JPH06146806A - Opening controller for electro-hydraulic control valve - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if the opening / closing speed characteristics of the electro-hydraulic converter of the mechanical system or the control valve changes, the automatic opening / closing speed is limited to the maximum opening / closing speed of the control valve provided in the electric circuit. The purpose is to eliminate the above inconvenience. [Configuration] A change rate deviation signal between the actual change rate signal from the change rate detector that detects the change rate of the actual valve opening signal and the set signal of the speed limit setter that limits the opening or closing direction speed of the valve Obtain this value and set it as the speed limit value for opening or closing the valve through a coefficient multiplier that multiplies this change rate deviation signal by a coefficient, and use this speed limit value for the signal limiter that limits the deviation signal between the opening command signal and the actual valve opening signal. As a set value, the opening or closing speed of the valve is limited by limiting the signal to the electro-hydraulic converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrohydraulic control valve opening control device for controlling the flow rate of steam or gas flowing into a turbine in a power generation or heat cycle plant equipped with a steam turbine or a gas turbine. .

[0002]

2. Description of the Related Art The flow rate of steam or gas flowing into a turbine is controlled by adjusting the opening of a control valve provided on the upstream side of the turbine. Since this control valve requires a large driving torque and a continuous smooth opening / closing operation, it is generally controlled to be opened / closed by hydraulic pressure. Further, in order to facilitate the electrical interface with the automatic control device, a method of providing an electro-hydraulic converter and converting an electric signal into a hydraulic signal to control the opening of the control valve is adopted.

FIG. 2 shows a conventional valve opening control device. In the figure, the opening degree command signal V1 and the actual valve opening degree signal V2 are input to the adder 1, and the deviation between them is input to the coefficient unit 2 and multiplied by the coefficient to become the signal V3. This signal V3 is input to the signal limiter 3, and the set value V4H of the open speed limit setter 4 that sets the maximum value of the valve open speed and the close speed limit setter 5 that sets the maximum value of the valve closed speed. The signal is limited by the set value V4L of the above and becomes the signal V4. This signal V4 is converted from an electric signal to a hydraulic signal P1 in the electro-hydraulic converter 6, and the opening of the control valve 7 is controlled by this hydraulic signal. The opening degree P2 of the control valve 7 is converted by the valve opening degree detector 8 into an actual valve opening degree signal V2 proportional to the opening degree and fed back to the adder 1 to perform closed loop control of the valve opening degree.

The electro-hydraulic converter 6 and the control valve 7 described above are expressed in an electrical diagram as shown in FIG. That is, the electric signal V4 is added with the signal V4B from the bias setter 6-2 in the adder 6-1 and is input to the integrator 7-2 through the signal limiter 7-1 and integrated to be the actual valve opening signal. It becomes V2.

The signal V4B of the bias setter 6-2 is a mechanical bias, and the signal V4 becomes zero due to a failure of the automatic control device or disconnection of the electric signal wiring, and the valve opening control is open loop. It is provided in order to change the control valve 7 to the fully open direction or the fully closed direction to bring the control system to a safe direction. Further, the control valve 7 is an integral system, and changes in the opening or closing direction depending on the polarity of the electric signal, and the opening / closing speed of the control valve 7 is determined by the magnitude of the electric signal. It doesn't get faster than the limited speed.

The maximum opening / closing speed for automatic control of the control valve 7 is set by the signal limiter 3 shown in FIG.
Generally, the speed is set to be smaller (slower) than that of the signal limiter 7-1 on the machine side. For example, in the steam control valve of the steam turbine, the following settings are made. That is,
In the rapid opening operation of the steam control valve, the control oil pressure for driving the control valve is rapidly supplied, so the oil pressure drops at this time and other control valves using the same control oil are closed. The opening speed is limited for the purpose of preventing the accident. In addition, the valve closing direction, which is the safe direction of turbine rotor control,
In order to set the maximum speed of the mechanical system, it is general to set the closing speed limit setting to be missing, but it is also necessary to set the limit when the speed of the mechanical system is extremely high.

[0007]

Since the bias setting device 6-2 shown in FIG. 3 is a mechanical bias, it changes with time or with temperature or the like, and the integrator 7 has a slight amount. The integration time constant of -2 also changes.

When such a change occurs, a deviation occurs between the limit setting of the opening or closing speed set by the signal limiter 3 of FIG. 2 and the actual maximum opening and closing speed, and the automatic Control inconvenience occurs. In particular, in the case of a steam control valve of a steam turbine, if the speed characteristics of the mechanical system deviate so as to increase in the opening direction, the control valve is driven by a rapid opening operation, and the control oil pressure drops. Other control valves may be closed, or the speed of the control valve in the closing direction may become slower, which causes inconvenience in control. Further, if the speed characteristics of the mechanical system deviate so as to become faster in the closing direction, the opening speed of the control valve becomes slower, which causes inconvenience in control. Therefore, it is necessary to perform regular inspections and readjust the bias setting device 6-2 or the open speed limit setting device 4 and the closing speed limit setting device 5.

