EP1319117A1

EP1319117A1 - Method for regulating a steam turbine, and corresponding steam turbine

Info

Publication number: EP1319117A1
Application number: EP01983470A
Authority: EP
Inventors: Heinrich Oeynhausen; Richard Steinborn; Heribert Werthes
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2000-09-20
Filing date: 2001-09-07
Publication date: 2003-06-18
Anticipated expiration: 2021-09-07
Also published as: EP1319117B1; DE50115502D1; CN1461374A; ES2344591T3; EP1191190A1; WO2002025067A1; CN100335751C; JP2004518050A; JP4695822B2

Abstract

The invention relates to a method for regulating a steam turbine (1), according to which steam is fed to the steam turbine (1) via at least three valves, whereby one of the valves is regulated as a regulating valve (9, 11), and at least two valves are controlled as control valves (13, 15).

Description

description

Process for controlling a steam turbine and steam turbine

The invention relates to a method for regulating a steam turbine, in which steam is fed to the steam turbine via at least three valves. The invention further relates to a steam turbine with a valve group for regulating the steam inlet.

A method for controlling a steam turbine emerges from the article "Practical design of speed and power regulators for steam turbines" by Johannes Dastych and Heinz Unbehauen, Martin Bennauer and Heribert Werthes, ATP 41 (1999), No. 5. A steam turbine is based on speed or power regulated. The control circuit for speed and power according to Figure 2 consists of function blocks such as speed / power controller (D- / LR), live steam control valve (FD-STV), interception control valve (AF-STV), steam generator (DE) and turbine (T) as well elementary blocks, such as Constant, ramp and

Jump function for the input signals. To provide electrical power, the turbo set is supplied with steam from a steam generator, the steam supply being regulated via control valves in such a way that the necessary power is available. The speed and the power are regulated via a common speed / power controller both for load operation with selectable statics and for regulating the speed when idling. The output signal of the speed / power controller acts on the live steam and interception control valves. Such a control of a steam turbine requires a very complex control circuit as well as control valves which allow a sufficiently fast control. So far, only hydraulically driven control valves for steam inlet control have been used, since a sufficiently rapid adjustment of the valve lift is only possible via such a hydraulic drive. ω ω r-υ r H ¹

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set a certain value of their valve lift. The maintenance of a control difference value of approximately zero is carried out by one, possibly also several, control valves. This means that at least two control valves can be replaced by much simpler control valves, which considerably simplifies the control circuit.

A) The control valves are preferably driven by an electric motor. An electric motor drive offers considerable cost advantages over an electro-hydraulic drive, for example. In addition, the risk of fire is reduced by the absence of hydraulic oil. By adopting the fine control by means of the control valve, the lower dynamic range of the electromotive drive is also sufficient for use in the control process.

B) Two control valves and two control valves are preferably used. Four valves are usually used in control processes in the steam turbine. According to the new control concept, one control valve with three

Control valves works together. With regard to improved availability, however, it is advantageous to use two control valves and two control valves.

C) The method is preferably designed when the steam turbine is consuming power so that the control valve first opens and one of the control valves opens when a predetermined first value of a controller output signal used for controlling the control valve is exceeded and when there is a positive control difference. The first value is more preferably approximately a quarter of the maximum controller output signal. The positive control difference indicates that the desired value for the power or the speed has not yet been reached.

D) It is further preferred if the second output value of the controller output signal is exceeded and if there is a positive the second control valve. The second value of the controller output signal is larger than the first value of the controller output signal. A further stage in power consumption is thus reached in which the third valve, namely the second control valve, is switched on. The second value of the controller output signal is more preferably approximately half the maximum value of the controller output signal.

E) Preferably, the second control valve opens when a third value of the controller output signal is exceeded and when there is a positive control difference. The third value of the controller output signal is above the value of the second value of the controller output signal. A further stage in the power consumption of the steam turbine is thus reached, in which the second control valve is activated. With a controller output signal of 100%, all valves are fully open.

F) Preferably, a closing speed of each of the

Control valves set depending on the size of the control difference. The control difference, as stated, indicates the difference between the setpoint and the actual value of the speed or the power of the steam turbine. If there is a large control difference, the control valves are moved into their target position at high speed. With a smaller control difference, a lower actuating speed is sufficient. For the electromotive drives, a frequency converter, in particular, can specify the setting direction for the control valves depending on the sign of the control difference.

The configurations according to points A to F can be combined with one another in any manner.

