JP2013164195A - Method for controlling steam pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provided a method for controlling steam pressure capable of enhancing the control performance of the steam pressure in boiler turbine power generation facilities suppressing the generation of vibration even though the vibration is generated in the case of setting a large gain.SOLUTION: In a method for controlling a steam pressure including differential control, it is determined that the generation of the vibration of the steam pressure is generated, a fuel quantity correcting amount is corrected by a correcting gain according to a section of a steam pressure variation (ΔP) to a correcting amount by the differential control of the steam pressure variation (ΔP), and the correcting gain is made zero in a section including a value where the steam pressure variation (ΔP) becomes zero, in the case that a time (Tp) from a time 31 when the steam pressure variation (ΔP) deviates from a pressure range set in advance at the first time to a time 34 when the same enters the pressure range at the second time is not shorter than a time (Tv) set in advance, in the case (34) that the steam pressure variation (ΔP) between a steam pressure measured value and a vapor pressure set value deviates from the pressure range 37 set in advance (31), phenomena entering the pressure range 37 occur more than two times.

Description

  TECHNICAL FIELD The present invention relates to a steam pressure control method for a boiler, a turbine, and a generator facility that generates heat by supplying steam generated by supplying fuel to a boiler and absorbing the heat generated by a heat exchanger to a turbine. .

  The boiler equipment used in power generation is equipment that uses high-temperature and high-pressure steam. In power generation using the boiler equipment, fuel is supplied to the boiler for combustion, and the heat generated by absorbing the heat with a heat exchanger. Is used for the boiler, turbine, and generator equipment (hereinafter referred to as “BTG equipment”).

  In the BTG facility, it is necessary to improve the controllability of the boiler steam system so that the boiler tube protection, the turbine blade protection, and the generator do not exceed the power generation output upper limit.

  FIG. 7 is a diagram showing an outline of the boiler steam system and its control. The boiler steam system control mechanism includes a BTG facility 1, a power generation amount command 10 and a fuel amount control unit 12 that controls the amount of fuel supplied to the boiler 2 in accordance with the fuel amount correction amount 22 from the steam pressure control unit 18, and a power generation A governor control unit 14 that controls the amount of steam flowing into the governor valve 3 according to the amount command 10 and a boiler steam pressure that corrects the fuel amount by feedback based on the deviation between the set value of the steam pressure of the boiler 2 and the measured value. And a control unit 18.

  In the boiler steam system, the governor valve is operated according to the change in the power generation command 10, and the steam pressure and flow rate change is detected, and the fuel follow-up control method and the required load command are controlled. Boiler / turbine cooperative control is installed that controls the opening of the governor valve, the amount of fuel, the amount of water supply, etc., which are input in parallel to the boiler and turbine.

  For example, if the amount of fuel supplied to the boiler 2 is excessive, the amount of steam generated increases and the steam pressure of the boiler increases. At this time, if the turbine supply pressure increases, the power generation output becomes excessive. Therefore, the governor control unit 14 closes the governor valve 3 to prevent an increase in the amount of steam supplied to the turbine 4. Thereby, the electric power output from the generator 5 can be kept constant. Moreover, if the amount of fuel supplied to the boiler 2 is insufficient, the amount of steam generated decreases and the steam pressure of the boiler decreases. At this time, if the turbine supply pressure decreases, the power generation output is insufficient. At this time, the governor control unit 14 opens the governor valve 3 to prevent a reduction in the amount of steam supplied to the turbine 4. Thereby, the electric power output from the generator 5 can be kept constant.

  Furthermore, when the amount of steam supplied from the boiler 2 to the turbine 4 changes due to the opening and closing of the governor valve 3, the steam pressure in the boiler 2 (boiler steam pressure) changes. That is, when the amount of fuel supplied to the boiler 2 is excessive, only a part of the steam generated in the boiler 2 is supplied to the turbine 4, so that the boiler steam pressure rises.

  Now, when a certain amount of power is generated, the power generation amount command 10 is a fixed value, but there are the following problems.

