CN207801488U - Current transformer, electric-control system and wind power plant transmission system - Google Patents
Current transformer, electric-control system and wind power plant transmission system Download PDFInfo
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- CN207801488U CN207801488U CN201721850253.3U CN201721850253U CN207801488U CN 207801488 U CN207801488 U CN 207801488U CN 201721850253 U CN201721850253 U CN 201721850253U CN 207801488 U CN207801488 U CN 207801488U
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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
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- 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
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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
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Abstract
The utility model discloses a kind of current transformer, electric-control system and wind power plant transmission systems.The current transformer includes three concatenated power strings；Wherein, each concatenated power string includes first lead-out terminal and second output terminal, and asterism connection is formed between the first lead-out terminal of each concatenated power string, and second output terminal of each concatenated power string forms three-phase output；The three-phase input of each concatenated power string and the direct wind-driven generator of wind power generating set connect.According to the current transformer that the utility model embodiment provides, the output voltage of current transformer can be increased, output current is reduced, reduces the loss of machine system, and the use of a large amount of low-voltage cables can be reduced, alleviate the pressure of untying the mooring rope of blower fan system.
Description
Technical Field
The invention relates to the technical field of wind power integration, in particular to a converter and an electric control system for a wind power plant power transmission system and a wind power plant power transmission system.
Background
With the aggravation of the energy crisis, the development and utilization of new energy have become the hot spots of research, and wind power is the renewable energy with large-scale development potential at present. The wind generating set is an electric power device which converts wind energy into mechanical energy, and the mechanical energy drives a generator rotor to rotate so as to finally output alternating current. Because wind resources in China are distributed more intensively, a large-scale and highly-centralized access and remote transmission mode is adopted for wind power development. In order to ensure the voltage stability of the low-frequency alternating current output by the wind generating set, the low-frequency alternating current output by the wind generating set is generally converted into direct current electric energy through rectification, and the direct current electric energy is converted into alternating current commercial power through an inverter circuit, so that the stable use can be ensured.
In the existing power transmission system of a wind generating set, the transmission and conversion process of the electric energy is generally realized by using a converter. In practical application, a generator of the wind generating set is located in an engine room at the top of the tower, the converter is generally located in a tower barrel at the bottom of the tower of the wind generating set, and a large number of low-voltage cables need to be transmitted to the converter at the bottom of the tower through a high tower barrel, so that the number of cables used in the tower barrel is large, and great pressure is caused to cable untwisting of a fan system.
In addition, the voltage output by the converter is low, the output current is high, a large amount of low-voltage cables made of precious metals are needed, and the loss of the whole system is high.
Disclosure of Invention
The embodiment of the invention provides a converter, an electric control system and a wind power plant power transmission system for a wind power plant power transmission system, which can increase the output voltage of the converter, reduce the output current, reduce the loss of the whole system, reduce the use of a large number of low-voltage cables and relieve the cable release pressure of a fan system.
According to an aspect of an embodiment of the present invention, a converter for a power transmission system of a wind farm is provided, which includes three cascaded power strings; each cascade power string comprises a first output terminal and a second output terminal, star point connection is formed between the first output terminals of each cascade power string, and the second output terminal of each cascade power string forms three-phase output; and the three-phase input of each cascade power string is connected with a direct-drive wind driven generator of the wind driven generator set.
According to another aspect of the embodiment of the invention, an electric control system for a power transmission system of a wind power plant is provided, which comprises a direct-drive wind driven generator and a converter in the embodiment; a direct-drive wind power generator configured to include a plurality of windings, the number of the plurality of windings is 3N, and every three windings form a group of three-phase windings, wherein N is an integer greater than or equal to 3; the converter is configured to be connected with the direct-drive wind driven generator through a plurality of windings.
According to another aspect of the embodiment of the invention, a wind power plant power transmission system is provided, which comprises the electric control system, a plurality of groups of power frequency step-up transformers and a medium voltage power supply bus, which are described in the embodiment; the low-voltage side of each group of power frequency step-up transformers is connected with one group of electric control systems in the plurality of groups of electric control systems, and each group of power frequency step-up transformers is connected with a medium-voltage power supply bus in a three-phase mode through inductors; the multiple groups of power frequency step-up transformers are configured to convert power frequency alternating current electric energy which is output by the multiple groups of electric control systems and meets the requirements of a power grid into medium-voltage alternating current electric energy which meets the requirements of the power grid, and the medium-voltage alternating current electric energy obtained through conversion is connected to a medium-voltage power supply bus.
