JP4126973B2 - Gas turbine control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control system for a gas turbine power generation facility that uses a main fuel such as fermented methane gas whose calorific value fluctuates and an auxiliary fuel such as kerosene or natural gas whose calorific value is stable.
[0002]
[Prior art]
For example, in the sludge digestion gas generated from a sewage treatment plant, the calorific value fluctuates because the composition ratio of combustible components such as methane in the sludge gas fluctuates. Thus, in a gas turbine plant using a fuel whose calorific value fluctuates, it is necessary to control the gas turbine plant so as to maintain a certain performance corresponding to the fluctuation of the calorific value of the fuel.
[0003]
In other words, when the amount of heat generated by the fuel fluctuates, it is necessary to correct the parameters of the control device accordingly. As a method of automatically correcting the parameters of this control device that has been manually performed by skilled operators, a reference model indicating the relationship between the fuel flow rate of the gas turbine plant and the turbine rotational speed and the output of the actual plant are used. The present applicant has developed an adaptive control method corresponding to the calorific value fluctuation by obtaining a correction coefficient from the difference and applying this correction coefficient, and has already developed "Adaptive control method for sludge gas calorific value fluctuation" (Japanese Patent Application No. 2001). -047262) has been filed as a patent.
[0004]
FIG. 9 is a configuration diagram showing a configuration of an adaptive control method for a fluctuating calorific value of sludge gas that has already been filed.
[0005]
In this adaptive control method, control is performed by applying the output of the control device having the reference model 91, the adaptive rule 92, the proportional gain K, and the correction coefficient C (s) as elements to the actual plant 95.
[0006]
Here, the reference model 91 models the relationship between the fuel flow rate input to the gas turbine and the rotational speed of the gas turbine from the dynamic characteristic H (s) of the gas turbine in the actual plant 95.
[0007]
The adaptive rule 92 starts the gas turbine and reaches the rated rotational speed, but still has the rotational speed signal Ngm from the reference model 91 and the actual rotational speed Ng before entering the system. The comparison is performed to obtain the difference (Ng−Ngm), and the correction coefficient C (s) is calculated therefrom. After the gas turbine is inserted into the system, the application of the adaptive rule 92 is stopped. The correction coefficient C (s) obtained by the adaptive rule 92 is stored in the memory and used as an initial value at the next start.
[0008]
The fuel supplied to the gas turbine is a value obtained by comparing the required rotational speed Ngref and the actual rotational speed Ng, multiplying the difference (Ngref−Ng) by a proportional gain K, and further multiplying the correction coefficient C (s). The flow rate is controlled to be Wf.
[0009]
As described above, in the “adaptive control method for sludge gas calorific value fluctuation”, the correction coefficient C (s) is corrected every time the gas turbine is started by the adaptive rule 92. When it is stable but fluctuates over the long term, the parameters of the control device can be automatically rewritten to maintain optimum combustion without resorting to operator experience.
[0010]
[Problems to be solved by the invention]
However, the “adaptive control method for heat generation fluctuation of sludge gas” does not require the use of auxiliary fuel in the gas turbine, and the heat generation amount of the supplied fuel is stable in the short term, but long term. Is a method that assumes a fluctuating case, and is not applicable when the calorific value of the fuel fluctuates rapidly in a short period of time or when auxiliary fuel is used in combination.
[0011]
In other words, when the calorific value of the fuel supplied to the gas turbine fluctuates dramatically in a short period of time, an auxiliary fuel with a stable calorific value separate from the main fuel to prevent blowout and overheating due to sudden fluctuations in the calorific value. However, it is not assumed that different fuels are used together.
[0012]
Also, if the calorific value of the fuel fluctuates dramatically in a short period of time, it is necessary to correct the parameters of the control device even during load operation. However, the “Adaptive control method for sludge gas calorific value variation” It does not modify the parameters.