  For example, when the amount of fuel supplied to the boiler 2 is insufficient, the amount of steam generated in the boiler 2 is supplied to the turbine 4 so that the boiler steam pressure decreases. For example, the steam pressure deviation 21 (ΔP) is a deviation of the actual steam pressure value 19 from the steam pressure set value 9 so that the boiler steam pressure changing in this way becomes a predetermined set value. Proportional control for correcting using a value obtained by multiplying the proportional gain by the integral control, integral control for correcting the fuel amount using a value obtained by multiplying the integral gain by the value obtained by integrating the steam pressure deviation 21 (ΔP), or the steam pressure deviation Differential control is used in which the fuel amount is corrected using a value obtained by multiplying a value obtained by differentiating 21 (ΔP) by a differential gain. Such a control method is disclosed in Patent Documents 1 and 2.

  However, the steam pressure control system of boilers, turbines, and generator equipment that generates electricity by supplying steam generated by absorbing fuel generated by supplying fuel to the boiler with a heat exchanger is not Therefore, there is a time delay of several minutes until the water vapor is generated, and there is a problem that the fluctuation of the fuel amount by the correction itself induces the vibration of the control system.

  When differential control is used, the fuel amount is corrected even for a minute change in the steam pressure deviation (ΔP), and as a result, the vibration of the control system is induced. In addition, when differential control is used, the waveform of the correction amount by differential control is a waveform with a 90 ° phase advance with respect to the steam pressure deviation (ΔP), so when the steam pressure deviation starts to vibrate. When differential control is performed, vibration is promoted.

  On the other hand, when the gain used for the control is reduced, there is a problem that the control response is delayed and the controllability is deteriorated.

JP 2006-2000875 A JP 2004-190913 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to improve the controllability of the steam pressure and to generate vibration when a large gain is set. Another object of the present invention is to provide a steam pressure control method capable of suppressing the generation thereof.

The inventor has earnestly researched and developed steam pressure control for boilers, turbines, and generator equipment that generates heat by supplying steam generated by supplying fuel to the boiler and absorbing the heat generated by the heat exchanger. When the steam pressure deviation (ΔP) deviates from the preset pressure range and the phenomenon of entering the pressure range occurs more than once, the steam pressure deviation (ΔP) is a preset pressure. When the time (T _P ) from the time when the range departs from the first time to the time when the pressure enters the pressure range for the second time is equal to or less than the preset time (T _V ), the vapor pressure deviation (ΔP) is It can be determined that the vibration has started, and if the steam pressure deviation (ΔP) starts to vibrate, the correction gain for differential control is set to zero in the vicinity where the steam pressure deviation (ΔP) becomes zero. Can suppress vibration It was found that.

From the above, the gist of the present invention is as follows.
(1) The actual value of boiler steam pressure in boilers, turbines, and generator equipment that generates electricity by supplying steam generated by absorbing fuel generated by supplying fuel to the boiler with a heat exchanger. When correcting the amount of fuel to be supplied to the boiler for control, the difference between the boiler steam pressure setting value and the actual boiler steam pressure value is the steam pressure deviation (ΔP), and the differential gain is added to the differential value of the steam pressure deviation (ΔP). A method of calculating and correcting the fuel amount correction amount using a value multiplied by Kd (hereinafter referred to as “differential control”),
The steam pressure deviation (ΔP) deviates from a preset pressure range and the phenomenon of entering the pressure range has occurred twice or more, and the steam pressure deviation (ΔP) is preset. The time of entering the pressure range for the second time from the time when the pressure range deviated for the first time (hereinafter referred to as “first time of departure”) (hereinafter referred to as the “second time of entry”). The second entry time (hereinafter referred to as “start time”) when the time until (hereinafter referred to as “pseudo-vibration period”) (T _P ) is equal to or less than a preset time (T _V ). And correcting the fuel amount correction amount with a correction gain according to the classification of the steam pressure deviation (ΔP) with respect to the correction amount by the differential control,
A steam pressure control method, wherein the correction gain is set to zero in a section including a value at which the steam pressure deviation (ΔP) is zero.

  According to the apparatus and method of the present invention, it is possible to improve the controllability of the steam pressure, and to exert a remarkable effect that vibration generated even at a large gain setting can be suppressed.

