WO2010018264A1 - Electric power transmission system with a dc link - Google Patents
Electric power transmission system with a dc link Download PDFInfo
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- WO2010018264A1 WO2010018264A1 PCT/ES2009/000410 ES2009000410W WO2010018264A1 WO 2010018264 A1 WO2010018264 A1 WO 2010018264A1 ES 2009000410 W ES2009000410 W ES 2009000410W WO 2010018264 A1 WO2010018264 A1 WO 2010018264A1
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- Prior art keywords
- voltage
- bus
- transformers
- rectifier
- current
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- 230000005540 biological transmission Effects 0.000 title claims abstract description 47
- 238000000034 method Methods 0.000 claims abstract description 31
- 238000001914 filtration Methods 0.000 claims description 5
- 238000006073 displacement reaction Methods 0.000 claims description 3
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- 230000008030 elimination Effects 0.000 description 6
- 238000003379 elimination reaction Methods 0.000 description 6
- 230000008878 coupling Effects 0.000 description 5
- 238000010168 coupling process Methods 0.000 description 5
- 238000005859 coupling reaction Methods 0.000 description 5
- 238000010304 firing Methods 0.000 description 4
- 238000009434 installation Methods 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 230000002457 bidirectional effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
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- 230000008859 change Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
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- 229910052742 iron Inorganic materials 0.000 description 1
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Classifications
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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
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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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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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
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Definitions
- the described invention consists of a system of transmission of electric power in direct current that joins two or more buses of alternating current and its associated control method. It is of special relevance in the sector of transport and distribution of electrical energy, especially for cases where the production plants are very far from the distribution and consumption areas, as is the case of wind farms located on the high seas.
- the typical configuration consists of the connection of the different generators, directly or through electronic power systems, to a common collector or alternating bar.
- Said alternating bar is connected to a converter that rectifies the alternating current and delivers it to a direct current transmission line.
- the direct current line is connected in turn to the alternating transmission network through an inverter. It is necessary to control the voltage variations in the alternating line to which the generators are connected and for this a synchronous or static compensator (or STATCOM) and / or different reactive power compensation filters and banks are used.
- STATCOM synchronous or static compensator
- the control of the transmitted power is carried out by means of trigger pulses applied to each of the converters.
- the rectifier converter controls the current
- the inverter converter controls the voltage of the continuous link, getting a control of the power transmitted by means of the firing impulses applied to each of the converters. It is also possible to control the voltage by the rectifier and the current by the inverter.
- the coupling of alternating current networks through high-voltage direct current links is justified, in most cases, for economic reasons. In other cases, the need to couple two or more asynchronous AC buses justifies said connection.
- the invention described herein proposes a new control method and a new configuration of the energy transmission system by which the voltage, frequency and harmonic content in the collector is modified to control the voltage and / or current (and , therefore, the power) of the continuous comment link, resulting in a simpler and cheaper method when it comes to its implementation than those known to date.
- references to electric power transmission systems by high-voltage direct current and its associated control method are known, such as those found in WO 2006/35018 A2, WO 2006/034250 A1, WO 02 / 063758 A1, WO 00/62409 A1, WO 2006/094952 A1, WO 2006/037412 A1 or WO 2007/027141 A1.
- WO 2007/033619 A1 and WO 2007/033620 A1 only the control method is described.
- GB 2423650 A describes a connection system of a single generator of variable voltage and frequency to power supply networks, preferably of fixed voltage and frequency, using a rectifier-inverter; This invention would constitute an alternative for the connection, through electronic power systems, of each of the generators to the collector mentioned above.
- the invention described herein refers to an electric power transmission system with direct current link consisting of several electric generators connected to a collector, directly, or through electronic power systems, and using current transformer lines and transformers. alternate, if it were necessary, with some filters and reactive power compensators.
- the alternating current collector is connected by one or several transformers to an uncontrolled converter or rectifier, so that the angle of displacement between voltage and current is minimal, as well as its reactive power demand, without the need of the transformer tap changer of the rectifier and with a significant reduction or even elimination of harmonic filters and reactive power compensation systems (eg STATCOM or Synchronous Compensator).
- the uncontrolled rectifier feeds a direct current line that connects to the alternating transmission network through an inverter, by means of one or several transformers.
- the invention also relates to a method of control and transmission of electrical energy in an electrical energy transport network, whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located are modified to control the voltage and / or the current of the direct current link of an electrical energy transmission system in an electrical energy transport network.
- Said network consists of electric generators connected to a collector or bus of alternating current, directly or through a connection system consisting of electronic power systems and / or transformers, with their corresponding power lines, with filters and power compensators reactive
- the collector or bus of alternating current is connected, by one or several transformers, to an uncontrolled converter or rectifier, so that the angle of displacement between voltage and current is minimal, as well as its reactive power demand, without the need of the changer of shots.
- the uncontrolled rectifier feeds a direct current line that is connected to the alternating current receiver network through an inverter, adapting the voltage by one or more transformers.
- a method of control and transmission of electrical energy in an electrical energy transport network whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located are modified to control the voltage and / or the current of the direct current link of an electrical energy transmission system in an electrical energy transport network.
- Said network consists of electric generators connected to a collector or bus of alternating current, directly or through a connection system consisting of electronic power systems and / or transformers, with their corresponding electric lines, with filters and reactive power compensators, and where the collector or AC bus is connected, by one or several transformers, to a controlled converter or rectifier, so that the tap changer of the transformers is eliminated and the systems are reduced or eliminated of filtering and reactive compensation.
- the controlled rectifier feeds a direct current line that is connected to the alternating current receiver network through an inverter, adapting the voltage by one or more transformers.
- FIG. 1 represents a standard high voltage direct current (HVDC) transmission system according to the state of the art known until now.
- HVDC high voltage direct current
- FIG. 2 illustrates an energy transmission system with direct current link and uncontrolled rectifier according to what is described in the present invention.
- Figure 3 shows a system that uses several uncontrolled converters in the same location or in geographically separated locations, which evacuate their power in the same high-voltage direct current line.
- Generators System connecting the generators to the alternating network.
- Bus or alternating collector of the generating network of alternating generator 4.
- the invention described consists of a system of transmission of electric power in direct current that links two or more AC buses and their associated control method.
- the coupling of alternating current networks through direct current links is justified in most cases, as previously noted, for economic reasons. In other cases, the need to couple two or more asynchronous AC buses justifies said connection.
- the installations of transmission of electrical energy by means of direct current lines are, in general, bidirectional, that is, the electrical energy
- a typical system of these characteristics is the one that appears in figure 1.
- a number of generators (1) connected directly or through electronic power systems (2) have been represented, together with the corresponding transformers if necessary, to a common alternating bar or manifold (4) by means of the corresponding alternating current lines (3).
- Said collector (4) is connected to a controlled converter or rectifier (9) directly or by means of one or more transformers (8).
- the controlled rectifier (9) rectifies the alternating current and delivers it to a direct current transmission line (10).
- This direct current line (10) is connected to the receiving alternating network (13) through an inverter (11), directly or through the use of one or more transformers (12).
- the corresponding filters (6) are included on both sides of the transmission system, which attenuate the level of harmonics produced by the controlled rectifier (9), as well as compensators (7), which provide the reactive power necessary for the operation of controlled rectifier (9).
- the filters (6) and the compensators (7) act as elements of the filter banks, which are switched on or off in a staggered manner according to the level of reactive power necessary for the operation of the controlled rectifier (9).
- said filters (6) and the compensators (7) are complemented by synchronous or static compensators (STATCOM) (5), so that the stepwise variation of the reactive power produced between the connection of a bank and the next one is compensated by reactive power producing elements of lower nominal power, but with continuous variation thereof.
- STATCOM synchronous or static compensators
- the control of the transmitted power is carried out by means of the trip impulses applied to each of the converters.