[0013]
The present invention has been made in view of such problems, and uses as a main fuel fermented methane gas or the like whose calorific value fluctuates rapidly in a short period of time, and further uses kerosene or natural gas whose calorific value is stable as an auxiliary fuel. It aims at providing the control system applicable also to the gas turbine power generation equipment used together.
[0014]
[Means for Solving the Problems]
The gas turbine control system according to the present invention controls a gas turbine that uses a main fuel whose calorific value fluctuates and an auxiliary fuel whose calorific value is constant as a control target, and a flow rate of the main fuel supplied to the gas turbine, In the gas turbine control system that controls the flow rate of the auxiliary fuel and the distribution ratio thereof, a reference model that calculates the model rotational speed and model output of the gas turbine based on the flow rate of the main fuel and the flow rate of the auxiliary fuel; When it is determined that the calorific value of the main fuel fluctuates based on the difference between the model rotational speed of the gas turbine and the actual rotational speed of the gas turbine in a state where the gas turbine is not juxtaposed in the system, the flow rate of the actual distribution rate and the main fuel of the engine speed and the main fuel Let 's is that matches the auxiliary fuel model rotational speed and the gas turbine of the turbine While adjusting, when the gas turbine is determined that the heat value of main fuel on the basis of the difference between the actual output of the gas turbine and the model output of the gas turbine in the state of being NamiIri to the system fluctuates, And a distribution ratio adjusting means for adjusting a distribution ratio of the main fuel and the auxiliary fuel and a flow rate of the main fuel so that a model output of the gas turbine matches an actual output of the gas turbine. .
[0015]
According to the present invention, when the gas turbine is not juxtaposed to the system, the gas turbine is juxtaposed to the system based on the difference between the model rotational speed of the gas turbine and the actual rotational speed of the gas turbine. In this case, when it is determined that the amount of heat generated by the main fuel fluctuates based on the difference between the model output of the gas turbine and the actual output of the gas turbine, the model rotational speed of the gas turbine matches the actual rotational speed of the gas turbine. Or the main fuel / auxiliary fuel distribution ratio and the main fuel flow rate are adjusted so that the model output of the gas turbine and the actual output of the gas turbine match, so the calorific value of the main fuel fluctuates drastically in a short time Even in this case, the optimum fuel distribution ratio can be maintained according to the heat generation amount of the main fuel.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to the present invention will be described in detail with reference to FIGS.
[0017]
FIG. 1 shows the overall configuration of an embodiment of the present invention.
[0018]
In the present embodiment, as shown in FIG. 1, the control system is composed of elements of a reference model 1, a distribution ratio adjustment logic 2, a proportional gain 3, and an input changeover switch 4, and is supplied to the actual plant 5 by the control system. The main fuel flow rate 26 and the auxiliary fuel flow rate 27 are controlled.
[0019]
Here, the reference model 1 creates the gas turbine model Hm (s) and the generator model Wm (s) from the gas turbine dynamic characteristic H (s) and the generator dynamic characteristic W (s) in the actual plant 5, and the fuel flow rate. Is a model of the relationship between the rotational speed Ng of the gas turbine and the output P of the generator.
[0020]
The distribution rate adjustment logic 2 includes an α change rule 21, an auxiliary fuel distribution coefficient 22, a main fuel distribution coefficient 23, a β change rule 24, and a heat generation amount adjustment coefficient 25. The α change rule 21 and the β change rule 24 are signals ERR from the input changeover switch 4, that is, the difference between the model rotational speed Ngm in the reference model 1 and the actual rotational speed Ng, or the model output Pm in the reference model 1 and the actual The values of α and β are calculated from the difference from the output P. Α is the auxiliary fuel distribution coefficient 22, 2-α is the main fuel distribution coefficient 23, β is the heat generation amount adjustment coefficient 25, and the distribution ratio of the main fuel flow rate 26 and the auxiliary fuel flow rate 27 is adjusted by these values.
