JPH09317690A - Controller for compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the surging of a compressor by arranging a rotational speed limiter to output a second opening signal by which the opening of a regulating valve is controlled to be enlarged when a rotational speed is high and contracted when the rotational speed is low according to a signal from a rotational speed detector when a changing speed exceeds a threshold value in a rate-of-change limiter. SOLUTION: In case that an output signal from a comparator 24, received in a rate-of-change limiter 25, is a fully opening command signal, an output signal corresponding to the rotational speed of a compressor 1 is calculated by a rotational speed limiter 25a, and this output signal is outputted as a second opening signal for controlling the opening of a regulating valve 6, to a maximum value selector 26. In the maximum value selector 26, any larger value out of a first opening signal from a controller 13 and the second opening signal from the rate-of-change limiter 25, is selected and outputted to the regulating valve 6, so that a valve opening is operated. Hereby, influence exerted on the wake side of the compressor 1 is diminished, and the compressor can be returned immediately to a normal operation by loose flow control from a normal operational condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressor control device applied to a centrifugal compressor for gas pressurization in a chemical plant such as a gas pipeline or an ammonia plant.

[0002]

2. Description of the Related Art FIG. 6 is an explanatory diagram showing the overall configuration of a conventional compressor control device.

As shown in FIG. 1, the compressor 1 is driven by a driving device 2 such as a gas turbine or a steam turbine that rotates at a high speed. During operation of the compressor 1, the gas to be compressed enters the compressor 1 through the pipe 3 and the suction drum 5, and is compressed there. Then, the gas leaving the compressor 1 is pipe 4
It goes through to the downstream process.

Further, a part of the gas discharged from the outlet of the compressor 1 enters the suction drum 5 through the pipe 7 and a control valve 6 provided in the middle of the pipe 7 so that it can be circulated to the compressor 1 again. It has become.

The flow rate detector 10 and the rotation speed detector 12 are
The inflow flow rate Q into the compressor 1 and the rotation speed N are respectively detected, and each outputs a detection signal to the divider 21.

The divider 21 calculates the ratio between the rotation speed N of the compressor 1 detected by the rotation speed detector 12 and the inflow flow rate Q into the compressor 1 detected by the flow rate detector 10, and calculates the ratio. The result is a controller 13, a changing speed calculator 22 and a function generator 23.
Output to

The controller 13 receives the output signal from the divider 21 and controls the opening of the control valve 6 so that the ratio (Q / N) of the inflow flow rate Q and the rotational speed N approaches the set value. And outputs the first opening signal to the maximum value selector 26.

The change speed calculator 22 receives the output signal from the divider 21 and receives the ratio (Q
/ N) change speed is calculated, and this change speed is calculated by the comparator 24.
Output to

The function generator 23 receives the output signal from the divider 21 and receives the ratio (Q / Q) between the inflow rate Q and the rotation speed N.
Based on N), a threshold value for the changing speed of Q / N is calculated, and this threshold value is output to the comparator 24. This threshold becomes larger as Q / N becomes larger than the surging point, and conversely becomes smaller as Q / N becomes smaller.

In the comparator 24, the change speed calculator 22 and
Output signal x of the function generator 23₁, X _Two, That is, the change of Q / N
Input the conversion speed and its threshold value and compare both
The control valve 6 fully open command signal (y = 1) or fully closed
The command signal (y = 0) is output to the change rate limiter 25.

The change rate limiter 25 inputs the output signal y = 1 or y = 0 from the comparator 24, and based on this value, outputs a second opening signal for controlling the opening of the control valve 6. Is calculated and the second opening signal is output to the maximum value selector 26. That is, the output signal from the comparator 24 is 1 (y = 1)
When, the output signal z of the change rate limiter 25 instantly becomes 1 (z = 1), and the output signal from the comparator 24 becomes 0.
When (y = 0), the output signal z of the change rate limiter 25 is calculated so as to gradually approach 0 from the previous value.

In the maximum value selector 26, the first opening signal from the controller 13 and the second opening signal from the change rate limiter 25 are input, and the larger one of them is selected. Select and output to the control valve 6.

The control valve 6 receives the output signal of the maximum value selector 26, and the valve opening is operated by this output signal.

[0014]

Therefore, in the above conventional compressor control device, in order to avoid the surging of the compressor 1 when the operating state of the compressor 1 rapidly changes in the direction of the surging region. The control valve 6 is controlled so that the opening degree of the control valve 6 is quickly and fully opened. However, due to the quick and full opening of the control valve 6, a large amount of gas flows from the discharge side to the suction side of the compressor 1 and the gas to the wake side process The flow rate of is rapidly reduced.
At this time, if the rotation speed of the compressor 1 is in a low rotation speed region, the influence on the wake side process is small, but when the rotation speed of the compressor 1 becomes high, this rapid flow rate reduction gives the wake side process. It had a big impact and became a problem.

