CN110289636B

CN110289636B - Direct-drive double-fed wind generating set based on frequency division/low-frequency power grid operation

Info

Publication number: CN110289636B
Application number: CN201910572638.5A
Authority: CN
Inventors: 成健; 刘世洪; 莫尔兵; 邓良; 郑大周; 胡开文; 王其君; 赵伟; 强喜臣; 梁臣; 曾东; 刘江华; 李�杰; 杨奎滨; 付斌
Original assignee: Dongfang Electric Wind Power Co Ltd
Current assignee: Dongfang Electric Wind Power Co Ltd
Priority date: 2019-06-28
Filing date: 2019-06-28
Publication date: 2022-07-19
Anticipated expiration: 2039-06-28
Also published as: CN110289636A

Abstract

The invention discloses a direct-drive double-fed wind generating set based on frequency division/low-frequency power grid operation, wherein a wind wheel of the direct-drive double-fed wind generating set is directly connected with a main shaft and a generator thereof, the voltage of a first stator winding loop of the generator adopts medium voltage or high voltage and is directly provided by a frequency division/low-frequency power grid, the voltage of the first rotor winding loop is provided by a machine side converter through a slip ring system or a slip ring-free electromagnetic induction system, and the direct-drive double-fed wind generating set is double-fed power supply; the rated voltage of the first rotor winding loop and the converter adopts medium voltage or low voltage, the bus rated voltage of the rotor loop adopts medium voltage or low voltage to be indirectly or directly connected to a network point on the frequency division/low frequency power grid, and the output active power of the first rotor winding loop is directly connected to the frequency division/low frequency power grid after being converged with the output active power of the first rotor winding loop. The invention can improve the cost performance and economic benefit of offshore and onshore wind turbine generators.

Description

Direct-drive double-fed wind generating set based on frequency division/low-frequency power grid operation

Technical Field

The invention relates to a direct-drive double-fed wind generating set based on frequency division/low-frequency power grid operation, and belongs to the technical field of wind power generation.

Background

Wind energy is a very important energy source in China as a clean renewable energy source. At present, the capacity of a single machine of offshore and onshore wind power access power grid is larger and larger, and the power transmission distance can be extended to medium and long distances.

Disclosure of Invention

Aiming at the problem that long-distance power transmission is carried out in an offshore wind generating set to a shore or in an onshore wind generating set to a load center, in order to reduce the impedance of a line and improve the power transmission capacity, 50/3 Hz-50/6 Hz frequency division/low frequency power grid power transmission can be adopted, the power generation power of the wind generating set is collected, and after boosting and medium-and-long distance alternating current power transmission, back-to-back or rectification, direct current power transmission and inversion are carried out to obtain a conventional 50Hz public power grid power frequency power supply. Therefore, a direct-drive double-fed wind generating set based on frequency division/low-frequency power grid operation is provided.

The purpose of the invention is realized by the following technical scheme:

a direct-drive double-fed wind generating set based on frequency division/low-frequency power grid operation comprises a direct-drive double-fed wind driven generator, a current transformer and a grid point on a frequency division/low-frequency power grid of the wind generating set and the frequency division/low-frequency power grid, wherein the rated frequency of the frequency division/low-frequency power grid is 50/3 Hz-50/6 Hz; the wind wheel of the direct-drive double-fed wind generating set is directly connected with a main shaft and a generator without a gear box, the voltage of a first stator winding loop of the generator adopts medium voltage or high voltage and is directly provided by a frequency division/low frequency power grid, the voltage of the first rotor winding loop is provided by a machine side converter through a slip ring system or a slip ring-free electromagnetic induction system, and the direct-drive double-fed wind generating set is supplied with power in a double-feed mode;

the rated voltage of a stator loop of the direct-drive double-fed wind generating set is indirectly or directly connected to a network point on a frequency division/low-frequency power grid by adopting medium voltage or high voltage; the rated voltage of the first rotor winding loop and the converter adopts medium voltage or low voltage, the bus rated voltage of the rotor loop adopts medium voltage or low voltage to be indirectly or directly connected to a network point on the frequency division/low frequency power grid, and the active power output by the first rotor winding loop is merged with the active power output and input by the first rotor winding loop and then is connected to the frequency division/low frequency power grid through a full-power step-up transformer.

The basic operation mode of the direct-drive double-fed wind generating set is a double-fed operation mode.

As a preferred mode, the first stator winding loop of the generator is accessed to a frequency division/low-frequency power grid by adopting a full-power step-up transformer or is accessed to a network point on the frequency division/low-frequency power grid by adopting a medium-high voltage direct distribution mode, and the full-power step-up transformer is not needed.

Preferably, the cooling of the direct-drive doubly-fed generator is operated by adopting a conventional air-to-air cooling mode or an air-to-water cooling mode or is operated by adopting high-temperature superconducting (HTS) cooling of the direct-drive doubly-fed wind generator.

As a preferred mode, a generator stator loop is directly or indirectly connected with a frequency division/low-frequency power grid upper net point, the output and input active power of a generator rotor loop is directly or indirectly connected with the frequency division/low-frequency power grid upper net point through a converter, and a short-circuit switch is arranged on the stator loop; the first operation mode of the direct-drive double-fed wind generating set comprises the following two modes:

doubly-fed operating mode RM11: the short-circuit switch on the stator loop of the generator is switched off, the bus transfer switch is switched off, the grid-connected switch connected with the grid-connected point of the frequency division/low-frequency power grid on the stator loop is closed according to quasi-synchronization grid connection, the electric energy generated by the stator loop is directly or indirectly output to the grid-connected point of the frequency division/low-frequency power grid, and the electric energy generated by the rotor loop is directly or indirectly converged to the grid-connected point of the frequency division/low-frequency power grid through the converter;

in a squirrel-cage running mode RM12 of the full-power frequency converter, a grid-connected switch between a stator loop and a grid point on a frequency division/low-frequency power grid is disconnected, a bus transfer switch is disconnected, a short-circuit switch on the stator loop is closed, and electric energy generated by a rotor loop is directly or indirectly connected to the grid point on the frequency division/low-frequency power grid through a converter.

As a preferable mode, the generator stator loop is directly or indirectly connected with a frequency division/low frequency power grid, the rated voltage of the generator stator loop adopts medium-high voltage, the generator rotor loop is directly or indirectly connected with a network access point of the frequency division/low frequency power grid through a converter, the rated voltage of the generator rotor loop adopts low-medium voltage and is lower than the rated voltage of the stator loop, the stator loop bus and the rotor loop bus are provided with a 'bus conversion switch', the first stator winding loop of the generator can be connected to the stator loop bus, or the first stator winding loop of the generator is connected to the rotor loop bus, and the conversion mode is reversible; the second operation mode of the direct-drive double-fed wind generating set comprises the following two specific modes:

doubly-fed bus conversion mode RM 21: the short-circuit switch on the stator loop is disconnected, the 'bus transfer switch' is switched to be inactive, the first stator winding loop of the generator is separated from the rotor loop bus, and the first stator winding and the stator loop bus are directly or indirectly connected with the upper network point of the frequency division/low frequency power grid; the electric energy generated by the first rotor winding loop of the generator is output to a rotor loop bus through a slip ring system or a slip ring-free electromagnetic induction system, a machine side converter, a direct current link and a grid side converter, and is directly or indirectly connected with a frequency division/low frequency power grid network access point; the generator set runs in a double-fed mode, and the running region is in a super-synchronous region and a partial sub-synchronous region;

doubly-fed bus conversion mode RM 22: the short-circuit switch on the stator loop is disconnected, the first stator winding loop of the generator is switched by the bus transfer switch, and the first stator winding loop is disconnected with the stator loop bus and connected with the rotor loop bus; the first rotor winding loop outputs active power through a slip ring system or a slip ring-free electromagnetic induction system, the active power is output to a rotor loop bus through frequency conversion of a machine side converter, a direct current link and a grid side converter, the active power output by the first rotor winding loop is converged with the active power output by a first stator winding loop of a generator, and the active power output by the direct-drive double-fed wind generating set is directly or indirectly connected with a frequency division/low-frequency power grid network access point; the generator set operates in a double-fed mode, and the operation region is in a sub-synchronous region.