- the rectifier converter controls the current flowing through the DC link and the inverter converter controls the DC link voltage.
- the present invention consists of a control method whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located, is modified in order to control the voltage and / or the current of the direct current link and to reduce the Need for filters (6) and reactive compensation (5 and 7).
- Figure 2 shows the proposed continuous power transmission system. Similar to the configuration of Figure 1, in Figure 2 a number of generators (1) connected directly or through electronic power systems (2), together with the corresponding transformers if necessary, have been represented to a bar of alternating common or collector (4) by means of the corresponding lines of alternating current (3). Likewise, there may be reactive power compensation banks (7), filters (6) and compensators (5).
- the alternating current bus (4) is connected, by means of a transformer (8), to an uncontrolled converter or rectifier (9a).
- the transformer sockets (8) are superfluous.
- the tap changer of the transformer (8) is used to maintain the firing angle of the controlled rectifier valves (9) in a certain range in steady state and thus reduce the reactive power demand of said rectifier (9) .
- the firing angle is always zero degrees and the reactive power demand is minimal, without the need for the tap-changer.
- the proposed system entails reducing costs and increasing the robustness of the system as a whole.
- the instantaneous voltage of the alternating current bus (4) and, therefore, the effective voltage, is controlled by acting on the generators (1), either directly, modifying its magnetizing current, or acting on the electronic power systems (2 ) that connect the generators to the alternating bus (4).
- the voltage variation in the alternating bus (4) is ideally reflected proportionally in a variation in the rectified voltage in the continuous bus (10), through the uncontrolled rectifier (9a).
- the voltage in the continuous bus can be controlled, by adjusting the corresponding voltage of the alternating bus.
- the inverter (11) should be controlled to ensure the current circulation to achieve the transmission of the desired power.
- the inverter (11) should be controlled to ensure the level of voltage in the continuous bus (10) to achieve the transmission of the desired power.
- the frequency and voltage control of the alternating bus (4) could be carried out jointly.
- the proposed control method also contemplates the use of voltage waveforms and harmonic currents in the collector, which is equivalent to the use of non-sinusoidal waveforms. In this way, it is possible to collaborate in the filtering of harmonics produced by the rectifier, and even to eliminate the filter banks used for this purpose.
- the proposed control method could complement, if deemed necessary, the method proposed in WO 2006/035018 A2, and thus achieve the advantages of said control method, among others, a reduction in thermal and stress stress of the different elements of the system and a decrease in the risk of switching faults in the inverter.
- the proposed method is especially indicated, among other cases, for use in large wind farms located a great distance from the transmission network (for example, offshore wind farms), in which the voltage, power and frequency of the different wind turbines is controlled by electronic converters.
- the exposed advantages are especially relevant, for example, in large offshore wind farms, in which an increase in the robustness of the rectifier, to the For a decrease in their weight, they represent important economic benefits in the implementation and operation of the wind farm.
- the reactive power provided by the filters (6) and compensators (7) can be continuously adjusted, and the losses produced in lines (3), (10) and transformers (8) can be minimized. ), (12), by means of the variation of the voltage and the frequency of the collector (4), either independently or in a coordinated manner. In this way, the power of the required synchronous compensator (5) could be reduced or eliminated completely. Again important economic advantages are achieved, as well as in the robustness of the transmission system as a whole, having managed to eliminate a point of critical failure.
- the operation at relatively high frequencies allows the reduction of losses in lines and transformers. It is foreseeable that the losses in the rectifier will increase as the frequency of the collector increases, so that it is also possible to adjust the frequency within a range so that the overall losses are minimized.
- This type of generators is characterized by the direct connection of the stator to the network, while its control is carried out by means of AC / DC / AC converters that connect the generator rotor with the alternating current network. They have the great advantage that the nominal power of the electronic converters used is a fraction of the nominal power of the set.
- the stator voltage of the generators which are directly connected to the collector (or through one or more transformers), can be easily reduced by flow weakening techniques. Said voltage reduction allows controlling the current flowing through the direct current link.
- the voltage reduction range produced by the wind turbines is not generally excessively large, but this small variation margin is sufficient to control the current through the direct current link. In this case, the DC voltage would be controlled by the inverter converter.
- the iron losses of the generators and transformers would be reduced when operating at a voltage lower than the nominal voltage.
- the operation at reduced voltage in the stator also allows the reduction in the rotor voltage, with which the range of operating speeds of the turbine is extended, being able to extract more energy at low wind speeds.
- the system described would not require a transformer with tap changer, although in certain cases it may require sufficient filtering to mitigate the harmonics produced by the rectifier.
- Wind turbines based on synchronous generators are connected to the network through AC / DC / AC (or AC / AC) converters of nominal power equal to that of the generator.
- This type of converters implies a greater expense than in the double-feed asynchronous generators, however, they provide, among other advantages, a greater flexibility in the control, a greater range of operating speeds of the turbine and a better behavior before transients in The electricity network.
- This type of wind turbines can use the described control method to regulate the current flowing through the continuous link.
- the rapid response of this type of wind turbines allows the wind turbines themselves to be able to control the currents that circulate in the alternating and high-voltage continuous installations during faults and transients. Since the converters of the wind turbines can carry out the constant voltage regulation, it is possible to eliminate the changes of sockets of the different transformers.
- converters of this type of wind turbines can provide a certain level of reactive power and even harmonic currents, so that the nominal values of the harmonic and reactive filters can be lowered or even eliminated.
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention relates to an electric power transmission method and system with a DC link, including electric generators (1) connected to an AC collector or bus (4) either directly or via a wiring system (2) consisting of electronic power systems and/or transformers and the corresponding electric lines (3) thereof, said system also including reactive power compensators (7) and filters (6). The AC collector (4) is connected using transformers (8) to a non-controlled rectifier or converter (9a), such that the offset angle between voltage and current is minimum, as is the reactive power requirement thereof.
Description
Sistema de transmisión de energía eléctrica con enlace de corriente continua Electric power transmission system with direct current link
La invención descrita consiste en un sistema de transmisión de energía eléctrica en corriente continua que une dos o más buses de corriente alterna y su método de control asociado. Es de especial relevancia en el sector del transporte y distribución de energía eléctrica, especialmente para los casos en que las centrales de producción se encuentran muy alejadas de las áreas de distribución y consumo, como es el caso de los parque eólicos situados en alta mar.The described invention consists of a system of transmission of electric power in direct current that joins two or more buses of alternating current and its associated control method. It is of special relevance in the sector of transport and distribution of electrical energy, especially for cases where the production plants are very far from the distribution and consumption areas, as is the case of wind farms located on the high seas.
Problema a resolverProblem to solve
El acoplamiento a redes de transmisión de energía eléctrica de grandes instalaciones generadoras situadas a largas distancias es particularmente complejo. Este acoplamiento es especialmente importante en instalaciones eólicas de muy alta capacidad. Actualmente se están proyectando en el Mar del Norte instalaciones offshore de más de 1 GW de potencia instalada; algunos de estos parques están situados a más de 40 km de Ia costa, con Io que Ia transmisión de energía en corriente continua de alto voltaje (HVDC) es Ia solución tecnológica más factible. A estos niveles de potencia, Ia tecnología más adecuada consiste en el uso de sistemas rectificador- inversor a base de tiristores autoconmutados. A potencias menores es posible utilizar los sistemas HVDC-Light, con conversores fuente de tensión (VSC); sin embargo, Ia utilización de sistemas con tiristores conmutados por línea (LCT) resulta Ia solución más factible cuando Ia potencia instalada supera los 500-600 MW.The coupling to electricity transmission networks of large generating facilities located over long distances is particularly complex. This coupling is especially important in wind farms of very high capacity. Offshore facilities with more than 1 GW of installed power are currently being projected in the North Sea; Some of these parks are located more than 40 km from the coast, so that the transmission of high-voltage direct current (HVDC) energy is the most feasible technological solution. At these power levels, the most appropriate technology consists in the use of rectifier-inverter systems based on self-switched thyristors. At lower powers it is possible to use HVDC-Light systems, with voltage source converters (VSC); However, the use of systems with line switched thyristors (LCT) is the most feasible solution when the installed power exceeds 500-600 MW.