[0021]
The proportional gain 3 includes a main fuel gain 31 and an auxiliary fuel gain 32. The difference (Ngref−Ng) between the required rotation speed Ngref and the actual rotation speed Ng is multiplied by the main fuel gain 31 and the auxiliary fuel gain 32. Based on the respective values obtained as a result, the main fuel flow rate 26 and the auxiliary fuel flow rate 27 are controlled.
[0022]
The input changeover switch 4 uses the signal ERR input to the distribution ratio adjustment logic 2 as a signal indicating the difference between the model rotational speed Ngm in the reference model 1 and the actual rotational speed Ng, or the model output Pm in the reference model 1 and the actual output. The signal is switched to one of the difference signals from P. That is, when the circuit breaker of the gas turbine generator is ON, a signal of the difference between the model output Pm in the reference model 1 and the actual output P is input to the distribution ratio adjustment logic 2 as the input signal ERR, and the gas turbine generator When the circuit breaker is OFF, a signal indicating the difference between the model rotation speed Ngm in the reference model 1 and the actual rotation speed Ng is input to the distribution ratio adjustment logic 2 as the input signal ERR.
[0023]
The actual plant 5 includes a gas turbine and a generator coupled to the gas turbine shaft, and main gas and auxiliary fuel are supplied to the gas turbine. In FIG. 1, the dynamic characteristic of the gas turbine is represented by H (s), and the dynamic characteristic of the generator is represented by W (s). Since the main fuel fluctuates in calorific value, in order to multiply the main fuel flow rate 26 by the calorific value variation coefficient 53, a multiplier 54 is provided on the diagram to express the calorific value change of the main fuel. The value obtained by multiplying the main fuel flow rate 26 by the calorific value variation coefficient 53 and the auxiliary fuel flow rate 27 are added and used as the input value of the gas turbine dynamic characteristic H (s).
[0024]
Next, the operation of the control system in the present embodiment will be described.
[0025]
FIG. 2 shows the relationship between the control device 61 and the gas turbine 51 and generator 52 to be controlled.
[0026]
During the gas turbine no-load operation, that is, in a state where the circuit breaker 62 is OFF and the generator 52 is not juxtaposed to the system, the requested rotation speed Ngref and the rotation speed Ng are input to the control device 61. The control device controls the main fuel flow rate 26 and the auxiliary fuel flow rate 27 so that the fuel flow rate is proportional to the difference (Ngref−Ng).
[0027]
At the time of gas turbine load operation, that is, when the circuit breaker 62 is ON and the generator 52 is inserted into the system, the rotational speed Ng is determined by the power supply frequency on the system side. Regardless of the increase or decrease of 27, the rotational speed Ng is constant. Therefore, in this case, the control device 61 controls the output of the generator 52 by increasing or decreasing the main fuel flow rate 26 and the auxiliary fuel flow rate 27. At this time, the difference (Ngref−Ng) between the requested rotational speed Ngref and the rotational speed Ng becomes an output request signal. Note that switching between the rotational speed control and the output control is performed by a circuit breaker state signal CB.
[0028]
Here, the control device 61 includes the reference model 1 as shown in FIG. In the reference model 1, Wfm obtained by multiplying the difference (Ngref−Ng) between the required rotational speed Ngref and the actual rotational speed Ng by the main fuel gain 31 and adding the no-load steady fuel value Wfss1, and the auxiliary A value obtained by adding two values Wfa obtained by multiplying the fuel gain 32 and adding the no-load steady fuel value Wfss2 is input. At this time, Wfm corresponds to the main fuel flow rate input to the reference model 1, and Wfa corresponds to the auxiliary fuel flow rate input to the reference model 1.
