US20150292469A1 - Electric unit for a pump-storage power plant - Google Patents
Electric unit for a pump-storage power plant Download PDFInfo
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- US20150292469A1 US20150292469A1 US14/384,120 US201314384120A US2015292469A1 US 20150292469 A1 US20150292469 A1 US 20150292469A1 US 201314384120 A US201314384120 A US 201314384120A US 2015292469 A1 US2015292469 A1 US 2015292469A1
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- Prior art keywords
- frequency converter
- electric unit
- synchronous machine
- electric
- transformer
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03B—MACHINES OR ENGINES FOR LIQUIDS
- F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
- F03B13/06—Stations or aggregates of water-storage type, e.g. comprising a turbine and a pump
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D19/00—Starting of machines or engines; Regulating, controlling, or safety means in connection therewith
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
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- 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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- 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
- H02J3/40—Synchronising a generator for connection to a network or to another generator
- H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
- H02K7/1807—Rotary generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P1/00—Arrangements for starting electric motors or dynamo-electric converters
- H02P1/16—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters
- H02P1/46—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters for starting an individual synchronous motor
- H02P1/52—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters for starting an individual synchronous motor by progressive increase of frequency of supply to motor
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/022—Synchronous motors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/022—Synchronous motors
- H02P25/024—Synchronous motors controlled by supply frequency
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
- H02P27/14—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation with three or more levels of voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/04—Control effected upon non-electric prime mover and dependent upon electric output value of the generator
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/08—Control of generator circuit during starting or stopping of driving means, e.g. for initiating excitation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/20—Hydro energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/16—Mechanical energy storage, e.g. flywheels or pressurised fluids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P80/00—Climate change mitigation technologies for sector-wide applications
- Y02P80/10—Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
Definitions
- the invention relates to a pumped-storage power plant, in particular to an electric unit therefor, comprising a converter and a rotating electric synchronous machine, wherein the machine is provided in a cavern.
- Regenerative energy sources such as, for example, wind energy and solar energy provide a continuously increasing proportion of the electricity demand. These energy sources do have discontinuous operating times, however. Therefore, a direct and permanent supply of electricity to consumers from these energy sources cannot be ensured. For this, energy stores need to be used which enable rapid changes between a surplus of electricity and a deficit of electricity and whose power and energy flow direction can be changed quickly and continuously.
- energy stores there are different system available as energy stores which are in each case particularly suitable for specific quantities of energy and application cases.
- kinetic stores for example flywheels
- electrochemical stores batteries, redox flow cells
- electromagnetic stores capacitor, supercapacitors, superconducting coils
- thermodynamic stores compressed-air stores, electrothermic stores
- pumped stores are used for large quantities of energy of typically over 100 MWh and usually over 1 GWh.
- Modern pumped stores have variable-speed drives. By decoupling the speed of the machines from a grid frequency, rotational speeds of the pumps and turbines can be set such that they are operated close to optimum efficiency. In addition, the variation in the speed during pump operation makes it possible to freely adjust the power consumption. In particular, systems with a variable speed can be connected to or synchronized with the grid quickly from a standstill.
- Pumped stores in accordance with the prior art have double-fed asynchronous machines and power electronics frequency converters, whereby speed regulation of a pump and a turbine is possible.
- a stator of the double-fed asynchronous machine is connected directly to the electric grid with a grid frequency.
- a rotor of the double-fed asynchronous machine is connected to the grid via a frequency transformer and can therefore have a variable frequency.
- a pump power is regulated and secondly the efficiency of the system can be increased, if required.
- pumped stores provision is often made for the machine equipment such as, for example, turbines, pumps and motor generators, to be accommodated in a cavern introduced into rock, in a cavity or in a closed area beneath the second storage basin, for example.
- Another form of pumped store provides pump, turbine and motor generator at the lower end of a shaft, wherein further power plant components are provided above ground in a building or likewise in the shaft, for example.
