JPH0814279B2 - Centrifugal compressor control method - Google Patents

Description

The present invention relates to a centrifugal compressor such as a raw material air compressor used in an oxygen production plant or various plants, a compressor for a factory air source, a gas compressor for a chemical plant, etc. It relates to a method for controlling the capacity and pressure of the.

[Prior Art] Generally, a centrifugal compressor having a multi-stage structure is used in an oxygen production plant and various plants. In such a multi-stage centrifugal compressor, as shown in FIG. 7, the centrifugal compressor 1 is a first-stage compressor 4 driven by a power transmission gear 3 that accelerates the rotation from the drive unit 2. , Second
Stage compressor 5, 3rd stage compressor 6 and 4th stage compressor 7
And the intercooler 8 between the compressors 4 and 5,
An intercooler 9 is provided between the compressors 5 and 6, and an intercooler 10 is provided between the compressors 6 and 7. The compressors 4 and 5 and the compressors 6 and 7 are overhung at the same shaft end.

In such a centrifugal compressor 1, the air sucked into the compressor 4 of the first stage is sequentially compressed and cooled by each of the compressors 5-7 and the intercoolers 8-10 to obtain the fourth stage. The compressor 7 of the eye is sent to the process.

Then, angle-adjustable inlet guide vanes (GV) 11 to 14 are provided on the inlet side of the compressors 4 to 7 of the respective stages, and by adjusting the angles of these inlet guide vanes 11 to 14, The volume of air flowing into the compressors 4 to 7 can be adjusted. Diff user vanes (DV) 15 to 18 are provided on the outlet side of the compressors 4 to 7 at each stage. By adjusting the angles of these diff user vanes 15 to 18, The volume of air flowing out from each compressor 4 to 7 can be adjusted.

The angles of the inlet guide vanes 11 to 14 and the diff user vanes 15 to 18 are adjusted to arbitrary values by the drive device 19, respectively.

Furthermore, the operating states of the centrifugal compressor 1 as a whole or the compressors 4 to 7 at the respective stages, for example, operating state quantities such as air flow rate, temperature, pressure, etc., are respectively measured by the flow rate sensor 20, the temperature sensor 21,
It is detected by detection means such as the pressure sensor 22. A control device is provided between each of the sensors 20 to 22 and the drive device 19.
23 are provided.

When controlling the flow rate of the multi-stage centrifugal compressor as described above, in order to prevent the centrifugal compressor 1 from becoming a surging state during the control, it is conventionally disclosed in Japanese Patent Laid-Open No. 55-107097. The control means of the centrifugal compressor having such surging prevention means is used.

In this conventional control means, as shown in FIG. 8, the surging prevention line P ₀ is set based on the surging start lines S _i (i = 1 to 4) of the first to fourth stages, and the surging prevention line P ₀ is set. ₀ is programmed and stored in advance in the storage unit in the control device 23. In addition, the storage unit also stores the inlet guide vanes of each stage as the operation amount for achieving the optimum operating condition.
The optimum combination values of the angles of 11 to 14 and the diff user vanes 15 to 18 are stored (in FIG. 8, the curve C _j : j
= 0 to 3 indicates the flow rate-pressure ratio characteristic curve for each combination of the inlet guide vane and the diff user vane).

Then, the controller 23, as shown in FIG.
When the state detection value is received from 20 to 22 (step S1), the operating state of each stage of the centrifugal compressor 1 is made to correspond to that shown in FIG. 8 from the detected value (step S2) to determine whether or not it is necessary to prevent surging. It is determined whether or not (step S3). If it is determined that it is not necessary to prevent surging, the current operating state is maintained, while if it is determined that surging needs to be prevented (that is, surging state), it is determined whether blow-off valve control is necessary. Judge (step S4). That is, according to the surging state, the blow-off valve (not shown) is controlled to be opened (step S5), or the inlet guide vane control and the diff user vane control of the surging stage are performed (step S5).
6) Judge.

In this way, after the surging is prevented, the inlet guide vane control and the diff user vane control of stages other than the surging stage are performed (step S7). Here, the inlet guide vane control and the diff user vane control are performed by the previously stored inlet guide vanes 11 to 14 as described above.
And Diff user vanes 15 to 18 are appropriately selected and changed.

