CN207588466U - For the current transformer of wind power plant transmission system and wind power plant transmission system - Google Patents

Abstract

The utility model discloses a kind of for the current transformer of wind power plant transmission system and wind power plant transmission system.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 the three-phase output of current transformer；The rotor windings of the three-phase input of each concatenated power string and the double-fed 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, reduces output current, reduces the loss of machine system, improves wind power plant transmission system stability.

Description

For the current transformer of wind power plant transmission system and wind power plant transmission system

Technical field

The utility model is related to wind-electricity integration technical field more particularly to a kind of current transformers for wind power plant transmission system With wind power plant transmission system.

Background technology

With the aggravation of energy crisis, the development and utilization of new energy has become the hot spot of research, and wind-powered electricity generation is that have at present The regenerative resource of large-scale development potential.Wind power generating set is to convert wind energy into mechanical energy, and mechanical energy drives generator Rotor rotates, the power equipment of final output alternating current.Since concentration is compared in wind-resources distribution in China's, Wind Power Generation employs greatly Scale, high concentration access and the pattern transmitted at a distance.In order to ensure the electricity of the low frequency ac of wind power generating set output Stability is pressed, the low-frequency ac electric energy that wind power generating set exports usually is transformed into direct current energy by rectification, using inverse Become circuit and direct current energy is transformed into electric main, just can guarantee stable use.

In current wind power generating set transmission system, usually realized using current transformer the transmission of above-mentioned electric energy with it is transformed Journey.During practical application, under conditions of Same Efficieney is conveyed, the voltage of current transformer output is relatively low, and output current is larger, is passing Caused by defeated cable loss it is larger, wind power generating set it is less efficient.

In addition, the capacity with wind power generating set is increasing, low pressure current transformer expands capacity often through parallel connection.So And the current transformer parallel system that low pressure current transformer parallel connection obtains easily causes serious circulation problem, circulation problem can cause this low Ideal effect is not achieved in the equal properties of flow of volage current transformer parallel system output current, and the reliability of wind powered generator system is made Into influence.

Utility model content

The utility model embodiment offer is a kind of for the current transformer of wind power plant transmission system and wind power plant transmission system, can To increase the output voltage of current transformer, output current is reduced, reduces the loss of machine system, and a large amount of low-voltage cables can be reduced Use, alleviate the pressure of untying the mooring rope of blower fan system.

According to the one side of the utility model embodiment, a kind of current transformer for wind power plant transmission system is provided, including Three concatenated power strings；Wherein, each concatenated power string includes first lead-out terminal and second output terminal, each concatenated power Asterism connection is formed between the first lead-out terminal of string, second output terminal of each concatenated power string forms the three-phase of current transformer Output；The rotor windings of the three-phase input of each concatenated power string and the double-fed generator of wind power generating set connect.

According to the another aspect of the utility model embodiment, a kind of wind power plant transmission system is provided, including the multiple of parallel connection Double-fed wind power generator group, each double-fed wind power generator group include the current transformer that double-fed generator and above-described embodiment describe； Double-fed generator include stator and rotor, stator include three-phase stator winding, rotor include multiple rotor windings, multiple rotors around The quantity of group is 3N, and every three rotor windings form the rotor three-phase winding of double-fed generator, wherein, N is more than or equal to 3 Integer, the rotor three-phase winding of double-fed generator is connected to current transformer.

In the utility model embodiment for the current transformer of wind power plant transmission system and wind power plant transmission system, can By by modularization it is cascade in a manner of, by the concatenated power string in current transformer, increase the output voltage of current transformer, reduce output Electric current reduces the use of high-volume low-voltage cable, reduces the loss of machine system.Meanwhile in the utility model embodiment Current transformer can must carry out the selection of hoist capacity in parallel to avoid current low-voltage high-capacity current transformer, so as to avoid electricity in parallel The technical problems such as the stream of cable and circulation improve the reliability of blower fan system.

Description of the drawings

It, below will be in the utility model embodiment in order to illustrate more clearly of the technical solution of the utility model embodiment Required attached drawing is briefly described, for those of ordinary skill in the art, what is do not made the creative labor Under the premise of, it can also be obtained according to these attached drawings other attached drawings.