- the converters according to the prior art used in this connection typically have an output voltage of 3 to 6 kV. In contrast, in the case of the electric machine, a voltage of 10 to 21 kV is usually used. Therefore, it is necessary to provide a power transformer between an output of the converter and terminals of the machine, which power transformer bypasses the respective voltage differences.
- the high currents in this case require that the transformer is provided in the direct vicinity of the machine, that is to say within the cavern.
- An essential disadvantage of this arrangement with a double-fed asynchronous machine is an increased requirement on space within the cavern, as a result of which costs for erecting the pump-storage power plant and digging the cavern are significantly increased.
- the transformer has losses of the order of 1-2% of the transferred active power.
- the use of a transformer is disadvantageous owing to the high costs of the transformer.
- a transformer has a considerable risk of explosion owing to transformer oils and therefore represents a considerable safety risk.
- a further disadvantage of converters according to the prior art is that the voltage difference is overcome in one or two stages or steps.
- the high and steep voltage steps require smoothing or filtering in order not to overload an electrical isolation of the transformers which are directly coupled to the frequency converter, and the machine, and to avoid damage to the isolation.
- a smoothing or filtering arrangement is expensive, causes further losses of the active power and requires lots of space.
- the transferred power has a large harmonic component which harmonics cause additional losses in the machine and in the connected transformers.
- the present invention is based on the object of simplifying the erection, operation and maintenance of a pumped-storage power plant and increasing the efficiency.
- the invention relates to an electric unit for a pumped-storage power plant, wherein said electric unit is connectable to an electric grid.
- the electric unit in this case comprises at least one frequency converter and a rotating electric synchronous machine, which acts as motor or generator depending on a type of operation of the machine.
- the machine is mechanically connectable, for example, to a water turbine and a water pump or a reversible pump turbine.
- the converter is designed in this case as a modular multilevel converter MMC and is directly connected to the machine, that is to say without an intermediately connected transformer, wherein the converter has an adjustable voltage.
- At least the electric machine is provided in a cavern, in a shaft or in a closed area beneath the tailwater level.
- the converter has a multiplicity of series-connected unit cells for scaling an output voltage.
- the unit cells each have, for example, a capacitor or an inductor.
- the unit cells are separately controllable, for example for adapting the output voltage to the electric machine.
- edge steepness and amplitude of pulses between an output of the converter and the machine, for example terminals of the machine, is limitable to relieve the isolation.
- a multiplicity of voltage steps for example small steps, can be used to modify the output voltage.
- Another embodiment provides that the output voltage has low harmonic distortion, such that the grid connection conditions are fulfilled without additional filtering and no differences emerge in the case of configuration of the machine with respect to harmonics compared to a direct connection to the grid.
- grid connection conditions are defined, for example, in a grid code.
- the converter is connected on the grid-side to a generator transformer.
- the invention simplifies the erection of a pumped-storage power plant, in particular in the case of an underground construction, for example in a rock cavern, by sparing a transformer between machine and converter. Furthermore, active power losses of the omitted transformer are saved and the electric unit has a higher efficiency.
- FIG. 1 shows a schematic illustration of an electric unit comprising a converter, an electric synchronous machine and a generator transformer.
- FIG. 1 shows a schematic illustration of an electric unit 1 connected to an electric grid 2 .
- the electric unit 1 in this case comprises a modular multilevel converter 3 and a rotating electric synchronous machine 4 .
- the machine 4 is in this case accommodated in a cavern.
- a generator transformer 5 is provided in this embodiment to connect the electric unit to the electric grid 2 .
- a frequency conversion is produced by means of a combination of a rectifier and an inverter, which are connected to one another via a concentrated or distributed voltage DC link or current DC link.
- the DC link in this case furthermore has units for energy storage, for example capacitors in the case of a voltage DC link and inductances in the case of a current DC link.
- the operation of the machine at a freely selectable speed has considerable advantages.
- an established, reliable and low-maintenance generator technology can be used.
