WO2019128145A1 - 用于风电场输电系统的变流器、电控系统和输电系统 - Google Patents

用于风电场输电系统的变流器、电控系统和输电系统 Download PDF

Info

Publication number
WO2019128145A1
WO2019128145A1 PCT/CN2018/092000 CN2018092000W WO2019128145A1 WO 2019128145 A1 WO2019128145 A1 WO 2019128145A1 CN 2018092000 W CN2018092000 W CN 2018092000W WO 2019128145 A1 WO2019128145 A1 WO 2019128145A1
Authority
WO
WIPO (PCT)
Prior art keywords
power
converter
generator
phase
cascaded
Prior art date
Application number
PCT/CN2018/092000
Other languages
English (en)
French (fr)
Inventor
刘世军
李战龙
杨有涛
蒋中川
杨志千
Original Assignee
北京金风科创风电设备有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CN201711437685.6A external-priority patent/CN108631356B/zh
Priority claimed from CN201711432843.9A external-priority patent/CN108631355A/zh
Application filed by 北京金风科创风电设备有限公司 filed Critical 北京金风科创风电设备有限公司
Publication of WO2019128145A1 publication Critical patent/WO2019128145A1/zh

Links

Images

Classifications

    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

Definitions

  • the invention relates to the field of wind power grid-connecting technology, in particular to a converter, an electric control system and a power transmission system for a wind farm power transmission system.
  • Wind power is a renewable energy source with large-scale development potential.
  • Wind turbines are electrical equipment that converts wind energy into mechanical energy, mechanical energy that drives the rotor of the generator to rotate, and ultimately outputs alternating current. Due to the concentrated distribution of wind resources in China, wind power development adopts a large-scale, highly centralized access and long-distance transmission mode.
  • the low-frequency alternating current output from the wind turbine is usually converted into DC power by rectification, and then the DC power is converted into AC mains through the inverter circuit to ensure stable use.
  • the current transmission and transformation process of the above-mentioned electric energy is usually realized by using a current transformer.
  • the generator of the wind turbine is located in the nacelle at the top of the tower, and the converter is generally located in the tower of the tower of the wind turbine.
  • a large number of low-voltage cables need to be transmitted to the converter at the bottom of the tower through the high tower. This results in a large number of cables used in the tower, which puts a lot of pressure on the unwinding of the fan system.
  • the embodiment of the invention provides a converter, an electric control system and a wind farm transmission system for a wind farm transmission system, which can increase the output voltage of the converter, reduce the output current, reduce the loss of the whole system, and can Reduce the use of a large number of low-voltage cables, relieve the unwinding pressure of the fan system, and improve the stability of the wind farm transmission system.
  • a converter for a wind farm power transmission system comprising three cascaded power strings; wherein each cascaded power string includes a first output terminal and a second output terminal, A star point connection is formed between the first output terminals of each cascaded power string, and the second output terminal of each cascaded power string forms a three-phase output of the converter; three-phase input and wind of each cascaded power string
  • the generator of the generator set is connected, and the generator includes a direct drive wind generator or a doubly fed generator.
  • an electronic control system for a wind farm power transmission system including a generator and a current transformer in the above embodiment; the generator is a direct drive wind power generator; direct drive wind power generation
  • the machine is configured to include a plurality of windings, the number of the plurality of windings is 3N, and each of the three windings forms a set of three-phase windings, wherein N is an integer greater than or equal to 3; the converter is configured to pass through the plurality of windings Connected to a direct drive wind turbine.
  • a wind farm power transmission system including the electronic control system, the multiple sets of power frequency step-up transformers, and the medium voltage power supply bus bar described in the above embodiments; wherein each group of power frequency step-up transformers The low voltage side is connected to a group of electronic control systems in a plurality of electronic control systems, each set of power frequency step-up transformers is connected to the medium voltage power supply bus through three phases through inductors; multiple sets of power frequency step-up transformers are configured for multiple groups The power frequency AC power output of the electronic control system that meets the grid requirements is converted into medium voltage AC power that meets the requirements of the power grid, and the converted medium voltage AC power is connected to the medium voltage power supply bus.
  • a wind farm power transmission system includes a plurality of doubly-fed wind power generators connected in parallel, and each of the doubly-fed wind power generator sets includes a doubly-fed generator and the foregoing embodiment is described.
  • the converter includes a stator and a rotor, the stator includes a stator three-phase winding, the rotor includes a plurality of rotor windings, the number of the plurality of rotor windings is 3N, and each three rotor windings form a rotor of the doubly-fed generator A three-phase winding, wherein N is an integer greater than or equal to 3, and a rotor three-phase winding of the doubly-fed generator is connected to the converter.
  • the output voltage of the converter can be increased by the cascaded power string in the converter by means of modular cascade.
  • Output current reduces the use of high-volume low-voltage cables and reduces the loss of the entire system.
  • the converter in the embodiment of the invention can avoid the selection of the parallel lifting capacity of the current low-voltage large-capacity converter, thereby avoiding technical problems such as current sharing and circulation of the parallel cable, and improving the reliability of the fan system.
  • FIG. 1 is a schematic view showing the structure and position of a current converter for a wind turbine
  • FIG. 2 is a schematic diagram showing the topology of an electric control system of a current wind turbine-based converter
  • FIG. 3 is a schematic structural diagram showing a converter according to an embodiment of the invention.
  • FIG. 4 is a detailed structural diagram showing a converter 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 invention.
  • FIG. 6 is a schematic structural diagram of an electronic control system according to an embodiment of the invention.
  • FIG. 7 is a schematic structural view showing a wind farm power transmission system according to an embodiment of the present invention.
  • FIG. 8 is a schematic diagram showing a topology of a wind farm power transmission system in the prior art
  • FIG. 9 is a schematic structural view showing a converter according to another embodiment of the present invention.
  • FIG. 10 is a detailed structural diagram showing a converter according to other exemplary embodiments of the present invention.
  • FIG. 11 is a schematic diagram showing a specific structure of a power unit according to another embodiment of the present invention.
  • FIG. 12 is a schematic structural view showing a wind farm power transmission system according to another embodiment of the present invention.
  • 10-wind generator set 20-electric control system; 21-direct drive motor; 2201-first converter; 2202-second converter;
  • 300-converter 310-first cascaded power string; 320-second cascade power string; 330-third cascade power string;
  • 3111-three-phase rectifier module 3112-busbar capacitor and discharge resistor; 3113-chopper circuit module; 3114-H bridge arm inverter module;
  • 600-electric control system 610-pitch control system; 620-master control system;
  • 700-wind farm transmission system 710-multiple power frequency step-up transformer; 720-medium voltage power supply bus; 730-boost power transmission transformer; 740-AC power supply AC transmission bus; 750-reactive power compensation device;
  • Fig. 1 is a schematic view showing the structure and position of a current converter for a wind turbine.
  • the generator of the wind turbine is usually located in the nacelle of the tower top
  • the converter is generally located in the tower of the tower of the wind turbine, and a large number of low-voltage cables are transmitted to the bottom of the tower through the high tower.
  • the converter converts the low-frequency alternating current outputted by the wind turbine into a direct current electric energy by rectification, and then converts the direct current electric energy into alternating current electric energy into the electric grid via the inverter circuit.
  • the position of the converter is such that the number of cables used in the tower is large and the unwinding pressure of the fan system is large.
  • the generator of the wind turbine may comprise a direct drive wind generator or a doubly fed generator.
  • a converter, an electric control system and a wind farm transmission system according to an embodiment of the present invention will be described in detail below with reference to FIGS. 2 to 7 in detail when the generator of the wind power generator is a direct drive wind power generator. . It should be noted that these examples are not intended to limit the scope of the disclosure.
  • the electronic control system 20 includes a direct drive motor 21, a first converter 2201, and a second converter 2202.
  • the direct drive motor 21 is coupled to the wind turbine 10.
  • the conventional converter can be directly used as the current conversion system by the first converter 2201 or the converter 2202.
  • the three-phase of the wind turbine side of the first converter 2201 is connected to the three-phase winding of the stator of the direct drive motor through the inductor; the three-phase of the grid side of the first converter 2201 is connected to the grid through the inductor.
  • Other electrical equipment such as step-up transformers (not shown).
  • the converter has a low output voltage and a large current, which requires the use of a large amount of low-voltage cables of precious metals, resulting in a large loss of the whole system.
  • the converter may be composed of a first converter 2201 and a second converter 2202 to form a converter parallel system, on the side of the wind turbine of the converter parallel system, each converter The three-phase is connected to the three-phase winding of the stator of the direct drive motor through an inductor; on the grid side of the parallel system of the converter, the AC output of each converter is connected in parallel to connect the low voltage side of other electrical equipment such as the step-up transformer in the power grid.
  • FIG. 3 is a schematic structural diagram of a converter according to an embodiment of the invention. As shown in FIG.
  • the converter 300 may specifically include three cascaded power strings, wherein each cascaded power string may include a first output terminal and a second output terminal, and the first output of each cascaded power string A star point connection is formed between the terminals, and the second output terminal of each cascaded power string forms a three-phase output of the converter 300; the three-phase input of each cascaded power string is connected to the direct drive wind turbine of the wind turbine .
  • the three cascaded power strings are configured to convert the AC power output by the direct drive wind turbine into power frequency AC power that meets the grid requirements.
  • the converter 300 can include a first cascaded power string 310, a second cascaded power string 320, and a third cascaded power string 330.
  • 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 composed of a first cascade power string 310, a second cascade power string 320, and a third cascade power string 330, respectively, to form a three-phase system.
  • the single converter in the traditional converter can directly change the design of the converter system.
  • modular cascading the output voltage of the converter is increased, the output current is greatly reduced, and the low-voltage cable is reduced.
  • the use reduces the loss and improves the efficiency.
  • it avoids the choice of the parallel low-lift capacity of the low-voltage large-capacity converter, avoids the technical problems such as current sharing and circulation, and improves the reliability of the fan system.
  • Fig. 4 shows a detailed structural diagram of a converter according to some exemplary embodiments of the present invention, and the same or equivalent structures of Fig. 4 and Fig. 3 use the same reference numerals.
  • 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 units For example, power unit_a1, power unit_a2, ..., power unit_aN; second cascaded power string 320 includes a plurality of power units such as power unit_b1, power unit_b2, ..., power unit_bN;
  • the third concatenated power string 330 includes a plurality of power units such as a power unit_c1, a power unit_c2, ..., a power unit_cN.
  • the cascaded power strings in the converter 300 may
  • each cascaded power string of the converter 300 includes a plurality of power units, wherein the three-phase inputs of each of the plurality of power units are in a one-to-one correspondence with the direct drive wind turbine a set of three-phase winding connections; a serial connection between a plurality of power units of each cascaded power string; each power unit comprising a first alternating current output terminal and a second alternating current output terminal, each cascaded power string phase a second AC terminal of the previous one of the two power units is connected to the first AC terminal of the next power unit, and the first AC terminal of the first power unit of each serially connected power string is used as A first output terminal of the cascaded power string, and a second AC terminal of the last power unit of the serial connection of each cascaded power string serves as a second output terminal of each cascaded power string.
  • the first exchange of each power unit other than the first power unit connected in series and the last power unit connected in series may be The terminal is connected to a second AC terminal of a previous power unit to which it is serially connected, and its second AC terminal is connected to a first AC terminal of a next power unit to which it is serially connected.
  • each cascaded power string of the converter 300 includes three power units, that is, the power unit included in the first cascaded power string 310 in the cascaded power string is a power unit_a1, a power unit_ A2 and power unit_a3, the second cascaded power string 320 includes power units _b1, power unit_b2 and power unit_b3, and the power unit included in the third cascode power string 330 is a power unit _ C1, power unit_c2 and power unit_c3.
  • the three-phase input of the power unit _b3, the three-phase input of the power unit _c1, the three-phase input of the power unit _c2, and the three-phase input of the power unit _c3 are respectively connected to a set of three-phase windings of the direct drive wind power generator ;
  • the power unit_a1, the power unit_a2 and the power unit_a3 are connected in series
  • the power unit_b1, the power unit_b2 and The power unit_b3 is connected in series
  • the power unit_c1, the power unit_c2 and the power unit_c3 are connected in series.
  • the first AC output terminal of the power unit_a1 serves as a first output terminal of the first cascaded power string 310
  • the first AC output terminal of the power unit_b1 serves as a first output terminal of the second cascaded power string 320
