JPH046302A - Steam temperature control device - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of steam temperature according to the fluctuation of a demand load signal by using a steam temperature control device for a supercritical pressure boiler plant by providing a PID regulator, a compensator to input a demand load signal and effect specified compensation, and an adder to add a proportional gain and an output from the compensator and send a result to an integrator with a gain. CONSTITUTION:A proportional gain, an integrator with a gain, and a differentiator with a gain, which a PID regulator comprises, are separated away from from each other. An adder is disposed between the proportional gain and an integrator with a gain. The adder has one of transmission functions G of G(s) = -K[(1+a1s/(1+b, s)].S, G(s) = -K[(1+a1s+a2s<2>)/(1+b, s+b2s<2>)].S, and G(s) = -K[(1+a1s+a2s<2>+a3s<3>/(1+b1s+b2s<2>+b3s<3>)].S', wherein (s) is a plus operator, K, a1 - a3, b1 - b3 are a constant. An output from a compensator to input a demand load signal and an output from the propor tional gain are added together by the adder. The adding result is provided to the integrator with a gain.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steam temperature control device for controlling steam temperature in a supercritical pressure boiler plant.

[Prior Art] Conventionally, a steam temperature control device for controlling the steam temperature of a supercritical pressure boiler plant has a configuration as shown in FIG. That is, in the same figure, 1 is the water supply 1, and this water supply 1 is the energy saver (ECO) 2 and the water allergy (WW).
3. It becomes steam via the first heater (SHI) 4, heating reducer 5, and second heater (SH2) 6, and is supplied to the governor valve 7. The steam turbine 8 is driven by the steam that has passed through the governor valve 7, and a generator connected to the steam turbine 8 generates electricity.

Therefore, the heater steam temperature control system detects the power generation amount of the generator 9 with the power generation amount detector (MW) 10, and the subtractor 1
1, the comparison output is sent to the PID controller 12 to operate the governor valve 7, and a steam temperature detector (T) detects the outlet steam temperature of the second heater 6. 1
3, and the subtractor I4 sets the steam temperature target value (Set) 1.
5 and sends the comparative output to the PID controller 16 to operate the fuel valve 17, and the temperature difference between the inlet and outlet of the heating attenuator 5 is detected by a temperature difference detector (ΔT) 18 and subtracted. The output of the comparison is multiplied by a coefficient in the coefficient unit (Kp') 21, and then compared and subtracted with the output of the subtractor 19 in the subtracter 22, and the difference output is It is composed of three control systems, including a third system that sends the water to the PID regulator 23 and operates the spray valve 24.

The PID controller 23 includes a proportional gain (Kp) 31, an integrator with gain (1/T, 5) 32, and a differentiator with gain (T
DS) 33 and an adder 34.

[Problems to be Solved by the Invention] In the above configuration, the rate of change of the requested load signal W is large, and when a large change is requested by this requested load signal W, the steam temperature also fluctuates greatly. Therefore, there is a problem that the life of the steam turbine is shortened.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a steam temperature control device that does not cause the steam temperature to fluctuate even if the required load signal fluctuates.

[Means and effects for solving the problem] That is, the present invention sets the main operation amount of the heater outlet steam temperature control to be the fuel amount,
In a steam temperature control device consisting of a system in which the spray amount is used as the sub-operation amount, and a system in which the temperature difference between the inlet and outlet of the heating attenuator is controlled by the spray amount, a proportional gain, an integrator with a gain, and an integrator with a gain that constitute a PID regulator are used. Separate the differentiator,
An adder is disposed between the proportional gain and the integrator with gain, and the transfer function G of equations (1) to (3) shown below is
(s), the output of the compensator inputting the required load signal and the output of the proportional gain are added by this adder, and the addition result is derived to the integrator with gain. The compensator has a transfer characteristic G (s) that changes in the opposite direction when the required load signal fluctuates greatly, canceling out fluctuations in the input of the integrator with gain. The steam temperature does not fluctuate even when the temperature fluctuates.

(However, S nila plus operator, K, at ~a,, b+ ~ba: constant.) [Example] An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows its configuration, and since it is basically the same as that shown in FIG. 2 above, the same parts are given the same reference numerals and the explanation thereof will be omitted.

Therefore, on the input side of the integrator with gain 32, the proportional gain 3
1, and an adder 43 that can add the characteristic test input signal 42 to the control system of the 24 spray valve systems. The adder 41 has a proportional gain of 3J.
In addition, a compensator (G(s)) that inputs the required load signal W
The output of 44 is input, and the added output thereof is sent to the integrator 32 with gain.

The compensator 44 approximates the transfer characteristic Gw(s) (s is a Laplace operator) of the required load signal W and the output y of the steam temperature detector 13 using a dead time and a rational function, and also uses an input signal for characteristic testing. By similarly approximating the transfer characteristic Gu (s) of 42(u) and the output y of the steam temperature detector 13 using a dead time and a rational function, the inverse transfer characteristic G (s) is obtained. It is. That is, the above transfer functions GW (S), GLI (S)
(However, S: Laplace operator, K, a, ~a3.bl ~b3: constant a.), and has one of these formulas (1) to (3).