Fig. 1 is to show a kind of topological structure schematic diagram of wind power plant transmission system of the prior art；

Fig. 2 is the structure for the current transformer for wind power plant transmission system for showing to be provided according to one embodiment of the utility model Schematic diagram；

Fig. 3 is the detailed construction schematic diagram for showing the current transformer according to the utility model some exemplary embodiments；

Fig. 4 is the concrete structure schematic diagram for showing the power cell according to one embodiment of the utility model；

Fig. 5 is the structure diagram for the wind power plant transmission system for showing to be provided according to one embodiment of the utility model.

In the accompanying drawings, identical component uses identical reference numeral, and description of symbols is as follows：

10- double-feds exchange wind power generating set；20- bus rods；11- wind-driven generators；12- double-fed generators；13- is low Volage current transformer；14- step-up transformers；

300- current transformers；310- the first concatenated power strings；320- the second concatenated power strings；330- third concatenated power strings；

3111- three-phase converter modules；3112- bus capacitors and discharge resistance；3113- chopper circuit modules；3114-H Formula leg inverter module；

510- double-fed wind power generator groups；520- medium-pressure electricity supply busbares；

511- double-fed generators；512- step-up transformers.

Specific embodiment

The feature and exemplary embodiment of the various aspects of the utility model is described more fully below, in order to make this practicality new The object, technical solution and advantage of type are more clearly understood, with reference to the accompanying drawings and embodiments, to the utility model into advance one Step detailed description.It should be understood that specific embodiment described herein is only configured to explain the utility model, it is not configured as Limit the utility model.To those skilled in the art, the utility model can be in these details not be needed to Implement in the case of some details.Below the description of embodiment is used for the purpose of carrying by showing the example of the utility model For being better understood to the utility model.

It should be noted that herein, relational terms such as first and second and the like are used merely to a reality Body or operation are distinguished with another entity or operation, are deposited without necessarily requiring or implying between these entities or operation In any this practical relationship or sequence.Moreover, term " comprising ", "comprising" or its any other variant are intended to Non-exclusive inclusion, so that process, method, article or equipment including a series of elements not only will including those Element, but also including other elements that are not explicitly listed or further include as this process, method, article or equipment Intrinsic element.In the absence of more restrictions, the element limited by sentence " including ... ", it is not excluded that including Also there are other identical elements in the process of the element, method, article or equipment.

Fig. 1 is to show a kind of topological structure schematic diagram of wind power plant transmission system of the prior art.It is as shown in Figure 1, traditional Wind power generating set 10 is exchanged by multigroup double-fed based on the transmission system of wind power plant and middle pressure 35KV bus rods 20 are formed, every group Double-fed exchange wind power generating set 10 includes wind-driven generator 11, double-fed generator 12, low pressure current transformer 13 and step-up transformer 14.Wherein, double-fed generator includes threephase stator winding 1201 and three-phase rotor windings 1202；The three-phase of double-fed generator 12 is determined Sub- winding 1201 is connect with the low-pressure side of step-up transformer 14；The rotor windings of double feedback electric engine are sent out with the wind-force of low pressure current transformer 13 The threephase cable of motor side is connected, and the threephase cable of the grid side of low pressure current transformer 13 can access its in power grid or power grid His electrical equipment such as step-up transformer 14.

As an example, step-up transformer 14 can will be exchanged in 70% 690V of the stator side of double-fed generator 12 The power of the power of voltage and 30% 690V alternating voltages of the rotor-side of double-fed generator 120, is converted into 35KV wind power plants Middle pressure busbar.

But the current transformer output voltage is relatively low and electric current is larger, under conditions of Same Efficieney is conveyed, transmission cable Loss is very big, and the efficiency of wind turbine power generation unit cannot improve.The use of the low-voltage cable of a large amount of noble metal is needed, is caused whole The loss of machine system is larger.Increasing with the capacity of wind power generating set, low pressure current transformer needs to hold by parallel expand Amount.However, the current transformer parallel system that low pressure current transformer parallel connection obtains easily causes serious circulation problem, circulation problem can cause Ideal effect is not achieved in the equal properties of flow of the low pressure current transformer parallel system output current, and the reliability of blower fan system is caused It influences.