  • power The first AC output terminal of the unit_c1 serves as a first output terminal of the third cascaded power string 330, and the first output terminal of each cascaded power string, that is, the first AC output terminal of the power unit_a1, the power unit_ a star point connection is formed between the first AC output terminal of b1 and the first AC output terminal of the power unit_c1;
  • the second AC output terminal of the power unit_a3 serves as a second output terminal of the first cascaded power string 310
  • the second AC output terminal of the power unit_b3 serves as a second output terminal of the second cascaded power string 320
  • power The second AC output terminal of the unit_c3 serves as a second output terminal of the third cascaded power string 330, and the second output terminal of each cascaded power string, that is, the second AC output terminal of the power unit_a3, the power unit_
  • the second AC output terminal of b3 and the second AC output terminal of power unit_c3 form a three-phase output of converter 300.
  • the second AC output terminal of the power unit_a1 is connected to the first AC output terminal of the power unit_a2, and the second AC output terminal and power unit of the power unit_a2 The first AC output terminal of _a3 is connected;
  • the second AC output terminal of the power unit_b1 is connected to the first AC output terminal of the power unit_b2, and the second AC output terminal of the power unit_b2 is the first of the power unit_b3 AC output terminal connection;
  • the second AC output terminal of the power unit_c1 is connected to the first AC output terminal of the power unit_c2, and the second AC output terminal of the power unit_c2 is the first of the power unit_c3 AC output terminal connection.
  • each cascaded power string in the converter 300 can include a greater number of power units, ie, the number of power units in each cascaded power string can be greater than or equal to three.
  • the converter 300 includes three cascaded power strings, each of which includes N power units, each of which has a set of three-phase input terminals, and the direct drive wind power in the embodiment of the present invention.
  • the generator is a multi-winding direct drive wind power generator, and the rotor of the multi-winding direct drive wind power generator is coaxially connected with the wind power generator.
  • the stator of the multi-winding direct drive wind power comprises 3N windings, and N is an integer greater than or equal to 3.
  • each of the three windings constitutes a set of three-phase outputs of the multi-winding direct drive wind turbine, and the three sets of three-phase outputs of the doubly-fed generator are respectively coupled with the three-phase input of the N power units of each cascaded power string The end corresponds to the connection.
  • the output voltage of the converter can be constrained by limiting the number of windings of the stator in a multi-winding direct drive wind turbine. Therefore, the converter of the embodiment of the present invention can superimpose and output a higher voltage by modularly cascading power units in each cascaded power string, greatly reducing the output current, and having an output de-harmonic. At the same time, it is different from the current low-voltage large-capacity converters in parallel to increase the capacity of the converter, thus avoiding technical problems such as current sharing and circulation, and improving the reliability of the fan system.
  • FIG. 5 shows a schematic structural diagram of a power unit according to an embodiment of the invention.
  • the power unit may include a three-phase rectifier module 3111, a bus capacitor and a discharge resistor 3112, and a chopper circuit module 3113 which are sequentially connected. And the H-bridge arm inverter module 3114.
  • the three-phase rectifier module 3111 is configured to be connected to one of the three-phase windings of the direct drive wind power generator via a three-phase inductor, and configured to perform low frequency alternating current power output by the direct drive wind power generator. Rectification converts low frequency AC energy into DC power.
  • the three-phase rectifier module can be, for example, a three-phase PWM rectifier.
  • a bus capacitor and discharge resistor 3112 is configured to be coupled to the two outputs of the three-phase rectifier module.
  • the bus capacitance can be configured to filter the converted DC power and store the DC power
  • the discharge resistor can 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 that exceeds the DC bus voltage threshold by the unloading resistor in the chopper circuit module 3113 when the DC bus voltage exceeds a predetermined DC bus voltage threshold.
  • the chopper circuit module 3113 may include a switching transistor Q1 and an unloading resistor R connected in series between the DC bus bars.
  • the switching transistor Q1 may be an insulated gate bipolar transistor (IGBT).
  • the chopper circuit module 3113 may further include a switching transistor Q2 connected in parallel with the unloading resistor R, and the switching transistor Q2 may be any one of a diode-containing IGBT, a diode-equipped MOS transistor, or a diode.
  • the switching transistor Q2 can be used as a diode.
  • the Chopper circuit module 3113 when the power grid of the wind farm occurs, for example, a low voltage ride-through condition causes the DC bus voltage to rise, and the DC bus voltage exceeds the preset DC bus voltage threshold, the Chopper circuit module 3113 can be disabled and disabled.
  • the switch Q1 of the resistor series is turned on, so that the energy of the pump rise in the DC bus is discharged through the switch Q1 and the unloading resistor R to prevent the DC bus from overvoltage.
  • the H-type bridge arm inverter module 3114 is configured to convert the voltage-adjustable DC power into a power frequency AC power that meets the requirements of the power grid.
  • the H-type bridge arm inverter module (which may be simply referred to as an H-bridge in the following description) includes two parallel bridge arms, each of which includes two power tubes connected in series.
  • the two output ends of the H-type bridge arm inverter module are a first AC terminal and a second AC terminal.
  • the input of each power unit of the cascaded power string in the converter is connected to a set of three-phase windings of the multi-winding DC generator, and the output of the power unit is an H-bridge arm inverter Two AC output terminals of the module, wherein the first AC terminal of the H bridge is connected to the second AC terminal of the serially connected previous power unit, and the second AC terminal of the H bridge is connected to the serial The first AC terminals of one power unit are connected.
  • FIG. 6 is a schematic structural diagram of an electronic control system according to an embodiment of the invention. As shown in FIG. 6, in an embodiment, the electronic control system 600 can include:
  • the motor rotor of the direct drive wind turbine 200 is directly coupled to the wind turbine of the wind turbine 100 for driving, and the converter connected to the direct drive wind turbine 200 may be a full power converter.
  • the electronic control system 600 can also include a pitch control system 610 and a master control system 620.
  • the pitch control system 610 can be used to adjust the blade pitch angle (referred to as the pitch angle) of the wind turbine as the wind speed changes, stabilizing the output power of the generator.
  • the pitch control system 610 can control the position angle of the blade chord of the wind power generator relative to the rotation plane, that is, the pitch angle.
  • the pneumatic wheel captured by the wind wheel is controlled by adjusting the pitch angle of the blade. Torque and pneumatic power enable the wind turbine to capture wind energy to the maximum extent and output power is stable.
  • the master control system 620 can be used to communicate with the pitch control system 610 and the converter 300, issue pitch control commands to the pitch control system 610, and communicate with the converter 300 through control
  • the converter regulates the active power and reactive power of the wind turbine.
  • the main control system 620 can communicate with the pitch control system 610 by receiving signals from the tank and the pitch control system, and output a pitch control command to the pitch control system 610 to control the pitch control system to complete the blade pitch.
  • the main control system 620 is the main body of the control system of the wind power generator, and can realize automatic starting, automatic steering, automatic speed regulation, automatic grid connection, automatic fault shutdown, automatic cable unwinding of the wind power generator. Important control and protection functions such as automatic recording and monitoring.
  • FIG. 7 is a schematic structural view showing a wind farm power transmission system according to an embodiment of the present invention, and the same or equivalent structures of FIG. 7 and FIG. 6 are given the same reference numerals.
  • the wind farm power transmission system 700 can include:
  • each set of power frequency step-up transformer 710 is connected to a group of electronic control systems 600 in a plurality of sets of electronic control systems, and each set of power frequency step-up transformers 710 is connected to the medium voltage power bus three-phase 720 through an inductor;
  • the frequency step-up transformer 710 is configured to convert the power frequency AC power output of the plurality of sets of electronic control systems 600 to meet the grid requirements of the medium voltage AC power, and convert the converted medium voltage AC power into the medium voltage.
  • Power bus 720 is configured to convert the power frequency AC power output of the plurality of sets of electronic control systems 600 to meet the grid requirements of the medium voltage AC power, and convert the converted medium voltage AC power into the medium voltage.
  • the wind farm power transmission system 700 may further include: a boost power transmission transformer 730 configured to convert medium voltage alternating current power into alternating power of a preset power transmission voltage level, and convert the power into a preset power transmission voltage level.
  • AC power is connected to the AC transmission bus 740.
  • the wind farm power transmission system 700 may further include: a reactive power compensation device 750 , which may be connected in parallel to the medium voltage between the medium voltage power supply bus 720 and the boost power transmission transformer 730 .
  • the reactive power compensation device 750 can be configured to perform reactive power compensation for the medium voltage power supply network.
  • the output voltage of the converter is increased by the modular cascade of the converter, the output current is greatly reduced, and the large batch is reduced.
  • the use of low voltage cables reduces losses and increases efficiency.
  • the current low-voltage large-capacity converter must avoid the choice of parallel lifting capacity, avoiding technical problems such as current sharing and circulation, and improving the reliability of the fan system.
  • Fig. 8 is a schematic diagram showing the topology of a wind farm power transmission system in the prior art.
  • the conventional wind farm-based power transmission system can be composed of multiple sets of doubly-fed AC wind turbines 30 and medium-voltage 35KV bus bars 40, each of which includes a wind power generator 31 and a double A generator 32, a low voltage converter 33 and a step-up transformer 34 are provided.
  • the doubly-fed generator comprises a three-phase stator winding 3201 and a three-phase rotor winding 3202; the three-phase stator winding 3201 of the doubly-fed generator 32 is connected with the low-voltage side of the step-up transformer 34; the rotor winding of the doubly-fed electric machine and the low-voltage converter
  • the three-phase cable on the wind turbine side of the compressor 33 is connected, and the three-phase cable on the grid side of the low voltage converter 33 can be connected to other electrical equipment such as the step-up transformer 34 in the grid or the grid.
  • the step-up transformer 34 can convert the power of 70% of the 690V AC voltage on the stator side of the doubly-fed generator 32 and the power of the 30% 690V AC voltage on the rotor side of the doubly-fed generator 120 into Medium voltage busbar of 35KV wind farm.
  • the output voltage of the converter is low and the current is large. Under the condition of delivering the same power, the loss of the transmission cable is large, and the efficiency of the fan generator set is not improved.
  • the use of low-voltage cables requiring a large amount of precious metals results in a large loss of the entire system.
  • the parallel system of the converter obtained by connecting the low-voltage converters in parallel is prone to cause serious circulation problems. The circulation problem will cause the current-sharing characteristics of the output current of the parallel system of the low-voltage converter to fail to achieve the desired effect, and the reliability of the fan system is reliable. Sexual effects.
  • the embodiment of the present invention provides a converter for a wind farm power transmission system, which changes the internal electrical structure of the converter, can increase the output voltage of the converter, reduce the output current, and reduce the whole machine. System losses and can increase the reliability of the fan system.
  • FIG. 9 is a schematic structural diagram of a converter according to another embodiment of the present invention.
  • the converter 400 may specifically include three cascaded power strings, wherein each cascaded power string may include a first output terminal and a second output terminal, the first output of each cascaded power string A star point connection is formed between the terminals, and the second output terminal of each cascaded power string forms a three-phase output of the converter 400; the three-phase input of each cascaded power string is coupled to the doubly-fed generator of the wind turbine.
  • each cascaded power string is coupled to a set of rotor windings of a doubly-fed generator of a wind turbine.
  • the three cascaded power strings are configured to convert the alternating current output from the doubly-fed generator rotor into power frequency alternating current electrical energy that meets the grid requirements.
  • the converter 400 can include a first cascaded power string 410, a second cascaded power string 420, and a third cascaded power string 430.
  • a star point connection is formed between the first output terminal of the first cascaded power string 410, the first output terminal of the second cascaded power string 420, and the first output terminal of the third cascaded power string 430.
  • the second output terminal of the first cascaded power string 410, the second output terminal of the second cascaded power string 420, and the second output terminal of the third cascaded power string 430 form a three-phase output of the converter.
  • the converter of the embodiment of the present invention is composed of a first cascade power string 410, a second cascade power string 420, and a third cascade power string 430, respectively, to form a three-phase system.
  • the single converter in the traditional converter can directly change the design of the converter system.
  • modular cascading the output voltage of the converter is increased, the output current is greatly reduced, and the low-voltage cable is reduced.
  • the use reduces the loss and improves the efficiency.
  • it avoids the choice of the parallel low-lift capacity of the low-voltage large-capacity converter, avoids the technical problems such as current sharing and circulation, and improves the reliability of the fan system.
  • FIG. 10 shows a detailed structural diagram of a converter according to further exemplary embodiments of the present invention, and the same or equivalent structures of FIG. 10 and FIG. 9 use the same reference numerals.
