Classifications

• • 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
  • F03D—WIND MOTORS
  • F03D9/00—Adaptations of wind motors for special use; Combinations of wind motors with apparatus driven thereby; Wind motors specially adapted for installation in particular locations
  • F03D9/20—Wind motors characterised by the driven apparatus
  • F03D9/25—Wind motors characterised by the driven apparatus the apparatus being an electrical generator
  • F03D9/255—Wind motors characterised by the driven apparatus the apparatus being an electrical generator connected to electrical distribution networks; Arrangements therefor
• • 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
  • F03D—WIND MOTORS
  • F03D9/00—Adaptations of wind motors for special use; Combinations of wind motors with apparatus driven thereby; Wind motors specially adapted for installation in particular locations
  • F03D9/20—Wind motors characterised by the driven apparatus
  • F03D9/25—Wind motors characterised by the driven apparatus the apparatus being an electrical generator
• • 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
  • H02J3/381—Dispersed generators
• • 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
• • 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
  • H02P9/44—Control of frequency and voltage in predetermined relation, e.g. constant ratio
• • 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
  • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
  • H02J2300/20—The dispersed energy generation being of renewable origin
  • H02J2300/28—The renewable source being wind energy
• • 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
  • H02K7/1823—Rotary generators structurally associated with turbines or similar engines
  • H02K7/183—Rotary generators structurally associated with turbines or similar engines wherein the turbine is a wind turbine
  • H02K7/1838—Generators mounted in a nacelle or similar structure of a horizontal axis wind turbine
• • 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
  • H02P2101/00—Special adaptation of control arrangements for generators
  • H02P2101/15—Special adaptation of control arrangements for generators for wind-driven turbines
• • 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
  • Y02E10/70—Wind energy
  • Y02E10/72—Wind turbines with rotation axis in wind direction
• • 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
  • Y02E10/70—Wind energy
  • Y02E10/76—Power conversion electric or electronic aspects

Definitions

• This invention relates to a wind power plant comprising at least one wind power station, which includes a wind turbine, an electric generator driven by this wind turbine, and an electric alternating voltage connection connecting the wind power station with a transmission network or distribution network.
• the invention also relates to a method for control in such a wind power plant.
• the invention is preferably intended to be used in such cases where the connection between the generator and the transmission or distribution network includes a cable intended to be submerged into water. Consequently, expressed in other words, it primarily relates to such applications where one or several wind turbines with associated generators are intended to be placed in seas or lakes, wherein the cable connection extends to the transmission or distribution network placed on land.
• the invention can, however, also imply advantages in cases where the wind turbines and the generators are located on land and the connection, which in that case not nec- essarily has to consist of a cable but instead can be realized in the form of aerial lines or cables, connects several such wind turbines/generators with the transmission or distribution network.
• the voltage variation may not be more than 4%. Different countries have different regulations and as a rule the regulations are mitigated in case of a lower voltage level on the transmission line. Voltage variations couid also have to be treated differently depending on time intervals. Rapid voltage variations causes "flicker”, i.e. light variations in glow lamps, which is regulated in rules.
• a solution, lying at the side of the present invention, concerning the abovementioned problems with long cable distances is to transmit the power with high-voltage direct voltage.
• the cable can then be drawn right up to a strong network.
• Another advantage is that DC-transmissions have lower losses than AC-trans- missions. From a technical point of view the cable distance can then be of unlimited length.
• a HVDC-link consists of a rectifier station, a transmission line (cable or aerial line), an inverter station and filters for removing overtones generated during the conversion.
• thyristors are used for rectification and inversion.
• Thyristors can be switched on but not switched off: the commutation takes place at the zero- crossing of the voltage, which is determined by the alternating voltage, and the converters are therefore called line commu- tating.
• IGBT Insulated Gate Bipolar Transistor
• An IGBT can be switched on as well as switcne ⁇ off and furthermore has a high switch fre- quency. This implies that the converters can be produced according to a completely different principle, so called self-com- mutating converters.
