JPH03123909A - Abnormality diagnostic controller - Google Patents

Abstract

PURPOSE:To previously prevent a unit trip by continuously supervising the change of amplitude in the hunting state of a feedback signal in a feedback control system, judging it to be a divergent hunting state when amplitude is in an increase direction by more than a specified value, giving an alarm and saving the control system to a safe direction such as a manual mode. CONSTITUTION:A turbine at the time of loading, the switching of motor driving/ water supply pumps 7 and 8 and fluctuation of water supply when recirculation pumps 26-28 are closed influence the control, for example. Namely, the sudden change of a sawtooth water supply quantity 20 when the valves are opened comes to the disturbance of the feedback control system but it is normally arranged at once. If a plus error occurs owing to the other cause and if the correction of an opening command 21 and the actual mechanical operation timing of the valves are shifted when the valves 26-28 are opened, the water supply quantity 20 becomes divergent hunting state, and the unit may trip. Thus, an abnormality diagnostic circuit 29 where the water supply quantity 20 being the feedback signal of the control system is set to be input is added and the alarm is generated at an initial stage.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an abnormality diagnosis device for an automatic control device consisting of a return control system, and in particular to an optimal system for water supply control devices used in steam generators in thermal power plants, etc. The present invention relates to an abnormality diagnosis device.

[Conventional technology]

In a conventional system, as described in Japanese Patent Publication No. 63-685, a water supply pump for a steam generator (for example, a boiler) is comprised of a plurality of pumps with different drive systems, such as turbine drive and motor drive. When the output of the steam generator is low, the motor-driven feed water pump (M-RFP) is mainly used, and in the process of increasing the output, the turbine-driven feed water pump (T-RFP) is used.
BFP). Conventionally, this switching operation was performed manually by an operator. A turbine-driven water pump controls the water pump flow rate based on the turbine rotation speed.

When the rate of increase in the turbine rotational speed is increased, the flow rate increases rapidly and the boiler feed water flow rate increases. Fluctuations in water supply to boilers are strictly limited due to requirements for protecting the main engine of the boiler and turbine, and an interlock is activated that trips the boiler and turbine when the deviation exceeds a specified value. In addition, the boiler trip interlock is activated to protect the boiler from running dry when the water supply drops.However, the switching operation of the water supply pump must be performed carefully and over a long period of time by an experienced operator. It was being done.

In response to this, in recent years, devices have been proposed that automatically switch the water supply pump depending on availability, such as the system shown in FIG. 2.

Steam generated in the boiler 1 is introduced into the turbine 3 through the main steam pipe 2, drives a generator (not shown), and is then sent to the condenser 4 and returned to water. The pressure of this condensate is increased by a low-pressure condensate pump 5 and a high-pressure condensate pump 6, and the pressure is further increased by a turbine-driven water pump (T-BFP) 7 and a motor-driven water pump (M-BFP) 8, and then the water supply pipe 10 is Water is supplied to the boiler 1 through the boiler. Typically, water pumps include
2 turbine-driven water pumps and 1 motor-driven water pump
A total of three machines will be used. When starting the turbine,
The motor-driven water pump 8 is operated and the turbine is at 20%
The turbine-driven water supply pump 7 is operated when the output power is increased. In the adder 12, the boiler feed water flow rate is subtracted from the set value. This output becomes a control signal for the main controller 13. At the start of startup, the controller 16 is turned on, so the main controller 13 only controls the water supply regulating valve 9. As mentioned above, when the generator output increases, the water supply control is transferred from the water supply regulating valve 9 to the turbine controller, and then
Turn off the controller 18.

Therefore, the output of the main controller 13 is sent to the turbine control,
Controls the amount of turbine steam for the turbine-driven water supply pump 7.

Furthermore, the detailed system configuration of the boiler water supply control system is shown in FIG. The turbine-driven water pump 7 and the motor-driven water pump 8 must be supplied with a minimum flow rate of water for the purpose of protecting the pumps, and recirculation valves 26 to 28 are installed on the pump discharge side.

