JPH01310107A - Revolution speed control unit for steam turbine - Google Patents

Abstract

PURPOSE:To control the turbine revolution speed just as an aimed value by computing a compensation value according to a degree of steam temperature, and performing compensation for a valve lift command value based on the compensation value. CONSTITUTION:A steam temperature compensating means 27 that inputs steam temperature T between a steam pressure compensating means 17 and an adding element 18 for computing a steam temperature compensation value KT in accordance with the degree of temperature, inputs Kp.L1 computed on a steam pressure compensating means 17 for performing compensation based on the steam temperature compensation value KT, outputs a valve lift command value LT= Kp.KT.L1 being the result of the compensation to the adding element 18, is provided. Thereby, even in a case of broad change in steam temperature, a proper valve lift command value can be obtained, therefore the turbine revolution speed can be controlled just as the aimed value.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a steam turbine rotation speed control system.

In particular, the present invention relates to a steam turbine rotation speed control device that optimally compensates a valve lift command value based on steam temperature.

(Prior Art) FIG. 1 shows an example of a turbine configuration used in a power generation plant. To control the rotation speed of the turbine, as shown in FIG. It is done by doing. In other words,
The rotation speed of the steam turbine is controlled by controlling the valve opening degree using a motor drive signal m given to the drive motor M. Further, the output of the motor drive signal m is compensated by the steam pressure P. The control valve 1 is usually a main steam stop valve bypass valve or a steam control valve, and the main steam supplied from the steam generator via the control valve 1 is transferred to the high pressure turbine 2.
, to an intermediate pressure turbine 3 and a low pressure turbine 4, and drive a generator 5 connected to these turbines to generate electric power. Note that a reheater 6 is provided between the high pressure turbine and the intermediate pressure turbine.

The steam temperature T has been used as a determining factor for the turbine startup schedule, and has not been treated as a determining factor for controlling the rotation speed of the steam turbine.

FIG. 2 is a block diagram of the rotation speed control of the turbine shown in FIG. 1. A turbine acceleration rate command value α is stored in the first valve lift command value setting means 11 of the steam turbine rotation speed control bag @C.

is input and its acceleration command value α.

A valve lift command value Li corresponding to the acceleration torque is calculated. Further, a target value NI of the turbine rotation speed is input to the second valve lift command value setting means 12, and the target value N1 is inputted to the second valve lift command value setting means 12.
A valve lift command value R corresponding to the torque loss is calculated according to the value of l. A target value N0 of the turbine rotation speed and a main feedback amount H2·N of the actual turbine rotation speed N via the main feedback element 14 are input to the first addition element 13. Then, the deviation is input to the rotation speed control element 15 and subjected to a predetermined calculation to obtain a valve lift command value. is calculated. second addition element 1
6 contains a valve lift command value for acceleration torque, a valve lift command value LR for loss torque, and a valve lift command value for rotation speed deviation. is input, and the valve lift command value L1 is the sum of these values.
is calculated. In the steam pressure compensating means 17, ρ is calculated as a steam pressure compensation value based on the steam pressure P, and the valve lift command value L is inputted to calculate the valve lift command value Kp −L after steam pressure compensation is performed. . Third addition element 18
P”LL is the valve lift command value with steam pressure compensation applied.
and the sub-feedback amount of the actual lift scale via the sub-feedback element 19 +
1.・L is input, and its deviation L2 is obtained here. Based on this deviation L2, the drive motor control element 20 outputs a motor drive signal m to be applied to the drive motor M.

The motor drive signal m is input to the drive motor M, and its characteristic is an integral characteristic as shown in block 21.

That is, T1 is the integral time constant of the drive motor M. Note that S is a Laplace operator.

When the drive motor M is driven, the actual valve lift of the control valve 1 changes, so that the high pressure turbine 2. The steam flow flowing into the intermediate pressure turbine 3 changes, and its torque also changes. The block 22 shows the torque characteristics of the high pressure turbine 2,
fo is its torque coefficient. Furthermore, the steam flow that has finished its work in the high-pressure turbine 2 and is reheated in the reheater 6 flows into the intermediate-pressure turbine 3 . The torque characteristics in that case are shown in block 23. TR is a delay time constant of the reheater 6.