As a preferred mode, the generator stator loop is directly connected with a frequency division/low frequency power grid, the generator rotor loop is connected with the frequency division/low frequency power grid through a converter, and a triangular winding/star winding conversion system is arranged on the first stator winding loop; the third operation mode of the direct-drive double-fed wind generating set comprises the following two specific modes:

doubly-fed stator delta winding mode of operation RM 31: before the unit is operated in a super-synchronous mode, the star winding loop of the stator is recovered to the triangular winding loop of the stator to operate through the up-conversion system on the first stator winding loop, electric energy generated by the stator loop is connected with the upper mesh point of the frequency division/low-frequency power grid, and electric energy generated by the rotor loop is converted and output to the upper mesh point of the frequency division/low-frequency power grid through the converter;

doubly-fed stator star winding mode of operation RM 32: the operation of the triangular winding loop of the stator is converted into the operation of the star winding loop of the stator by the up-conversion system of the winding loop of the first stator, the electric energy generated by the stator loop is connected with the upper net point of the frequency division/low frequency power grid, and the electric energy generated by the rotor loop is converted and output to the upper net point of the frequency division/low frequency power grid through the converter.

As a preferred mode, a first rotor winding of the generator is a low-voltage or medium-voltage winding, the rated voltage of a corresponding rotor loop bus is low-voltage or medium-voltage, and the first rotor winding inputs and outputs electric energy through a slip ring system or a slip ring-free electromagnetic induction system; and the first rotor winding outgoing line loop is connected with the machine side converter.

As a preferred mode, a high-power UPS is connected to a rotor loop bus of the direct-drive double-fed wind generating set, and the UPS converts the power frequency 50/3 Hz-50/6 Hz of the frequency division/low-frequency power grid into the power frequency 50Hz of the power frequency and then supplies power to general auxiliary electric equipment of the wind generating set, such as a main control system, a pitch control system, a cooling system of a converter and a generator, a yaw system and the like of the wind generating set.

As an optimal mode, the direct-drive double-fed wind generating set is connected with the rated frequency of a frequency division/low-frequency power grid50/3 Hz-50/6 Hz, and the rated voltage U of the stator loop_1nThe range is 0.69 KV-35 KV, and the rated voltage U of the rotor circuit bus_2nThe range is 0.69 KV-10 KV, and the capacity range of the generator set is 5 MW-50 MW.

The invention has the beneficial effects that:

the invention can improve the medium-voltage high-voltage network access of the stator electric loop of the large-capacity direct-drive double-fed wind generating set, and the rotor electric loop can adopt a medium-voltage or low-voltage converter; the rotor electrical circuit may or may not be boosted to the stator circuit by a transformer; the rotor electric loop can be coupled through other coils of the three-coil transformer or boosted to the high-voltage side of the boosting transformer and then connected into a frequency division/low-frequency power grid.

The direct-drive double-fed generator set adopts a frequency division/low frequency power grid for surfing the net, so that the problem of medium-distance and long-distance large-capacity power transmission on the sea and on the land is solved, the capacity of a surfing converter can be saved, and the capacity of the surfing converter can be further reduced after the rated slip adopts a small slip; meanwhile, the voltage grade of the first stator winding is greatly improved, and the cross section and the number of the stator loop cables are reduced; if the voltage grade of the rotor converter is reasonably improved, the cross section and the number of cables of a rotor loop can be further reduced; the reasonable rotor voltage grade and the access power grid mode can further increase the wide voltage and wide frequency range operation of the direct-drive double-fed generator set, and the high voltage ride through, low voltage ride through and zero voltage ride through capabilities; in addition, the cost performance and economic benefit of the offshore wind turbine generator and the onshore wind turbine generator can be improved.

Drawings

FIG. 1 is an electrical system diagram of a full-power two-coil step-up transformer of a direct-drive double-fed wind generating set;

FIG. 2 is a schematic view of part A of FIG. 1;

FIG. 3 is a schematic view of part B of FIG. 1;

FIG. 4 is a schematic view of section C of FIG. 1;

FIG. 5 is an electrical system diagram of a full-power three-coil step-up transformer of the direct-drive doubly-fed wind turbine generator system;

FIG. 6 is a schematic view of section D of FIG. 5;

FIG. 7 is a schematic view of section E of FIG. 5;

FIG. 8 is a schematic view of section F of FIG. 5;

FIG. 9 is a system diagram of a brush direct-drive doubly-fed wind generator and an electromagnetic power input/output slip ring of a generator rotor;

FIG. 10 is a diagram of a brushless direct-drive doubly-fed wind generator and a generator rotor electromagnetic power input/output slip-ring-free electromagnetic induction system;

in the drawings 1-10, a 1-wind wheel, a 2-main shaft, a 3-direct-drive doubly-fed generator, a 4-machine side converter (GSC), a 5-direct-current link (DL), a 6-grid side converter (LSC) and a 7-grid side converter contactor (C)₁) 8-breaker (K)₈) 9-stator-circuit grid-connected switch (C)₂₂) 10-breaker (K)₂) 11-breaker (K)₃) 12-breaker (K)₄) 13-first auxiliary transformer, 14-first auxiliary transformer outgoing line breaker (K)₅) 15-high power (UPS) incoming line breaker (K)₆) 16-high power three-phase Uninterrupted Power Supply (UPS), 17-high power (UPS) outlet circuit breaker (K)₇) 18-second auxiliary transformer, 19-stator delta and star switching system, 20-stator outlet star short-circuit switch (C)₂₃) 21- "bus bar changeover switch" (C)₂₁) 22-rotor loop bus step-up transformer, 23-full power two-coil step-up transformer, 24-full power three-coil step-up transformer, 25-main breaker (K)₁) 26-frequency division/low-frequency grid, 27-wind turbine frequency division/low-frequency grid upper network point (LP)₁) 28-full power three coil step-up transformer coil 2 (medium voltage side) or full power two coil step-up transformer coil 2 (medium voltage side), 29-rotor loop bus, 30-wind turbine frequency division/Low frequency grid upper network node (LP)₂) 31-stator loop bus, 32-machine side converter outgoing line, 33-network side converter outgoing line, 34-slip ring system, 35-no slip ring electromagnetic induction system, 36-stator electromagnetic power output system, 37-brushed direct-drive doubly-fed generator, 38-brushless direct-drive doubly-fed generator, 41-carbon brush, 42-slip ring, 51-first stator winding, 52-first rotor winding, 61-second stator winding and 62-second rotor winding.

Detailed Description

The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following.