[0029]
The reference model 1 creates a gas turbine model Hm (s) and a generator model Wm (s) from the gas turbine dynamic characteristic H (s) and the generator dynamic characteristic W (s) in the actual plant 5, and the gas turbine with respect to the fuel flow rate. The relationship between the rotational speed Ng and the generator output P is modeled. Therefore, if the calorific values of the main fuel and the auxiliary fuel do not change, the change in the model rotational speed Ngm output from the reference model 1 when the required rotational speed Ngref is increased or decreased without the distribution rate adjustment logic 2. And the actual change in the rotational speed Ng coincide with each other. Furthermore, even when the required output value is increased or decreased by increasing or decreasing the required rotational speed Ngref in the state where the circuit breaker 62 is turned on and inserted in the system, the change in the model output Pm output from the reference model 1 and the actual output This is consistent with the change in P.
[0030]
However, since the amount of heat generated by the main fuel changes, the main fuel flow rate and the auxiliary fuel flow rate do not change. Therefore, the values of Wfm and Wfa are kept constant, and the model rotational speed Ngm or the model output Pm is a constant value. However, the actual rotational speed Ng or the actual output P changes according to the change in the heat generation amount of the main fuel. That is, when the calorific value of the main fuel changes, the change in the model rotational speed Ngm or model output Pm output from the reference model 1 does not match the actual actual rotational speed Ng or output P.
[0031]
The distribution rate adjustment logic 2 is configured when the change in the model rotation speed Ngm or the model output Pm does not coincide with the actual change in the rotation speed Ng or the output P due to the change in the heat generation amount of the main fuel. By adjusting the distribution ratio between the main fuel flow rate 26 and the auxiliary fuel flow rate 27, the value obtained from the reference model 1 and the value in the actual plant 5 are matched.
[0032]
On the other hand, during no-load operation of the gas turbine, that is, in a state where the circuit breaker 62 is OFF and the generator 52 is not juxtaposed to the system, the output of the gas turbine is zero, so the model rotation speed in the reference model 1 It is necessary to input the difference between Ngm and the actual rotational speed Ng to the distribution ratio adjustment logic 2, and when the gas turbine load is operated, that is, the circuit breaker 62 is turned on and the generator 52 is inserted in the system. Then, since the rotation speed Ng is determined by the power supply frequency on the system side, it is necessary to input the difference between the model output Pm in the reference model 1 and the actual output P to the distribution ratio adjustment logic 2.
[0033]
The input changeover switch 4 switches a signal input to the distribution ratio adjustment logic 2 in accordance with ON / OFF of the circuit breaker 62.
[0034]
FIG. 3 shows the distribution rate adjustment logic 2 extracted from FIG.
[0035]
First, the distribution rate adjustment logic 2 takes in the difference ERR between the model rotational speed Ngm in the reference model 1 and the actual rotational speed Ng as an error ERR during no-load operation, and the model output Pm and actual output in the reference model 1 during load operation. The difference from P is taken as an error ERR.
[0036]
Next, the fuel distribution coefficient is adjusted according to the α change rule.
[0037]
The α change rule is as follows.
[0038]
α = α × (1 / (1 + ERR / n)) (1)
Here, ERR = Ngm-Ng (2) (No load operation)
ERR = Pm-P (3) (During load operation)
n is a positive integer of 1 or more and is called an adjustment coefficient. (The larger n is, the slower the adjustment progresses.)
α takes a value in the range of 0 <α <2, this value is the auxiliary fuel distribution coefficient, and 2-α is the main fuel distribution coefficient. Therefore, the sum of the auxiliary fuel distribution coefficient and the main fuel distribution coefficient is 1.
[0039]
Furthermore, since the total heat quantity of the fuel supplied to the gas turbine increases or decreases only by changing the distribution rate as it is, the calorific value adjustment coefficient β is calculated according to the following rule according to the β change rule.
[0040]
β = β × (1 / (1-ERR / n)) (4)
Here, ERR = Ngm-Ng (5) (No load operation)
ERR = Pm−P (6) (During load operation)
n is a positive integer of 1 or more and is called an adjustment coefficient. (The larger n is, the slower the adjustment progresses.)