La configuración típica consiste en Ia conexión de los distintos generadores, directamente o a través de sistemas electrónicos de potencia, a un colector o barra de alterna común. Dicha barra de alterna se conecta a un conversor que rectifica Ia corriente alterna y Ia entrega a una línea de transmisión de corriente continua. La línea de corriente continua se conecta a su vez a Ia red de transmisión en alterna a través de un inversor. Es necesario controlar las variaciones de tensión en Ia línea alterna a Ia que se conectan los generadores y para ello se utiliza un compensador síncrono o estático (o STATCOM) y/o diferentes filtros y bancos de compensación de potencia reactiva. Los sistemas propuestos conocidos hasta ahora consideran que distintos parámetros característicos (valor eficaz, frecuencia) de Ia tensión en el punto de conexión de los generadores (colector) deben ser mantenidas constantes. Por ello, el control de Ia potencia transmitida se realiza por medio de impulsos de disparo aplicados a cada uno de los conversores. Generalmente, el conversor rectificador controla Ia corriente y el conversor inversor controla Ia tensión del enlace de continua,
consiguiendo un control de Ia potencia transmitida por medio de los impulsos de disparo aplicados a cada uno de los conversores. También es posible el control de Ia tensión por parte del rectificador y de Ia corriente por parte del inversor.The typical configuration consists of the connection of the different generators, directly or through electronic power systems, to a common collector or alternating bar. Said alternating bar is connected to a converter that rectifies the alternating current and delivers it to a direct current transmission line. The direct current line is connected in turn to the alternating transmission network through an inverter. It is necessary to control the voltage variations in the alternating line to which the generators are connected and for this a synchronous or static compensator (or STATCOM) and / or different reactive power compensation filters and banks are used. The proposed systems known so far consider that different characteristic parameters (effective value, frequency) of the voltage at the connection point of the generators (collector) must be kept constant. Therefore, the control of the transmitted power is carried out by means of trigger pulses applied to each of the converters. Generally, the rectifier converter controls the current and the inverter converter controls the voltage of the continuous link, getting a control of the power transmitted by means of the firing impulses applied to each of the converters. It is also possible to control the voltage by the rectifier and the current by the inverter.
Por otro lado, no se tiene conocimiento de ningún sistema que explote Ia capacidad de inyección de corrientes armónicas y reactivas de los generadores para Ia minimización de los requerimientos de filtrado del rectificador.On the other hand, there is no knowledge of any system that exploits the capacity of injection of harmonic and reactive currents of the generators for the minimization of the filtering requirements of the rectifier.
El acoplamiento de redes de corriente alterna a través de enlaces de corriente continua de alta tensión se justifica, en Ia mayaría de los casos, por razones económicas. En otros casos, Ia necesidad de acoplar dos o más buses de corriente alterna asincronos justifica dicha conexión. La invención que se describe en el presente documento propone un nuevo método de control y una nueva configuración del sistema de transmisión de energía por el cual Ia tensión, frecuencia y contenido armónico en el colector es modificado para controlar Ia tensión y/o corriente (y, por Io tanto, Ia potencia) del enlace de comente continua, resultando un método más sencillo y económico a Ia hora de proceder a su implementación que los conocidos hasta Ia fecha.The coupling of alternating current networks through high-voltage direct current links is justified, in most cases, for economic reasons. In other cases, the need to couple two or more asynchronous AC buses justifies said connection. The invention described herein proposes a new control method and a new configuration of the energy transmission system by which the voltage, frequency and harmonic content in the collector is modified to control the voltage and / or current (and , therefore, the power) of the continuous comment link, resulting in a simpler and cheaper method when it comes to its implementation than those known to date.
Estado de Ia técnicaState of the art
En el estado de Ia técnica se conocen referencias a sistemas de transmisión de energía eléctrica mediante corriente continua de alta tensión y su método de control asociado, como las que aparecen en los documentos WO 2006/35018 A2, WO 2006/034250 A1 , WO 02/063758 A1 , WO 00/62409 A1 , WO 2006/094952 A1 , WO 2006/037412 A1 o WO 2007/027141 A1. En otros documentos, como WO 2007/033619 A1 y WO 2007/033620 A1 , se describe únicamente el método de control. Por su parte, el documento GB 2423650 A describe un sistema de conexionado de un único generador de tensión y frecuencia variable a redes de suministro eléctrico, preferentemente de tensión y frecuencia fija, empleando un rectificador-inversor; esta invención constituiría una alternativa para el conexionado, a través de sistemas electrónicos de potencia, de cada uno de los generadores al colector mencionado con anterioridad.In the state of the art, references to electric power transmission systems by high-voltage direct current and its associated control method are known, such as those found in WO 2006/35018 A2, WO 2006/034250 A1, WO 02 / 063758 A1, WO 00/62409 A1, WO 2006/094952 A1, WO 2006/037412 A1 or WO 2007/027141 A1. In other documents, such as WO 2007/033619 A1 and WO 2007/033620 A1, only the control method is described. For its part, GB 2423650 A describes a connection system of a single generator of variable voltage and frequency to power supply networks, preferably of fixed voltage and frequency, using a rectifier-inverter; This invention would constitute an alternative for the connection, through electronic power systems, of each of the generators to the collector mentioned above.
Descripción de Ia invenciónDescription of the invention
La invención que aquí se describe se refiere a un sistema de transmisión de energía eléctrica con enlace de corriente continua que consta de varios generadores eléctricos conectados a un colector, directamente, o a través de sistemas electrónicos de potencia, y que usa líneas y transformadores de corriente alterna, si fuera
necesario, contando con unos filtros y compensadores de potencia reactiva. El colector de corriente alterna se conecta mediante uno o varios transformadores a un conversor o rectificador no controlado, de manera que el ángulo de desplazamiento entre tensión y corriente sea mínimo, así como su demanda de potencia reactiva, sin necesidad del cambiador de tomas del transformador del rectificador y con una reducción importante o incluso eliminación de los filtros de armónicos y de los sistemas de compensación de potencia reactiva (p.ej. STATCOM o Compensador Sincrónico).The invention described herein refers to an electric power transmission system with direct current link consisting of several electric generators connected to a collector, directly, or through electronic power systems, and using current transformer lines and transformers. alternate, if it were necessary, with some filters and reactive power compensators. The alternating current collector is connected by one or several transformers to an uncontrolled converter or rectifier, so that the angle of displacement between voltage and current is minimal, as well as its reactive power demand, without the need of the transformer tap changer of the rectifier and with a significant reduction or even elimination of harmonic filters and reactive power compensation systems (eg STATCOM or Synchronous Compensator).
El rectificador no controlado alimenta, por otro lado, a una línea de corriente continua que se conecta a Ia red de transmisión de alterna a través de un inversor, mediante uno o varios transformadores.The uncontrolled rectifier, on the other hand, feeds a direct current line that connects to the alternating transmission network through an inverter, by means of one or several transformers.