According to the converter, the electric control system and the wind farm power transmission system in the embodiment of the invention, the output voltage of the converter can be increased, the output current can be reduced, the use of large-batch low-voltage cables can be reduced, and the loss of the whole system can be reduced by a modular cascade mode through the cascade power strings in the converter. Meanwhile, the converter in the embodiment of the invention can avoid the selection that the current low-voltage large-capacity converter needs to be connected in parallel to increase the capacity, thereby avoiding the technical problems of current equalization, circulation and the like of parallel cables and improving the reliability of a fan system.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram showing the structure and position of a current transformer currently used in wind power plants;
FIG. 2 is a schematic diagram showing a topology of an electric control system of a current transformer based wind generating set;
fig. 3 is a schematic structural diagram illustrating a current transformer provided according to an embodiment of the present invention;
fig. 4 is a detailed structural schematic diagram illustrating a current transformer according to some exemplary embodiments of the present invention;
fig. 5 is a schematic diagram showing a specific structure of a power unit according to an embodiment of the present invention;
fig. 6 is a schematic structural view illustrating an electronic control system provided according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating a wind farm power transmission system according to an embodiment of the invention.
In the drawings, like parts are designated with like reference numerals throughout and are described as follows:
10-a wind generating set; 20-an electronic control system; 21-direct drive motor; 2201-a first current transformer; 2202-a second current transformer;
200-direct drive wind driven generator; 300-a current transformer; 310-a first cascaded power string; 320-a second cascaded power string; 330-third cascaded power string;
3111-three-phase rectifier module; 3112-bus capacitor and discharge resistor module; 3113-a chopper circuit module; 3114-H bridge arm inverter module;
600-an electronic control system; 610-a pitch control system; 620-master control system;
700-a wind farm power transmission system; 710-multiple groups of power frequency step-up transformers; 720-medium voltage power supply bus; 730-step-up transmission transformer; 740-connecting alternating current electric energy into an alternating current transmission bus; 750-reactive compensation device.
Detailed Description
Features and exemplary embodiments of various aspects of the present invention will be described in detail below, and in order to make objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Fig. 1 is a schematic diagram showing the structure and position of a current transformer currently used for a wind turbine. As shown in fig. 1, a generator of a wind turbine generator system is usually located in a nacelle at the top of a tower, a converter is usually located in a tower at the bottom of the tower of the wind turbine generator system, a large number of low-voltage cables are transmitted to the converter at the bottom of the tower through a high tower, the converter rectifies low-frequency ac power output by the wind turbine generator system to convert the low-frequency ac power into dc power, and the dc power is converted into ac power by an inverter circuit to be connected.
However, the number of cables used in the tower is large due to the position arrangement of the converter, and the cable untwisting pressure of the wind turbine system is large.
Fig. 2 is a schematic diagram showing the topology of the current wind turbine converter-based electric control system. As shown in fig. 2, the electric control system 20 includes a direct drive motor 21, a first converter 2201 and a second converter 2202, wherein the direct drive motor 21 is connected to the wind turbine 10. As can be seen from fig. 2, the conventional converter can be directly used as a converter system by the first converter 2201 or the converter 2202. For example, the three phases on the wind turbine side of the first converter 2201 are connected to the three-phase windings of the direct drive motor stator via inductors; the three phases on the grid side of the first converter 2201 are coupled via inductors to other electrical devices in the grid, such as step-up transformers (not shown).
However, the converter has low output voltage and large current, and needs a large amount of low-voltage cables made of noble metals, so that the loss of the whole system is large.
With the capacity of the wind generating set increasing, the low-voltage converter needs to be connected in parallel to enlarge the capacity. As shown in fig. 2, the converters may be composed of a first converter 2201 and a second converter 2202 to form a converter parallel system, and on the wind power generator side of the converter parallel system, three phases of each converter are connected with three-phase windings of a stator of a direct drive motor through inductors; on the grid side of the parallel converter system, the ac output of each converter is connected in parallel to the low voltage side of other electrical devices in the grid, such as step-up transformers.
However, a converter parallel system obtained by connecting low-voltage converters in parallel is prone to cause a serious circulation problem, and the circulation problem can cause that the current-sharing characteristic of the output current of the low-voltage converter parallel system cannot achieve an ideal effect, so that the reliability of a fan system is affected.
