JP2805892B2 - Control device for gas turbine for generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a control device for a two-shaft gas turbine with a variable guide blade (variable nozzle) for a generator.

<Prior Art> As a conventional gas turbine, for example, FIGS.
There is one shown in the figure (see Japanese Utility Model Publication No. 61-20265).

First, the outline of the two-shaft gas turbine shown in FIG. 8 will be described. The compressor 1 is connected to the compressor turbine 3 by the gas generator shaft 2, and the power turbine 4 is connected to the generator 7 by the output shaft 5 via the gearbox 6. Have been.

The air (atmospheric AT) is compressed by the compressor 1 and heated through the heat exchanger 8 before reaching the combustor 9. Fuel is supplied from the fuel pump 10 to the combustor 9 through the fuel regulating valve 11. Here, the fuel control valve 11 is driven by the valve drive mechanism 12 to adjust the fuel flow rate. In the combustor 9, the fuel is mixed with the air and burned. The combustion gas enters the compressor turbine 3 and performs work. Thus, the compressor 1 is driven by the output of the compressor turbine 3.

The combustion gas leaving the compressor turbine 3 enters the power turbine 4 via a variable guide vane (variable nozzle) 13 and performs work. As a result, the generator 7 is driven by the output of the power turbine 4. Here, the variable guide vanes 13 are driven by a vane drive mechanism 14 to control the output. The combustion gas exiting the power turbine 4 passes through the heat exchanger 8 and is exhausted EX.
Is discharged as

As shown in FIG. 9, the device for controlling this system includes a control circuit (control signal calculator) 20 for the valve drive mechanism 12 and the blade drive mechanism 14, and detects the load _LPT of the generator 7. Generator load detector 21, rotating speed of gas generator shaft 2 (hereinafter referred to as gas generator rotating speed) _NGG , gas generator rotating speed detector 22, and rotating speed of output shaft 5 (hereinafter referred to as power turbine speed) power turbine speed detector 23 for detecting the N _PT, an input of the control signal calculation a signal from the compressor inlet temperature detector 24 for detecting the compressor inlet temperature T _1.

Fuel flow rate G supported by the valve drive mechanism 12 of the fuel regulating valve 11
_FSET is first arithmetic circuit 20A by the generator load L _PT and the compressor inlet temperature T ₁ of Tokyo from the target gas generator speed N
Seeking _GGSET, followed by calculation circuit 20B, the actual gas generator speed N _GG target gas generator speed N
_Perform PID control in closed loop to match _GGSET ,
decide.

The variable nozzle angle θ _VNSET instructed to the wing drive mechanism 14 of the variable guide wing (variable nozzle) 13 is calculated by an arithmetic circuit 20C
Accordingly, in order to match the actual power of the constant of the turbine speed N _PT is determined by the generator frequency specification target power turbine speed N _PTSET, performs PID control of a closed loop, is determined.

<Problems to be Solved by the Invention> However, in such a conventional gas turbine control device, control is performed such that only the control of the fuel flow rate (the target value of the gas generator rotation speed) follows the change in the generator load. Because of this method, there is a problem that the ability to follow a load change is poor, such as when a load is turned on or off.

Therefore, in controlling the variable guide vanes, the feedforward amount of the angle of the variable guide vanes is calculated in consideration of the generator load, and based on this feedforward amount and the deviation between the power turbine speed and a constant target value. Proposed to control the angle of the variable guide wing (Japanese Patent Application Sho 63)
-156920).

However, in this device, a large load load is mainly handled by feedforward, and the feedback control gain is set regardless of the presence or absence of the load load. When controlling the number of drops, the effect of the increase in output due to the acceleration of the gas generator shaft could not be covered by the control of the variable guide vanes, resulting in a large overshoot in the number of revolutions, leaving room for improvement.

The present invention has been made in view of such a problem, and can control the power turbine speed constantly even for a large load change.
An object of the present invention is to provide a control device for a gas turbine for a generator that can satisfy strict frequency specifications.