La invención también se refiere a un método de control y transmisión de energía eléctrica en una red de transporte de energía eléctrica, por el cual Ia tensión, Ia frecuencia y el contenido armónico del bus de alterna donde se encuentran los generadores son modificados para controlar Ia tensión y/o Ia corriente del enlace de corriente continua de un sistema de transmisión de energía eléctrica en una red de transporte de energía eléctrica. Dicha red consta de unos generadores eléctricos conectados a un colector o bus de corriente alterna, directamente o a través de un sistema de conexionado consistente en sistemas electrónicos de potencia y/o transformadores, con sus correspondientes líneas eléctricas, contando con unos filtros y compensadores de potencia reactiva. El colector o bus de corriente alterna se conecta, mediante uno o varios transformadores, a un conversor o rectificador no controlado, de manera que el ángulo de desplazamiento entre tensión y corriente sea mínimo, así como su demanda de potencia reactiva, sin necesidad del cambiador de tomas. En dicho método, el rectificador no controlado alimenta una línea de corriente continua que se conecta a Ia red de receptora de corriente alterna a través de un inversor, adecuando Ia tensión mediante uno o varios transformadores.The invention also relates to a method of control and transmission of electrical energy in an electrical energy transport network, whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located are modified to control the voltage and / or the current of the direct current link of an electrical energy transmission system in an electrical energy transport network. Said network consists of electric generators connected to a collector or bus of alternating current, directly or through a connection system consisting of electronic power systems and / or transformers, with their corresponding power lines, with filters and power compensators reactive The collector or bus of alternating current is connected, by one or several transformers, to an uncontrolled converter or rectifier, so that the angle of displacement between voltage and current is minimal, as well as its reactive power demand, without the need of the changer of shots. In said method, the uncontrolled rectifier feeds a direct current line that is connected to the alternating current receiver network through an inverter, adapting the voltage by one or more transformers.
En otra configuración, se propone un método de control y transmisión de energía eléctrica en una red de transporte de energía eléctrica, por el cual Ia tensión, Ia frecuencia y el contenido armónico del bus de alterna donde se encuentran los generadores son modificados para controlar Ia tensión y/o Ia corriente del enlace de corriente continua de un sistema de transmisión de energía eléctrica en una red de transporte de energía eléctrica. Dicha red consta de unos generadores eléctricos conectados a un colector o bus de corriente alterna, directamente o a través de un sistema de conexionado consistente en sistemas electrónicos de potencia y/o transformadores, con sus correspondientes líneas eléctricas, contando con unos filtros
y compensadores de potencia reactiva, y donde el colector o bus de corriente alterna se conecta, mediante uno o varios transformadores, a un conversor o rectificador controlado, de manera que se elimine el cambiador de tomas de los transformadores y se reduzcan o eliminen los sistemas de filtrado y compensación de reactiva. En dicho método alternativo, el rectificador controlado alimenta una línea de corriente continua que se conecta a Ia red de receptora de corriente alterna a través de un inversor, adecuando Ia tensión mediante uno o varios transformadores.In another configuration, a method of control and transmission of electrical energy in an electrical energy transport network is proposed, whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located are modified to control the voltage and / or the current of the direct current link of an electrical energy transmission system in an electrical energy transport network. Said network consists of electric generators connected to a collector or bus of alternating current, directly or through a connection system consisting of electronic power systems and / or transformers, with their corresponding electric lines, with filters and reactive power compensators, and where the collector or AC bus is connected, by one or several transformers, to a controlled converter or rectifier, so that the tap changer of the transformers is eliminated and the systems are reduced or eliminated of filtering and reactive compensation. In said alternative method, the controlled rectifier feeds a direct current line that is connected to the alternating current receiver network through an inverter, adapting the voltage by one or more transformers.
Descripción de las figuras La figura 1 representa un sistema estándar de transmisión en corriente continua de alta tensión (HVDC) según el estado de Ia técnica conocido hasta ahora.Description of the figures Figure 1 represents a standard high voltage direct current (HVDC) transmission system according to the state of the art known until now.
La figura 2 ilustra un sistema de transmisión de energía con enlace de corriente continua y rectificador no controlado según Io descrito en Ia presente invención.Figure 2 illustrates an energy transmission system with direct current link and uncontrolled rectifier according to what is described in the present invention.
La figura 3 muestra un sistema que utiliza varios conversores no controlados en Ia misma localización o en localizaciones separadas geográficamente, que evacúan su potencia en Ia misma línea de corriente continua de alta tensión.Figure 3 shows a system that uses several uncontrolled converters in the same location or in geographically separated locations, which evacuate their power in the same high-voltage direct current line.
En dichas figuras, las referencias numéricas adjuntas se corresponden con los siguientes elementos:In these figures, the enclosed numerical references correspond to the following elements:
I . Generadores. 2. Sistema de conexión de los generadores a Ia red de alterna.I. Generators 2. System connecting the generators to the alternating network.
3. Líneas eléctricas de alterna que conectan los generadores con el bus de alterna o colector (4).3. AC power lines that connect the generators to the AC bus or collector (4).
4. Bus o colector de alterna de Ia red eléctrica de alterna generadora.4. Bus or alternating collector of the generating network of alternating generator.
5. Compensador dinámico de reactiva (compensador síncrono o STATCOM).5. Dynamic reactive compensator (synchronous compensator or STATCOM).
6. Bancos de filtros.6. Filter banks.
7. Compensadores (bancos de condensadores).7. Compensators (capacitor banks).
8. Transformador.8. Transformer.
9. Rectificador. 9a. Rectificador no controlado.9. Rectifier. 9a. Uncontrolled rectifier.
10. Línea de corriente continua de alta tensión.10. High voltage direct current line.
I I . Inversor.I I. Investor.
12. Transformador.12. Transformer.
13. Bus de alterna de Ia red eléctrica de alterna receptora. 14. Cargas locales.
Descripción de una forma preferente de realización de Ia invención13. AC bus of the receiving AC power grid. 14. Local charges. Description of a preferred embodiment of the invention
Como ya se ha señalado, Ia invención que se describe consiste en un sistema de transmisión de energía eléctrica en corriente continua que une dos o más buses de corriente alterna y su método de control asociado. El acoplamiento de redes de corriente alterna a través de enlaces de corriente continua se justifica en Ia mayoría de los casos, como ya se ha apuntado previamente, por razones económicas. En otros casos Ia necesidad de acoplar dos o más buses de corriente alterna asincronos justifica dicha conexión.As already mentioned, the invention described consists of a system of transmission of electric power in direct current that links two or more AC buses and their associated control method. The coupling of alternating current networks through direct current links is justified in most cases, as previously noted, for economic reasons. In other cases, the need to couple two or more asynchronous AC buses justifies said connection.
Las instalaciones de transmisión de energía eléctrica mediante líneas de corriente continua son, generalmente, bidireccionales, es decir, Ia energía eléctricaThe installations of transmission of electrical energy by means of direct current lines are, in general, bidirectional, that is, the electrical energy
(producto de Ia tensión y Ia corriente continuas) se puede transmitir en ambos sentidos. La inversión del sentido de transmisión de Ia energía se consigue, en Ia mayoría de los casos, invirtiendo el sentido de circulación de Ia comente continua, ya que Ia inversión de Ia polaridad de Ia tensión presenta inconvenientes técnicos importantes.(product of the continuous voltage and current) can be transmitted in both directions. The inversion of the direction of transmission of the energy is achieved, in the majority of cases, by reversing the direction of circulation of the continuous comment, since the inversion of the polarity of the voltage presents important technical disadvantages.
En aquellos casos en los que los sistemas de transmisión de corriente continua únicamente requieran una transmisión de energía unidireccional, es posible sustituir uno o varios de los conversores por rectificadores no controlados, de modo que Ia tensión y/o Ia corriente del enlace de corriente continua pueda ser controlado mediante variaciones de tensión, frecuencia, potencia reactiva, y/o contenido armónico de los correspondientes buses de corriente alterna.In those cases where DC systems require only one-way power transmission, it is possible to replace one or more of the converters with uncontrolled rectifiers, so that the voltage and / or current of the DC link It can be controlled by variations in voltage, frequency, reactive power, and / or harmonic content of the corresponding AC buses.