For these reasons, the utility model embodiment provides a kind of current transformer for wind power plant transmission system, changes The internal electrical structure of current transformer is become, the output voltage of current transformer can be increased, reduced output current, reduce machine system Loss, and the reliability of blower fan system can be improved.

In order to be better understood from the utility model, below in conjunction with attached drawing, it is described in detail according to the utility model embodiment Current transformer and wind power plant transmission system, it should be noted that these embodiments are not for limiting the utility model scope of disclosure.

Fig. 2 shows the structure diagrams of wind electric converter provided according to one embodiment of the utility model.Such as Fig. 2 institutes Showing, current transformer 300 can specifically include three concatenated power strings, wherein, each concatenated power string can include the first output terminal Son and second output terminal are sub, and asterism connection, each concatenated power string are formed between the first lead-out terminal of each concatenated power string Second output terminal formed current transformer 300 three-phase output；The three-phase input of each concatenated power string and wind power generating set Double-fed generator a group rotor winding connection.

In this embodiment, which is configured as the alternating current that can export doubly-fed generation machine rotor It is converted into the industrial frequency AC electric energy for meeting grid requirements.

As an example, as shown in Fig. 2, current transformer 300, which can include the first concatenated power string 310, second, cascades work( Rate string 320 and third concatenated power string 330.

With continued reference to Fig. 2, the first lead-out terminal of the first concatenated power string 310, the second concatenated power string 320 it is first defeated Formation asterism connects between going out the first lead-out terminal of terminal and third concatenated power string 330；First concatenated power string 310 Second output terminal, the second concatenated power string 320 second output terminal and third concatenated power string 330 it is second defeated Go out the three-phase output end that terminal forms current transformer.

The current transformer of the utility model embodiment respectively by the first concatenated power string 310, the second concatenated power string 320, with And third concatenated power string 330 forms three-phase system together.Changing single current transformer in conventional current transformer can directly constitute The design of converter system by the cascade mode of modularization, increases the output voltage of current transformer, greatly reduces output current, The use of high-volume low-voltage cable is reduced, loss is reduced, improves efficiency；Meanwhile it avoids current low-voltage high-capacity and becomes Stream device must carry out the selection of hoist capacity in parallel, avoid the technical problems such as stream and circulation, and improve blower fan system can By property.

Fig. 3 shows the detailed construction schematic diagram of the current transformer according to the utility model some exemplary embodiments, Fig. 3 with Structure identical or equivalent Fig. 2 uses identical label.As shown in figure 3, current transformer 300 includes the first concatenated power string 310, the Two concatenated power strings 320 and third concatenated power string 330, wherein, the first concatenated power string 310 includes multiple power cells Such as power cell _ a1, power cell _ a2 ..., power cell _ aN；Second concatenated power string 320 includes multiple power lists Member such as power cell _ b1, power cell _ b2 ..., power cell _ bN；Third concatenated power string 330 includes multiple power Unit such as power cell _ c1, power cell _ c2 ..., power cell _ cN.But the utility model is retouched more than being not limited to Specific module stating and being shown in FIG. 3, in some embodiments, the concatenated power string in current transformer 300 can wrap Containing more flexible configuration, illustrated with reference to specific embodiment.

In one embodiment, each concatenated power string of current transformer 300 includes multiple power cells, wherein, Duo Gegong The three-phase input of each power cell in rate unit is connect correspondingly with a group rotor three-phase windings of double-fed generator； It is connected in series between multiple power cells included by each concatenated power string；Each power cell includes the first ac output end Son and the second AC output terminal the second of a upper power cell are handed in two neighboring power cell in each concatenated power string Stream terminal is connect with the first ac terminal of next power cell, first power of the serial connection of each concatenated power string First lead-out terminal of first ac terminal of unit as each concatenated power string, the serial connection of each concatenated power string Second output terminal of second ac terminal of the last one power cell as each concatenated power string.

That is, for the multiple power cells being connected in series in each concatenated power string, it can will remove and be connected in series with First power cell and the last one power cell for being connected in series with other than each power cell the first ac terminal Connect with the second ac terminal of a upper power cell that it is connected in series, and by its second ac terminal with and its serially The first ac terminal connection of next power cell of connection.

