JPS63121901A - Process controller - Google Patents

Abstract

PURPOSE:To stably control the water level after switching by regulating valve signals of a control system in normal service and an emergency control system with each other and switching signals of gradually opening and gradually closing signal generators and the regulating part output signal of the control system in normal service by the signal from this controller and a control system switching signal. CONSTITUTION:In case the regulating part output of the control system in normal service is given to a regulating valve 9 of an emergency control system to switch the regulating valve control state of the control system in normal service to that of the emergency control system or the control state of the regulating valve 9 of the emergency control system controlled by the regulating part output of the control system in normal service is switched to that of a regulating valve 5 of the control system in normal service, the regulating valve 5 which is in the automatic control state before switching is kept in this state as it is and the other regulating valve 9 is forcibly gradually opened up to a middle degree of opening, and the regulating valve 5 kept in the automatic control state is forcibly gradually closed and the forcibly gradually opened regulating valve 9 is switched to the automatic control state due to a regulating part of the control system in normal service when the degree of opening of the regulating valve 5 kept in the automatic control state is lower than that of the forcibly gradually opened regulating valve. Thus, the water level stable state is secured to switch control system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a process control device, and more particularly to a process control device having a regular control system and an emergency control system for backing up the regular control system as one control target.

[Conventional technology]

Industrial process conditions such as temperature, pressure, flow rate, liquid level, safety, etc.
In process control using weight as a controlled variable, it is often seen that a regular control system and an emergency control system are installed in parallel for one controlled object. The regular control system is generally used to manage control during normal operation, and the emergency control system is used to control the process status x during plant startup and shutdown, etc.
When i changes and the regular control system is unable to control it, it is substituted by the regular control system. ■When the process state quantity exceeds the normal range and becomes abnormal, the regular control system alone is insufficient to deal with it. This will be installed for purposes such as backing up this with an emergency control system.

There are various examples of process control, but here we will discuss drain water level control of a feed water heater that heats boiler feed water using turbine oil for power generation equipment.

In some conventional process control devices of this type, when switching from a regular control system to an emergency control system, the emergency control system remains automatic and the control valve of the regular control system is forced to fully close and slowly close. A control device that automatically shifts control to the emergency control system due to a rise in the water level, and when switching from the operating state of the emergency control system to the regular control system, the emergency control system remains automatic and the regular control system adjustment section A full valve open signal is given to the low level signal selector installed on the exit car side to force the control valve to gradually open, and as the water level falls, the control valve of the emergency control system is fully closed and the normal control system is adjusted. As soon as the section calculation signal becomes lower than the control valve gradual opening signal (in the direction of suppressing the valve gradual opening), the control section output is selected by the low level signal selector and the control device shifts to automatic control by the control section of the regular control system. Are known.

(Japanese Patent Publication No. 53-47841) [Problems to be Solved by the Invention] The above-mentioned prior art is considered to be an effective means when control switching is performed in the same load range in the turbine operating state. However, the timing of control switching is not carried out arbitrarily, so when switching from the normal control system to the emergency control system, the control valve of the normal control system is forcibly closed gradually to raise the water level, and the water level of the emergency control system is increased. In the method in which the emergency system controller increases the output and controls the emergency control valve after the water level exceeds the controller set value, condensate is often generated in the high load range, so the water level rise rate is high. Due to the delay in the operation of the control system, there was a risk that the condensate would exceed the setting value of the control part by a wide margin, and the condensate would flow back into the turbine through the bleed pipe and damage the turbine. Also, when switching control from the emergency control system to the regular control system, the output of the regular controller decreases after the control valve of the regular control system is forcibly opened gradually and the water level falls below the constant value of the control section. When the signal becomes smaller than the gradual opening signal, the low-level signal selector switches control to the regular controller, but there is a problem in that the water level fluctuations become large due to the delay in the operation of the regular controller.

An object of the present invention is to provide stable water level control after switching even when switching control systems under arbitrary plant operating conditions.

[Means for solving problems]

The above purpose is to provide an output line of the control section of the regular control system and a control line branching from the control section to the high-level signal selector of the emergency control system, and on that line, a valve open signal generator and a valve close signal generator are installed. A signal comparator is provided to compare the control valve signals of the regular control system and the emergency control system, and the signal from the control system and the control system switching signal are used to compare the signal from the gradual opening and gradual closing signal generator. This is achieved by switching the regulator output signal of the regular control system.