A modo de ejemplo se puede citar el acoplamiento a redes de transmisión de energía eléctrica de grandes instalaciones generadoras, en las cuales Ia transmisión de energía siempre va a ser unidireccional. La transmisión de Ia energía generada mediante enlaces de corriente continua resulta económica cuando Ia instalación generadora es de gran potencia y se encuentra a gran distancia de Ia red de transmisión eléctrica.By way of example, it is possible to mention the coupling to electric power transmission networks of large generating facilities, in which the energy transmission will always be unidirectional. The transmission of the energy generated by direct current links is economical when the generating installation is of great power and is located a great distance from the electrical transmission network.
Este es el caso de instalaciones eólicas de muy alta capacidad situadas a distancias relativamente grandes de Ia costa. Este tipo de instalaciones presentan Ia característica de una transmisión energética unidireccional y variable, en Ia que Ia utilización de sistemas de transmisión de energía en corriente continua representa Ia alternativa más aconsejable desde los puntos de vista técnico y económico.This is the case of wind farms of very high capacity located at relatively large distances from the coast. These types of installations have the characteristic of a unidirectional and variable energy transmission, in which the use of direct current energy transmission systems represents the most advisable alternative from a technical and economic point of view.
Un sistema típico de estas características, conocido en el estado de Ia técnica, es el que aparece en Ia figura 1. En ella se han representado un número de generadores (1) conectados directamente o a través de sistemas (2) electrónicos de potencia, junto con los correspondientes transformadores si fuera necesario, a una
barra de alterna común o colector (4) mediante las correspondientes líneas de corriente alterna (3). Dicho colector (4) se conecta a un conversor o rectificador controlado (9) directamente o mediante uno o varios transformadores (8). El rectificador controlado (9) rectifica Ia corriente alterna y Ia entrega a una línea de transmisión de corriente continua (10). Esta línea de corriente continua (10) es conectada a Ia red de alterna receptora (13) a través de un inversor (11), directamente o mediante el uso de uno o varios transformadores (12).A typical system of these characteristics, known in the state of the art, is the one that appears in figure 1. In it a number of generators (1) connected directly or through electronic power systems (2) have been represented, together with the corresponding transformers if necessary, to a common alternating bar or manifold (4) by means of the corresponding alternating current lines (3). Said collector (4) is connected to a controlled converter or rectifier (9) directly or by means of one or more transformers (8). The controlled rectifier (9) rectifies the alternating current and delivers it to a direct current transmission line (10). This direct current line (10) is connected to the receiving alternating network (13) through an inverter (11), directly or through the use of one or more transformers (12).
En ambos lados de alterna del sistema de transmisión se incluyen los correspondientes filtros (6), que atenúan el nivel de armónicos producidos por el rectificador controlado (9), así como compensadores (7), que proporcionan Ia potencia reactiva necesaria para el funcionamiento de rectificador controlado (9). De esta manera, los filtros (6) y los compensadores (7) actúan como elementos de los bancos de filtrado, que se conectan o desconectan de forma escalonada según el nivel de potencia reactiva necesaria para el funcionamiento del rectificador controlado (9). En muchos casos, dichos filtros (6) y los compensadores (7) son complementados por compensadores sincrónicos o estáticos (STATCOM) (5), de modo que Ia variación escalonada de Ia potencia reactiva producida entre Ia conexión de un banco y el siguiente sea compensada por elementos productores de potencia reactiva de menor potencia nominal, pero con variación continua de Ia misma. También existe un número indeterminado de cargas locales (14), como por ejemplo, las asociadas al rectificador o las que presenta cada aerogenerador.The corresponding filters (6) are included on both sides of the transmission system, which attenuate the level of harmonics produced by the controlled rectifier (9), as well as compensators (7), which provide the reactive power necessary for the operation of controlled rectifier (9). In this way, the filters (6) and the compensators (7) act as elements of the filter banks, which are switched on or off in a staggered manner according to the level of reactive power necessary for the operation of the controlled rectifier (9). In many cases, said filters (6) and the compensators (7) are complemented by synchronous or static compensators (STATCOM) (5), so that the stepwise variation of the reactive power produced between the connection of a bank and the next one is compensated by reactive power producing elements of lower nominal power, but with continuous variation thereof. There is also an undetermined number of local loads (14), such as those associated with the rectifier or those presented by each wind turbine.
Los sistemas propuestos hasta ahora consideran que Ia tensión, frecuencia y contenido armónico de Ia red de corriente alterna en el punto de conexión de los generadores (colector) deben ser mantenidas constantes. Este es el caso más común cuando se conectan dos buses de alterna mediante un enlace de continua y se pretende Ia transmisión de energía en cualquiera de los dos sentidos.The systems proposed so far consider that the voltage, frequency and harmonic content of the alternating current network at the connection point of the generators (collector) must be kept constant. This is the most common case when two alternating buses are connected through a continuous link and the transmission of energy in either of the two directions is intended.
En estos casos, el control de Ia potencia transmitida se realiza por medio de los impulsos de disparo aplicados a cada uno de los conversores. Generalmente, el conversor rectificador controla Ia corriente que circula por el enlace de continua y el conversor inversor controla Ia tensión del enlace de continua.In these cases, the control of the transmitted power is carried out by means of the trip impulses applied to each of the converters. Generally, the rectifier converter controls the current flowing through the DC link and the inverter converter controls the DC link voltage.
La presente invención consiste en un método de control por el cual Ia tensión, frecuencia y contenido armónico del bus de alterna donde se encuentran los generadores, es modificado para así controlar Ia tensión y/o Ia corriente del enlace de corriente continua y para reducir Ia necesidad de filtros (6) y compensación de reactiva (5 y 7).
La figura 2 muestra el sistema de transmisión de energía en continua propuesto. De forma similar a Ia configuración de Ia figura 1 , en Ia figura 2 se han representado un número de generadores (1) conectados directamente o a través de sistemas (2) electrónicos de potencia, junto con los correspondientes transformadores si fuera necesario, a una barra de alterna común o colector (4) mediante las correspondientes líneas de corriente alterna (3). Igualmente, puede haber bancos de compensación de potencia reactiva (7), filtros (6) y compensadores (5).The present invention consists of a control method whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located, is modified in order to control the voltage and / or the current of the direct current link and to reduce the Need for filters (6) and reactive compensation (5 and 7). Figure 2 shows the proposed continuous power transmission system. Similar to the configuration of Figure 1, in Figure 2 a number of generators (1) connected directly or through electronic power systems (2), together with the corresponding transformers if necessary, have been represented to a bar of alternating common or collector (4) by means of the corresponding lines of alternating current (3). Likewise, there may be reactive power compensation banks (7), filters (6) and compensators (5).
A diferencia del estado de Ia técnica general, el bus de corriente alterna (4) se conecta, mediante un transformador (8), a un conversor o rectificador no controlado (9a). Obviamente, si los generadores (1) cambian Ia tensión del colector (4) de forma continua, las tomas del transformador (8) resultan superfluas. De hecho, el cambiador de tomas del transformador (8) se utiliza para mantener el ángulo de disparo de las válvulas del rectificador controlado (9) en un rango determinado en estado estacionario y así reducir Ia demanda de potencia reactiva de dicho rectificador (9) . Con el uso de un rectificador no controlado (9a), el ángulo de disparo siempre es de cero grados y Ia demanda de potencia reactiva es mínima, sin necesidad del cambiador de tomas. De nuevo, el sistema propuesto conlleva Ia reducción de costes y el aumento de Ia robustez del sistema en su conjunto.Unlike the state of the general technique, the alternating current bus (4) is connected, by means of a transformer (8), to an uncontrolled converter or rectifier (9a). Obviously, if the generators (1) change the collector voltage (4) continuously, the transformer sockets (8) are superfluous. In fact, the tap changer of the transformer (8) is used to maintain the firing angle of the controlled rectifier valves (9) in a certain range in steady state and thus reduce the reactive power demand of said rectifier (9) . With the use of an uncontrolled rectifier (9a), the firing angle is always zero degrees and the reactive power demand is minimal, without the need for the tap-changer. Again, the proposed system entails reducing costs and increasing the robustness of the system as a whole.
