JP2000266304A - Desuperheater control device - Google Patents

Abstract

(57) [Problem] To provide a controller that flexibly responds to changes in operating conditions and environmental conditions without saturation and divergence, and always controls the steam temperature at the outlet side of a superheater in a satisfactory manner. SOLUTION: Water or low-temperature steam mixed into steam from a superheater 2 provided at an inlet side of a superheater 1 upstream of a turbine in a steam supply system for supplying steam generated by a boiler of a thermal power plant to a turbine. In the desuperheater control device for lowering the steam temperature by controlling the flow rate through the flow control valve 3, a higher-order controller having an integrating element for integrating a deviation between the steam temperature at the outlet of the superheater and the temperature set value. 30 and a lower controller 10 that inputs the output of the upper controller as a set value and controls the flow control valve 3 based on a deviation from the inlet-side steam temperature of the superheater 1, and When the output of the lower-level controller 10 is equal to or less than a certain value, a signal limiter 32 is provided to limit the input signal of the integration element of the higher-level controller 40 so that the input signal does not become 0 or negative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desuperheater control device used in a steam power plant or a combined cycle plant.

[0002]

2. Description of the Related Art Among thermal power plants, a combined cycle plant exchanges heat with the exhaust gas of a gas turbine to generate steam, and a general steam power plant utilizes the calorific value of combustion gas in a boiler. It produces steam. Then, the steam is superheated by a superheater and sent to the steam turbine, thereby rotating the steam turbine and driving the generator.

At this time, in the steam supply system to the steam turbine, the main steam temperature at the turbine inlet sometimes reaches a maximum value, and operation beyond this temperature is not desirable from the viewpoint of equipment safety.

Therefore, conventionally, a desuperheater is installed at the inlet of the superheater, and when the main steam temperature exceeds the maximum temperature, water or low-temperature steam is blown into the main steam from the desuperheater to lower the steam temperature below the maximum value. Temperature reduction operation.

FIG. 6 shows a general configuration of such a temperature reducer and a configuration example of a temperature reducer control device. In FIG. 6, reference numeral 1 denotes a superheater into which steam generated by a boiler (not shown) is introduced through a steam supply system. The steam heated by the superheater 1 is passed through a steam supply system to a superheater (not shown) or a steam turbine at a next stage. It is supplied to.

Reference numeral 2 denotes a desuperheater provided in a steam supply system on the inlet side of the superheater 1. The desuperheater 2 has a nozzle for spraying water or low-temperature steam, and the nozzle has a cooling device. A medium supply system is connected, and the cooling medium supply system is provided with a flow control valve 3.

On the other hand, reference numeral 20 denotes a steam temperature 102 at the outlet side of the superheater 1 measured by the thermometer T1 and a temperature set value 100.
Is a higher-level controller to which the higher-level controller 20 compares the steam temperature 102 with the temperature set value 100.
1, a proportional element 22 to which the deviation between the steam temperature and the temperature set value is input from the comparing section 21, an integrating element 23 for integrating a signal obtained through the proportional element 22, and integration by the integrating element 23. And an adder 24 for adding the signal and the signal obtained through the proportional element 22.

Reference numeral 10 denotes a lower controller to which the steam temperature on the inlet side of the superheater 1 measured by the thermometer T2 and the output of the upper controller 20 are input. The lower controller 10 is a lower controller. Controlling the flow rate of water or low-temperature steam blown into the steam through the nozzle of the desuperheater 2 by adjusting the opening of the flow control valve V by comparing the output with the steam temperature on the inlet side of the superheater 1 as a set value. It is.

Here, the control of the desuperheater 2 is a cascade control, and the output of the upper controller 20 becomes the set value of the lower controller 10.

The control purpose of the desuperheater control device having such a configuration is to mix the cooling medium at an appropriate flow rate into the working steam so as to reduce the steam temperature 102 at the outlet side of the superheater 1 to the heater 1.
Is to control the steam temperature at the outlet side to 100 or less.