The object directed at a steam turbine is achieved according to the invention by specifying a steam turbine with a valve. tilgruppe for regulating the steam inlet, which valve group comprises a control valve and at least two control valves.

The advantages of such a steam turbine result from the above explanations regarding the advantages of the method for regulating a steam turbine.

The control valves preferably have an electric motor drive.

The invention is explained in more detail by way of example with reference to the drawing. They show schematically and not to scale:

1 shows a steam turbine plant,

2 shows a set of steam inlet valves with associated control circuit and

3 shows a characteristic curve for the steam inlet valves.

The same reference symbols have the same meaning in the different figures.

Figure 1 shows schematically a steam turbine system. A steam turbine 1 is supplied with steam from a steam generator 3 via the feed line 5. A valve group 7 is installed in the supply line 5. The valve group 7 comprises a first control valve 9 and a second control valve 11. The valve group 7 further comprises a first control valve 13 and a second control valve 15. The amount of steam introduced into the steam turbine 1 is regulated via the valve group 7. This takes place as a function of the power or speed desired for the steam turbine 1. This is explained in more detail with reference to FIGS. 2 and 3. Figure 2 shows the valve group 7 from Figure 1 with the associated control circuit. Depending on the actual value of the speed or power and the target value of the speed or power, a controller 21 generates a controller output signal identifying a control difference. The controller output signal is fed to a first servo amplifier 23 of the first control valve 9. The controller output signal is also fed to a second servo amplifier 27 of the second control valve 11. The controller output signal is also fed to a first frequency converter 25 of the first control valve 13. The controller output signal is also fed to a second frequency converter 29 of the second control valve 15. The control method is described in more detail with reference to FIG. 3.

FIG. 3 shows an example of the valve lift of each of the valves 9, 11, 13, 15 as a function of the controller output signal in a diagram. The information is shown in percent of the respective maximum value. The characteristic curve 9K indicates the course of the valve lift 33 of the first regulator valve 9 as a function of the regulator output signal 31. The characteristic curve 13K indicates the corresponding characteristic curve for the first control valve 13. The characteristic curve 11K indicates the corresponding characteristic curve for the second control valve 11. The characteristic curve 15K indicates the corresponding characteristic curve for the second control valve 15. The first control valve 9 opens in proportion to the size of the controller output signal 31. At a value of 22.5% of the controller output signal 31, the first control valve 13 opens. At a value of 47.5% of the controller output signal 31, the valve lift 33 is for the first control valve 9 and for the first control valve 13 at 100%. From this point on, the second control valve 11 opens. At a value of 72.5%, the second control valve 15 is finally switched on. At a value of 100% of the controller output signal 31, all valves 9, 11, 13, 15 are completely open. The first control valve 9 is used for starting, ramping up to the nominal speed and synchronization. The size of the control difference determines the opening speed of the control valves 13, 15 to a negative control difference. The size of the negative control difference determines the closing speed of the control valves. Because of the lower control dynamics of the control valves, which are driven by an electric motor in the example shown, the response value for a "closing" switching operation when the load is shed can be different for the control valves 9, 11 and the control valves 13, 15.

Claims

claims

1. Method for controlling a steam turbine (1), in which steam is fed to the steam turbine (1) via at least three valves (9, 11, 13, 15), one of the valves (9, 11) being regulated as a control valve and at least two valves (13, 15) are controlled as control valves.

2. The method according to claim 1, wherein the control valves (13, 15) are driven by an electric motor.

3. The method according to claim 1, in which two control valves (9, 11) and two control valves (13, 15) are used.

4. The method according to claim 1, in which for a power consumption of the steam turbine (1) first the control valve (9, 11) opens and when a predetermined first value of a controller output signal (9, 11) used for the control of the control valve (9, 11) is exceeded one of the control valves (13, 15) opens when there is a positive control difference.

5. The method according to claim 4 and 3, wherein the second control valve (11) opens when a second value of the controller output signal (31) is exceeded and when there is a positive control difference.

6. The method according to claim 4 and 3, in which the second control valve (15) opens when a third value of the controller output signal (31) is exceeded and when there is a positive control difference.

7. The method of claim 1, wherein a closing speed of each of the control valves (13, 15) is set depending on the size of the control difference.

8. Steam turbine (1) with a valve group (7) for regulating the steam inlet, which valve group (7) is a control valve

(9, 11) and at least two control valves (13, 15).

9. steam turbine (1) according to claim 8, wherein the control valves (13, 15) have an electric motor drive.