  • the converter 400 includes a first cascaded power string 410, a second cascaded power string 420, and a third cascaded power string 430, wherein the first cascaded power string 410 includes a plurality of power units For example, power unit_a1, power unit_a2, ..., power unit_aN; second cascaded power string 420 includes a plurality of power units such as power unit_b1, power unit_b2, ..., power unit_bN;
  • the third concatenated power string 330 includes a plurality of power units such as a power unit_c1, a power unit_c2, ..., a power unit_cN.
  • the cascaded power strings in the converter 400 may include a
  • each cascaded power string of the converter 400 includes a plurality of power units, wherein the three-phase inputs of each of the plurality of power units are in one-to-one correspondence with one of the doubly-fed generators Group rotor three-phase winding connection; serial connection between multiple power units included in each cascaded power string; each power unit includes a first AC output terminal and a second AC output terminal, each of the cascaded power strings a second AC terminal of a previous power unit of the adjacent two power units is connected to a first AC terminal of the next power unit, and a first AC terminal of the first power unit of each serially connected power string is used as A first output terminal of each cascaded power string, a second AC terminal of a last power unit of the serial connection of each cascaded power string acts as a second output terminal of each cascaded power string.
  • the first exchange of each power unit other than the first power unit connected in series and the last power unit connected in series may be The terminal is connected to a second AC terminal of a previous power unit to which it is serially connected, and its second AC terminal is connected to a first AC terminal of a next power unit to which it is serially connected.
  • each cascaded power string of the converter 400 includes three power units, that is, the power unit included in the first cascaded power string 410 in the cascaded power string is a power unit_a1, a power unit_ A2 and power unit_a3, the second cascaded power string 420 includes power units _b1, power unit _b2, and power unit _b3, and the power unit included in the third cascading power string 430 is a power unit _ C1, power unit_c2 and power unit_c3.
  • 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 respectively connected to a set of rotor three-phase windings of the doubly-fed generator ;
  • the power unit_a1, the power unit_a2 and the power unit_a3 are connected in series
  • the power unit_b1, the power unit_b2 and The power unit_b3 is serially connected
  • the power unit_c1, the power unit_c2 and the power unit_c3 are connected in series.
  • the first AC output terminal of the power unit_a1 serves as a first output terminal of the first cascaded power string 310
  • the first AC output terminal of the power unit_b1 serves as a first output terminal of the second cascaded power string 420
  • power The first AC output terminal of the unit_c1 serves as a first output terminal of the third cascaded power string 330
  • the first output terminal of each cascaded power string, that is, the first AC output terminal of the power unit_a1, the power unit_ a star point connection is formed between the first AC output terminal of b1 and the first AC output terminal of the power unit_c1;
  • the second AC output terminal of the power unit_a3 serves as a second output terminal of the first cascaded power string 410
  • the second AC output terminal of the power unit_b3 serves as a second output terminal of the second cascaded power string 420
  • power The second AC output terminal of the unit_c3 serves as a second output terminal of the third cascaded power string 430, and the second output terminal of each cascaded power string, that is, the second AC output terminal of the power unit_a3, the power unit_
  • the second AC output terminal of b3 and the second AC output terminal of power unit_c3 form a three-phase output of converter 400.
  • the second AC output terminal of the power unit_a1 is connected to the first AC output terminal of the power unit_a2, and the second AC output terminal and power unit of the power unit_a2 The first AC output terminal of _a3 is connected;
  • the second AC output terminal of the power unit_b1 is connected to the first AC output terminal of the power unit_b2, and the second AC output terminal of the power unit_b2 is the first of the power unit_b3 AC output terminal connection;
  • the second AC output terminal of the power unit_c1 is connected to the first AC output terminal of the power unit_c2, and the second AC output terminal of the power unit_c2 is the first of the power unit_c3 AC output terminal connection.
  • each cascaded power string in the converter 400 can include a greater number of power units, ie, the number of power units in each cascaded power string can be greater than or equal to three.
  • the converter 400 includes three cascaded power strings, each of the cascaded power strings includes N power units, each power unit has a set of three-phase inputs, and the doubly-fed generator includes a stator and a rotor, wherein The number of rotor windings disposed on the rotor of the doubly-fed generator is 3N, wherein each of the three windings constitutes a set of three-phase outputs of the doubly-fed generator, and the three sets of three-phase outputs of the doubly-fed generator are respectively and each stage The three-phase input terminals of the N power units of the power string are connected.
  • the doubly-fed generator in the embodiment of the present invention includes a stator and a rotor.
  • the stator and the rotor of the doubly-fed generator can output AC power to the power grid, and the AC power output from the stator side of the doubly-fed generator through the stator winding. It can be directly integrated into the grid through the grid-connected switch, and the AC power output from the rotor side of the doubly-fed generator through the rotor winding can be connected to the grid through the converter and the grid switch, and the rotor of the doubly-fed generator includes 3N windings. N is an integer multiple of 3, and each of the three rotor windings forms a set of ABC three-phase AC systems.
  • the converter modular multi-level medium voltage converter can constrain the output voltage of the converter by limiting the number of windings of the rotor in the doubly-fed generator. Therefore, the converter of the embodiment of the present invention can superimpose and output a higher voltage by modularly cascading power units in each cascaded power string, greatly reducing the output current, and having an output de-harmonic. At the same time, it is different from the current low-voltage large-capacity converters in parallel to increase the capacity of the converter, thus avoiding technical problems such as current sharing and circulation, and improving the reliability of the fan system.
  • FIG. 11 is a block diagram showing a specific structure of a power unit according to another embodiment of the present invention.
  • the power unit may include a three-phase rectifier module 4111, a bus capacitor and a discharge resistor 4112, and a chopper circuit module 4113 which are sequentially connected. And the H-bridge arm inverter module 4114.
  • a three-phase rectifier module 4111 is configured to be coupled to one of the three-phase windings of the doubly-fed generator via a three-phase cable and configured to rectify low-frequency AC power output from the doubly-fed generator, Convert low frequency AC power to DC power.
  • the three-phase rectifier module can be, for example, a three-phase PWM rectifier.
  • the three-phase rectifier module 4111 may be a three-bridge six-arm structure, and includes three parallel bridge arms, each of which includes two power tube units connected in series, and the power tube unit may be, for example, an insulated gate bipolar type. Insulated Gate Bipolar Transistor (IGBT).
  • IGBT Insulated Gate Bipolar Transistor
  • a bus capacitor and discharge resistor 4112 is configured to be coupled to the two outputs of the three-phase rectifier module.
  • the bus capacitance can be configured to filter the converted DC power and store the DC power
  • the discharge resistor can be configured to discharge the amount of power stored in the bus capacitor.
  • the chopper circuit module 4113 is configured to discharge energy in the DC bus that exceeds the DC bus voltage threshold by the unloading resistor in the chopper circuit module 4113 when the DC bus voltage exceeds a predetermined DC bus voltage threshold.
  • the chopper circuit module 4113 may include a switching transistor Q1 and an unloading resistor R connected in series between the DC bus bars.
  • the switching transistor Q1 can be an IGBT transistor.
  • the chopper circuit module 4113 may further include a switching transistor Q2 connected in parallel with the unloading resistor R, which may be any one of a diode-containing IGBT, a diode-equipped MOS transistor, or a diode.
  • the switching transistor Q2 can be used as a diode.
  • the Chopper circuit module 4113 when the power grid of the wind farm occurs, for example, a low voltage ride-through condition causes the DC bus voltage to rise, and the DC bus voltage exceeds the preset DC bus voltage threshold, the Chopper circuit module 4113 can be disabled and disabled.
  • the switch Q1 of the resistor series is turned on, so that the energy of the pump rise in the DC bus is discharged through the switch Q1 and the unloading resistor R to prevent the DC bus from overvoltage.
  • the H-type bridge arm inverter module 4114 is configured to convert the voltage-adjustable DC power into a power frequency AC power that meets the requirements of the power grid.
  • an H-type bridge arm inverter module (which may be simply referred to as an H-bridge in the following description) includes two parallel bridge arms, each of which includes two power tubes connected in series.
  • the two output ends of the H-type bridge arm inverter module are a first AC terminal and a second AC terminal.
  • the three-phase input of each power unit of the cascaded power string in the converter is connected to a set of rotor three-phase windings of the doubly-fed generator, and the output of the power unit is an H-bridge arm inverse Two AC output terminals of the transformer module, wherein a first AC terminal of the H-bridge is connected to a second AC terminal of a serially connected previous power unit, and a second AC terminal of the H-bridge is serially connected The first AC terminal of the next power unit is connected.
  • FIG. 12 is a schematic structural diagram of a wind farm power transmission system according to another embodiment of the present invention.
  • the wind farm power transmission system 800 can include:
  • a plurality of doubly-fed wind turbines 810 are connected in parallel, each doubly-fed wind turbine 810 comprising a doubly-fed generator 811 and the converter 400 described above in connection with Figures 9-11.
  • the doubly-fed generator 811 includes a stator and a rotor, the stator includes a stator three-phase winding, the rotor includes a plurality of rotor windings, the number of the plurality of rotor windings is 3N, and each of the three rotor windings forms a rotor three-phase winding of the doubly-fed generator Where N is an integer greater than or equal to 3, and the rotor three-phase winding of the doubly-fed generator 811 is connected to the current transformer 400.
  • the output power of the direct drive fan is completely different from that of the stator through the full power inverter, and the stator and the rotor of the doubly-fed generator 811 can feed the grid, and the alternating current energy of the stator side of the doubly-fed generator It can be directly integrated into the grid, and the AC energy on the rotor side of the doubly-fed generator can be integrated into the grid through the converter 400.
  • the frequency, voltage, amplitude and phase of the rotor winding power supply can be changed by the converter according to the operation requirements of the wind turbine generator set. Automatic adjustment, wind turbines can achieve constant frequency power generation at different speeds, meeting the requirements of power load and grid connection.
  • the doubly-fed generator of the embodiment of the invention is a medium-voltage doubly-fed generator.
  • the grid-side grid-connected cost can be reduced.
  • the output voltage of the stator-side of the doubly-fed generator can be increased. To 10kV.
  • the cascaded power string in the converter the output voltage of the converter is increased by modular cascading, the output current is reduced, the loss of the whole system is reduced, and the current low-voltage large capacity is avoided.
  • the flow device must be selected in parallel to increase the reliability of the fan system.
  • each doubly-fed wind turbine set 800 can further include a step-up transformer 812, which can also include a medium voltage power supply bus 820; the low voltage side of the step-up transformer 812 and the doubly-fed The stator three-phase winding of the generator 811 is connected, and the low voltage side of the step-up transformer 812 is connected to the three-phase output of the converter 400; the step-up transformer 812 is configured to output the alternating current power of the stator of the doubly-fed generator 811 and The AC power outputted by the converter 400 is converted into medium voltage AC power that meets the requirements of the power grid, and the converted medium voltage AC power is connected to the medium voltage power bus 820.
  • a step-up transformer 812 which can also include a medium voltage power supply bus 820; the low voltage side of the step-up transformer 812 and the doubly-fed The stator three-phase winding of the generator 811 is connected, and the low voltage side of the step-up transformer 812 is connected to the three-phase output of the converter 400; the step
  • the low voltage side of the step-up transformer 812 is connected to the stator three-phase winding of the doubly-fed generator 811, and the low-voltage side of the step-up transformer 812 and the three-phase output of the converter 400 are shown.
  • the high voltage side of the step-up transformer 812 is connected to the medium voltage power supply bus 820 in three phases.
  • the output voltage of the converter is increased by the modular cascade of the converter, the output current is greatly reduced, and the use of the high-voltage low-voltage cable is reduced. , reducing losses and improving efficiency.
  • the current low-voltage large-capacity converter must avoid the choice of parallel lifting capacity, avoiding technical problems such as current sharing and circulation, and improving the reliability of the fan system.
  • the embodiment of the present invention provides a converter for a wind farm power transmission system, where the converter includes three cascaded power strings; wherein each cascaded power string includes the first An output terminal and a second output terminal form a star point connection between the first output terminals of each cascaded power string, and the second output terminal of each cascaded power string forms a three-phase output of the converter; each cascade The three-phase input of the power string is connected to the generator of the wind turbine, and the generator includes a direct drive wind generator or a doubly-fed generator.
  • the output voltage of the converter is increased and the output is reduced by the cascaded power string in the converter in a modular cascade manner.
  • Current reduces the use of high-volume low-voltage cables and reduces the loss of the entire system.
  • the converter in the embodiment of the invention can avoid the selection of the parallel lifting capacity of the current low-voltage large-capacity converter, thereby avoiding technical problems such as current sharing and circulation of the parallel cable, and improving the reliability of the fan system.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

