CN216872860U - Doubly-fed asynchronous wind turbines and transmission systems for wind turbines - Google Patents

Abstract

The embodiment of the application provides double-fed asynchronous wind generating set and wind generating set's transmission of electricity system, and double-fed asynchronous wind generating set includes: a generator; the rotor-side converter is electrically connected with a rotor of the generator and used for adjusting the frequency of the alternating current output by the rotor to a target frequency, and the target frequency is less than 50 Hz; and the stator side converter is electrically connected with the stator of the generator and is used for adjusting the frequency of the alternating current output by the stator to a target frequency. The embodiment of the application can reduce the refitting cost or the design cost of the double-fed asynchronous wind generating set.

Description

Doubly-fed asynchronous wind turbines and transmission systems for wind turbines

technical field

The application belongs to the technical field of wind power generation, and in particular relates to a doubly-fed asynchronous wind generator set and a power transmission system for the wind generator set.

Background technique

With the rapid development of new energy technology, the application scope of new energy is getting wider and wider. Among them, wind power generation technology has become one of the key technologies.

In the process of wind power generation, wind turbines convert wind energy into electrical energy, and then integrate the electrical energy into the power grid through transmission lines. However, the inventors of the present application have found that the cost of power transmission and modification of the current wind turbine is relatively high.

Utility model content

The embodiments of the present application provide a doubly-fed asynchronous wind turbine generator set and a power transmission system for the wind turbine generator set, which can at least solve the technical problem of high retrofit cost of the wind turbine generator set.

In the first aspect, the embodiments of the present application provide a doubly-fed asynchronous wind power generator set, which includes: a generator; a rotor-side converter, the rotor-side converter is electrically connected to the rotor of the generator, and the In order to adjust the frequency of the alternating current output by the rotor to the target frequency, the target frequency is less than 50Hz; the stator side converter, the stator side converter is electrically connected with the stator of the generator, and is used to adjust the frequency of the alternating current output by the stator to the target frequency .

In a second aspect, an embodiment of the present application provides a power transmission system for a wind turbine. The power transmission system for a wind turbine includes: a doubly-fed asynchronous wind turbine, and the doubly-fed asynchronous wind turbine includes a generator and a rotor-side converter, The rotor-side converter is electrically connected to the rotor of the generator, and is used to adjust the frequency of the alternating current output by the rotor to the target frequency, and the target frequency is less than 50Hz; the first step-up transformer, the low-voltage side of the first step-up transformer is respectively connected to the generator. The stator and the rotor-side converter are electrically connected, and the high-voltage side of the first step-up transformer is electrically connected to the power grid; the first converter, the first converter is electrically connected between the stator and the power grid, and is used to convert the output voltage of the stator to the power grid. The frequency of the alternating current is adjusted to the target frequency.

In this way, in the embodiment of the present application, the frequency of the AC power output by the generator is adjusted to be less than 50 Hz through the rotor-side converter and the first converter. On the other hand, it can reduce the voltage drop of the transmission line in the power transmission system of the wind turbine, which helps to maintain the voltage stability of the power transmission system; on the other hand, it can reduce the loss of the transmission cable, Extend the life of transmission cables.

According to an embodiment of the second aspect of the present application, the first converter is electrically connected between the stator and the low voltage side of the first step-up transformer.

In this way, through the first converter between the stator of the generator and the low-voltage side of the first step-up transformer, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, and it is possible to generate electricity without the need for double-fed asynchronous wind power generation. In the case of redesigning the generators in the unit, the DFIG asynchronous wind turbine can be applied to the low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the DFIG.

According to any of the foregoing embodiments of the second aspect of the present application, the input end of the rotor-side converter is electrically connected to the rotor, the input end of the first converter is electrically connected to the stator, and the output end of the rotor-side converter is electrically connected to the first converter. The output ends of the current transformers are all electrically connected to the low voltage side of the first step-up transformer.

In this way, through the first converter provided on the stator side, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, which can eliminate the need to redesign the generator in the doubly-fed asynchronous wind turbine. , so that the doubly-fed asynchronous wind turbine can be applied to low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

According to any of the foregoing embodiments of the second aspect of the present application, the input end of the rotor-side converter is electrically connected to the rotor, the input end of the first converter is electrically connected to the stator and the output end of the rotor-side converter, respectively, and the first The output end of the converter is electrically connected to the low voltage side of the first step-up transformer.

In this way, through the first converter arranged on the low voltage side of the first step-up transformer, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, which can eliminate the need for the generator in the doubly-fed asynchronous wind turbine generator set. In the case of redesign, the doubly-fed asynchronous wind turbine can be applied to low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

According to any of the foregoing embodiments of the second aspect of the present application, the first converter is electrically connected between the high voltage side of the first step-up transformer and the grid.