For the purpose of clearly illustrating the technical solution of the present invention, the principle description is now made with reference to the accompanying drawings: in FIG. 1, 30-wind turbine frequency division/Low frequency grid upper node (LP)₂) (ii) a When the rated voltage U of the stator loop bus 31_1nEqual to the rated voltage U of the rotor loop bus 29_2nTime, "bus bar changeover switch" (C)₂₁)21 and rotor circuit bus step-up transformer 22 do not participate in the following options.

Firstly, the stator triangle and star switching system 19 is selected, and then the stator outgoing line star short-circuit switch (C) can not be selected₂₃)20 and "bus bar switch" (C)₂₁)21. The slip ring system 34 (carbon brush 41, slip ring 42) or the slip ring-free electromagnetic induction system 35 is selected. Alternatively, a rotor circuit bus step-up transformer 22 may be used.

② selecting a star-shaped short-circuit switch (C) for stator outgoing line₂₃)20, the stator delta and star switching system 19 cannot be selected; the slip ring system 34 (carbon brush 41, slip ring 42) or the slip ring-free electromagnetic induction system 35 is selected. In addition, the bus transfer switch can be singly or doubly selected (C)₂₁)21 and a rotor circuit bus bar step-up transformer 22.

③ selecting a bus transfer switch (C)₂₁)21, the sub-triangle and star conversion system 19 cannot be selected; the slip ring system 34 (carbon brush 41, slip ring 42) or the slip ring-free electromagnetic induction system 35 is selected. In addition, the star-shaped short-circuit switch (C) can singly select or doubly select the stator outgoing line₂₃)20 and a rotor circuit bus step-up transformer 22.

The slip ring system 34 (the carbon brushes 41 and the slip rings 42) or the slip ring-free electromagnetic induction system 35 can only be selected.

'bus change-over switch' (C)₂₁)21 and stator circuit grid-connected switch (C)₂₂)9 are mutually mechanically interlocked and electrically interlocked, and the working positions are respectively from '1' to '0' to '1'; wherein: the working position is '1', the stator loop is a grid-connected switch (C)₂₂)9 closed position, "bus bar switch" (C)₂₁)21 is the off position; the working position is '0', and the stator loop is a grid-connected switch (C)₂₂)9 off position, "bus bar switch" (C)₂₁)21 is the off position; the working position is '-1', the stator loop is connected with the grid switch (C)₂₂)9 off position, "bus bar switch" (C)₂₁)21 is the closed position;

a stator outlet star-shaped short-circuit switch (C) is selected₂₃)20 and "bus bar switch" (C)₂₁)21, stator outlet star short-circuit switch (C)₂₃) The double-feed operation mode RM11 in 20 can be the same as a bus bar switch (C)₂₁) Bus bar conversion mode RM21 for doubly fed operation in 21.

In FIG. 5, when the stator loop bus 31 is rated at the voltage U_1nEqual to the rated voltage U of the rotor loop bus 29_2nTime, "bus bar changeover switch" (C)₂₁)21 and the full power three coil step-up transformer 24 do not participate in the following options.

Firstly, the stator triangle and star switching system 19 is selected, and then the stator outgoing line star short-circuit switch (C) can not be selected₂₃)20 and "bus bar switch" (C)₂₁)21. The slip ring system 34 (carbon brush 41, slip ring 42) or the slip ring-free electromagnetic induction system 35 is selected.

② selecting a star-shaped short-circuit switch (C) for stator outgoing line₂₃)20, the stator delta and star switching system 19 cannot be selected; the slip ring system 34 (carbon brush 41, slip ring 42) or the slip ring-free electromagnetic induction system 35 is selected.

③ selecting a bus transfer switch (C)₂₁)21, the stator delta and star switching system 19 cannot be selected; the slip ring system 34 (carbon brush 41, slip ring 42) or the slip ring-free electromagnetic induction system 35 is selected. Stator outgoing line star-shaped short-circuit switch (C) can be selected₂₃)20。

And fourthly, only one of the slip ring system 34 (the carbon brush 41 and the slip ring 42) and the slip ring-free electromagnetic induction system 35 can be selected.

'bus transfer switch' (C)₂₁)21 and stator circuit grid-connected switch (C)₂₂)9 are mutually mechanically interlocked and electrically interlocked, and the working positions are respectively from '1' to '0' to '1'; wherein: the working position is '1', the stator loop is a grid-connected switch (C)₂₂)9 closed position, "bus bar switch" ("bus bar transfer switch") (C₂₁)21 is the off position; the working position is '0', and the stator loop is a grid-connected switch (C)₂₂)9 off position, "bus bar switch" (C)₂₁)21 is the off position; the working position is '-1', the stator loop is connected with the grid switch (C)₂₂)9 off position, "bus bar switch" (C)₂₁)21 is the closed position;

a stator outlet star-shaped short-circuit switch (C) is selected₂₃)20 and "bus bar switch" (C)₂₁)21, stator outlet star short-circuit switch (C)₂₃) The doubly-fed mode of operation RM11 in 20 may be the same as a "bus bar switch" (C)₂₁) Bus conversion mode RM21 for doubly fed operation in 21.

The wind wheel 1 (comprising blades and a rotating wheel) of the direct-drive double-fed wind generating set is directly connected with the main shaft 2 and the direct-drive double-fed generator 3 in a direct-drive manner, and a mechanical transmission chain is not provided with any primary main transmission gear box; the loop voltage of a first stator winding loop of the generator is provided by a frequency division/low frequency power grid, the loop voltage of a non-slip ring electromagnetic induction system 35 of the first rotor winding 52, a slip ring system 34 or the first rotor winding 52, a second rotor winding 62 and a second stator winding 61 of the generator is provided by a machine side converter outgoing line 32, a machine side converter (GSC)4, a direct current link (DL)5, a net side converter (LSC)6 and a net side converter outgoing line 33, the double-fed power supply is realized, and the active power output and input by the first rotor winding 52 or the second rotor winding 62 loop is directly or indirectly converged with the active power output by a converter and a first stator winding 51 loop, and then is respectively directly or indirectly converged with a wind turbine generator frequency division/low frequency power grid upper mesh point (LP)₁)27 or (LP)₂)30 connection; the basic operation mode of the direct-drive double-fed wind generating set is a double-fed operation mode.

The direct-drive double-fed wind generating set of the invention is connected with a frequency division/low frequency power grid 26 rated frequency f_n＝f_11nThe rated voltage U of the bus 31 of the stator loop of the direct-drive doubly-fed generator 3 is 50/3 Hz-50/6 Hz_1nSum voltage U₁＝(0.9～1.1)U_1nRotor circuit bus 29 rated voltage U_2nSum voltage U₂＝(0.9～1.1)U_2n(ii) a Mechanical rotation synchronous speed n of rotor of direct-drive doubly-fed generator 3_11n＝60f_11n/p_n(y 1); frequency division/low frequency power grid 26, stator loop bus 31 and rotor loop bus 29 of direct-drive doubly-fed generator 3_1yn＝f_nUnder (y) Hz (y is 0.9-1.1), the direct-drive doubly-fed generator 3 rotor synchronous speed n_1yn＝60f_1yn/p_n(y is 0.9 to 1.1); the mechanical rotating speed of a rotor of the direct-drive doubly-fed generator 3 is equal to the mechanical rotating speed of a main shaft 2 and a wind wheel (including blades and a rotating wheel) 1 of the generator set:

the rotor air gap electromagnetic field rotating speed of the direct-drive doubly-fed generator 3 is equal to the equivalent mechanical rotating speed of the first rotor winding 52 or the second rotor winding 62 loop relative to the rotor rotating speed:

current operating frequency of first rotor winding 52 or second rotor winding 62

Mechanical speed equivalent electrical working frequency of rotor

Operating frequency f_1ynLower, rotor speed

Slip of the lower part

Direct-drive double-fed generator 3 air gap active power P_e ^+/0/-The active power output by the stator is approximately equal to the active power of the stator air gap