As an example, when each concatenated power string of current transformer 300 includes three power cells, i.e. concatenated power The power cell that the first concatenated power string 310 in string includes be power cell _ a1, power cell _ a2 and power cell _ a3, The power cell that second concatenated power string 320 includes is power cell _ b1, power cell _ b2 and power cell _ b3, Yi Ji The power cell that three concatenated power strings 330 include is power cell _ c1, power cell _ c2 and power cell _ c3.

In this example, the three-phase input of power cell _ a1, the three-phase input of power cell _ a2, power cell _ a3 Three-phase input, the three-phase input of power cell _ b1, the three-phase input of power cell _ b2, the three-phase input of power cell _ b3, work( The three-phase input of rate unit _ c1, the three-phase input of power cell _ c2 and the three-phase input of power cell _ c3 are respectively at double-fed The group rotor three-phase windings connection of generator；

In the first concatenated power string 310, serially connect between power cell _ a1, power cell _ a2 and power cell _ a3 It connects, in the second concatenated power string 320, is connected in series between power cell _ b1, power cell _ b2 and power cell _ b3, In third concatenated power string 330, it is connected in series between power cell _ c1, power cell _ c2 and power cell _ c3.

First lead-out terminal of the first AC output terminal of power cell _ a1 as the first concatenated power string 310, power The first AC output terminal of unit _ b1 is as the first lead-out terminal of the second concatenated power string 320 and power cell _ c1 First lead-out terminal of first AC output terminal as third concatenated power string 330, and the first of each concatenated power string The first AC output terminal of leading-out terminal, that is, power cell _ a1, the first AC output terminal, the Yi Jigong of power cell _ b1 Asterism connection is formed between the first AC output terminal of rate unit _ c1；

Second output terminal of the second AC output terminal of power cell _ a3 as the first concatenated power string 310, power Second output terminal and power cell _ c3 of the second AC output terminal of unit _ b3 as the second concatenated power string 320 Second output terminal of second AC output terminal as third concatenated power string 330, and the second of each concatenated power string The second AC output terminal of leading-out terminal, that is, power cell _ a3, the second AC output terminal, the Yi Jigong of power cell _ b3 The second AC output terminal of rate unit _ c3 forms the three-phase output of current transformer 300.

In this example, in the first concatenated power string 310, the second AC output terminal and the power list of power cell _ a1 The first AC output terminal connection of member _ a2, the second AC output terminal of power cell _ a2 and the first of power cell _ a3 AC output terminal connects；

In second concatenated power string 320, the second AC output terminal of power cell _ b1 and the first of power cell _ b2 AC output terminal connects, the second AC output terminal of power cell _ b2 and the first AC output terminal of power cell _ b3 Connection；

In third concatenated power string 330, the second AC output terminal of power cell _ c1 and the first of power cell _ c2 AC output terminal connects, the second AC output terminal of power cell _ c2 and the first AC output terminal of power cell _ c3 Connection.

In some embodiments, each concatenated power string in current transformer 300 can include greater number of power cell, The quantity of power cell can be more than or equal to 3 in i.e. each concatenated power string.

As an example, current transformer 300 includes three concatenated power strings, and each concatenated power string includes N number of power list Member, each power cell have one group of three-phase input end, and double-fed generator includes stator and rotor, wherein, the double-fed generator The rotor windings quantity set on rotor is 3N, wherein, every 3 windings form one group of three-phase output of double-fed generator, double The three-phase input end that the N groups three-phase of feedback generator is exported respectively with N number of power cell of each concatenated power string is correspondingly connected with.

As shown in figure 3, the double-fed generator in the utility model embodiment includes stator and rotor, double-fed generator is determined Son and rotor can export AC energy to power grid, and double-fed generator stator side can by the AC energy that stator winding exports To be directly incorporated into power grid by grid-connected switch, and the AC energy that double-fed generator rotor-side is exported by rotor windings can lead to Cross current transformer and it is grid-connected switch access power grid, and the rotor of the double-fed generator include 3N winding, N for 3 integral multiple, every three A rotor windings form one group of ABC three-phase alternating current system.

