WO2010018194A2

WO2010018194A2 - Power plant system for selective operation in power networks at various network frequencies

Info

Publication number: WO2010018194A2
Application number: PCT/EP2009/060438
Authority: WO
Inventors: Floris Van Straaten; Jürgen Hoffmann
Original assignee: Alstom Technology Ltd.
Priority date: 2008-08-15
Filing date: 2009-08-12
Publication date: 2010-02-18
Also published as: JP2012500608A; JP5627584B2; CH699321A1; BRPI0917652A2; BRPI0917652B1; WO2010018194A3

Abstract

The invention relates to a power plant system (10) comprising at least one shaft line (11) of a turbine and one generator (18) driven directly by the turbine, said generator generating an alternating current at an operating frequency. The at least one generator (18) provides electrical power by way of an electronic frequency converter (27) and at least one step-up transformer (3, 4) alternatively at a first electrical network (1) at a first operating frequency or at a second electrical network (2) at a second operating frequency. The invention further relates to a method for operating such a power plant system (10).

Description

DESCRIPTION

POWER PLANT FOR OPTIONAL OPERATION IN ELECTRICITY NETWORKS WITH

DIFFERENT NETWORK FREQUENCY

TECHNICAL AREA

The present invention relates to the field of power plant technology. It relates to a power plant with electronic frequency conversion between generator and network and a method for operating such a power plant.

STATE OF THE ART

Large power plants with outputs in the range of more than 100 MW, in which a generator generating electricity is driven by a turbine and feeds the generated electric power into a grid with a given grid frequency (eg 50 or 60 Hz) usually have a fixed coupling between the grid (mechanical) speed of the turbine and the mains frequency. The output of the generator is connected in a frequency-locked manner via a network connection to the network, while it is driven by the turbine either directly (1-shaft system) or via a mechanical gear speed-coupled. By means of gear only fixed ratios between a turbine and a grid frequency can be realized.

These turbines have traditionally been designed to drive generators to generate electrical power, which is then fed into a grid having a predetermined line frequency (either 50 Hz or 60 Hz).

1 shows, in a greatly simplified representation, a power plant 10 'of a known type, which generates power by means of a gas turbine 12 with a coupled first generator 118 and a steam turbine 24 with a coupled second generator 108 and feeds it into a network 1. The gas turbine 12 and the

Generator 118 are connected by a common shaft 19 and form a shaft train 1 1. The gas turbine comprises in the simplest case, a compressor 13, which sucks and compresses combustion air via an air inlet 16. The compressor 13 may be composed of a plurality of partial compressors connected in series, which operate on rising pressure level and possibly allow an intermediate cooling of the compressed air. The combustion air compressed in the compressor 13 enters a combustion chamber 15 into which liquid (e.g., oil) or gaseous (e.g., natural gas) fuel is injected via a fuel supply 17 and burned using combustion air.

The emerging from the combustion chamber 15 hot gases are relaxed in a subsequent turbine 14 under work and thus drive the compressor 13 and the coupled first generator 118 at. The still relatively hot exhaust gas at the exit from the turbine is sent through a subsequent heat recovery steam generator 23 in order to generate steam for the operation of a steam turbine 24 in a separate water-steam circuit 25. Condenser, feedwater pump and other systems of water Steam cycle 25 are not shown for simplicity of illustration. Such a combination of gas turbine and steam power plant is referred to as a combined cycle power plant. The steam turbine 24 may be coupled to the first generator 118 on the opposite side of the turbine 14; The gas turbine 12, the first generator 118 and the steam turbine 24 then form a so-called "single shaft power train." However, the steam turbine 24 can also drive its own second generator 108 on a separate shaft train 1 1 ', as shown in FIG For example, so-called 2-to-1 arrangements in which a steam turbine 24 is supplied with steam on a shaft train 11 'with a second generator 108 through two downstream gas turbines 12 are used widely each arranged on a shaft train 1 1 with its own first generator 118. Analogously, there are also arrangements in which the steam of three or more gas turbines 12 downstream boilers 23 used for the drive of a steam turbine 24.

In the 1-shaft gas turbine of FIG. 1, the rotational speed of the gas turbine 12 is in a fixed ratio to the generated in the first generator 1 18 frequency of the AC voltage, which is equal to the network frequency of the network 1. In today's large gas turbine units with outputs of over 100 MW, the generator frequency or mains frequency of 60 Hz is a gas turbine speed of 3600 rpm (eg gas turbine GT24 of the Applicant) and the generator frequency of 50 Hz a speed of 3000 rpm (eg gas turbine GT26 of the Applicant) assigned.