In this configuration, the host controller 20 compares the measured value of the steam temperature 102 on the outlet side of the superheater 1 with the temperature set value and adjusts the control output so that the two become equal. The output of the upper controller 20 is the set value of the lower controller 10 and is the set value of the inlet temperature of the superheater 1. Further, the lower controller 10 compares the set value calculated by the upper controller 20 with the temperature on the inlet side of the superheater 1 to adjust the flow rate of water or low-temperature steam blown into the steam.

[0012]

As described above, in the conventional desuperheater control apparatus, the upper controller 20 compares the steam temperature 102 at the outlet side of the superheater 1 with the set value 100, and determines the lower controller 10 Is calculated, the steam temperature 102 at the inlet side of the superheater 1 is calculated, and when the steam temperature 102 at the outlet side of the superheater 1 attempts to exceed the set value, the water flowing into the desuperheater 2 by the lower-order controller 10 is calculated. Alternatively, since the opening of the flow control valve V is controlled so that the flow rate of the low-temperature steam increases, the steam temperature on the outlet side of the superheater 1 can be set to an optimum value.

However, in such a desuperheater control system, depending on the operating conditions of the boiler, even if the flow rate of water or low-temperature steam blown into the desuperheater (hereinafter referred to as spray flow rate) is 0, the superheater 1 The steam temperature 102 on the outlet side may be lower than the temperature set value 100. In this case, since the spray flow rate is 0, the steam temperature 102 on the outlet side of the superheater 1 cannot be further increased only by controlling the desuperheater 2. For this reason, the upper controller 20 always has a positive control deviation, which causes a problem that the state quantity of the integration element 23 of the upper controller saturates and diverges.

In order to prevent this, it is conceivable to set upper and lower limits for the integral element 23 of the upper controller 20. However, even in this case, the steam temperature 1 at the outlet side of the superheater 1
Since the controllability of No. 02 greatly changes depending on the set value, there is a problem that adjustment for determining the set value is difficult.

The steam temperature 102 on the outlet side of the superheater 1
Exceeds the maximum value, it is not preferable in terms of the safety of the equipment. Therefore, there is a problem that the limit range is narrowed more than necessary and the upper and lower limits are set.

In addition, although there is an optimum value for the set value of the limit value, there is a problem in the desuperheater control device in the combined cycle plant that the optimum value differs depending on environmental conditions such as an outside temperature.

The present invention solves the above-described problems, the controller does not saturate or diverge, flexibly responds to changes in operating conditions and environmental conditions, and always keeps the steam temperature at the outlet side of the superheater good. It is an object of the present invention to provide a desuperheater control device that can control the temperature of the heater.

[0018]

According to the present invention, in order to achieve the above object, a desuperheater control device is constituted by the following means.

According to a first aspect of the present invention, there is provided a steam supply system for supplying steam generated by a boiler of a thermal power plant to a turbine, which is mixed into the steam from a supercooler provided on the inlet side of a superheater upstream of the turbine. In a desuperheater control device that lowers steam temperature by controlling the flow rate of water or low-temperature steam through a flow control valve, a deviation between the steam temperature at the outlet of the superheater and a temperature set value is integrated. A higher-level controller having an operation means including an integral element, and a lower-level controller that inputs an output of the higher-level controller as a set value and controls the flow rate control valve based on a deviation from an inlet-side steam temperature of the superheater. And when the output of the lower controller is equal to or less than a certain value, the input of the integral element is controlled so that the input of the integral element does not increase with respect to the deviation which is the input of the upper controller. It is provided with a limiting means to restrict the signal.

According to a second aspect of the present invention, there is provided a steam supply system for supplying steam generated by a boiler of a thermal power plant to a turbine from a supercooler provided on the inlet side of a superheater upstream of the turbine in the steam. In a desuperheater control device that lowers steam temperature by controlling the flow rate of water or low-temperature steam through a flow control valve, a deviation between the steam temperature at the outlet of the superheater and a temperature set value is integrated. A higher-level controller having an operation means including an integral element, and a lower-level controller that inputs an output of the higher-level controller as a set value and controls the flow rate control valve based on a deviation from an inlet-side steam temperature of the superheater. And when the flow rate of water or low-temperature steam mixed into the desuperheater is equal to or less than a predetermined value, the input of the integral element does not increase with respect to the deviation that is the input of the higher-level controller. Wherein is the input signal of the integral element which is provided a limiting means to restrict such.