- the synchronous machine 4 By virtue of the use of the synchronous machine 4 , high speeds can be achieved for high drops, for example, in particular even at high powers.
- the speed range which can be achieved during operation continuously ranges from zero to the maximum speed and is only restricted by the operational limits of the pump and the turbine.
- the pump and the turbine can in principle be combined in one unit, for example a pump turbine.
- a further advantage consists in very quick grid coupling and the possibility of generating positive and negative reactive power in the converter 3 , in order that the generator can be operated exclusively with active power, as a result of which said generator has a more compact design. Furthermore, owing to the use of the converter 3 , it is possible to switch over quickly from pump to turbine operation, for example.
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Control Of Eletrric Generators (AREA)
- Supply And Distribution Of Alternating Current (AREA)
- Control Of Ac Motors In General (AREA)
- Rectifiers (AREA)
- Control Of Non-Positive-Displacement Pumps (AREA)
- Motor And Converter Starters (AREA)
Abstract
A pumped-storage power plant is disclosed, such as an electric unit having a converter and a rotating electric synchronous machine. The converter is designed as a modular multilevel converter and the machine is directly connectable to the converter, wherein the converter has an adjustable voltage.
Description
- The invention relates to a pumped-storage power plant, in particular to an electric unit therefor, comprising a converter and a rotating electric synchronous machine, wherein the machine is provided in a cavern.
- Regenerative energy sources such as, for example, wind energy and solar energy provide a continuously increasing proportion of the electricity demand. These energy sources do have discontinuous operating times, however. Therefore, a direct and permanent supply of electricity to consumers from these energy sources cannot be ensured. For this, energy stores need to be used which enable rapid changes between a surplus of electricity and a deficit of electricity and whose power and energy flow direction can be changed quickly and continuously.
- In this case, there are different system available as energy stores which are in each case particularly suitable for specific quantities of energy and application cases. For low quantities of energy up to approximately 20 MWh, kinetic stores (for example flywheels), electrochemical stores (batteries, redox flow cells) or electromagnetic stores (capacitors, supercapacitors, superconducting coils) are preferably used, depending on the application. For medium quantities of energy of up to a few 100 MWh, in principle thermodynamic stores (compressed-air stores, electrothermic stores) are particularly well suited. For large quantities of energy of typically over 100 MWh and usually over 1 GWh, pumped stores are used.
- Pumped stores or pumped-storage power plants are of particular interest owing to the large amount of energy that can be stored. In this case, with surplus electricity water is pumped from a first natural storage basin or storage basin set up artificially for this purpose into a second storage basin positioned higher. In the process, the electrical energy is converted into potential energy. In order to recover electricity, water is directed from the higher storage basin via a turbine back into the lower storage basin. For this system, minimization of the losses in the conversion processes is particularly important.
- Modern pumped stores have variable-speed drives. By decoupling the speed of the machines from a grid frequency, rotational speeds of the pumps and turbines can be set such that they are operated close to optimum efficiency. In addition, the variation in the speed during pump operation makes it possible to freely adjust the power consumption. In particular, systems with a variable speed can be connected to or synchronized with the grid quickly from a standstill.
- Pumped stores in accordance with the prior art have double-fed asynchronous machines and power electronics frequency converters, whereby speed regulation of a pump and a turbine is possible. In this case, a stator of the double-fed asynchronous machine is connected directly to the electric grid with a grid frequency. A rotor of the double-fed asynchronous machine is connected to the grid via a frequency transformer and can therefore have a variable frequency. Thus, firstly a pump power is regulated and secondly the efficiency of the system can be increased, if required.
- In the case of pumped stores, provision is often made for the machine equipment such as, for example, turbines, pumps and motor generators, to be accommodated in a cavern introduced into rock, in a cavity or in a closed area beneath the second storage basin, for example. Another form of pumped store provides pump, turbine and motor generator at the lower end of a shaft, wherein further power plant components are provided above ground in a building or likewise in the shaft, for example.
