rate, the pressure switch 12 is P or more or the temperature switch 13 is T or more, and the generator load current 14 is I1 or less. Then, the runback command signal A is restored, and the runback of the regulator valve 3 is stopped.

[0011]

The problem with the above-described control is that in the turbine generator, because the stator is cooled by water, some accident occurs during operation near the rated load. If the cooling water is cut off in step 3, if the operation is continued as it is, the stator coil of the generator will be burned out.

In order to prevent such a situation, when the generator stator cooling water is abnormal (the temperature of the cooling water at the outlet of the generator is high or the pressure of the cooling water at the inlet of the generator is low), the self-cooling capacity of the generator is equivalent within 3 minutes. Control the turbine to reduce the load to.

A so-called load runback is performed,
If the load runback does not reach the target load within 3 minutes, the unit is tripped.

On the other hand, when the runback command signal A is generated, time counting is started by the timer 16 set to the runback allowable time (for example, 3 minutes), and the signal does not return within the set time t1. If the timer 1
The output signal B of 6 causes the unit to trip.

The above control has the following drawbacks. (1) Generally, in a steam turbine, the output time constant between the steam input and the generator output is about 6 to 10 seconds. (2) The main steam flow rate characteristic of the regulator valve is not necessarily a linear characteristic. (3) The load drop rate becomes small with respect to the throttle speed of the regulator valve 3 at the time of runback because the load following of the boiler is delayed.

FIG. 11 shows the regulating valve throttle speed V1 and the load current drop rate V2 when the runback occurs in the turbine generator operating at the rated load IO. Time t0
At this time, a runback occurs, and the regulator valve 3 starts to narrow down at the speed of V1 immediately, but the load current starts to drop after t2 due to the turbine output time constant. After t "1 has elapsed, the control valve opening is narrowed down to an opening equivalent to the generator's self-cooling capacity I1, but at this time the load current has not yet dropped to I1, so the runback further progresses and t'1 ( t "1 <t'1 <
After t1), I1 is reached and runback stops. At this time, the regulator valve is narrowed down to an opening corresponding to I2 (I2 <I1), so that the load current continues even after the runback is stopped and drops to the value of I2. The value of I2 is generally small, and when running back from the rated load, the value often falls below the limit of stable control by the regulator valve 3, and sometimes the regulator valve is fully closed.

Therefore, conventionally, the runback due to the abnormality in the cooling water of the stator has not been successful, and the trip has occurred.

Therefore, according to the present invention, at the time of runback, the regulator valve is narrowed down to a set opening corresponding to the generator self-cooling capacity, and at the same time, steam to the turbine is bypassed by the turbine bypass adjusting valve, and the bypass steam amount is adjusted. By controlling, the control capability of the regulator valve is enhanced and the control characteristic of the runback is improved.

[0019]

The structure of the present invention will be described with reference to the basic conceptual diagram shown in FIG.

The input scanning means 291 reads the process amount a of the plant steam amount from the plant 20 and converts it into a digital amount, and the converted process amount a is notified to the control operation judging means 293.

The control operation judging means 293 judges whether to control the turbine bypass adjusting valve 26 with the process amount a input from the input scanning means 291. When it is determined to control the turbine bypass adjusting valve 26, the process amount predicting means 292 of the plant 20 is notified, and the drive difference of the turbine bypass adjusting valve 26 is notified to the process amount predicting means 292.
Enter from.

The process amount predicting means 292 predicts in advance the drive difference of the turbine bypass adjusting valve 26 after a certain time from the process amount a and notifies the control operation judging means 293. The control operation determination means 293 is the process amount prediction means 2
92 notifies the control command output means 294 of the drive difference of the turbine bypass adjusting valve 26.

The control command output means 294 controls the turbine bypass adjusting valve 26 according to the drive difference of the turbine bypass adjusting valve 26.

As described above, the turbine bypass adjusting valve 2
By performing the control of No. 6, the boiler 21 and the regulator valve 23
The pressure difference between them can be controlled to be constant.