According to a third aspect of the present invention, a steam generated in a boiler of a thermal power plant is mixed with the steam from a supercooler provided on the inlet side of a superheater upstream of the turbine in a steam supply system for supplying the steam to the turbine. In a desuperheater control device that lowers steam temperature by controlling the flow rate of water or low-temperature steam through a flow control valve, a deviation between the steam temperature at the outlet of the superheater and a temperature set value is integrated. A higher-level controller having an operation means including an integral element, and a lower-level controller that inputs an output of the higher-level controller as a set value and controls the flow rate control valve based on a deviation from an inlet-side steam temperature of the superheater. When the opening degree of the flow control valve for controlling the flow rate of water or low-temperature steam mixed into the desuperheater becomes less than a certain value, the deviation that is the input of the upper controller versus , In which the input of the integral element is provided with a limiting means to restrict the input signal of the integral element so as not to increase.

Therefore, in the desuperheater control apparatus according to the first to third aspects of the present invention, the flow rate of water or low-temperature steam sprayed from the desuperheater to the steam supply system is zero and the superheater is overheated. Even if the temperature at the outlet of the controller falls below a predetermined value, the signal input to the integral element of the host controller is limited, so that the host controller does not saturate or diverge, and is flexible to changes in operating conditions and environmental conditions. And the steam temperature can always be controlled well.

According to a fourth aspect of the present invention, in the temperature reducing apparatus control apparatus according to any one of the first to third aspects of the present invention, the limiting means has a hysteresis characteristic and the input signal of the integration element is switched. The frequent fluctuation of the output signal of the host controller due to the operation is suppressed.

According to a fifth aspect of the present invention, in the temperature control device of any one of the first to third aspects of the present invention, the limiting means determines whether or not to limit the signal of the higher-level controller. The limiting operation is performed under the condition that the determination condition has continued for a predetermined time or more.

Therefore, in the desuperheater control device according to the present invention corresponding to the fourth and fifth aspects, the first aspect of the present invention relates to the first aspect.
In addition to obtaining the same operation and effect as the invention corresponding to claim 3, even if the output of the lower controller oscillates around the set value of the upper controller, the integral element of the upper controller becomes unnecessary. Input switching can be prevented.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of a desuperheater control apparatus according to the present invention.
FIG. 7 is a configuration diagram showing an embodiment of the present invention, and the same parts as those in FIG.

In FIG. 1, reference numeral 1 denotes a superheater into which steam generated by a boiler (not shown) is introduced through a steam supply system.
The steam heated by the superheater 1 is supplied to a next-stage superheater or steam turbine (not shown) through a steam supply system.

Reference numeral 2 denotes a desuperheater provided in the steam supply system on the inlet side of the superheater 1. The desuperheater 2 has a nozzle for spraying water or low-temperature steam. A medium supply system is connected, and a flow control valve V is provided in the cooling medium supply system.

On the other hand, 30 is the steam temperature 102 at the outlet side of the superheater 1 measured by the thermometer T1 and the temperature set value 100.
Is input to the upper controller 30. The upper controller 30 compares the steam temperature 102 with the temperature set value 100.
1, a signal limiter 32 for limiting a deviation signal 101 between the steam temperature and the temperature set value input from the comparison unit 31 to 0 or a negative value, and fixed contacts Sa and Sb and a movable contact S
c, a switch 33 to which a deviation signal is inputted from the comparing section 31 to the fixed contact Sa and an output signal of the signal limiter 32 is inputted to the fixed contact Sb, and an output signal of the lower-level controller 10 which will be described later. When detecting that the value has become lower than a certain value, the switch 3
3, a switching command is given to the movable contact Sc from the fixed contact Sa side to the Sb side, and a deviation signal from the comparator 31 or a comparator 34 input through the switch 33.
And a PID calculator 35 for executing a PID calculation on the output signal of the above and outputting the calculation result as a set value.

