START-UP CONVERTER

• US 3,764,815 A
• Filed: 03/03/1972
• Issued: 10/09/1973
• Est. Priority Date: 03/06/1971
• Status: Expired due to Term

• Current Assignee: Adolf Habock, Kurt Fork
• Original Assignee: Adolf Habock, Kurt Fork
• Inventors: Fork, Kurt, Habock, Adolf
• Primary Examiner(s): Shoop, Jr., William M.
• Application Number:
  US05/231,543
• Time in Patent Office: 585 Days
• Field of Search: 290/38,52
• US Class Current: 290/52
• CPC Class Codes: F01D 19/00 Starting of machines or engines; Regulating, controlling, or safety means in connection therewith warming-up before starting F01D25/10; turning or inching gear F01D25/34
• CPC Class Codes: H02P 9/08 Control of generator circuit during starting or stopping of driving means, e.g. for initiating excitation

Abstract

Apparatus for starting up the turbine of a gas turbine unit or a pump storage unit having a generator coupled to the turbine, which includes a frequency converter of variable output frequency which connects a supply voltage to the generator during start-up. The generator is accelerated by the frequency converter as a synchronous motor until a predetermined speed is reached. The frequency converter is a static semiconductor converter. The starting-up apparatus eliminates the need for providing a separate starter motor for the turbines. According to a further embodiment, the semiconductor converter includes a speed control arrangement for maintaining the generator shaft at an adjustable, desired speed until the turbine unit is either accelerated by the frequency converter to the predetermined speed or is further decelerated or stopped. The speed control arrangement avoids the very rapid accelerations and decelerations of the turbine shaft otherwise accompanying start-up and shut down, thereby preventing distortions in the turbine shaft caused by non-uniform heating and cooling.

Claims

1. Apparatus for starting up a gas turbine unit or the pump turbine of a pump storage unit, comprising:

a generator which is coupled to the turbine of said gas turbine or pump storage unit;

power supply means for said gnerator; and

a static semiconductor frequency converter connected between said power supply means and said generator during startup of the turbine, said frequency converter including a controllable rectifier which is connected on its input side to said power supply means, and a controllable inverter which is connected on its output side to said generator, said inverter being connected with said rectifier via an intermediate DC choke circuit, said inverter having commutating means, said inverter being timed during the start-up by a position transmitter which is coupled to the shaft of said generator, as a function of the position of said shaft, and said frequency converter providing a variable output frequency and accelerating said generator synchronously as a synchronous motor from zero speed until a predetermined speed is reached.

2. Apparatus as recited in claim 1, wherein said rectifier is connected on its input side to an auxiliary starting arrangement serving as power supply means.

3. Apparatus as recited in claim 1, wherein said semiconductor converter is provided as a braking device for synchronously decelerating said generator.

4. Apparatus as recited in claim 1, wherein said inverter is designed as a self-commutating inverter with quenching means connected between said inverter and said rectifier.

5. Apparatus as recited in claim 1, wherein the intermediate-circuit current is made zero for the commutation of the inverter, in the event that the commutation voltage is absent because the speed is too low.

6. Apparatus as recited in claim 1, wherein the exciter winding of said generator is fed during starting up from an auxiliary voltage source, and upon reaching a predetermined speed said rectifier is connected as the excitation rectifier to said exciter winding in lieu of said auxiliary voltage source, my means of at least one circuit breaker.

7. Apparatus as recited in claim 1, also comprising a voltage control for the voltage at the output of the inverter or at the input of the generator, respectively, which voltage control, after reaching a maximum permissible output voltage of said inverter, reduces, during starting, the current through the exciter winding of the generator in such a manner that the permissible output voltage is not exceeded.

8. Apparatus as recited in claim 1, further comprising a speed control arrangement at the semiconductor converter for maintaining the speed of rotation of the shaft of said generator constant.