In the utility model embodiment, volage current transformer in the more level of converter moduleization, by limiting double-fed generator The winding quantity of middle rotor can constrain the output voltage of current transformer.Therefore, the current transformer of the utility model embodiment can lead to It crosses and the power cell in each concatenated power string is subjected to the cascade mode of modularization, superposition exports higher voltage, drops significantly Low output current, and have the advantages that output goes that harmonic wave is few, the degree of modularity is high；Meanwhile different from current low-voltage high-capacity Current transformer carries out parallel connection to promote the selection of Converter Capacity, so as to avoid the technical problems such as stream and circulation, improves wind The reliability of machine system.

Fig. 4 shows the concrete structure schematic diagram of the power cell according to one embodiment of the utility model.As shown in figure 4, One of power cell of one of concatenated power string as current transformer 300, the power cell can include connecting successively Three-phase converter module 3111, bus capacitor and discharge resistance 3112, chopper circuit module 3113 and the H formula bridge arms connect is inverse Become device module 3114.

As shown in figure 4, three-phase converter module 3111, is configured as wherein one via threephase cable and double-fed generator Group three-phase windings connection, and be configured as carrying out rectification to the low-frequency ac electric energy that double-fed generator exports, by low-frequency ac Electric energy is converted to direct current energy.

As an example, three-phase converter module for example can be Three-Phase PWM Rectifier.Specifically, three-phase rectifier Module 3111 can be three bridges, six arm configuration, and including three bridge arms in parallel, and each bridge arm includes the power tube of two series connection Unit, the power pipe unit for example can be insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT).

Bus capacitor and discharge resistance 3112 are configured as being connected to two output terminals of three-phase converter module, in Fig. 5 In, bus capacitor can be configured as and the direct current energy being converted to is filtered and stored the direct current energy, electric discharge electricity Resistance, which can be configured as, discharges to the electricity stored in bus capacitor.

Chopper circuit module 3113 is configured as when DC bus-bar voltage is more than preset DC bus-bar voltage threshold value, By unloading energy resistance in chopper circuit module 3113, discharge is more than the energy in the dc bus of DC bus-bar voltage threshold value.

As shown in figure 4, chopper circuit module 3113 can include being connected in series in switching tube Q1 between dc bus and Unloading can resistance R.As an example, switching tube Q1 can be with igbt transistor.In this example, chopper circuit module 3113 is gone back It can include the switching tube Q2 in parallel with unloading energy resistance R, switching tube Q2 can be the IGBT comprising diode, with diode Any one in metal-oxide-semiconductor or diode, in chopper circuit module 3113, switching tube Q2 can be used as diode.

In this embodiment, DC bus-bar voltage is caused to pump when the operating mode such as low-voltage crossing occurs for the power grid of wind power plant Rise, DC bus-bar voltage be more than predetermined DC busbar voltage threshold value when, can by control in the chopper circuit module 3113 with The switching tube Q1 conductings of energy resistance series connection are unloaded, the energy for pumping liter in dc bus is made to be carried out through switching tube Q1 with energy resistance R is unloaded Discharge, to prevent dc bus over-pressed.

H formula leg inverters module 3114, for the adjustable direct current energy of voltage to be converted into the work for meeting grid requirements Frequency AC energy.

As shown in figure 4, in one embodiment, H formula leg inverters module (H bridges can be referred to as in described below) packet Two bridge arms in parallel are included, each bridge arm includes the power pipe unit of two series connection；Two outputs of H formula leg inverter modules It holds as the first ac terminal and second ac terminal.

In the utility model embodiment, the three-phase input of each power cell of the concatenated power string in current transformer with it is double The group rotor three-phase windings connection of generator is presented, the output of the power cell is exchanged for the two-way of H formula leg inverter modules Leading-out terminal, wherein, the second ac terminal of a upper power cell of the first ac terminal of the H bridges with being connected in series is connected It connects, the first ac terminal of next power cell of the second ac terminal of the H bridges with being connected in series is connected.

Fig. 5 shows the structure diagram of the wind power plant transmission system provided according to one embodiment of the utility model.Such as Fig. 5 Shown, in one embodiment, wind power plant transmission system 500 can include：

Multiple double-fed wind power generator groups 510 in parallel, each double-fed wind power generator group include double-fed generator 511, Each double-fed wind power generator group 510 includes combining the unsteady flow that Fig. 2 to Fig. 4 is described in double-fed generator 511 and above-described embodiment Device 300.