本发明实施例公开了一种用于风电场输电系统的变流器、电控系统和输电系统。该变流器包括三个级联功率串；其中，每个级联功率串包括第一输出端子和第二输出端子，每个级联功率串的第一输出端子之间形成星点连接，每个级联功率串的第二输出端子形成变流器的三相输出；每个级联功率串的三相输入与风力发电机组的发电机连接，发电机包括直驱风力发电机或双馈发电机。根据本发明实施例提供的变流器，可以升高变流器的输出电压，降低输出电流，减少整机系统的损耗，并可以减少大量低压电缆的使用，缓解风机系统的解缆压力，提高风电场输电系统稳定性。

Description

用于风电场输电系统的变流器、电控系统和输电系统 技术领域
本发明涉及风电并网技术领域，尤其涉及一种用于风电场输电系统的变流器、电控系统和输电系统。
背景技术
随着能源危机的加剧，新能源的开发与利用已成为研究的热点，风电是目前具有大规模开发潜能的可再生能源。风力发电机组是将风能转换为机械能，机械能带动发电机转子旋转，最终输出交流电的电力设备。由于我国风资源分布比较集中，风电开发采用了大规模、高度集中接入和远距离传输的模式。为了保证风力发电机组输出的低频交流电的电压稳定性，通常将风力发电机组输出的低频交流电能经过整流转变成直流电能，再经过逆变电路将直流电能转变成交流市电，才能保证稳定使用。
目前的风力发电机组输电系统中，通常利用变流器实现上述电能的传送与变换过程。实际应用时，风力发电机组的发电机位于塔顶的机舱，变流器一般位于风力发电机组的塔底的塔筒内，大量的低压电缆需要通过高塔筒传输到塔底的变流器，这使得塔筒内使用的电缆数量多，对风机系统的解缆造成很大的压力。
另外，随着风力发电机组的容量越来越大，低压变流器往往通过并联扩大容量。然而，低压变流器并联得到的变流器并联系统易引起严重的环流问题，环流问题会导致该低压变流器并联系统输出电流的均流特性达不到理想的效果，对风力发电机系统的可靠性造成影响。此外，变流器输出的电压较低，且输出电流较大，需要大量的贵金属的低压电缆的使用，造成整机系统的损耗较大。
发明内容
本发明实施例提供一种用于风电场输电系统的变流器、电控系统和风电场输电系统，可以升高变流器的输出电压，降低输出电流，减少整机系统的损耗，并可以减少大量低压电缆的使用，缓解风机系统的解缆压力，提高风电场输电系统稳定性。
根据本发明实施例的一方面，提供一种用于风电场输电系统的变流器，包括三个级联功率串；其中，每个级联功率串包括第一输出端子和第二输出端子，每个级联功率串的第一输出端子之间形成星点连接，每个级联功率串的第二输出端子形成变流器的三相输出；每个级联功率串的三相输入与风力发电机组的发电机连接，发电机包括直驱风力发电机或双馈发电机。
根据本发明实施例的另一方面，提供一种用于风电场输电系统的电控系统，包括发电机和上述实施例中的变流器；发电机为直驱风力发电机；直驱风力发电机被配置为包括多个绕组，多个绕组的数量为3N，并且每三个绕组形成一组三相绕组，其中，N为大于等于3的整数；变流器，被配置为通过多个绕组与直驱风力发电机连接。
根据本发明实施例的又一方面，提供一种风电场输电系统，包括上述实施例描述的电控系统、多组工频升压变压器和中压供电母线；其中，每组工频升压变压器的低压侧与多组电控系统中的一组电控系统连接，每组工频升压变压器通过电感与中压供电母线三相连接；多组工频升压变压器被配置用于将多组电控系统输出的符合电网要求的工频交流电能转换成符合电网要求的中压交流电能，并将转换得到的中压交流电能接入中压供电母线。
根据本发明实施例的再一方面，提供一种风电场输电系统，风电场输电系统包括并联的多个双馈风力发电机组，每个双馈风力发电机组包括双馈发电机和上述实施例描述的变流器；双馈发电机包括定子和转子，定子包括定子三相绕组，转子包括多个转子绕组，多个转子绕组的数量为3N，并且每三个转子绕组形成双馈发电机的转子三相绕组，其中，N为大于等于3的整数，双馈发电机的转子三相绕组连接于变流器。
根据本发明实施例中的变流器、电控系统和风电场输电系统，可以通过模块化级联的方式，通过变流器中的级联功率串，升高变流器的输出电 压，降低输出电流，减小了大批量低压电缆的使用，减小整机系统的损耗。同时，本发明实施例中的变流器可以避免目前低压大容量变流器必须进行并联提升容量的选择，从而避免了并联电缆的均流及环流等技术问题，提升了风机系统的可靠性。
附图说明
为了更清楚地说明本发明实施例的技术方案，下面将对本发明实施例中所需要使用的附图作简单地介绍，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是示出目前用于风力发电机组的变流器的结构及位置的示意图；
图2是示出目前基于风力发电机组的变流器的电控系统的拓扑结构示意图；
图3是示出根据本发明一实施例提供的变流器的结构示意图；
图4是示出根据本发明一些示例性实施例的变流器的详细结构示意图；
图5是示出根据本发明一实施例的功率单元的具体结构示意图；
图6是示出根据本发明一实施例提供的电控系统的结构示意图；
图7是示出了根据本发明一实施例的风电场输电系统的结构示意图；
图8是示出现有技术中风电场输电系统的拓扑结构示意图；
图9是示出根据本发明另一实施例提供的变流器的结构示意图；
图10是示出根据本发明另一些示例性实施例的变流器的详细结构示意图；
图11是示出根据本发明另一实施例的功率单元的具体结构示意图；
图12是示出根据本发明另一实施例提供的风电场输电系统的结构示意图。
在附图中，相同的部件使用相同的附图标记，标记说明如下：
10-风力发电机组；20-电控系统；21-直驱电机；2201-第一变流器；2202-第二变流器；
200-直驱风力发电机；
300-变流器；310-第一级联功率串；320-第二级联功率串；330-第三级 联功率串；
3111-三相整流器模块；3112-母线电容及放电电阻；3113-斩波电路模块；3114-H式桥臂逆变器模块；
600-电控系统；610-变桨控制系统；620-主控系统；
700-风电场输电系统；710-多组工频升压变压器；720-中压供电母线；730-升压输电变压器；740-交流电能接入交流输电母线；750-无功补偿装置；
30-双馈交流风力发电机组；40-中压35KV汇流母线；31-风力发电机；32-双馈发电机；33-低压变流器；34-升压变压器；
400-变流器；410-第一级联功率串；420-第二级联功率串；430-第三级联功率串；
4111-三相整流器模块；4112-母线电容及放电电阻；4113-斩波电路模块；4114-H式桥臂逆变器模块；
800-风电场输电系统；810-双馈风力发电机组；811-双馈发电机；812-升压变压器。
具体实施方式
下面将详细描述本发明的各个方面的特征和示例性实施例，为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细描述。应理解，此处所描述的具体实施例仅被配置为解释本发明，并不被配置为限定本发明。对于本领域技术人员来说，本发明可以在不需要这些具体细节中的一些细节的情况下实施。下面对实施例的描述仅仅是为了通过示出本发明的示例来提供对本发明更好的理解。
需要说明的是，在本文中，诸如第一和第二等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或者暗示这些实体或操作之间存在任何这种实际的关系或者顺序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、物品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、物 品或者设备所固有的要素。在没有更多限制的情况下，由语句“包括……”限定的要素，并不排除在包括所述要素的过程、方法、物品或者设备中还存在另外的相同要素。
图1是示出目前用于风力发电机组的变流器的结构及位置的示意图。如图1所示，风力发电机组的发电机通常位于塔顶的机舱，变流器一般位于风力发电机组的塔底的塔筒内，大量的低压电缆通过高塔筒传输到塔底的变流器，变流器将风力发电机组输出的低频交流电通过整流转变成直流电能，再经由逆变电路将直流电能转变为交流电能接入电网。
但是，该变流器的位置设置使得塔筒内使用的电缆数量多，风机系统的解缆压力很大。
在本发明实施例中，风力发电机组的发电机可以包括直驱风力发电机或双馈发电机。为了更好的理解本发明，下面结合图2至图7，详细描述风力发电机组的发电机为直驱风力发电机时，根据本发明实施例的变流器、电控系统和风电场输电系统。应注意，这些实施例并不是用来限制本发明公开的范围。
图2是示出目前基于风力发电机组的变流器的电控系统的拓扑结构示意图。如图2所示，电控系统20包括直驱电机21、第一变流器2201和第二变流器2202，直驱电机21连接于风力发电机组10。由图2可以看出，传统的变流器可以由第一变流器2201或变流器2202直接作为变流系统。例如，在第一变流器2201的风力发电机侧的三相通过电感，连接直驱电机定子的三相绕组；在第一变流器2201的电网侧的三相通过电感，接入电网中的其他电气设备例如升压变压器(图中未示出)。
但是，该变流器输出电压较低，电流较大，需要大量的贵金属的低压电缆的使用，造成整机系统的损耗较大。
随着风力发电机组的容量越来越大，低压变流器需要通过并联扩大容量。如图2所示，变流器可以由第一变流器2201和第二变流器2202组成变流器并联系统，在该变流器并联系统的风力发电机侧，每个变流器的三相通过电感，连接直驱电机定子的三相绕组；在该变流器并联系统的电网侧，每个变流器的交流输出并联，连接电网中其他电气设备例如升压变压 器的低压侧。