In this way, through the first converter arranged on the high voltage side of the first step-up transformer, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, which can eliminate the need for the generator in the doubly-fed asynchronous wind turbine generator set. In the case of redesign, the doubly-fed asynchronous wind turbine can be applied to low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

According to any of the foregoing embodiments of the second aspect of the present application, the target frequency is any frequency in the first frequency range, and the first frequency range includes 8 Hz to 21 Hz.

In this way, in the embodiment of the present application, the frequency of the alternating current output by the generator is adjusted to 8 Hz to 21 Hz through the rotor-side converter and the first converter, so that the wind power generator set outputs low frequency alternating current of 8 Hz to 21 Hz. On the one hand, wind power generation can be improved. The maximum power that the transmission system of the wind turbine can transmit, that is, to improve the transmission capacity of the transmission system of the wind turbine; on the other hand, it can reduce the voltage drop of the transmission line in the transmission system of the wind turbine, which helps to maintain the voltage stability of the transmission system On the other hand, it can reduce the loss of the transmission cable and prolong the life of the transmission cable.

According to any of the preceding embodiments of the second aspect of the present application, the target frequency comprises 50/3 Hz.

In this way, in the embodiment of the present application, the frequency of the alternating current output by the generator is adjusted to 50/3 Hz through the rotor-side converter and the first converter, so that the wind power generator set outputs low-frequency alternating current of 50/3 Hz. On the one hand, the wind power generation can be improved. The maximum power that the transmission system of the wind turbine can transmit, that is, to improve the transmission capacity of the transmission system of the wind turbine; on the other hand, it can reduce the voltage drop of the transmission line in the transmission system of the wind turbine, which helps to maintain the voltage stability of the transmission system On the other hand, it can reduce the loss of the transmission cable and prolong the life of the transmission cable.

According to any of the foregoing embodiments of the second aspect of the present application, the power transmission system further includes a second step-up transformer and a power transmission cable, the low-voltage side of the second step-up transformer is electrically connected to the high-voltage side of the at least one first step-up transformer, and the second step-up transformer is electrically connected to the high-voltage side of the at least one first step-up transformer. The high-voltage side of the step-up transformer is electrically connected to the grid through a power transmission cable.

In this way, before the AC power output by the wind turbine is transmitted over a long distance through the power transmission cable, the voltage value of the AC power output from the high-voltage side of the first step-up transformer is further increased by adding a second step-up transformer to a higher voltage value, Therefore, the loss of electric energy during long-distance transmission is reduced, and the energy utilization rate is improved.

According to any of the foregoing embodiments of the second aspect of the present application, the power transmission system further includes a second converter, the input end of the second converter is electrically connected to the high-voltage side of the second step-up transformer through a power transmission cable, and the second converter The output end of the converter is electrically connected to the grid, and the second converter is configured to adjust the frequency of the alternating current output by the second step-up transformer from the target frequency to 50 Hz.

In this way, in the embodiment of the present application, the frequency of the alternating current output by the generator is adjusted to a low frequency of less than 50 Hz through the rotor-side converter and the first converter, so that the wind power generating set outputs low-frequency alternating current, thereby improving the power transmission system of the wind power generating set. Power transmission capacity, maintain the voltage stability of the power transmission system of the wind turbine, improve the life of the transmission line in the power transmission system of the wind turbine and reduce the cost of power transmission. Then, the second converter adjusts the frequency of the alternating current from a low frequency of less than 50 Hz to 50 Hz, so as to meet the frequency requirements of the alternating current for daily household use.

According to any of the foregoing embodiments of the second aspect of the present application, the power transmission system further includes a first step-down transformer or a third step-up transformer, wherein: the high-voltage side of the first step-down transformer is connected to the high-voltage side of the second step-up transformer through a power transmission cable side is electrically connected, and the low-voltage side of the first step-down transformer is electrically connected to the grid; the low-voltage side of the third step-up transformer is electrically connected to the high-voltage side of the second step-up transformer through a power transmission cable, and the high-voltage side of the third step-up transformer is electrically connected to the power grid. Grid electrical connection.

In this way, by adding the first step-down transformer or the third step-up transformer, the AC power output by the power transmission system of the wind turbine can be converted into the AC power with the desired target voltage value, so as to meet the different needs of people in production or life. electricity demand.