<Problems to be Solved by the Invention> For this reason, as shown in FIG. 1, in the present invention, a fuel metered by a fuel regulating valve in a combustor is burned by air compressed by a compressor, and a combustion gas To the compressor turbine, drives the compressor connected to the compressor turbine via a gas generator shaft, and supplies the combustion gas exiting the compressor turbine to a power turbine via a variable guide vane to supply this power. In a generator gas turbine configured to drive a generator connected to an output shaft of the turbine, the following (a) to (a) to
The control device is configured by providing the means (j).

(A) Load detection means for detecting the generator load (b) Gas generator rotation number detection means for detecting the rotation number of the gas generator shaft (c) Power turbine rotation number detection means for detecting the rotation number of the output shaft of the power turbine (D) Compressor inlet temperature detecting means for detecting compressor inlet temperature (e) Compressor inlet pressure detecting means for detecting compressor inlet pressure (f) Target of rotation speed of gas generator shaft based on generator load, compressor inlet temperature and pressure Target gas generator rotation speed calculating means for calculating a value (g) fuel flow control means (g) for controlling the fuel flow rate by the fuel regulating valve based on these deviations so that the rotation speed of the gas generator shaft matches the target value. h) Generator load, compressor inlet temperature and pressure, gas generator shaft speed, Feedforward amount calculating means for calculating the feedforward amount of the angle of the variable guide vane from the feedforward amount and the output shaft of the power turbine so as to set the rotation speed of the output shaft of the power turbine to a constant target value. Variable guide vane control means for controlling the angle of the variable guide vane based on the difference between the rotational speed of the motor and a fixed target value; (j) detecting a load change of a generator load equal to or greater than a predetermined value, Control gain changing means for increasing the control gain of the variable guide vane control means for a predetermined period <Operation> Regarding the control of the fuel flow rate, the generator load, compressor inlet temperature and pressure are controlled by the target gas generator rotational speed calculating means (f). The target value of the number of revolutions of the gas generator shaft is calculated from the above, and the fuel flow rate control means (g) calculates the number of revolutions of the gas generator shaft. In order to match the value, to control the fuel flow through the fuel control valve on the basis of these deviations.

As for the control of the variable guide vanes, the feed forward amount of the angle of the variable guide vanes is calculated by the feed forward amount calculating means (h) from the generator load, the compressor inlet temperature and pressure, and the rotation speed of the gas generator shaft. In order to set the rotation speed of the output shaft of the power turbine to a constant target value by the guide vane control means (i), the feedforward amount and the deviation between the rotation speed of the output shaft of the power turbine and the fixed target value are determined. The angle of the variable guide wing is controlled based on the angle.

Here, the control gain changing means (j) detects a load change equal to or more than a predetermined value with respect to the generator load, and when the load change is detected, the control gain of the variable guide vane control means (i) for a predetermined period. To increase the followability.

<Example> An example of the present invention will be described below.

Configuration of the gas turbine is the same as FIG. 8, as a detector, as indicated by a chain line in the drawing, a compressor inlet pressure detector 25 for detecting a compressor inlet pressure P ₁ is provided in addition. This is for detecting the compressor inlet state more accurately.

Note that the generator load detector 21 corresponds to load detection means, the gas generator rotation number detector 22 corresponds to gas generator rotation number detection means, and the power turbine rotation number detector 23 corresponds to power turbine rotation number detection means. The compressor inlet temperature detector 24 corresponds to compressor inlet temperature detecting means, and the compressor inlet pressure detector 25 corresponds to compressor inlet pressure detecting means.

The control circuit is configured as shown at 30 in FIG. 2 and includes arithmetic circuits 31 to 37.

The arithmetic circuit 31 calculates the generator load L _PT by using the compressor inlet temperature T ₁ and the compressor inlet pressure P ₁ according to the following equation.
Correct and _calculate the corrected load L _PT ^* .