9. Apparatus as recited in claim 8, further comprising a tachometer for determining the actual speed of the shaft;

a reference-speed setting device with adjustable reference speed which is connected, together with said tachometer, to a comparator;

a speed control connected to said comparator;

the output signal of said speed control being fed as the reference value of the armature current to a first input of an armature-current comparator having a second input which is fed from a probe for the actual value of the armature current; and

a control unit connected to said armature current comparator via an armature-current regulator.

10. Apparatus as recited in claim 9, wherein a maximum output limit value, dependent on the actual speed, is set into the speed control by means of a function generator.

11. Apparatus as recited in claim 10, wherein sAid speed control can be removed from the connection between said function generator and said control unit by means of a double-throw switch, when switching to another mode of operation.

12. Apparatus as recited in claim 9, wherein said tachometer comprises a magnet-wheel position transmitter with a following frequency-voltage converter.

13. Apparatus as recited in claim 1, wherein said inverter is designed as a self-commutating inverter with quenching means connected between said inverter and said rectifier.

14. Apparatus as recited in claim 1, wherein the intermediate-circuit current is made zero for the commutation of the inverter, in the event that the commutation voltage is absent because the speed is too low.

15. Apparatus as recited in claim 3, wherein the exciter winding of said generator is fed during starting up from an auxiliary voltage source, and upon reaching a predetermined speed said rectifier is connected as the excitation receifier to said exciter winding in lieu of said auxiliary voltage source, by means of at least one circuit breaker.

16. Apparatus as recited in claim 2, also comprising voltage control for the voltage at the output of the inverter or at the input of the generator, respectively, which voltage control, after reaching a maximum permissible output voltage of said inverter, reduces, during starting, the current through the exciter winding of the generator in such a manner that the permissible output voltage is not exceeded.

17. Apparatus as recited in claim 2, further comprising a speed control arrangement at the semiconductor converter for maintaining the speed of rotation of the shaft of said generator constant.

18. Method for starting-up a gas turbine unit or a pump storage unit having a generator coupled to a turbine thereof, comprising:

connecting said generator to a supply voltage by means of a frequency converter during the start-up acceleration in a manner which operates said generator as a synchronous motor, said frequency converter including a controllable rectifier which is connected on its input side to said supply voltage and a controllable inverter which is connected on its output side to said generator, said inverter being connected with said rectifier via an intermediate DC choke circuit, and said inverter having commutating means;

accelerating said generator synchronously, by said frequency converter, as a synchronous motor from zero speed until a predetermined speed is reached;

disconnecting said generator from said frequency converter when a predetermined speed is reached; and

timing said frequency converter during starting-up by generating commutation commands which depend on the position of the shaft of said generator.

19. Method as recited in claim 18, further comprising, accelerating said generator of a gas turbine set by means of the frequency converter up to a disengagement speed which corresponds to about one-half the nominal speed, at which said generator is subsequently accelerated by the turbine, with the frequency converter disconnected, to the full nominal speed which corresponds to the frequency of the system to be supplied.

20. Method as recited in claim 18, further comprising, accelerating the generator of a pump storage unit by means of said frequency converter up to a full nominal speed.

21. Method as recited in claim 18, further comprising, accelerating said generator, with the turbine not coupled, by means of said frequency converter to beyond the nominal speed of the generator which corresponds to the frequency of the system to be supplied, whereby said generator is subsequently synchronized when running down.

22. Method as recited in claim 18, wherein several generators are turned by connecting a number of generators in cyclic succession, accelerating the respectively connected generator to a predetermined release speed after which it subsequently runs down uncontrolled until it is again accelerated in the next cycle to the release speed.

23. MetHod as recited in claim 18, further comprising:

at a first point in time, connecting a first generator, which is selected from a number of generators, to an inverter of said frequency converter;

turning said generator at a predetermined desired speed with a speed control device enabled;

from a second point in time, accelerating said first generator until a predetermined release speed is reached;

from a third point in time, accelerating a second generator to a predetermined speed by means of said frequency converter, while the first generator is disconnected from said frequency converter and runs down uncontrolled; and

from a fourth point in time, reconnecting said first generator to said inverter, whereby the speed control arrangement is enabled in said process.