METHOD FOR COUPLING A STEAM TURBINE AND A GAS TURBINE AT A DESIRED DIFFERENTIAL ANGLE USING A SETPOINT ACCELERATION

Abstract

A method for coupling a rotating device, in particular a steam turbine, and a shaft device, in particular a gas turbine, having the following steps: detecting a differential angle between the shaft device and the rotating device; detecting a differential speed between the shaft device and the rotating device; predicting a coupling angle at which the rotating device and the shaft device would be coupled if the rotating device were accelerated with a known acceleration up to the start of the coupling-in; comparing the predicted coupling angle with a target coupling angle, and calculating therefrom a setpoint acceleration such that the predicted coupling angle matches the target coupling angle.

Claims

1. A method for coupling a rotating device and a shaft device, comprising: detecting a differential angle between the shaft device and rotational device; detecting a differential speed between the shaft device and rotational device; predicting a coupling angle at which the rotational device and shaft device would be coupled if the rotational device were accelerated with a known acceleration up to a start of a coupling process; comparing the predicted coupling angle with a target coupling angle and calculating therefrom a setpoint acceleration in such a way that the predicted coupling angle corresponds to the target coupling angle.

2. The method as claimed in claim 1, wherein the prediction is based on an assumption that the start of the coupling process takes place as soon as the rotational speed of the rotating device reaches the rotational speed of the shaft device or exceeds it by a selected value.

3. The method as claimed in claim 1, wherein the calculated setpoint acceleration serves as a value for the known acceleration.

4. The method as claimed in claim 1, wherein the rotational device is accelerated up to an output rotational speed which is below the rotational speed of the shaft device, with a selected acceleration independently of an aimed-at target coupling angle.

5. The method as claimed in claim 4, wherein the selected acceleration is constant.

6. The method as claimed in claim 3, wherein the prediction of the coupling angle is started when an output rotational speed is reached with a selected acceleration.

7. The method as claimed in claim 3, wherein an output rotational speed is approximately 0.5 Hz up to approximately 1.5 Hz below the rotational speed of the shaft device.

8. The method as claimed in claim 1, wherein during the calculation of the setpoint acceleration it is noted that during the coupling process the differential angle is changed by a coupling rotational angle.

9. The method as claimed in claim 1, wherein the setpoint acceleration is converted into a setpoint rotational speed which is transferred to a turbine control unit.

10. An arrangement having a shaft device, and a rotating device, having a clutch for coupling the shaft device and rotating device, comprising: a device for detecting a differential angle between the shaft device and rotating device; a device for detecting a differential speed between the shaft device and rotating device; a device for accelerating the rotating device with an acceleration value; a prediction module that predicts, from the detected differential angle, the detected differential speed and a known acceleration, a coupling angle which would occur if the rotating device were accelerated with the known acceleration up to a start of the coupling; and an acceleration module which compares the predicted coupling angle with a target coupling angle and calculates therefrom a setpoint acceleration such that the predicted coupling angle corresponds to the target coupling angle are present.

11. An arrangement comprising: a shaft device, a rotating device, and a clutch for coupling the shaft device to the rotating device; and a control unit designed to carry out a method as claimed in claim 1.

12. The arrangement as claimed in claim 10, wherein the detection of the differential angle is determined with a clock rate of approximately 4 ms up to approximately 20 ms or lower.

13. The method as claimed in claim 7, wherein the output rotational speed is approximately 0.9 Hz up to approximately 1.1 Hz below the rotational speed of the shaft device.

14. The method as claimed in claim 1, wherein the rotating device is a steam turbine and wherein the shaft device is a gas turbine.

15. The arrangement as claimed in claim 10, wherein the rotating device is a steam turbine and wherein the shaft device is a gas turbine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will be explained in more detail below on the basis of an exemplary embodiment and using figures, of which:

[0026] FIG. 1 shows a single-shaft system of a gas and steam power plant,

[0027] FIG. 2 shows the sequence of the prediction of the coupling angle and the control of the setpoint acceleration,

[0028] FIG. 3 shows the control of the setpoint acceleration and the interaction of the turbine control unit,

[0029] FIG. 4 shows a simulation of the measured differential angle and of the predicted coupling angle, and

[0030] FIG. 5 shows a simulation of the controlled acceleration.