Reference numeral 10 denotes a lower controller to which the steam temperature on the inlet side of the superheater 1 measured by the thermometer T2 and the set value output from the upper controller 20 are inputted. Set value input from host controller and superheater 1
The flow rate of water or low-temperature steam blown into the steam through the nozzle of the desuperheater 2 is controlled by adjusting the opening degree of the flow control valve V by comparing the flow rate with the steam temperature on the inlet side of the heater.

Here, the control of the desuperheater 2 is performed by the host controller 30.
Is a cascade configuration in which the output of the lower controller 10 is set as the output of the lower controller 10.

Next, the operation of the thus-configured temperature reducer control device will be described.

In FIG. 1, the host controller 30 compares the measured value of the steam temperature 102 on the output side of the superheater 1 with the temperature set value, and adjusts the control output so that the two become equal. The output of the upper controller 30 is the set value of the lower controller 10 and is the set value of the inlet temperature of the superheater 1.

Further, the lower controller 10 controls the upper controller 3
By comparing the set value calculated at 0 with the temperature on the inlet side of the superheater 1 and controlling the opening degree of the flow control valve V based on the deviation, the spray flow rate mixed into the desuperheater 2 is adjusted.

Here, in the higher-level controller 30, the comparator 34 determines whether the output of the lower-level controller 10
It is always compared whether it is below the% opening command value.

When the output of the lower order controller 10 exceeds the 5% opening command value by the comparator 34, the movable contact Sc of the signal switch 33 is connected to the fixed contact Sa side, and the comparison element 31 The output deviation signal is input to the PID calculator 35.

Therefore, when the output of the lower-level controller 10 exceeds the 5% opening command value, the spray flow rate of the temperature reducer 2 can be controlled by ordinary cascade control as in the conventional apparatus.

When the comparator 34 detects that the output of the lower order controller 10 has become equal to or less than the 5% opening command value, the switching contact causes the movable contact Sc of the signal switch 23 to move to the fixed contact Sb side. Then, the output signal of the signal limiter 34 is input to the PID calculator 35.

In this case, the signal limiter 34 sets the comparison element 3
The deviation signal 101 output from 1 is set to 0 having no positive value.
Or it is restricted to be negative.

Therefore, in the conventional desuperheater control device, even when the spray amount is 0, the steam temperature at the outlet side of the superheater 1 is not controlled.
When 2 is equal to or less than the set value, the comparison element 31 of the higher-level controller 30
The deviation signal output from the PID calculator 35 continues to take a positive value, causing the integrator of the PID calculator 35 to saturate and diverge.
In the present embodiment, the deviation signal 101 output from the comparison element 31 of the host controller 30 is limited by the signal limiter 32 to take 0 or a negative value. The state quantity does not increase, preventing the integrator from saturating and diverging.

As described above, in this embodiment, by detecting that the output signal of the lower-level controller 10 has become equal to or less than the 5% opening command value, it is possible to prevent water or low-temperature steam from being mixed into the desuperheater 2. However, an operation state in which the steam temperature 102 on the outlet side of the superheater 1 becomes equal to or lower than the set value is detected, and in this operation state, the deviation signal output from the comparison element 31 of the host controller 30 is set to 0.
Or, since it is restricted to take a negative value, PI
The amount of state of the integrator in the D calculator 35 does not increase, and saturation and divergence of the integrator can be prevented.

Therefore, in the actual operation state, the operation of the control device is switched while accurately grasping the operating conditions under which the operation of the desuperheater becomes unnecessary, so that the operation is not affected by changes in the atmospheric temperature or the fuel composition. It can flexibly respond to changes in operating conditions and environmental conditions, and can always perform good control.

