Method for coupling two sub-shafts

Abstract

A method for coupling a first sub-shaft, which has a first turbomachine and a generator connected to a mains supply, to a second sub-shaft, which has a second turbomachine, by means of an overrunning clutch, has the following steps: a) rotating the second sub-shaft with a starting rotational speed which is lower than the rotational speed of the first sub-shaft; b) measuring the mains frequency of the mains supply; c) measuring a differential angle between the first sub-shaft and the second sub-shaft; d) accelerating the second sub-shaft with an acceleration value which is produced using the mains frequency measured in step b), the differential angle and the starting rotational speed, and therefore the overrunning clutch couples the two sub-shafts to each other with a previously determined target coupling angle.

Claims

1. A method for coupling a first sub-shaft, which has a first fluid-flow machine and a generator connected to a mains supply, to a second sub-shaft, which has a second fluid-flow machine, by means of an overrunning clutch, comprising the steps: a) rotating the second sub-shaft with an initial rotational speed which is lower than the rotational speed of the first sub-shaft; b) measuring the mains frequency of the mains supply; c) measuring a differential angle between the first sub-shaft and the second sub-shaft; d) accelerating the second sub-shaft with an acceleration value which is produced by using the mains frequency measured in step b), the differential angle and the initial rotational speed, so that the overrunning clutch couples the two sub-shafts to each other with a previously determined target coupling angle; e) measuring a new mains frequency during the accelerations of the second sub-shaft; f) in the event that the new mains frequency is different from the mains frequency measured in step b), accelerating the second sub-shaft with a changed acceleration value, which is produced by using the new mains frequency.

2. The method as claimed in claim 1, further comprising the step: g) repeating steps e) and f) at least once.

3. The method as claimed in claim 1, wherein the mains frequency is measured electrically and/or by measuring the rotational speed of the first sub-shaft.

4. The method as claimed in claim 1, further comprising the steps: b1) forming a difference between the mains frequency and a reference mains frequency; c1) determining an initial acceleration value by using the differential angle, the initial rotational speed and the reference mains frequency; wherein in step d) the acceleration value is determined by using the initial acceleration value and the difference.

5. The method as claimed in claim 1, wherein step d) is carried out as soon as the differential angle measured in step c) is equal to a reference differential angle.

6. The method as claimed in claim 5, further comprising the steps: b1) forming a difference between the mains frequency and a reference mains frequency; c1) determining an initial acceleration value by using the reference differential angle, the initial rotational speed and the reference mains frequency; wherein in step d) the acceleration value is determined by using the initial acceleration value and the difference.

7. The method as claimed in claim 1, wherein the initial rotational speed and the acceleration value are entered as set points into a rotational speed control system of the second sub-shaft.

8. The method as claimed in claim 1, wherein the first fluid-flow machine is a gas turbine and the second fluid-flow machine is a steam turbine.

9. The method as claimed in claim 1, wherein the first fluid-flow machine is a steam turbine and the second fluid-flow machine is a steam turbine.

10. The method as claimed in claim 1, further comprising the step: g) repeating steps e) and f) continuously.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to illustrate the method, the FIGURE illustrates a logical scheme 1 for implementing the method.

DETAILED DESCRIPTION OF INVENTION

(2) Firstly, the second sub-shaft is rotated with an initial rotational speed which is lower than the rotational speed of the first sub-shaft. The initial rotational speed can be about 0.5 Hz to 1.5 Hz, in particular 0.9 Hz to 1.1 Hz, lower than a reference mains frequency. This ensures that, even in the event of typically occurring fluctuations of the rotational speed of the first sub-shaft, the second sub-shaft is slower than the first sub-shaft at the initial rotational speed. The reference mains frequency 3 is, for example, 50 Hz or 60 Hz. The initial rotational speed can be entered as a set point into a rotational speed control system 9 of the second sub-shaft.

(3) As can be seen from the FIGURE, the mains frequency 2 of the mains supply is measured. This can be done electrically or by measuring the rotational speed of the first sub-shaft. A difference 4 is then formed between the mains frequency 2 and the reference mains frequency 3 of the mains supply. The difference 4 is processed further in a processing step 5. For example, scaling, an offset shift or integration of the difference can be carried out. In addition, an initial acceleration value 6, which is produced by using the initial rotational speed and the reference mains frequency, is determined. By using the initial acceleration value 6, a rotational speed set point is calculated. In order to determine the rotational speed set point, the duration of an acceleration starting time is also used. In order to find a suitable acceleration starting time for accelerating the second sub-shaft, the second sub-shaft can be kept at the initial rotational speed until the differential angle is equal to a reference differential angle. In this case, the reference differential angle is also used for determining the initial acceleration value 6. Alternatively, the second sub-shaft can be accelerated at an arbitrary acceleration starting time. In this case, the differential angle measured at the arbitrary time is also used in order to determine the initial acceleration value 6.

(4) The initial acceleration value 6 can, for example, be determined experimentally. For this purpose, the angle covered during a coupling process between the first sub-shaft and the second sub-shaft, and also the mains frequency, can be measured in a time-resolved manner. From the deviations of the mains frequency, occurring during the coupling operation, from the reference mains frequency and the angle covered, the initial acceleration value 6 can be deduced.

(5) In a correction step 7, the rotational speed set point is corrected with the difference processed in the processing step 5, which results in a corrected rotational speed set point 8. For example, in the processing step 5, the difference can be multiplied by a factor 1 and, in the correction step 7, the difference can be added to the rotational speed set point, which forms the corrected rotational speed set point 8. This can be done continuously, for example. The corrected rotational speed set point 8 is entered as a set point into the rotational speed control system 9 of the second sub-shaft, so that the second sub-shaft is accelerated and the two sub-shafts are coupled to each other.

(6) It is conceivable for a new mains frequency to be measured during the accelerations of the second sub-shaft. In the event that the new mains frequency is different from the previously measured mains frequency, the second sub-shaft is accelerated with a changed acceleration value, which is produced by using the new mains frequency. Furthermore, the rotational speed of the second sub-shaft and a new differential angle, which are present at the time at which the new mains frequency is measured, are used. For the rotational speed, the reference rotational speed from the rotational speed control system or a measured rotational speed can be used. It is also conceivable that this is carried out many times when accelerating the second sub-shaft or continuously when accelerating the second sub-shaft.

(7) Although the invention has been illustrated and described in detail by means of the preferred exemplary embodiment, the invention is not restricted by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the protective scope of the invention.