JPH04203402A - Process control device - Google Patents

Abstract

PURPOSE:To prevent hunting of a process system and breakage of an apparatus by providing a lower limit restricting means by which the lower limit value of a process signal detected by a process amount detecting means is restricted to a prescribed value so as to give it to a calculating means. CONSTITUTION:The rotational speed of a turbine 1 is detected by a rotational speed detector 4, and the rotational speed signal thereof is inputted step to a lower limit restrictor 8. When the rotational speed signal detected by the rotational speed detector 4 exceeds the restricted value of the lower limit restrictor 8, output of the rotational speed detector 4 is inputted into a calculating circuit 6 from the lower limit restrictor 8. Hence, a flow amount regulation value 3 is operated according to the deviation signal between a rotational speed demand signal and the rotational speed signal which are found out by the calculating circuit 6 in a value opening control circuit 7, and the amount of steam or gas which are supplied into a turbine 1 is controlled until the rotational speed signal of the burbine 1 matches the rotational speed demand signal finally. It is thus possible to prevent hunting of a process system and breakage of an apparatus.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a process that prevents damage to equipment due to sudden fluctuations at the start of control of a process amount or at the start of operation of a process system. Regarding a control device.

(Prior Art) As a conventional process control device, there is a turbine control device as shown in FIG. 4, for example. As shown in the figure, this turbine control device has a power generation equipment that includes a turbine 1, a generator 2 directly connected to the turbine 1, and a flow ffi control valve 3 provided in a steam or gas supply system that drives the turbine 1. ing. Also, a rotation speed detector 4 that detects the rotation speed of the turbine 1, a rotation speed request circuit 5, a rotation speed request signal output from the rotation speed request circuit 5, and a rotation speed signal output from the rotation speed detector 39. and a valve opening control circuit 7 which receives a deviation signal between the rotational speed request signal and the rotational speed signal outputted from this calculation circuit 6 and operates the flow jl control valve 3 based on this deviation signal. The control system is configured by:

(Problem to be Solved by the Invention) In such a turbine control device, when the turbine 1 is operating at a constant rotation speed, a deviation signal between the rotation speed request signal and the rotation speed signal obtained by the arithmetic circuit 6 is generated. is input to the valve opening control circuit 7, the valve opening control circuit 7 operates the flow rate control valve 3 to control the flow rate of steam flowing into the turbine 1, so that the rotation speed of the turbine 1 is adjusted to the rotation speed request signal. controlled to match. However, when starting the turbine 1 to gradually increase the rotation speed from a stopped state, the rotation speed detector 4 cannot detect from zero rotation as shown in FIG. 5, and when the rotation of the turbine 1 increases to several tens of rotations. Since the detection is started from , the rotation speed signal is inputted in a stepwise manner, which causes the flow rate control valve 3 to hunt, and the rotation speed of the turbine 1 to also hunt.

The above is a case of a turbine control system, but in the case of a water supply flow rate control system, the signal of the flow rate detector starts to be detected in a step manner at the start of water supply flow rate control, so the water supply flow rate may be hunting, and in rare cases, hammering may occur. There was a problem that this could cause damage to the pump and piping.

SUMMARY OF THE INVENTION An object of the present invention is to provide a process control device with good responsiveness that can prevent process system hunting and equipment damage due to sudden fluctuations at the start of control of process quantities or at the start of operation of the process system.

L Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a process amount requesting means, a process amount detecting means for detecting a process in a process system, and the process amount requesting means. a calculation means for comparing and calculating a process amount request signal issued by the process amount request signal and a process signal detected by the process amount detection means; and a calculation means for operating the position of an operating device provided in the process system based on a deviation signal obtained by the calculation means. an actuator control means for controlling a process quantity by using a controller; provided between the process quantity detection means and the calculation means; and lower limit limiting means for applying a lower limit to the arithmetic means.

(Function) In a process control device having such a configuration, a step-like detection signal is output when the process amount detection means enters the signal detection range due to the start of control of the process amount or the start of operation of the process system. However, since the lower limit value of this detection signal is limited to a predetermined value by the lower limit value limiting means, it is possible to operate the operating device smoothly, thereby eliminating sudden fluctuations in the process amount and preventing damage to the equipment. It becomes possible to control the process to prevent this.

(Example) An embodiment of the present invention will be described below with reference to rotation.

FIG. 1 shows the configuration of a turbine control device, and the same parts as in FIG. 4 are shown with the same symbols. As shown in FIG. 1, the power generation equipment consists of a turbine 1, a generator 2 directly connected to the turbine 1, and a flow control valve 3 provided in the steam or gas supply system that drives the turbine 1. . The turbine control system also includes a rotation speed detector 4 that detects the rotation speed of the turbine 1;
A lower limit limiter 8 that limits the lower limit of the rotation speed signal by a preset limit value, a rotation speed request circuit 5, and a rotation speed output from the rotation speed request circuit 5. An arithmetic circuit 6 that compares and calculates the request signal and the rotational speed signal output from the lower limit limiter 8, and a deviation signal between the rotational speed request signal and the rotational speed signal output from this arithmetic circuit 6 are input, and this deviation signal is inputted. The valve opening control circuit 7 operates the flow rate regulating valve 3 by means of the following.

Next, the operation of the turbine control device configured as described above will be described with reference to the time chart shown in FIG.

Now, when the turbine 1 starts to start up, the rotation speed detector 4 cannot detect the turbine 1 from zero rotation to several tens of rotations, so its output signal is zero. Therefore, even if the output signal input from the rotation speed detector 4 to the lower limit limiter 8 is zero, the lower limit of the rotation speed signal is limited by the lower limit limiter 8. The output of the limit value is input as a rotation speed signal.