Note that when the steam flow rate is small, such as when the turbine is speeding up, the torque generated by the low-pressure turbine 4 is small, so this is ignored in FIG. 2.

Since the torque of the entire turbine is the sum of the respective torques of the high-pressure turbine 2 and the intermediate-pressure turbine 3, it is obtained by the fourth addition element 24. Then, a torque loss such as windage loss 2 mechanical loss is subtracted from this by a fifth addition element 25, and the resultant torque gives the rotational force to the turbine. Block 26
shows its characteristics, and T4 shows the inertia of the turbine rotor.

(Problems to be Solved by the Invention) As described above, in conventional steam turbine rotation speed control, changes in the steam flow flowing into the turbine through the control valve 1 due to differences in steam conditions are dealt with. The valve lift command value is calculated using the steam pressure P, which shows a change almost proportional to the change in . However, there was no compensation for differences in generated torque due to differences in steam temperature. For this reason, when the steam temperature changes, the optimum valve lift command value cannot be obtained, which often results in poor controllability. FIG. 3 shows the rotation speed control characteristics when the rotation speed of a turbine under low temperature steam conditions is controlled using a control system adjusted under high temperature steam conditions.

Here, it is assumed that the evaporation pressure compensation value Kp is 1. Since the torque generated under low-temperature steam conditions is smaller than the torque generated under high-temperature steam conditions, the valve lift command value Li for acceleration torque and the valve lift command value for loss torque are calculated as shown in the figure. LR is running low. Therefore, at the beginning of the turbine speed increase (between times t and t2), the rotation speed deviation increases due to the operation delay, and accordingly, the valve lift command value, which is the output of the rotation speed control element 15, increases. will also change significantly. Similarly, the valve lift command value L1 calculated by the second addition element 16 changes greatly. In particular, when the rotational speed control element 15 has an integral element, the valve lift command value L1 rises with a delay with respect to the deviation and overshoots as shown in the characteristic curve LA. Further, when the turbine rotational speed N is to be maintained at a constant value at time t3, the valve lift command value L1 falls behind and undershoots as shown by the characteristic curve LB. Therefore, the target value N of the rotation speed N. The tracking performance becomes worse.

[Structure of the invention]

(Means for Solving the Problem) In order to achieve this object, the present invention inputs the steam temperature and calculates a compensation value based on its height, inputs a valve lift command value, and then calculates the compensation value based on the compensation value calculated above. Steam temperature compensation means is provided to compensate for differences in generated torque due to differences in steam temperature.

(Function) As a result, the turbine rotational speed can be appropriately controlled even under conditions of different steam temperatures.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 4 shows a control block diagram in which the rotational speed control device C of the present invention is applied to a steam turbine, and as is clear from the figure, it is characterized in that a steam temperature compensating means 27 is provided. Items 11 to 26 are similar to those shown in FIG. 2, so their explanation will be omitted.

The steam temperature compensation means 27 inputs the steam temperature T, calculates the steam temperature compensation value according to its height, inputs Kp-Ll calculated by the steam pressure compensation element 17, and calculates the steam temperature compensation value exactly. -KT-L□ is output to the third addition element 18 for the valve lift command value LT= which is the result.

FIG. 5 is a characteristic diagram for explaining the operation of the steam turbine rotation speed control device C of the present invention shown in FIG. 4. Here, it is assumed that the steam pressure compensation value KP is 1. Now, as shown in the figure, the rotation speed N changes from zero. Turbine rotation speed N changes at a predetermined rate of change α up to □. Suppose that is given. In this case, the target value N of the turbine rotation speed is from time t1 to time t3. changes at a predetermined rate of change α, so the value corresponding to this rate of change α is the acceleration rate command value α. is input into the first valve lift command value setting means 11, and the valve lift command value corresponding to the acceleration torque is input to the second addition element 1.
6 is output. On the other hand, the second valve lift command value setting means 12 stores a target value N of the turbine rotation speed. is given, and the valve lift command value corresponding to the loss torque corresponding to the change is the second value.
is output to the addition element 16. As a result, the output 1 from the second addition element 16 is the valve lift command value Ll-1-L.
It becomes R. Here, it is assumed that the steam pressure compensation value Kp is 1, so the steam temperature compensation means 27 has a second addition element 1.
The output 1 from 6, that is, LiLR, is input as is. The steam temperature compensation means 27 calculates a steam temperature compensation value KT for the input valve lift command value +LR.
As a result, LT=KT
-L, that is, KT·t, i+KT−t, and R are output. Here KT-guchi is L sumo wrestler (KT 1)・L no t
KT' LR can be expressed as LR+(KT 1 )·LR. In other words, the steam temperature compensation (KT
1).Ll and (Kt l).LR are added and output.