[0025]

Next, the operation of the present invention will be described with reference to FIGS.

As shown in FIG. 2, the input scanning means 291.
Is the process amount a of the plant steam amount from the plant 20.
Is read and converted into a digital amount, and the converted process amount a is notified to the control operation determination means 293.

The control operation judging means 293 notifies the process amount predicting means 292 of the differential pressure command b across the regulator valve 23,
The turbine bypass adjusting valve opening command c is input from the process amount predicting means 292.

The processing of the control operation judging means 293 will be described with reference to the flowchart of FIG.

(1) Control valve (CV) from the plant 20
23, the differential pressure across the regulator valve 23 is calculated, the differential pressure across the regulator valve 23 is calculated, and the process amount predicting means 2 is used as the differential pressure command b before and after the regulator valve 2.
Notify to 92 (S1). (2) It is determined whether the differential pressure across the regulator valve 23 is within α (allowable differential pressure), and whether the turbine bypass adjustment valve 26 is controlled (S2). Front differential pressure of the regulator valve 23-Post differential pressure of the regulator valve ≧ α There is limitation. Front differential pressure of the regulator valve 23-Post differential pressure of the regulator valve 23 ≦ α No limitation. (3) Process amount prediction when it is determined to control Means 2
The opening of the turbine bypass (TB) adjusting valve 26 is input from 92 (S3). (4) It is judged from the process amount a of the plant 20 whether or not the engine is in a runback. If the engine is not in a runback, the turbine bypass adjusting valve 26 is not controlled (S4). (5) During the runback, the turbine bypass adjusting valve 26 is output as a control command according to the opening degree of the turbine bypass adjusting valve 26 (S5). (6) It is determined whether control is impossible (S6). Control count ≧ β Unrestricted control count ≦ β Restrictable Here, β represents an allowable count. (7) When control is possible, control is performed again by the differential pressure across the regulator valve 23. (8) If control is impossible, the plant 20 is tripped to protect it (S7).

Next, the processing of the process amount predicting means 292 will be described with reference to FIG.

The process amount predicting means 292 obtains an expected curve 91 of the differential pressure across the regulator valve 23 from the following data. <Data for calculating the expected curve> Differential pressure X0 before and after the regulating valve 23 at the present time t0 Before and after differential pressure X-1 of the regulating valve 23 at the time point t-1 before 1 time Before and after the regulating valve 23 at the time point t-2 2 times before Differential pressure X-2 Three times before and after differential pressure X3 of the regulating valve 23 at time t-3 Before and after differential pressure X-n of the regulating valve 23 at time t-n before n times X-n where X0 is the current regulating valve Indicates the differential pressure across 23, X-1
~ X-n represents the differential pressure across the regulator valve 23 in the past, t-1 ~
t-n represents the time of each event, and X1 represents the predicted differential pressure across the regulator valve 23. <Prediction curve> X = f (t) ... Expected curve formula for differential pressure across the regulator valve 23. The differential pressure X1 across the regulator valve 23 after a certain time t1 is calculated by the forecast curve formula.

The relationship between the differential pressure across the regulator valve 23 and the turbine bypass adjusting valve 26 can be expressed by the relationship shown in FIG. 4. Therefore, the turbine bypass adjustment is performed based on the differential pressure across the regulator valve 23 at a constant time t1. The opening degree of the valve 26 can be predicted. Here, 92 represents a load runback prediction curve. Then, the turbine bypass adjusting valve opening degree Δk% is notified to the control operation determining means 293.

As described above, the control operation judging means 2 of FIG.
At 93, the opening degree of the turbine bypass adjusting valve 26 is predicted, the control operation determining means 293 makes an operation determination, and the control instruction d is notified to the control instruction output means 294.

The control command output means 294 can control the turbine bypass adjusting valve 26 by the drive signal e.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a steam system diagram showing an embodiment of the present invention.
The steam generated in the boiler 21 is sent to the turbine 24 through the main stop valve 22 and the regulator valve 23. A turbine bypass adjusting valve 26 controls the amount of steam flowing from a steam line between the outlet of the boiler 21 and the regulator valve 23 to a condenser 25.