La tensión instantánea del bus de corriente alterna (4) y, por Io tanto, Ia tensión eficaz, se controla actuando sobre los generadores (1), bien directamente, modificando su corriente magnetizante, o bien actuando sobre los sistemas electrónicos de potencia (2) que conectan los generadores al bus de alterna (4).The instantaneous voltage of the alternating current bus (4) and, therefore, the effective voltage, is controlled by acting on the generators (1), either directly, modifying its magnetizing current, or acting on the electronic power systems (2 ) that connect the generators to the alternating bus (4).
La variación de tensión en el bus de alterna (4) se refleja, idealmente en forma proporcional, en una variación en Ia tensión rectificada en el bus de continua (10), a través del rectificador no controlado (9a). De este modo se puede controlar Ia tensión en el bus de continua, ajustando Ia correspondiente tensión del bus de alterna. En este caso, el inversor (11) debería ser controlado para asegurar Ia circulación de corriente para lograr Ia transmisión de Ia potencia deseada.The voltage variation in the alternating bus (4) is ideally reflected proportionally in a variation in the rectified voltage in the continuous bus (10), through the uncontrolled rectifier (9a). In this way, the voltage in the continuous bus can be controlled, by adjusting the corresponding voltage of the alternating bus. In this case, the inverter (11) should be controlled to ensure the current circulation to achieve the transmission of the desired power.
Alternativamente, es posible medir Ia corriente continua a Ia salida del rectificador (9) y modificar Ia tensión del bus de continua (10) para obtener una corriente determinada en el bus de continua (10) según el método mencionado con anterioridad, es decir, variando Ia tensión instantánea del bus de corriente alterna (4). En este caso, el inversor (11) debería ser controlado para asegurar el nivel de tensión en el bus de continua (10) para lograr Ia transmisión de Ia potencia deseada. Al mismo tiempo, es posible variar Ia frecuencia de tensiones y corrientes del bus de alterna (4) para conseguir una variación continua de Ia potencia reactiva
entregada por los filtros, con Io que se limitarían los transitorios de conexión y desconexión de filtros y se podrían optimizar las pérdidas, controlando de forma continua el balance de energía reactiva. El control de frecuencia y de tensión del bus de alterna (4) se podría llevar a cabo de forma conjunta. El método de control propuesto también contempla Ia utilización de formas de onda de tensión y corrientes armónicas en el colector, Io que es equivalente a Ia utilización de formas de onda no senoidales. De este modo, es posible colaborar en el filtrado de los armónicos producidos por el rectificador, e incluso, llegar a Ia eliminación de los bancos de filtros utilizados para este propósito. El método de control propuesto podría complementar, si así se considerara necesario, al método propuesto en el documento WO 2006/035018 A2, y conseguir así las ventajas de dicho método de control, entre otras, una reducción del estrés térmico y de tensión de los distintos elementos del sistema y una disminución del riesgo de fallos de conmutación en el inversor. El método propuesto está especialmente indicado, entre otros casos, para su utilización en grandes parques eólicos situados a gran distancia de Ia red de transmisión (por ejemplo, parques eólicos marinos), en los que Ia tensión, potencia y frecuencia de los distintos aerogeneradores es controlada mediante conversores electrónicos.Alternatively, it is possible to measure the direct current at the output of the rectifier (9) and modify the voltage of the continuous bus (10) to obtain a certain current in the continuous bus (10) according to the method mentioned above, that is, varying the instantaneous voltage of the alternating current bus (4). In this case, the inverter (11) should be controlled to ensure the level of voltage in the continuous bus (10) to achieve the transmission of the desired power. At the same time, it is possible to vary the frequency of voltages and currents of the alternating bus (4) to achieve a continuous variation of the reactive power delivered by the filters, so that the transient connection and disconnection of filters would be limited and losses could be optimized, continuously controlling the reactive energy balance. The frequency and voltage control of the alternating bus (4) could be carried out jointly. The proposed control method also contemplates the use of voltage waveforms and harmonic currents in the collector, which is equivalent to the use of non-sinusoidal waveforms. In this way, it is possible to collaborate in the filtering of harmonics produced by the rectifier, and even to eliminate the filter banks used for this purpose. The proposed control method could complement, if deemed necessary, the method proposed in WO 2006/035018 A2, and thus achieve the advantages of said control method, among others, a reduction in thermal and stress stress of the different elements of the system and a decrease in the risk of switching faults in the inverter. The proposed method is especially indicated, among other cases, for use in large wind farms located a great distance from the transmission network (for example, offshore wind farms), in which the voltage, power and frequency of the different wind turbines is controlled by electronic converters.
Con este método de control se puede obviar el control del rectificador, y substituirlo por un rectificador no controlado. Las ventajas obtenidas de este método de operación son, entre otras:With this control method, the control of the rectifier can be ignored, and replaced by an uncontrolled rectifier. The advantages obtained from this method of operation are, among others:
• Eliminación de circuitos de disparo y de control del rectificador.• Elimination of trip circuits and rectifier control.
• Eliminación del compensador síncrono (STATCOM).• Elimination of synchronous compensator (STATCOM).
• Eliminación de Ia necesidad del cambiador de tomas en el lado del rectificador y, posiblemente, en el lado inversor.• Elimination of the need for the tap changer on the rectifier side and, possibly, on the inverter side.
• Operación natural en el ángulo de disparo que produce Ia mínima demanda de potencia reactiva y contenido armónico en Ia corriente.• Natural operation in the firing angle that produces the minimum demand for reactive power and harmonic content in the current.
• Aumento de Ia eficiencia del rectificador, ya que los diodos presentan menos pérdidas de conducción que los tiristores. • Reducción de costes del rectificador.• Increase the efficiency of the rectifier, since the diodes have less conduction losses than the thyristors. • Reduction of rectifier costs.
• Reducción o eliminación de los filtros de reactiva del lado rectificador.• Reduction or elimination of reagent filters on the rectifier side.
• Reducción o eliminación de los filtros de armónicos del lado rectificador.• Reduction or elimination of harmonic filters on the rectifier side.
• Reducción de peso del rectificador.• Rectifier weight reduction.
Las ventajas expuestas son especialmente relevantes, por ejemplo, en grandes parques eólicos marinos, en los cuales un aumento de Ia robustez del rectificador, a Ia
par que una disminución en su peso, representan beneficios económicos importantes en Ia puesta en marcha y operación del parque eólico.The exposed advantages are especially relevant, for example, in large offshore wind farms, in which an increase in the robustness of the rectifier, to the For a decrease in their weight, they represent important economic benefits in the implementation and operation of the wind farm.
Por otro lado, con el método de control propuesto se puede ajustar de forma continua Ia potencia reactiva proporcionada por los filtros (6) y compensadores (7), y minimizar las pérdidas producidas en líneas (3), (10) y transformadores (8), (12), mediante Ia variación de Ia tensión y Ia frecuencia del colector (4), bien de forma independiente o coordinada. De este modo, se podría reducir Ia potencia del compensador síncrono (5) requerido o eliminarlo por completo. De nuevo se consiguen importantes ventajas económicas, así como en Ia robustez del sistema de transmisión en su conjunto, al haber logrado eliminar un punto de fallo crítico.On the other hand, with the proposed control method, the reactive power provided by the filters (6) and compensators (7) can be continuously adjusted, and the losses produced in lines (3), (10) and transformers (8) can be minimized. ), (12), by means of the variation of the voltage and the frequency of the collector (4), either independently or in a coordinated manner. In this way, the power of the required synchronous compensator (5) could be reduced or eliminated completely. Again important economic advantages are achieved, as well as in the robustness of the transmission system as a whole, having managed to eliminate a point of critical failure.