Further, at the same time that the influence on the wake-side process becomes large, the operation shifts from the normal operation state to an excessively large flow rate side, which causes a problem that the recovery to the normal operation is delayed. .

Therefore, in view of the above-mentioned prior art, the present invention makes it possible to avoid the surging of the compressor when the operating state of the compressor rapidly changes in the surging region, and the rotation speed of the compressor is high. It is an object of the present invention to provide a control device for a compressor, which has a small effect on the downstream process of the compressor even in a case, and can quickly return to normal operation.

[0017]

A compressor control apparatus according to the present invention, which solves the above problems, detects a flow rate detector for detecting an inflow flow rate of a compressor for boosting gas and a rotational speed of the compressor. A rotation speed detector, a divider that inputs the output signal of the flow rate detector and the output signal of the rotation speed detector, and calculates the ratio between the inflow flow rate and the rotation speed, and the output signal of this divider. The controller outputs a first opening signal for controlling the output signal to approach the set value, and the output signal of the divider is input to change the rate of change of the ratio of the inflow flow rate to the rotation speed. A change speed calculator for calculating, a function generator for inputting an output signal of the divider to calculate a threshold value for the change speed, an output signal of the change speed calculator and an output signal of the function generator. Input and compare the rate of change with the threshold value And an output signal representing the comparison result of this comparator is input, and when the changing speed exceeds the threshold value in accordance with the comparison result, the opening degree of the control valve is rapidly increased and then the changing speed is set to the above-mentioned value. A rate-of-change limiter that outputs a second opening signal for controlling the opening of the control valve to gradually decrease when it falls below a threshold value, and the first opening signal and the second opening signal. And a maximum value selector for selecting and outputting the larger one of these values, and a control valve installed at the inlet of the compressor and operated by the output signal of the maximum value selector. A control device for a compressor, wherein, in the change rate limiter, when the change speed exceeds the threshold value, in response to an output signal from the rotation speed detector, when the rotation speed is low, Increase the opening of the control valve to rotate Characterized in that is provided with a rotational speed limiter for outputting a second opening signal to control so as to reduce the opening to open from the closed of the control valve as higher.

Therefore, according to the compressor control device having the above structure, when the flow rate into the compressor is rapidly reduced and the outlet pressure of the compressor is rapidly increased, the compressor operated by the divider is calculated. The ratio of the inflow flow rate to the number of revolutions of A changes rapidly. At this time, if the rate of change of the ratio of the inflow rate to the number of revolutions calculated by the change rate calculator exceeds the threshold calculated by the function generator, the opening signal from the comparator to the control valve changes It is output to the limiter. When this output signal is a full-open command signal, the rotation speed limiter increases the opening of the control valve when the rotation speed of the compressor is low, and as the rotation speed increases, the control valve is closed to open. A second opening signal for controlling to reduce the opening is output. On the other hand, the control valve outputs a first opening signal to the control valve based on the ratio of the inflow flow rate to the rotational speed and the set value thereof.

Next, in the maximum value selector, the second opening signal output from the change rate limiter is compared with the first opening signal output from the controller, and the first opening signal having the larger value is compared. Two
The opening signal of is selected and output. Therefore, the control valve opens to the opening corresponding to the rotation speed by the second opening signal, and the inflow flow rate increases. Thus, the rise of the compressor outlet pressure is suppressed before the operating state of the compressor reaches the surging region.

After that, as the second opening signal output from the change rate limiter gradually decreases, the opening of the control valve also gradually decreases, but the value of the second opening signal is When the value becomes smaller than the value of the first opening signal output from the controller, the maximum value selector starts to output this first opening signal. The opening is controlled by the first opening signal from the controller.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. The same parts as those in the related art (FIG. 6) are designated by the same reference numerals, and overlapping detailed description will be omitted.

<Structure> FIG. 1 is an explanatory view showing the overall structure of a compressor control device according to an embodiment of the present invention, and FIG. 2 shows the relationship between the rotational speed of the compressor and the valve opening of a control valve. FIG.

As shown in FIG. 1, the compressor control device according to the present embodiment includes a flow rate detector 10 and a rotation speed detector 1.
2, a divider 21, a controller 13, a change speed calculator 22, a function generator 23, a comparator 24, a change rate limiter 25, a rotation speed limiter 25a, a maximum value selector 26, and a control valve 6.