For applications where power is fed into networks of different voltages and frequencies, power is conventionally produced as alternating current at one frequency and then converted to the second frequency via frequency converters as needed. This is typically done by rectifier followed by an alternating direction. A well-known example of this is ITAIPU on the Brazilian-Paraguayan border. Frequency converter for use in However, power plants are expensive according to the high power to be transmitted and also associated with power losses. The basic possibility to supply power directly from a power plant to consumers or networks with different frequencies was first mentioned in the Swiss application number CH00246 / 07.

PRESENTATION OF THE INVENTION

It is an object of the invention to provide a power plant for supplying power networks with different power frequencies, which avoids the disadvantages of known power plants and in particular allows the introduction of electrical power in power grids with different operating frequencies with high efficiency, and to provide a method for their operation.

The object is solved by the totality of the features of claims 1 and 9. An essential point of the invention is that between the driven by a turbine generator and a step-up transformer via which the power is fed into the power grids, an electronic

Frequency converter is arranged, which converts the current with the output frequency of the generator optionally in the operating frequency of a first or a second network.

In order to realize the current introduction with the correct voltage, a first step-up transformer with a first voltage ratio is arranged, for example, for connection to the first electrical network between the electronic frequency converter and the first network. Accordingly, for the connection to the second network between the electronic frequency converter and the second network, a second

Clamping transformer arranged with a second voltage ratio. Alternatively, for example, at least one step-up transformer, from which either two voltages can be tapped, may be used to connect to the electrical networks. For connection to the first electrical network, a first voltage ratio and for connection to the second network a second voltage ratio is tapped.

Another step to make the operation of a power plant having at least two wave strands, each comprising at least one generator, an arrangement in which each of the generators is selectively connected to the first network at the first operating frequency via a frequency converter, at least one high voltage switch and at least one step-up transformer or the second network is connectable to the second operating frequency. This allows to optimize the power plant operation to supply electricity either in only one of the two networks or to supply both networks in parallel with electricity.

In addition to the power plant with device for feeding into two power grids, a method for its operation is proposed. This is characterized in that for feeding into the first power grid with the first power frequency of the frequency converter is controlled so that it generates an output current at the first power frequency, and that the frequency converter is connected via a step-up transformer to the first power grid. Further, it is characterized by the fact that for feeding into the second power grid with the second power frequency of the frequency converter is controlled so that it generates an output current at the second power frequency and the frequency converter is connected via a step-up transformer to the second power grid.

Another important aspect of the invention is the supply of the power plant's own power grid, which can operate at an operating frequency regardless of the frequency of the network to which power is supplied. The power plant's own power grid is typically designed as a medium-voltage grid, which is why the further discussion refers to the medium-voltage grid, without this being interpreted as a limitation. It supplies various major consumers, such as combustion gas compressors, NOx water pumps and low-voltage grids for local consumers. The medium-voltage network is conventionally supplied by the generator via an auxiliary transformer. The frequency of the medium-voltage network is identical to that of the generator.

According to the invention, in order to feed the power plant's own power grid, new circuits and methods for operating the power plant are proposed. In particular, the optional supply of the medium-voltage network via an auxiliary transformer or via an auxiliary frequency converter connected in series with the auxiliary frequency converter is proposed. If the generated power is supplied by the electronic frequency converter with a first operating frequency and the frequency of the medium-voltage network is equal to the first operating frequency, the medium-voltage network is supplied directly via the auxiliary transformer. If the generated power is supplied by the electronic frequency converter at a second operating frequency and the frequency of the medium-voltage network is equal to a first operating frequency, the medium-voltage network is supplied via the auxiliary frequency converter and the auxiliary transformer. The auxiliary frequency shaper converts the power required for the power plant's own medium-voltage grid into its grid frequency. This conversion will typically occur before transformation to medium voltage. An arrangement in which is first transformed to medium voltage and then the frequency is converted is also conceivable. This may even be advantageous to avoid costly high voltage switches and to replace them with medium voltage switches.

Alternatively, in order to minimize the number of switches and lines, the power supply of the power plant's own power grid, independent of the output frequency of the electronic frequency converter, can always be Frequency converter can be performed, which is switched so that it outputs power at the operating frequency of the power plant's own medium voltage network. In the event that the output frequency of the electronic frequency converter is equal to the operating frequency of the power plant's own medium-voltage network, the auxiliary frequency converter operates with a frequency ratio of one. This means that the auxiliary frequency converter in this mode leads to power loss without any effective benefit. Due to the low power transmitted relative to the overall performance of the power plant, the power losses are moderate, so that this simpler arrangement, which also simplifies the operating method, can be advantageous overall.