In the conventional upper-level controller, when an integrator upper limit is provided, it is necessary to adjust the set value of the upper limit during a field test operation. Only the set value of the comparator 30 for detecting that the flow rate is near 0 does not greatly affect the control performance. For this reason, the adjustment work required in the conventional case can be omitted, and the adjustment work on site can be reduced.

FIG. 2 shows a second embodiment of the desuperheater control apparatus according to the present invention.
In the configuration diagram showing the embodiment, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Here, only different points will be described.

In the second embodiment, the host controller 40 has the following configuration. That is, as shown in FIG. 2, a comparison unit 41 that compares the steam temperature 102 with the temperature set value 100, a proportional element 42 to which a deviation between the steam temperature and the temperature set value is input from the comparison unit 41, Element 4
, A signal limiter 43 for limiting the signal obtained through the switch 2 to zero or a negative value, and fixed contacts Sa, Sb and a movable contact S.
c, a switch 44 to which a deviation signal from the proportional element 42 is input to the fixed contact Sa, and an output signal of the signal limiter 43 to the fixed contact Sb, and an output signal of the lower-level controller 10 is constant. When it is detected that the value has become equal to or less than the value, a switch command is given to the switch 44 to move the movable contact Sc from the fixed contact Sa side to S.
a comparator 45 for switching to the b side; an integration element 46 for integrating a deviation signal from the proportional element 42 input through the switch 44 or an output signal of the comparator 43;
And an adder 47 that adds the signal integrated through the proportional element and the signal obtained through the proportional element 42.

Next, the operation of the thus-configured desuperheater control device will be described.

In FIG. 2, the host controller 40 compares the measured value of the steam temperature 102 on the output side of the heater 1 with the temperature set value, and adjusts the control output so that both become equal. The output of the upper controller 30 is the set value of the lower controller 10 and is the set value of the inlet temperature of the superheater 1.

Further, in the lower controller 10, the upper controller 4
By comparing the set value calculated at 0 with the temperature on the inlet side of the superheater 1 and controlling the opening degree of the flow control valve V based on the deviation, the spray flow rate mixed into the desuperheater 2 is adjusted.

Here, in the higher-level controller 40, the comparator 45 determines that the output of the lower-level controller 10
It is always compared whether it is below the% opening command value.

When the output of the lower controller 10 exceeds the 5% opening command value by the comparator 45, the movable contact Sc of the signal switch 44 is connected to the fixed contact Sa side, and the proportional element 42 Integral element 4
6 is entered. The signal integrated by the integration element 46 and the signal obtained through the proportional element 42 are added to the addition unit 4
7 to give the lower controller 10 as a set value.

Therefore, when the output of the lower-level controller 10 exceeds the 5% opening command value, the spray flow rate of the temperature reducer 2 can be controlled by the normal cascade control as in the conventional apparatus.

When the comparator 45 detects that the output of the lower order controller 10 has become equal to or less than the 5% opening command value, the switching contact moves the movable contact Sc of the signal switch 44 to the fixed contact Sb side. Then, the output signal of the signal limiter 43 is input to the integration element 46. The signal integrated by the integration element 46 is added to the deviation signal obtained through the proportional element 42 by the addition unit 47, and is provided to the lower-level controller 10 as a set value.

In this case, the signal limiter 34
The deviation signal output from 2 is limited to 0, which does not have a positive value, or to be negative.

Therefore, in the conventional desuperheater control device, even when the spray amount is 0, the steam temperature at the outlet side of the superheater 1 is 10
2 is equal to or less than the set value, the proportional element 42
In this embodiment, the deviation signal output from the proportional element 42 of the host controller 40 is a signal limiter. 43 restricts the value to be 0 or a negative value, so that the state quantity of the integral element 46 does not increase, thereby preventing the integral element 46 from saturating and diverging.

Therefore, in the actual operating state, the operation of the control device is switched by accurately grasping the operating conditions under which the operation of the desuperheater becomes unnecessary, so that the operation is not affected by changes in the ambient temperature or the fuel composition. It can flexibly respond to changes in operating conditions and environmental conditions, and can always perform good control.