In addition, a gradual opening and closing signal generator is installed on each side of the control section of the regular and emergency control systems, and a signal comparator is also installed to compare the control valve control signals of the regular and emergency control systems. In addition to switching the gradual open and gradual closing signal generator signals and the output signals of each adjustment section using the signal from the device and the control system switching signal, a tapping path is provided to switch the setting value of the emergency system adjustment section, and This is achieved by detecting that the control valve of the emergency control system is fully closed when switching from the control system to the regular control system and restoring control to control using the control unit output signal.6 [Operation] Constructed by the above-mentioned means The process control switching device is
The control system that was in the automatic control state at the time of the control change command causes the control system that was in the automatic control state to continue its control state, and the control valves of the other control systems are set to intermediate openings (for example, the control valves of the control system that were in the automatic control state at the time of the changeover) are Forced to gradually open the valve to an opening equivalent to 60% of the opening.

When the opening of the control valve that is continuing the automatic control state becomes equal to or less than the opening of the control valve of the other control system that is being forced to gradually open, the control valve enters the automatic control state and the control valve is forced to gradually close and is now in the automatic control state. The control valve, which had been forced to gradually open until now, is switched to automatic control using the control section signal.

In addition, the process control switching device of the above-mentioned means, which is provided with a gradual opening/slow closing signal generator on each of the output sides of the adjustment section of the regular and emergency control systems, operates in the same manner as described above, and also operates in the same manner as above. When the control valve becomes gradually open, change the set value to the control section to a value equivalent to NWL, and when the control valve becomes gradually closed, change the set value to the control section to a value equivalent to NWL + 50 -. When the valve is switched and the valve is fully closed, it operates to restore the control state based on the control section signal.

As a result, the water level can always be controlled to a constant NWL, and since both valves are switched at an intermediate opening state, the disturbance caused by switching can be minimized, improving plant safety and operability. be able to.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 8.

FIG. 8 is a system diagram showing the feed water heater water level control device.

The feed water heater 50 heats the feed water 51 using turbine bleed air 52, and the turbine oil gas 52 becomes drain (hot water) through heat exchange and is stored in the feed water heater 50. The water level detector 1 for detecting the water level of this drain is the feed water heater 50.
attached to.

The drain is sent to the lower feed water heater or condenser through the water level control valves 5 and 9 installed on the drain pipe 53.

The control of these water level control valves 5 and 9 is performed as follows, as shown in the control system diagram of FIG.

The output signal of the water level detector 1 is sent to the deviation calculator 2 of the regular control system and compared with a set value (signal corresponding to NWL), and the deviation signal is sent to the PID calculator 3. The deviation signal is PI
Proportional, integral and differential calculations are performed in the D calculator 3, and transmitted to the water level control valve 5 via the electric/pneumatic converter 4 as a valve open/close signal.
The output signal of the water level detector l is sent to the deviation calculator 6 of the emergency control system and set value (for example, NWL+50+
+s) and its deviation signal is PID
The signal is sent to the arithmetic unit 7. The deviation signal is subjected to proportional, integral, and differential calculations in the PID calculator 7, and is transmitted to the water level control valve 9 via the electro-pneumatic converter 8 as a valve open/close signal. However, PID
A signal to open the water level control valve 9 is issued only when the output signal water level of the calculator 7 rises and exceeds the set value of the deviation calculator 6 (corresponding to NWL+50m).

Therefore, when the water level is controlled to NWL in the regular control system, the output signal of the PID calculator 7 in the emergency control system is a valve fully closed signal, and the water level control valve 9 is in a fully closed state. The configuration and operation up to 0 or more are basically the same as the conventional one, but the difference from the conventional configuration is that a gradual closing signal generator 13 is provided between the PID calculator 3 of the regular control system and the water level control valve 5. A signal switch 12, a gradual opening signal generator 21, and a signal switch 20 are provided, and a branch line from the PID calculation 93 of the regular tul system to the PID calculation unit 7 output line of the emergency control system is provided on the line. A gradual opening signal generator 11 and a signal switch 10 are further provided, and a gradual closing signal generator 23 and a signal switch 22 are installed, and a high-level signal selector 24 for signal selection between the signal 34 and the PID device 7 signal is connected to the PIDID calculator 1. What was installed on the output line, and.