According to one embodiment of the invention, the first network frequency differs significantly from the second network frequency, wherein the first network frequency is either smaller than the second network frequency, and the second network frequency is 50 Hz or 60 Hz. In particular, the second

Mains frequency is 60 Hz and the first mains frequency is 50 Hz.

Or the first mains frequency is greater than the second mains frequency, the second mains frequency being 50 Hz or 60 Hz. In particular, the second mains frequency can be 50 Hz and the first mains frequency is 60 Hz.

Preferably, the turbine is designed for a power greater than 50 MW.

Preference is given to electronic frequency converters in the form of matrix converters. These comprise a plurality of controllable bidirectional switches arranged in a (m × n) matrix and controlled by a controller m optionally connect inputs to n outputs, where m is greater than n. By using matrix converters, the power losses can be kept small

Alternatively, for example, the use of frequency converters is conceivable. These consist of a rectifier, a DC or DC link feeds, and one fed from this intermediate circuit inverter, which selectively generates alternating current with the first or second operating frequency.

BRIEF EXPLANATION OF THE FIGURES

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it

Fig. 1 is a highly simplified circuit diagram of a combined cycle power plant with a gas turbine and a downstream water-steam cycle according to the prior art;

Fig. 2 is a greatly simplified section of a single line

Diagram (one-line diagram) of a power plant according to the prior art;

Fig. 3 is a greatly simplified section of a single-line diagram of a power plant according to a

Embodiment of the invention with two Aufspanntransformatoren for feeding into two networks;

4 is a greatly simplified section of a single line diagram of a power plant according to a

Embodiment of the invention with a step-up transformer for feeding into two networks;

5 is a greatly simplified section of a single line diagram of a power plant according to a

Embodiment of the invention with two Step-up transformers for feeding into two networks and cost-optimized power supply of the auxiliary systems;

6 is a greatly simplified section of a single line diagram of a power plant according to a

Embodiment of the invention with two Aufspanntransformatoren for feeding into two networks and circuit for switching the feed from the first network to the second network while the turbine is running;

7 is a highly simplified circuit diagram of a combined cycle power plant according to an embodiment of the invention with a gas turbine and a downstream water-steam cycle and

Fig. 8 shows the exemplary internal structure of a matrix converter, as it can be used as an electronic frequency converter in a system according to FIG. 7.

WAYS FOR CARRYING OUT THE INVENTION

FIG. 2 shows a greatly simplified section from a single-line diagram of a power plant according to the prior art. It shows a conventional generator 108, 1 18 driven by at least one turbine whose output power is transmitted via a power plant high-voltage network 5. This network includes high-voltage power lines, a generator circuit breaker 6 with which the generator from the power plant high-voltage network 5 can be separated. The current generated by the generator 108, 1 18 is fed via a (first) step-up transformer 3 and a mains high voltage switch 21 in a (first) network 1. About an auxiliary transformer 42 and a high voltage switch 64, the power plant's own power network consisting of a Medium voltage network 54 and one of these supplied low-voltage network 50 is supplied. The low-voltage network 50 to which smaller loads 51, such as drives, regulators, measuring devices or the regulation are connected, is supplied by the medium-voltage network 54 via at least one auxiliary system transformer 45. Larger consumers, such as NOx

Water pumps or fuel gas compressors are supplied directly from the medium voltage network 54 via their own auxiliary drive transformers.

The generator excitation current is removed from the power plant high-voltage network 5, transformed via exciter transformer 7 to exciter voltage and rectified and regulated in a static exciter 43. By an excitation switch 47, the excitation can be switched on or off.

In generators of a gas turbine, the generator is typically also switched to start as a motor. For this purpose, power from the power plant high-voltage network 5 via transformer and a static frequency converter 63 is supplied with power. Static frequency converter 63 can be connected to or disconnected from generator 108, 118 via a start-up switch 26.