Based on the reasons, the embodiment of the invention provides the converter for the power transmission system of the wind power plant, which changes the internal electrical structure of the converter, can increase the output voltage of the converter, reduce the output current, reduce the loss of the whole system, reduce the use of a large number of low-voltage cables, relieve the cable releasing pressure of a fan system and improve the reliability of the fan system.
For a better understanding of the present invention, the following detailed description of the converter, the electric control system and the wind farm power transmission system according to the embodiments of the present invention will be made with reference to the accompanying drawings, and it should be noted that these embodiments are not intended to limit the scope of the present disclosure.
Fig. 3 shows a schematic structural diagram of a current transformer according to an embodiment of the present invention. As shown in fig. 3, the converter 300 may specifically include three cascaded power strings, where each cascaded power string may include a first output terminal and a second output terminal, the first output terminal of each cascaded power string forms a star point connection therebetween, and the second output terminal of each cascaded power string forms a three-phase output of the converter 300; and the three-phase input of each cascade power string is connected with a direct-drive wind driven generator of the wind driven generator set.
In the embodiment, the three cascade power strings are configured to convert alternating current output by the direct-drive wind power generator into power frequency alternating current electric energy meeting the requirements of a power grid.
As an example, as shown in fig. 3, the converter 300 may include a first cascaded power string 310, a second cascaded power string 320, and a third cascaded power string 330.
With continued reference to fig. 3, a star point connection is formed between the first output terminal of the first cascaded power string 310, the first output terminal of the second cascaded power string 320, and the first output terminal of the third cascaded power string 330; the second output terminal of the first cascaded power string 310, the second output terminal of the second cascaded power string 320, and the second output terminal of the third cascaded power string 330 form a three-phase output.
The converter of the embodiment of the present invention is a three-phase system formed by a first cascade power string 310, a second cascade power string 320, and a third cascade power string 330. The design that a single converter in the traditional converter can directly form a converter system is changed, the output voltage of the converter is increased in a modular cascade mode, the output current is greatly reduced, the use of large-batch low-voltage cables is reduced, the loss is reduced, and the efficiency is improved; meanwhile, the selection that the capacity of the current low-voltage high-capacity converter must be increased in parallel is avoided, the technical problems of current equalization, circulation and the like are avoided, and the reliability of the fan system is improved.
Fig. 4 shows a detailed structural schematic diagram of a current transformer according to some exemplary embodiments of the present invention, and the same reference numerals are used for the same or equivalent structures in fig. 4 as in fig. 3. As shown in fig. 4, the converter 300 includes a first cascaded power string 310, a second cascaded power string 320, and a third cascaded power string 330, wherein the first cascaded power string 310 includes a plurality of power cells such as power cell _ a1, power cells _ a2, … …, and power cell _ aN; the second cascaded power string 320 includes a plurality of power cells such as power cell _ b1, power cell _ b2, … …, power cell _ bN; the third cascaded power string 330 includes a plurality of power cells such as power cell _ c1, power cell _ c2, … …, power cell _ cN. The invention is not limited to the specific modules described above and shown in fig. 4, and in some embodiments the cascaded power strings in converter 300 may comprise a more flexible configuration, as described below in connection with specific embodiments.
In one embodiment, each cascaded power string of converter 300 comprises a plurality of power cells, wherein the three-phase input of each power cell of the plurality of power cells is connected with a set of three-phase windings of a direct-drive wind turbine in a one-to-one correspondence; a plurality of power units of each cascade power string are connected in series; each power unit comprises a first alternating current output terminal and a second alternating current output terminal, the second alternating current terminal of the previous power unit in the two adjacent power units in each cascaded power string is connected with the first alternating current terminal of the next power unit, the first alternating current terminal of the first power unit connected in series in each cascaded power string is used as the first output terminal of each cascaded power string, and the second alternating current terminal of the last power unit connected in series in each cascaded power string is used as the second output terminal of each cascaded power string.
That is, for a plurality of power cells connected in series in each cascade power string, the first alternating current terminal of each power cell except for the first power cell connected in series and the last power cell connected in series may be connected to the second alternating current terminal of the last power cell connected in series thereto, and the second alternating current terminal thereof may be connected to the first alternating current terminal of the next power cell connected in series thereto.