The doubly-fed asynchronous wind generator set and the power transmission system of the wind generator set in the embodiment of the present application, the doubly-fed asynchronous wind generator set includes: a generator; a rotor-side converter, the rotor-side converter is electrically connected to the rotor of the generator, and the In order to adjust the frequency of the alternating current output by the rotor to the target frequency, the target frequency is less than 50Hz; the stator side converter, the stator side converter is electrically connected with the stator of the generator, and is used to adjust the frequency of the alternating current output by the stator to the target frequency . In the embodiment of the present application, by adding a stator-side converter to adjust the frequency of the alternating current output from the stator to a target frequency of less than 50 Hz, it is possible to make The doubly-fed asynchronous wind turbine can be applied to low-frequency or divided-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present application more clearly, the following briefly introduces the accompanying drawings that need to be used in the embodiments of the present application. For those of ordinary skill in the art, without creative work, the Additional drawings can be obtained from these drawings.

Fig. 1 is a schematic diagram of a power transmission scheme based on power frequency high voltage AC transmission;

FIG. 2 is a schematic diagram of a power transmission scheme based on HVDC transmission;

3 is a schematic structural diagram of a doubly-fed asynchronous wind power generator set provided by an embodiment of the present application;

4 is a schematic structural diagram of a power transmission system of a wind turbine according to an embodiment of the application;

5 is another schematic structural diagram of a power transmission system of a wind turbine according to an embodiment of the application;

6 is another schematic structural diagram of a power transmission system of a wind turbine according to an embodiment of the present application;

FIG. 7 is another schematic structural diagram of a power transmission system of a wind turbine according to an embodiment of the present application.

Detailed ways

The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, but not to limit the present application. It will be apparent to those skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present application by illustrating examples of the present application.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element defined by the phrase "comprises" does not preclude the presence of additional identical elements in a process, method, article, or device that includes the element.

It should be understood that the term "and/or" used in this document is only an association relationship to describe the associated objects, indicating that there may be three kinds of relationships, for example, A and/or B, which may indicate that A exists alone, and A and B exist at the same time. B, there are three cases of B alone. In addition, the character "/" in this document generally indicates that the related objects are an "or" relationship.

Before describing the technical solutions provided by the embodiments of the present application, in order to facilitate the understanding of the embodiments of the present application, the present application first specifically describes the problems existing in the prior art:

As mentioned above, the inventors of the present application have found that the related art has problems of high cost of power transmission and retrofit of wind turbines.

In order to solve the problems of high power transmission cost and retrofit cost of wind turbines, the inventor of the present application firstly studies the transmission lines and transmission methods of wind turbines in the related art to determine the root causes of the above technical problems. The research and analysis process is as follows:

Figure 1 shows a power transmission scheme based on power frequency high voltage AC transmission (HVAC for short). As shown in FIG. 1 , taking a power transmission scenario of an offshore wind turbine as an example, the offshore wind farm 10' may include multiple wind turbines 100'. The wind turbine 100' may include an impeller 101', a generator 102' and a converter 103'. Exemplarily, the generator 102 ′ may be a permanent magnet synchronous generator (Permanent Magnetic Synchronous Machine, referred to as PMSG), a double-fed induction generator (Doublyfed induction generator, referred to as DFIG) or other types of generators, the power generation in FIG. 1 . Machine 102' is shown, for example, as a permanent magnet synchronous generator PMSG. Driven by the wind, the impeller 101' starts to rotate and drives the rotor in the generator 102' to rotate relative to the stator in the generator 102', thereby starting to generate electricity. In order to ensure that the wind turbine 100' can output constant electric energy, the converter 103' is usually required to adjust the output electric energy of the generator 102' to electric energy with a constant voltage amplitude and a constant frequency (the frequency is the power frequency of 50 Hz). Since the voltage value output by the converter 103' is low, it is not conducive to the transmission of electric energy. Therefore, in order to efficiently transmit electric energy, it is usually necessary to connect a step-up transformer 200' to the output end of the converter 103', and the voltage output by the converter 103' (that is, the output of the wind turbine 100' is converted into The voltage) is boosted from a lower voltage value to a higher voltage value, such as from 690V (volts) to 35kV (kilovolts), such as an alternating current with a voltage value of 35kV and a frequency of 50Hz, that is, 35kV/50Hz alternating current.

Next, the boosted electric energy (such as 35kV/50Hz alternating current) output by each step-up transformer 200' is aggregated through the collector line 300', and the aggregated electric energy is then passed through the booster transformer 400 in the offshore booster substation. 'Further rise to a higher voltage value (such as 110kV or 220kV), such as to obtain an alternating current with a voltage value of 110kV or 220kV and a frequency of 50Hz, that is, 110kV or 220kV/50Hz alternating current. Next, the 110kV or 220kV/50Hz AC power is transmitted to the onshore substation through the offshore transmission cable 500'. Finally, 110 kV or 220 kV/50 Hz is converted into an alternating current with a target voltage value and a frequency of 50 Hz through the transformer 600' in the land substation and is fed into the grid 700'.

The inventors of the present application have found that with the increase of the transmission distance, the output cost of the HVAC power transmission scheme will also increase. Higher transmission costs than other transmission options.