This recirculation valve is an on-off valve that closes sequentially as the discharge flow rate of the pump increases, and closes sequentially as the discharge flow rate decreases, but when it opens and closes, it appears as a fluctuation in the water supply flow rate.

Therefore, in order to reduce fluctuations in the water supply control system, the opening command 21 is corrected by the opening of the recirculation valve branch bone - Xa% at the same time as the opening/closing command.

Figure 4 shows the switching of the A-C water supply pumps when the load is increased and the effect on the water supply flow rate when the recirculation valve is opened and closed at that time. This sawtooth sudden change in the water supply flow rate when the valve is opened becomes a disturbance to the return control system, but normally it settles down quickly.

However, if there is a deviation when opening, or if there is a difference between the correction of the opening command 21 and the actual mechanical operation timing of the recirculation valve, the sudden change in the water supply flow rate will result in divergent hunting, resulting in a unit rip. There are cases.

FIG. 5 shows the water supply flow rate 20 at T when the recirculation valve is closed.

It shows a normal fluctuation that suddenly changes from then settles.

FIG. 6 shows the water supply flow rate 20 at T when the recirculation valve is closed.

There is a sudden change from then on, and hunting continues with one divergence, and at the timing of Tt, the flow rate drops below the unit trip level, which is below the boiler's dry firing protection flow rate, indicating a unit trip change.

[Problem to be solved by the invention]

The above conventional technology has the advantage that even if the system enters a divergent hunting state due to a disturbance in the return control system, this abnormality is detected early, the system is returned to a stable state, and unit trips are prevented. There was no consideration given to this, and there were problems that led to unit trips.

An object of the present invention is to detect a divergent hunting state in a return control system at an early stage and diagnose the abnormality, thereby evacuating the control system in a safe direction and preventing unit tripping.

[Means to solve the problem]

In order to achieve the above object, the changes in the amplitude of the return signal of the return control system in the hunting state are continuously monitored, and if the amplitude increases beyond a specified value, it is diagnosed as a divergent hunting state. In addition to issuing a warning, the control system is evacuated to a safe direction (manual mode, etc.) to prevent unit tripping.

[Effect]

Continuously monitor the waveform change in the hunting state of the return signal of the return control system, find the first wave amplitude from the hold value of the first wave maximum value hold circuit and the minimum value hold circuit, and calculate the maximum value of the second wave. The second wave amplitude is obtained from the hold circuit and the minimum value hold circuit, and as for the third wave amplitude, the hold value of the first wave amplitude detection circuit is reset and detected, so the previous amplitude and current amplitude are continuously detected. Understood, changes in amplitude can be continuously monitored. As a result, if the change in amplitude becomes larger than the normal value, it can be diagnosed that the return signal is in a divergent hunting state, so an alarm is issued and the control system is changed from automatic return control mode to manual mode. It is possible to evacuate in a safe direction and prevent unit tripping.

As an alternative, even if the control deviation becomes larger than the normal value, it can be assumed that there is an abnormality in the control loop and the return signal is in a divergent hunting state, but it is difficult to diagnose in the initial state of hunting, and detection is difficult. is often delayed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing an example of the abnormality diagnosis circuit of the present invention, and corresponds to the abnormality diagnosis circuit 19 of the water supply pump automatic switching device which is an embodiment of the present invention shown in FIG. FIG. 3 shows the configuration and operation explained in the section of the prior art, especially the A-C turbine and motor-driven water supply pump 7 when the load is increased.
．． 8 and the fluctuations in the water supply flow rate 20 when the recirculation valves 26 to 28 are opened and closed pose a control problem, and the effects thereof are shown in FIG. This sudden change in the sawtooth water supply flow rate 20 at the time of opening causes a disturbance in the return control system, but normally it settles down quickly. However, when the recirculation valves 26 to 28 are closed, a deviation occurs due to another factor, and the correction 17 of the opening command 21 and the actual recirculation valve 2
If the mechanical operation timing of 6 to 28 is off,
The water supply flow rate 20 becomes divergent type hunting, and unit 1-
It may become a lip. Therefore, we added an abnormality diagnosis circuit 19 that inputs the water supply flow rate 20, which is the return signal of the control system, to diagnose the abnormality and issue an alarm at the initial stage of divergent hunting, and to switch the control system from automatic return control mode. Evacuation in a safe direction, such as manual mode, prevents unit tripping.