Steam pressure deviation control system block diagram Block diagram of control unit Block diagram of differential control unit Block diagram of differential control unit Judgment of vibration start It is a graph of the present invention, and (a) when only differential control is performed It is a graph of the present invention, and (b) When differential control is performed together with proportional / integral control It is a graph of a comparative example, (a) When only differential control is performed It is a graph of a comparative example, (b) When differential control is implemented together with proportional / integral control Conceptual diagram of boiler, turbine, generator equipment and control equipment

  An embodiment for carrying out the present invention is a boiler for a turbine, a turbine, and a generator facility that generates electricity by supplying steam generated by absorbing heat generated by supplying fuel to a boiler and burning it with a heat exchanger. This is a method of correcting the amount of fuel supplied to the boiler to control the actual steam pressure value to a constant value.

  In boiler steam pressure control, proportional control, integral control, differential control, or a combination of these is performed using the steam pressure deviation (ΔP), which is a deviation of the actual steam pressure value from the steam pressure set value, as an index.

  Consider a case where the steam pressure deviation (ΔP) of the boiler starts to oscillate for some reason. In the middle of vibration, in the vicinity where the steam pressure deviation (ΔP) becomes zero, the absolute value of the differential value of the steam pressure deviation (ΔP) is usually the maximum. Therefore, in the vicinity where the steam pressure deviation (ΔP) is zero, the differential control amount becomes a large value (absolute value) and the fuel amount is corrected although the correction of the fuel amount is not actually required. As a result, it was found that the steam pressure deviation (ΔP) was an obstacle to convergence of vibration. Therefore, if a differential gain that is a constant value with respect to the steam pressure deviation (ΔP) is used, vibration is promoted. In other words, if the differential control amount is reduced when the steam pressure deviation (ΔP) is equal to or less than a preset value, it means that the promotion of vibration can be prevented.

  Therefore, the present invention provides the steam pressure deviation (ΔP) in the differential control in which the fuel amount correction amount is calculated and corrected using a value obtained by multiplying the differential value of the steam pressure deviation (ΔP) by the differential gain Kd. It has been found that the vibration of the boiler steam pressure can be effectively suppressed by multiplying the correction gain so that the correction amount becomes zero in the vicinity of the value where becomes zero.

The start time of multiplying the differential control gain by the correction gain is after the steam pressure deviation starts to oscillate. The fact that the steam pressure deviation (ΔP) starts oscillating indicates that the steam pressure deviation 21 (ΔP) deviates from the pressure range 37 set in advance at 31 (first deviation), as shown in FIG. After that, the pressure range 37 is entered at 32 (first entry), 33 is deviated from the pressure range 37 (second departure), and 34 is entered into the pressure range 37 (second entry). In this case, the determination is made when the time (T _P ) from the first departure time 31 to the second entry time 34 is equal to or less than a preset time (T _V ). The start time of the vibration of the steam pressure deviation is the second entry time 34.

(Control system configuration)
FIG. 1 shows the basic configuration of the control system of the present invention. The steam pressure actual measurement value (P) 19 of the steam generated by the boiler 2 is drawn from the drawing point 28 and subtracted from the steam pressure set value (PN) 9 at the addition point 29 to calculate the steam pressure deviation (ΔP). Has been.
That is, ΔP = PN−P.
The steam pressure control unit 18 calculates the fuel amount correction amount (ΔF) with the steam pressure deviation (ΔP) 21 as an input. The fuel amount control unit 12 calculates the fuel amount (F) 23 with the fuel amount correction amount (ΔF) as an input. The calculated fuel amount 23 is given to the boiler 2, and in response to this, new steam is generated, and the temperature of the steam is controlled by the temperature control unit 16. The steam whose temperature has been controlled is given to the turbine 4 and the generator 5 to generate power.

(Steam pressure control unit)
FIG. 2 shows the configuration of the steam pressure control. The steam pressure control unit includes a vibration start determination unit, a differential control unit, an integral control unit, and a proportional control unit. The vibration start determination unit constantly monitors whether or not the steam pressure deviation (ΔP) is oscillating, and when it is determined that the vibration has started, the differential control unit and, if necessary, the integral control unit, proportional A notification to that effect is sent to the control unit. The integral control unit calculates an integral control correction amount 58 using the steam pressure deviation (ΔP) as an input after being drawn from the withdrawal point 28. For the proportional control, the proportional pressure correction amount 68 is calculated by taking the steam pressure deviation (ΔP) from the extraction point 28 as an input. The integral control correction amount 58 and the proportional control correction amount 68 are added at the addition point 29 to become the fuel amount correction amount 22.