Figure 2 shows a power transmission scheme based on high-voltage direct current transmission (VSC-HVAC for short). As shown in FIG. 2, different from the HVAC power transmission scheme shown in FIG. 1, the VSC-HVAC power transmission scheme shown in FIG. 2 also includes an offshore converter station 800' and an onshore converter station 900'. It is easy to understand that the offshore converter station 800' is arranged at sea, and the onshore converter station 900' is arranged on land. The role of the offshore converter station 800' is to convert the alternating current (such as 110kV or 220kV/50Hz alternating current) output by the step-up transformer 400' in the offshore step-up substation into direct current. Then, the DC power converted by the offshore converter station 800' is transmitted to the onshore converter station 900' through the offshore power transmission cable 500'. The onshore converter station 900' then converts the direct current to alternating current. That is, compared with the HVAC power transmission scheme shown in FIG. 1 , the VSC-HVAC power transmission scheme shown in FIG. 2 adds a process of converting alternating current to direct current, and then converting direct current to alternating current. Therefore, the VSC-HVAC power transmission scheme needs to configure the offshore converter station 800' and the onshore converter station 900', and the power transmission cost is relatively high.

In order to reduce the power transmission cost of the wind turbine, the embodiment of the present application proposes a low-frequency power transmission scheme or a frequency division power transmission scheme. However, the inventor of the present application also discovered another technical problem in the related art, that is, the stator of the doubly-fed asynchronous generator in the related art is designed according to the AC output of 50Hz, and cannot be applied to the frequency less than 50Hz. Low-frequency or cross-frequency power transmission scenarios. If you want the stator of the DFIG to be suitable for low-frequency or divided-frequency power transmission scenarios with a frequency less than 50 Hz, the DFIG needs to be redesigned, especially the stator of the DFIG needs to be redesigned. As the core component of the wind turbine, the redesign of the generator means that the wind turbine needs to be redesigned. In this way, the retrofit cost or design cost of the wind turbine will be relatively high.

In view of the above research findings of the inventors, the embodiments of the present application provide a doubly-fed asynchronous wind power generator set, which can solve the technical problem of the high cost of retrofitting of wind power generator sets in the related art.

The technical idea of the embodiments of the present application is to adjust the frequency of the alternating current output from the stator from 50 Hz to less than 50 Hz by adding a stator-side converter, so that there is no need to redesign the generator in the doubly-fed asynchronous wind turbine. Under the circumstance, the DFIG asynchronous wind turbine can be applied to the low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the DFIG.

First, the doubly-fed asynchronous wind power generator set provided by the embodiment of the present application will be introduced below.

As shown in FIG. 3 , an embodiment of the present application provides a doubly-fed asynchronous wind generator set 300 . The so-called "double-fed" means that both the stator and the rotor of the generator can exchange power with the grid. The stator or stator winding of the doubly-fed asynchronous generator can be directly connected to the grid, and the rotor or rotor winding can be connected to the grid through a converter. The frequency, voltage, amplitude and phase of the rotor winding power supply can be automatically adjusted by the converter according to the operating requirements, so that the doubly-fed asynchronous wind turbine can achieve constant frequency power generation at different speeds, thereby satisfying the power load and grid connection. requirements. The doubly-fed asynchronous wind power generator set 300 provided in the embodiment of the present application includes: a generator 301 , a rotor-side converter 302 and a stator-side converter 303 . The rotor-side converter 302 is electrically connected to the rotor of the generator 301, and is used to adjust the frequency of the AC power output by the rotor to a target frequency. The stator-side converter 303 is electrically connected to the stator of the generator 301, and is used to adjust the frequency of the alternating current output from the stator to a target frequency. Among them, the target frequency is less than 50Hz.

It is easy to understand that the rotor-side converter can be understood as a converter provided on the rotor side and electrically connected to the rotor of the generator 301 , and the stator-side converter can be understood as a converter provided on the stator side and connected to the generator 301 . The stator is electrically connected to the converter. In practical applications, the converter can also be called a frequency converter or other names, such as the English name FrequencyConverter, that is, if the rotor-side converter and the stator-side converter are replaced with other electronic devices that can realize the frequency conversion function, they are also in the within the scope of protection of this application. In the embodiment of the present application, the rotor-side converter 302 and the stator-side converter 303 include, but are not limited to, an AC-AC converter, that is, an AC-AC converter.

The working process of the doubly-fed asynchronous wind power generating set 300 according to the embodiment of the present application will be briefly introduced below.