[Problems to be Solved by the Invention] However, the control means of the conventional centrifugal compressor as described above performs processing so as to prevent surging after each stage of the centrifugal compressor 1 is actually in the surging state. Since it does not prevent the surging area from being reached in advance, the inlet guide vane 11 at the start of control
~ 14 and the diff user vanes 15-18 are near the surging line SL, and the target flow rate line is within the surging area, as shown by the solid arrow in Fig. 4, the surging does not occur. The driving state of eliminating the above condition is repeated, and the driving state becomes extremely unstable.

The present invention seeks to solve such a problem, and when the surging state is reached, the state is quickly resolved, while the surging state is likely to occur. It is an object of the present invention to provide a method capable of controlling a centrifugal compressor while avoiding the above.

[Means for Solving Problems] Therefore, in the method for controlling the centrifugal compressor according to the present invention, the surging line that defines the surging area on the vane angle plane determined by the angles of the inlet guide vane and the diff user vane is previously set. After setting and remembering,
The current angles of the inlet guide vanes and the diff user vanes are measured, and if these current angles fall within the surging area defined by the surging line, it is a normal direction vector of the surging line. The one that goes out of the surging area and the one that adjusts the operation amount of the angle of the inlet guide vane and the diffuser vane necessary to get out of the surging area is obtained as the vane angle operation amount vector for surging elimination, while the measured current When the angle is in the vicinity of the surging line outside the sag jig area and the vane angle manipulated variable vector determined to go toward the target flow rate goes into the surging area, from the vane angle manipulated variable vector based on the surging line. Normal direction of the surging line The component is removed to obtain the surging avoidance vane angle operation amount vector in the direction along the surging line, and the surging elimination vane angle operation amount vector or the surging avoidance vane angle operation amount vector is used to determine the above. The flow rate of the centrifugal compressor is controlled based on the angles of the inlet guide vanes and the diff user vanes.

[Embodiment of the Invention] A method of controlling a centrifugal compressor according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart thereof. First, a method according to the present embodiment will be described. First, the configuration of the centrifugal compressor to which the method of this embodiment is applied will be described with reference to FIG. In FIG. 6, the same reference numerals as those in FIG. 7 indicate almost the same parts, and the description thereof will be omitted. However, the sixth
In the multi-stage centrifugal compressor to which the control device of this embodiment shown in the figure is applied, the compressors 4 to 7 are all overhung on the same shaft end and the power transmission gear 3 is omitted. It is different from the machine.

As shown in FIG. 6, in the multi-stage centrifugal compressor according to the present embodiment, the inlet guide vanes (GV) 11-14 are driven by the inlet guide vane drive devices 19a-19d, respectively, and the diff user vanes (DV). 15-18 are driven by Diff user vane drive devices 19e-19h, respectively. As the sensors, in addition to the flow rate sensor 20, the temperature sensor 21, and the pressure sensor 22, a rotation speed sensor 24 that detects the compressor rotation speed and a humidity sensor 27 are provided.

The detection signals from the sensors 20-22, 24, 27 are all input to the control device 28, and the control device 28 controls the flow rate in the centrifugal compressor 1 so that the inlet guide vanes are controlled. 11-14 and Diff user vanes 15-18
It is possible to receive each detection signal so as to adjust the respective angles and to calculate and output an appropriate control signal to each drive device 19a to 19h.

Next, a case where the control method of the present embodiment is applied to the centrifugal compressor as described above will be described with reference to FIGS. First, before starting the control, the storage section of the control device 28 has an inlet guide vane 11 to 14 and a diff user vane.
On the vane angle plane (αβ plane) determined by the angles (α, β) of 15 to 18, it is a function of the vane angle (α, β) and the flow rate Q and the efficiency η corresponding to these vane angles (α, β). The flow rate characteristic function f ₁ = Q (α, β) and the efficiency characteristic function f ₂ = η (α, β) are given by mathematical modeling in advance and set in the surging region (Figs. 2 and 4). The surging line SL (see FIG. 2) that defines the hatched area is also mathematically modeled and set as g = G (α, β) = 0. The normalized flow rate characteristic function Q / Q _D obtained by dividing the flow rate Q corresponding to the vane angle (α, β) given by the flow rate characteristic function f ₁ by the standard flow rate Q _D specific to the centrifugal compressor. And the normalized efficiency characteristic function η / η _D obtained by dividing the efficiency η corresponding to the vane angle (α, β) given by the efficiency characteristic function f ₂ by the standard efficiency η _D specific to the centrifugal compressor. Each of them is shown by a broken line and a solid line in FIG. 2, and these can be easily obtained by approximation by selecting an appropriate sample from the short-term actual machine operation data. The normalization in the above means adjusting so that the maximum values of Q / Q _D and η / η _D are expressed in the vicinity of 1.0.