Rotor output active power approximately equals rotor air gap active power

The direct-drive double-fed wind generating set has super-synchronous operation, synchronous operation and sub-synchronous operation modes. Wherein:

1. the direct-drive doubly-fed generator 3 works in a doubly-fed super-synchronous dynamic running state, and the synchronous rotating speed of a rotor is less than the mechanical rotating speed of the rotor

(+ is supersynchronous), rotor slip

Rotor current frequency

1) Active power of first stator winding 51 loop of direct-drive doubly-fed generator 3

Active power is output by the air gap electromagnetic field of the direct-drive doubly-fed generator 3 through the first stator winding 51, wherein in the figure 1, the first stator winding 51 outputs the active power

Voltage U via stator loop bus 31₁And a stator circuit grid-connected switch (C)₂₂)9 to wind turbine frequency division/low frequency grid upper network (LP)₂)30. In fig. 5, the first stator winding 51 outputs active power

Voltage U via stator loop bus 31₁And a stator loop grid-connected switch (C)₂₂)9 and breaker (K)₂)10 and a full-power three-coil step-up transformer 24, coil 2 (medium voltage side), coil 1 (high voltage side) to the upper network point (LP) of the frequency division/low frequency power grid of the wind turbine generator₁)27。

2) Active power of the first rotor winding 52 or the second rotor winding 62 loop of the direct-drive doubly-fed generator 3

Wherein: in FIG. 1, the active power of the first rotor winding 52 or the second rotor winding 62 loop of the direct-drive doubly-fed generator 3

Through an air gap electromagnetic field of the direct-drive doubly-fed generator 3, the first rotor winding 52 and the slip ring system 34 or the first rotor winding 52 and the slip ring-free electromagnetic induction system 35, the direct current passes through a machine side converter outgoing line 32, a machine side converter (GSC)4, a direct current link (DL)5, a grid side converter (LSC)6, a grid side converter outgoing line 33 and a grid side converter contactor (C)₁)7 and breaker (K)₈)8, connected to the rotor circuit bus 29, and/or the rotor circuit bus step-up transformer 22, minus converter losses

And offsetting a part of the power consumed by the electric circuit for the auxiliary machine

Or further reducing the loss part of the boost transformer 22 of the rotor loop bus

And a stator loop grid-connected switch (C) of the direct-drive doubly-fed generator 3₂₂)9 and a full power two-coil step-up transformer 23, coil 2 and a circuit breaker (K)₂) Grid point (LP) on frequency division/low frequency power grid of wind turbine generator system between 10₂)30, active power is in loop with the first stator winding 51

The active power at the coil 2 of the full-power two-coil transformer 23 is converged and on the network

(or

)

In FIG. 5, the rotor loop active power of the direct-drive doubly-fed generator 3

Through an air gap electromagnetic field of the direct-drive doubly-fed generator 3, the first rotor winding 52 and the slip ring system 34 or the first rotor winding 52 and the slip ring-free electromagnetic induction system 35, through a machine side converter outgoing line 32, a machine side converter (GSC)4, a direct current link (DL)5, a grid side converter (LSC)6 and a grid side converter outgoing line 33, a grid side converter contactor (C)₁)7 and breaker (K)₈)8, connected to the rotor circuit bus 29, minus the loss

Then, part of the power consumption of the electric loop for auxiliary machine is offset

The active power at the coil 3 (low voltage side) of the full-power three-coil step-up transformer 24 is

And the first stator winding 51 loop active power

The power is connected into a coil 2 (medium voltage side) of a full-power three-coil boosting transformer 24, and after the power is electromagnetically coupled with the coil 2 and the coil 3 and is boosted through a coil 1, the loss of the full-power three-coil boosting transformer 24 is reduced

Direct-drive double-fed wind generating set to wind generating set frequency division/low frequency grid upper mesh point (LP)₁)27 has an active power of

The air gap electromagnetic field of the direct-drive doubly-fed generator 3 passes through the first rotor winding 52 and the slip ring system 34 or the first rotor winding 52 and the electromagnetic induction without slip ringThe system 35 generates active power through the machine side converter outgoing line 32, the machine side converter (GSC)4, the direct current link (DL)5, the grid side converter (LSC)6 and the grid side converter outgoing line 33, and finally generates active power at the wind turbine generator frequency division/low frequency grid upper net point (LP)₁)27 or (LP)₂)30, converging; meanwhile, according to the control requirement, on one hand, the direct-drive doubly-fed generator 3 air gap electromagnetic field excitation inductive reactive power induction is provided to establish the stator voltage U₁On the other hand, the frequency division/low frequency network upper net point (LP) of the wind turbine generator set can be fed through the first stator winding 51 loop through the air gap electromagnetic field of the direct-drive doubly-fed generator 3₁)27 or (LP)₂)30 sends out capacitive or inductive reactive power, and simultaneously sends out capacitive or inductive reactive power to a machine side converter (GSC)4 through a first rotor winding 52 and a slip ring system 34 or a first rotor winding 52 and a slip ring-free electromagnetic induction system 35 and a machine side converter outlet wire 32; and the working frequency of the rotor loop is ensured to be

2. The direct-drive doubly-fed generator 3 works in a synchronous dynamic running state, and the rotor rotating speed is equal to the rotor synchronous rotating speed

(0 is synchronization), rotor slip

Rotor current frequency of

Through the air gap electromagnetic field of the direct-drive doubly-fed generator 3, active power is output through the first stator winding 51, wherein: in fig. 1, the first stator winding 51 of the direct-drive doubly-fed generator 3 outputs active power

Voltage U via stator loop bus 31₁Stator loop grid-connected switch (C)₂₂)9 to wind turbine frequency division/low frequency grid upper network (LP)₂)30. In fig. 5, the first stator winding 51 outputs active power

Voltage U via stator loop bus 31₁Stator circuit grid-connected switch (C)₂₂)9 and breaker (K)₂)10, 24 coils 2 (medium voltage side) and 1 (high voltage side) of full-power three-coil step-up transformer to the upper network point (LP) of frequency division/low frequency power grid of wind turbine generator set₁)27。

2) Active power of the first rotor winding 52 or the second rotor winding 62 of the direct-drive doubly-fed generator 3

The direct-drive doubly-fed generator 3 does not output or input active power to the first rotor winding 52 or the second rotor winding 62 through an electromagnetic field air gap; wherein: in FIG. 1, the rotor loop active power of the direct-drive doubly-fed generator 3

Not through the direct drive doubly fed generator 3 air gap electromagnetic field, the first rotor winding 52 and the slip ring system 34 or the first rotor winding 52 and the slip ring-free electromagnetic induction system 35; but with little loss of active power through the machine side converter outgoing line 32, the machine side converter (GSC)4, the direct current link (DL)5, the grid side converter (LSC)6, the grid side converter outgoing line 33 and the grid side converter contactor (C)₁)7 and breaker (K)₈)8, the output and input active power of the step-up transformer 22 connected to the rotor circuit bus 29 or the rotor circuit bus is zero, and the loss part of the converter is reduced