DETAILED DESCRIPTION OF INVENTION

[0031] FIG. 1 shows the essential components, for the present invention, of a combined gas and steam power plant. The shaft 1 is to be considered an essential feature. A gas turbine 2 is attached to said shaft 1 and rotates therewith. In addition, a generator 3 which is driven by the gas turbine 2 can be seen.

[0032] The shaft 1 is interrupted by a clutch 4. The clutch 4 is embodied as a self-synchronizing clutch.

[0033] The steam turbine 5 is located in the part of the shaft 1 which adjoins the clutch 4. The clutch 3 therefore has the function of coupling the steam turbine 5 to the gas turbine 2. It is clear here that this is basically a clutch of the respective shaft parts of the shaft 1. However, since said shaft parts are fixedly connected to the gas turbine or the steam turbine, it is both factually correct, and backed up by a figurative illustration, for mention to be made of a coupling of the steam turbine 5 to the gas turbine 2.

[0034] FIG. 2 shows the profile of the prediction of the coupling angle and the control of the setpoint acceleration. A detected differential angle 7 between the gas turbine 2 and the steam turbine 5 and a detected differential speed 8 between the gas turbine 2 and steam turbine 5 are included in a prediction module 6. In addition, the setpoint acceleration 9 is included, and this will be returned to below.

[0035] In the prediction module 6 a coupling angle 10 is determined from the differential angle 7, the differential speed 8 and the setpoint acceleration 9, which coupling angle 10 would be obtained if the steam turbine 5 were accelerated with the setpoint acceleration 9 until the clutch 4 starts the coupling process. It is to be noted that owing to its design as a self-synchronizing clutch, owing to the design the clutch 4 starts the coupling process as soon as the rotational speed of the steam turbine 5 slightly exceeds the rotational speed of the gas turbine 2.

[0036] The predicted coupling angle 10 which results from the prediction is compared with a predefined target coupling angle 11. The setpoint acceleration 9 is determined in the acceleration module 12 from the difference between the predicted coupling angle 10 and the target coupling angle 11. As already mentioned, this setpoint acceleration 9 is transferred to the prediction module 6. Moreover, the setpoint acceleration 9 is transferred to an integrator 13. A setpoint rotational speed 14 of the steam turbine is determined in the integrator 13 from the setpoint acceleration 9 by integration of the setpoint acceleration 9 over time up to the start of the coupling process.

[0037] The setpoint rotational speed 14 is, as is apparent in FIG. 3, transferred to a turbine control unit 15. Such turbine control units are known from the prior art. For reasons of completeness, a brief presentation of the turbine control unit 15 will nevertheless be given. The turbine control unit can receive the setpoint rotational speed 14 and compare it with a measured steam turbine rotational speed 16. A setpoint position 18 of a steam turbine valve 19 is determined in the speed module 17 from the comparison of the setpoint rotational speed 14 with the steam turbine rotational speed 16.

[0038] The setpoint position 18 is compared with the detected steam turbine valve position 20. On the basis of this, a position module 21 determines how an adjustment unit 22 sets the steam turbine valve 19.

[0039] The presentation above makes it clear that the new coupling method using a setpoint acceleration can easily be integrated into existing control concepts.

[0040] The illustration is to be considered an abstract illustration of the steps. The prediction that one step takes place in a module and a further step takes place in another module does not mean that the modules necessarily have to be different components. It is therefore possible to carry out a lot on a common computer unit. What is significant is rather the logical sequencing of the steps.

[0041] FIG. 4 illustrates the time profile of the detected differential angle and the predicted coupling angle. The time is plotted in seconds on the horizontal axis, and the angle in degrees on the vertical axis. The profile of the detected differential angle is shown by the dashed line, and the predicted coupling angle is shown by the continuous line.

[0042] In FIG. 5, a simulation of the controlled acceleration is plotted against the time. The time is plotted in seconds on the horizontal axis. The acceleration is plotted in percentage up to a random acceleration value on the vertical axis. The severe drop between 85 s and 90 s is due to the coupling process. The rest of the profile of the curve is no longer significant. After the coupling process, the steam turbine 5 and gas turbine 2 are naturally at the same speed.

[0043] Although the invention has been illustrated and described in more detail by means of the preferred exemplary embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.