In addition to the 5-valve → 9-valve switching command and the 9-valve → 5-valve switching command, a valve opening signal to the water level control valve 5 of the regular control system and a water level adjustment of the emergency control system are sent to provide interlock conditions to the above device. A signal comparator 25 is provided to compare the valve opening signal to the valve 9. Fig. 2 shows the internal configuration of the gradual opening signal generator, and Fig. 31i1 shows its operation diagram. Further, FIG. 4 shows an internal configuration diagram of the gradual closing signal generator, and FIG. 5 shows its operation diagram.

FIG. 6 shows the valve operation by switching the control valve.

The function and control operation of the constituent instruments according to claim 1 will be explained below. When the water level is controlled by the regular control system,
That is, if a 9-valve → 5-valve switching command exists, the 5-valve switching command exists.
The valve→9 valve switching command has been canceled, and the AND circuits 40 and 41 are in the OFF state. The signal switching devices 10 and 12 to which the signals are transmitted are switched to the side where the outputs of the PID calculator 3 are introduced to the signals 31 and 33. Furthermore, the signal comparator 25 is in the OFF state m (value M of the signal 32 of the regular control system).
Since V 1 is OFF, which is larger than the value M V x of the emergency control system signal 35, the AND circuit 42 is also OFF.

The signal switch 20, which is the destination thereof, is switched to the side that leads the value of the signal 31 to the signal 32. On the other hand, AND circuit 4
3 is in the ON state because the signal of the signal comparator 25 is guided through the NOT circuit 45, and the signal switch 22, which is the transmission destination, is on the side that guides the output of the slow closing signal generator 23 to the signal 34. It has been switched. When a 5-valve → 9-valve switching command is generated in the above state, the 9-valve → 5-valve switching command is canceled, the AND circuit 43 is turned off, and the signal switch 22 is the side that guides the value of the signal 33 to the signal 34. can be switched to At the same time, the AND circuit 40 that guides the signal of the signal comparator 25 via the NOT circuit 44 is turned on and the signal switch 1
0 is switched to the side that leads the output of the gradual opening signal generator 11 to the signal 33.

The other signal switches 12 and 20 remain as described above.

The gradual opening signal generator 11 is connected to an AND circuit 4 as shown in FIG.
At the same time that 0 turns ON, the output value of the PID calculator 3 is held by the signal holder 60, and the output value is reduced by the calculator 61 to, for example, 60%, and the value is sent to the rate converter 63 via the signal switch 62. As shown in FIG. 6, the valve open signal is generated by increasing at a constant rate from the fully closed valve to the output of the calculator 61. (When the AND circuit 40 is OFF, the 0% value is guided to the rate converter by the signal switch 62 and becomes the valve fully closed signal.) This gradual opening signal of the gradual opening signal generator 11 is selected by the high level selector 24. , is guided to the water level control valve 9 via the electro-pneumatic converter 8, and the valve is gradually opened to a specified opening degree. When the water level control valve 9 opens, the output of the PID calculator 3 decreases, and the water level control valve 5 is controlled in the closing direction. (Since the water level is about to drop when the water level control valve 9 opens, it works to control the water level to NWL) Due to these operations, the value M V s of the signal 32 becomes smaller than the value M V z of the signal 35. The signal comparator 25 is turned on. Since the AND circuit 41 is turned on by the ON signal of the signal comparator 25, the signal switch 12 changes the output of the gradual closing signal generator 13 to signal 3.
1, and the gradual closing signal generator 13 gradually closes the water level control valve 5 until it is fully closed. Gradual closing signal generator 1.
3 is as shown in FIG.
The output of PID calculator 3 that was being given to
By introducing the % signal (valve fully closed signal) to the rate converter 66, a gradual closing signal as shown in FIG. 5 is generated when the valve is fully closed at a constant rate compared to the previously controlled valve opening. Also, since the AND circuit 40 is turned off by the ON signal of the signal comparator 25, the signal switch 10. The output of the PID calculator 3 is the signal 33
The water level control valve 9 of the emergency control system is automatically controlled by the PID calculator 3. As described above, since the control system is switched while the water level is being controlled by the NWL, stable switching is possible.