In this and the following example, the output voltage of the generator and correspondingly the network connected to the generator is referred to as the power station's own high-voltage network 5. There are different definitions of low voltage, medium voltage and high voltage. In the example, with a low voltage in the range of 380 V to 415 V,

Medium voltage in the range of 6000 V to 1 1000 V and high voltage greater 21000 V worked. There are different definitions of voltage ranges in the literature. There are definitions where high voltage only starts above 35 kV, 38 kV or even above 69 kV. The names chosen here are not meant to be limiting. FIG. 3 shows a first embodiment of the power plant according to the invention. In contrast to a conventional power plant, the power plant high-voltage network 5 is not connected directly to the generator 8, 18, but via an electronic frequency converter 27th

Typically, two power grids that have different line frequency have different operating voltages. Accordingly, two mains high voltage switches 21 a, b and two Aufspanntransformatoren 3, 4 are provided.

For feeding electricity into the first network 1, the power plant high-voltage network 5 is operated at the first operating frequency and connected via a mains high-voltage switch 21 a and a first step-up transformer 3 to the first network 1.

For feeding electricity into the second network 2, the power plant high-voltage network 5 is operated at the first operating frequency and connected via a mains high-voltage switch 21 b and a second step-up transformer 4 to the second network 2.

An advantage of the invention is that the medium-voltage network 54 and the low-voltage network 50 can be performed with your consumers virtually unchanged and identical to those of a conventional power plant. The power supply of the medium-voltage network 54 itself is dependent on the selected frequency of the power plant high-voltage network 5 either directly via a high voltage switch 64a and the auxiliary transformer 42 or via a high voltage switch 64b, an auxiliary frequency converter 41 and the auxiliary transformer 42nd

If the frequency of the power plant high-voltage network 5 is equal to that of the medium-voltage network 54, the direct introduction of high-voltage switch 64 and the auxiliary transformer 42 is selected. If the Frequency of the power plant high-voltage network 5 is not identical to that of the medium voltage network 54, the introduction of high voltage switch 64, an auxiliary frequency converter 41 and the auxiliary transformer 42 is selected.

In the example shown in FIG. 3, the power plant medium voltage network 54 is designed for 50 Hz. The first network 1 is also 50 Hz and the second network is designed for 60 Hz.

For the introduction of electricity in the first network 1, the power plant. High-voltage network 5 of the electronic frequency converter 27 operated at 50 Hz and introduced current via the first step-up transformer 3 in the first network 1. The medium-voltage network 54 can be supplied directly via the auxiliary transformer 42 with medium voltage in 50 Hz.

Upon introduction of electricity in the second network 2, the power plant.

High-voltage network 5 of the electronic frequency converter 27 operated at 60 Hz and fed power via the second Aufspanntransformator 4 in the second network 2. To supply the medium-voltage network 54, the power of the power plant high-voltage network 5 is converted via the auxiliary frequency converter 41 from 60 Hz to 50 Hz and then introduced via the auxiliary transformer 42 into the medium-voltage network 54.

Since the generator 8, 18 can be operated via the electronic frequency converter 27 for starting the turbine as an electric motor, omitted in the inventive arrangements of the static frequency converter 63 and the associated lines and circuits.

4, a second embodiment of the inventive power plant is shown. It is substantially identical to the embodiment shown in Fig. 3. It is characterized by a special Aufspanntransformator 3, 4, which allows the clamping to two different mains voltages. When introduced into the first network 1, the current with the voltage and frequency of first network tapped from Aufspanntransformator 3.4 and initiated via a mains high voltage switch 21 a. When it is introduced into the second network 2, the current with the voltage and frequency of the second network is picked up by the step-up transformer 3,4 and initiated via a mains high-voltage switch 21b.

In order to prevent an electromagnetic connection between the two networks 1, 2 in this embodiment, the mains high-voltage switch 21 a, b between the networks 1, 2 and the Aufspanntransformator 3, 4 are arranged.

FIG. 5 shows a further embodiment of the power plant according to the invention. It differs from the embodiment shown in FIG. 3 by a cost-optimized power supply of the auxiliary systems. In order to reduce the number of parallel lines and high voltage switches 64, there is only one introduction to the medium voltage network 54 via the auxiliary frequency converter 41, the auxiliary transformer 42 and a medium voltage switch 46. Consequently, the medium voltage network 54 of the power plant is always supplied via the auxiliary frequency converter 41.

The frequency ratio of the auxiliary frequency converter 41 is equal to the ratio of the design frequency of the medium-voltage network 54 to the operating frequency of the power plant high-voltage network. 5

For example, in the event that the electronic frequency converter 27 supplies the power plant high-voltage network 5 with the frequency of the medium-voltage network 54, the frequency ratio of the auxiliary frequency converter 41 is equal to one.