In order to make the compensator 44 satisfy the above equation (1), the above transfer function Gw (s) Gu (s) must be.

Furthermore, in order to obtain the compensator 44 that satisfies the above equation (3), the transfer functions Gw*(s) and Gu*(s) must be expressed as follows. At this time, K − (Kw−T i) /Ku −=
(6).

Further, it must be done so that the compensator 44 satisfies the above equation (2).

The relationship between the requested load signal W and the transfer function Gw (s) of the output y of the steam temperature detector 13 is y−Gw (s) w −=(
The relationship 11) holds true.

Then, the characteristic test input signal 42. (u) and the transfer function Gu (s) of the output y of the steam temperature detector 13 is y−Gu (s) u
-112) holds true. Therefore, y of W and U
Adding the influence on y-Gw (s) w 10 Gu
(s) u −=(13), and U that cancels the movement of y due to the change in W is given by the above (12)
The formula should be set to y-0, and from this, u - (-Gw (s) /Gu (s) )
w...(14) The following formula is obtained.

Next, in order to transfer the addition point of U to the adder 41, the above (14
) by multiplying the formula by Ti-5, we get Ti・s”u (-Gw (s)/Gu (s)) Ti・s−w・
...(15) The value on the left side of equation (15) becomes the equivalent value obtained by moving the addition point. Therefore, compensator 44
By giving the characteristic of equation (15) above, the movement of y due to the fluctuation of W can be canceled out and eliminated. However, to be precise, the points mentioned above are Gw (s
) and Gu (s) can be approximated with high accuracy; in reality, approximation errors are involved, so y will vary by the amount of the error. However, this variation in y is very small compared to the conventional one, and can be reduced to a level that does not pose a practical problem.

The reason why the addition point was moved from the adder 43 to the adder 41 is because if the adder 43 adds the value to the output side of the PID controller 23, U can be found using the above equation (14). In general, W will have a certain value other than "0",
If the gain of r-Gw (s) /Gu (s) j is large, it will exceed the control range, so
This was done to avoid this.

[Effects of the Invention] As detailed above, according to the present invention, there is provided a system in which the main manipulated variable for heater outlet steam temperature control is the fuel amount and the secondary manipulated variable is the spray amount, and the temperature difference control at the inlet and outlet of the heating attenuator. In a steam temperature control system consisting of a system that controls the amount of spray,
The proportional gain, the integrator with gain, and the differentiator with gain that constitute the PID regulator are separated, and an adder is disposed between the proportional gain and the integrator with gain to calculate the output of the proportional gain and the transfer function G. (s), and the output of the compensator that inputs the requested load signal, is added by this adder, and the addition result is derived to the above-mentioned integrator with gain, so the requested load signal fluctuates greatly. The compensator has a transfer characteristic G (s) that fluctuates in the opposite direction when the load signal changes, and this cancels out fluctuations in the input of the integrator with gain. A steam temperature control device that does not fluctuate can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of a conventional steam temperature control device. DESCRIPTION OF SYMBOLS 1... Water supply, 2... Energy saver, 3... Water wool, 4... Heater, 5... Heating reducer, 6...
... Second heater, 7... Governor valve, 8... Steam turbine, 9... Generator, lO/power generation amount detector, 11.1
4.19.22...Subtractor, 12, 16.23...
・PID controller, 13... Steam temperature detector, 15...
・Steam temperature target value, 17...Fuel valve, 18...Temperature difference detector, 20...Temperature difference target value, 21...Coefficient unit,
24... Spray valve, 31... Proportional gain, 32...
...Integrator with gain, 33...Differentiator with gain, 34
．． 41.43...Adder, 42...Input signal for characteristic test, 44...Compensator. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] A steam system consisting of a system in which the main manipulated variable for heater outlet steam temperature control is the fuel amount and the secondary manipulated variable is the spray amount, and a system in which the temperature difference between the inlet and outlet of the heating attenuator is controlled by the spray amount. In the temperature control device, a PID regulator in which a proportional gain, an integrator with a gain, and a differentiator with a gain are separately configured, and a required load signal are input, and the transfer function G ( s), and the integrator with proportional gain and gain, and adds the output of the proportional gain and the output of the compensator, and adds the result of the addition to the above. A steam temperature control device characterized by comprising an adder that sends out data to an integrator with a gain. G(s)=-K{(1+a_1s)/(1+b_1s)
}・s...(1)G(s)=-K{(1+a_1s+a_
2S^2)/(1+b_1s+b_2s^2)}・s...
(2) G(s)=-K{(1+a_1s+a_2S^2
+a_3s^3)/(1+b_1s+b_2s^2+b
_3s^3)}・s...(3) (However, s: Laplace operator, K, a_1 to a_3, b_1 to b_3: constants.)