Continuing to refer to FIG. 3 , according to some embodiments of the present application, the doubly-fed asynchronous wind turbine generator 300 may further include an impeller 304 and a gearbox 305 . The impeller 304 drives the gears in the gear box 305 to rotate to realize the conversion of wind energy to mechanical energy. The gearbox 305 drives the generator 301 to generate electricity to realize the conversion of mechanical energy to electrical energy. The rotor-side converter 302 adjusts the frequency of the alternating current output by the rotor of the generator 301 to be less than the target frequency of 50 Hz, and the stator-side converter 303 adjusts the frequency of the alternating current output from the stator of the generator 301 to be less than the target frequency of 50 Hz. The step-up transformer 200 boosts the voltage of the alternating current output by the rotor-side converter 302 and the stator-side converter 303 from a lower voltage value to a higher voltage value, for example, from 690V to 35kV, and the obtained voltage value is 35kV and The alternating current with a frequency of less than 50 Hz is then transmitted to the grid 500 with an alternating current with a voltage value of 35 kV and a frequency of less than 50 Hz.

The doubly-fed asynchronous wind power generator set provided by the embodiment of the present application can achieve the following technical effects: because the stator of the current doubly-fed asynchronous generator is designed according to the AC output of 50Hz, it cannot be applied to the low-frequency or divided-frequency power transmission scenarios with a frequency less than 50Hz. . However, in the embodiment of the present application, the frequency of the alternating current output from the stator is adjusted from 50 Hz to less than 50 Hz by adding a stator-side converter, so that the generator in the doubly-fed asynchronous wind turbine does not need to be redesigned. The doubly-fed asynchronous wind turbine can be applied to low-frequency or divided-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

Aiming at the problems of high power transmission cost and modification cost of the wind power generating set, the embodiment of the present application also provides a power transmission system for the wind power generating set.

As shown in FIG. 4 , the power transmission system 400 of the wind turbine generator set provided in the embodiment of the present application includes: a doubly-fed asynchronous wind turbine generator set 410 , a first converter 420 and a first step-up transformer 430 . The DFIG 410 includes a generator 411 and a rotor-side converter 412. The rotor-side converter 412 is electrically connected to the rotor of the generator 411 for adjusting the frequency of the alternating current output by the rotor of the generator 411 to a target frequency, the target frequency is less than 50Hz. The first converter 420 is electrically connected between the stator of the generator 411 and the grid 500, and is used for adjusting the frequency of the alternating current output by the stator of the generator 411 to a target frequency less than 50 Hz. The low-voltage side of the first step-up transformer 430 is electrically connected to the stator of the generator 411 and the rotor-side converter 412 respectively, the high-voltage side of the first step-up transformer 430 is electrically connected to the power grid 500, and the first step-up transformer 430 is used for converting The voltage of the alternating current output by the rotor-side converter 302 and the stator of the generator 411 or the first converter 420 is boosted from a lower voltage value to a higher voltage value, for example, from 690V to 35kV. The AC power with a higher voltage value and a frequency less than 50 Hz after being boosted by the first step-up transformer 430 is transmitted to the power grid 500 .

In the power transmission system 400 of the wind turbine generator set provided by the embodiment of the present application, a first converter is added to adjust the frequency of the alternating current output from the stator from 50Hz to less than 50Hz, so that the generator in the doubly-fed asynchronous wind turbine generator does not need to be rebuilt. In the case of design, the doubly-fed asynchronous wind turbine can be applied to low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

In addition, the power transmission system 400 of the wind turbine provided by the embodiment of the present application adjusts the frequency of the AC power output by the generator to be less than 50 Hz through the rotor-side converter and the first converter, which can improve the power transmission of the wind turbine on the one hand. The maximum power that the system can transmit, that is, to improve the transmission capacity of the transmission system of the wind turbine; on the other hand, it can reduce the voltage drop of the transmission line in the transmission system of the wind turbine, which helps to maintain the voltage stability of the transmission system; On the one hand, it can reduce the loss of the transmission cable and prolong the life of the transmission cable.

Continuing to refer to FIG. 4 , according to some embodiments of the present application, optionally, the first converter 420 may be electrically connected between the stator of the generator 411 and the low voltage side of the first step-up transformer 130 . That is, the first converter 420 adjusts the frequency of the alternating current output from the stator of the generator 411 to a target frequency of less than 50 Hz, and then the first step-up transformer 430 boosts the alternating current output from the first converter 420 to obtain a higher frequency. Alternating current with high voltage value (eg 35kV) and frequency less than 50Hz. In the embodiment of the present application, the rotor-side converter 302 and the first converter 420 include, but are not limited to, an AC-AC converter, that is, an AC-AC converter.

In this way, through the first converter between the stator of the generator and the low-voltage side of the first step-up transformer, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, and it is possible to generate electricity without the need for double-fed asynchronous wind power generation. In the case of redesigning the generators in the unit, the DFIG asynchronous wind turbine can be applied to the low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the DFIG.