As an example, when each cascaded power string of the converter 300 includes three power units, that is, the first cascaded power string 310 in the cascaded power strings includes power units of power unit _ a1, power unit _ a2, and power unit _ a3, the second cascaded power string 320 includes power units of power unit _ b1, power unit _ b2, and power unit _ b3, and the third cascaded power string 330 includes power units of power unit _ c1, power unit _ c2, and power unit _ c 3.
In this example, the three phase input of power unit _ a1, the three phase input of power unit _ a2, the three phase input of power unit _ a3, the three phase input of power unit _ b1, the three phase input of power unit _ b2, the three phase input of power unit _ b3, the three phase input of power unit _ c1, the three phase input of power unit _ c2, and the three phase input of power unit _ c3 are connected to a set of three phase windings of a direct drive wind generator, respectively;
in the first cascaded power string 310, power unit _ a1, power unit _ a2, and power unit _ a3 are connected in series, in the second cascaded power string 320, power unit _ b1, power unit _ b2, and power unit _ b3 are connected in series, and in the third cascaded power string 330, power unit _ c1, power unit _ c2, and power unit _ c3 are connected in series.
The first ac output terminal of power cell _ a1 as the first output terminal of the first cascaded power string 310, the first ac output terminal of power cell _ b1 as the first output terminal of the second cascaded power string 320, and the first ac output terminal of power cell _ c1 as the first output terminal of the third cascaded power string 330, and the first output terminal of each cascaded power string, i.e., the first ac output terminal of power cell _ a1, the first ac output terminal of power cell _ b1, and the first ac output terminal of power cell _ c1, form a star point connection therebetween;
the second ac output terminal of power cell _ a3 as the second output terminal of the first cascaded power string 310, the second ac output terminal of power cell _ b3 as the second output terminal of the second cascaded power string 320, and the second ac output terminal of power cell _ c3 as the second output terminal of the third cascaded power string 330, and the second output terminal of each cascaded power string, i.e., the second ac output terminal of power cell _ a3, the second ac output terminal of power cell _ b3, and the second ac output terminal of power cell _ c3, form the three-phase output of the converter 300.
In this example, in the first cascaded power string 310, the second ac output terminal of power cell _ a1 is connected with the first ac output terminal of power cell _ a2, and the second ac output terminal of power cell _ a2 is connected with the first ac output terminal of power cell _ a 3;
in the second cascade power string 320, the second ac output terminal of the power cell _ b1 is connected to the first ac output terminal of the power cell _ b2, and the second ac output terminal of the power cell _ b2 is connected to the first ac output terminal of the power cell _ b 3;
in the third cascade power string 330, the second ac output terminal of the power cell _ c1 is connected to the first ac output terminal of the power cell _ c2, and the second ac output terminal of the power cell _ c2 is connected to the first ac output terminal of the power cell _ c 3.
In some embodiments, each cascaded power string in converter 300 may include a greater number of power cells, i.e., the number of power cells in each cascaded power string may be equal to or greater than 3.
As shown in fig. 4, the converter 300 includes three cascaded power strings, each cascaded power string includes N power units, each power unit has a set of three-phase input ends, the direct-drive wind power generator in the embodiment of the present invention is a multi-winding direct-drive wind power generator, a rotor of the multi-winding direct-drive wind power generator is coaxially connected to a wind power generator set, a stator of the multi-winding direct-drive wind power generator includes 3N windings, and N is an integer greater than or equal to 3, wherein each 3 windings form a set of three-phase outputs of the multi-winding direct-drive wind power generator, and the N sets of three-phase outputs of the doubly-fed generator are respectively and correspondingly connected to the three-phase input ends of the N power units of.
In the embodiment of the invention, the output voltage of the converter can be restricted by limiting the number of windings of the stator in the multi-winding direct-drive wind driven generator. Therefore, the converter of the embodiment of the invention can superpose and output higher voltage by carrying out modular cascade connection on the power units in each cascade power string, thereby greatly reducing output current and having the advantages of less output harmonic waves and high modularization degree; meanwhile, the method is different from the selection of the current low-voltage high-capacity converter for improving the capacity of the converter in parallel connection, so that the technical problems of current equalization, circulation and the like are avoided, and the reliability of a fan system is improved.