Or plus the loss part of the rotor loop bus bar step-up transformer 22

And a stator loop grid-connected switch (C) of the direct-drive doubly-fed generator 3₂₂)9 and a full power two-coil step-up transformer 23, coil 2 and a circuit breaker (K)₂) Grid point on frequency division/low frequency power grid (LP) of wind turbine generator between 10₂)30, active power of stator loop

Converge to active power at coils 2 of a full power two coil step-up transformer 23

(or

)

(or

)

Not through the direct drive doubly fed generator 3 air gap electromagnetic field, the first rotor winding 52 and the slip ring system 34 or the first rotor winding 52 and the slip ring-free electromagnetic induction system 35; but with little loss active power, through the machine side converter outgoing line 32, the machine side converter (GSC)4, the direct current link (DL)5, the grid side converter (LSC)6 and the grid side converter outgoing line 33, the grid side converter contactor (C)₁)₇And a circuit breaker (K)₈)8, connected to the rotor circuit bus 29, minus the loss

Then part of consumed power of electric loop for auxiliary machine is offset

Active power in coil 24, coil 3 (low voltage side) of full-power three-coil step-up transformer

And active power of the stator loop

Switching in a coil 2 (medium voltage side) of a full-power three-coil step-up transformer 24, coupling the coil 2 and a coil 3 through the full-power three-coil step-up transformer 24 and boosting through a coil 1, and subtracting the loss of the full-power three-coil step-up transformer 24

Direct-drive double-fed wind generating set to wind generating set frequency division/low frequency grid upper network node (LP)₁)27 has an active power of

Grid point (LP) of direct-drive doubly-fed generator 3 from wind turbine generator frequency division/low-frequency power grid₁)27 or (LP)₂)30, through a machine side converter outgoing line 32, a machine side converter (GSC)4, a direct current link (DL)5, a grid side converter (LSC)6, a grid side converter outgoing line 33, a first rotor winding 52, a slip ring system 34 or a first rotor winding 52 and a loop without a slip ring electromagnetic induction system 35, providing exciting inductive reactive power for an air gap electromagnetic field of the direct-drive double-fed generator 3 to induce and establish a stator voltage U₁No input and output of active power, and the working frequency of the rotor loop is ensured to be

3. Direct-drive double-fed hairThe motor 3 works in a double-fed subsynchronous dynamic running state, and the synchronous rotating speed of the rotor is greater than the mechanical rotating speed of the rotor

(-subsynchronous), rotor slip

Rotor (current) frequency

Active power is output by a direct-drive doubly-fed generator 3 air gap electromagnetic field through a first stator winding 51, wherein in the figure 1, the first stator winding 51 outputs the active power

Voltage U via stator loop bus 31₁Through a stator circuit grid-connected switch (C)₂₂)9 to wind turbine frequency division/low frequency grid upper network (LP)₂)30. In fig. 5, the first stator winding 51 outputs active power

Voltage U via stator loop bus 31₁And a stator circuit grid-connected switch (C)₂₂)9 and breaker (K)₂)10, 24 coils 2 (medium voltage side) and 1 (high voltage side) of full-power three-coil step-up transformer to the upper network point (LP) of frequency division/low frequency power grid of wind turbine generator set₁)27。

Through an air gap electromagnetic field, the first rotor winding 52 and the slip ring system 34 or the first rotor winding 52 and the slip ring-free electromagnetic induction system 35, through a machine side converter outgoing line 32, a machine side converter (GSC)4, a direct current link (DL)5, a grid side converter (LSC)6 and a grid side converter outgoing line 33, through a grid side converter contactor (C)₁)7 and breaker (K)₈)8, connected to the rotor circuit bus 29, or the rotor circuit bus step-up transformer 22, minus the converter loss

And offsetting a portion of the power consumed by the auxiliary electric circuit

Or re-adding the loss part of the transformer 22

In the direct-drive doubly-fed generator 3 stator loop grid-connected switch (C)₂₂)9 and a full power two coil step-up transformer coil 2 (medium voltage side) 28 and a circuit breaker (K)₂) Grid point on frequency division/low frequency power grid (LP) of wind turbine generator between 10₂)30, active power is in loop with the first stator winding 51

Converge to have active power at coil 2 of full power two-coil step-up transformer 23

(or

)

In FIG. 5, the active power of the first rotor winding 52 or the second rotor winding 62 loop of the direct-drive doubly-fed generator 3

Through an air gap electromagnetic field of the direct-drive doubly-fed generator 3, the first rotor winding 52 and the slip ring system 34 or the first rotor winding 52 and the slip ring-free electromagnetic induction system 35, through a machine side converter outgoing line 32, a machine side converter (GSC)4, a direct current link (DL)5, a grid side converter (LSC)6 and a grid side converter outgoing line 33, through a grid side converter contactor (C)₁)7 and breaker (K)₈)8, connected to the rotor circuit bus 29, minus the loss

In the full-power three-coil step-up transformer 24, the coil 3 (low-voltage side) has active power of

And the active power of the stator loop

The full power three coil step-up transformer coil 2 (medium voltage side) 28 is switched in, the coil 2 and the coil 3 are coupled through the full power three coil step-up transformer 24 and the voltage is boosted through the coil 1, and then the loss of the full power three coil step-up transformer 24 is subtracted

Grid point (LP) on frequency division/low frequency power grid of wind turbine generator set of direct-drive doubly-fed wind power direct-drive doubly-fed generator 3₁)27 or (LP)₂)30, active power is input through a machine side converter (GSC)4, a direct current link (DL)5 and a network side converter (LSC)6, and then the active power is input through a slip ring system 34 and a first rotor winding 52 or a slip ring-free electromagnetic induction system 35, the first rotor winding 52 provides active power for an air gap electromagnetic field of the direct-drive doubly-fed generator 3; meanwhile, according to the control requirement, on one hand, a direct-drive double-fed generator 3 air gap electromagnetic field excitation inductive reactive power induction is provided to establish stator voltage U₁On the other hand, the frequency division/low frequency grid upper mesh point (LP) of the wind turbine generator set can be fed back through the first stator winding 51 loop through the air gap electromagnetic field of the direct-drive doubly-fed generator 3₁)27 or (LP)₂)30, and simultaneously sends out capacitive or inductive reactive power to a machine side converter (GSC)4 through a first rotor winding 52 and a slip ring system 34 or a first rotor winding 52 slip ring-free electromagnetic induction system 35; and the working frequency of the rotor loop is ensured to be

The electric system of the direct-drive double-fed wind generating set can adopt the following operation scheme:

1) when the rotor loop bus 29 is rated with the voltage U_2nLess than the rated voltage U of the stator loop bus 31_1nThere are sometimes 3 schemes for the purpose of,

scheme 1: in fig. 1, active power is output and input from a machine side converter (GSC)4, a direct current link (DL)5 and a grid side converter (LSC)6 to a first rotor winding 52 through a slip ring system 34 or a slip ring-free electromagnetic induction system 35

Outputs active power with the first stator winding 51

The voltage of the wind turbine generator is boosted by a rotor loop bus booster transformer 22 and then is transmitted to a network point (LP) on a frequency division/low frequency power grid of the wind turbine generator₂)30, then through a wind-powered electricity generation unit full-power two-coil step-up transformer 23 to a higher voltage level, through a main circuit breaker (K)₁)25 into a frequency division/low frequency grid 26;

scheme 2: in FIG. 1, the first rotor winding 52 is machine-side switched via slip ring system 34 or slip ring-less electromagnetic induction system 35The output and input active power of a current device (GSC)4, a direct current link (DL)5 and a network side converter (LSC)6