然而，低压变流器并联得到的变流器并联系统易引起严重的环流问题，环流问题会导致该低压变流器并联系统输出电流的均流特性达不到理想的效果，对风机系统的可靠性造成影响。
基于上述原因，本发明实施例提供了一种用于风电场输电系统的变流器，改变了变流器的内部电气结构，可以升高变流器的输出电压，降低输出电流，减少整机系统的损耗，并可以减少大量低压电缆的使用，缓解风机系统的解缆压力，提高风机系统的可靠性。图3示出了根据本发明一实施例提供的变流器的结构示意图。如图3所示，变流器300具体可以包括三个级联功率串，其中，每个级联功率串可以包括第一输出端子和第二输出端子，每个级联功率串的第一输出端子之间形成星点连接，每个级联功率串的第二输出端子形成变流器300的三相输出；每个级联功率串的三相输入与风力发电机组的直驱风力发电机连接。
在该实施例中，该三个级联功率串被配置为将直驱风力发电机输出的交流电转换成符合电网要求的工频交流电能。
作为一个示例，如图3所示，变流器300可以包括第一级联功率串310、第二级联功率串320、以及第三级联功率串330。
继续参考图3，第一级联功率串310的第一输出端子、第二级联功率串320的第一输出端子、以及第三级联功率串330的第一输出端子之间形成星点连接；第一级联功率串310的第二输出端子、第二级联功率串320的第二输出端子、以及第三级联功率串330的第二输出端子形成三相输出。
本发明实施例的变流器分别由第一级联功率串310、第二级联功率串320、以及第三级联功率串330一起构成三相系统。改变了传统变流器中单个变流器可以直接构成变流系统的设计，通过模块化级联的方式，升高变流器的输出电压，大大降低了输出电流，减小了大批量低压电缆的使用，减小了损耗，提高了效率；同时，避免了目前低压大容量变流器必须进行并联提升容量的选择，避免了均流及环流等技术问题，提升了风机系统的可靠性。
图4示出了根据本发明一些示例性实施例的变流器的详细结构示意图， 图4与图3相同或等同的结构使用相同的标号。如图4所示，变流器300包括第一级联功率串310、第二级联功率串320、以及第三级联功率串330，其中，第一级联功率串310包括多个功率单元例如功率单元_a1、功率单元_a2、……、功率单元_aN；第二级联功率串320包括多个功率单元例如功率单元_b1、功率单元_b2、……、功率单元_bN；第三级联功率串330包括多个功率单元例如功率单元_c1、功率单元_c2、……、功率单元_cN。但本发明并不局限于以上描述的，以及在图4中示出的特定的模块，在一些实施例中，变流器300中的级联功率串可以包含更灵活的配置，下面结合具体的实施例进行说明。
在一个实施例中，变流器300的每个级联功率串包括多个功率单元，其中，该多个功率单元中的每个功率单元的三相输入一一对应地与直驱风力发电机的一组三相绕组连接；每个级联功率串的多个功率单元之间串行连接；每个功率单元包括第一交流输出端子和第二交流输出端子，每个级联功率串中相邻两个功率单元中上一个功率单元的第二交流端子与下一个功率单元的第一交流端子连接，每个级联功率串的串行连接的第一个功率单元的第一交流端子作为每个级联功率串的第一输出端子，每个级联功率串的串行连接的最后一个功率单元的第二交流端子作为每个级联功率串的第二输出端子。
也就是说，对于每个级联功率串中串行连接的多个功率单元，可以将除串联连接的第一个功率单元和串联连接的最后一个功率单元以外的每个功率单元的第一交流端子与和其串行连接的上一个功率单元的第二交流端子连接，并将其第二交流端子与和其串行连接的下一个功率单元的第一交流端子连接。
作为一个示例，当变流器300的每个级联功率串包括三个功率单元时，即级联功率串中的第一级联功率串310包括的功率单元为功率单元_a1、功率单元_a2和功率单元_a3，第二级联功率串320包括的功率单元为功率单元_b1、功率单元_b2和功率单元_b3，以及第三级联功率串330包括的功率单元为功率单元_c1、功率单元_c2和功率单元_c3。
在该示例中，功率单元_a1的三相输入、功率单元_a2的三相输入、功 率单元_a3的三相输入、功率单元_b1的三相输入、功率单元_b2的三相输入、功率单元_b3的三相输入、功率单元_c1的三相输入、功率单元_c2的三相输入、以及功率单元_c3的三相输入分别于直驱风力发电机的一组三相绕组连接；
在第一级联功率串310中，功率单元_a1、功率单元_a2和功率单元_a3之间串行连接，在第二级联功率串320中，功率单元_b1、功率单元_b2和功率单元_b3之间串行连接，在第三级联功率串330中，功率单元_c1、功率单元_c2和功率单元_c3之间串行连接。
功率单元_a1的第一交流输出端子作为第一级联功率串310的第一输出端子，功率单元_b1的第一交流输出端子作为第二级联功率串320的第一输出端子，以及功率单元_c1的第一交流输出端子作为第三级联功率串330的第一输出端子，且每个级联功率串的第一输出端子即功率单元_a1的第一交流输出端子、功率单元_b1的第一交流输出端子、以及功率单元_c1的第一交流输出端子之间形成星点连接；
功率单元_a3的第二交流输出端子作为第一级联功率串310的第二输出端子，功率单元_b3的第二交流输出端子作为第二级联功率串320的第二输出端子，以及功率单元_c3的第二交流输出端子作为第三级联功率串330的第二输出端子，且每个级联功率串的第二输出端子即功率单元_a3的第二交流输出端子、功率单元_b3的第二交流输出端子、以及功率单元_c3的第二交流输出端子形成变流器300的三相输出。
在该示例中，第一级联功率串310中，功率单元_a1的第二交流输出端子与功率单元_a2的第一交流输出端子连接，功率单元_a2的第二交流输出端子与功率单元_a3的第一交流输出端子连接；
第二级联功率串320中，功率单元_b1的第二交流输出端子与功率单元_b2的第一交流输出端子连接，功率单元_b2的第二交流输出端子与功率单元_b3的第一交流输出端子连接；
第三级联功率串330中，功率单元_c1的第二交流输出端子与功率单元_c2的第一交流输出端子连接，功率单元_c2的第二交流输出端子与功率单元_c3的第一交流输出端子连接。
在一些实施例中，变流器300中的每个级联功率串可以包括更多数量的功率单元，即每个级联功率串中功率单元的数量可以为大于等于3。
如图4所示，变流器300包括三个级联功率串，每个级联功率串包括N个功率单元，每个功率单元有一组三相输入端，本发明实施例中的直驱风力发电机为多绕组直驱风力发电机，该多绕组直驱风力发电机的转子与风力发电机组同轴连接，该多绕组直驱风力的定子包括3N个绕组，且N为大于等于3的整数，其中，每3个绕组构成该多绕组直驱风力发电机的一组三相输出，双馈发电机的N组三相输出分别与每个级联功率串的N个功率单元的三相输入端对应连接。
在本发明实施例中，可以通过限制多绕组直驱风力发电机中定子的绕组数量来约束变流器的输出电压。因此，本发明实施例的变流器可以通过将每个级联功率串中的功率单元进行模块化级联的方式，叠加输出较高的电压，大大降低了输出电流，并具有输出去谐波少、模块化程度高的优点；同时，不同于目前低压大容量变流器进行并联以提升变流器容量的选择，从而避免了均流及环流等技术问题，提升了风机系统的可靠性。
图5示出了根据本发明一实施例的功率单元的具体结构示意图。如图5所示，作为变流器300的其中一个级联功率串的其中一个功率单元，该功率单元可以包括依次连接的三相整流器模块3111、母线电容及放电电阻3112、斩波电路模块3113、以及H式桥臂逆变器模块3114。
如图5所示，三相整流器模块3111，被配置为经由三相电感与直驱风力发电机的其中一组三相绕组连接，并且被配置为对直驱风力发电机输出的低频交流电能进行整流，将低频交流电能转换为直流电能。
作为一个示例，三相整流器模块例如可以是三相PWM整流器。
母线电容及放电电阻3112，被配置为连接于三相整流器模块的两个输出端。在图5中，母线电容可以被配置为对转换得到的直流电能进行滤波以及存储该直流电能，放电电阻可以被配置为对母线电容中储存的电量进行放电。
斩波电路模块3113，被配置为在直流母线电压超过预设的直流母线电压阈值时，通过斩波电路模块3113中的卸能电阻，卸放超过直流母线电 压阈值的直流母线中的能量。
如图5所示，斩波电路模块3113可以包括串联连接在直流母线之间的开关管Q1和卸能电阻R。作为一个示例，该开关管Q1可以为绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor，IGBT)。在该示例中，斩波电路模块3113还可以包括与卸能电阻R并联的开关管Q2，该开关管Q2可以是包含二极管的IGBT、带二极管的MOS管或二极管中的任意一种，在斩波电路模块3113中，开关管Q2可以作为二极管使用。
在该实施例中，当风电场的电网发生例如低压穿越等工况导致直流母线电压泵升，直流母线电压超过预设直流母线电压阈值时，可以通过控制该斩波电路模块3113中与卸能电阻串联的开关管Q1导通，使直流母线中泵升的能量经该开关管Q1和卸能电阻R进行卸放，以防止直流母线过压。
H式桥臂逆变器模块3114，用于将电压可调的直流电能转换成符合电网要求的工频交流电能。
在一个实施例中，如图5所示，H式桥臂逆变器模块(下述描述中可以简称为H桥)包括两个并联的桥臂，每个桥臂包括两个串联的功率管单元；H式桥臂逆变器模块的两个输出端为第一交流端子和第二交流端子。
在本发明实施例中，变流器中的级联功率串的每个功率单元的输入与多绕组直流发电机的一组三相绕组连接，该功率单元的输出为，H式桥臂逆变器模块的两路交流输出端子，其中，该H桥的第一交流端子与串行连接的上一个功率单元的第二交流端子相连接，该H桥的第二交流端子与串行连接的下一个功率单元的第一交流端子相连接。
图6示出了根据本发明一实施例提供的电控系统的结构示意图。如图6所示，在一个实施例中，电控系统600可以包括：