Of the signals Wfm and Wfa input to the distribution rate adjustment logic 2 for controlling the fuel flow rate, a value obtained by multiplying Wfa by the auxiliary fuel distribution coefficient α is the auxiliary fuel flow rate 27. (In actuality, this is the set value of the auxiliary fuel control device, but the control loop is incorporated in the auxiliary fuel control device, and the set value of the auxiliary fuel control device and the auxiliary fuel flow rate are controlled to coincide. Therefore, for the sake of simplicity, here, the set value is read as it is as it is. The same applies to the main fuel flow rate 26. In addition, Wfm is multiplied by the main fuel distribution coefficient (2-α) to further adjust the heat generation amount. A value obtained by multiplying the coefficient β is the main fuel flow rate 26.
[0041]
For example, it is assumed that the output P of the gas turbine has decreased by 2% because the heat generation amount of the main fuel has decreased in the state where the initial value α = 2−α = β = 1 during the load operation of the gas turbine. At this time, since ERR = 0.02, when the adjustment coefficient n = 1, the auxiliary fuel distribution coefficient α, the main fuel distribution coefficient (2-α), and the heat generation amount adjustment coefficient β are expressed by the equations (1), (4). 0.98, 1.02, and 1.02, respectively, and the auxiliary fuel flow rate 27 decreases. However, the main fuel flow rate 26 increases as the heat generation amount of the main fuel decreases, and the auxiliary fuel flow rate 27 increases accordingly. Decrease.
[0042]
Such correction operation of the values of α and β is repeated until ERR becomes zero. At this time, the larger the value of the adjustment coefficient n, the more slowly the correction operation of the values of α and β is advanced.
[0043]
In the present embodiment, in order to use as much main fuel as possible, the α change rule 21 and the β change rule 24 are defined as in equations (1) and (4). Even with expressions other than Expressions (1) and (4), the change rule is such that when ERR is positive, α decreases and β increases, and when ERR is negative, α increases and β decreases. As shown in FIG. 4, the main fuel distribution coefficient and the auxiliary fuel distribution coefficient may be α1 and α2, respectively, and may be corrected according to different change rules. However, even in this case, in order to use as much main fuel as possible, α1 increases when α is positive, α2 decreases, α1 decreases when α is negative, α1 increases and α2 increases. -It is necessary to use the α2 change rule 21a. Conversely, in order to use as much auxiliary fuel as possible, the change rule is such that α1 is decreased when α is positive, α2 is increased, α1 is increased when ERR is negative, and α2 is decreased. There is a need. Alternatively, α1 and α2 may be fixed to 1 regardless of the value of ERR, and only the heat generation amount adjustment coefficient β may be corrected according to the value of ERR.
[0044]
Next, an example in which simulation is performed by the present control system is shown.
[0045]
FIG. 5 shows the response of the rotational speed Ng in the case of a conventional control device, that is, a system without the reference model 1 and the distribution ratio adjustment logic 2 when the 10% main fuel heat generation amount rises rapidly during no-load operation. FIG. 6 shows the response of the rotational speed Ng when this control system is applied when the 10% main fuel calorific value suddenly rises during no-load operation, and FIG. 7 shows the 2% main fuel calorific value suddenly rises during 500 kW load operation. FIG. 8 shows the response of the output P when the present control system is applied when the 2% main fuel calorific value suddenly drops during 500 kW load operation. .
[0046]
As shown in FIG. 5, an offset occurs when a conventional control device is applied, but as shown in FIGS. 6 to 8, the offset disappears in the present embodiment. In either case, the set value is converged within 10 seconds.