Active power output from the first stator winding 51

The voltage of the wind turbine generator is boosted by a rotor loop bus booster transformer 22 and then is transmitted to a network point (LP) on a frequency division/low frequency power grid of the wind turbine generator₂)30 meet, when the rated voltage U of the stator loop bus 31_1nWhen a very high voltage grade is selected, the rated power transmission distance of the direct-drive double-fed wind turbine generator is very long, the power transmission line network of the frequency division/low frequency power grid 26 is suitable for the condition that the full-power two-coil step-up transformer 23 of the wind turbine generator is not needed, and finally, the direct-drive double-fed generator 3 adopts a high-voltage direct-matching mode and passes through a main circuit breaker (K)₁)25 directly into the frequency division/low frequency grid 26;

scheme 3: in fig. 5, the first rotor winding 52 or the second rotor winding 62 outputs and inputs active power

Outputs active power with the first stator winding 51

The high-voltage power generation system directly passes through a coil 3 (low-voltage side) and a coil 2 (medium-voltage side) of a full-power three-coil step-up transformer 24 of the wind turbine generator respectively, and the two are boosted to a coil 1 (high-voltage side) of the full-power three-coil step-up transformer 24 through electromagnetic coupling and merged into a frequency division/low-frequency grid upper mesh point (LP) of the wind turbine generator₁)27 while passing through the main breaker (K)₁)25 sink into a frequency division/low frequency network 26.

2) When the rotor loop bus 29 is rated with the voltage U_2nEqual to rated voltage U of stator loop bus 31_1nThere are 2 schemes in time;

scheme 4: in fig. 1, active power output and input from the machine-side converter (GSC)4, the direct current link (DL)5 and the grid-side converter (LSC)6 are transmitted to the first rotor winding 52 through the slip ring system 34 or the slip ring-free electromagnetic induction system 35 through the machine-side converter (GSC)4, the direct current link (DL)5

Active power output from the first stator winding 51

The network point (LP) on the frequency division/low frequency power grid of the wind turbine generator set is directly realized without a rotor loop bus booster transformer 22₂)30, then the wind power generation set full power two-coil booster transformer 23 coil 2 (medium voltage side) is boosted to coil 1 (high voltage side) through a main circuit breaker (K)₁)25 into a frequency division/low frequency grid 26;

scheme 5: in fig. 1, the rotor circuit bus 29 has a rated voltage U_2nAnd the rated voltage U of the stator loop bus 31_1nThe direct-drive double-fed wind turbine generator system has the advantages that the direct-drive double-fed wind turbine generator system is equal in voltage grade and high in voltage grade, the transmission distance of rated power of the direct-drive double-fed wind turbine generator system is large, the frequency division/low-frequency power grid 26 power transmission line networking is suitable for the situation that a full-power two-coil booster transformer 23 of the wind turbine generator system is not needed and a rotor loop bus booster transformer 22 is not needed, active power is output and input from a machine side converter (GSC)4, a direct current link (DL)5 and a grid side converter (LSC)6 through a slip ring system 34 or a slip ring-free electromagnetic induction system 35 through a first rotor winding 52

Outputs active power with the first stator winding 51

Network point (LP) on frequency division/low frequency power grid of wind turbine generator₂)30, and finally, adopting a high-voltage direct distribution mode for the direct-drive double-fed wind generating set to pass through a main circuit breaker (K)₁)25 directly into the divided/low frequency grid 26.

In addition, through the network side converter outgoing line 33, the network side converter (LSC)6, the direct current link (DL)5, the machine side converter (GSC)4, the machine side converter outgoing line 32, the slip ring system 34 and the first rotor winding 52 or the slip ring-free electromagnetic induction system 35 and the first rotor winding 52, the converter controller can electrically adjust the air gap electromagnetic field of the direct-drive double-fed generator 3, and can adjust and fixThe sub-loop synchronization synchronous voltage phase sequence, amplitude, phase and dynamic adjustment direct-drive doubly-fed generator 3 air gap electromagnetic field rotation frequency and frequency division/low frequency power grid 26 frequency synchronization (constant frequency) and the direct-drive doubly-fed generator 3 stator loop voltage amplitude, stator loop input and output reactive power and rotor loop input and output reactive power, and the working frequency (variable frequency) of the first rotor winding 52 or the second rotor winding 62 loop is dynamically adjusted according to the direct-drive doubly-fed generator 3 air gap electromagnetic field rotation frequency and rotor mechanical rotation speed (variable speed) synchronous with the frequency division/low frequency power grid frequency (constant frequency), wherein the working frequency is the working frequency

In the direct-drive doubly-fed generator set of the present invention, from fig. 1 and fig. 5, the brush-type direct-drive doubly-fed generator 37 in fig. 9, including the stator electromagnetic power output system 36 (including the first stator winding 51 and the first rotor winding 52) and the slip ring system 34 (carbon brush 41, slip ring 42), or the brush-less direct-drive doubly-fed generator 38 in fig. 10, including the stator electromagnetic power output system 36 (including the first stator winding 51 and the first rotor winding 52) and the slip ring-free electromagnetic induction system 35 (the second stator winding 61, the second rotor winding 62), may be adopted for the rotor winding outgoing line of the direct-drive doubly-fed generator 3.

In the direct-drive double-fed wind generating set of the invention, in the figures 1 and 5, a rotor loop bus 29 has a rated voltage U_2nThe frequency division/low-frequency power grid 26 frequency is adopted to be 50/3 Hz-50/6 Hz, and the circuit breaker (K) is a main incoming line breaker of an auxiliary power loop of the direct-drive double-fed wind turbine generator (K)₄)12, supplying power to a first auxiliary transformer 13; after the voltage is reduced to 400V, the outgoing line breaker (K) is connected through a first auxiliary transformer₅)14, high power (UPS) incoming line breaker (K)₆)15, supplying power to a high-power three-phase Uninterruptible Power Supply (UPS)16, converting the frequency division/low frequency of 50/3 Hz-50/6 Hz into 50Hz power frequency voltage of 400V by the high-power three-phase UPS 16, and supplying power to a 400V auxiliary electric device commonly used by a wind turbine; the 50Hz power frequency voltage 400V of the high-power three-phase Uninterrupted Power Supply (UPS)16 supplies power to the second auxiliary transformer 18 through the high-power (UPS) outgoing line breaker (K7)17, and outputs 50Hz power frequency voltage 690V to the second auxiliary transformerThe wind turbine set 690V assists the power supply of the electric equipment.

The direct-drive double-fed generator 3 can also be operated by a high-temperature superconducting (HTS) cooling direct-drive double-fed generator besides a conventional air-to-air cooling or air-to-water cooling mode.