直驱风力发电机200和上述实施例描述的变流器300；直驱风力发电机200，被配置为包括多个绕组，多个绕组的数量可以为3N，N为大于等于3的正整数。其中，每三个绕组形成一组三相绕组；变流器300，被配置为通过多个绕组与直驱风力发电机连接。
在该实施例中，直驱风力发电机200的电机转子与风力发电机组100的风轮直接连接进行驱动，并且与直驱风力发电机200连接的变流器可以 是全功率变流器。
继续参考图5，在一个实施例中，电控系统600还可以包括：变桨控制系统610和主控系统620。
在一个实施例中，变桨控制系统610可以用于随着风速的变化调节风力发电机组的桨叶节距角(简称桨距角)，稳定发电机的输出功率。具体地，变桨控制系统610可以控制风力发电机的叶片弦长相对于旋转平面的位置角度即桨距角，当风速高于额定风速时，通过调节叶片的桨距角，控制风轮捕获的气动转矩和气动功率，使风电机组以其能最大限度地捕获风能、输出功率平稳。
在一个实施例中，主控系统620可以用于与变桨控制系统610和变流器300进行通讯，向变桨控制系统610发出变桨控制指令，以及与变流器300进行通讯，通过控制变流器以调节风力发电机的有功功率和无功功率。
具体地，主控系统620可以接收机舱柜及变桨控制系统的信号，与变桨控制系统610进行通讯，向变桨控制系统610发出变桨控制指令，控制变桨控制系统完成对叶片桨距角的调节，实现最大风能捕获和恒速运行；并用于控制变流器300调节风力发电机的有功功率和无功功率；以及与中央控制系统进行通讯、传递信息等。
在该实施例中，主控系统620为风力发电机的控制系统的主体，可以实现对风力发电机的自动启动、自动调向、自动调速、自动并网、故障自动停机、自动电缆解绕、自动记录与监控等重要控制和保护功能。
图7是示出了根据本发明一实施例的风电场输电系统的结构示意图，图7与图6相同或等同的结构使用相同的标号。如图7所示，风电场输电系统700可以包括：
多组上述实施例中描述的电控系统600、多组工频升压变压器710和中压供电母线720；其中，
每组工频升压变压器710的低压侧与多组电控系统中的一组电控系统600连接，每组工频升压变压器710通过电感与中压供电母线三相720连接；多组工频升压变压器710被配置用于将多组电控系统600输出的符合电网要求的工频交流电能转换成符合电网要求的中压交流电能，并将转换 得到的中压交流电能接入中压供电母线720。
如图7所示，风电场输电系统700还可以包括：升压输电变压器730，被配置为将中压交流电能转换成预设输电电压等级的交流电能，并将转换成预设输电电压等级的交流电能接入交流输电母线740。
继续参考图7，在一个实施例中，风电场输电系统700还可以包括：无功补偿装置750，无功补偿装置750可以并联于中压供电母线720与升压输电变压器730之间的中压供电网络中，并且，无功补偿装置750可以被配置为对中压供电网络进行无功补偿。
根据本发明实施例的变流器、电控系统和风电场输电系统，通过变流器模块化级联的方式，升高变流器的输出电压，大大降低了输出电流，减小了大批量低压电缆的使用，减小了损耗，提高了效率。同时，避免了目前低压大容量变流器必须进行并联提升容量的选择，避免了均流及环流等技术问题，提升了风机系统的可靠性。
在本发明实施例中，风力发电机组的发电机为直驱风力发电机时，根据本发明实施例的风电场输电系统中的变流器的其他细节与以上结合图1至图5描述的变流器类似，在此不再赘述。
为了更好的理解本发明，下面将结合图8至图12，详细描述风力发电机组的发电机为双馈发电机时，根据本发明实施例的变流器、电控系统和风电场输电系统。应注意，这些实施例并不是用来限制本发明公开的范围。
图8是示出现有技术中风电场输电系统的拓扑结构示意图。如图8所示，传统的基于风电场的输电系统可以由多组双馈交流风力发电机组30和中压35KV汇流母线40构成，每组双馈交流风力发电机组30包括风力发电机31、双馈发电机32、低压变流器33和升压变压器34。其中，双馈发电机包含三相定子绕组3201和三相转子绕组3202；双馈发电机32的三相定子绕组3201与升压变压器34的低压侧连接；双馈电机的转子绕组与低压变流器33的风力发电机侧的三相电缆相连接，低压变流器33的电网侧的三相电缆可以接入电网或电网中的其他电气设备例如升压变压器34。
作为一个示例，升压变压器34可以将在双馈发电机32的定子侧的70％的690V交流电压的功率，和双馈发电机120的转子侧的30％的690V交流 电压的功率，转换成35KV风电场的中压母线。
但是，该变流器输出电压较低且电流较大，在输送同等功率的条件下，传输线缆的损耗很大，风机发电机组的效率得不到提高。需要大量的贵金属的低压电缆的使用，造成整机系统的损耗较大。随着风力发电机组的容量越来越大，低压变流器需要通过并联扩大容量。然而，低压变流器并联得到的变流器并联系统易引起严重的环流问题，环流问题会导致该低压变流器并联系统输出电流的均流特性达不到理想的效果，对风机系统的可靠性造成影响。
基于上述原因，本发明实施例提供了一种用于风电场输电系统的变流器，改变了变流器的内部电气结构，可以升高变流器的输出电压，降低输出电流，减少整机系统的损耗，并可以提高风机系统的可靠性。
图9示出了根据本发明另一实施例提供的变流器的结构示意图。如图9所示，变流器400具体可以包括三个级联功率串，其中，每个级联功率串可以包括第一输出端子和第二输出端子，每个级联功率串的第一输出端子之间形成星点连接，每个级联功率串的第二输出端子形成变流器400的三相输出；每个级联功率串的三相输入与风力发电机组的双馈发电机连接。
作为一个示例，每个级联功率串的三相输入与风力发电机组的双馈发电机的一组转子绕组连接。
在该实施例中，该三个级联功率串被配置为可以将双馈发电机转子输出的交流电转换成符合电网要求的工频交流电能。
作为一个示例，如图9所示，变流器400可以包括第一级联功率串410、第二级联功率串420、以及第三级联功率串430。
继续参考图9，第一级联功率串410的第一输出端子、第二级联功率串420的第一输出端子、以及第三级联功率串430的第一输出端子之间形成星点连接；第一级联功率串410的第二输出端子、第二级联功率串420的第二输出端子、以及第三级联功率串430的第二输出端子形成变流器的三相输出端。
本发明实施例的变流器分别由第一级联功率串410、第二级联功率串420、以及第三级联功率串430一起构成三相系统。改变了传统变流器中 单个变流器可以直接构成变流系统的设计，通过模块化级联的方式，升高变流器的输出电压，大大降低了输出电流，减小了大批量低压电缆的使用，减小了损耗，提高了效率；同时，避免了目前低压大容量变流器必须进行并联提升容量的选择，避免了均流及环流等技术问题，提升了风机系统的可靠性。
图10示出了根据本发明另一些示例性实施例的变流器的详细结构示意图，图10与图9相同或等同的结构使用相同的标号。如图10所示，变流器400包括第一级联功率串410、第二级联功率串420、以及第三级联功率串430，其中，第一级联功率串410包括多个功率单元例如功率单元_a1、功率单元_a2、……、功率单元_aN；第二级联功率串420包括多个功率单元例如功率单元_b1、功率单元_b2、……、功率单元_bN；第三级联功率串330包括多个功率单元例如功率单元_c1、功率单元_c2、……、功率单元_cN。但本发明并不局限于以上描述的，以及在图10中示出的特定的模块，在一些实施例中，变流器400中的级联功率串可以包含更灵活的配置，下面结合具体的实施例进行说明。
在一个实施例中，变流器400的每个级联功率串包括多个功率单元，其中，多个功率单元中的每个功率单元的三相输入一一对应地与双馈发电机的一组转子三相绕组连接；每个级联功率串所包括的多个功率单元之间串行连接；每个功率单元包括第一交流输出端子和第二交流输出端子，每个级联功率串中相邻两个功率单元中上一个功率单元的第二交流端子与下一个功率单元的第一交流端子连接，每个级联功率串的串行连接的第一个功率单元的第一交流端子作为每个级联功率串的第一输出端子，每个级联功率串的串行连接的最后一个功率单元的第二交流端子作为每个级联功率串的第二输出端子。
也就是说，对于每个级联功率串中串行连接的多个功率单元，可以将除串联连接的第一个功率单元和串联连接的最后一个功率单元以外的每个功率单元的第一交流端子与和其串行连接的上一个功率单元的第二交流端子连接，并将其第二交流端子与和其串行连接的下一个功率单元的第一交流端子连接。
作为一个示例，当变流器400的每个级联功率串包括三个功率单元时，即级联功率串中的第一级联功率串410包括的功率单元为功率单元_a1、功率单元_a2和功率单元_a3，第二级联功率串420包括的功率单元为功率单元_b1、功率单元_b2和功率单元_b3，以及第三级联功率串430包括的功率单元为功率单元_c1、功率单元_c2和功率单元_c3。
在该示例中，功率单元_a1的三相输入、功率单元_a2的三相输入、功率单元_a3的三相输入、功率单元_b1的三相输入、功率单元_b2的三相输入、功率单元_b3的三相输入、功率单元_c1的三相输入、功率单元_c2的三相输入、以及功率单元_c3的三相输入分别于双馈发电机的一组转子三相绕组连接；
在第一级联功率串410中，功率单元_a1、功率单元_a2和功率单元_a3之间串行连接，在第二级联功率串420中，功率单元_b1、功率单元_b2和功率单元_b3之间串行连接，在第三级联功率串430中，功率单元_c1、功率单元_c2和功率单元_c3之间串行连接。