L _PT ^* = (P ₀₀ / P ₁ ) × SQR (T ₀₀ / T ₁ ) × L _PT where T ₀₀ and P ₀₀ are standard temperatures and pressures for creating a correction value in consideration of the compressor inlet condition. is there.

 SQR (X) represents the square root of X.

Arithmetic circuit 32, a gas generator rotational speed N _GG was modified according to the following equation by the compressor inlet temperature T _1, obtaining the modified gas generator rotational speed N _GG ^*.

N _GG ^* = SQR (T ₀₀ / T ₁ ) × N _GG calculation circuit 33 obtains the target gas generator rotation speed N _GGSET ^* from the corrected load L _PT ^* .

Therefore, the operation circuits 31, 33 are target gas generator rotation speed operation means.

The arithmetic circuit 34 performs closed-loop PID control based on these deviations so that the corrected gas generator rotation speed N _GG ^* matches the target gas generator rotation speed N _GGSET ^*. Fuel flow to support 12
Determine G _FSET .

 Therefore, the arithmetic circuit 34 is a fuel flow control means.

The arithmetic circuit 35 calculates a variable guide wing (variable nozzle) 1 based on the corrected load L _PT ^* and the corrected gas generator speed N _GG ^*.
The feedforward amount θ _VNFF of the variable nozzle angle instructed to the third blade drive mechanism 14 is obtained.

Therefore, the operation circuits 31, 32, and 35 are feedforward amount operation means.

The arithmetic circuit 36 uses the feedforward amount θ _VNFF as a basis, and calculates the actual power turbine rotational speed N _PT as the target power turbine rotational speed determined by the power generation frequency.
Based on these deviations, a closed loop PID control is performed to match the N _PTSET, and a variable nozzle angle θ _VNSET to be instructed to the blade drive mechanism 14 of the variable guide blade (variable nozzle) 13 is determined. Specifically, the variable nozzle angle θ _VNSET is determined by adding the PID amount based on the deviation to the feedforward amount θ _VNFF .

 Therefore, the arithmetic circuit 36 is a variable guide wing control means.

The arithmetic circuit 37 calculates the target gas generator rotation speed N _GGSET ^*
And actual rotation (corrected gas generator rotation speed) N _GG ^*
It is determined that a load has been applied when this difference is equal to or greater than a predetermined value, and for a predetermined period from that time, the power turbine speed N _PT and the target power turbine speed N _PTSET in the arithmetic circuit 36 are _compared . The control gain of the closed-loop PID control based on the deviation is increased to provide a sensitive control system.

In this example, the load change is detected based on the difference between N _GGSET ^* and N _GG ^* . However, it is needless to say that the load change may be directly detected from the change in the actual generator load L _PT. .

Therefore, the arithmetic circuit 37 is a control gain changing means for detecting a load change of a generator load equal to or more than a predetermined value, and increasing the control gain of the variable guide wing control means for a predetermined period upon detection.

FIG. 3 shows a control flow as a flowchart.

That is, in step 1 (shown as S1 in the figure, the same applies hereinafter), the generator load L _PT , the gas generator speed N _GG ,
The power turbine speed N _PT , compressor inlet temperature T ₁ , and compressor inlet pressure P ₁ are detected.

Step modified from the 2 and generator load L _PT compressor inlet temperature T ₁ of the compressor inlet pressure P ₁ Metropolitan calculates the load L _PT ^*.

Step 3 In the gas generator speed N _GG and the compressor inlet temperature T ₁ of Tokyo from the modified gas generator speed N
Calculate _GG ^* .

In step 4, the target gas generator speed N _GGSET ^* is calculated from the corrected load L _PT ^* by referring to the map.

In step 5, the target gas generator speed N _GGSET ^*
And the actual rotation speed N _GG ^* is calculated.

In step 6, a comparison value ε _max is retrieved from the corrected gas generator speed N _GG ^* and the compressor inlet temperature T ₁ with reference to a map.