The double-fed generator 511 include stator and rotor, stator include three-phase stator winding, rotor include multiple rotors around Group, the quantity of multiple rotor windings is 3N, and every three rotor windings form the rotor three-phase winding of double-fed generator, In, N is the integer more than or equal to 3, and the rotor three-phase winding of double-fed generator 511 is connected to current transformer 300.

In this embodiment, with the output power of straight drive blower completely by stator by the grid-connected difference of total power frequency converter, The stator and rotor of double-fed generator 511 can be fed to power grid, and the AC energy of double-fed generator stator side can directly simultaneously Enter power grid, and the AC energy of double-fed generator rotor-side can be connected to the grid by current transformer 300, the frequency of rotor windings power supply Rate, voltage, amplitude and phase can be automatically adjusted by the service requirement of wind turbine power generation unit by current transformer, and wind power generating set can To realize constant frequency generation, satisfaction electric loading and grid-connected requirement under different rotating speeds.

The double-fed generator of the utility model embodiment is middle pressure double-fed generator, by the stator for promoting double-fed generator Port voltage grade can reduce the grid-connected cost of rotor-side, such as can promote the output voltage of double-fed generator stator side To 10kV.At the same time, using the concatenated power string in current transformer, by the cascade mode of modularization, the defeated of current transformer is promoted Go out voltage, reduce output current, reduce the loss of machine system, and avoid current low-voltage high-capacity current transformer that from must carrying out parallel connection The selection of hoist capacity improves the reliability of blower fan system.

With continued reference to Fig. 5, in one embodiment, each double-fed wind power generator group 500 can also include boosting transformation Device 512, wind power plant transmission system can also include medium-pressure electricity supply busbar 520；The low-pressure side and doubly-fed generation of step-up transformer 512 The three-phase stator winding connection of machine 511, and the low-pressure side of step-up transformer 512 and the three-phase output of current transformer 300 connect；It rises Pressure transformer 512 is configured for exchanging the AC energy of the stator output of double-fed generator 511 with what current transformer 300 exported Electric energy is converted into the middle pressure AC energy for meeting grid requirements, and the middle pressure AC energy being converted to access medium-pressure electricity supply is female Line 520.

As shown in figure 5, in the utility model embodiment, low-pressure side and the double-fed generator 511 of step-up transformer 512 Three-phase stator winding connects, and the low-pressure side of step-up transformer 512 and the three-phase output of current transformer 300 connect；Boosting transformation The high-pressure side of device 512 is connected with medium-pressure electricity supply busbar 520 3.

According to the current transformer of the utility model embodiment and wind power plant transmission system, pass through the cascade side of converter moduleization Formula increases the output voltage of current transformer, greatly reduces output current, reduces the use of high-volume low-voltage cable, reduces Loss, improves efficiency.Meanwhile avoid current low-voltage high-capacity current transformer and must carry out the selection of hoist capacity in parallel, it keeps away Exempt from the technical problems such as stream and circulation, improve the reliability of blower fan system.

According to the other details of the current transformer of the utility model embodiment with above in association with Fig. 1 to Fig. 5 describe according to The current transformer of utility model embodiment is similar, and details are not described herein.

It should be clear that the utility model is not limited to specific configuration described above and shown in figure and place Reason.For brevity, it is omitted here the detailed description to known method.In the above-described embodiments, if having been described and illustrated Dry specific step is as example.But the procedure of the utility model is not limited to described and illustrated specific steps, Those skilled in the art can be variously modified after the spirit of the utility model is understood, modification and addition or change Sequence between step.

The above, only specific embodiment of the present utility model, those skilled in the art can be clearly It solves, for convenience of description and succinctly, the specific work process of the system of foregoing description, module and unit, before can referring to The corresponding process in embodiment of the method is stated, details are not described herein.It should be understood that the scope of protection of the utility model is not limited to This, in the technical scope that any one skilled in the art discloses in the utility model, can readily occur in various etc. The modifications or substitutions of effect, these modifications or substitutions should be covered within the scope of the utility model.