- This way of accommodating the machine equipment is a consequence of the circumstance whereby the turbines need to be positioned sufficiently below the lower storage basin in order to avoid cavitation. For space and geometry reasons, this is usually only possible by virtue of a powerhouse for accommodating the machine equipment being built underground. Furthermore, an underground design provides protection against environmental influences such as descents of avalanches, for example. Furthermore, for environmental protection or landscape protection reasons, an underground design is likewise often used.
- The converters according to the prior art used in this connection typically have an output voltage of 3 to 6 kV. In contrast, in the case of the electric machine, a voltage of 10 to 21 kV is usually used. Therefore, it is necessary to provide a power transformer between an output of the converter and terminals of the machine, which power transformer bypasses the respective voltage differences. The high currents in this case require that the transformer is provided in the direct vicinity of the machine, that is to say within the cavern.
- An essential disadvantage of this arrangement with a double-fed asynchronous machine is an increased requirement on space within the cavern, as a result of which costs for erecting the pump-storage power plant and digging the cavern are significantly increased. Moreover, the transformer has losses of the order of 1-2% of the transferred active power. Overall, the use of a transformer is disadvantageous owing to the high costs of the transformer. Furthermore, a transformer has a considerable risk of explosion owing to transformer oils and therefore represents a considerable safety risk.
- A further disadvantage of converters according to the prior art is that the voltage difference is overcome in one or two stages or steps. As a result of this, firstly, the high and steep voltage steps require smoothing or filtering in order not to overload an electrical isolation of the transformers which are directly coupled to the frequency converter, and the machine, and to avoid damage to the isolation. A smoothing or filtering arrangement is expensive, causes further losses of the active power and requires lots of space. Secondly, the transferred power has a large harmonic component which harmonics cause additional losses in the machine and in the connected transformers.
- Against this background, the present invention is based on the object of simplifying the erection, operation and maintenance of a pumped-storage power plant and increasing the efficiency.
- This object is achieved by an electric unit for a pumped-storage power plant as claimed in claim 1. Further advantageous configurations result from the dependent claims, wherein back-references in the claims do not exclude any other expedient combinations of claims.
- The invention relates to an electric unit for a pumped-storage power plant, wherein said electric unit is connectable to an electric grid. The electric unit in this case comprises at least one frequency converter and a rotating electric synchronous machine, which acts as motor or generator depending on a type of operation of the machine. The machine is mechanically connectable, for example, to a water turbine and a water pump or a reversible pump turbine. The converter is designed in this case as a modular multilevel converter MMC and is directly connected to the machine, that is to say without an intermediately connected transformer, wherein the converter has an adjustable voltage.
- In an advantageous configuration of the invention, at least the electric machine is provided in a cavern, in a shaft or in a closed area beneath the tailwater level.
- In another advantageous embodiment, the converter has a multiplicity of series-connected unit cells for scaling an output voltage. The unit cells each have, for example, a capacitor or an inductor. Furthermore, the unit cells are separately controllable, for example for adapting the output voltage to the electric machine.
- In a particularly advantageous embodiment, provision is made that edge steepness and amplitude of pulses between an output of the converter and the machine, for example terminals of the machine, is limitable to relieve the isolation.
- In another advantageous embodiment, a multiplicity of voltage steps, for example small steps, can be used to modify the output voltage.
- Another embodiment provides that the output voltage has low harmonic distortion, such that the grid connection conditions are fulfilled without additional filtering and no differences emerge in the case of configuration of the machine with respect to harmonics compared to a direct connection to the grid. Such grid connection conditions are defined, for example, in a grid code.
- In one embodiment of the invention, provision is made that the converter is connected on the grid-side to a generator transformer.
- Accordingly, the invention simplifies the erection of a pumped-storage power plant, in particular in the case of an underground construction, for example in a rock cavern, by sparing a transformer between machine and converter. Furthermore, active power losses of the omitted transformer are saved and the electric unit has a higher efficiency.
- Further features, details and advantages of the invention result from the wording of the claims and from the description of exemplary embodiments on the basis of the figure.