Then, in the control method in this embodiment, as shown in FIG. 1, when the current angles of the inlet guide vanes 11 to 14 and the diff user vanes 15 to 18 are in the surging area, the surging is performed by steps A4 to A6. On the other hand, when the vane angle control is possible to enter the surging area, the surging avoiding method according to steps A9 to A11 is performed. In addition,
When it is not necessary to eliminate or avoid surging, in this embodiment, a control method called a hill climbing method by steps A7 and A12 to A17 is executed to control the flow rate of the centrifugal compressor 1 by the control device 28. There is.

When controlling the flow rate of the centrifugal compressor 1, first, the target flow rate Q _FIN is set (step A1), and then the current angles (α, β) of the inlet guide vanes 11-14 and the diff user vanes 15-18 are set. ) Is measured (step A2). Then, it is determined from the measured vane angles (α, β) whether this current angle is within the preset surging area (step A3). On the other hand, if it is within the surging area [G
When (α, β) <0], the process proceeds to the next step A4. At this time, the current flow rate Q at the vane angle (α, β)
_NOW can be obtained (estimated) by a preset flow rate characteristic function f ₁ .

When it is determined that the current vane angle (α ₀ , β ₀ ) is within the surging area, the shortest operation path for eliminating surging is naturally the surge as shown in FIG. 3 (a). This is the normal direction vector, as it is the direction toward the outside of the surging area in the normal direction (∂g / ∂α, ∂g / ∂β) of the light SL [g = G (α, β) = 0]. The vane angle manipulated variable vector (Δα ₄ , Δβ ₄ ) for surging elimination is determined as the one that goes out of the region. here,
The manipulated variable is proportional to the difference between the boundary line G (α, β) = 0 and the current surging function value G (α ₀ , β ₀ ). As a result, the vane angle operation amount vector for surging elimination (Δα ₄ , Δβ ₄ ) is obtained (step A4), and this is output as the vane angle operation amount vector (Δα, Δβ) (step A5).

Then, the calculated vane angle operation amounts Δα and Δβ
But the entrance guide vanes 11-14 and Diff user vanes
If the maximum allowable operation amount of 15 to 18 is exceeded, that is, the angle that can be driven at one time is exceeded,
The vane angle operation amount Δα or [Delta] [beta], leave substituted into Rimitsuta function F _L (x) as shown in FIG. 5, when exceeding the maximum allowed operation amount vane angle operation amount Δα or Δ
β is reduced, and the controller based on the vane angle operation amount vector (Δα, Δβ) thus obtained
A control signal is output from 28 to the drive devices 19a to 19h to drive and control the inlet guide vanes 11 to 14 and the differential user vanes 15 to 18 (step A6).

After that, the process returns to step A2 again, and it is determined by step A3 whether or not it is within the current surging region, and the above steps A4 to A6 are repeated until the vane angle (α, β) is outside the surging region. Then, the surging state is promptly resolved.

On the other hand, at step A3, the current vane angle (α,
If β) is determined not to be within the surging region,
First, the first vane angle manipulated variable vector (Δα ₁ , Δβ ₁ ) toward the target flow rate Q _FIN is obtained as follows. That is, with respect to the equal flow rate curve G (α, β) = Q _NOW at the current vane angle (α, β) determined by the flow rate characteristic function f ₁ , the normal direction of this equal flow rate curve (∂f ₁ / ∂α , ∂f ₁ / ∂
In the direction toward the target flow rate Q _FIN side at β), the vane angle (α,
By driving β), the shortest operation path can be obtained.
This normal direction vector, which is directed to the target flow rate Q _FIN , is obtained as the first vane angle manipulated variable vector (Δα ₁ , Δβ ₁ ). Here, the vane angle operation amount vector (Δα
Assuming that the flow rate corrected based on ₁ , Δβ ₁ ) is ΔQ, ΔQ = (∂f ₁ / ∂α) Δα ₁ + (∂f ₁ / ∂β) Δβ ₁ ......
(2) and the vane angle manipulated variables Δα ₁ and Δβ ₁ are the target flow rates.
Since it is proportional to the difference between Q _FIN and the current flow rate Q _NOW , considering the above normal direction, As the first vane angle manipulated variable vector (Δα ₁ , Δβ
₁ ) can be obtained. Note that K ₁ represents a tuning parameter.