Del mismo modo, Ia operación a frecuencias relativamente elevadas permite Ia reducción de las pérdidas en líneas y transformadores. Es previsible que las pérdidas en el rectificador aumenten al hacerlo Ia frecuencia del colector, por Io que es también posible ajustar Ia frecuencia dentro de un rango de modo que se minimicen las pérdidas globales.In the same way, the operation at relatively high frequencies allows the reduction of losses in lines and transformers. It is foreseeable that the losses in the rectifier will increase as the frequency of the collector increases, so that it is also possible to adjust the frequency within a range so that the overall losses are minimized.
A continuación se presentan dos ejemplos de empleo de este método.Below are two examples of using this method.
Ejemplo 1Example 1
Utilización del método de control y del sistema de transmisión con rectificador no controlado y transformador sin cambiador de tomas en parques eólicos con aerogeneradores basados en generadores asincronos de inducción de doble alimentación.Use of the control method and the transmission system with uncontrolled rectifier and transformer without tap-changer in wind farms with wind turbines based on asynchronous double-feed induction generators.
Este tipo de generadores está caracterizado por Ia conexión directa del estator a Ia red, mientras que su control se realiza mediante conversores CA/CC/CA que conectan el rotor del generador con Ia red de corriente alterna. Presentan Ia gran ventaja que Ia potencia nominal de los conversores electrónicos utilizados es una fracción de Ia potencia nominal del conjunto.This type of generators is characterized by the direct connection of the stator to the network, while its control is carried out by means of AC / DC / AC converters that connect the generator rotor with the alternating current network. They have the great advantage that the nominal power of the electronic converters used is a fraction of the nominal power of the set.
La tensión de estator de los generadores, que están directamente conectado al colector (o bien a través de uno o varios transformadores), se puede reducir fácilmente mediante técnicas de debilitamiento de flujo. Dicha reducción de tensión permite controlar Ia corriente que circula por el enlace de corriente continua.The stator voltage of the generators, which are directly connected to the collector (or through one or more transformers), can be easily reduced by flow weakening techniques. Said voltage reduction allows controlling the current flowing through the direct current link.
Como desventaja, se tiene que Ia operación a flujo reducido implica necesariamente una reducción en Ia potencia máxima que puede entregar el generador. Sin embargo, dicha reducción de flujo y tensión se produce necesariamente cuando Ia energía presente en el viento se reduce y,
consecuentemente es necesario reducir Ia energía transmitida por el enlace de continua.As a disadvantage, it is that the operation at reduced flow necessarily implies a reduction in the maximum power that the generator can deliver. However, said reduction of flow and tension necessarily occurs when the energy present in the wind is reduced and, consequently it is necessary to reduce the energy transmitted by the continuous link.
El margen de reducción de tensión producido por los aerogeneradores no es, generalmente, excesivamente grande, pero este pequeño margen de variación es suficiente para controlar Ia corriente por el enlace de corriente continua. En este caso, Ia tensión de continua sería controlada por el conversor inversor.The voltage reduction range produced by the wind turbines is not generally excessively large, but this small variation margin is sufficient to control the current through the direct current link. In this case, the DC voltage would be controlled by the inverter converter.
Como ventaja adicional se tiene que las pérdidas en el hierro de los generadores y transformadores se verían reducidas al operar a una tensión inferior a Ia nominal. Además, Ia operación a tensión reducida en el estator permite asimismo, Ia reducción en Ia tensión de rotor, con Io que se amplía el rango de velocidades de operación de Ia turbina, siendo capaz de extraer mayor energía a velocidades bajas de viento.As an additional advantage, the iron losses of the generators and transformers would be reduced when operating at a voltage lower than the nominal voltage. In addition, the operation at reduced voltage in the stator also allows the reduction in the rotor voltage, with which the range of operating speeds of the turbine is extended, being able to extract more energy at low wind speeds.
El sistema descrito no necesitaría de transformador con cambiador de tomas, aunque en ciertos casos podría requerir de filtrado suficiente para mitigar los armónicos producidos por el rectificador.The system described would not require a transformer with tap changer, although in certain cases it may require sufficient filtering to mitigate the harmonics produced by the rectifier.
Contando con Ia capacidad de generación de potencia reactiva de los aerogeneradores actuales, el valor de los bancos de reactiva necesarios se podría reducir respecto de los utilizados con los sistemas de transmisión de continua que utilizan un rectificador controlado. Estos bancos quizás podrían ser eliminados con el adecuado diseño y/o selección apropiada de aerogeneradores.With the reactive power generation capacity of the current wind turbines, the value of the necessary reactive banks could be reduced compared to those used with the continuous transmission systems that use a controlled rectifier. These banks could perhaps be eliminated with the proper design and / or appropriate selection of wind turbines.
Ejemplo 2Example 2
Utilización del método de control y del sistema de transmisión con rectificador no controlado y transformador sin cambiador de tomas en parques eólicos con aerogeneradores basados en generadores síncronos.Use of the control method and transmission system with uncontrolled rectifier and transformer without tap changer in wind farms with wind turbines based on synchronous generators.
Los aerogeneradores basados en generadores síncronos se conectan a Ia red a través de convertidores CA/CC/CA (o CA/CA) de potencia nominal igual a Ia del generador. Este tipo de conversores implican un gasto mayor que en los generadores asincronos de doble alimentación, sin embargo, proporcionan, entre otras ventajas, una mayor flexibilidad en el control, un mayor rango de velocidades de operación de Ia turbina y un mejor comportamiento ante transitorios en Ia red eléctrica.Wind turbines based on synchronous generators are connected to the network through AC / DC / AC (or AC / AC) converters of nominal power equal to that of the generator. This type of converters implies a greater expense than in the double-feed asynchronous generators, however, they provide, among other advantages, a greater flexibility in the control, a greater range of operating speeds of the turbine and a better behavior before transients in The electricity network.
Este tipo de aerogeneradores pueden utilizar el método de control descrito para así regular Ia corriente circulante por el enlace de continua. Del mismo modo, Ia rápida respuesta de este tipo de aerogeneradores permite que los propios aerogeneradores sean capaces de controlar las corrientes que circulan en las instalaciones de alterna y de continua de alta tensión durante fallos y transitorios.
Dado que los conversores de los aerogeneradores pueden realizar Ia regulación constante de tensión, es posible eliminar los cambios de tomas de los distintos transformadores. Además, los conversores de este tipo de aerogeneradores pueden proporcionar cierto nivel de potencia reactiva e incluso de corrientes armónicas, con Io que los valores nominales de los filtros de armónicos y reactiva pueden disminuirse o incluso eliminarse.This type of wind turbines can use the described control method to regulate the current flowing through the continuous link. In the same way, the rapid response of this type of wind turbines allows the wind turbines themselves to be able to control the currents that circulate in the alternating and high-voltage continuous installations during faults and transients. Since the converters of the wind turbines can carry out the constant voltage regulation, it is possible to eliminate the changes of sockets of the different transformers. In addition, converters of this type of wind turbines can provide a certain level of reactive power and even harmonic currents, so that the nominal values of the harmonic and reactive filters can be lowered or even eliminated.
Por otro lado, es posible modificar, de forma sencilla, Ia frecuencia del lado de alterna, de modo que se consiga reducir las pérdidas y, al mismo tiempo, regular Ia potencia reactiva producida por los distintos filtros.
On the other hand, it is possible to modify, in a simple way, the frequency of the alternating side, so that it is possible to reduce the losses and, at the same time, regulate the reactive power produced by the different filters.