功率单元_a1的第一交流输出端子作为第一级联功率串310的第一输出端子，功率单元_b1的第一交流输出端子作为第二级联功率串420的第一输出端子，以及功率单元_c1的第一交流输出端子作为第三级联功率串330的第一输出端子，且每个级联功率串的第一输出端子即功率单元_a1的第一交流输出端子、功率单元_b1的第一交流输出端子、以及功率单元_c1的第一交流输出端子之间形成星点连接；
功率单元_a3的第二交流输出端子作为第一级联功率串410的第二输出端子，功率单元_b3的第二交流输出端子作为第二级联功率串420的第二输出端子，以及功率单元_c3的第二交流输出端子作为第三级联功率串430的第二输出端子，且每个级联功率串的第二输出端子即功率单元_a3的第二交流输出端子、功率单元_b3的第二交流输出端子、以及功率单元_c3的第二交流输出端子形成变流器400的三相输出。
在该示例中，第一级联功率串410中，功率单元_a1的第二交流输出端子与功率单元_a2的第一交流输出端子连接，功率单元_a2的第二交流输出端子与功率单元_a3的第一交流输出端子连接；
第二级联功率串420中，功率单元_b1的第二交流输出端子与功率单元_b2的第一交流输出端子连接，功率单元_b2的第二交流输出端子与功率单元_b3的第一交流输出端子连接；
第三级联功率串430中，功率单元_c1的第二交流输出端子与功率单元_c2的第一交流输出端子连接，功率单元_c2的第二交流输出端子与功率单元_c3的第一交流输出端子连接。
在一些实施例中，变流器400中的每个级联功率串可以包括更多数量的功率单元，即每个级联功率串中功率单元的数量可以为大于等于3。
作为一个示例，变流器400包括三个级联功率串，每个级联功率串包括N个功率单元，每个功率单元有一组三相输入端，双馈发电机包括定子和转子，其中，该双馈发电机的转子上设置的转子绕组数量为3N个，其中，每3个绕组构成双馈发电机的一组三相输出，双馈发电机的N组三相输出分别与每个级联功率串的N个功率单元的三相输入端对应连接。
如图10所示，本发明实施例中的双馈发电机包括定子和转子，双馈发电机的定子和转子均可以向电网输出交流电能，双馈发电机定子侧通过定子绕组输出的交流电能可以通过并网开关直接并入电网，而双馈发电机转子侧通过转子绕组输出的交流电能可以通过变流器和并网开关接入电网，且该双馈发电机的转子包括3N个绕组，N为3的整数倍，每三个转子绕组形成一组ABC三相交流系统。
在本发明实施例中，变流器模块化多电平中压变流器，通过限制双馈发电机中转子的绕组数量可以约束变流器的输出电压。因此，本发明实施例的变流器可以通过将每个级联功率串中的功率单元进行模块化级联的方式，叠加输出较高的电压，大大降低了输出电流，并具有输出去谐波少、模块化程度高的优点；同时，不同于目前低压大容量变流器进行并联以提升变流器容量的选择，从而避免了均流及环流等技术问题，提升了风机系统的可靠性。
图11示出了根据本发明另一实施例的功率单元的具体结构示意图。如图11所示，作为变流器400的其中一个级联功率串的其中一个功率单元，该功率单元可以包括依次连接的三相整流器模块4111、母线电容及放 电电阻4112、斩波电路模块4113、以及H式桥臂逆变器模块4114。
如图11所示，三相整流器模块4111，被配置为经由三相电缆与双馈发电机的其中一组三相绕组连接，并且被配置为对双馈发电机输出的低频交流电能进行整流，将低频交流电能转换为直流电能。
作为一个示例，三相整流器模块例如可以是三相PWM整流器。具体地，三相整流器模块4111可以是三桥六臂结构，且包括三个并联的桥臂，每个桥臂包括两个串联的功率管单元，该功率管单元例如可以是绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor，IGBT)。
母线电容及放电电阻4112，被配置为连接于三相整流器模块的两个输出端。在图11中，母线电容可以被配置为对转换得到的直流电能进行滤波以及存储该直流电能，放电电阻可以被配置为对母线电容中储存的电量进行放电。
斩波电路模块4113，被配置为在直流母线电压超过预设的直流母线电压阈值时，通过斩波电路模块4113中的卸能电阻，卸放超过直流母线电压阈值的直流母线中的能量。
如图11所示，斩波电路模块4113可以包括串联连接在直流母线之间的开关管Q1和卸能电阻R。作为一个示例，该开关管Q1可以IGBT晶体管。在该示例中，斩波电路模块4113还可以包括与卸能电阻R并联的开关管Q2，该开关管Q2可以是包含二极管的IGBT、带二极管的MOS管或二极管中的任意一种，在斩波电路模块4113中，开关管Q2可以作为二极管使用。
在该实施例中，当风电场的电网发生例如低压穿越等工况导致直流母线电压泵升，直流母线电压超过预设直流母线电压阈值时，可以通过控制该斩波电路模块4113中与卸能电阻串联的开关管Q1导通，使直流母线中泵升的能量经该开关管Q1和卸能电阻R进行卸放，以防止直流母线过压。
H式桥臂逆变器模块4114，用于将电压可调的直流电能转换成符合电网要求的工频交流电能。
如图11所示，在一个实施例中，H式桥臂逆变器模块(下述描述中可以简称为H桥)包括两个并联的桥臂，每个桥臂包括两个串联的功率管单 元；H式桥臂逆变器模块的两个输出端为第一交流端子和第二交流端子。
在本发明实施例中，变流器中的级联功率串的每个功率单元的三相输入与双馈发电机的一组转子三相绕组连接，该功率单元的输出为H式桥臂逆变器模块的两路交流输出端子，其中，该H桥的第一交流端子与串行连接的上一个功率单元的第二交流端子相连接，该H桥的第二交流端子与串行连接的下一个功率单元的第一交流端子相连接。
图12示出了根据本发明另一实施例提供的风电场输电系统的结构示意图。如图12所示，在一个实施例中，风电场输电系统800可以包括：
并联的多个双馈风力发电机组810，每个双馈风力发电机组810包括双馈发电机811和上述实施例中结合图9至图11描述的变流器400。
该双馈发电机811包括定子和转子，定子包括定子三相绕组，转子包括多个转子绕组，多个转子绕组的数量为3N，并且每三个转子绕组形成双馈发电机的转子三相绕组，其中，N为大于等于3的整数，双馈发电机811的转子三相绕组连接于变流器400。
在该实施例中，与直驱风机的输出功率完全由定子通过全功率变频器并网不同，双馈发电机811的定子和转子都能向电网馈电，双馈发电机定子侧的交流电能可以直接并入电网，而双馈发电机转子侧的交流电能可以通过变流器400并入电网，转子绕组电源的频率、电压、幅值和相位可以按风机发电机组的运行要求由变流器自动调节，风力发电机组可以在不同的转速下实现恒频发电，满足用电负载和并网的要求。
本发明实施例的双馈发电机为中压双馈发电机，通过提升双馈发电机的定子端口电压等级可以降低转子侧的并网成本，例如可以将双馈发电机定子侧的输出电压提升到10kV。与此同时，利用变流器中的级联功率串，通过模块化级联的方式，提升变流器的输出电压，降低输出电流，减小整机系统的损耗，并避免目前低压大容量变流器必须进行并联提升容量的选择，提升了风机系统的可靠性。
继续参考图12，在一个实施例中，每个双馈风力发电机组800还可以包括升压变压器812，风电场输电系统还可以包括中压供电母线820；升压变压器812的低压侧与双馈发电机811的定子三相绕组连接，并且升压 变压器812的低压侧与变流器400的三相输出连接；升压变压器812被配置用于将双馈发电机811的定子输出的交流电能和变流器400输出的交流电能转换成符合电网要求的中压交流电能，并将转换得到的中压交流电能接入中压供电母线820。
如图12所示，在本发明实施例中，升压变压器812的低压侧与双馈发电机811的定子三相绕组连接，并且升压变压器812的低压侧与变流器400的三相输出连接；升压变压器812的高压侧与中压供电母线820三相连接。
根据本发明实施例的变流器和风电场输电系统，通过变流器模块化级联的方式，升高变流器的输出电压，大大降低了输出电流，减小了大批量低压电缆的使用，减小了损耗，提高了效率。同时，避免了目前低压大容量变流器必须进行并联提升容量的选择，避免了均流及环流等技术问题，提升了风机系统的可靠性。
在本发明实施例中，风力发电机组的发电机为双馈发电机时，根据本发明实施例的变流器的其他细节与以上结合图8至图11描述的变流器类似，在此不再赘述。
通过上述实施例的描述可知，本发明实施例提供一种用于风电场输电系统的变流器，其中，变流器包括三个级联功率串；其中，每个级联功率串包括第一输出端子和第二输出端子，每个级联功率串的第一输出端子之间形成星点连接，每个级联功率串的第二输出端子形成变流器的三相输出；每个级联功率串的三相输入与风力发电机组的发电机连接，发电机包括直驱风力发电机或双馈发电机。
根据本发明实施例中的变流器、电控系统和风电场输电系统，以模块化级联的方式，通过变流器中的级联功率串，升高变流器的输出电压，降低输出电流，减小了大批量低压电缆的使用，减小整机系统的损耗。同时，本发明实施例中的变流器可以避免目前低压大容量变流器必须进行并联提升容量的选择，从而避免了并联电缆的均流及环流等技术问题，提升了风机系统的可靠性。
需要明确的是，本发明并不局限于上文所描述并在图中示出的特定配 置和处理。为了简明起见，这里省略了对已知方法的详细描述。在上述实施例中，描述和示出了若干具体的步骤作为示例。但是，本发明的方法过程并不限于所描述和示出的具体步骤，本领域的技术人员可以在领会本发明的精神后，作出各种改变、修改和添加，或者改变步骤之间的顺序。
以上所述，仅为本发明的具体实施方式，所属领域的技术人员可以清楚地了解到，为了描述的方便和简洁，上述描述的系统、模块和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。应理解，本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本发明的保护范围之内。