Continuing to refer to FIG. 4 , in some specific embodiments, optionally, the first converter 420 may be provided on the stator side. Specifically, the input end of the rotor-side converter 412 is electrically connected to the rotor of the generator 411, the input end of the first converter 420 is electrically connected to the stator of the generator 411, and the output end of the rotor-side converter 412 is electrically connected to the stator of the generator 411. The output ends of a converter 420 are all electrically connected to the low voltage side of the first step-up transformer 430 . The rotor-side converter 412 adjusts the frequency of the alternating current output from the rotor of the generator 411 to a target frequency, and the first converter 420 adjusts the frequency of the alternating current output from the stator of the generator 411 to a target frequency less than 50 Hz. The first step-up transformer 430 boosts the AC power output by the rotor-side converter 412 and the first converter 420 to obtain AC power with a higher voltage value (eg, 35kV) and a frequency less than 50Hz.

In this way, through the first converter provided on the stator side, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, which can eliminate the need to redesign the generator in the doubly-fed asynchronous wind turbine. , so that the doubly-fed asynchronous wind turbine can be applied to low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

As shown in FIG. 5 , in other specific embodiments, optionally, the first converter 420 may also be disposed on the low-voltage side of the first step-up transformer 430 . Specifically, the input end of the rotor-side converter 412 is electrically connected to the rotor of the generator 411, the input end of the first converter 420 is electrically connected to the stator of the generator 411 and the output end of the rotor-side converter 412, respectively, The output end of the first converter 420 is electrically connected to the low voltage side of the first step-up transformer 430 . The rotor-side converter 412 adjusts the frequency of the alternating current output from the rotor of the generator 411 to a target frequency, and the first converter 420 adjusts the frequency of the alternating current output from the stator of the generator 411 to a target frequency less than 50 Hz. The first step-up transformer 430 boosts the AC power output by the rotor-side converter 412 and the first converter 420 to obtain AC power with a higher voltage value (eg, 35kV) and a frequency less than 50Hz.

In this way, through the first transformer arranged on the low voltage side of the first step-up transformer, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, and the generators in the doubly-fed asynchronous wind turbines can be re-engineered without having to be rebuilt. In the case of design, the doubly-fed asynchronous wind turbine can be applied to low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

As shown in FIG. 6 , in some other specific embodiments, optionally, the first converter 420 may also be disposed on the high voltage side of the first step-up transformer 430 . Specifically, the first converter 420 is electrically connected between the high voltage side of the first step-up transformer 430 and the power grid 500 . The first converter 420 can also adjust the frequency of the alternating current output by the stator of the generator 411 to a target frequency of less than 50 Hz.

In this way, by means of the first transformer arranged on the high voltage side of the first step-up transformer, the frequency of the alternating current output from the stator can be adjusted to a target frequency of less than 50 Hz, and the generators in the doubly-fed asynchronous wind power generating set need not be reworked. In the case of design, the doubly-fed asynchronous wind turbine can be applied to low-frequency or sub-frequency transmission scenarios with a frequency less than 50Hz, thereby reducing the retrofit cost or design cost of the doubly-fed asynchronous wind turbine.

According to some embodiments of the present application, optionally, the target frequency may be any frequency in a first frequency range, and the first frequency range includes 8 Hz to 21 Hz. Illustratively, for example, the target frequency may be 50/6 Hz, 15 Hz, 50/3 Hz, 21 Hz, or the like.

In this way, in the embodiment of the present application, the frequency of the alternating current output by the generator is adjusted to 8 Hz to 21 Hz through the rotor-side converter and the first converter, so that the wind power generator set outputs low frequency alternating current of 8 Hz to 21 Hz. On the one hand, wind power generation can be improved. The maximum power that the transmission system of the wind turbine can transmit, that is, to improve the transmission capacity of the transmission system of the wind turbine; on the other hand, it can reduce the voltage drop of the transmission line in the transmission system of the wind turbine, which helps to maintain the voltage stability of the transmission system On the other hand, it can reduce the loss of the transmission cable and prolong the life of the transmission cable.

In some specific embodiments, the target frequency may optionally include 50/3 Hz.

In this way, in the embodiment of the present application, the frequency of the alternating current output by the generator is adjusted to 50/3 Hz through the rotor-side converter and the first converter, so that the wind power generator set outputs low-frequency alternating current of 50/3 Hz. On the one hand, the wind power generation can be improved. The maximum power that the transmission system of the wind turbine can transmit, that is, to improve the transmission capacity of the transmission system of the wind turbine; on the other hand, it can reduce the voltage drop of the transmission line in the transmission system of the wind turbine, which helps to maintain the voltage stability of the transmission system On the other hand, it can reduce the loss of the transmission cable and prolong the life of the transmission cable.