Next, when a 9-valve → 5-valve switching command is issued from the above control state, the 5-valve → 9-valve switching command is canceled and the AND circuit 41
is in the OFF state, and the signal switch 12 is switched to the PID calculator 3.
is switched to the side that leads the output of the signal to the signal 31. At the same time, the signal of the signal comparator 25 (because the water level control valve 5 is fully open and the water level control valve 9 is under automatic control, the signal comparator 25 is M V 1
< M V x is established and is in the ON state).
0 is switched to the side that leads the output of the gradual opening signal generator 21 to the signal 32. The other signal switches 10 and 22 are kept in the state described above. The water level control valve 4 is activated by the gradual opening signal from the gradual opening signal generator 21 (the signal is generated by the same device and operation as the aforementioned gradual opening signal generator 11). By opening the water level control valve 5, which gradually opens to a specified opening degree, the output of the PID calculator 3 decreases, and the water level control valve 9 of the emergency control system is controlled in the closing direction. Due to these operations, the value M V x of the signal 32 changes to the value M V x of the signal 35
It becomes larger than V x and the signal comparator 25 turns OFF.

Since the signal comparator 25 is turned off, the AND circuit 4
2 is also turned OFF, the signal switch 20 is switched to the side that leads the output of the signal 31 to the signal 32, and the water level control valve 5 is controlled by the output of the PID calculator 3. Also, the signal of the signal comparator 25 is set to N.

The AND circuit 43 introduced via the T circuit 45 is
The N state is entered, and the signal switch 22 is switched to the side that leads the output of the gradual opening signal generator 23 to the signal 34. Water level control valve 9
is determined by the output of the gradual closing signal generator 23, and the high-level signal selection 24
It is then gradually closed until it is fully open via an electric/pneumatic converter. (The internal operation of the gradual closing signal generator 23 is the same as that of the aforementioned gradual closing signal generator 12, so it will be omitted.) In the unlikely event that the water level control valve 9 is in the gradual closing process due to the valve 5 → valve 9 switching command. When the water level suddenly rises and exceeds the set value of the deviation calculator 6 of the emergency control system at the time when the water level is fully open or when the water level is fully open, the output signal of the PID calculator 7 is output to the water level control valve 9 selected by the high level selection 24. Open control. As described above, since the control system is switched while the water level is being controlled by NWL, stable switching is possible, and the function of the emergency control system, which is a backup system, can also be ensured.

FIG. 7 shows an embodiment of claim 2, and the same parts as in FIG. 1 of claim 1 are designated by the same reference numerals. The difference from FIG. 1 is that the gradual opening signal generator 11. The gradual closing signal generator 23 and the signal switch 10.22 are provided directly on the output signal line of the PID calculator 7 of the emergency control system, and the PID calculator signal to the gradual opening signal generator 21 is
Introducing the output signal of the arithmetic unit 7. And the emergency control system is equipped with setting devices 78, 79 and signal switching devices 77,
A hold circuit 80 composed of an R circuit 75 and a wipeout 76 (a function that turns off the hold signal when an external signal is present) is provided, and this circuit receives the signal from the AND circuit 40 and the A
A signal from the ND circuit 43 is introduced to switch the set value to the deviation operator 6 of the emergency control system. Furthermore, a monitor relay 70 is provided to detect that the value of the signal 34 of the emergency control system is a fully closed valve, and the signal and the 5-valve → 9-valve switching command are held by an OR circuit 71 and a wipeout 72. leads to the circuit 81, passes through the NOT circuit 73, and
This is what has been introduced into the circuit 43. The operation of these device configurations will be explained below.