• a self-commutating converter is characterized in that the voltage is built up by a rapid pulse pattern, which is generated by the converter.
• VSI Voltage Source Inverter
• CSI Current Source Inverter
• a synchronous generator is not to any disadvantage, but rather to an advantage, since the asynchronous generator requires a more expensive and more complicated rectifier. If it is desired to have a direct driven gen- erator and consequently eliminate the nee ⁇ of a gear unit between the turbine and the generator, the generator must be synchronous since it will be provided with so many poles. In other words, a direct driven generator requires a DC-intermediate link. In the concept it is also possible to actively regulate the moment by changing the trigger angle, if a controlled rectifier is used. In most concepts having a variable rotational speed, an external active rotational speed control is furtnermore provided by so called pitch control, which implies that the blade angle is changed on the turbine. A disadvantage with a variable rota- tional speed according to the related concepts is the price of the required power electronics and furthermore that the maintenance of such power electronics out at sea will be difficult and costly.
• the purpose c *' the present invention is to achieve, with deviation from the aoovementioned direct voltage connections, an alternating voltage connection between a particularly sea based wind park and _ particularly land located transmission or distribution network with the possibility of considerably longer transmission distances and lower losses than what is offered by a conventional alternating voltage connection, and at the same time create the cossibility for operation with a variable rotational speed without any power electronics at all out at sea. This is very valuable. s: ⁇ ce all maintenance taking place at sea is expensive and difficult to perform.
• a further purpose with the invention is to achieve the same good regulation possibilities concerning reactive power as offered by a modern HVDC-system.
• the purpose of the invention is primarily achieved in that a frequency converter is connected to the electrical alternating volt- age connection on the network side of the plant, which frequency converter is arranged to fix the frequency of the connection between the wind power station and the converter to be essentially below the network frequency and to convert this low frequency of the connection into correspondence with the higher frequency of the network.
• the expression "on the network side of the plant” consequently means that the frequency converter is located relatively close to the transmission or distribution network, whereas the principle part of the connection extends between the frequency converter and the wind power station itself, for instance in the form of a submarine cable.
• a further advantage of the inventional idea is that the frequency converter consequently will be located close to the transmission or distribution network, i.e. normally on land, which drastically reduces the costs for maintenance and supervision and also reduces the duration of service interruptions in case of breakdowns.
• several wind power stations with asynchronous generators are interconnected parallelly with the alternating voltage connection.
• the suitable frequency and voltage of the alternating voltage con- nection depends on the size of the wind park and the distance from land, but for a 50 MW wind park a frequency of 10-20 Hz at 130 kV should be suitable.
• the frequency converter comprises a direct voltage intermediate link with an AC/DC-converter and an inverter arrangement.
• a DC/DC-converter is comprised in the direct voltage intermediate link.
• valves in the frequency converter consist of IGBT:s connected in series, other types of valves would be possible to use.
• other types of frequency converters for instance direct converters, also called “cyclo converters", which lack a direct voltage link, can be used with the invention as well as also other frequency converters than static ones, i.e. also rotary frequency converters.
• At least one transformer can be arranged on the generator side of the connection for step-down transformation of the voltage of the alternating voltage connection between the generator and the frequency converter to a suitable generator voltage level.
• each of the occurring generators can be provided with its own transformer, in addition to which as a complement or an alternative thereof, a transformer being common for all generators can be provided. Consequently such transformers make it possible to increase the voltage ir the alternating voltage connection to a higher level than conventional generators are capable of.
• a disadvantage of such transformers is that they imply an extra cost and also entail the deficiency that the total effectivity of the system is reduced. They also imply a risk of fire and a risk for the envi- ronment since they contain transformer oil, wnich can leak out in case of breakdown or vandalism.
• a solid insulation is used for at least one winding in the generator, which insulation preferably is performed according to the subsequent claim 14.
• the winding has more specifically the character of a high-voltage cable.
• a generator manufactured in this way creates the prerequisites of achieving considerably higher voltages than conventional generators. Up to 400 kV can be achieved.