Fig. 5 shows a specific structural diagram of a power unit according to an embodiment of the invention. As shown in fig. 5, as one of the power units of one of the cascaded power strings of the converter 300, the power unit may include a three-phase rectifier module 3111, a bus capacitor and discharge resistor 3112, a chopper circuit module 3113, and an H-bridge arm inverter module 3114, which are connected in sequence.
As shown in fig. 5, the three-phase rectifier module 3111 is configured to be connected with one set of three-phase windings of the direct-drive wind turbine via three-phase inductors, and is configured to rectify low-frequency ac power output by the direct-drive wind turbine and convert the low-frequency ac power into dc power.
As one example, the three-phase rectifier module may be, for example, a three-phase PWM rectifier.
And a bus capacitor and discharge resistor 3112 configured to be connected to two output terminals of the three-phase rectifier module. In fig. 5, the bus capacitor may be configured to filter and store the converted dc power, and the discharge resistor may be configured to discharge the amount of power stored in the bus capacitor.
The chopper circuit module 3113 is configured to discharge energy in the dc bus exceeding a preset dc bus voltage threshold through an energy discharge resistor in the chopper circuit module 3113 when the dc bus voltage exceeds the preset dc bus voltage threshold.
As shown in fig. 5, the chopper circuit module 3113 may include a switching tube Q1 and a dump resistor R connected in series between the dc bus bars. As an example, the switching tube Q1 may be an Insulated Gate Bipolar Transistor (IGBT). In this example, the chopper circuit module 3113 may further include a switching tube Q2 connected in parallel with the dump resistor R, the switching tube Q2 may be any one of an IGBT including a diode, a MOS tube with a diode, or a diode, and in the chopper circuit module 3113, the switching tube Q2 may be used as a diode.
In this embodiment, when a working condition such as low voltage ride through occurs in a power grid of a wind farm, causing a pump-up of a dc bus voltage, and the dc bus voltage exceeds a preset dc bus voltage threshold, the switching tube Q1 in the chopper circuit module 3113 connected in series with an energy discharging resistor may be controlled to be turned on, so that energy pumped up in the dc bus is discharged through the switching tube Q1 and the energy discharging resistor R, thereby preventing overvoltage of the dc bus.
And the H-type bridge arm inverter module 3114 is configured to convert the voltage-adjustable dc power into power frequency ac power meeting the power grid requirement.
In one embodiment, as shown in fig. 5, an H-bridge arm inverter module (which may be referred to as an H-bridge in the following description) includes two parallel bridge arms, each of which includes two power tube units connected in series; two output ends of the H-type bridge arm inverter module are a first alternating current terminal and the second alternating current terminal.
In the embodiment of the invention, the input of each power unit of the cascaded power string in the converter is connected with a group of three-phase windings of the multi-winding direct current generator, and the output of the power unit is two-way alternating current output terminals of the H-type bridge arm inverter module, wherein a first alternating current terminal of the H bridge is connected with a second alternating current terminal of the last power unit connected in series, and a second alternating current terminal of the H bridge is connected with a first alternating current terminal of the next power unit connected in series.
Fig. 6 is a schematic structural diagram of an electronic control system according to an embodiment of the present invention. As shown in fig. 6, in one embodiment, the electronic control system 600 may include:
the direct drive wind turbine 200 and the converter 300 described in the above embodiments; the direct-drive wind power generator 200 is configured to include a plurality of windings, the number of the plurality of windings may be 3N, and N is a positive integer greater than or equal to 3. Wherein, every three windings form a group of three-phase windings; the converter 300 is configured to be connected with the direct-drive wind power generator through a plurality of windings.
In this embodiment, the motor rotor of the direct drive wind power generator 200 is directly connected with the wind wheel of the wind turbine generator set 100 for driving, and the converter connected with the direct drive wind power generator 200 may be a full power converter.
With continued reference to fig. 5, in one embodiment, the electronic control system 600 may further include: pitch control system 610 and master control system 620.
In one embodiment, pitch control system 610 may be configured to adjust a blade pitch angle (or pitch angle for short) of the wind turbine generator set as the wind speed changes, thereby stabilizing the output power of the generator. Specifically, the pitch control system 610 may control a position angle, i.e., a pitch angle, of a chord length of a blade of the wind turbine generator with respect to a rotation plane, and when a wind speed is higher than a rated wind speed, the pitch angle of the blade is adjusted to control a pneumatic torque and a pneumatic power captured by the wind turbine, so that the wind turbine can capture wind energy to the maximum extent and output power stably.