Claims (9)

1. a kind of current transformer for wind power plant transmission system, which is characterized in that the current transformer includes three concatenated power strings； Wherein,

Each concatenated power string includes first lead-out terminal and second output terminal, the first output of each concatenated power string Asterism connection is formed between terminal, the three-phase that second output terminal of each concatenated power string forms the current transformer is defeated Go out；

The rotor windings of the three-phase input of each concatenated power string and the double-fed generator of wind power generating set connect.

2. current transformer according to claim 1, which is characterized in that each concatenated power string includes multiple power lists Member；Wherein,

The three-phase input of each power cell is connect correspondingly with a group rotor three-phase windings of the double-fed generator；

It is connected in series between the multiple power cell of each concatenated power string；

Each power cell includes the first AC output terminal and the second AC output terminal, phase in each concatenated power string The second ac terminal of a upper power cell connects with the first ac terminal of next power cell in adjacent two power cells It connects, the first ac terminal of first power cell of the serial connection of each concatenated power string is as each cascade The first lead-out terminal of power string, the second exchange of the last one power cell of the serial connection of each concatenated power string Second output terminal of the terminal as each concatenated power string.

3. current transformer according to claim 1, which is characterized in that

The three-phase output of the current transformer is connected to the step-up transformer of the wind power generating set.

4. current transformer according to claim 2, which is characterized in that each power cell includes sequentially connected three-phase Rectifier module, bus capacitor, discharge resistance, chopper circuit module and H formula leg inverter modules, wherein,

The three-phase converter module is configured as the one of which three-phase windings via threephase cable and the double-fed generator Connection, and be configured as carrying out rectification to the low-frequency ac electric energy that the double-fed generator exports, by the low frequency ac Direct current energy can be converted to；

The bus capacitor and the discharge resistance are configured as being connected to two output terminals of the three-phase converter module；

The chopper circuit module is configured as when the DC bus-bar voltage is more than preset DC bus-bar voltage threshold value, Energy resistance is unloaded by the way that the chopper circuit mould is in the block, discharge is more than the energy in the dc bus of the DC bus-bar voltage threshold value Amount；

The H formulas leg inverter module, for the adjustable direct current energy of the voltage to be converted into the work for meeting grid requirements Frequency AC energy.

5. current transformer according to claim 4, which is characterized in that

The H formulas leg inverter module includes two bridge arms in parallel, and each bridge arm includes the power pipe unit of two series connection；

Two output terminals of the H formulas leg inverter module are first ac terminal and second ac terminal.

6. a kind of wind power plant transmission system, which is characterized in that the wind power plant transmission system includes multiple double-fed wind-force in parallel Generating set, each double-fed wind power generator group include double-fed generator and the unsteady flow as described in any one of claim 1-5 Device；

The double-fed generator includes stator and rotor, and the stator includes three-phase stator winding, and the rotor includes multiple turns Sub- winding, the quantity of the multiple rotor windings is 3N, and every three rotor windings form the rotor of the double-fed generator Three-phase windings, wherein, N is the integer more than or equal to 3, and the rotor three-phase winding of the double-fed generator is connected to the unsteady flow Device.

7. wind power plant transmission system according to claim 6, which is characterized in that each double-fed wind power generator group is also Including step-up transformer, the wind power plant transmission system further includes medium-pressure electricity supply busbar；

The low-pressure side of the step-up transformer is connect with the three-phase stator winding of the double-fed generator, and the boosting transformation The low-pressure side of device and the three-phase output of the current transformer connect；

The step-up transformer is configured for the AC energy of the stator output of the double-fed generator and the current transformer The AC energy of output is converted into the middle pressure AC energy for meeting grid requirements, and by the middle pressure AC energy being converted to Access medium pressure power supply buses.

8. wind power plant transmission system according to claim 7, which is characterized in that

The low-pressure side of the step-up transformer is connect with the three-phase stator winding of the double-fed generator, and the boosting transformation The low-pressure side of device and the three-phase output of the current transformer connect；

The high-pressure side of the step-up transformer is connected with medium pressure power supply buses three.

9. wind power plant transmission system according to claim 6, which is characterized in that

The double-fed generator is middle pressure double-fed generator.