Further, in order to prevent the influence of the characteristic deviation of the control valve opening / closing speed of the mechanical system, the use of the signal limiter 3 in FIG. 2 is stopped, and instead, the opening command is issued as shown in FIG. A change rate limiter 9 is provided in the middle of the line of the signal V1,
There is also a method of limiting the maximum change rate of the opening command signal V1.
However, according to this method, even if the rate of change from the opening command side can be limited, in the situation where the valve opening detector 8 fails and the actual valve opening signal suddenly changes, the maximum opening / closing speed of the control valve You can no longer limit.

The present invention has been made to solve the above-mentioned problems of the prior art. Even when the opening / closing speed characteristics of the electrohydraulic converter of the mechanical system or the control valve changes, the control valve provided in the electric circuit is changed. The object of the present invention is to eliminate the inconvenience in automatic control by limiting the maximum opening / closing speed.

[0011]

SUMMARY OF THE INVENTION An opening control device for an electrohydraulic control valve according to the present invention provides an actual change rate signal from a change rate detector for detecting a change rate of an actual valve opening signal, and an opening of the valve. Or, obtain the change rate deviation signal from the setting signal of the speed limit setter that limits the speed in the closing direction, and set it as the speed limit value for opening or closing the valve through the coefficient multiplier that multiplies this change rate deviation signal by the coefficient. Is a set value of a signal limiter that limits the deviation signal between the opening command signal and the actual valve opening signal, and limits the opening or closing speed of the valve by limiting the signal to the electro-hydraulic converter. To do.

[0012]

In the device of the present invention having such a configuration, when the actual change rate of the actual valve opening signal is slower than the set maximum opening / closing speed of the valve, the signal limit value to the electro-hydraulic converter is large, so It changes according to the opening / closing speed characteristics of the system, but when the actual rate of change approaches the set maximum opening / closing speed of the valve, the signal limit value for the electro-hydraulic converter becomes small and the signal does not exceed the maximum opening / closing speed. Is output.

[0013]

EXAMPLES Next, examples of the present invention will be described. FIG. 1 shows an embodiment of an electro-hydraulic control valve opening control device according to the present invention, and the inside of the frame of the broken line in the figure is a characteristic part of the present invention.
The same parts or signals as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, the actual valve opening signal V2 is also input to the change rate detector 10, and signals V5, V proportional to the change rate are inputted.
Outputs 9. Signal V5 is the actual change rate signal in the valve opening direction,
It is zero in the valve closing direction. The signal V9 is an actual change rate signal in the valve closing direction, which is zero in the valve opening direction.

The actual change rate signal V5 in the valve opening direction is calculated by the adder 1
In 1, the value is compared with the set value V6 of the opening speed limit setter 12 which sets the maximum opening speed of the valve, and the deviation therebetween becomes the change rate deviation signal V7 in the valve opening direction. This signal is input to the coefficient unit 13 and multiplied by the coefficient, and is input to the signal limiter 3 as the valve opening direction signal limit setting value V8, and the signal maximum value limit in the valve opening direction is set. Further, the actual change rate signal V9 in the valve closing direction is compared and calculated in the adder 14 with the set value V10 of the closing speed limit setter 15 which sets the maximum closing speed of the valve.
These deviations become the change rate deviation signal V11 in the valve closing direction.
This signal is input to the coefficient multiplier 16 and multiplied by the coefficient,
The signal limiter 3 is inputted as the valve closing direction signal limit set value V12, and the signal maximum value limit in the valve closing direction is set.

In the embodiment of the apparatus of the present invention configured as described above, when the actual valve opening signal V2 is constant and does not change, the actual change rate signal V5 in the valve opening direction and the actual change rate in the valve closing direction. The signals V9 are both zero. Therefore, the change rate deviation signal V7 in the valve opening direction becomes equal to the opening speed limit setting value V6, and a signal obtained by multiplying this by the coefficient becomes the valve opening direction signal limit setting value V8. Similarly, the change rate deviation signal V11 in the valve closing direction becomes equal to the closing speed limit setting value V10, and a signal obtained by multiplying this by the coefficient becomes the valve closing direction signal limit setting value V12. The coefficient settings of the coefficient units 13 and 16 are set so that the limit value of the signal limiter 3 becomes larger than the V4 value corresponding to the maximum opening speed or closing speed of the valve when the actual valve opening is constant. It is numerically set so that the V4 value is not limited when the valve begins to move and the speed limit is set to a relatively large coefficient value in order to be as close as possible to the speed limit set value.

When the opening command signal V1 changes in the opening direction,
The opening deviation signal V3 is output in the opening direction. At this time,
Since the signal limit set value V8 by the signal limiter 3 is a large value, the signal V4 = V3 is input to the electrohydraulic converter 6 without limiting the signal, and the control valve 7 changes to the opening direction. . Accordingly, when the actual valve opening signal V2 changes in the opening direction, the actual change rate signal V5 of the change rate detector 10 in the valve opening direction outputs a signal proportional to the change rate. When the actual rate of change at this time is slower than the opening speed limit setting value V6, the valve opening direction signal limit setting value V8 outputs a large value, and the signal limiter 3 does not limit the signal, and the valve opening degree changes. It changes at the same speed.