(Vibration start determination unit)
Reference numeral 80 in FIG. 2 denotes a vibration start determination unit. FIG. 4 shows an outline of the determination that the steam pressure deviation (ΔP) has started to vibrate.

  In FIG. 4, the vertical axis represents the steam pressure deviation (ΔP), the horizontal axis represents time (t), 35 is a line indicating the upper limit value of the steam pressure deviation (ΔP), and 36 is the steam pressure deviation. This is a line indicating the lower limit of (ΔP), and 37 is a preset pressure range of the steam pressure deviation (ΔP).

  30 is a graph representing the behavior of the steam pressure deviation (ΔP) from time to time, and intersects with the line 35 representing the upper limit value of the steam pressure deviation (ΔP) at 31 and 32, and the steam pressure deviation (ΔP) ) Crosses the line 36 representing the lower limit at 33 and 34.

  In FIG. 4, the time corresponding to 31 is the time when the steam pressure deviation (ΔP) deviates from the preset pressure range 37 for the first time, and the time corresponding to 32 is the time when the steam pressure deviation (ΔP) is This is the time when the pressure range 37 is first entered, and the time corresponding to 33 is the time when the steam pressure deviation (ΔP) deviates from the preset pressure range 37 for the second time, corresponding to 34. The time when the steam pressure deviation (ΔP) enters the pressure range 37 set in advance for the second time.

Therefore, the time corresponding to the time corresponding to 31 and the time corresponding to 34 enters the pressure range for the second time from the time when the steam pressure deviation (ΔP) deviates from the preset pressure range for the first time. Time (T _P ).

As a result of diligent research and development, the inventors have found that when the time (T _P ) from the time of departure from the first time to the time of entering the pressure range at the second time is less than or equal to the preset time (T _V ) It is possible to effectively suppress the vibration by determining that the steam pressure deviation (ΔP) has started to vibrate, and immediately taking measures for suppressing the vibration after the time corresponding to 34, which is the time when the judgment is made. I found.

The preset time (T _V ) is a vibration cycle that usually occurs, and is 5 to 20 minutes, preferably 8 to 18 minutes, and more preferably about 10 to 16 minutes.

(Differential control part)
Differential control unit, as shown in FIG. 3 (a), a differentiator 71, a differential gain Kd77, and a corrected gain Kdg _1. The steam pressure deviation (ΔP) 21 is differentiated by a differentiator 71 and multiplied by a differential gain Kd. When the start of vibration is recognized, the correction gain Kdg ₁ is further multiplied to calculate a differential control correction amount 78.

As the correction gain Kdg ₁ , an independent correction gain can be set for each range section of the steam pressure deviation (ΔP) as shown in FIG. In particular, the correction gain is set to zero for a section whose range is a value at which the steam pressure deviation (ΔP) is zero. This is based on an empirical rule that, when the steam pressure deviation (ΔP) is near zero, if the differential control is positively performed, vibration of the steam pressure deviation (ΔP) is promoted.

  Examples of the present invention and comparative examples will be described below. In the boiler / turbine / generator facility as shown in FIG. 7, the basic configuration of the control system shown in FIG. 1 is used to correct the amount of fuel supplied to the boiler so as to control the actual steam pressure value of the boiler to a constant value. The method was carried out.

(Example of the present invention)
FIG. 5 is a graph showing the steam pressure deviation (ΔP) by controlling the steam pressure deviation (ΔP) using the method of the present invention, the fuel correction amount by differential control, and the total fuel correction amount.

<For differential control only>
FIG. 5A shows the case where only the differential control is performed.

The steam pressure deviation (ΔP) deviates from a preset range (first deviation), and the vibration start is recognized by the second entry. Before recognizing the start of vibration, only Kd is used as the differential control gain. When the vibration start is recognized, the correction gain Kdg ₁ is further multiplied by Kd as a differential control gain. The correction gain Kdg ₁ of the differential control Kd is divided for each steam pressure deviation (ΔP), and is set to be zero in a section including a value where the steam pressure deviation (ΔP) is zero. ing. Therefore, the differential control calculates the fuel correction amount so as to suppress the vibration of the steam pressure deviation (ΔP) at the vibration start timing, and when the steam pressure deviation (ΔP) falls within a preset range, the fuel is corrected. The correction amount is set to zero to suppress the promotion of vibration of the steam pressure deviation (ΔP).