In one embodiment, master control system 620 may be configured to communicate with pitch control system 610 and converter 300, issue pitch control commands to pitch control system 610, and communicate with converter 300 to control the converter to regulate the active and reactive power of the wind turbine.
Specifically, the main control system 620 may receive signals of the nacelle cabinet and the pitch control system, communicate with the pitch control system 610, and send a pitch control instruction to the pitch control system 610 to control the pitch control system to complete adjustment of the blade pitch angle, thereby achieving maximum wind energy capture and constant-speed operation; and is used to control the converter 300 to adjust the active and reactive power of the wind turbine; and communicate with a central control system, transfer information, etc.
In this embodiment, the main control system 620 is a main body of a control system of the wind turbine, and can implement important control and protection functions of automatic start, automatic direction adjustment, automatic speed adjustment, automatic grid connection, automatic fault shutdown, automatic cable unwinding, automatic recording and monitoring, and the like of the wind turbine.
Fig. 7 is a schematic diagram showing the structure of a wind farm power transmission system according to an embodiment of the invention, and the same or equivalent structures of fig. 7 and 6 have the same reference numerals. As shown in fig. 7, a wind farm power transmission system 700 may include:
a plurality of groups of electric control systems 600, a plurality of groups of power frequency step-up transformers 710 and a medium voltage power supply bus 720 described in the above embodiments; wherein,
the low-voltage side of each group of power frequency step-up transformers 710 is connected with one group of electric control systems 600 in a plurality of groups of electric control systems, and each group of power frequency step-up transformers 710 is connected with a medium-voltage power supply bus three-phase 720 through an inductor; the multiple groups of power frequency step-up transformers 710 are configured to convert power frequency alternating current electric energy, which is output by the multiple groups of electronic control systems 600 and meets the requirement of the power grid, into medium voltage alternating current electric energy which meets the requirement of the power grid, and the converted medium voltage alternating current electric energy is connected to the medium voltage power supply bus 720.
As shown in fig. 7, the wind farm power transmission system 700 may further include: step-up transmission transformer 730 configured to convert the medium-voltage ac power into ac power of a preset transmission voltage class and to switch the ac power converted into the preset transmission voltage class into ac transmission bus 740.
With continued reference to fig. 7, in one embodiment, the wind farm power transmission system 700 may further comprise: a reactive compensation device 750, the reactive compensation device 750 may be connected in parallel in the medium voltage network between the medium voltage supply bus 720 and the step-up transmission transformer 730, and the reactive compensation device 700 may be configured to reactive compensate the medium voltage network.
According to the converter, the electric control system and the wind farm power transmission system provided by the embodiment of the invention, the output voltage of the converter is increased in a modular cascade mode of the converter, the output current is greatly reduced, the use of large-batch low-voltage cables is reduced, the loss is reduced, and the efficiency is improved. Meanwhile, the selection that the capacity of the current low-voltage high-capacity converter must be increased in parallel is avoided, the technical problems of current equalization, circulation and the like are avoided, and the reliability of the fan system is improved.
Other details of the current transformer according to the embodiment of the present invention are similar to those of the current transformer according to the embodiment of the present invention described above with reference to fig. 1 to 5, and are not described herein again.
It is to be understood that the invention is not limited to the specific arrangements and instrumentality described above and shown in the drawings. A detailed description of known methods is omitted herein for the sake of brevity. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present invention are not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications and additions or change the order between the steps after comprehending the spirit of the present invention.
As described above, only the specific embodiments of the present invention are provided, and it can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the system, the module and the unit described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again. It should be understood that the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the present invention, and these modifications or substitutions should be covered within the scope of the present invention.
Claims (9)
1. A converter, characterized in that it comprises three cascaded power strings; wherein,
each cascade power string comprises a first output terminal and a second output terminal, star point connection is formed between the first output terminals of each cascade power string, and the second output terminal of each cascade power string forms three-phase output;
and the three-phase input of each cascade power string is connected with a direct-drive wind driven generator of the wind driven generator set.