• such an insulation system in the winding implies insensibility to salt, humidity and temperature variations.
• the high output voltage implies that transformers can be completely excluded, which implies avoidance of the already mentioned disa ⁇ vantages of such transformers.
• a generator having such a winding formed by a cable can be produced by threading the cable in slots performed for this purpose in the stator, whereupon the flexibility of the winding cable implies that the threading work can be easily performed.
• the two semiconducting layers of the insulation system have a potential compensating function and consequently reduce the risk of surface glow.
• the inner semiconducting layer is to be in electrically conducting contact with the electrical conductor, or a part thereof, located inwardly of the layer, in order to obtain the same potential as this.
• the inner layer is intimately fastened to the solid insulation located outwordly thereof and this also applies to the fastening of the outer semiconducting layer to the solid insulation.
• the outer semiconducting layer tends to contain the electrical field within the solid insulation.
• the semiconducting layer and the solid insulation have essentially the same thermal coefficient of expansion.
• the outer semiconducting layer in the insulation system is connected to ground potential or otherwise a relatively low potential.
• the generator has a number of features which have already been mentioned above and which distinctly differ from conventional technology. Further features are defined in the dependent claims and are discussed in the following:
• the winding in the magnetic circuit is produced of a cable having one cr several permanently insulated electrical conductors with a semiconducting layer at the conductor and outwardly of the solid insulation.
• Typical cables of this kind are cables having an insulation of cross-linked polyethylene or ethylene-propene, which for the purpose here in question are further developed concerning stands of the electrical conductor and also the character of the insulation system.
• Cables having a circular cross section are preferred, but cables having another cross section can also be used for instance in or ⁇ er to achieve a better packing density.
• Such a cable makes it possible to design a laminated core of the magnetic circuit in a new and optimal way as concerns slots and teeth.
• the winding is produced with a stepwise increasing insulation for the best utilization of the laminated core.
• the winding is produced as a concentric cable winding , which makes it possible to reduce the number of coil end crossings.
• the shape of the slots is adapted to the cross section of the winding cable so that the slots are in the form of a number of cylindrical openings extending axially and/or radially outwardly of each other and having constrictions running between the layers of the stator winding.
• the shape of the slots is adapted to the cable cross section in question and to the stepwise changing thickness of the insulation of tne winding.
• the stepwise insulation makes it possible for the magnetic core to have an essentially constant tooth width independent of the radial extension.
• the cable can have an outer diameter in the order of 10- 40 mm and a conductor area in the order of 1 0-200 mm .2
• the invention comprises a method for controlling the operation of a wind power plant according to the subsequent claims.
• Fig 1 is a schematic axial end view of a sector of the stator in an electric generator in the wind power plant according to the m- vention.
• Fig 2 is an en ⁇ view, partly cut, of a cable used in the stator winding according to Fig 1 ,
• Fig 3 is a schematic view, partly in section, of an embodiment of a wind power ge n erator according to the invention
• Fig 4 is a schematic view showing the embodiment of the wind power plant according to the invention
• Fig 5 is likewise a schematic view illustrating an alternative embodiment of the plant
• Fig 6 is a view similar to Fig 5 of a variant.
• Fig 7 is a view illustrating a possible embodiment of the frequency converter comprised in the plant.
• Fig 1 shows a schematic axial view through a sector of the stator 2.
• the rotor of the generator is denoted as 3.
• the stator 2 is in a conventional way formed of a laminated core.
• Fig 1 shows a sector of the generator corresponding to a pole pitch. From a yoke section of the core, located furthest out in radial direction, a number of teeth 5 extend radially inwards towards the rotor 3 and these teeth are separated by a slot 6, in which the stator winding is arranged.
• PEX cross-linked polyethylene
• the cables 7 are schematically illustrated in Fig 1 , wherein only the electrically conducting central part of each cable section or coil side is shown. It appears that each slot 6 has a varying cross section with alternating broad parts 8 and narrow parts 9.
• the broad parts 8 are essentially circular and surround the cable, waist sections between the broad parts forming the narrow parts 9.