In this way, after the first vane angle manipulated variable vector (Δα ₁ , Δβ ₁ ) is obtained in step A7, the current vane angle (α, β) is in the vicinity of the surging line SL shown in FIG. It is determined whether or not there is (step A8).
Then, while moving to step A12 to be described later if not in the vicinity of the surging line SL, when the case [G (α, β) < e G in the vicinity of the surge line SL; the proviso e _G 0
[Positive value close to] moves to the next step A9.

In step A9, first, the first vane angle manipulated variable vector (Δα ₁ , Δ) obtained in step A7.
As shown in FIG. 3 (b), it is determined whether or not β ₁ ) is within the surging region. If not, the first vane angle manipulated variable vector (Δα ₁ , Δ
β ₁ ) is the vane angle manipulated variable vector (Δα, Δ)
By outputting as β) (step A11) and shifting to step A14, it is possible to quickly avoid from the vicinity of the surging line SL without considering the efficiency improvement by the second vane angle operation amount vector described later.

On the other hand, in step A9, if it is determined that the first vane angle operation amount vector (Δα ₁ , Δβ ₁ ) is directed to the surging region as shown in FIG. By removing the component heading toward the surging region from the first vane angle manipulated variable vector (Δα ₁ , Δβ ₁ ) as described above, the vane angle manipulated variable vector (Δα ₅ , Δβ ₅ ) for avoiding surging along the surging line Seek to avoid surging. Here, the unit vector in the normal direction of the surging line SL that goes into the surging area is Then Then, using the equation (4), the surging avoidance vane angle operation amount vector (Δα ₅ , Δ as shown in the following equation (5) is calculated from the first vane angle operation amount vector (Δα ₁ , Δβ ₁ ).
β ₅ ) is required.

Is.

In this way, the surging avoidance vane angle operation amount vector (Δα ₅ , Δ) along the surging line SL from the first vane angle operation amount vector (Δα ₁ , Δβ ₁ ).
β ₅ ) is obtained (step A10), and the vane angle operation amount vector (Δα ₅ , Δβ ₅ ) is output as a vane angle operation amount vector (Δα, Δβ) (step A11).
By moving to 14, the vane angle is surging line SL
Even in the vicinity, as indicated by the double-lined arrow in FIG. 4, the flow rate control of the centrifugal compressor 1 is performed without considering the improvement in efficiency and avoiding entering the surging region. is there.

The procedure after step A14 will be described in the mountain climbing method described later.

On the other hand, if it is determined at step A8 that the current vane angle (α, β) is near the surging line SL shown in FIG. 2, then at step A12, the target flow rate Q _FIN is approached by the shortest path. The second vane angle manipulated variable vector (Δα ₂ , Δβ ₂ ) is set so that the efficiency is increased with respect to the obtained first vane angle manipulated variable vector (Δα ₁ , Δβ ₁ ), without changing the flow rate. ). That is,
As with the flow control in step A7 as described above, current vane angle determined by the efficiency characteristic function f ₂ (alpha,
For the isoefficiency curve η (α, β) = η _NOW in β), the normal direction of this isoefficiency curve (∂f ₂ / ∂α, ∂f ₂ / ∂
If the vane angle (α, β) is driven in the direction of β) and the improvement efficiency Δη becomes positive, the efficiency η is improved. Here, the second vane angle operation amount vector (Δα ₂ , Δ
The efficiency Δη that is improved based on β ₂ ) is Δη = (∂f ₂ / ∂α) Δα ₂ + (∂f ₂ / ∂β) Δβ ₂ ......
It is expressed as (6). At this time, in order to prevent the flow rate from changing due to the operation for improving efficiency, the vane angle operation amount Δα ₂ ,
In order to make the flow rate change ΔQ due to Δβ ₂ zero, from the formula (2), (∂f ₁ / ∂α) Δα ₂ + (∂f ₁ / ∂β) Δβ ₂ = 0 ......
The vane angle operation amounts Δα ₂ and Δβ ₂ are determined so as to satisfy (7). That is, when the tangential vector of the above equal flow rate curve and the improvement efficiency Δη> 0 is obtained from the equations (6) and (7), As the second vane angle manipulated variable vector (Δα ₂ , Δβ
₂ ) can be obtained. K ₂ represents a tuning parameter.