  As a result, it can be seen that the steam pressure deviation (ΔP) converges with time.

<When differential control is performed together with proportional / integral control>
FIG. 5B shows a case where differential control is performed together with proportional / integral control.

Although differential control is performed together with proportional / integral control, the steam pressure deviation (ΔP) deviates from a preset range (first deviation), and the start of vibration is recognized by the second entry. Before recognizing the start of vibration, only Kd is used as the differential control gain. When the vibration start is recognized, the correction gain Kdg ₁ is further multiplied by Kd as a differential control gain. The correction gain Kdg ₁ of the differential control Kd is divided for each steam pressure deviation (ΔP), and is set to be zero in a section including a value where the steam pressure deviation (ΔP) is zero. ing. Therefore, the differential control calculates the fuel correction amount so as to suppress the vibration of the steam pressure deviation (ΔP) at the vibration start timing, and when the steam pressure deviation (ΔP) falls within a preset range, the fuel is corrected. The correction amount is set to zero to suppress the promotion of vibration of the steam pressure deviation (ΔP).

  As a result, it can be seen that the steam pressure deviation (ΔP) converges with time.

(Comparative example)
A comparative example not using the method of the present invention is shown in FIG.

<For differential control only>
FIG. 6A shows the case where only the differential control is performed.

  In the comparative example, the vibration start recognition of the steam pressure deviation (ΔP) is not performed. Therefore, only Kd is used as the differential control gain as before in the conventional example before and after the time when the vibration start should be recognized. . There is no correction gain as in the present invention.

  Therefore, the vibration of the steam pressure deviation (ΔP) is promoted by the differential control, and the vibration is enlarged.

<When differential control is performed together with proportional / integral control>
FIG. 6B shows a case where differential control is performed together with proportional / integral control.

  In the comparative example, the vibration start recognition of the steam pressure deviation (ΔP) is not performed. Therefore, only Kd is used as the differential control gain as before in the conventional example before and after the time when the vibration start should be recognized. . There is no correction gain as in the present invention.

  Therefore, the vibration of the steam pressure deviation (ΔP) is promoted by the differential control, and the vibration is enlarged.

1: Boiler / turbine / generator equipment 2: Boiler 3: Governor valve 4: Turbine 5: Generator 6: Condenser 9: Steam pressure set value 10: Power generation amount command 12: Fuel amount control unit 14: Governor control unit 16: Steam temperature control unit 18: Steam pressure control unit 19: Actual steam pressure value 21: Steam pressure deviation 22: Fuel amount correction amount 23: Fuel amount 28: Extraction point 29: Addition point 50: Integration control unit 60: Proportional control Unit 70: derivative control unit 71: differentiator 72: derivative control correction gain 77: derivative control gain 78: derivative control correction amount

Claims (1)

To control the actual steam pressure of boilers, turbines, and generator equipment that generates electricity by supplying steam generated by supplying fuel to the boiler and absorbing the heat generated by the heat exchanger. In correcting the amount of fuel supplied to the boiler, the difference between the boiler steam pressure setting value and the actual boiler steam pressure value is the steam pressure deviation (ΔP), and the differential value of the steam pressure deviation (ΔP) is multiplied by the differential gain Kd. A method for calculating and correcting the fuel amount correction amount using a value (hereinafter referred to as “differential control”),
The steam pressure deviation (ΔP) deviates from a preset pressure range and the phenomenon of entering the pressure range has occurred twice or more, and the steam pressure deviation (ΔP) is preset. The time of entering the pressure range for the second time from the time when the pressure range deviated for the first time (hereinafter referred to as “first time of departure”) (hereinafter referred to as the “second time of entry”). The second entry time (hereinafter referred to as “start time”) when the time until (hereinafter referred to as “pseudo-vibration period”) (T _P ) is equal to or less than a preset time (T _V ). And correcting the fuel amount correction amount with a correction gain according to the classification of the steam pressure deviation (ΔP) with respect to the correction amount by the differential control,
A steam pressure control method, wherein the correction gain is set to zero in a section including a value at which the steam pressure deviation (ΔP) is zero.

Images