When the actual change rate signal V5 at this time approaches the opening speed limit set value V6 as much as possible, the valve opening direction signal limit set value V8 gradually decreases and the signal limiter 3 limits the signal. That is, the opening speed of the control valve 7 is limited. Here, if the actual change rate signal V5 = opening speed limit set value V6, the valve opening direction signal limit set value V8 =
In the state of 0, the output of the signal limiter 3 becomes V4 = 0, and the opening direction of the control valve 7 is not changed. In that case, at the same time, the actual change rate signal V5 = 0.
Therefore, the signal limiter 3 does not limit the signal, so that the control valve 7 changes to the opening direction again. Since these operations are instantaneously performed, as a result, the opening direction speed of the control valve 7 does not exceed the opening speed limit set value V6. In the above description, the opening direction operation of the control valve 7 has been described, but the closing direction also corresponds to each operation, and thus the description thereof is omitted.

As described above, in the embodiment of the present invention, the actual change rate of the actual valve opening signal of the control valve is detected, and the deviation value between this change rate and the maximum opening / closing speed setting value of the valve is used to determine the electric value. Since the control signal input to the hydraulic pressure converter is limited, it is possible to control the control valve so that it does not exceed the predetermined maximum opening / closing speed even if the mechanical system valve opening / closing speed characteristic changes with respect to the electrical signal. it can. The present invention can be modified and implemented as follows.

That is, in the embodiment shown in FIG. 1, the present invention is applied to the conventional example shown in FIG. 2, but as shown in FIG.
It is also possible to add the circuit of the present invention to the conventional example in which the change rate limiter 9 is provided in the opening command value line.

Further, a signal limiter (not shown) is provided on the output side of the coefficient multipliers 13 and 16 of the embodiment shown in FIG. 1 to limit the maximum value of each signal, thereby opening and closing the speed limit setting signal more than necessary. Alternatively, even when the opening degree deviation signal V3 becomes a large value for the first time, the control valve opening / closing speed can be limited to a desired value.

[0022]

As described above, according to the opening control device of the electrohydraulic control valve of the present invention, even if the opening / closing speed characteristic of the electrohydraulic converter of the mechanical system or the control valve changes, the control valve It is possible to limit the maximum opening / closing speed within a desired range, and it is possible to eliminate inconvenience in automatic control. This allows
Especially in the case of a steam control valve of a steam turbine, the maximum opening speed limit value will not exceed the maximum opening speed limit even if the speed characteristics of the mechanical system deviate in the opening direction. It is possible to reduce the control oil pressure for driving and prevent other control valves using the same control oil from closing. Further, it is possible to prevent the control valve from being slowed in the closing direction and causing inconvenience in control. Further, it becomes possible to lengthen the cycle of readjustment of the bias setting of the mechanical system or readjustment of the opening / closing speed limit setting of the electric circuit, which brings merit in maintenance.

[Brief description of drawings]

FIG. 1 is a control block diagram showing an embodiment of the present invention.

FIG. 2 is a control block diagram illustrating a conventional valve opening control device.

3 is an electrical block diagram of an electrohydraulic converter and a control valve of a mechanical system in the valve opening control device of FIG.

FIG. 4 is a control block diagram showing another example of a conventional valve opening control device.

[Explanation of symbols]

 1, 11, 14 ... Adder 2, 13, 16 ... Coefficient unit 3, 6-1 ... Signal limiter 4, 12 ... Open speed limit setter 5, 15 ... Closed speed limit setter 6 ... Electro-hydraulic conversion Device 6-2 …… Bias setting device 7 ………… Control valve 7-2 …… Integrator 8 ………… Valve opening detector 9 ………… Change rate limiter 10 ………… Change rate detector.

Claims (1)

[Claims] 1. A structure in which a deviation signal between an opening command signal and an actual valve opening signal is input to an electro-hydraulic converter to convert the electric signal into a hydraulic signal to control the opening of a control valve by hydraulic pressure. In the valve opening control device, a change rate detector that detects the change rate of the actual valve opening signal, and an open speed limit setter that limits the actual change rate signal from this change rate detector and the valve opening direction speed are set. A first deviation circuit that obtains a change rate deviation signal from the setting signal;
Through a second deviation circuit for obtaining a change rate deviation signal between the actual change rate signal and the setting signal of the opening speed limit setter for limiting the closing direction speed of the valve, and a coefficient multiplier for multiplying these change rate deviation signals by a coefficient. By setting the speed limit value for opening or closing the valve as a set value that limits the deviation signal between the opening command signal and the actual valve opening signal, and limiting the signal to the electro-hydraulic converter, And a signal limiter for limiting the opening or closing speed of the electro-hydraulic control valve.