On the basis of the double-fed basic operation mode of the direct-drive double-fed wind generating set, a first operation mode, a second operation mode and a third operation mode are also provided:

1) the first operation mode of the direct-drive double-fed wind generating set comprises the following two specific modes:

full-power frequency converter squirrel-cage operation mode RM12 in the sub-synchronous region of double-fed operation of a generator set in the graph 1 and the graph 5, a stator loop bus 31 and a frequency division/low-frequency grid upper mesh point (LP) of the wind generator set are adopted₁)27 or (LP)₂) Stator circuit grid-connected switch (C) between 30₂₂)9 ("bus bar transfer switch" (C)₂₁)21) is disconnected, and the stator outlet star-shaped short circuit switch (C) on the stator loop bus 31₂₃)20, the generator set is closed, active power generated by squirrel-cage running of the full-power frequency converter of the generator set directly or indirectly is connected to upper mesh points (LP) of a frequency division/low frequency power grid of the wind generating set through an air-gap electromagnetic field, a loop of a first rotor winding 52 and a slip ring system 34 or a loop of the first rotor winding 52 and a slip ring-free electromagnetic induction system 35, a machine side converter outgoing line 32, a machine side converter (GSC)4, a direct current link (DL)5, a grid side converter (LSC)6 and a grid side converter outgoing line 33₁)27 or (LP)₂)30, of a nitrogen-containing gas; when the full-power frequency converter squirrel-cage power generation of the unit runs, the limit of slip or the range of rotating speed is avoided, and the limit of the rotor capacity, the converter capacity and the input mechanical power of the direct-drive double-fed generator 3 is only realized.

In the doubly-fed operation mode RM11, in the diagram 1, in the super-synchronous region and the partial sub-synchronous region of the doubly-fed operation of the unit, a bus transfer switch (C) is adopted₂₁)21 is disconnected, and a stator outgoing line star-shaped short circuit switch (C) on the stator loop bus 31₂₃)20 is disconnected, and the stator loop bus 31 and the wind turbine generator frequency division/low frequency grid upper mesh point (LP)₁)27 or (LP)₂) Stator circuit grid-connected switch (C) between 30₂₂)9 closed, circuit breaker (K)₂)10 closureThen connected to the full power two-coil step-up transformer coil 2 (medium voltage side) 28, the first rotor winding 52 or the second rotor winding 62 loop outputs active power, through the rotor loop bus 29 breaker (K)₃)11 and a rotor loop bus step-up transformer 22 are connected to a network point (LP) on a frequency division power grid of the wind turbine generator in a step-up mode₂) And 30, the active power is merged with the loop output active power of the first stator winding 51. In FIG. 5, in the super-synchronous region and the partial sub-synchronous region of the double-fed operation of the unit, a 'bus bar change-over switch' (C) is adopted₂₁)21 is disconnected, and the stator outgoing line star-shaped short circuit switch (C) on the stator loop bus 31₂₃)20 is disconnected, and the stator loop bus 31 and the wind turbine generator frequency division/low frequency grid upper mesh point (LP)₁)27 or (LP)₂) Stator circuit grid-connected switch (C) between 30₂₂)9 closed, circuit breaker (K)₂)10 is connected with a full-power three-coil step-up transformer coil 2 (medium voltage side) 28 after being closed, the first rotor winding 52 or the second rotor winding 62 outputs active power in a loop, and a circuit breaker (K) is connected through a rotor loop bus 29₃)11 is connected to a 24 coil 3 (low-voltage side) of a full-power three-coil booster transformer, and is electromagnetically coupled with active power output by a 51 loop of a first stator winding through a 24 coil 2 (medium-voltage side) of the full-power three-coil booster transformer, and is connected to an upper mesh point (LP) of a frequency division/low-frequency power grid of a wind turbine generator after being boosted to an outlet of a 24 coil 1 (high-voltage side) of the full-power three-coil booster transformer₁)27。

2) The second operation mode of the direct-drive double-fed wind generating set comprises the following two specific modes:

the invention relates to a direct-drive double-fed generator set, which is characterized in that when a stator loop bus 31 has a rated voltage U_1nGreater than the rated voltage U of the rotor loop bus 29_2nThen, a 'bus transfer switch' (C) is selected₂₁)21 on-line switching (reversible).

The unit operates according to a double-fed operation mode RM 22:

in the sub-synchronous double-fed operation region of the unit in fig. 1, the stator loop bus 31 is connected with the rotor loop bus 29, and the stator loop bus 31 passes through the stator loop grid-connected switch (C)₂₂)9 after disconnection, the voltage is switched to the 'bus bar change-over switch' (C)₂₁)21 closed and connected to a rotor circuit busbar 29, firstThe active power output from the loop of the stator winding 51 is merged with the active power input from the loop of the first rotor winding 52 or the second rotor winding 62, and then the merged power passes through a circuit breaker (K) of the rotor loop bus 29₃)11 and a rotor loop bus step-up transformer 22 are connected to the upper net point (LP) of a frequency division power grid of a wind turbine generator₂) And (6) 30 points.

In fig. 5, in the sub-synchronous doubly-fed operation region of the unit, the voltage U of the stator loop bus 31₁By means of a stator circuit grid-connected switch (C)₂₂)9 breaker (K)₂)10 after disconnection, through a "bus bar switch" (C)₂₁)21 is closed and connected with a rotor circuit bus 29, the output active power of a loop of the first stator winding 51 is merged with the input active power of a loop of the first rotor winding 52 or the second rotor winding 62, and then a circuit breaker (K) passes through the rotor circuit bus 29₃)11 is connected to a 24 coil 3 (low-voltage side) of a full-power three-coil booster transformer, and is connected to an upper mesh point (LP) of a frequency division/low-frequency power grid of a wind turbine generator after being boosted to an outlet of a 24 coil 1 (high-voltage side) of the full-power three-coil booster transformer after being electromagnetically coupled₁)27。

Reducing stator loop bus 31 voltage U₁The open-end voltage of the rotor of the generator is also reduced, and the low limit range of the low-speed area is improved.

The unit operates according to a double-fed operation mode RM 21:

in FIG. 1, before the unit is operated in super-synchronization, the stator loop bus 31 passes through a bus transfer switch (C)₂₁)21 disconnected from rotor circuit bus 29, and stator circuit bus 31 voltage U₁By means of a stator circuit grid-connection switch (C)₂₂)9 closed, circuit breaker (K)₂)10 are closed and connected to the full power two coil step-up transformer coil 2 (medium voltage side) 28, the first rotor winding 52 or the second rotor winding 62 loop outputs active power, the circuit breaker (K) via the rotor loop bus 29₃)11 and a rotor loop bus step-up transformer 22 are connected to a network point (LP) on a frequency division/low-frequency power grid of a wind turbine generator system in a step-up manner₂)30 points, the active power is merged with the active power output by the loop of the first stator winding 51;

in FIG. 5, before the unit is operated in super-synchronization, the voltage U of the stator loop bus 31₁By "bus-bar switches" (C)₂₁)21 disconnected from the rotor circuit bus 29 and the stator circuit bus 31 voltage U₁By means of a stator circuit grid-connection switch (C)₂₂)9 closed, circuit breaker (K)₂)10 is closed and connected with a full-power three-coil step-up transformer coil 2 (medium-voltage side) 28, active power is output in a loop of the first rotor winding 52 or the second rotor winding 62, and the active power passes through a breaker (K) of a rotor loop bus 29₃)11 is connected to a 24 coil 3 (low-voltage side) of a full-power three-coil booster transformer, and is electromagnetically coupled with active power output by a 51 loop of a first stator winding through a 24 coil 2 (medium-voltage side) of the full-power three-coil booster transformer, and is connected to a wind turbine generator frequency division/low-frequency grid upper mesh point (LP) after being boosted to a 24 coil 1 (high-voltage side) of the full-power three-coil booster transformer₁)27。

Increasing the voltage U of the stator loop bus 31₁The open-circuit voltage of the rotor of the generator is also improved, and the operation of the stator loop and the rotor loop at rated current and below is stabilized.