Based on FIG. 3, FIG. 6 shows a further embodiment of the power plant according to the invention. This is characterized in that a switching of the introduction of a first network 1 in a second network 2 is possible without shutting down the turbine. When choosing a matrix converter as electronic frequency converter 27, which is presented as a preferred variant, theoretically, the output frequency can be suddenly switched from a first frequency to a second frequency. The synchronization of the associated mains high voltage switch 21 a, b and high voltage switch 64 a, b with this switching operation and the synchronization of the phases with those of the network and the influence of a sudden switching operation on the grid stability are problematic. Advantageously, the turbine is therefore first blanked down to idle for the switching process, the electronic frequency converter 27 synchronized with the new target network and the turbine then charged again. To enable this without shutting down the turbine, the power supply of the auxiliary systems during the

Switching be guaranteed. This could be ensured, for example, by a power supply from a network 1, 2 that is independent of the generator 8, 18. However, during normal operation, where power is delivered to one of the grids 1, 2, power plants 10 are typically self-powered and corresponding circuits.

To enable a switch from a first network 1 to a second network 2 without shutting down the turbine and to ensure the self-sufficiency of the power plant during normal operation, a division of the high-voltage network 5 is proposed in two parts. As shown in Fig. 6, the first part of the high voltage network 5a connects the generator 8, 18 with the input of the electronic frequency converter 27. Further connects the high voltage network 5a, for example, the output of the electronic frequency converter 27 via mains high voltage switch 21 a, b and the Aufspanntransformatoren 3, 4 optionally with the first network 1 or the second network 2. The second part of the high-voltage network 5b may connect the auxiliary transformer 42 via a high-voltage switch 64a and the first step-up transformer 3 to the first network 1. In addition, the high voltage network 5b may connect the auxiliary transformer 42 to the second network 2 via the auxiliary frequency converter 41, a high voltage switch 64b, and the second step-up transformer 4. The high-voltage network 5b allowed by the mains high voltage switch 21 a, b a complete separation of the Medium voltage network 54 from the high-voltage network 5a of the power plant and the high voltage switch 64a, b, the supply from the first network 1 or from the second network 2. During normal load operation, the supply from the power plant's own high-voltage network 5a, and a combination of supply from different high-voltage networks (1 and 5a or 2 and 5a) are realized.

A method for switching the power supply from the first power grid 1 to the second power grid 2 can be carried out, for example, as follows: Starting from the load operation of the turbine, in which the mains high voltage switch 21 a and the high voltage switch 64 a are closed and the mains high voltage switch 21 b and the high voltage switch 64b are open, the turbine is unloaded. At idle the mains high voltage switch 21 a is opened and the generator 8, 18 disconnected from the mains. The auxiliary systems are now supplied by the first network 1 via the step-up transformer 3, the power plant's own high voltage network, the high voltage switch 64a and the auxiliary transformer 42. For switching to the second network, the high voltage switch 64b is closed and the output of the auxiliary frequency converter 41 is synchronized to the frequency of the first network 1. Once the synchronization has taken place, the power supply of the auxiliary systems can be taken over by the second network 2 and disconnected from the first network 1 by opening the high-voltage switch 64a.

Further, the output current of the electronic frequency converter 27 is synchronized with the frequency of the second network 2. Once this is done, the mains high voltage switch 21 b is closed and charged the turbine. The order of synchronization of auxiliary frequency converter 41 and electronic frequency converter 27 can also be reversed or carried out at the same time. A switchover of the power supply from the second power grid 2 to the first power grid 1 takes place essentially in analogous steps. As far as the frequency control of the medium-voltage network 54 is independent of the frequency of the first network 1 by a separate clock, is at a switching of the supply of the medium voltage network 54 from the second network 2 to a supply by the first network 1 before closing the high-voltage switch 64 a, the output of the auxiliary - Synchronize frequency converter 41 to the first line frequency.

FIG. 7 shows a simplified diagram of a combined cycle power plant as an example of a power plant 10 according to the invention. The turbine train 1 1 with the gas turbine 12 and the first generator 18 and the turbine train 1 1 'of the steam turbine 24 correspond to those in Fig. 1. Both the generator 18 of the gas turbine 12 and the generator 1 of the steam turbine 24 can optionally via the mains high voltage switch 21st a, b are connected to the first network 1 or the second network 2. On the presentation of capacitor, feedwater pumps and other systems of the water steam cycle 25 has also been omitted here for reasons of space.