In step 7, it is determined whether or not the flag SW = 1, and if NO, the process proceeds to the next step 8.

In step 8 ε> ε _max whether determined, if NO, the process proceeds to the next step 9.

In step 9, the control gain of the PID control based on the comparison between the power turbine speed N _PT and the target putter turbine speed N _PTSET in step 17 described below (hereinafter referred to as the gain of the θ _VN −N _PT control unit) in a steady state Use things. That is, the control gain is set to a small value suitable for a steady state. Thereafter, the process proceeds to step S16.

In step 16, the feedforward amount _θVNFF of the variable nozzle angle is calculated by referring to the map from the corrected load L _P T ^* and the corrected gas generator speed N _GG ^* .

In step 17, the feedforward amount θ _VNFF is used,
The variable nozzle angle θ _VNSET is determined by PID control with feedforward _based on a comparison between the power turbine speed N _PT and the target power turbine speed N _PTSET .
The control gain here is the one set in step 9 or step 12.

In step 18, the PID is obtained from a comparison between the corrected gas generator speed N _GG ^* and the target gas generator speed N _GGSET ^*.
The fuel flow rate _GFSET is determined by control.

In step 19, _GFSET and _θVNSET are output.

Considering the case where there is a load change equal to or more than a predetermined value, in this case, first, in the determination in step 8, ε> ε _max
As a result, the process proceeds to step 10.

 In step 10, the flag SW = 1 is set.

 Next, at step 11, the timer t = 0.

Next, in step 12, the gain of the θ _VN −N _PT control unit during acceleration is used. That is, the control gain is set to a large value suitable for acceleration.

 Next, in step 13, the timer t is added by Δt.

Next, at step 14, it is determined whether or not t> t _max . If NO, the process proceeds to step 16.

Immediately after the detection of the load change equal to or more than the predetermined value, since the flag SW = 1 in the determination in step 7, the steps from step 7
Proceed to step 12 to continue using the gain of the θ _VN -N _PT control unit at the time of acceleration.

If a predetermined time equivalent to _tmax has elapsed after the detection of the load change equal to or more than the predetermined value, since t> _tmax is determined in step 14, the process proceeds from step 14 to step 15, where the flag SW = 0
And Therefore, after this, the gain of the θ _VN −N _PT control unit in the steady state will be used from the next time.

As described above, in the present invention, a load change equal to or more than a predetermined value is detected, and at the time of the detection, the control gain of the θ _VN −N _PT control unit is increased for a predetermined period. .

When the control gain of the feedback system is increased, the response to a change is improved. On the other hand, when the control gain is excessively increased, the sensitivity becomes too high, which causes a problem such as being easily influenced by noise or oscillating easily.

Especially, in the θ _VN -N _PT control unit, the control input is a variable guide blade driven in high-temperature gas, so this becomes the limit of oscillation, and if fine movements are constantly repeated, the wear of each sliding unit increases. , The durability is impaired.

Therefore, if PID control with feedforward is used, it is sufficient to respond to a large load change by feedforward, so that a good frequency characteristic can be obtained for a step-like load change without increasing the gain of the feedback system. Can be.

However, as described above, when feedforward is applied to both the variable nozzle angle and the gas generator rotation speed, there is a problem that the overshoot of the power turbine rotation speed caused by the delay of the gas generator shaft acceleration during load application cannot be suppressed well. Was.

This is shown in FIG. FIG. 4 shows how the power turbine speed N _PT , the gas generator speed N _GG , and the variable nozzle angle θ _VN change. FIG. 4 (a) shows load input, and FIG. This is an example. At the time of load application, the power turbine speed N _PT has overshot significantly.

For this reason, the present invention increases the gain of the θ _VN −N _PT control unit only during a certain period immediately after detecting a large load application, suppresses this overshoot, and employs a smaller gain in normal times, The purpose is to prevent wear of the variable nozzle system. Thus, the control characteristics are as shown in FIG.

