TURBINE CONTROL UNIT COMPRISING A THERMAL STRESS CONTROLLER AS A MASTER CONTROLLER

Abstract

A turbine control unit and method for controlling a turbine, in particular for controlling the start-up of a turbine, the unit being designed as a cascade controller having a master controller and an inner controller, the master controller being a thermal stress controller for the components subjected to thermal stress.

Claims

1. A turbine control unit for controlling a turbine, comprising: a cascade controller having a master controller and an inner controller, wherein the master controller is a thermal stress controller for the temperature of components which are subjected to thermal stress.

2. The turbine control unit as claimed in claim 1, wherein the inner controller comprises a turbine controller that controls the turbine power level.

3. The turbine control unit as claimed in claim 1, further comprising: a thermal stress calculation unit that predefines at least one setpoint value to the thermal stress controller.

4. The turbine control unit as claimed in claim 1, wherein the thermal stress controller is designed to ensure for such control of the turbine that a desired rise in temperature over time is not exceeded.

5. The turbine control unit as claimed in claim 1, wherein the thermal stress controller is designed to avoid thermal stress which is caused by temperature differences.

6. The turbine control unit as claimed in claim 2, wherein the turbine controller that controls the turbine power level is designed to generate setpoint values for position controllers which can control the position of actuating valves.

7. The turbine control unit as claimed in claim 1, wherein the turbine control unit is designed to control partial turbines separately.

8. The turbine control unit as claimed in claim 1, further comprising: temperature sensors mounted at various locations on the turbine.

9. A method for controlling a turbine having a cascade controller comprising a master controller and an inner controller, the method comprising: sensing by the master controller thermal stress of the turbine, and transferring setpoint values to the inner controller which are such that undesired thermal stress of the turbine is avoided.

10. The method as claimed in claim 9, wherein the master controller senses the thermal stress of the turbine by a rise in temperature over time, and determines the thermal stress arising therefrom, wherein in the case of excessively high thermal stress the setpoint value is transferred to the inner controller to reduce the increase in power of the turbine, in the case of thermal stress within a desired range the setpoint value is transferred in order to be able to maintain the increase in power, and in the case of thermal stress below a threshold value the setpoint value is transferred in order to be able to boost the increase in power.

11. The turbine control unit as claimed in claim 1, wherein the turbine control unit controls the starting of a turbine.

12. The turbine control unit as claimed in claim 7, wherein the partial turbines comprise a high-pressure turbine, a medium-pressure turbine and a low-pressure turbine.

13. The turbine control unit as claimed in claim 8, wherein the temperature sensors are mounted on a high-pressure turbine and/or on a medium-pressure turbine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further details will be explained with reference to a figure which shows a turbine control unit in a schematic view.

DETAILED DESCRIPTION OF INVENTION

[0027] A turbine control unit 1 is shown. A thermal stress controller 2 serves as a master controller and transfers setpoint values to an inner controller 3 which is embodied as a controller of the turbine power level. A thermal stress calculation unit 4 is connected upstream of the thermal stress controller 2. Said thermal stress calculation unit 4 evaluates signals which originate from temperature sensors 5 for a high-pressure turbine 6 and from temperature sensors 7 for a medium-pressure turbine 8. Even though the figure respectively illustrates just one temperature sensor in a schematic view, there are in fact appropriately a plurality of temperature sensors. The thermal stress calculation unit 4 determines thermal stress of the high-pressure turbine 6 of the medium-pressure turbine 8 and of a low-pressure turbine 10 from the signals of the temperature sensors 5 and 7 using stored data. In this context, in particular the rise in temperature over time is considered, which rise must not be too high in order to avoid excessively high thermal stresses.

[0028] The thermal stress calculation unit 4 communicates to the thermal stress controller 2 whether the thermal stress is to be increased, is to remain the same or is to drop. As a function of this, the thermal stress controller 2 transfers suitable setpoint values to the controller 3 of the turbine power level, as a function of which setpoint values it is determined whether a rise in power level of the turbine is to be reduced, boosted or kept constant. This is carried out separately in each case for the high-pressure turbine 6, the medium-pressure turbine 8 and the low-pressure turbine 10.

[0029] The controller 3 of the turbine power level transfers corresponding setpoint values to a position controller 11. The position controller 11 controls, on the basis of the transferred setpoint values, a position of a live steam actuating valve 12, which influences the supply of steam to the high-pressure turbine 6, a position of an interception actuating valve 13 which influences the supply of steam to the medium-pressure turbine 8, and a position of a supply steam valve 14 which influences the supply of steam to the low-pressure turbine 10.

[0030] A position meter 15 is situated on the live steam actuating valve 12, a position meter 16 on the interception actuating valve 13, and a position meter 17 on the supply steam valve 14. The position meters 15, 16 and 17 transfer values to the position controller 11. Therefore the position controller 11 has the information as to whether the position of the live steam actuating valve 11, interception actuating valve 13 and supply steam valve 14 has assumed the respectively desired value or whether opening or closing is necessary.

[0031] At this point details will briefly be given of a simplified steam circuit. Wet steam coming from the low-pressure turbine 10 is condensed in a condenser 18. The water which is produced here is fed into a steam generator 20 with a feed water pump 19. From said steam generator 20 the steam passes through the live steam actuating valve 12 to the high-pressure turbine 6. Steam coming from the high-pressure turbine is heated in a reheater 26. The steam flows from the reheater 26 through the interception actuating valve 13 into the medium-pressure turbine 8. After relaxing in the medium-pressure turbine 8, the steam flows into the low-pressure turbine 10. In this context, steam coming from the steam generator 20 can be added depending on the degree of opening of the supply steam valve 14.

[0032] The high-pressure turbine 6, the medium-pressure turbine 8 and the low-pressure turbine 10 together drive a generator 21. The power level of said generator 21 is determined with a power meter 22 and transferred to the controller 3 of the turbine power level. In addition, a rotational speed meter 23 is provided which supplies the controller 3 of the turbine power level with the rotational speed of the turbine and generator 21.

[0033] There is a pressure meter 24 downstream of the live steam actuating valve 12 in the direction of flow, a pressure meter 25 downstream of the interception actuating valve 13, and a pressure meter 27 downstream of the supply steam valve 14. The respectively sensed pressure values are transferred to the controller 3 of the turbine power level.

[0034] Although the invention has been illustrated and described in 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.