Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
  • H02J3/02—Circuit arrangements for AC mains or AC distribution networks using a single network for simultaneous distribution of power at different frequencies; using a single network for simultaneous distribution of AC power and of DC power
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers

Definitions

• 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.
• 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.
• FIG. 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 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 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.”
• the steam turbine 24 can also drive its own second generator 108 on a separate shaft train 1 1 ', as shown in FIG
• 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.
• 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.
• 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.
• 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.
• 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.
• at least one step-up transformer from which either two voltages can be tapped, may be used to connect to the electrical networks.
• a first voltage ratio and for connection to the second network a second voltage ratio is tapped.
• 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.
• 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.
• new circuits and methods for operating the power plant are proposed.
• 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.
• 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.
• 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.
• 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.
• the second network frequency is 50 Hz or 60 Hz.
• Mains frequency is 60 Hz and the first mains frequency is 50 Hz.
• the first mains frequency is greater than the second mains frequency, the second mains frequency being 50 Hz or 60 Hz.
• the second mains frequency can be 50 Hz and the first mains frequency is 60 Hz.
• the turbine is designed for a power greater than 50 MW.
• matrix converters By using matrix converters, the power losses can be kept small
• frequency converters 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.
• 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
• Fig. 3 is a greatly simplified section of a single-line diagram of a power plant according to a
• FIG. 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
• FIG. 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;
• FIG. 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;
• FIG. 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.
• 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.
• 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.
• an excitation switch 47 the excitation can be switched on or off.
• the generator 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.
• 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.
• 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,
• FIG. 3 shows a first embodiment of the power plant according to the invention.
• the power plant high-voltage network 5 is not connected directly to the generator 8, 18, but via an electronic frequency converter 27th
• 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.
• the power plant high-voltage network 5 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.
• 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
• 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.
• 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.
• 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.
• the power plant Upon introduction of electricity in the second network 2, the power plant.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• the medium voltage network 54 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
• the frequency ratio of the auxiliary frequency converter 41 is equal to one.
• 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.
• a matrix converter as electronic frequency converter 27
• 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.
• 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.
• the high-voltage network 5 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.
• 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 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.
• 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.
• 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.
• 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.
• feedwater pumps and other systems of the water steam cycle 25 has also been omitted here for reasons of space.
• 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.
• a measuring line 48 in the control 39 For measuring the network frequency in the network 1, 2, a Netzfrequenzauf choir 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
• 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 ,
• 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.
• a Netzfrequenzaufêt 49 may be provided for measuring the network frequency in the network 1, 2, a Netzfrequenzaufsacrificing 49 may be provided.
• the control signals are exchanged with the steam turbine 24 via the signal lines 62.
• 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
• 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
• 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.
• controllers that communicate with the unit controller 56.
• controllers 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.
• 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.
• 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.
• 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.
• the controller 31 For details of the operation of the matrix converter, refer to the above mentioned. References directed.
• excitation switch 48 measuring line (generator frequency / speed)
• G1 .., G6 phase (generator) L1, .., L3 phase (load)

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Control Of Eletrric Generators (AREA)
• Supply And Distribution Of Alternating Current (AREA)

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• 2008
  • 2008-08-15 CH CH01286/08A patent/CH699321A1/de not_active Application Discontinuation
• 2009
  • 2009-08-12 BR BRPI0917652-7A patent/BRPI0917652B1/pt not_active IP Right Cessation
  • 2009-08-12 WO PCT/EP2009/060438 patent/WO2010018194A2/de not_active Ceased
  • 2009-08-12 JP JP2011522510A patent/JP5627584B2/ja active Active

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