- The invention will be explained in more detail on the basis of the following text with reference to preferred exemplary embodiments using the figure, in which
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FIG. 1 shows a schematic illustration of an electric unit comprising a converter, an electric synchronous machine and a generator transformer. - The reference symbols and the significance thereof are summarized in the list of reference symbols. In general, the same reference symbols denote the same parts.
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FIG. 1 shows a schematic illustration of an electric unit 1 connected to an electric grid 2. The electric unit 1 in this case comprises a modularmultilevel converter 3 and a rotating electric synchronous machine 4. The machine 4 is in this case accommodated in a cavern. In addition a generator transformer 5 is provided in this embodiment to connect the electric unit to the electric grid 2. - A frequency conversion is produced by means of a combination of a rectifier and an inverter, which are connected to one another via a concentrated or distributed voltage DC link or current DC link. The DC link in this case furthermore has units for energy storage, for example capacitors in the case of a voltage DC link and inductances in the case of a current DC link.
- The operation of the machine at a freely selectable speed has considerable advantages. In particular in the embodiment with a frequency converter and a synchronous machine, an established, reliable and low-maintenance generator technology can be used. Furthermore, there is the possibility of operating a pump and a turbine independently of one another in the optimum speed range of said pump and turbine. By virtue of the use of the synchronous machine 4, high speeds can be achieved for high drops, for example, in particular even at high powers. Furthermore, the speed range which can be achieved during operation continuously ranges from zero to the maximum speed and is only restricted by the operational limits of the pump and the turbine. The pump and the turbine can in principle be combined in one unit, for example a pump turbine. In particular, there is the possibility of retrofitting older systems for variable frequency operation without replacing the existing generator. A further advantage consists in very quick grid coupling and the possibility of generating positive and negative reactive power in the
converter 3, in order that the generator can be operated exclusively with active power, as a result of which said generator has a more compact design. Furthermore, owing to the use of theconverter 3, it is possible to switch over quickly from pump to turbine operation, for example. - 1 Electric unit
- 2 Electric grid
- 3 Converter
- 4 Electric synchronous machine
- 5 Generator transformer
Claims (12)
1. An electric unit for a pumped-storage power plant, connectable to an electric grid (2) and comprising:
a frequency converter; and
a rotating electric synchronous machine, wherein the synchronous machine is configured for connection to a water turbine and a water pump;
wherein the frequency converter is configured as a modular multilevel converter, and
the synchronous machine is directly connected to the frequency converter;
wherein the frequency converter has is configured to provide an adjustable output voltage, to the synchronous machine which is identical to an input voltage of the machine.
2. The electric unit as claimed in claim 1 , in combination with a pumped-storage power plant, wherein at least the electric synchronous machine is provided in a cavern, in a shaft or in a closed area beneath a tailwater basin of the pumped-storage power plant.
3. The electric unit as claimed in claim 1 , wherein the frequency converter comprises:
plural series-connected unit cells for adjusting the output voltage by scaling, wherein the unit cells are separately controllable.
4. The electric unit as claimed in claim 3 , comprising:
a transformer, wherein the individual unit cells are configured to be controllably switched, an edge steepness and amplitude of a pulse generated by switching of the individual unit cells between an output of the frequency converter and the synchronous machine and the transformer being limitable to such an extent that, even without additional filter elements, no increased demands on isolation of the synchronous machine and the transformer exist.
5. The electric unit as claimed in claim 1 , wherein the frequency converter is configured such that plural a voltage steps will modify an output voltage of the frequency converter.
6. The electric unit as claimed in claim 1 , wherein the output voltage will have limited harmonic distortion such that grid connection conditions will be fulfilled without additional filtering and no differences emerge for a configuration of the synchronous machine with respect to harmonics when compared to a direct connection to the grid.
7. The electric unit as claimed in claim 1 , comprising:
a generator transformer which is connected on a grid-side of the electric unit to the frequency converter.