Claims
1. - Sistema de transmisión de energía eléctrica con enlace de corriente continua que consta de unos generadores eléctricos (1) conectados a un colector o bus de corriente alterna (4), directamente o a través de un sistema (2) de conexionado consistente en sistemas electrónicos de potencia y/o transformadores, con sus correspondientes líneas eléctricas (3), contando con unos filtros (6) y compensadores de potencia reactiva (7), caracterizado por que el colector o bus de corriente alterna (4), se conecta, mediante uno o varios transformadores (8), a un conversor o rectificador no controlado (9a), de manera que el ángulo de desplazamiento entre tensión y corriente sea mínimo, así como su demanda de potencia reactiva.1. - Electric power transmission system with direct current link consisting of electric generators (1) connected to an AC collector or bus (4), directly or through a connection system (2) consisting of systems power electronics and / or transformers, with their corresponding power lines (3), with some filters (6) and reactive power compensators (7), characterized in that the collector or alternating current bus (4) is connected, by one or several transformers (8), to an uncontrolled converter or rectifier (9a), so that the angle of displacement between voltage and current is minimal, as well as its reactive power demand.
2. - Sistema de transmisión de energía eléctrica con enlace de corriente continua según Ia reivindicación 1 caracterizado por que el rectificador no controlado (9a) alimenta una línea de corriente continua (10) que se conecta a Ia red de receptora de corriente alterna (13) a través de un inversor (11), adecuando Ia tensión mediante uno o varios transformadores (12).2. - Electric power transmission system with direct current link according to claim 1 characterized in that the uncontrolled rectifier (9a) feeds a direct current line (10) that connects to the alternating current receiver network (13 ) through an inverter (11), adapting the voltage by one or several transformers (12).
3. - Método de control y transmisión de energía eléctrica en una red de transporte de energía eléctrica, por el cual Ia tensión, Ia frecuencia y el contenido armónico del bus de alterna donde se encuentran los generadores son modificados para controlar Ia tensión y/o Ia corriente del enlace de corriente continua de un sistema de transmisión de energía eléctrica en una red de transporte de energía eléctrica, que consta de unos generadores eléctricos (1) conectados a un colector o bus de corriente alterna (4), directamente o a través de un sistema (2) de conexionado consistente en sistemas electrónicos de potencia y/o transformadores, con sus correspondientes líneas eléctricas (3), contando con unos filtros (6) y compensadores de potencia reactiva (7), caracterizado por que el colector o bus de corriente alterna (4), se conecta, mediante uno o varios transformadores (8), a un conversor o rectificador no controlado (9a), de manera que el ángulo de desplazamiento entre tensión y corriente sea mínimo, así como su demanda de potencia reactiva, sin necesidad del cambiador de tomas.3. - Method of control and transmission of electrical energy in an electrical energy transport network, whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located are modified to control the voltage and / or The current of the direct current link of an electric power transmission system in an electric power transport network, which consists of electric generators (1) connected to an alternating current bus or bus (4), directly or through a connection system (2) consisting of electronic power systems and / or transformers, with their corresponding power lines (3), with filters (6) and reactive power compensators (7), characterized in that the collector or bus of alternating current (4), it is connected, by one or several transformers (8), to an uncontrolled converter or rectifier (9a), so that the angle of travel between Minimum voltage and current, as well as your reactive power demand, without the need for the tap-changer.
4. - Método de control y transmisión de energía eléctrica en una red de transporte de energía eléctrica según Ia reivindicación 3 caracterizado por que el rectificador no controlado (9a) alimenta una línea de corriente continua (10) que se conecta a Ia red de receptora de corriente alterna (13) a través de un inversor (11), adecuando Ia tensión mediante uno o varios transformadores (12).4. - Method of control and transmission of electric energy in an electric power transport network according to claim 3 characterized in that the uncontrolled rectifier (9a) feeds a direct current line (10) that is Connects to the alternating current receiver network (13) through an inverter (11), adapting the voltage through one or more transformers (12).
5. - Método de control y transmisión de energía eléctrica en una red de transporte de energía eléctrica, por el cual Ia tensión, Ia frecuencia y el contenido armónico del bus de alterna donde se encuentran los generadores son modificados para controlar Ia tensión y/o Ia corriente del enlace de corriente continua de un sistema de transmisión de energía eléctrica en una red de transporte de energía eléctrica, que consta de unos generadores eléctricos (1) conectados a un colector o bus de corriente alterna (4), directamente o a través de un sistema (2) de conexionado consistente en sistemas electrónicos de potencia y/o transformadores, con sus correspondientes líneas eléctricas (3), contando con unos filtros (6) y compensadores de potencia reactiva (7), caracterizado por que el colector o bus de corriente alterna (4), se conecta, mediante uno o varios transformadores (8), a un conversor o rectificador controlado (9), de manera que se elimine el cambiador de tomas de los transformadores (8) y se reduzcan o eliminen los sistemas de filtrado (6) y compensación de reactiva (7).5. - Method of control and transmission of electrical energy in an electrical energy transport network, whereby the voltage, frequency and harmonic content of the alternating bus where the generators are located are modified to control the voltage and / or The current of the direct current link of an electric power transmission system in an electric power transport network, which consists of electric generators (1) connected to an alternating current bus or bus (4), directly or through a connection system (2) consisting of electronic power systems and / or transformers, with their corresponding power lines (3), with filters (6) and reactive power compensators (7), characterized in that the collector or bus of alternating current (4), it is connected, by one or several transformers (8), to a controlled converter or rectifier (9), so that the tap changer of the transformers (8) and the filtration systems (6) and reagent compensation (7) are reduced or eliminated.
6. - Método de control y transmisión de energía eléctrica en una red de transporte de energía eléctrica según Ia reivindicación 5 caracterizado por que el rectificador controlado (9) alimenta una línea de corriente continua (10) que se conecta a Ia red de receptora de corriente alterna (13) a través de un inversor (11), adecuando Ia tensión mediante uno o varios transformadores (12). 6. - Method of control and transmission of electrical energy in an electrical energy transport network according to claim 5, characterized in that the controlled rectifier (9) feeds a direct current line (10) that is connected to the receiver network of alternating current (13) through an inverter (11), adapting the voltage by one or several transformers (12).
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ES200802377A ES2358816B1 (en) | 2008-07-31 | 2008-07-31 | METHOD AND SYSTEM OF CONTROL AND TRANSMISSION OF ELECTRICAL POWER WITH CONTINUOUS CURRENT LINK. |
ESP200802377 | 2008-07-31 |
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WO2012162570A1 (en) * | 2011-05-24 | 2012-11-29 | Cameron D Kevin | System and method for integrating and managing demand/response between alternative energy sources, grid power, and loads |
CN105939020A (en) * | 2016-05-14 | 2016-09-14 | 国家电网公司 | Station-configuration method for dynamic reactive compensation apparatus capable of improving multi-feed direct current restoration capability |
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ES2584535B2 (en) * | 2015-03-27 | 2017-06-21 | Universidad Carlos Iii De Madrid | Method and system for voltage and frequency control in an isolated network |
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WO2012162570A1 (en) * | 2011-05-24 | 2012-11-29 | Cameron D Kevin | System and method for integrating and managing demand/response between alternative energy sources, grid power, and loads |
CN105939020A (en) * | 2016-05-14 | 2016-09-14 | 国家电网公司 | Station-configuration method for dynamic reactive compensation apparatus capable of improving multi-feed direct current restoration capability |
CN106229999A (en) * | 2016-08-30 | 2016-12-14 | 中石化南京工程有限公司 | A kind of low-pressure reactive compensation current sampling method |
CN106229999B (en) * | 2016-08-30 | 2019-01-15 | 中石化南京工程有限公司 | A kind of low-pressure reactive compensation current sampling method |
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WO2010018264A4 (en) | 2010-05-06 |
ES2358816A1 (en) | 2011-05-16 |
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