[0047]
Thus, according to the present embodiment, when the gas turbine is not juxtaposed to the system , the gas turbine is integrated into the system based on the difference between the model rotational speed of the gas turbine and the actual rotational speed of the gas turbine. In the juxtaposed state, if it is determined that the calorific value of the main fuel has fluctuated based on the difference between the model output of the gas turbine and the actual output of the gas turbine, the model rotational speed of the gas turbine and the actual gas turbine The main fuel flow rate 26 and the distribution ratio of the auxiliary fuel flow rate 27 and the main fuel flow rate 26 are adjusted so that the rotational speeds of the main fuel flow rate 26 and the gas turbine model output match the actual output of the gas turbine. Even when the calorific value of the fuel fluctuates drastically in a short period of time, an appropriate fuel distribution ratio can be maintained according to the calorific value of the main fuel. Therefore, stable control is possible for gas turbine power generation facilities that use fermented methane gas, etc., whose calorific value fluctuates dramatically in a short period of time, and also uses kerosene, natural gas, etc., which have a stable calorific value, as auxiliary fuel. It becomes possible.
[0048]
【The invention's effect】
As described above, the gas turbine control system according to the present invention is based on the difference between the model rotational speed of the gas turbine and the actual rotational speed of the gas turbine when the gas turbine is not installed in the system. In the state where the gas turbine is installed in the system, the model rotation of the gas turbine is performed when it is determined that the calorific value of the main fuel fluctuates based on the difference between the model output of the gas turbine and the actual output of the gas turbine. Since the main fuel flow rate and the auxiliary fuel flow rate distribution ratio and the main fuel flow rate are adjusted so that the actual number of rotations of the gas turbine and the actual output of the gas turbine match, or the model output of the gas turbine and the actual output of the gas turbine match. A gas tank that uses a main fuel such as fermented methane gas whose calorific value fluctuates rapidly in a short period of time and an auxiliary fuel such as kerosene or natural gas that has a stable calorific value. Thus enabling stable control over the bottle power generation facilities.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of a gas turbine control system according to the present invention.
FIG. 2 is a configuration diagram showing a relationship between a gas turbine and a generator of a control device in the system of FIG.
FIG. 3 is a diagram in which distribution rate adjustment logic is extracted from the system of FIG. 1;
FIG. 4 is a diagram showing a modification of the distribution rate adjustment logic in the system of FIG. 1;
FIG. 5 is a simulation result in a conventional control system.
FIG. 6 is a simulation result when the main fuel calorific value rapidly rises by 10% during no-load operation.
FIG. 7 is a simulation result when a main fuel heating value rapidly increases by 10% during a 500 kW load operation.
FIG. 8 is a simulation result when the main fuel heating value suddenly drops by 10% during a 500 kW load operation.
FIG. 9 is a configuration diagram of a conventional example.
[Explanation of symbols]
1 Reference Model 2 Distribution Ratio Adjustment Logic 3 Proportional Gain 4 Input Changeover Switch 5 Actual Plant

Claims (1)

The control target is a gas turbine that uses a main fuel with a variable calorific value and an auxiliary fuel with a constant calorific value, and the flow rate of the main fuel supplied to the gas turbine, the flow rate of the auxiliary fuel, and the distribution ratio thereof. In a gas turbine control system for controlling
A reference model for calculating a model rotational speed and a model output of the gas turbine based on the flow rate of the main fuel and the flow rate of the auxiliary fuel;
When it is determined that the calorific value of the main fuel fluctuates based on the difference between the model rotational speed of the gas turbine and the actual rotational speed of the gas turbine in a state where the gas turbine is not juxtaposed in the system, thereby adjusting the flow rate of the distribution ratio and the main fuel of the main fuel and the auxiliary fuel turbine model speed and the actual rotational speed of said gas turbine Let 's that matches the gas turbine NamiIri lineage When it is determined that the calorific value of the main fuel has fluctuated based on the difference between the model output of the gas turbine and the actual output of the gas turbine, the model output of the gas turbine and the actual output of the gas turbine And a distribution ratio adjusting means for adjusting a distribution ratio of the main fuel and the auxiliary fuel and a flow rate of the main fuel so that the output of the main fuel and the auxiliary fuel coincide with each other. -Bin control system.

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