Wherein, the rated voltage U of the stator loop bus 31_1nRated voltage U of rotor loop bus 29_2nWith a certain voltage difference, normally U_1n/U_2nTaking 1.3-1.6.

3) The third operation mode of the direct-drive double-fed wind generating set comprises the following two specific modes:

the doubly-fed stator star winding operation mode RM32 is a direct-drive doubly-fed generator set of the invention, in the figures 1 and 5, in the sub-synchronous doubly-fed operation region of the generator set, namely a stator delta winding loop is (reversibly) converted into a stator star winding operation through a stator delta and star conversion system 19, and under the condition that the three-phase stator line voltage is unchanged, the voltage on each phase is reduced to be the voltage on each phase

I.e. the open circuit voltage will be the original

The lower limit range of the low speed area is increased.

The double-fed stator delta winding operation mode RM31 is a direct-drive double-fed generator set of the invention, shown in figure 1,In fig. 5, before the unit needs to operate in super-synchronization, the stator star winding loop returns to the stator delta winding loop (reversible) through the stator delta and star switching system 19 to operate, so that the open voltage of the generator rotor is increased, and the stator loop and the rotor loop are stabilized to operate at rated current or below. Wherein the ratio of rotor open voltage of the delta winding loop to rotor open voltage of the star winding loop

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, it should be noted that any modifications, equivalents and improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A direct-drive double-fed wind generating set based on frequency division/low-frequency power grid operation comprises a direct-drive double-fed wind driven generator, a current transformer and a wind generating set frequency division/low-frequency power grid upper mesh point and a frequency division/low-frequency power grid, wherein the rated frequency of the frequency division/low-frequency power grid is 50/3 Hz-50/6 Hz; the method is characterized in that: the wind wheel of the direct-drive double-fed wind generating set is directly connected with the main shaft and the generator without a gear box, the voltage of a first stator winding loop of the generator is directly provided by a frequency division/low-frequency power grid, the voltage of the first rotor winding loop is provided by a machine side converter through a slip ring system or a slip ring-free electromagnetic induction system, and the direct-drive double-fed wind generating set is doubly-fed;

the rated voltage of the first rotor winding loop and the converter adopts medium voltage or low voltage, the bus rated voltage of the rotor loop adopts medium voltage or low voltage to be indirectly or directly connected to a network point on the frequency division/low frequency power grid, and the active power output by the first rotor winding loop and the active power output and input by the first rotor winding loop are converged and then connected to the frequency division/low frequency power grid;

a first stator winding loop of the direct-drive double-fed wind driven generator is connected to a net point on a frequency division/low-frequency power grid by adopting medium-voltage or high-voltage direct distribution, and a full-power booster transformer is not needed.

2. The direct-drive doubly-fed wind generator set operating on a divided/low frequency grid as claimed in claim 1, wherein: the cooling of the direct-drive double-fed generator adopts a conventional air-to-air cooling or air-to-water cooling mode or adopts the high-temperature superconducting (HTS) cooling operation of the direct-drive double-fed wind driven generator.

3. The direct-drive doubly-fed wind generator set operating on a divided/low frequency grid as claimed in claim 1, wherein: the generator stator loop is directly connected with the frequency division/low-frequency power grid network access point, and the output and input active power of the generator rotor loop is directly or indirectly connected with the frequency division/low-frequency power grid network access point through the converter; the first operation mode of the direct-drive double-fed wind generating set comprises the following modes:

doubly-fed mode of operation RM11: a bus transfer switch on a stator loop of the generator is disconnected, a grid-connected switch connected with a grid-connected point of a frequency division/low-frequency power grid on the stator loop is closed according to quasi-synchronization grid connection, electric energy generated by the stator loop is directly output to the grid-connected point of the frequency division/low-frequency power grid, and electric energy generated by a rotor loop is directly or indirectly converged to the grid-connected point of the frequency division/low-frequency power grid through a converter.

4. The direct-drive doubly-fed wind generator set operating on a divided/low frequency grid as claimed in claim 1, wherein: the generator stator loop is directly connected with a frequency division/low-frequency power grid, the rated voltage of the generator stator loop adopts medium-high voltage, the generator rotor loop is directly or indirectly connected with a network access point of the frequency division/low-frequency power grid through a converter, the rated voltage of a generator rotor loop bus adopts low-medium voltage and is lower than the rated voltage of the stator loop, a bus change-over switch is arranged on a stator loop bus and a rotor loop bus, a first stator winding loop of the generator can be connected to the stator loop bus, or the first stator winding loop of the generator is connected to the rotor loop bus, and the change-over mode is reversible; the second operation mode of the direct-drive double-fed wind generating set comprises the following two specific modes:

doubly-fed bus conversion mode RM 21: the 'bus change-over switch' on the stator loop does not act, the first stator winding loop of the generator is separated from the rotor loop bus, and the first stator winding and the stator loop bus are directly connected with the upper network point of the frequency division/low frequency power grid; the electric energy generated by the first rotor winding loop of the generator is output to a rotor loop bus through a converter and is directly or indirectly connected with a frequency division/low-frequency power grid network access point; the generator set operates in a double-fed mode, and the operation area is in a super-synchronous area and a partial sub-synchronous area;

doubly-fed bus conversion mode RM 22: a first stator winding loop of the generator is switched by a bus transfer switch, and the first stator winding loop is disconnected with a stator loop bus and connected with a rotor loop bus; the active power output by the first rotor winding loop is converted and output to a rotor loop bus through a converter, the active power output by the first rotor winding loop is converged with the active power output by the first stator winding loop of the generator through a slip ring system or a slip ring-free electromagnetic induction system, and then the active power output by the direct-drive double-fed wind generating set is directly or indirectly connected with a frequency division/low-frequency power grid network access point; the generator set operates in a double-fed mode, and the operation area is in a sub-synchronous area.

5. The direct-drive doubly-fed wind generator set operating on a divided/low frequency grid as claimed in claim 1, wherein: the generator stator loop is directly connected with a frequency division/low-frequency power grid, the generator rotor loop is connected with the frequency division/low-frequency power grid through a converter, and a triangular winding/star winding conversion system is arranged on the first stator winding loop; the third operation mode of the direct-drive double-fed wind generating set comprises the following two specific modes:

6. A direct drive doubly fed wind generator set operating on a divided/low frequency grid as claimed in any one of claims 1 to 5 wherein: a high-power UPS is connected to a rotor loop bus of the direct-drive double-fed wind generating set, and after the UPS converts the power supply frequency of a frequency division/low-frequency power grid from 50/3Hz to 50/6Hz to the power supply frequency of 50Hz, the UPS supplies power to universal auxiliary electric equipment of the wind generating set, such as a main control system, a pitch system, a converter, a cooling system of a generator, a yaw system and the like of the wind generating set.

7. The direct-drive doubly-fed wind generator set operating on a divided/low frequency grid as claimed in any one of claims 1 to 5, wherein: the rated frequency of a connected frequency division/low-frequency power grid is 50/3 Hz-50/6 Hz, and the rated voltage U of a stator loop is_1nThe range is 0.69 KV-35 KV, and the rated voltage U of the rotor circuit bus_2nThe range is 0.69 KV-10 KV, and the capacity range of the generator set is 5 MW-50 MW.