In the conventional upper-level controller, when an integrator upper limit is set, it is necessary to adjust the set value of the upper limit during a field test operation. Only the set value of the comparator 30 for detecting that the flow rate is near 0 does not greatly affect the control performance. For this reason, the adjustment work required in the conventional case can be omitted, and the adjustment work on site can be reduced.

FIG. 3 shows a third embodiment of the desuperheater control apparatus according to the present invention.
In the configuration diagram showing the embodiment, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. Here, only different points will be described.

In the third embodiment, as shown in FIG. 3, a spray flow meter 80 for measuring the flow rate of water or low-temperature steam flowing into the desuperheater 2 is connected to a refrigerant supply system, and the spray flow rate is measured. The measurement value measured by the device 80 is given to the comparator 45 of the host controller 40.
In this case, the comparator 45 detects whether or not the measured value of the spray flow rate measuring device 80 is equal to or less than a certain value, and gives a switching command to the signal switch 44 when detecting that the measured value is equal to or less than the certain value. is there.

In the temperature reducer control device having such a configuration, the measured value measured by the spray flow rate measuring device 80 is input to the comparator 45 of the host controller 40, so that the measured value of the comparator 45 is reduced. Evaluate whether it is below a certain value,
When it is detected that the value is equal to or less than the predetermined value, a switching command is given to the signal switch 44 to switch the movable contact Sc to the fixed contact Sb, so that the output signal of the signal limiter 43 is input to the integration element 46.

Therefore, the same function and effect as those of the first and second embodiments can be obtained.

In the temperature reducer control device having such a configuration, the measured value measured by the spray flow rate measuring device 80 is input to the comparator 45 of the host controller 40, so that the measured value of the comparator 45 is reduced. Evaluate whether it is below a certain value,
When it is detected that the value is equal to or less than the predetermined value, the movable contact Sc of the signal switch 44 is switched to the fixed contact Sb by the switching command, and the output signal of the signal limiter 43 is input to the integration element 46. The same operation and effect as in the second embodiment can be obtained.

Further, in the present embodiment, the comparator 45 operates not on the basis of the opening command value of the lower-level controller 10 but on the basis of the actual measured value of the spray flow rate. There is also an advantage that it can be performed more accurately.

FIG. 4 shows a fourth embodiment of the desuperheater control apparatus according to the present invention.
In the configuration diagram showing the embodiment, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. Here, only different points will be described.

In the fourth embodiment, the actual opening of the flow control valve 3 is detected as shown in FIG. 4, and the detected value is given to the comparator 45 of the host controller 40. In this case, the comparator 45 detects whether or not the opening degree of the flow control valve 3 is equal to or less than a certain value, and gives a switching command to the signal switch 44 when detecting that the opening degree is equal to or less than the certain value. is there.

According to the temperature reducer control device having such a configuration, by inputting the detected value of the opening of the flow control valve 3 to the comparator 45 of the host controller 40, the detected value of the opening of the comparator 45 is reduced. It is detected whether or not it is below a certain value, and when it is detected that it is below a certain value, a switching command is given to the signal switch 44, and the movable contact Sc is switched to the fixed contact Sb side to change the signal limiter 4
Since the output signal of No. 3 is input to the integration element 46, the same operation and effect as those of the above-described first and second embodiments can be obtained.

Further, in the present embodiment, the comparator 45 operates not on the basis of the opening command value of the lower controller 10 but on the basis of the actual opening detection value of the flow control valve 3, so that the first embodiment is performed. As compared with the second embodiment and the second embodiment, there is an advantage that the operation state can be grasped more reliably and the operation of the upper controller can be switched.

FIG. 5 shows a fifth embodiment of the desuperheater control apparatus according to the present invention.
In the configuration diagram showing the embodiment, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. Here, only different points will be described.