The flow rate detector 10 and the rotation speed detector 12 are
The inflow flow rate Q and the rotational speed N of the compressor 1 are respectively detected, and both outputs a detection signal to the divider 21. The divider 21 calculates the ratio (Q / N) of the inflow flow rate Q and the rotation speed N, and the change speed calculator 22 calculates the ratio (Q / N) of the inflow flow rate Q and the rotation speed N.
N) change speed is calculated, and the function generator 23 calculates a threshold value for the Q / N change speed. In the comparator 24, the output signals x _{1 of} the change speed calculator 22 and the function generator 23,
x _2, i.e. by comparing the rate of change of Q / N and its threshold value, outputs a full open command signal for the control valve 6 (y = 1) or fully closing command signal (y = 0) to the velocity limiter 25 To do.

When the signal received by the rate-of-change limiter 25 is the full-open command signal (y = 1), the rotation speed limiter 25a calculates the output signal z corresponding to the rotation speed of the compressor 1 and outputs it. It is output to the maximum value selector 26 as a second opening signal for controlling the opening of the control valve 6. That is, as shown in FIG. 2, when the rotation speed of the compressor 1 is low, the opening degree of the control valve is increased, and as the rotation speed is increased, the opening degree of the control valve 6 from closed to open is decreased. And outputs a second opening signal for controlling. Also, the comparator 2
When the output signal from 4 is the fully closed command signal (y = 0), the output signal z from the change rate limiter 25 is calculated so as to gradually approach 0 from the previous value.

In the maximum value selector 26, the larger one of the output signal from the controller 13 (first opening signal) and the output signal from the change rate limiter 25 (second opening signal) is selected. The control valve 6 is selected and output to the control valve 6, and the valve opening of the control valve 6 is operated based on the output signal from the maximum value selector 26.

<Operation / Effect> With reference to FIGS. 3, 4 and 5, the operation / effect of the control device of the present compressor when the operating state of the compressor 1 changes rapidly in the surging region will be described. . It should be noted that FIG. 3 shows the passage of time and the state quantity (pressure,
Flow rate, etc.), FIG. 4 is an explanatory view showing the characteristic curve of the compressor and the locus of the operating state from the relationship between the flow rate and the boost ratio, and FIG. 5 is the relationship between Q / N and head / N ^2. It is explanatory drawing which shows the characteristic curve of a compressor and the locus | trajectory of an operating state.

As shown in these figures, up to point A, the compressor 1 is in a normal operating state, and its inlet pressure P _s , outlet pressure P _d , inflow flow rate Q and rotational speed N are in a rated state. . At this time, the opening degree of the control valve 6 is determined by the inflow flow rate Q and the rotation speed N.
Since the ratio (Q / N) with is larger than the set value, it is fully closed.

At this point A, for example, when the process downstream of the compressor 1 is stopped and the inflow flow rate Q is rapidly reduced, but the rotation speed of the compressor 1 is constant, the compression is performed. The outlet pressure P _d of the machine 1 rises rapidly.

As described above, when the inflow flow rate Q rapidly decreases from the point A, the outlet pressure P _d rapidly rises from the point A, and then at the point B, the inflow flow rate Q rapidly decreases. The ratio (Q / N) between the inflow flow rate Q and the rotation speed N rapidly decreases and the rate of change thereof increases.

Further, as the Q / N decreases, the output signal (threshold value) of the function generator 23 also decreases, and finally the rate of change of Q / N becomes larger than the output signal (threshold value) of the function generator 23. Then, the comparator 24 outputs 1 (y = 1, full open command signal).

The rate-of-change limiter 25 receives the full-open command signal (y = 1) from the comparator 24, and the rotational speed limiter 25a calculates an output signal z corresponding to the rotational speed of the compressor 1. The maximum value selector 2 as the second opening signal z for controlling the opening of the control valve 6.
Output to 6.

At this time, since the second opening signal z is larger than the first opening signal (the value at this time is 0) output from the controller 13, the maximum value selector 26 Second
The opening signal z is selected and is output to the control valve 6. As a result, the control valve 6 is operated by the second opening signal z to a valve opening degree according to the rotation speed.

At the point C, the inflow flow rate Q is further reduced due to the initial operation delay of the control valve 6, and the Q / N becomes smaller than the set value. Therefore, the Q / N is adjusted to the set value. The first opening signal is output from the total 13.

Then, as the control valve 6 opens, the inflow flow is increased.
The quantity Q begins to increase rapidly and the outlet pressure P _dAlso drops rapidly.
As a result, the rate of change of Q / N is reversed in the negative direction. This
When the rate of change of is smaller than the threshold value, comparison
0 (y = 0, fully closed command signal) is output from the device 24.
Is the second opening signal output from the rate-of-change limiter 25.
z is calculated so that it gradually approaches 0 from the previous value.
You.