8. The electric unit as claimed in claim 2 , wherein the frequency converter comprises:
plural series-connected unit cells for adjusting the output voltage by scaling, wherein the unit cells are separately controllable.
9. The electric unit as claimed in claim 8 , comprising:
a transformer, wherein the individual unit cells are configured to be controllably switched, an edge steepness and amplitude of a pulse generated by switching of the individual unit cells between an output of the frequency converter and the synchronous machine and the transformer being limitable to such an extent that, even without additional filter elements, no increased demands on isolation of the synchronous machine and the transformer exist.
10. The electric unit as claimed in claim 9 , wherein the frequency converter is configured such that plural voltage steps will modify an output voltage of the frequency converter.
11. The electric unit as claimed in claim 10 , wherein the output voltage will have limited harmonic distortion such that grid connection conditions will be fulfilled without additional filtering and no differences emerge for a configuration of the synchronous machine with respect to harmonics when compared to a direct connection to the grid.
12. The electric unit as claimed in claim 8 , comprising:
a generator transformer which is connected on a grid-side of the electric unit to the frequency converter.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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EP12158786.9 | 2012-03-09 | ||
EP12158786 | 2012-03-09 | ||
PCT/EP2013/054862 WO2013132099A2 (en) | 2012-03-09 | 2013-03-11 | Electric unit for a pump-storage power plant |
Publications (1)
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US20150292469A1 true US20150292469A1 (en) | 2015-10-15 |
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US14/384,128 Active US9657709B2 (en) | 2012-03-09 | 2013-03-11 | Method for using an electric unit |
US14/384,120 Abandoned US20150292469A1 (en) | 2012-03-09 | 2013-03-11 | Electric unit for a pump-storage power plant |
US14/384,071 Active US9683540B2 (en) | 2012-03-09 | 2013-03-11 | Electric unit for a pumped-storage power plant having components within and outside of an underground cavern |
US14/384,067 Abandoned US20150048623A1 (en) | 2012-03-09 | 2013-03-11 | Method for operating an electric unit for a pumped-storage power plant |
Family Applications Before (1)
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US14/384,128 Active US9657709B2 (en) | 2012-03-09 | 2013-03-11 | Method for using an electric unit |
Family Applications After (2)
Application Number | Title | Priority Date | Filing Date |
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US14/384,071 Active US9683540B2 (en) | 2012-03-09 | 2013-03-11 | Electric unit for a pumped-storage power plant having components within and outside of an underground cavern |
US14/384,067 Abandoned US20150048623A1 (en) | 2012-03-09 | 2013-03-11 | Method for operating an electric unit for a pumped-storage power plant |
Country Status (5)
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US (4) | US9657709B2 (en) |
EP (4) | EP2823557B2 (en) |
JP (4) | JP2015509698A (en) |
CN (4) | CN104145390B (en) |
WO (7) | WO2013132100A2 (en) |
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JP2015509698A (en) * | 2012-03-09 | 2015-03-30 | アーベーベー テクノロジー アクチエンゲゼルシャフトABB Technology AG | How to use the electrical unit |
CN104410172A (en) * | 2014-11-28 | 2015-03-11 | 国家电网公司 | Pumped storage system based on DC generator motor |
CN104600726B (en) * | 2014-11-28 | 2017-02-22 | 国家电网公司 | Light-duty direct-current transmission based water pumping energy storage system |
BR112019003817A2 (en) * | 2017-06-29 | 2019-05-21 | K. Obermeyer Henry | improved installation of reversible turbine pump |
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DE102018109926B4 (en) * | 2018-04-25 | 2019-12-19 | Dr. Ing. H.C. F. Porsche Aktiengesellschaft | Electrical arrangement |
AU2021254256B2 (en) | 2020-04-09 | 2024-06-06 | RCAM Technologies, Inc. | Marine-pumped hydroelectric energy storage |
US11685604B2 (en) | 2021-09-17 | 2023-06-27 | William Taggart, IV | Underground energy storage systems |
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