In the fifth embodiment, as a comparator for giving a switching command to the signal switching unit 44 in the higher-level controller 40, the fact that the output signal of the lower-level controller 10 has fallen below a certain value is accompanied by a hysteresis characteristic. And a hysteresis characteristic comparator 48 for detecting the temperature. In this case, the hysteresis characteristic comparator 48 has different set values depending on the output of the lower order controller 10, that is, when the opening command value increases and decreases, and the detection sensitivity differs.

With the temperature reducer control device having such a configuration, the hysteresis characteristic comparator 48 of the higher-level controller 40 detects whether or not the output signal of the lower-level controller 10 is below a certain value, and When the following is detected, the signal switch 4
4, the movable contact Sc is switched to the fixed contact Sb, and the output signal of the signal limiter 43 is input to the integration element 46. Therefore, the same operation as in the first and second embodiments described above. The effect can be obtained.

In this embodiment, the following operation and effect can be obtained as compared with the above-described second embodiment. That is, in the second embodiment, when the output signal of the lower-level controller 10 vibrates near the set value of the comparator 45, the comparator 45 operates in synchronization with the vibration, and the operation of the higher-level controller 40 decreases. It can be switched messy. On the other hand, in the present embodiment, the hysteresis characteristic comparator 4 is used as a comparator.
8, the maximum value of the output signal exceeds the upper set value of the hysteresis characteristic even if the output signal of the lower controller 10 oscillates around an arbitrary value, and the minimum value of the output signal is smaller than the hysteresis characteristic. As long as it does not fall below the lower set value of
It does not operate in synchronization with vibration. Therefore, it is possible to prevent the switching operation of the higher-level controller from being unnecessarily complicated as in the second embodiment.

FIG. 6 shows a sixth embodiment of the desuperheater control apparatus according to the present invention.
In the configuration diagram showing the embodiment, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. Here, only different points will be described.

In the sixth embodiment, as shown in FIG. 6, in the upper controller 40, a signal continuous detector 49 is provided on the output side of the comparator 45 to which the output signal of the lower controller 10 is input. The switching command is given from the signal continuation detector 49 to the signal switch 44. Here, the signal continuity detector 49 is provided by the comparator 45 to the lower controller 10.
When it is detected that the opening command value outputted from the controller becomes equal to or less than a predetermined value, a switching command is given to the signal switch 44 on condition that the output continues for a predetermined time or more.

With the temperature reducer control device having such a configuration, the comparator 45 of the higher-level controller 40 detects whether or not the output signal of the lower-level controller 10 is equal to or less than a certain value. When detecting that there is, the signal continuity detector 49 gives a switching command to the signal switch 44 on condition that the output of the comparator 45 has continued for a certain time or more, and switches the movable contact Sc to the fixed contact Sb side, Since the output signal of the signal limiter 43 is input to the integration element 46, the same operation and effect as those of the above-described first and second embodiments can be obtained.

In this embodiment, the following operation and effect can be obtained as compared with the above-described second embodiment. That is, in the second embodiment, when the output signal of the lower-level controller 10 vibrates near the set value of the comparator 45, the comparator 45 operates in synchronization with the vibration, and the operation of the higher-level controller 40 decreases. It can be switched messy. On the other hand, in the present embodiment, the switching command is provided to the signal switch 44 by the signal continuity detector 49 provided on the output side of the comparator 45 only when the output of the comparator 45 continues for a certain time or more. Therefore, even when the output of the lower-level controller 10 vibrates near an arbitrary value, it does not operate in synchronization with the vibration.

Therefore, it is possible to prevent the switching operation of the host controller from being more complicated than necessary as in the second embodiment.

In each of the above embodiments, the case where the deviation signal input to the integration element is positive is taken as an example, and the input signal of the integration element is limited to 0 or a negative value by the signal limiter. However, it goes without saying that if the deviation signal input to the integration element is negative, the input signal is limited to 0 or a positive value.

[0078]

As described above, according to the present invention, the controller does not saturate or diverge, flexibly responds to changes in operating conditions and environmental conditions, and always keeps the steam temperature at the outlet side of the heater good. And a desuperheater control device capable of controlling the temperature of the heater.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a desuperheater control device according to the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of a desuperheater control device according to the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of a desuperheater control device according to the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of a desuperheater control device according to the present invention.