• the waist sections serve to radially fix the position of each cable.
• the cross section of the slot 6 becomes narrower radially inwards. This depends on that the volt- age in the cable sections are lower the closer they are situated to the radially innermost part of the stator 1 . Thinner cables can therefore be used inwards, whereas thicker cables are required further out.
• cables v/ith three different dimensions and arranged in three correspondingly dimensioned sections 1 0, 1 1 . 12 of the slot 6 are used.
• a winding 13 for auxiliary power is arranged furthest out in the slot 6.
• Fig 2 shows a stepwise cut end view of a high-voltage cable for use in the generator.
• the high-voltage cable 7 comprises one or several electrical conductors 14, each of which comprises a number of strands 15, which together give a circular cross section.
• the conductors can for instance be of copper.
• These conductors 14 are arranged in the middle of the high-voltage cable 7 and in the shown embodiment each of the conductors is sur- rounded by a partial insulation 16. It is however possible to omit the partial insulation 16 on one of the conductors 14.
• the conductors 14 are surrounded by a first semi-conducting layer 17. Around this first semiconducting layer 17 there is an insulation layer 18, e.g.
• a wind cower station is shown with a magnetic circuit of the type described with reference to Figs 1 and 2.
• the generator 1 is driven by a wind turbine 20 via a shaft 21 . Even though the generator 1 can oe direct driven by the turbine 20, i.e.
• the rotor of the generator is coupled fixed in rotation to the shaft of the turbine 20 mere can be a gearing 22 between the turbine 20 and the generator 1
• This can for instance oe constituted by a single-step planetary gearing, the purpose of which is to change up the rotational speed of the generator in relation to the rotational speed of the turbine
• the stator 2 of the generator carries the stator windings 23 which are built up of the cable 7 described above
• the cable 7 can be unsheatheo and pass on into a sheathed cable 24 via a cable joint 25
• Fig 4 which in a schematic form broadly illustrates the wind power plant, two wind power stations 29 connected in parallel are illustrated each having a generator
• the generator has a field winding 26 and one (or several) auxiliary power windings 27.
• the generators are Y-connected and the neutral point is grounded via a respective impedance 28.
• connection 30 connects the two wind power stations 29 to a transmission or distribution network 31 .
• This is here of three-phase type
• the normal frequency of such a networ ⁇ is 50 or 60 Hz
• the connection 30 comprises, along a section denoted as 32, a cable 33 intended to be submerged into water
• a cable submerged into water instead of a cable submerged into water, one or several aerial lines/cables could also come into question
• the section 32 can in practice be very large.
• a frequency converter 34 is connected to tne electrical alternating voltage connection 30, which frequency converter is arranged to fix the frequency of the connection between the wind power station 29 and the converter 34 to be substantially below the frequency of the network 31 and to convert this tow frequency of the connection into correspondence with the nigher frequency of the network 31
• the generator 1 is of asynchronous type in the example.
• the frequency converter 34 is suitably located on land in a suitable station nearby the network 31 .
• the wind power stations 29 are located out at sea or a lake on suitable foundations. On one of these foundations, or on a foundation particularly set ups for this purpose, the outgoing cables from the generators 1 are interconnected, e.g . via bus-bars, in a point denoted as 35.
• Fig 4 it is illustrated how a circuit breaker 36 is provided between the frequency converter 34 and the network 31 and sets of disconnectors on each side thereof.
• the generators 1 are direct coupled to the frequency converter 34. This is a consequence of the fact that the generators 1 are supposed to be of the design described above with reference to Figs 1 and 2, i.e. capable of generating a very high voltage.
• a transformer 31 common for the generators 1 , is arranged between the parallel connection point 35 for the generators 1 and the frequency converter 34, which transformer is intended to achieve a high voltage in the part of the connection situated between the transformer and the frequency converter 34 and a comparatively lower voltage between said transformer 38 and the generators X
• This common transformer 38 is located on the wind power side of the connection 30, i.e. close to the wind power station 29. so that the main part of the connection 30 will be present between the transformer 38 and the frequency converter 34.