As the control method, the deviation between the set value preset by the pressure setter 28 and the pressure difference before and after the adjusting valve is 0.
Thus, the pressure regulator 27 controls the turbine bypass regulating valve 26.

When the amount of steam in the steam line is runback, when the regulator valve 23 is rapidly throttled in a short time, the boiler 2
Since the steam generation amount of No. 1 does not decrease following this, the pressure in the boiler side pipe of the regulator valve 23 increases by throttling the regulator valve 23, and if the differential pressure between the inlet and outlet of the regulator valve 23 increases, the load The process amount a input to the runback device 29 increases, the opening degree of the turbine bypass adjusting valve 26 is predicted from the process amount a, and the turbine bypass adjusting valve 26
Is controlled so that the amount of steam flowing into the turbine 24 whose pressure is constant is proportional to the opening degree of the regulator valve 23.

The drive device for the turbine bypass adjusting valve 26 has a sufficient response speed with respect to the pressure change speed between the boiler 21 and the regulator valve 23.

As described above, the turbine bypass adjusting valve 2
Even if an extremely large amount of steam is increased by automatically controlling 6, the amount of steam of the adjusting valve 23 is adjusted to adjust the adjusting valve 23.
The amount of steam proportional to the opening degree of the regulator valve 23 can be sent to the turbine 24 while suppressing the pressure increase due to the narrowing of.

Next, the load runback device 2 according to the present invention.
9 will be described with reference to FIG.

The input scanning means 292 reads the pressure before and after the regulating valve and the pressure after the regulating valve which are the process amount a from the plant 20 and notifies the process predicting means 292 as the differential pressure before and after the regulating valve.

The process predicting means 292 reads the pressure before the adjustment valve and the pressure after the adjustment valve in a cycle of 1 second.

The plant process amount and time data will be described below with reference to FIG.

At the time of 55 seconds, the pressure before adjustment valve PA1, the pressure after adjustment valve PB1, etc. are read. Based on the process amount a, it is determined whether to control the turbine bypass adjustment valve 26.

From the time 55 seconds to the time 58 seconds, there is no differential pressure between the pressure before and after the control valve, and therefore it is judged that the turbine bypass adjusting valve 26 is not controlled.

When the time is 59 seconds and 1 minute, the differential pressure is ΔP5,
Since it becomes ΔP6, it is judged that control is performed. The process amount predicting unit 292 predicts the differential pressure after 1 second, based on the pressures before and after the adjustment valve for the past four times.

For the prediction, the data of the past four times and the present value are obtained, and the least square method is used.

The turbine bypass adjusting valve opening ΔK7 is calculated from the predicted differential pressure ΔP7.

Whether or not the turbine bypass adjusting valve opening degree is controlled is determined by determining whether or not the state of the plant 20 is in the runback state. If it is in the runback state, the turbine bypass adjusting valve opening degree ΔK7 is controlled. Notify the judgment means 293.

As described above, the opening of the turbine bypass adjusting valve 26 is predicted by the process amount predicting means 292 of FIG.
The operation is judged by the control operation judging means 293, and the control command d
To the control command output means 294. The control command output means 294 can control the turbine bypass adjustment valve 26 by the drive signal e.

The control characteristic and control block according to the present invention will now be described with reference to FIGS. 7 and 8.

FIG. 7 shows the control characteristics.

The output characteristic V2 of the generator is delayed by the inertia of the turbine 24 with respect to the load drop straight line V1 of the regulator valve 23, but drops almost in parallel.

The alternate long and short dash line shows the output characteristic of the generator when the conventional control method is used. The time required to reach the permissible current I1 at which the generator self-cooling operation is possible is greatly shortened, and the regulator 23 It can be seen that the control ability has increased.

FIG. 8 shows a control block.