In this state, when the rotation speed request signal input from the rotation speed request circuit 5 to the arithmetic circuit 6 starts to gradually increase, the arithmetic circuit 6
Then, the rotation speed signal whose lower limit is limited and the rotation speed request signal are compared and calculated, and the deviation signal is input to the valve opening degree control circuit 7. When this deviation signal becomes larger than zero due to an increase in the rotation speed request signal, the flow control valve 3 begins to open by operating the valve opening degree control circuit 7, and steam or gas is supplied to the turbine 1. As a result, the turbine 1 rotates, and when its rotation speed begins to rise above several tens of rotations, the rotation speed detector 4 starts detecting the rotation speed of the turbine 1 at point A in the figure, and the rotation speed signal is The signal is input to the lower limit limiter 8 in a stepwise manner.

However, even if the rotation speed signal that changes stepwise is input to the lower limit limiter 8, the lower limit is limited, so the output of the lower limit limiter 8 does not change to point B in the figure, and the arithmetic circuit 8
The deviation signal input to the valve opening degree control circuit 7 changes in accordance with the increase in the rotation speed request signal. When the rotational speed signal detected by the rotational speed detector 4 exceeds the limit value of the lower limit limiter 8, the output of the rotational speed detector 4 is input from the lower limit limiter 8 to the arithmetic circuit 6. Therefore, the valve opening degree control circuit 7 operates the flow ffi control valve 3 according to the deviation signal between the rotation speed request signal and the rotation speed signal obtained by the calculation circuit 6 at this time, and finally the rotation speed of the turbine 1 is The amount of steam or gas supplied to the turbine 1 is controlled until the signal matches the rotational speed request signal.

In this way, in this embodiment, even if the rotation speed detector 4 cannot detect the rotation speed from zero to several tens of revolutions when the turbine 1 is started, the limit value preset in the lower limit limiter 8 is used as the rotation speed signal. When the rotational speed signal applied to the arithmetic circuit 6 and detected by the rotational speed detector 4 exceeds the limit value, the lower limit limiter 8 outputs jl'f according to the deviation signal from the rotational speed detection request signal.
Since the flow control valve 3 is operated by the sJ1 degree control circuit 7, hunting will not occur in the flow control valve 3 even if the rotation speed signal changes stepwise when the rotation speed detector 4 detects the rotation speed. Therefore, the rotation of the turbine 1 can be increased smoothly.

In the above embodiment, a turbine control device is used as the process control device, but the present invention can be similarly applied to a water supply control device that controls the discharge flow rate of a pump as shown in FIG. In FIG. 3, 11 is a water supply pump, 12 is a flow fflR control valve provided in the outflow system of the water outflowing from the water supply pump 11, and 13 is a flow rate detector for detecting the flow rate of the outflow system. Further, 14 is a lower limit limiter that limits the lower limit of the flow rate signal detected by the flow rate detector 13 to a preset limit value, 15 is a flow rate request circuit, and 16 is a flow rate request signal inputted from this flow rate request circuit 15. A calculation circuit 17 calculates the deviation by comparing and calculating the flow rate signal inputted from the lower limit limiter 14, and 17 is a calculation circuit that calculates the deviation between
This is a valve opening control circuit that controls the flow rate so that it matches the flow rate request signal.

In such a water supply control device, even if the flow rate value of the water supply system is too small to be detected by the flow rate detector 13 when the water supply pump 11 is started, the lower limit of the flow rate signal is limited by the limit value of the lower limit limiter 14. The flow rate at the beginning of water supply can be smoothly controlled, and the water supply flow rate does not hunt and damage the pump or piping due to hammering, which is the case with conventional systems.

In the embodiment shown in FIG. 1 and the embodiment shown in FIG. 3, the components of the control system were explained using a hardware configuration, but this control system can be implemented using software of a digital computer such as a microprocessor having an input/output device. may be configured.

Further, although the description has been made with reference to a turbine control device and a water supply control device as process control devices, it goes without saying that the present invention can be similarly applied to other process control devices.

[Effects of the Invention] As described above, the present invention provides responsiveness that can prevent hunting of the process system and damage to equipment due to sudden fluctuations at the start of control of process quantities or the start of operation of the process system. We can provide good process control equipment.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment in which the present invention is applied to a turbine control device, Fig. 2 is a diagram showing a time chart for explaining the operation of the embodiment, and Fig. 3 is a diagram showing the construction of an embodiment in which the present invention is applied to a turbine control device. FIG. 4 is a block diagram showing an example of application to a control device, FIG. 4 is a block diagram showing a conventional turbine control device, and FIG. 5 is a time chart for explaining the operation of the turbine control device. . 1... Turbine, 2... Generator, 3.
...Flow rate control valve, 4...Rotation speed detector,
5... Rotation speed request circuit, 6... Arithmetic circuit, 7... Valve opening control circuit, 8... Lower limit limiter, 11... ...Water pump, 12...
...Flow rate control valve, 13...Flow rate detector, 14.
... lower limit limiter, 15 ... flow rate request circuit, 16 ... calculation circuit, 17 ... valve opening degree control circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 4

Claims (1)

[Claims] A process amount requesting means, a process amount detecting means for detecting a process amount of a process system, and an operation for comparing a process amount request signal outputted from the process amount requesting means and a process signal detected by the process amount detecting means. means, an operating device control means for controlling a process quantity by operating an operating device provided in the process system using a deviation signal obtained by the computing means, and an operating device control means provided between the process quantity detecting means and the computing means. and lower limit limiting means for limiting the lower limit value of the process signal detected by the process amount detecting means to a predetermined value and applying it to the calculating means.