As shown in FIG. 7 , according to some embodiments of the present application, optionally, the power transmission system 400 of the wind turbine may further include a second step-up transformer 710 and a power transmission cable 720 , and the low-voltage side of the second step-up transformer 710 is connected to the The high-voltage side of at least one first step-up transformer 430 is electrically connected, and the high-voltage side of the second step-up transformer 710 is electrically connected to the grid 500 through a power transmission cable 720 . The second step-up transformer 710 can be used to step up the alternating current with a higher voltage value (eg, 35kV) and a frequency less than 50Hz output by the at least one first step-up transformer 430 , eg, to obtain a higher voltage value (eg, 110kV or 220kV) And the frequency is less than 50Hz alternating current. The power transmission cable 720 transmits the alternating current with a higher voltage value (eg, 110 kV or 220 kV) output by the second step-up transformer 710 and a frequency less than 50 Hz to the power grid 500 . It should be noted that, in a power transmission scenario of an offshore wind turbine, the second step-up transformer 710 may be disposed in an offshore step-up substation, and the power transmission cable 720 may be an offshore power transmission cable.

In this way, before the AC power output by the wind turbine is transmitted over a long distance through the power transmission cable, the voltage value of the AC power output from the high-voltage side of the first step-up transformer is further increased by adding a second step-up transformer to a higher voltage value, Therefore, the loss of electric energy during long-distance transmission is reduced, and the energy utilization rate is improved.

Continuing to refer to FIG. 7 , according to some embodiments of the present application, optionally, the power transmission system 400 of the wind turbine may further include a second converter 730 , and the input end of the second converter 730 is connected to the second converter 730 through the power transmission cable 720 . The high voltage sides of the two step-up transformers 710 are electrically connected, the output end of the second converter 730 is electrically connected to the grid 500, and the second converter 730 is configured to change the frequency of the alternating current output from the second step-up transformer 710 to the target frequency Adjust to 50Hz. For example, the second step-up transformer 710 outputs an alternating current of 110kV or 220kV and a frequency less than 50Hz, and the second converter 730 can convert the alternating current of 110kV or 220kV and a frequency of less than 50Hz to an alternating current of 110kV or 220kV and a frequency equal to 50Hz . In this embodiment of the present application, the second converter 730 includes, but is not limited to, an AC-AC converter, that is, an AC-AC converter.

In this way, in the embodiment of the present application, the frequency of the alternating current output by the generator is adjusted to a low frequency of less than 50 Hz through the rotor-side converter and the first converter, so that the wind power generating set outputs low-frequency alternating current, thereby improving the power transmission system of the wind power generating set. Power transmission capacity, maintain the voltage stability of the power transmission system of the wind turbine, improve the life of the transmission line in the power transmission system of the wind turbine and reduce the cost of power transmission. Then, the second converter adjusts the frequency of the alternating current from a low frequency of less than 50 Hz to 50 Hz, so as to meet the frequency requirements of the alternating current for daily household use.

It should be noted that, in the power transmission scenario of the offshore wind turbine, the second converter 730 can be arranged on land, thereby reducing the installation cost of the second converter and improving the installation efficiency of the second converter.

According to some embodiments of the present application, optionally, the power transmission system 400 of the wind turbine may further include a first step-down transformer 740 or a third step-up transformer 750, wherein: the high-voltage side of the first step-down transformer 740 passes through a power transmission line The cable 720 is electrically connected to the high voltage side of the second step-up transformer 710 , and the low voltage side of the first step-down transformer 740 is electrically connected to the grid 500 . The low voltage side of the third step-up transformer 750 is electrically connected to the high-voltage side of the second step-up transformer 710 through the power transmission cable 720 , and the high-voltage side of the third step-up transformer 750 is electrically connected to the grid 500 . It should be noted that, in the power transmission scenario of the offshore wind turbine, the first step-down transformer 740 or the third step-up transformer 750 may be arranged on land.

It is easy to understand that when the AC power transmitted by the power transmission cable 720 needs to be stepped down (for example, the AC power transported by the power transmission cable 720 is converted into electricity for daily life), the first step-down transformer 740 can be provided to pass the first step-down transformer 740. The step-down transformer 740 steps down the AC power transmitted by the power transmission cable 720, so that the AC power output by the power transmission system 400 of the wind turbine is converted into AC power with a desired target voltage value. When the AC power transmitted by the power transmission cable 720 needs to be boosted (for example, the AC power transported by the power transmission cable 720 needs to be transmitted over a long distance again), a third step-up transformer 750 can be provided, and the third step-up transformer 750 can be used for power transmission. The AC power transmitted by the cable 720 is boosted, so that the AC power output by the power transmission system 400 of the wind turbine is converted into AC power with a desired target voltage value.