Then, at time t2, when acceleration of the turbine is no longer required, the valve lift command value port corresponding to the acceleration torque is no longer necessary, so the output from the first valve lift command value setting means 11 becomes zero, and the output from the second valve lift command value setting means 11 becomes zero. The output □ from the addition element 16 is only the valve lift command value LR corresponding to the loss torque. Ll, that is, LR, is input to the steam temperature compensation means 27, and compensation is performed based on the steam temperature compensation value KT, and LT=KT-L.
R is output.

KT-LR can be expressed as LR+ (KT 1 )·LR. In other words, the steam temperature compensation amount (KT 1) is added to the output LR of the second valve lift command value setting means 12.
・LR will be added and output.

Here, if the valve lift command value LT output from the steam temperature compensator 27 is accurately compensated, the turbine rotational speed N will be equal to its target value N0.

Even if there is a slight error in the valve lift command value LT, the target value N is stored in the second addition element 16. Since the valve lift command value L6 from the rotation speed control element 15 for compensating for the deviation between the main feedback amount (turbine rotation speed N) and the main feedback amount (turbine rotation speed N) is input,
Turbine rotation speed N is properly its target value N. controlled to match. In other words, the re-bin rotation speed N and the target value N
. Even if a deviation occurs, the deviation is based on an error in the steam temperature compensated valve lift command value LT and is very small, so overshoot or undershoot will not occur as in the conventional case. There isn't.

FIG. 6 is a flowchart showing the method of calculating the value of steam temperature compensation value. First, the process starts at step 31, and at step 32, the steam temperature T is input. In step 33, it is determined whether the steam temperature T input in step 32 is normal.
If affirmative, the process proceeds to step 34, where a steam temperature compensation value KT is calculated based on the steam temperature T, and the process proceeds to the end of step 35. If step 33 is negative, proceed to step 35 K
After setting T to 1, the process proceeds to step 36, the end. As shown in the figure, the steam temperature compensation value is calculated using a linear equation for the steam temperature since a change in the generated torque is approximately proportional to a change in the steam temperature.

〔Effect of the invention〕

As described above, according to the present invention, even if the steam temperature changes significantly, an appropriate valve lift command value can be obtained by performing temperature compensation, so that the turbine rotation speed can be maintained at the target value. can be controlled.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the turbine configuration, FIG. 2 is a conventional block diagram of a steam turbine, FIG. 3 is a conventional control characteristic diagram of a steam turbine, and FIG. 4 is a control block diagram of the present invention for a steam turbine. FIG. 5 is a control characteristic diagram of a steam turbine according to the present invention, and FIG. 6 is a flowchart showing a method of calculating a steam temperature compensation value. 1... Control valve 2... High pressure turbine 3.
...Intermediate pressure turbine 4...Low pressure turbine 5...
Generator 6... Reheater agent Patent attorney Nori Ken Chika Yudo Ken Daishimaru 1 Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] Calculating a valve lift command value for a control valve for regulating steam flowing into the steam turbine according to a deviation between the rotation speed of the steam turbine and its target value, and compensating the valve lift command value using the pressure of the steam. and controls the rotation speed of the steam turbine to follow the target value by driving the drive motor of the control valve based on the compensated valve lift command value, in which the temperature of the steam is detected and the temperature is adjusted. A steam turbine rotation speed control device comprising steam temperature compensating means for compensating the valve lift command value by calculating a compensation value based on the height.