At point D, the control valve 6 follows the second opening signal and gradually closes. Along with this, the inflow flow rate Q gradually decreases, Q / N gradually decreases, and the outlet pressure P _d of the compressor 1 gradually increases.

At point E, Q / N becomes smaller than the set value again, and the controller 13 outputs the first opening signal to set the Q / N to the set value. When the first opening signal becomes larger than the second opening signal, the maximum value selector 26 selects the first opening signal and outputs it to the control valve 6. Therefore, the opening degree of the control valve 6 after this is
It is controlled by the controller 13.

Incidentally, in FIG. 3, the alternate long and short dash line indicates the high rotation N
₁ , the two-dot chain line indicates the low rotation N ₂ , and the control valve opening signal indicates that the low rotation N ₂ is larger than the high rotation N ₁ .

As described above, according to the compressor control device of the present embodiment, when the fully open command signal to the control valve 6 is issued, the control valve opening degree is changed according to the rotation speed of the compressor 1. The influence on the downstream side process of the compressor 1 can be reduced by controlling the. Further, in this way, the influence on the wake side process is reduced, and since the flow rate control is gradually changed from the normal operation state, it is possible to quickly return to the normal operation.

[0040]

As described above in detail with the embodiments of the present invention, according to the compressor control device of the present invention, the change rate limiter changes the ratio of the inflow rate of the compressor to the rotational speed. When the speed exceeds the threshold value, corresponding to the output signal from the rotation speed detector, if the rotation speed of the compressor is low, the opening of the control valve is increased and the rotation speed of the compressor is increased. A rotation speed limiter that outputs a second opening signal for controlling the opening degree of the control valve to decrease from the closed state to the open state is provided, and the control valve opening degree is changed according to the rotation number of the compressor. By performing the control, it is possible to reduce the influence on the downstream side process of the compressor. Further, in this way, the influence on the wake side process is reduced, and since the flow rate control is gradually changed from the normal operation state, it is possible to quickly return to the normal operation.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a control device for a compressor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a rotation speed of a compressor and a valve opening degree of a control valve.

FIG. 3 is an explanatory diagram showing elapsed time and state quantities (pressure, flow rate, etc.).

FIG. 4 is an explanatory diagram showing a characteristic curve of a compressor and a locus of an operating state from a relationship between a flow rate and a boost ratio.

FIG. 5 is an explanatory diagram showing a characteristic curve of a compressor and a locus of an operating state based on a relationship between Q / N and head / N ² .

FIG. 6 is an explanatory diagram showing an overall configuration of a conventional compressor control device.

[Explanation of symbols]

 1 Compressor 2 Driver 6 Control valve 10 Flow rate detector 12 Rotation speed detector 13 Controller 21 Divider 22 Change speed calculator 23 Function generator 24 Comparator 25 Change rate limiter 25a Rotation speed limiter 26 Maximum value selector

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuhiro Taketa 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries Ltd. Hiroshima Works

Claims (1)

[Claims] 1. A flow rate detector for detecting an inflow rate of a compressor for boosting gas, a rotation speed detector for detecting a rotation speed of the compressor, an output signal of the flow rate detector, and the rotation speed detector. And a first opener for controlling the output signal of the divider so that the output signal approaches the set value. Degree controller, a change speed calculator that inputs the output signal of the divider and calculates the change speed of the ratio of the inflow flow rate to the rotation speed, and the change signal that receives the output signal of the divider. A function generator for calculating a threshold value for speed, a comparator for inputting an output signal of the change speed calculator and an output signal of the function generator and comparing the change speed with a threshold value, and this comparator Input the output signal that represents the comparison result of Accordingly, when the rate of change exceeds the threshold value, the opening degree of the control valve is rapidly increased, and when the rate of change falls below the threshold value, the opening degree of the control valve is gradually decreased. Change rate limiter for outputting a second opening degree signal for inputting the first opening degree signal and the second opening degree signal, and selecting either one of the larger values to output the maximum value. A controller of a compressor provided with a value selector and a control valve installed at the inlet of the compressor and operated by an output signal of the maximum value selector, wherein the change rate limiter, the change speed is When it exceeds the threshold value, in response to the output signal from the rotation speed detector, when the rotation speed is low, the opening degree of the control valve is increased, and as the rotation speed increases, the adjustment is performed. The opening from closing to opening of the valve should be reduced. A control device for a compressor provided with a rotation speed limiter for outputting a second opening signal for controlling