Then, the first vane angle operation amount vector (Δα ₁ , Δ
β ₁ ) and the second vane angle manipulated variable vector (Δα ₂ ,
By adding Δβ ₂ ), a third vane angle manipulated variable vector (Δα ₃ , Δβ ₃ ) that can improve efficiency while bringing the flow rate closer to the target flow rate Q _FIN is obtained, and the vane angle manipulated variable vector (Δα, Δβ) is obtained. ) As (step
A13). That is, the calculation based on the following equation (9) is performed.

Then, as in the case of step A6, when the obtained vane angle operation amounts Δα and Δβ exceed the maximum allowable operation amounts of the inlet guide vanes 11-14 and the diff user vanes 15-18, the vane angle operation is performed. If the vane angle (α, β) is driven based on the vane angle operation amount vector (Δα, Δβ) obtained up to step A14 after the amount Δα or Δβ is reduced, When it is determined that the new vane angle (α + Δα, β + Δβ) changed by the operation falls within the surging region, the vane angle operation amount vector (Δα, Δβ) is reduced in size and output (step A15). ). Based on the vane angle manipulated variable vector (Δα, Δβ) thus obtained,
The control device 23 outputs a control signal to the drive devices 19a to 19h,
Inlet guide vanes 11-14 and Diff user vanes 15-
Drive and control 18 (step A16).

Then, it is judged whether or not the flow rate changed by the above vane drive control has reached the vicinity of the target flow rate Q _FIN (step A17), and if it has not reached, it returns to step A7 again and the vane angle by the hill climbing method. While continuing the control, when it is determined that the vicinity of the target flow rate Q _FIN has been reached, the flow rate control is terminated at that point. Here, there are the following determination methods in step A17.

(I) The current flow rate Q _NOW is estimated from the preset flow rate characteristic function f ₁ based on the current vane angle (α, β) obtained by the vane drive control, and the estimated value Q _NOW and the target flow rate are calculated. Compared with Q _FIN , the difference between the two is a constant value Within, that is, If so, it is determined that the vicinity of the target flow rate Q _FIN has been reached.

(Ii) The vane angle manipulated variables Δα and Δβ are | Δα | ≦ ε ₁
When | Δβ | ≦ ε ₂ (when no further operation is performed), it is determined that the vicinity of the target flow rate Q _FIN has been reached.

(Iii) The vane angle manipulated variables Δα and Δβ are If so, it is determined that the vicinity of the target flow rate Q _FIN has been reached.

As described above, according to this embodiment, the inlet guide vane
When the current angles of 11 to 14 and Diff user vanes 15 to 18 are within the surging area, the surging state is quickly eliminated by steps A4 to A6, and the vane angle control by the hill climbing method enters the surging area. If there is a possibility, as shown in Fig. 4, steps A9-A1
By 1 it is possible to reliably avoid a surging state.

Further, in the present embodiment, the mountain climbing method (steps A7, A12 to A1
By means of 7), the flow rate of the centrifugal compressor 1 can be made to reach the vicinity of the target flow rate Q _FIN while maintaining high efficiency on the map of the flow rate characteristic function and the efficiency characteristic function, so that flow rate control and efficiency improvement can be achieved. This can be done simultaneously, and the efficiency in the middle of control is quantitatively guaranteed, and any target flow rate Q
_{It is} also possible to obtain a general-purpose centrifugal compressor control method that is effective for _FIN .

When carrying out the control method of the above embodiment,
The inlet guide vanes 11 to 14 and the diff user vanes 15 to 18 of all stages may be separately controlled by the above control method for each stage, or the inlet guide vanes 11 to 14 and the diff user vanes 15 of all stages may be controlled. It is also possible to drive-control 18 to 18 at the same angle. Further, the angles of the inlet guide vanes 11 to 14 and the diff user vanes 15 to 18 are set so that the operation flow rates of the centrifugal compressors 4 to 7 at the respective stages become similar operation flow rates having the same ratio to the design flow rate. Dimensional inlet guide vane angle and dimensionless diff user vane angle are expressed respectively, and the vane angle control is performed by regarding the inlet guide vanes 11 to 14 and the diff user vanes 15 to 18 of each stage as one set. You may do it.