Claims (15)

  1. 一种用于风电场输电系统的变流器，其特征在于，所述变流器包括三个级联功率串；其中，
    每个级联功率串包括第一输出端子和第二输出端子，所述每个级联功率串的第一输出端子之间形成星点连接，所述每个级联功率串的第二输出端子形成所述变流器的三相输出；
    所述每个级联功率串的三相输入与风力发电机组的发电机连接，所述发电机包括直驱风力发电机或双馈发电机。
  2. 根据权利要求1所述的变流器，其特征在于，所述发电机包括直驱风力发电机；所述每个级联功率串包括多个功率单元；其中，
    每个功率单元的三相输入一一对应地与所述直驱风力发电机的一组三相绕组连接；
    所述每个级联功率串的所述多个功率单元之间串行连接；
    所述每个功率单元包括第一交流输出端子和第二交流输出端子，每个级联功率串中相邻两个功率单元中上一个功率单元的第二交流端子与下一个功率单元的第一交流端子连接，所述每个级联功率串的串行连接的第一个功率单元的第一交流端子作为所述每个级联功率串的第一输出端子，所述每个级联功率串的串行连接的最后一个功率单元的第二交流端子作为所述每个级联功率串的第二输出端子。
  3. 根据权利要求2所述的变流器，其特征在于，所述每个功率单元包括依次连接的三相整流器模块、母线电容、放电电阻、斩波电路模块、以及H式桥臂逆变器模块，其中，
    所述三相整流器模块，被配置为经由三相电感与所述直驱风力发电机的其中一组三相绕组连接，并且被配置为对所述直驱风力发电机输出的低频交流电能进行整流，将所述低频交流电能转换为直流电能；
    所述母线电容及所述放电电阻被配置为连接于所述三相整流器模块的两个输出端；
    所述斩波电路模块，被配置为在所述直流母线电压超过预设的直流母 线电压阈值时，通过所述斩波电路模块中的卸能电阻，卸放超过所述直流母线电压阈值的直流母线中的能量；
    所述H式桥臂逆变器模块，用于将所述电压可调的直流电能转换成符合电网要求的工频交流电能。
  4. 根据权利要求1所述的变流器，其特征在于，
    所述变流器的三相输出连接于所述风力发电机组的升压变压器。
  5. 根据权利要求1所述的变流器，其特征在于，所述发电机包括双馈发电机；所述每个功率单元包括依次连接的三相整流器模块、母线电容、放电电阻、斩波电路模块、以及H式桥臂逆变器模块，其中，
    所述三相整流器模块，被配置为经由三相电缆与所述双馈发电机的其中一组三相绕组连接，并且被配置为对所述双馈发电机输出的低频交流电能进行整流，将所述低频交流电能转换为直流电能；
    所述母线电容及所述放电电阻，被配置为连接于所述三相整流器模块的两个输出端；
    所述斩波电路模块，被配置为在所述直流母线电压超过预设的直流母线电压阈值时，通过所述斩波电路模块中的卸能电阻，卸放超过所述直流母线电压阈值的直流母线中的能量；
    所述H式桥臂逆变器模块，用于将所述电压可调的直流电能转换成符合电网要求的工频交流电能。
  6. 根据权利要求3或5所述的变流器，其特征在于，
    所述H式桥臂逆变器模块包括两个并联的桥臂，每个桥臂包括两个串联的功率管单元；
    所述H式桥臂逆变器模块的两个输出端为所述第一交流端子和所述第二交流端子。
  7. 一种用于风电场输电系统的电控系统，其特征在于，所述电控系统包括发电机和如权利要求1-3及6中任一项所述的变流器；所述发电机为直驱风力发电机；
    所述直驱风力发电机，被配置为包括多个绕组，所述多个绕组的数量为3N，并且每三个绕组形成一组三相绕组，其中，N为大于等于3的整数；
    所述变流器，被配置为通过所述多个绕组与所述直驱风力发电机连接。
  8. 根据权利要求7所述的电控系统，其特征在于，所述电控系统还包括主控系统和变桨控制系统；
    所述主控系统，被配置用于与所述变桨控制系统和变流器进行通讯，向所述变桨控制系统发出变桨控制指令，以及与所述变流器进行通讯，通过控制所述变流器以调节风力发电机的有功功率和无功功率；
    所述变桨控制系统，被配置用于根据所述变桨控制指令调节风力发电机叶片的桨距角。
  9. 一种风电场输电系统，其特征在于，所述风电场输电系统包括：
    多组如权利要求7或8所述的电控系统、多组工频升压变压器和中压供电母线；其中，
    每组工频升压变压器的低压侧与所述多组电控系统中的一组电控系统连接，所述每组工频升压变压器通过电感与所述中压供电母线三相连接；
    所述多组工频升压变压器被配置用于将所述多组电控系统输出的符合电网要求的工频交流电能转换成符合电网要求的中压交流电能，并将所述转换得到的中压交流电能接入所述中压供电母线。
  10. 根据权利要求9所述的风电场输电系统，其特征在于，所述风电场输电系统还包括：升压输电变压器和交流输电母线；
    升压输电变压器，被配置为将所述中压交流电能转换成预设输电电压等级的交流电能，并将所述预设输电电压等级的交流电能接入所述交流输电母线。
  11. 根据权利要求10所述的风电场输电系统，其特征在于，所述风电场输电系统还包括：
    无功补偿装置，所述无功补偿装置并联于所述中压供电母线与所述升压输电变压器之间的中压供电网络中，并且，所述无功补偿装置被配置为对所述中压供电网络进行无功补偿。
  12. 一种风电场输电系统，其特征在于，所述风电场输电系统包括并联的多个双馈风力发电机组，每个双馈风力发电机组包括双馈发电机和如权利要求1及4-6中任一项所述的变流器；
    所述双馈发电机包括定子和转子，所述定子包括定子三相绕组，所述转子包括多个转子绕组，所述多个转子绕组的数量为3N，并且每三个转子绕组形成所述双馈发电机的转子三相绕组，其中，N为大于等于3的整数，所述双馈发电机的转子三相绕组连接于所述变流器。
  13. 根据权利要求12所述的风电场输电系统，其特征在于，所述每个双馈风力发电机组还包括升压变压器，所述风电场输电系统还包括中压供电母线；
    所述升压变压器的低压侧与所述双馈发电机的定子三相绕组连接，并且所述升压变压器的低压侧与所述变流器的三相输出连接；
    所述升压变压器被配置用于将所述双馈发电机的定子输出的交流电能和所述变流器输出的交流电能转换成符合电网要求的中压交流电能，并将所述转换得到的中压交流电能接入所述中压供电母线。
  14. 根据权利要求13所述的风电场输电系统，其特征在于，
    所述升压变压器的低压侧与所述双馈发电机的定子三相绕组连接，并且所述升压变压器的低压侧与所述变流器的三相输出连接；
    所述升压变压器的高压侧与所述中压供电母线三相连接。
  15. 根据权利要求14所述的风电场输电系统，其特征在于，
    所述双馈发电机为中压双馈发电机。
PCT/CN2018/092000 2017-12-26 2018-06-20 用于风电场输电系统的变流器、电控系统和输电系统 WO2019128145A1 (zh)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CN201711437685.6A CN108631356B (zh) 2017-12-26 2017-12-26 用于风电场输电系统的变流器和风电场输电系统
CN201711432843.9A CN108631355A (zh) 2017-12-26 2017-12-26 变流器、电控系统和风电场输电系统
CN201711437685.6 2017-12-26
CN201711432843.9 2017-12-26

Publications (1)

Publication Number Publication Date
WO2019128145A1 true WO2019128145A1 (zh) 2019-07-04

Family

ID=67062967

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2018/092000 WO2019128145A1 (zh) 2017-12-26 2018-06-20 用于风电场输电系统的变流器、电控系统和输电系统

Country Status (1)

Country Link
WO (1) WO2019128145A1 (zh)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4163492A1 (en) * 2021-10-08 2023-04-12 General Electric Renovables España S.L. Wind turbine generators and methods for rotating a hub of a wind turbine

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101465606A (zh) * 2008-09-17 2009-06-24 刘建政 直驱风力发电系统并网变流器
CN102157958A (zh) * 2011-03-22 2011-08-17 深圳市禾望电气有限公司 一种采用多套绕组发电机的风力发电机组
CN105375523A (zh) * 2015-12-03 2016-03-02 科诺伟业风能设备（北京）有限公司 一种风电全功率变流器高电压穿越控制方法
CN207588466U (zh) * 2017-12-26 2018-07-06 北京金风科创风电设备有限公司 用于风电场输电系统的变流器和风电场输电系统

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101465606A (zh) * 2008-09-17 2009-06-24 刘建政 直驱风力发电系统并网变流器
CN102157958A (zh) * 2011-03-22 2011-08-17 深圳市禾望电气有限公司 一种采用多套绕组发电机的风力发电机组
CN105375523A (zh) * 2015-12-03 2016-03-02 科诺伟业风能设备（北京）有限公司 一种风电全功率变流器高电压穿越控制方法
CN207588466U (zh) * 2017-12-26 2018-07-06 北京金风科创风电设备有限公司 用于风电场输电系统的变流器和风电场输电系统

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4163492A1 (en) * 2021-10-08 2023-04-12 General Electric Renovables España S.L. Wind turbine generators and methods for rotating a hub of a wind turbine
US11959464B2 (en) 2021-10-08 2024-04-16 General Electric Renovables Espana, S.L. Wind turbine generators and methods for rotating a hub of a wind turbine

Similar Documents

Publication Publication Date Title
de Freitas et al. Rectifier topologies for permanent magnet synchronous generator on wind energy conversion systems: A review
EP2944006B1 (en) Turbine-based energy generation system with dc output
AU2010353929B2 (en) Converting device of electrical energy
CN101345423B (zh) 用于风力发电系统的五电平h桥级联背靠背变流器
US20140091630A1 (en) Medium voltage dc collection system with power electronics
Islam et al. Power converters for wind turbines: Current and future development
CN108631355A (zh) 变流器、电控系统和风电场输电系统
CN201039016Y (zh) 兆瓦级直驱式风电并网变流器
CN105790305B (zh) 基于全桥mmc直流侧串联的海上风电并网系统及其控制方法
CN101051793A (zh) 兆瓦级直驱式风电并网变流器
US10107264B2 (en) Medium voltage wind power generation system and power generation method using the same
CN107887924A (zh) 风机输电系统
CN108092257A (zh) 一种18相风力发电机直流并网结构及其控制方法
CN108879773A (zh) 一种六相风力发电机直流并网结构及其控制方法
CN107947222A (zh) 直流风机输电系统
CN108631356B (zh) 用于风电场输电系统的变流器和风电场输电系统
CN109449990B (zh) 一种永磁直驱风力发电系统及控制方法
Rafin et al. Power Electronic Converters for Wind Power Generation
CN207530550U (zh) 基于风电场的输电系统
CN106356889A (zh) 永磁风力发电机组
CN219372037U (zh) 风力发电机组
CN201528280U (zh) 全功率直驱式风电机组柔性并网变流器
WO2019128145A1 (zh) 用于风电场输电系统的变流器、电控系统和输电系统
CN101447678A (zh) 一种多绕组风力发电机接入电网的方法
CN207801488U (zh) 变流器、电控系统和风电场输电系统

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 18893845

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

32PN Ep: public notification in the ep bulletin as address of the adressee cannot be established

Free format text: NOTING OF LOSS OF RIGHTS PURSUANT TO RULE 112(1) EPC (EPO FORM 1205A DATED 23/10/2020)

122 Ep: pct application non-entry in european phase

Ref document number: 18893845

Country of ref document: EP

Kind code of ref document: A1