When the pressure switch 31 or the temperature switch 32 operates due to an abnormality in the stator cooling system and the current value flowing through the stator exceeds a preset set value, a runback command A is given to the controller 34. A throttle operation is performed on the regulator valve 23 so that a predetermined load drop rate is obtained.

The turbine bypass adjusting valve 26 is normally fully closed, and the load runback device 29 is also inactive.

In response to the runback command A, the turbine bypass adjusting valve 26 is controlled by the load runback device 29 to start the pressure adjustment between the boiler 21 and the regulator valve 23.

In this way, the runback operation is started,
Allowable current I1 for generator stator current to allow generator self-cooling operation
Then, the load current detector 33 detects this and gives a runback stop command A to the control device 34 and the load runback device 29, and the runback ends.

If the generator stator current does not drop to the allowable current value I1 even after a certain period of time, a unit trip command B is issued and the boiler 21 and turbine 2
4. Stop all generators.

In the above embodiment, the case where the stator cooling system is abnormal has been described. However, as other application examples, there are abnormalities in the pushing fan and the induction fan, abnormalities in the boiler feed water pump, abnormalities in the circulating water pump, and phase separation. Since the load runback is similarly performed in the abnormality of the bus bar cooling system, it is effective to apply the present invention.

[0062]

As described above, according to the present invention, the turbine inlet pressure is controlled by controlling the turbine inlet pressure so as to match the amount of steam generated at the boiler outlet,
Also, since the increase in rotation speed can be suppressed by narrowing down the regulator valve and the steam amount proportional to the valve opening of the regulator valve can be sent to the turbine, the steam amount can be quickly and accurately adjusted by the regulator valve regardless of the following speed of the boiler. Can be controlled.

Therefore, if the load drop rate of the regulator valve is appropriately set, the time difference between the time until the generator stator current falls to the allowable value and the time when the opening of the regulator valve corresponds to the allowable value is It will be very short, and it will not trip too much too much as in the past.

[Brief description of drawings]

FIG. 1 is a steam system diagram of the present invention.

FIG. 2 is a configuration diagram of the inside of a computer of the present invention.

FIG. 3 is a differential pressure predictive curve before and after the control valve of the present invention.

FIG. 4 is a characteristic diagram of before and after a control valve and a turbine bypass adjustment valve opening degree characteristic of the present invention.

FIG. 5 is a flowchart of the control operation means of the present invention.

FIG. 6 is a diagram showing a relationship between a plant process amount and time data according to the present invention.

FIG. 7 is a control characteristic diagram of the present invention.

FIG. 8 is a control block diagram of the present invention.

FIG. 9 is a system diagram showing an outline of a power generation system and a stator cooling water system.

FIG. 10 is a conventional block diagram.

FIG. 11 is a diagram showing a relationship between a control valve opening degree and a generator stator current time.

[Explanation of symbols]

 20 ……… Plant 21 ……… Boiler 23 ……… Adjusting valve 24 ……… Turbine 26 ……… Turbine bypass adjusting valve 29 ……… Load runback device 31 ……… Pressure switch 32 ……… Temperature switch 23 Control valve 24 Turbine 26 Turbine bypass control valve 29 Load runback device 31 Pressure switch 32 Temperature switch 33 Generator output load current 34 ... control device 291 ... input scanning means 292 ... process amount prediction means 293 ... control operation determination means 294 ... control command output means a ... process amount d ... control command e ... Drive signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H02P 9/04 H 6728-5H

Claims (1)

[Claims] 1. In a power plant having a regulator valve, an input scanning means for reading a process amount from a detector and converting it into a digital amount inside a computer, and a process amount after a predetermined time from the process amount input by the input scanning means. Process amount predicting unit that predicts the process state, a control operation determining unit that determines the state of the plant from the predicted process amount, and determines whether or not a control operation for the plant is necessary, and a drive signal is output to the plant according to a control command. A load runback characterized by comprising a control command output means and a turbine bypass adjusting valve for controlling a steam line between the boiler and the regulator valve by a drive signal, and controlling the regulator differential pressure to be constant. apparatus.