Arrangement for injecting electric power into an AC network by means of an asynchronous machine, and method for operating the asynchronous machine

Abstract

An arrangement contains an asynchronous machine, which, in generator operation, is configured to feed electric power into an AC network. Accordingly, the asynchronous machine can be dual-fed by a modular multi-stage converter in a matrix configuration. The asynchronous machine has a rotor and the modular multi-stage converter is connected to the rotor of the asynchronous machine.

Claims

1. A configuration, comprising: an asynchronous machine which, in generator operation, is configured to inject electric power into an AC network; and a modular multi-stage converter, wherein said asynchronous machine is operated in a double-feed arrangement by said modular multi-stage converter in a matrix configuration, said multi-stage converter having a plurality of converter arms, each of said converter arms having a series-connected configuration of two-pole switching modules, each of said switching modules having interruptible power semiconductors and an energy store, each of said converter arms having a bridging switch and at least one charging resistor for being bridged by said bridging switch, said at least one charging resistor for pre-charging said energy store.

2. The configuration according to claim 1, wherein said asynchronous machine has a rotor and said modular multi-stage converter is connected to said rotor of said asynchronous machine.

3. The configuration according to claim 1, wherein said multi-stage converter has an n-phase first AC voltage terminal, which is connected to said asynchronous machine, and an m-phase second AC voltage terminal, which is connected to the AC network, wherein each of n phases of said first AC voltage terminal is connected to each of m phases of said second AC voltage terminal by means of exactly one of said converter arms.

4. The configuration according to claim 1, wherein said interruptible power semiconductors and said energy store of said switching modules are respectively mutually connected in a full-bridge circuit.

5. The configuration according to claim 1, further comprising a transformer, said modular multi-stage converter is connected to the AC network via said transformer.

6. The configuration according to claim 1, further comprising a turbine of a conventional energy system, said asynchronous machine is connected, on an input side, to said turbine.

7. The configuration according to claim 6, wherein said turbine is operated at a turbine frequency, wherein the turbine frequency and a frequency of the AC network are different.

8. The configuration according to claim 1, further comprising a control apparatus, by means of said control apparatus reactive power on said asynchronous machine and in the AC network is controllable.

9. A method for operating an asynchronous machine, in a generator operation, for injecting electrical energy into an AC network, which comprises the steps of: operating the asynchronous machine in a double-feed configuration, by an employment of a modular multi-stage converter in a matrix configuration having a plurality of converter arms, each of the converter arms having a series-connected configuration of two-pole switching modules, each of the switching modules having interruptible power semiconductors and an energy store, each of the converter arms having a bridging switch and at least one charging resistor for being bridged by the bridging switch; and pre-charging the at least one charging resistor for the energy store.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows an exemplary embodiment of an arrangement according to the invention, in a schematic representation;

(2) FIG. 2 shows an example of a converter arm of the arrangement according to FIG. 1, in a schematic representation;

(3) FIG. 3 shows an example of a switching module of the arrangement according to FIGS. 1 and 2, in a schematic representation.

DESCRIPTION OF THE INVENTION

(4) Specifically, FIG. 1 represents an arrangement 1, by means of which mechanical energy is delivered on an output 2 of a turbine 3, is convertible into electrical energy and can be injected into an AC network 4. The turbine 3 is a gas turbine, and operates, according to the example represented in FIG. 1, at a turbine frequency of 50 Hz. In the example represented here, the network frequency in the AC network 4 is 60 Hz.

(5) The arrangement 1 comprises an asynchronous machine 5 in the form of a double-feed asynchronous generator (DFIG). The asynchronous machine 5 comprises a stator 6, which is directly connected to the AC network 4. The asynchronous machine 5 further comprises a rotor 7 which is connected by means of sliprings 8a-c, and via optional smoothing inductances 9a-c, to a first three-phase AC voltage terminal 11a-c of a modular multi-stage converter 10, in a matrix configuration.

(6) The multi-stage converter 10 further comprises a second three-phase AC voltage terminal 12a-c, which is connected via a transformer 13 to the AC network 4. The transformer 13, in the example represented, steps up the network-side voltage on the multi-stage converter 10 in the example show to 25 kV. The multi-stage converter 10 comprises nine converter arms A1-A9, wherein one phase respectively of the first AC voltage terminal 11a-c is connected to one phase respectively of the second AC voltage terminal 12a-c via one of the converter arms A1-A9. In the exemplary embodiment represented in FIG. 1, all the converter arms A1-A9 are of an identical design.

(7) The arrangement 1 further comprises a control apparatus (not represented diagrammatically), which is configured for the regulation of current and voltage on both the network side and the rotor side of the multi-stage converter 10 by the appropriate actuation of power semiconductor switches on the multi-stage converter 10.

(8) FIG. 2 shows an example of the layout of one of the converter arms A1-A9 for the multi-stage converter 10 according to FIG. 1. Specifically, FIG. 2 shows a converter arm 14, which is switchable between one phase of a first AC voltage terminal 11a-c and one phase of a second AC voltage terminal 12a-c.

(9) The converter arm 14 comprises a series-connected arrangement of two-pole switching modules 15 wherein, in the exemplary embodiment represented here, all the switching modules 15 are of an identical design. In principle, the mutually series-connected switching modules 15 can assume any number, and can be adapted to the respective application, as indicated in FIG. 2 by a broken line 16. The higher the number of switching modules 15 in the converter arm, the higher the nominal power rating of the associated modular multi-stage converter. An arm inductance 17 is arranged in series with the switching modules 15.

(10) The converter arm 14 further comprises a charging resistor 18, which can be bridged by means of a controllable switch 19.

(11) One example of a switching module 15 in the form of a full-bridge module circuit 101 is schematically represented in FIG. 3. The full-bridge circuit 101 comprises a first semiconductor switch 102 in the form of an IGBT, to which a first freewheeling diode 103 is connected in an antiparallel arrangement, and a second semiconductor switch 104 in the form of an IGBT, to which a second freewheeling diode 105 is connected in an antiparallel arrangement. Both semiconductor switches 102 and 104 have a co-directional conducting direction. The full-bridge circuit 101 further comprises a third semiconductor switch 109 in the form of an IGBT, to which a third freewheeling diode 110 is connected in an antiparallel arrangement, and a fourth semiconductor switch 111 in the form of an IGBT, to which a fourth freewheeling diode 112 is connected in an antiparallel arrangement. Both semiconductor switches 109 and 111 have a co-directional conducting direction. The semiconductor switches 102 and 104, with their associated freewheeling diodes 103, 105, thus constitute a series-connected arrangement, which is connected in parallel with a series-connected arrangement constituted by the semiconductor switches 109, 111 and the associated freewheeling diodes 110 and 112. An energy store in the form of a capacitor 106 is arranged in parallel with the two series-connected arrangements. A first pole or terminal X1 of the switching module 15 is arranged on a potential point 113 between the semiconductor switches 102, 104, and a second pole or terminal X2 of the switching module 15 is arranged on a potential point 114 between the semiconductor switches 109, 111.

(12) By an appropriate actuation of the power semiconductors 102, 104, 109 and 111, a voltage present on the terminals X1, X2 can be generated which corresponds to the voltage Uc present on the capacitor 106, to the voltage across the capacitor 106 but with a reverse polarity (−Uc), or to a zero voltage. It should be observed that, in place of IGBTs, other closable and interruptible semiconductor switches, such as e.g. IGCTs, can also be employed.