• the transformer 38 can be placed on one of the foundations for the wind power stations 29 or possibly on its own foundation on a strategic place.
• Fig 6 illustrates an alternative corresponding to the one in Fig 5 with the exception that a particular transformer 39 is here arranged for each of the generators 1 . Consequently, the wind power stations are parallelly interconnected in the point 35 only after these transformers. In such an embodiment, it would be possible to omit the transformer 38. which has been more closely described with reference to Fig 5. Further, it is also possible to keep the transformer 38 so that the voltage from a single wind power station will be stepped up in two steps, i.e. at first via the transformer 39 and then by means of the common transformer 38.
• a possible embodiment of the frequency converter 34 is illustrated. It here includes a direct voltage intermediate link having a AC/DC-converter 40 and an inverter 41 .
• a DC/DC-converter 42 is advantageously included in the direct voltage intermediate link .
• the inverter 41 is a voltage stiff self-commutated inverter. Over the DC-link of the inverter a capacitor is parallel connected. Network inductances 44 are connected in series in each phase on the alternating voltage side of the inverter 41 .
• the inverter 41 suitably comprises an IGBT 45.
• the AC/DC-converter can be built up like the inverter 41 and has on its AC-side network inductances 46 in series in each phase.
• the converter 40 can comprise an IGBT 47.
• the plant has means (not shown) for measuring the active power from the v/ind power plant and means for measuring the present wind SDeed. These measuring means are connected to a control unit comprised in the frequency converter 34, which control unit controls the frequency regulation depending on the prevailing measuring values.
• the control unit can be arranged to control the frequency of the connection 30 in correspondence with an ideal characteristic over the rotational speed of the wind turbine as a function of wind speed.
• Such a frequency control can be denoted as "slow " . It is based on that the rotational speed of the wind power stations preferably should rise linearly with the wind speed up to the maximum ro- tational speed. With knowledge about the wind speed, a comparatively slow frequency control can consequently take place in the connection 30 so that the most favourable conditions ensue.
• the control unit is furthermore suitably arranged to control the frequency of the connection 30 by comparison of measured transmitted active power with an ideal characteristic over the rotational speed as a function of power.
• a frequency control can here popularly be denoted as "fast”. It is conducted with the aim of rapid power variations and this can e.g. be achieved with Pl-regulation and regeneration of the transmitted power through the DC-link, as described with reference to Fig 7.
• control unit is made to control the frequency converter 34 to maintain a constant ratio voltage/frequency of the connection over the major part of the frequency range.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Control Of Eletrric Generators (AREA)
• Supply And Distribution Of Alternating Current (AREA)
• Wind Motors (AREA)
• Windings For Motors And Generators (AREA)
• Insulation, Fastening Of Motor, Generator Windings (AREA)

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• 1999
  • 1999-05-28 EE EEP200100629A patent/EE200100629A/xx unknown
  • 1999-05-28 CN CN99816679A patent/CN1352731A/zh active Pending
  • 1999-05-28 PL PL99351025A patent/PL351025A1/xx unknown
  • 1999-05-28 BR BR9917307-7A patent/BR9917307A/pt not_active IP Right Cessation
  • 1999-05-28 JP JP2001500117A patent/JP2003501000A/ja active Pending
  • 1999-05-28 EP EP99933321A patent/EP1190176A1/en not_active Withdrawn
  • 1999-05-28 CA CA002375067A patent/CA2375067A1/en not_active Abandoned
  • 1999-05-28 AU AU49390/99A patent/AU759174B2/en not_active Ceased
  • 1999-05-28 WO PCT/SE1999/000944 patent/WO2000073652A1/en not_active Application Discontinuation
  • 1999-05-28 TR TR2001/03401T patent/TR200103401T2/xx unknown
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• 2000
  • 2000-05-26 AR ARP000102580A patent/AR024116A1/es unknown
  • 2000-06-05 TW TW089110973A patent/TW522202B/zh not_active IP Right Cessation
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