SYNCHRONISING A TURBINE WITH AN AC NETWORK ACCORDING TO A TARGET TRAJECTORY FOR THE TARGET DIFFERENCE ANGLE

Abstract

A method for synchronising a turbine with an AC network having a network frequency, having the following steps: A) accelerating the turbine up to a stated rotational speed, without taking into consideration a difference angle between the turbine and the AC network; B) detecting a difference angle between the turbine and the AC network; C) accelerating or decelerating the turbine in such a way that the differential speed follows a target trajectory, wherein the target trajectory is a trajectory that indicates a target rotational speed depending on the detected difference angle, such that a target angular position that is suitable for a synchronous supply is achieved between the turbine and AC network.

Claims

1. A method for synchronizing a turbine with an AC network having a network frequency, comprising: A) accelerating the turbine up to a nominal rotational speed without taking into consideration a difference angle between turbine and AC network; B) detecting a difference angle between turbine and AC network; C) accelerating or decelerating the turbine such that the differential speed follows a target trajectory, wherein the target trajectory is a trajectory which specifies a target rotational speed in dependence on the detected difference angle, so that a target angular position suitable for a synchronous supply is achieved between turbine and AC network.

2. The method as claimed in claim 1, wherein the target trajectory provides a linear curve of a target difference angle.

3. The method as claimed in claim 1, wherein the turbine is accelerated if the difference angle is greater than the target difference angle given by the target trajectory and decelerated if the difference angle is less than the target difference angle given by the target trajectory.

4. The method as claimed in claim 1, wherein the differential speed between turbine and AC network is detected and taken into consideration when following the target trajectory.

5. The method as claimed in claim 1, further comprising: a synchronizing device configured to carry out steps B) and C).

6. A control device for a turbine, wherein the control device is configured to control a turbine according to a method as claimed in claim 1.

7. The control device as claimed in claim 6, further comprising: a synchronizing device configured to detect a difference angle between turbine and AC network and a differential speed between turbine and AC network and to transfer instructions for acceleration or deceleration of the turbine to a turbine control unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The invention will be explained in greater detail hereafter on the basis of an exemplary embodiment with the use of figures. In the figures:

[0034] FIG. 1 shows a rotational-speed-regulated acceleration of the turbine;

[0035] FIG. 2 shows an exemplary curve of the difference angle after reaching a nominal rotational speed;

[0036] FIG. 3 shows the difference angle being regulated out to a target angular position via a ramp function;

[0037] FIG. 4 shows a change of the rotational speed of the turbine during the synchronization;

[0038] FIG. 5 shows a schematic construction of the regulation for reaching the target angular position;

[0039] FIG. 6 shows the regulation of the turbine frequency up to the nominal rotational speed.

DETAILED DESCRIPTION OF INVENTION

[0040] In FIG. 1, the time in seconds is specified on the abscissa and the turbine frequency in hertz is specified on the ordinate. The rotational-speed-regulated acceleration up to a nominal rotational speed of 50 Hz is shown. The acceleration is regulated and therefore practically no overshoot takes place, i.e., an acceleration of the turbine beyond the nominal rotational speed is substantially avoided.

[0041] In FIG. 2, the time in seconds is again on the abscissa and the detected difference angle in degrees is on the ordinate. As in FIG. 1, the time from 40 seconds to 80 seconds after beginning the acceleration is shown. In the case of this exemplary curve of the difference angle, after 80 seconds, i.e., after completion of the acceleration to the nominal rotational speed, a difference angle of 62.5 results.

[0042] The turbine thus leads the network by 62.5. The turbine is therefore now to be rotated more slowly in order to reach a target angle of 0, wherein turbine frequency and network frequency certainly have to correspond upon reaching the target angle.

[0043] FIG. 3 makes the regulation comprehensible. The time after beginning the acceleration in seconds is plotted on the abscissa and the difference angle between turbine and network is plotted on the ordinate. The solid line shows the curve of the actual difference angle. The curve known from FIG. 2 can be seen from the time value 55 seconds up to the time value 80 seconds. A regulated approach to the target angular position begins thereafter. The dashed line is to be observed for this purpose. This indicates a target difference angle at the respective point in time. The line begins at the time value 80 seconds with the actual difference angle of 62.5. A difference angle of 0 is finally desired; the target angular position is thus 0.

[0044] To achieve this, a target difference angle curve according to the dashed line is specified. In this case, this is a ramp, i.e., a curve linear over time between the actual difference angle at the beginning of the regulation, in the present case thus 62.5, and the target angular position, in the present case thus as usual 0.

[0045] It is now possible to continuously compare the detected difference angle to the target difference angle and to accelerate or decelerate the turbine accordingly. As already stated above in conjunction with the overshoot, the acceleration or deceleration cannot be changed arbitrarily rapidly. This is taken into consideration by a limited slope of the ramp and the regulatory feedback of the deviation between target difference angle and detected difference angle.

[0046] By way of the linear curve of the target difference angle at the target angular position, the specification is made by the regulation that the difference angle remains constant. If the difference angle remains constant, turbine frequency and network frequency corresponding is achieved automatically.

[0047] The curve of the turbine frequency resulting due to the regulation is made clear by FIG. 4. The time after beginning the acceleration in seconds is again plotted on the abscissa and the turbine frequency in hertz is plotted on the ordinate. If one observes the curve of the turbine frequency in the range from 55 seconds to 80 seconds after beginning the acceleration, a slight overshoot of the turbine, i.e., a slight acceleration beyond the network frequency is apparent.

[0048] The range which is now actually of interest is the range from 80 seconds after beginning the acceleration. As described above, at the detected difference angle of 62.5, the turbine temporarily has to be slower than the network. This is achieved in that the target difference angle is followed, as explained in FIG. 3.

[0049] The construction of the regulation is schematically shown in FIG. 5. A target trajectory module 1 specifies a curve of the target difference angle 2. In this case, a ramp is generally selected as explained in FIG. 3, which extends linearly over time from the difference angle 3 detected at the beginning of the regulation up to the desired target angular position. After reaching the target angular position, the target trajectory extends linearly, it is thus requested that the target angular position is maintained.

[0050] The target trajectory module 1 thus outputs the target difference angle 2. This is compared to the detected difference angle 3. The difference angle comparison value 4 thus obtained is transferred to an analysis unit 5, which ascertains therefrom by which value the turbine frequency is to be elevated or lowered. A target frequency 6 is thus ascertained, which can be transferred to a turbine control unit. The turbine control unit has the task of controlling the valve position for the steam supply and thus the turbine. In the typical turbine control units, this is performed, inter alia, in dependence on a target frequency. Therefore, although it actually relates to the acceleration or deceleration of the turbine, a target frequency 6 is ascertained. The turbine control unit certainly finally in turn ensures an acceleration or deceleration.

[0051] The regulation of the turbine frequency up to the nominal rotational speed is shown in FIG. 6. An acceleration module 7 specifies a target acceleration 8, i.e., a linear acceleration up to a nominal rotational speed. The target acceleration 8 is output. It is furthermore incorporated as a switching criterion 9 that an adjustment time is to be taken into consideration until the acceleration can be set to zero, since as explained above, the adjustment of the valve which controls the steam supply to the turbine requires a certain amount of time. The target acceleration 8 is converted into a target rotational speed change 10 in consideration of the switching criterion 9. With observation of the network frequency 11, a turbine target frequency 12 results which is transferred to the turbine control unit 13.

[0052] Although the invention was illustrated and described in greater detail by the preferred exemplary embodiment, the invention is not thus restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without leaving the scope of protection of the invention.