FIG. 5 is a configuration diagram showing a fifth embodiment of a desuperheater control device according to the present invention.

FIG. 6 is a configuration diagram showing a sixth embodiment of a desuperheater control device according to the present invention.

FIG. 7 is a configuration diagram showing an example of a conventional desuperheater control device.

[Explanation of symbols]

 1: Superheater 2: Desuperheater 3: Flow control valve 10: Lower controller 30, 40: Upper controller 31, 41: Comparative element 42: Proportional element 32, 43: Signal limiter 34, 45: Comparator 33 , 44: signal switch 35: PID calculator 48: hysteresis characteristic comparator 49: continuous time detector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G071 AB01 BA10 BA31 CA07 DA00 EA02 EA05 FA05 FA06 HA05 JA00 3G081 BA02 BA11 BB00 BC07 DA01

Claims (5)

[Claims] The present invention relates to a thermal power plant, and a desuperheater provided on a turbine inlet side of a steam supply system for supplying steam generated by a boiler of a steam power plant or an exhaust heat recovery boiler of a combined cycle plant to a turbine. By controlling the flow rate of water or low-temperature steam mixed into the steam through a flow rate control valve, a temperature reducer control device that lowers the steam temperature, comprising: A higher-level controller having an operation means including an integration element for integrating the deviation, an output of the higher-level controller being input as a set value, and controlling the flow rate control valve based on a deviation from the inlet-side steam temperature of the turbine. A cascade configuration including a lower-order controller, and when the output of the lower-order controller is equal to or less than a certain value, the state quantity of the integral element increases with respect to the higher-order controller. Desuperheater control device, characterized in that the provided limiting means to limit the input signal of the integral element so as not to. 2. A temperature reducer provided on a turbine inlet side of a steam supply system for supplying steam generated by a boiler of a steam power plant or an exhaust heat recovery boiler of a combined cycle plant to a turbine in a thermal power plant. By controlling the flow rate of water or low-temperature steam mixed into the steam through a flow rate control valve, a temperature reducer control device that lowers the steam temperature, comprising: A higher-level controller having an operation means including an integration element for integrating the deviation, an output of the higher-level controller being input as a set value, and controlling the flow rate control valve based on a deviation from the inlet-side steam temperature of the turbine. A cascade configuration including a lower controller, and the upper controller when the flow rate of water or low-temperature steam mixed into the desuperheater is equal to or less than a certain value, Serial integral element desuperheater control apparatus characterized by the state quantity is a limit means to limit the input signal of the integral element so as not to increase the. 3. A temperature reducer provided at a turbine inlet side of a steam supply system for supplying steam generated by a boiler of a steam power plant or an exhaust heat recovery boiler of a combined cycle plant to a turbine in a thermal power plant. By controlling the flow rate of water or low-temperature steam mixed into the steam through a flow rate control valve, a temperature reducer control device that lowers the steam temperature, comprising: A higher-level controller having an operation means including an integration element for integrating the deviation, an output of the higher-level controller being input as a set value, and controlling the flow rate control valve based on a deviation from the inlet-side steam temperature of the turbine. A cascade configuration including a lower-order controller, and the opening degree of a flow control valve that controls the flow rate of water or low-temperature steam mixed into the desuperheater falls below a certain value. To said host controller when Tsu, the integral element desuperheater control device, characterized in that the state quantity is a limit means to limit the input signal of the integral element so as not to increase the. 4. The superheater control device according to claim 1, wherein the limiter has a hysteresis characteristic, and the upper controller is controlled by a switching operation of an input signal of the integration element. A desuperheater control device characterized by suppressing frequent fluctuations of an output signal. 5. The desuperheater control device according to claim 1, wherein the limiter determines whether or not to limit the signal of the higher-level controller by a predetermined time or more. A desuperheater control device, wherein a limiting operation is performed on condition that the operation is continued.