Preferably, the gas turbine is designed as a gas turbine 12 with sequential combustion. At least one row of adjustable compressor guide vanes at the inlet of the compressor 13 and the regulation of the fuel feed 17 or 17 'to the combustion chambers 15, 15' serve to control or regulate the gas turbine 12. The corresponding control signals come from a control or regulation in accordance with certain input parameters that can be used individually or in selectable combination. Possible parameters are the compressor inlet temperature, the compressor end temperature and the compressor discharge pressure at the compressor outlet. Other common parameters are outlet temperatures of the first and second turbine 14a, 14b. The first and second turbine is cooled by, for example, cooling air 52. The signal exchange between gas turbine 12 and control 39 is shown in simplified form by the signal line 40. The speed of the gas turbine 12 can be measured, for example via the generator frequency at the first generator 18 and entered via a measuring line 48 in the control 39. For measuring the network frequency in the network 1, 2, a Netzfrequenzaufnehmer 49 may be provided. Finally, a value for a target power can be entered into the control 39.

The controller 39 regulates power and speed of the gas turbine 12 and the first generator 18 according to one or more of these parameters or other parameters. Unlike conventional power plants, the

Speed due to the use of the electronic frequency converter 27 regardless of the mains frequency of Netzesi, 2 are regulated.

The regulation of the rotational speed can alternatively also be effected, for example, by transmitting the nominal rotational speed calculated in the control 39 of the gas turbine to the regulator of the electronic frequency converter 27 and imparting the desired rotational speed to the gas turbine 12 via the generator. The first generator 18 is based on the electronic frequency converter 27 against the quasi-static compared to the gas turbine 12 network 1, 2 and forces by regulating the frequency ratio between the network and the mechanical speed of the gas turbine, the target speed. Quasi-static network 1, 2 means in this context that changes in the power frequency due to a change in the speed or of the respective turbine 12 to the network 1, 2 output power are very small and in the control process are negligible or can be easily compensated , This means in particular that an adaptation of the imposed gas turbine speed, a possibly resulting change in the grid frequency is at least an order of magnitude smaller. In general, the resulting change in the line frequency in the noise of the network will be difficult or impossible to measure.

The water-steam circuit 25 is controlled in this example by a water-steam cycle controller 55. The water-steam circuit regulator 55 gets over the signal lines 57 all required to control the boiler 23 operating conditions, such as temperatures, mass flows or positions of valves and pressures of the boiler and sends via the lines 57, the control signals to the boiler 23. Based on the operating conditions of the steam turbine 24, this is also regulated by the water-steam cycle controller 55. The speed of the steam turbine 24 can be measured for example via the generator frequency at the second generator 8 and entered via a measuring line 48 in the water-steam cycle controller 55. For measuring the network frequency in the network 1, 2, a Netzfrequenzaufnehmer 49 may be provided. The control signals are exchanged with the steam turbine 24 via the signal lines 62.

In contrast to conventional power plants, the speed of the steam turbine 24 due to the use of the electronic frequency converter 27 regardless of the mains frequency of Netzesi, 2 are regulated.

The regulation of the rotational speed can alternatively also be effected, for example, by transmitting the nominal rotational speed calculated in the water-steam cycle controller 55 of the steam turbine to the controller of the electronic frequency converter 27 and imparting the desired rotational speed via the generator to the steam turbine 24. The second generator 8 is based on the electronic frequency converter 27 against the quasi-static compared to the steam turbine 24 network 1, 2 and forces by regulating the frequency ratio between the network and mechanical speed of

Steam turbine 24, the target speed. Quasi-static network 1, 2 means in this context that changes in the power frequency as a result of changes in the speed or of the steam turbine 24 to the network 1, 2 output power are very small and in the control process are negligible or can be easily compensated , This means in particular that in an adaptation of the forced steam turbine speed a possibly resulting change in the mains frequency at least one order of magnitude smaller. In general, the resulting change in the line frequency in the noise of the network will be difficult or impossible to measure.

The unit controller 56 performs the higher-level regulation of the power plant 10. He is on the signal lines 58 in signal exchange with the control 39 of the gas turbine 12 and the signal lines 59 in signal exchange with the water-steam circuit controller 55th

In practice, the water-steam cycle is usually not controlled by a water-steam cycle controller 55, but via a series of controllers that communicate with the unit controller 56. These would be for example a controller for the steam turbine, a controller for the boiler or a controller for the auxiliary systems, such as condenser and feedwater pumps.