Further, in the hill climbing method of the above embodiment, in order to improve the approximation accuracy of the mathematical model, the characteristic function f ₁ , f ₂ is a high-order expression, or the region is divided and represented by a plurality of functions,
Alternatively, it is conceivable to use some means to correct the parameters in the characteristic function based on the measured values. Also,
In the hill climbing method of the above embodiment, the characteristic functions f ₁ and f ₂ are functions of the angles of the inlet guide vanes 11 to 14 and the diff user vanes 15 to 18, but the terms such as temperature, humidity and rotation speed are included. You may formulate it.

Furthermore, although the method of the present invention is applied to a multi-stage centrifugal compressor in the above-mentioned embodiments, it can be applied to a single-stage centrifugal compressor in the same manner.

As described above, according to the present invention, when the current angles of the inlet guide vane and the diff user vane are within the preset surging area, the surging state is promptly resolved. In addition, when there is a possibility of entering the surging area due to the vane angle control, it is possible to reliably avoid the surging state, and it is possible to reliably prevent the unstable operating state. is there.

[Brief description of drawings]

1 to 6 show a control method of a centrifugal compressor as one embodiment of the present invention. FIG. 1 is a flow chart thereof, and FIG. 2 is a normalized flow rate characteristic function Q / Q _D , a normal FIG. 3 (a) is a graph showing a model example of the simplified efficiency characteristic function η / η _D and surging line SL, FIG. 3 (a) is a graph for explaining the surging elimination method in the present embodiment, and FIG. 3 (b) is FIG. 4 is a graph for explaining the surging avoidance method in the present embodiment, FIG. 4 is a graph for explaining the effect of the present embodiment in comparison with the case of the conventional means, and FIG. 5 is a graph showing an example of the limiter function thereof. FIG. 6 is a block diagram showing a centrifugal compressor to which the method of this embodiment is applied, FIG. 7 is a block diagram showing a conventional general multistage centrifugal compressor, and FIGS. 8 and 9 are conventional centrifugal compressors. Fig. 8 shows the compressor control method. Fig. 8 shows the compressor characteristic curve. FIG. 9 is a flow chart showing the graph. In the figure, 1 ... Centrifugal compressor, 11-14 ... Inlet guide vanes, 15-18 ... Diff user vanes, 19a-19d ...
Inlet guide vane drive device, 19f ~ 19h ... Diff user vane drive device, 20 ... Flow sensor, 21 ... Temperature sensor, 22 ... Pressure sensor, 24 ... Rotation speed sensor, 27 ... Humidity sensor, 28 ……Control device.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-55-107097 (JP, A) JP-A-55-123394 (JP, A) JP-A-55-60692 (JP, A) JP-A-55- 60693 (JP, A)

Claims (1)

[Claims] 1. A centrifugal compressor having an inlet guide vane and a diffuser vane with variable angles on the inlet side and the outlet side, respectively, by adjusting the angles of the inlet guide vane and the diffuser vane. In controlling the flow rate in the above, first, the surging line that defines the surging area on the vane angle plane determined by the angles of the inlet guide vane and the diffuser vane is preset and stored, and then the inlet guide vane described above is stored. And the current angles of the diffuser vanes are measured, and if these current angles are within the surging area defined by the surging line, it is the normal direction vector of the surging line and goes outside the surging area. To get out of the surging area with something The required inlet guide vane and day diffuser vane angle operation amounts have been adjusted as the surging elimination vane angle operation amount vector, and the inlet guide vane and day are determined by the surging elimination vane angle operation amount vector. The flow rate of the centrifugal compressor is controlled based on the angle of the fuser vane, while the measured current angle is near the surging line outside the surging region and the vane angle manipulated variable vector determined toward the target flow rate is When heading into the surging area, the normal direction component of the surging line is removed from the vane angle operation amount vector based on the surging line to remove the surging avoidance vane angle operation amount vector in the direction along the surging line. Asked, this surging times It said inlet guide vane and a control method for a centrifugal compressor, characterized by controlling the flow rate of the centrifugal compressor based on the angle of the Day fuser vanes is determined by the use vane angle operation amount vector.