2. The converter according to claim 1, wherein each of the cascaded power strings comprises a plurality of power cells; wherein,
the three-phase input of each power unit is connected with a group of three-phase windings of the direct-drive wind driven generator in a one-to-one correspondence manner;
the plurality of power units of each cascaded power string are connected in series;
each power unit comprises a first alternating current output terminal and a second alternating current output terminal, the second alternating current terminal of the previous power unit in two adjacent power units in each cascaded power string is connected with the first alternating current terminal of the next power unit, the first alternating current terminal of the first power unit connected in series in each cascaded power string is used as the first output terminal of each cascaded power string, and the second alternating current terminal of the last power unit connected in series in each cascaded power string is used as the second output terminal of each cascaded power string.
3. The converter according to claim 2, wherein each of the power cells comprises a three-phase rectifier module, a bus capacitor, a discharge resistor, a chopper circuit module, and an H-leg inverter module connected in series,
the three-phase rectifier module is configured to be connected with one group of three-phase windings of the direct-drive wind driven generator through three-phase inductors, and is configured to rectify low-frequency alternating current electric energy output by the direct-drive wind driven generator and convert the low-frequency alternating current electric energy into direct current electric energy;
the bus capacitor and the discharge resistor are configured to be connected to two output ends of the three-phase rectifier module;
the chopper circuit module is configured to discharge energy in the direct current bus exceeding a preset direct current bus voltage threshold value through an energy discharge resistor in the chopper circuit module when the direct current bus voltage exceeds the preset direct current bus voltage threshold value;
and the H-type bridge arm inverter module is used for converting the voltage-adjustable direct current electric energy into power frequency alternating current electric energy meeting the power grid requirement.
4. The converter according to claim 3,
the H-type bridge arm inverter module comprises two bridge arms connected in parallel, and each bridge arm comprises two power tube units connected in series;
the two output ends of the H-bridge arm inverter module are the first ac terminal and the second ac terminal.
5. An electric control system, characterized in that the electric control system comprises a direct drive wind generator and a converter according to any of claims 1-4;
the direct-drive wind power generator is configured to comprise a plurality of windings, the number of the windings is 3N, and every three windings form a group of three-phase windings, wherein N is an integer greater than or equal to 3;
the converter is configured to be connected with the direct-drive wind power generator through the plurality of windings.
6. The electrical control system of claim 5, further comprising a master control system and a pitch control system;
the main control system is configured to communicate with the variable pitch control system and the converter, send a variable pitch control instruction to the variable pitch control system, communicate with the converter, and regulate active power and reactive power of the wind driven generator by controlling the converter;
the variable pitch control system is configured for adjusting the pitch angle of the wind turbine blade according to the variable pitch control instruction.
7. A wind farm power transmission system, characterized in that it comprises:
a plurality of groups of the electric control system as claimed in claim 5 or 6, a plurality of groups of power frequency step-up transformers and medium voltage power supply buses; wherein,
the low-voltage side of each group of power frequency step-up transformers is connected with one group of electric control systems in the plurality of groups of electric control systems, and each group of power frequency step-up transformers is connected with the medium-voltage power supply bus in a three-phase mode through inductors;
the multiple groups of power frequency step-up transformers are configured to convert power frequency alternating current electric energy which is output by the multiple groups of electric control systems and meets the requirements of a power grid into medium-voltage alternating current electric energy which meets the requirements of the power grid, and the medium-voltage alternating current electric energy obtained through conversion is connected to the medium-voltage power supply bus.
8. A wind farm power transmission system according to claim 7, further comprising: a step-up transmission transformer and an AC transmission bus;
the step-up power transmission transformer is configured to convert the medium-voltage alternating current electric energy into alternating current electric energy of a preset power transmission voltage level and connect the alternating current electric energy of the preset power transmission voltage level to the alternating current power transmission bus.
9. A wind farm power transmission system according to claim 8, further comprising:
a reactive compensation arrangement connected in parallel in the medium voltage network between the medium voltage supply bus and the step-up transmission transformer and configured to reactive compensate the medium voltage network.
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| CN201721850253.3U CN207801488U (en) | 2017-12-26 | 2017-12-26 | Current transformer, electric-control system and wind power plant transmission system |
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| CN201721850253.3U CN207801488U (en) | 2017-12-26 | 2017-12-26 | Current transformer, electric-control system and wind power plant transmission system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108631355A (en) * | 2017-12-26 | 2018-10-09 | 北京金风科创风电设备有限公司 | Converter, electric control system and wind farm power transmission system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108631355A (en) * | 2017-12-26 | 2018-10-09 | 北京金风科创风电设备有限公司 | Converter, electric control system and wind farm power transmission system |
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