The electronic frequency converter 27 is - to limit the power loss - preferably designed as a matrix converter without DC intermediate circuit. Such a matrix converter, which operates particularly low loss due to its control, has been described in EP-A2-1 199 794 in structure and in the mode of action. Further details of such a matrix converter have been made in EP-A1-1 561 273, in DE-A1 -10 2004 016 453, DE-A1 -10 2004 016 463 and DE-A1-10 2004 016 464. FIG. 8 shows the block diagram of a matrix converter with 6 input phases and 3 output phases. The matrix converter 27 connects in a time sequence 6 phases G1, .., G6 of a generator 8, 18 as a source with 3 phases L1, .., L3 of a load 30. The power unit 29 required for this purpose comprises 18 bidirectional switches 32 in the form of anti-parallel switched thyristors (in the general case there are mxn switches for m input / source phases and n output / load phases). The switches 32 are arranged in a (6 x 3) matrix. For the control of the switch 32, a controller or a controller 31 is provided which receives from a timer 28 time signals (a clock frequency). The switching state of the switches 32 (ON, OFF) is monitored and over each a first signal line 36 is reported to the controller 31. The switches 32 are each controlled by the controller 31 via a control line 35.

In the individual phases G1, .., G6 of the generator 8, 18, a current measuring device 34 is in each case arranged, which signals the sign of the phase current via a second signal line 37 to the controller 31. Furthermore, between the phases G1, .., G6 of the generator 8, 18th

Voltage measuring means 33 are arranged, which signal the sign of the respective phase difference voltage via a third signal line 38 to the controller 31. For details of the operation of the matrix converter, refer to the above mentioned. References directed.

The possible embodiments of the invention are not limited to the examples presented here. Based on the examples, the person skilled in the art will be able to realize a multitude of possibilities for equivalent circuits and methods. In particular, in the arrangement of switches and high voltage switches, a large number of combinations is possible. In addition, safety switches and a large part of the auxiliary systems are not shown for the sake of simplicity. Further, the application is not limited to the type or combination shown here. In particular, the application is not on the

Limited use in combined cycle power plants. An application for gas turbine or steam turbine power plants is also possible. For example, an application in combination with water turbines is conceivable.

LIST OF REFERENCE NUMBERS

1 first network 2 second network

3 first step-up transformer

4 second step-up transformer 5, 5a, b power plant high-voltage network

6 generator circuit breaker

7 exciter transformer

8 second generator

9 shaft of the steam turbine

10,10 'power plant

1 1, 1 1 'shaft train

12 gas turbine

13 compressors

14,14a, b Turbine

15.15 'combustion chamber

16 air intake

17,17 'fuel supply

18 first generator

19 wave

20 network connection (frequency-coupled)

21, 21 a, b mains high voltage switch

22 exhaust outlet

23 heat recovery steam generator

24 steam turbine

25 water-steam cycle

26 start-up counter

27 Electronic frequency converter

28 clocks

29 power section

30 load

31 controllers

32 switches (bidirectional)

33 tension measuring device

34 current measuring device

35 control line

36, .., 38 signal line 39 regulation

40 Measured value and signal exchange control to gas turbine

41 auxiliary frequency converter

42 auxiliary transformer 43 static excitation

44 auxiliary drive transformer

45 auxiliary system transformer

46 medium voltage switch

47 excitation switch 48 measuring line (generator frequency / speed)

49 mains frequency sensors

50 low voltage supply

51 low-voltage consumers as continuous

DC power supply, drives, controllers, measuring devices 52 Cooling air supply

54 medium voltage network

55 water steam cycle regulator

56 unit controllers

57 Measured Values and Control Signals Heat Recovery Steam Generators 58 Control Signals Gas Turbine Control / Unit Controller

59 Control signals Water-steam cycle controller / unit controller

61 exhaust

62 Measured value and control signal exchange Controller for water / steam cycle 63 Static start-up device including transformer

64, 64a, b High voltage switch

108 conventional second generator

1 18 conventional first generator

G1, .., G6 phase (generator) L1, .., L3 phase (load)

Claims

1. Power plant (10) comprising a turbine (12) and a turbine (12) directly driven, alternating current with an operating frequency generating generator (18), characterized in that the generator (8, 18) via a frequency converter (27) and at least one step-up transformer (3, 4) is selectively connectable to a first electrical network (1) having a first operating frequency or a second electrical network (2) to a second operating frequency.

Second power plant (10) according to claim 1, characterized in that from the at least one step-up transformer (27) when connected to the first electrical network (1) a first voltage ratio between the generator (8, 18) and the first network (1) is tapped and when connected to the second network (2) a second voltage ratio between the generator (8, 18) and the second network (2) is tapped.