The abnormality diagnosis circuit shown in FIG. 1 receives the water supply flow rate 20 as an input, and the first (, 3, 5, . . .
・) The maximum value OA and minimum value OA of the wave are set by the high signal selector 52.
The low signal selector 54 selects the second (.

4.6...) The maximum value OB and minimum value C)B of the wave are held by the high signal selector 56 and the low signal selector 58, and the first
(3,5,...) wave amplitude H^, second (4,6°・)
The amplitude Ha of the wave is calculated by the calculator 59.63, the value is held in the memory 60.64, and the increase in amplitude from the first wave to the second wave is continuously monitored by the deviation monitor 61. If it is above the range, it is determined that there is an abnormal and divergent hunting state, and an abnormal output 89 is output. The increase in the amplitude from the second wave to the third wave is achieved by calculating the amplitude Hc of the third wave by using a circuit that calculates the peak value of the first wave in the first step and storing it in the memory 60. , the increase in the amplitude is similarly continuously monitored by the deviation monitor 62.

As described above, it is possible to continuously monitor the increase in amplitude from the third wave to the fourth wave, etc. in the same way.

As a result, as shown in FIG. 7, the water supply flow rate 20 suddenly changes from the time To when the recirculation valve is closed and continues to hunt while diverging. At the timing of , the boiler's dry firing protection flow rate becomes lower than the unit trip, and the unit trips, but
If the abnormality diagnosis circuit 19 of the present invention is provided, at timing T2, when the increase in amplitude from the first wave to the second wave exceeds the normal value, an early abnormality is output, an alarm is issued, and the control system Since the unit is evacuated from the automatic return control mode to a safe direction such as manual mode, unit trip can be prevented.

The above example is an explanation of the case of an automatic water pump switching device, but as stated in the key claim of the present invention, it is possible to diagnose loop abnormalities early from the increase in amplitude for the loop return control system in general. You can do it and have the same effect.

〔Effect of the invention〕

According to the present invention, since a divergent hunting state when a disturbance is applied to the return control system can be diagnosed at an early stage, there is an effect that the control system can be evacuated in a safe direction at an early stage.

Furthermore, when applied to an automatic water pump switching device, it is possible to detect an abnormality early and move the control system from the automatic return control mode to a safe direction such as manual mode, thereby preventing unit tripping.

[Brief explanation of drawings]

Fig. 1 is a logic diagram of the abnormality diagnosis circuit of the present invention, Fig. 2 is a block diagram of the steam system and feed water pump automatic switching device of a thermal power plant, Fig. 3 is a detailed block diagram of the water pump switching of the present invention, and Fig. 4 The figure shows water supply switching, Figure 5 shows the water supply flow rate fluctuation when the recirculation valve is normally closed, Figure 6 shows the water supply flow rate fluctuation when the recirculation valve is closed in an abnormal situation, and Figure 7 FIG. 2 is a diagram illustrating fluctuations in the water supply flow rate when the recirculation valve is closed during an abnormality according to the present invention. 19... Abnormality diagnosis circuit, 20... Water supply flow rate, 52...
...High signal selector, 54...Low signal selector, 89...
・Abnormal occurrence chart No. 3 No. 4 next door diagram

Claims (1)

[Claims] 1. Abnormality diagnostic control in a loop return control system, characterized in that a divergent hunting state of the control system due to loop disturbance is detected by an increase in the hunting amplitude of a loop return signal, and an abnormality is output. Device. 2. A motor-driven water supply pump A and a turbine-driven water supply pump for supplying condensate to the steam generator, and a control device that adjusts the water supply flow rate based on the flow rate supply request value on the steam generator side and the water supply pump discharge flow rate. A boiler feed water control device comprising the abnormality diagnosis control device according to claim 1.