In this way, by adding the first step-down transformer or the third step-up transformer, the AC power output by the power transmission system of the wind turbine can be converted into the AC power with the desired target voltage value, so as to meet the different needs of people in production or life. electricity demand.

It should be noted that, the first step-up transformer 430, the second step-up transformer 710, the third step-up transformer 750 and the first step-down transformer 740 may adopt a star-delta design, a star-star design or other types of designs. The embodiment is not limited.

It should be clear that each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment may be referred to each other, and each embodiment focuses on the differences from other embodiments. place. For the power transmission system embodiment, reference can be made to the description section of the wind turbine embodiment. The present application is not limited to the specific structures described above and shown in the drawings. Various changes, modifications and additions can be made by those skilled in the art after comprehending the spirit of the present application. Also, for the sake of brevity, detailed descriptions of known technologies are omitted here.

Those skilled in the art should understand that the above-mentioned embodiments are all illustrative and not restrictive. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Those skilled in the art should be able to understand and implement other variant embodiments of the disclosed embodiments on the basis of studying the drawings, the description and the claims. In the claims, the term "comprising" does not exclude other means or steps; the term "a" does not exclude a plurality; the terms "first" and "second" are used to denote names rather than any particular order . Any reference signs in the claims shall not be construed as limiting the scope. The functions of several parts presented in the claims can be implemented by a single hardware or software module. The mere presence of certain technical features in different dependent claims does not imply that these features cannot be combined to advantage.

Claims (8)

1. a doubly-fed asynchronous wind power generating set, is characterized in that, comprises: dynamo; a rotor-side converter, the rotor-side converter is electrically connected to the rotor of the generator, and is used for adjusting the frequency of the alternating current output by the rotor to a target frequency, where the target frequency is less than 50 Hz; A stator-side converter, which is electrically connected to the stator of the generator, and used to adjust the frequency of the alternating current output by the stator to the target frequency. 2. A power transmission system for wind turbines, comprising: The doubly-fed asynchronous wind power generator set includes a generator and a rotor-side converter, and the rotor-side converter is electrically connected to the rotor of the generator, and is used to convert the output power of the rotor. The frequency of the alternating current is adjusted to the target frequency, and the target frequency is less than 50Hz; a first step-up transformer, the low-voltage side of the first step-up transformer is electrically connected to the stator of the generator and the rotor-side converter, respectively, and the high-voltage side of the first step-up transformer is electrically connected to the grid; a first converter, which is electrically connected between the stator and the power grid, and is used for adjusting the frequency of the alternating current output by the stator to a target frequency. 3. The power transmission system of claim 2, wherein the first converter is electrically connected between the stator and the low voltage side of the first step-up transformer. 4. The power transmission system according to claim 3, wherein the input end of the rotor-side converter is electrically connected to the rotor, and the input end of the first converter is electrically connected to the stator, Both the output end of the rotor-side converter and the output end of the first converter are electrically connected to the low voltage side of the first step-up transformer; or, The input end of the rotor-side converter is electrically connected to the rotor, the input end of the first converter is electrically connected to the stator and the output end of the rotor-side converter respectively, and the first converter is electrically connected to the output end of the stator and the rotor-side converter. The output end of the converter is electrically connected to the low voltage side of the first step-up transformer. 5. The power transmission system according to claim 2, wherein the first converter is electrically connected between the high voltage side of the first step-up transformer and the power grid; The target frequency is any frequency in a first frequency range, and the first frequency range includes 8 Hz to 21 Hz. 6. The power transmission system according to any one of claims 2-5, wherein the power transmission system further comprises a second step-up transformer and a power transmission cable, and the low-voltage side of the second step-up transformer is connected to at least a The high-voltage side of one of the first step-up transformers is electrically connected, and the high-voltage side of the second step-up transformer is electrically connected to the power grid through the power transmission cable. 7 . The power transmission system according to claim 6 , wherein the power transmission system further comprises a second converter, and an input end of the second converter is connected to the second converter through the power transmission cable. 8 . The high-voltage side of the step-up transformer is electrically connected to the high-voltage side, the output end of the second transformer is electrically connected to the grid, and the second transformer is configured to convert the frequency of the alternating current output from the second step-up transformer by the Adjust the target frequency to 50Hz. 8. The power transmission system according to claim 6, wherein the power transmission system further comprises a first step-down transformer or a third step-up transformer, wherein: The high-voltage side of the first step-down transformer is electrically connected to the high-voltage side of the second step-up transformer through the power transmission cable, and the low-voltage side of the first step-down transformer is electrically connected to the power grid; The low voltage side of the third step-up transformer is electrically connected to the high-voltage side of the second step-up transformer through the power transmission cable, and the high-voltage side of the third step-up transformer is electrically connected to the power grid.

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