3. Power plant (10) according to claim 1, characterized in that for the connection to the first electrical network (1), a first Aufspanntransformator (3) with a first voltage ratio between the generator and the first network (1) is arranged and for the connection a second step-up transformer (4) having a second voltage ratio between the generator (8, 18) and the second network (2) is arranged with the second network (2).

4. Power plant (10) according to one of claims 1 to 3, characterized in that the frequency converter (27) is designed as a matrix converter.

5. Power plant (10) according to one of claims 1 to 4, characterized in that the power plant (10) has at least one local medium voltage network (54) which is designed for an input frequency, wherein at least one auxiliary transformer (42) for supplying the at least one medium-voltage network (54) either directly or via an auxiliary frequency converter (41) to the output of the frequency converter (27) is connectable.

6. Power plant (10) according to one of claims 1 to 4, characterized in that the power plant (10) has at least one local medium voltage network (54), wherein at least one auxiliary transformer (42) for supplying the at least one medium voltage network (54) directly with the first Aufspanntransformator (3) and / or via an auxiliary frequency converter (41) with the second Aufspanntransformator (4) is connectable.

7. Power plant (10) according to one of claims 1 to 6, characterized in that at least two wave strands (1 1, 1 1 ') each having at least one generator (8, 18) are arranged, each of the generators (8, 18) via a frequency converter (27), at least one

Mains voltage switch (21) and at least one Aufspanntransformator (3, 4) either to the first electrical network (1) with the first operating frequency or the second electrical network (2) with the second operating frequency is connectable.

8. Power plant (10) according to claim 7, characterized in that the power plant (10) is designed as a combined cycle power plant with at least one gas turbine (12) and at least one steam turbine (24), wherein the generators (8,18) of these turbines (12 , 24) are arranged independently of one another selectively connectable to the first network (1) or to the second network (2).

9. A method for operating a power plant (10) according to any one of claims 1 to 8, characterized in that the frequency converter (27) for feeding into the first power grid (1) is driven so that it generates an output current at the first power frequency, wherein the frequency converter (27) via the first step-up transformer (3) to the first power grid (1) is connected or that the frequency converter (27) for feeding into the second power network (2) is driven so that it has an output current with the second

Mains frequency generated, wherein the frequency converter (27) via the second step-up transformer (4) to the second power grid (2) is connected.

10. A method for operating a power plant (10) according to claim 9, characterized in that when connecting the frequency converter (27) to the first network (1), the local medium voltage network (54) for supplying the auxiliary systems of the power plant via an auxiliary transformer (42). supplied by the high voltage network (5), and that when connected to the second network (2) the local medium voltage network (54) for supplying the auxiliary systems of the power plant via an auxiliary frequency converter (41) and the auxiliary transformer (42) is connected.

1 1. A method for operating a power plant (10) according to claim 9, characterized in that when connecting the frequency converter (27) to the first network (1), the local medium voltage network (54) for supplying the auxiliary systems of the power plant via an auxiliary frequency converter (41) which is so controlled that the input and output frequencies are equal, and that when connected to the second network (2) the local medium voltage network (54) for supplying the auxiliary systems of the power plant via an auxiliary frequency converter (41) is connected, which is controlled so that the output frequency is equal to the first frequency.

12. A method for operating a power plant (10) according to any one of claims 9 to 1 1, characterized in that for switching from an introduction into the first network (1) on an introduction into the second network (2) or vice versa, the turbine is unloaded and the generator switch (6) is opened, then the frequency converter (27) is synchronized to the new mains frequency, the generator switch (6) is closed and then the turbine is charged again.

13. A method for operating a power plant (10) according to claim 12, characterized in that the auxiliary transformer (42) for supplying the auxiliary systems during the switching phase via the first Aufspanntransformator (3) directly from the first network (1) are supplied with power and parallel via the second step-up transformer (4) and auxiliary frequency converter (41) is supplied with power.

14. A method for operating a power plant (10) according to claim 13, characterized in that before the parallel interconnection of the power supplies of the auxiliary systems, the output frequency of the auxiliary frequency converter (42) to the frequency of the first network (1) is synchronized.

15. A method for operating a gas turbine (12) of a power plant (10) according to one of claims 9 to 14, characterized in that the start of the gas turbine (12) the power plant high-voltage network (5) either with the first network (1) or second network (2) is connected, the generator (8) is operated as a starter motor and is controlled by the frequency converter (27).