When the AND circuit 40 is turned ON by the 5-valve → 9-valve switching command, the signal switching 10 is switched to the side that leads the output of the gradual opening signal generator 11 to the signal 33, but at the same time, the AND circuit is connected to the hold circuit 80. 40 is led, and the signal switch 77 is switched to the side where the value of the setter 78 (a value corresponding to NWL) is given as the set value of the deviation calculator 6. The ON signal of the hold circuit 80 continues even when the AND circuit 40 becomes OFF, and turns OFF when the signal of the AND circuit 43 introduced into the wipeout 76 becomes ○N.
It becomes F. When the signal to the signal switch 77 turns OFF, the setting value 79 (value equivalent to NWL + 50 mm) is switched to the side given as the setting value to the deviation calculator 6. 0th valve 9th valve → 5th valve When the water level control valve 9 becomes fully open while the AND circuit 43 is issuing a signal to gradually close the water level control valve 9 based on a switching command (the water level control valve 5 is in a controlled state based on the output of the PID calculator 3). Then, the monitor relay 70 detects this and transmits an ON signal to the hold circuit 81. Accordingly, the signal of the hold circuit 81 is changed to N
The signal of the AND circuit 43 introduced via the OT circuit 73 is turned off, and the signal switch 22 is switched to the PID calculator 7.
The water level control valve 9 is switched to the control side by the output.

The ○N signal of the hold circuit turns OFF when the wipeout 72 is given a 5-valve → 9-valve switching command. With this circuit, it is possible to detect that the original switching from the emergency control system to the regular control system has been completed in response to a 9-valve → 5-valve switching command, and to return to the original backup function of the emergency control system.

With the above device, almost the same effects as in the first embodiment can be obtained.

In the above detailed description of the present invention, the case where the control system is electrical is described, but it can also be used when the control system is pneumatic.

In addition, in explaining the present invention, the PID calculator 3, 7 signal switch, 10, 12, 20° 22, gradual opening signal generator 11
, 21, gradual closing signal generators 13, 23, signal comparator 25,
Parts are displayed for each element such as AND circuits 40 to 43 and NOT circuit 45, but it is clear that when these control calculations are performed by a digital control device, they are replaced by a software program having the above-mentioned functions. be.

〔Effect of the invention〕

According to the present invention, it is possible to maintain constant water level control using a water level control valve in one control system during the switching process, and it is possible to switch control systems while ensuring a stable water level even under any condition of plant operation. Therefore, it has the effect of improving the safety and operability of the plant. Further, in the control state of the regular control system, the function of the emergency control system as a backup is ensured as in the past.

[Brief explanation of the drawing]

Fig. 1 is a control system diagram of a feed water heater water level control device showing an embodiment of the present invention, Fig. 2 is an internal configuration diagram of the gradual opening signal generator in Fig. 1, and Fig. 3 is an explanation of its operation. Figure 4 is the first
An internal configuration diagram of the gradual closing signal generator in the figure, FIG. 5 is an explanatory diagram of its operation, FIG. 6 is a diagram of the control valve operation during switching, and FIG. 7 is a feed water heater showing another embodiment of the present invention. Control System Diagram of Water Level Control Device FIG. 8 is a system diagram showing a feed water heater water level control device as an example of process control. 2.6... Deviation calculator, 3,7... PID calculator,
5゜9... Water level control valve, 11.21... Gradual opening signal generator. 13.22... Gradual closing signal generator, 24... High level signal selector, 25... Signal comparator, 60... Signal holder-61... Arithmetic unit, 63.66... rate converter,
7o...Monitor relay, 80.81...Hold circuit, 78. -=1・1,'Go':,;)

Claims (1)

[Claims] 1. A detection section that detects the control amount of the process control target, an adjustment section that receives the signal from this detection section, compares it with a target value, and performs appropriate control calculations on the result, and a control section that receives the signal from this adjustment section. In a control device that has a regular control system consisting of a control valve that acts on a controlled object, and another emergency control system for that controlled object, installed in parallel, the output of the regulator of the regular control system is transferred to the emergency control system. from the control valve control state of the normal control system to the control valve control state of the emergency control system, or from the control valve of the emergency control system controlled by the regulator output of the normal control system to the control valve control state of the normal control system. When switching to the control valve control state, the control valves that were in the automatic control state before switching continue to be in the automatic control state, and the other control valves are forced to gradually open to an intermediate opening, and the control valves that were in the automatic control state before switching are forced to gradually open to an intermediate opening degree. When the opening degree of the valve falls below the opening degree of the control valve that has been forced to gradually open, the control valve that has been under automatic control until now is forced to gradually close, and the control valve that has been forced to gradually open until now is forced to gradually close. A process control device characterized in that the control valve is configured to be switched to an automatic control state by a control section of a regular control system.