 Next, another embodiment shown in FIG. 6 will be described.

In this embodiment, a part of the flowchart of FIG. 3 is changed. The period in which the limit gain is increased is not simply set as the time after detection, but as shown in FIG. _A predetermined time t after the fluctuation of _{PT falls} within a certain range (upper limit N _PTH to lower limit N _PTL for N _PTSET )
_This is an example in which the method is changed to a method in which the control gain is increased until _{max has} elapsed.

To explain the gist of the flow chart, B1 is part of determining whether the power turbine speed N _PT has entered between the upper N _PTH and lower N _PTL, part for performing initialization when B2 is entering between, B3 Is a portion for setting the gain to be large, and B4 is a portion for exiting from the flow for increasing the gain after t _max seconds when the power turbine rotational speed becomes N _PTTH > N _PT > N _PTTL .

This embodiment has an advantage in that, as compared with the above-described embodiment, even if there is a load change continuously after load application, it is possible to cope with a large gain until rotation converges irrespective of the time.

<Effects of the Invention> As described above, according to the present invention, a load change of a predetermined value or more with respect to a generator load is detected, and when the load change is detected for a predetermined period, the control gain of the variable guide wing control means is increased. Therefore, an effect is obtained that the fluctuation of the rotation speed when a large load is applied can be suppressed while suppressing the excessive movement of the variable guide wing during the steady operation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram of a control circuit showing an embodiment of the present invention, FIG. 3 is a flowchart showing the flow of control, and FIGS. b)
FIG. 5 is a diagram showing a conventional response characteristic at the time of load application and cutoff, FIG. 5 is a diagram showing a response characteristic in the present invention, FIG. 6 is a flowchart showing another embodiment, and FIG. FIG. 8 shows a period in which the gain is increased, and FIG.
FIG. 1 is a diagram showing an outline of a gas turbine, and FIG. 9 is a block diagram of a conventional control circuit. 1 ... Compressor, 2 ... Gas generator shaft, 3 ...
... compressor turbine, 4 ... power turbine, 5 ...
... output shaft, 7 ... generator, 9 ... combustor, 10 ... fuel pump, 11 ... fuel regulating valve, 13 ... variable guide vanes (variable nozzle), 21 ... generator load detector, 22 …………………………………………………………………………………………………………………………………………… …………………………………………………………,

Claims (1)

(57) [Claims] 1. A fuel combusted by a fuel regulating valve in a combustor with air compressed by a compressor, supplies combustion gas to a compressor turbine, and is connected to the compressor turbine via a gas generator shaft. A generator gas that drives the compressor and supplies the combustion gas exiting the compressor turbine to a power turbine via a variable guide vane to drive a generator connected to an output shaft of the power turbine. In the turbine, load detection means for detecting a generator load, gas generator rotation number detection means for detecting the rotation number of the gas generator shaft, power turbine rotation number detection means for detecting the rotation number of the output shaft of the power turbine, A compressor inlet temperature detecting means for detecting a compressor inlet temperature; and a compressor inlet. A compressor inlet pressure detecting means for detecting a force, a target gas generator rotational speed calculating means for calculating a target value of a gas generator shaft rotational speed from a generator load, a compressor inlet temperature and a pressure, and a gas generator shaft rotational speed. A fuel flow control means for controlling a fuel flow rate by the fuel regulating valve based on these deviations so as to match the target value; and the variable based on a generator load, a compressor inlet temperature and pressure, and a rotation speed of a gas generator shaft. Feedforward amount calculation means for calculating the feedforward amount of the angle of the guide vane; and the feedforward amount, the rotation speed of the output shaft of the power turbine, Variable guide wing control means for controlling an angle of the variable guide wing based on a deviation from a fixed target value; Detecting a change in the load of a predetermined value or more for the generator load,
A control gain changing means for increasing a control gain of the variable guide vane control means for a predetermined period at the time of detection thereof, and a control device for a gas turbine for a generator.